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  • 451.
    Sundberg, Jill
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Nyberg, Harald
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Särhammar, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Gustavsson, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Nyberg, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Kubart, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Influence of Ti addition on the structure and properties of low-friction W–S–C coatings2013In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 232, p. 340-348Article in journal (Refereed)
    Abstract [en]

    Transition metal dichalcogenides, such as WS2 and MoS2, are known for their layered structure and lubricating properties. When deposited as thin coatings, however, their use as solid lubricants is limited by their low hardness and load-bearing capacity. The addition of another element, such as carbon, can improve the mechanical properties, although the hardness of for example W-S-C coatings is still rather low. In this work, Ti has been added to W-S-C coatings in order to further increase the hardness by carbide formation. W-S-C and W-S-C-Ti coatings were deposited by non-reactive magnetron sputtering, and characterized with regard to composition, structure and mechanical and tribological properties. It was found that the addition of Ti leads to the formation of a new carbide phase, and a significant increase in hardness for coatings with moderate carbon contents. The friction properties of W-S-C-Ti coatings were found to be comparable to that of W-S-C coatings, with friction coefficients down to mu approximate to 0.02 and similar wear rates against steel in a dry atmosphere. Formation of WS2 in the wear track of W-S-C-Ti was confirmed by transmission electron microscopy. It has thus been shown that the addition of Ti to W-S-C coatings can increase the hardness, while still maintaining WS2 lubrication.

  • 452.
    Sundberg, Jill
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Nyberg, Harald
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Särhammar, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Kádas, Krisztina
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Hungarian Acad Sci, Inst Solid State Phys & Opt, Wigner Res Ctr, H-1525 Budapest, Hungary.
    Wang, Liping
    Chinese Acad Sci, Lanzhou Inst Chem Phys, State Key Lab Solid Lubricat, Lanzhou, Peoples R China.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Nyberg, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Tribochemically Active Ti–C–S Nanocomposite Coatings2013In: Materials Research Letters, ISSN 2166-3831, Vol. 1, no 3, p. 148-155Article in journal (Refereed)
    Abstract [en]

    We demonstrate a new concept of self-adaptive materials, where sulphur is incorporated into TiC/a-C coatings and may be released in, for example, a tribological contact. By reactive sputtering with H2S, sulphur goes into the carbide to form a TiC x S y phase in an amorphous carbon matrix. The addition of sulphur lowers the friction against steel. Significantly lower friction is obtained against a tungsten counter-surface, as WS2 is generated in the contact. Annealing experiments and formation energy calculations confirm that sulphur can be released from TiC x S y . Ti–C–S coatings are thus chemically active in tribological contacts, creating possibilities of new low-friction systems.

  • 453.
    Sundberg, Jill
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Nyberg, Harald
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Särhammar, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Kádas, Krisztina
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Wang, Liping
    Lanzhou Institute of Chemical Physics.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Nyberg, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Tribochemically active Ti-C-S nanocomposites – a new concept for self-lubricating coatings2013Conference paper (Other academic)
  • 454.
    Sundberg, Jill
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Nyberg, Harald
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Särhammar, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Nyberg, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Influence of composition, structure and testing atmosphere on the tribological performance of W-S-N coatings2014In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 258, p. 86-94Article in journal (Refereed)
    Abstract [en]

    W-S-N coatings deposited by reactive magnetron sputtering offer the possibility of ultra-low friction in unlubricated sliding. In this work, W-S-N coatings of different composition and structure have been deposited, characterised and evaluated with respect to the tribological performance and tribofilm formation. The composition was varied by changing the flow of N-2 into the deposition chamber, leading to N contents ranging from 0 to 47 at.%. W-S-N coatings deposited without substrate heating are amorphous, while substrate heating results in coatings containing nanocystalline tungsten sulphide (WSx) for low N contents, and nanocrystalline tungsten nitride (WyN) at a high N content. The coatings were tribologically tested against steel balls in four different atmospheres dry N-2, dry air, humid N-2 and humid air to study the effects of atmospheric O-2 and H2O both separately and simultaneously. In dry N-2, all coatings exhibited an excellent performance with very low friction (mu approximate to 0.02) and wear. Notably, this included the N-richest and hardest coating, containing nanocrystalline WyN and only 13 at.% of S. The friction and wear increased on changing the atmosphere, in the order of dry air-humid N-2-humid air. In these three non-inert atmospheres, the friction and wear also increased with increasing N content of the coating. It is thus concluded that the presence of O-2, the presence of H2O, and a high N content (i.e., low Wand S contents) are three factors increasing the risk of high friction and wear, especially when occurring together. Raman spectroscopy mapping of the contact surfaces on the coatings and the balls showed that low friction and wear is connected to the presence of WS2 tribofilms in the contact, and that the three previously mentioned factors affect the formation and function of this tribofilm.

  • 455.
    Sundberg, Jill
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Nyberg, Harald
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Särhammar, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Nyberg, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Sulfur-doping of nc-TiC/a-C films by reactive sputtering2012In: Thirteenth International Conference on Plasma Surface Engineering, Garmisch-Partenkirchen, Germany, 10-14 September 2012, 2012Conference paper (Refereed)
    Abstract [en]

    Nanocomposite thin films with carbide grains in a matrix of amorphous carbon have been found interesting for various mechanical and electrical applications. An important advantage of these materials is the possibility to tune the properties by varying the composition and the microstructure. A well-known example is the nc-TiC/a-C system, which is interesting for its tribological as well as its electrical and chemically protective properties. One way to modify the material is doping with a third element. Usually, another metal or a p-element such as oxygen or nitrogen is considered. In this work, however, Ti-C films have been doped with sulfur. The doping was performed by introduction of increasing amounts of H2S to the chamber during DC magnetron sputtering from elemental Ti and C targets.

    An increased flow of H2S during deposition leads to an increase in the S content of the films, as well as a slight decrease in the C:Ti ratio. Pure TiC/a-C films were proved by GI-XRD and XPS to contain crystalline TiC with the NaCl structure in a matrix of amorphous carbon. The introduction of S leads to a significant and gradual increase of the cell parameter of the carbide phase – from 4.3 Å up to more than 4.8 Å for coatings with approximately 20 at-% of S. This clearly indicates that the S atoms enter the carbide phase, forming a previously unknown Ti-C-S solid solution. The addition of S also affects the mechanical properties, such as the hardness which was seen to decrease from 8 GPa for pure TiC in an amorphous carbon matrix, to 5 GPa when doped with sulfur.

    Thus, the introduction of S is shown to have effects on the chemistry as well as the properties of nc-TiC/a-C thin films. In the current work, the effect of S doping on the structure, chemical bonding and mechanical properties as well as tribological performance will be presented.

  • 456.
    Sundberg, Jill
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Nyberg, Harald
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Särhammar, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Nyberg, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Tribochemically active Ti-C-S coatings2013Conference paper (Other academic)
  • 457.
    Sundberg, Jill
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Särhammar, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Nyberg, Harald
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Kubart, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Nyberg, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Quaternary W-S-C-Ti films for tribological applications2011Conference paper (Refereed)
    Abstract [en]

    Introduction

    Transition metal dichalcogenides such as WS2 are well-known for their layered structure and solid lubricant properties. The addition of another element, such as carbon, can improve the mechanical properties of the material, such as the hardness, while still maintaining the solid lubrication.1,2 Different theories regarding the friction mechanisms in W-S-C have been proposed: the low friction could be solely due to the WS2 phase2 or both the WS2 and the carbon phase could be responsible.1 Despite the hardness increase compared to pure WS2, W-S-C films still exhibit a quite low hardness. One route to increasing the hardness is to add a fourth element, which is a strong carbide-former (e. g. titanium), to form a hard carbide phase. In this work, W-S-C-Ti films have been deposited by magnetron sputtering and characterized with a variety of techniques. The mechanical and tribological properties have been studied and related to the composition.

    Experimental Procedures

    The films were deposited by non-reactive DC magnetron sputtering using two targets: graphitic carbon and WS2, with a ring-shaped titanium component mounted on the latter. The titanium content was varied by the size of the metal component, while the carbon content was varied by the carbon target power. Four series of films were deposited at room temperature and at 300°C.

    The micro- and nanostructure of the films was investigated by SEM and TEM, and XRD was used to study the presence of crystalline phases. The composition was determined by EDS, and the chemical bonding was studied by XPS and Raman spectroscopy. Nanoindentation was used to probe the mechanical properties of the different films, and ball-on-disc tests were performed in order to evaluate the tribological properties.

    Results and Discussion

    Previous studies on W-S-C suggest that the material consists of WS2 nanocrystallites embedded in an amorphous matrix. Also in this study, the only phase detected with XRD is WS2, with the typical WS2 peaks becoming broader with the addition of carbon indicating a decrease in crystallinity. TEM shows WS2 nanocrystallites embedded in an amorphous matrix. However, our results indicate that the composition of the matrix is more complex than what has previously been suggested. Chemical information from XPS suggests that the matrix is not based on carbon alone, but that it also includes a carbidic component. Furthermore, the S/W ratio in the samples is approximately constant but significantly lower than 2; such substochiometry in WS2 films is well known and we will discuss possible mechanisms for this behaviour.

    By adding titanium to W-S-C, the chemical bonding in the material is changed. XPS indicates the presence of Ti-C bonds even when no crystalline TiC grains are observed by XRD. For high titanium and carbon contents, a crystalline phase with the sodium chloride structure is observed, which has a cell parameter significantly larger than TiC. Furthermore, the added titanium changes the mechanical properties of the films, and an increase in hardness up to 100% from 6 GPa to 12 GPa can be observed. The effect of titanium addition, however, is dependent on the film composition and the deposition temperature.

    Tribological testing show friction coefficients down to approximately 0.02 in ball-on-disc tests using a steel ball in dry atmosphere for W-S-C films. The effect of titanium addition varies with the composition; high titanium contents combined with suitable carbon levels yields films that exhibit low and stable friction coefficients well under 0.02 under the aforementioned conditions. Thus, it is possible to tune the mechanical properties of W-S-C films, while still obtaining low friction, by the addition of titanium.

    References

    [1] A.A. Voevodin, J.S. Zabinski, Thin Solid Films 370, 223-231 (2000)

    [2] T. Polcar, M. Evaristo, A. Cavaleiro, Plasma Process. Polym. 6, 417-424 (2009)

  • 458.
    Sundman, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Utveckling av processparametrar inom en hårdmetallindustri2012Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This report analyzes and examines a hypothesis for finding a method to optimize thelength of the delubrication process time based on a total charge weight. The work hasfocused on the holding time for delubrication and the total charge weight.An important step in the manufacturing chain of cutting tools is when the greenbodies undergo the sintering process. Today, the delubrication step has the sameprocess time independent of the total charge weight. An implementation of a methodto adjust the delubrication process time would give more consistent quality of thecutting tool´s internal characteristics but also reduce the time course of the sinteringprocess. In the present project two methods for this goal were tested, thedevelopment of an algorithm and a weight interval subdivision with associateddelubrication process times.During delubrication a pressure increase is observed due to the decomposition of thePEG in the powder mixture. Previously, a larger total charge weight both increasedthe magnitude of the pressure increase and prolonged the time this increase took toreturn to the background pressure level. Earlier analysis of historical process datashowed indications of the possibility of developing an algorithm between total chargeweight and the time period defined by the time remaining for the delubricating stageafter the pressure increase has returned to its base level. This algorithm could thenbe implemented in production and lead to a charge weight adjusted delubricationprocess time, i.e. larger charge weights will need a longer delubricating period.A second method, involving a weight interval subdivision with specific associateddelubrication process times, was developed and a test was performed to determinewhether these ranges affected the quality of the sintering process.The results from the tests and the analysis of historical process data led to theconclusion that the hypothesis of dependence between the delubrication process timeand the total charge weight was not justified for the process investigated. Throughregression analysis it was found that the delubrication process did not dependsignificantly on the charge weight.The work resulted in a modification so that the delubrication process time couldtheoretically be shortened by approximately 60 minutes for the investigated processindependent of the total charge weight. Further analysis and tests are needed to findthe most optimal time reduction of the delubrication process without negativelyaffecting the internal properties of the inserts.

  • 459.
    Svanström, Sebastian
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Jacobsson, Jesper
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Sloboda, Tamara
    KTH Royal Inst Technol, Dept Chem, Div Appl Phys Chem, Stockholm, Sweden.
    Giangrisostomi, Erika
    Helmholtz Zentrum Berlin GmbH, Inst Methods & Instrumentat Synchrotron Radiat Re, Berlin, Germany.
    Ovsyannikov, Ruslan
    Helmholtz Zentrum Berlin GmbH, Inst Methods & Instrumentat Synchrotron Radiat Re, Berlin, Germany.
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Cappel, Ute
    KTH Royal Inst Technol, Dept Chem, Div Appl Phys Chem, Stockholm, Swede.
    Effect of halide ratio and Cs+ addition on the photochemical stability of lead halide perovskites2018In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 6, no 44, p. 22134-22144Article in journal (Refereed)
    Abstract [en]

    Lead halide perovskite solar cells with multi-cation/mixed halide materials now give power conversion efficiencies of more than 20%. The stability of these mixed materials has been significantly improved through the addition of Cs+ compared to the original methylammonium lead iodide. However, it remains one of the most significant challenges for commercialisation. In this study, we use photoelectron spectroscopy (PES) in combination with visible laser illumination to study the photo-stability of perovskite films with different compositions. These include Br : I ratios of 50 : 50 and 17 : 83 and compositions with and without Cs+. For the samples without Cs and the 50 : 50 samples, we found that the surface was enriched in Br and depleted in I during illumination and that some of the perovskite decomposed into Pb0, organic halide salts, and iodine. After illumination, both of these reactions were partially reversible. Furthermore, the surfaces of the films were enriched in organic halide salts indicating that the cations were not degraded into volatile products. With the addition of Cs+ to the samples, photo-induced changes were significantly suppressed for a 50 : 50 bromide to iodide ratio and completely suppressed for perovskites with a 17 : 83 ratio at light intensities exceeding 1 sun equivalent.

  • 460.
    SVEDLINDH, P
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    NISKANEN, K
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    NORLING, P
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    NORDBLAD, P
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    LUNDGREN, L
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    LONNBERG, B
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    LUNDSTROM, T
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    ANTI-MEISSNER EFFECT IN THE BISRCACUO-SYSTEM1989In: Physica. C, Superconductivity, ISSN 0921-4534, E-ISSN 1873-2143, Vol. 162, p. 1365-1366Article in journal (Refereed)
  • 461.
    Särhammar, Erik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Strandberg, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Sundberg, Jill
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Nyberg, Harald
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Kubart, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Nyberg, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Mechanisms for compositional variations of coatings sputtered from a WS2 target2014In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 252, p. 186-190Article in journal (Refereed)
    Abstract [en]

    Magnetron sputtering fromcompound targets is widely used for the deposition of compound films since it is easyto scale up and it exhibits a high reproducibility. Controlling film stoichiometry is crucial for obtaining filmswithdesired properties. However, the process is rather complex and sputtering from a compound target frequentlyresults in film compositions that deviate significantly from that of the target. This is due to a number of effectsrelated to the nature of the sputtering process which include preferential re-sputtering due to energetic particlebombardment at the substrate, different take-off angles, scattering in the gas phase, and different stickingcoefficients.

    In this work, we have investigated how sputtering from aWS2 target results in different film compositions as afunction of the position in the chamber, for different processing conditions. Hence, the films have not been characterizedwith respect to structural or morphological properties. A Monte-Carlo based software, accounting fordifferent take-off angles and scattering in the gas phase, was developed to simulate the compositional variationsat various positions in the chamber. Further, a number of experimentswere performed by varying the target voltage,process pressure, as well as the location of the substrate (on and off axis). Simulations and experiments revealsignificant compositional variations for different processing conditions. Experiments show that thesevariations are only slightly affected by the target voltage, while the most significant variations result from theprocessing pressure and position on the chamber. From the qualitatively good agreement between experimentsand simulations it is clear that gas phase scattering must be taken into account to explain the observed compositionaltrends, while the other effects are less important and sticking coefficients effectsmay even be negligible.It is therefore concluded that themajor effect responsible for the compositional variation of the film is the differentscattering behaviour of S andWin the gas phase.

  • 462.
    Särhammar, Erik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Sundberg, Jill
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Nyberg, Harald
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Kubart, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Nyberg, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Mechanisms responsible for compositional variations of films sputtered from a WS2 target2012In: International Conference on Metallurgical Coatings and Thin films (ICMCTF) 23-27/04 2012, San Diego, abstract number:428, 2012Conference paper (Refereed)
    Abstract [en]

    Transition metal dichalcogenides (TMDs) such as WS2 are well-known for their layered structure and solid lubricant properties. However, beside low friction, a solid lubricant coating must also have a long wear life in order to perform well in a tribological situation. Thus, by adding carbon to the material the mechanical properties can be improved. However, when using a magnetron sputtering process, the resulting thin films are found to be sub-stoichiometric with respect to sulphur. This is due to a number of different effects; take-off angle, scattering, different sticking coefficients and energetic particle bombardment of the substrate.

    In this work we have used a non-reactive magnetron sputtering process to see how these effects affect the resulting film stoichiometry, and hence the tribological properties. This was done by changing the process pressure, DC-RF power, the location of the substrate (in and off axes) and by adding carbon to the material. Also, a newly developed Monte Carlo computer model is presented which makes it possible to simulate and predict how these changes will affect the resulting film stoichiometry.

    Simulations and experiments alike show that by reducing the energetic particle bombardment of the substrate, the S/W ratio increases. Tribological evaluation of the films concludes that an increasing S/W ratio is beneficial as it decreases the coefficient of friction of the films.

  • 463.
    Taher, Mamoun
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry. ABB AB, Corp Res, Insulat & Mat Technol, SE-72178 Vasterdas, Sweden.
    Mao, Fang
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Berastegui, Pedro
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Andersson, Anna M.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    The Influence of Chemical and Phase Composition on Mechanical, Tribological and Electrical Properties of Silver-Aluminum alloys2018In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 119, p. 680-687Article in journal (Refereed)
    Abstract [en]

    Ag1-xAlx alloys were investigated as potential sliding electrical contact materials. Seven Ag1-xAlx alloys, covering the different phase regions on the Ag-Al phase diagram, were prepared by arc melting. X-ray diffraction (XRD), scanning electron microscopy coupled with X-ray spectroscopy (SEM/EDX), X-ray photoelectron spectroscopy (XPS), nano- and microindentation, and four-point electrical contact resistance measurements were employed to characterize the composition, structure, and physicochemical properties of the alloys. The hardness of Ag1-xAlx alloys increases with Al content. The Ag1-xAlx alloys with hexagonal close-packed (hcp) structure exhibit better tribological properties than pure Ag and other phase compositions. The wear mechanisms change from adhesive, for the alloys with low Al content (<= 20 at. %) to oxidative and abrasive wear for the alloys with high Al content (>= 25 at. %). The Ag1-xAlx alloys with hcp structure exhibit the highest wear resistance. Depth-profile XPS data reveal that the oxide layer grows during the triboprocess and that its thickness increases with number of sliding cycles. Ag/Ag1-xAlx contact pairs exhibit higher contact resistance than the Ag/Ag pair and the contact resistance increases with Al content.

  • 464.
    Taher, Mamoun
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Mao, Fang
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Berastegui, Pedro
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Andersson, Anna M.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Tuning tribological, mechanical and electrical properties of Ag-X (X=Al, In, Sn) alloys2018In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 125, p. 121-127Article in journal (Refereed)
    Abstract [en]

    A new design concept for silver based alloys with a hexagonal structure as electrical contact materials with enhanced tribological properties has been investigated. The correlations between the phase composition and the tribological properties have been investigated in the Ag-Al, Ag-In and Ag-Sn systems. In each system, alloys with different chemical compositions were prepared by melting in evacuated ampoules. Characterisation techniques such as: optical microscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning and transmission electron microscopies (SEM and TEM) have been used to evaluate the microhardneas, tribological properties and contact resistance of the samples. The phase compositions of the synthesized Ag-Al and Ag-Sn alloys were in agreement with the phase diagrams and the metastable hcp phase was observed in the Ag-In system. The friction coefficients and wear rates of all the hcp-Ag-X (X = Al, In, Sn) alloys were considerably lower than pure Ag or fcc-Ag alloys. This is attributed mainly to easily shearing basal planes in the hcp structure. The Ag-Sn alloys showed high contact resistances, making them less suitable for a sliding electrical contacts. In contrast, the Ag-In alloys showed much lower contact resistance, making them better alternatives for practical applications.

  • 465.
    Tammela, Petter
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Preparation and characterization of a metal hydride electrode2012Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Metal hydrides are used as anode material in nickel metal hydride batteries and are of particular interest because of the potential to be a part of energy systems completely involving renewable sources (e.g. solar power, wind power etc.). Preparation and electrochemical characterization of metal hydride electrodes have not previously been performed at the Department of Chemistry – Ångström Laboratory. Two basic techniques that are desired to be used in the characterization are cyclic voltammetry and chronopotentiometry. This thesis work is aimed at preparation and electrochemical characterization of a metal hydride electrode and, as a complement, study the electrode with X-ray diffraction.

    LaNi3.55Co0.75Mn0.4Al0.3, a standard material for metal hydride electrodes previously studied by Khaldi et al. was chosen, to ensure that electrochemical absorption of hydrogen was possible, and to be able to compare electrochemical results [1-3]. LaNi3.55Co0.75Mn0.4Al0.3 was synthesized with arc melting, with additional annealing at 900˚C for five days, ground in a cemented carbide ball mill and sieved to less than 56 µm.

    Electrodes were prepared containing 90 wt.-% of LaNi3.55Co0.75Mn0.4Al0.3 powder, 5 wt.-% of polytetrafluoroethylene and 5 wt.-% of carbon black. The hydrogen absorption and desorption capabilities of the electrode were studied electrochemically with cyclic voltammetry and chronopotentiometry, and the structural changes associated with absorption of hydrogen was studied with X-ray diffraction.

    The capacity increased, probably from activation of the material, during initial cycling up to the maximum capacity of 294 mAh/g, obtained after 9 cycles, followed by a small decrease, probably caused by corrosion and passivation of the material, in capacity of the remaining 11 cycles. Activation of the material causes the charge and the discharge potential to shift to a more positive and a more negative value, respectively. The final values for the charge potential and the discharge potential were -841mV and -945 mV vs. Hg/HgO, respectively, after 16 cycles. Khalid et al. [1-3]reported a maximum capacity of 300 mAh/g, a charge potential of about -960 mV and a discharge potential of about -840 mV after 16 cycles the results obtained in this study are considered to be in good agreement with those reported.

    X-ray diffraction of the electrodes revealed, as expected, a cell volume change of the charged electrode compared to the discharged electrode. The change in cell volume corresponds to an estimated capacity of 303 mAh/g, which is very close to the, above mentioned, electrochemically obtained maximum capacity of 294 mAh/g.

  • 466.
    Tammela, Petter
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Olsson, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Strømme, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Nyholm, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    The influence of electrode and separator thickness on the cell resistance of symmetric cellulose–polypyrrole-based electric energy storage devices2014In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 272, p. 468-475Article in journal (Refereed)
    Abstract [en]

    The influence of the cell design of symmetric polypyrrole and cellulose-based electric energy storage devices on the cell resistance was investigated using chronopotentiometric and ac impedance measurements with different separator and electrode thicknesses. The cell resistance was found to be dominated by the electrolyte and current collector resistances while the contribution from the composite electrode material was negligible. Due to the electrolyte within the porous electrodes thin separators could be used in combination with thick composite electrodes without loss of performance. The paper separator contributed with a resistance of similar to 1.5 Omega mm(-1) in a 1.0 M NaNO3 electrolyte and the tortuosity value for the separator was about 2.5. The contribution from the graphite foil current collectors was about similar to 0.4-1.1 Omega and this contribution could not be reduced by using platinum foil current collectors due to larger contact resistances. The introduction of chopped carbon fibres into the electrode material or the application of pressure across the cells, however, decreased the charge transfer resistance significantly. As the present results demonstrate that cells with higher charge storage capacities but with the same cell resistance can be obtained by increasing the electrode thickness, the development of paper based energy storage devices is facilitated.

  • 467.
    Tammela, Petter
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Olsson, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Wang, Zhao-hui
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Sjödin, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Strömme, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Nyholm, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    The Influence Of The Separator And Electrode Thickness On The Cell Resistance For Energy Storage Devices Based On Polypyrrole-Cellulose Composites 2013In: Nordbatt1 2013, 2013, p. P52-Conference paper (Refereed)
  • 468.
    Tammela, Petter
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Olsson, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Wang, Zhaohui
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Strømme, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Nyholm, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Influence of Separator and Electrode Thickness on Cell Resistance in Energy Storage Devices based on Polypyrrole-Cellulose Composites2014In: GradSAM21 workshop 2014: Graduate School of Advanced Materials for the 21st Century, 2014Conference paper (Other academic)
    Abstract [en]

    The next-generation electronic industry requires access to inexpensive, flexible, light-weight and environmentally friendly energy storage devices [1]. Consequently, a lot of research has been directed toward producing versatile and flexible materials as a complement to the materials used in contemporary batteries and supercapacitors. Electroactive polymers represent an attractive alternative and electronically conducting polymers have hence received considerable interest as it is well-known that these materials can be used to manufacture all-polymer-based batteries and supercapacitors [2]. The performance of such energy storage devices is, however, ultimately limited by the resistance of the cell [3]. One important aspect is therefore to consider the cell resistance when optimizing the performance and cell design.

    Our recent activities have shown that a flexible and highly porous cellulose and polypyrrole composite, obtained by polymerizing pyrrole on cellulose from the Cladophora sp. algae, can be used as paper-based electrode materials and together with an aqueous salt solution form an environmentally friendly charge storage device [4, 5]. The cellulose-polypyrrole-based device proved to cycle for thousands of cycles without significant loss of capacity even at high charge and discharge rates.

    In the present work, the cell resistances of cellulose-polypyrrole-based charge storage devices are investigated, and the influence of electrode material and separator thickness are examined. The effect of absorption of electrolyte in the separator compared to bulk solutions of electrolyte, and the contact resistances between current collectors and the composite are discussed, as well as the possibilities of designing inexpensive all-organic energy storage devices with promising performance regarding cycling stability, rate capability and cell resistance.

  • 469.
    Tammela, Petter
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Olsson, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Wang, Zhaohui
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Strømme, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Nyholm, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Influence of Separator and Electrode Thickness on Cell Resistance in Energy Storage Devices based on Polypyrrole-Cellulose Composites2014In: MRS Spring meeting April 21-25, 2014 - San Francisco, California, 2014Conference paper (Other academic)
    Abstract [en]

    At present there is a strong need for the development of inexpensive, flexible, light-weight and environmentally friendly energy storage devices [1]. In this process, research is carried out to develop new versatile and flexible electrode materials as a complement to the materials used in contemporary batteries and supercapacitors. These activities have resulted in an increased interest in electronically conducting polymers (e.g. polyaniline, polypyrrole, and polythiophene) as it is known since more than two decades [2, 3] that these materials can be used to manufacture all-polymer-based batteries and supercapacitors. However, the latter devices generally suffer from problems due to low capacities, slow charging rates, poor cycling stabilities and high self-discharge rates [2]. Possible approaches to circumvent at least some of these problems involve the use of conducting polymers with carbon nanotubes [4] or cellulose [5].

    We have recently shown [5], that flexible composites, made of cellulose and polypyrrole, by chemical polymerization of pyrrole on a cellulose substrate derived from the Cladophora sp. algae, can be used as paper-based electrode materials for environmental friendly charge storage devices. The device, which has been referred to as the “Salt and Paper Battery” [6], was found to exhibit good cycling stability even at high charging and discharging rates. The latter results open up to exciting possibilities for the development of green and foldable devices as well as for a range of new applications, incompatible with conventional batteries and supercapacitors.

    The poster will focus on the results of our recent and ongoing research concerning polypyrrole and cellulose composite charge storage devices. It will be shown how the total cell resistances in the devices are influenced by thickness of the polypyrrole and cellulose composite, the thickness of the separator, and additives in the composite. Furthermore, the influence of the porosity of the separator, and the contact resistances between current collectors and the composite will be briefly discussed. It will be shown that a cheap all organic energy storage device can be assembled with promising performance.

  • 470.
    Tammela, Petter
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Wang, Zhaohui
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Frykstrand, Sara
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Zhang, Peng
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Sintorn, Ida-Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Visual Information and Interaction. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computerized Image Analysis and Human-Computer Interaction.
    Nyholm, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Strömme, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Asymmetric supercapacitors based on carbon nanofibre and polypyrrole/nanocellulose composite electrodes2015In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 5, no 21, p. 16405-16413Article in journal (Refereed)
    Abstract [en]

    Asymmetric, all-organic supercapacitors (containing an aqueous electrolyte), exhibiting a capacitance of 25 F g-1 (or 2.3 F cm-2) at a current density of 20 mA cm-2 and a maximum cell voltage of 1.6 V, are presented. The devices contain a composite consisting of polypyrrole covered Cladophora cellulose fibres (PPy-cellulose) as the positive electrode while a carbon nanofibre material, obtained by heat treatment of the same PPy-cellulose composite under nitrogen gas flow, serves as the negative electrode. Scanning and transmission electron microscopy combined with X-ray photoelectron spectroscopy data show that the heat treatment gives rise to a porous carbon nanofibre material, topologically almost identical to the original PPy-cellulose composite. The specific gravimetric capacitances of the carbon and the PPy-cellulose electrodes were found to be 59 and 146 F g-1, respectively, while the asymmetric supercapacitors exhibited a gravimetric energy density of 33 J g-1. The latter value is about two times higher than the energy densities obtainable for a symmetric PPy-cellulose device as a result of the larger cell voltage range accessible. The capacitance obtained for the asymmetric devices at a current density of 156 mA cm-2 was 11 F g-1 and cycling stability results further indicate that the capacity loss was about 23% during 1000 cycles employing a current density of 20 mA cm-2. The present results represent a significant step forward towards the realization of all-organic material based supercapacitors with aqueous electrolytes and commercially viable capacitances and energy densities.

  • 471.
    Tammela, Petter
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Wang, Zhaohui
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Nyholm, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Strømme, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    What if batteries could be made from paper2018In: Solutions for a Sustainable Future, 2018Conference paper (Other (popular science, discussion, etc.))
  • 472.
    Tammela, Petter
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Yamada, Shoko
    BillerudKorsnäs.
    Wang, Zhaohui
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Strømme, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Nyholm, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Paper based electrodes suitable for disposable packaging2018In: Intelligent and Connected Packaging Solutions, 2018Conference paper (Refereed)
  • 473. Tengstrand, O.
    et al.
    Nedfors, Nils
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Alling, B.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Flink, A.
    Eklund, P.
    Hultman, L.
    Incorporation effects of Si in TiCx thin films2014In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 258, p. 392-397Article in journal (Refereed)
    Abstract [en]

    Ti-Si-C thin films with varying Si content between 0 to 10 at.% were deposited by DC magnetron sputtering from elemental targets. The effects on microstructure and lattice parameters were investigated using x-ray diffraction, x-ray photoelectron spectroscopy, transmission electron microscopy, and first-principles calculations. The results show that the growth of pure TiCx onto Al2O3(0001) substrates at a temperature of 350 degrees C yields (111) epitaxial and understoichiometric films with x similar to 0.7. For Si contents up to 4 at.%, the TiCx epitaxy is retained locally. Si starts to segregate out from the TiCx to column boundaries at concentrations between 1 and 4 at.%, and causes a transition from epitaxial to polycrystalline growth above 4 at.%. Eventually, the top part of the films form a nanocomposite of crystalline TiC grains surrounded by amorphous SiC and C for Si contents studied up to 10 at.%. The results show that Si takes the place of carbon when incorporated in the TiC lattice.

  • 474. Tengstrand, Olof
    et al.
    Nedfors, Nils
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Andersson, Matilda
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Lu, Jun
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Flink, Axel
    Eklund, Per
    Hultman, Lars
    Beam-induced crystallization of amorphous Me-Si-C (Me = Nb or Zr) thin films during transmission electron microscopy2013In: MRS Communications, ISSN 2159-6859, Vol. 3, no 3, p. 151-155Article in journal (Refereed)
    Abstract [en]

    We report that an electron beam focused for high-resolution imaging rapidly initiates observable crystallization of amorphous Me-Si-C films. For 200-keV electron irradiation of Nb-Si-C and Zr-Si-C films, crystallization is observed at doses of similar to 2.8 x 10(9) and similar to 4.7 x 10(9) e(-)/nm(2), respectively. The crystallization process is driven by atomic displacement events, rather than heating from the electron beam as in situ annealing (400-600 degrees C) retains the amorphous state. Our findings demand a critical analysis of alleged amorphous and nanocrystalline ceramics including reassessing previous reports on nanocrystalline Me-Si-C films for possible electron-beam-induced crystallization effects.

  • 475. Tengstrand, Olof
    et al.
    Nedfors, Nils
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Andersson, Matilda
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Lu, Jun
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Flink, Axel
    Eklund, Per
    Hultman, Lars
    Model for electron-beam-induced crystallization of amorphous Me-Si-C (Me = Nb or Zr) thin films2014In: Journal of Materials Research, ISSN 0884-2914, E-ISSN 2044-5326, Vol. 29, no 23, p. 2854-2862Article in journal (Refereed)
    Abstract [en]

    We use transmission electron microscopy (TEM) for in situ studies of electron-beam-induced crystallization behavior in thin films of amorphous transition metal silicon carbides based on Zr (group 4 element) and Nb (group 5). Higher silicon content stabilized the amorphous structure while no effects of carbon were detected. Films with Nb start to crystallize at lower electron doses than the Zr-containing ones. During the crystallization, equiaxed MeC grains are formed in all samples with larger grains for ZrC (similar to 5 nm) compared to NbC (similar to 2 nm). The phenomenon of self-terminating crystallization at a dimension of 2-5 nm is explained by segregation of Si that is expelled from growing metal carbide grains into the surrounding amorphous phase matrix, which limits diffusion of the metal and carbon.

  • 476. Tengstrand, Olof
    et al.
    Nedfors, Nils
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Fast, Lars
    Flink, Axel
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Eklund, Per
    Hultman, Lars
    Structure and electrical properties of Nb-Ge-C nanocomposite coatings2014In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 32, no 4, p. 041509-Article in journal (Refereed)
    Abstract [en]

    Nb-Ge-C nanocomposite thin films were deposited by dc magnetron sputtering using three elemental targets. The films consist of substoichiometric NbCx in a nanometer-thick matrix of amorphous C and Ge. Films with no Ge contain grains that are elongated in the growth direction with a (111) preferred crystallographic orientation. With the addition of similar to 12 at. % Ge, the grains are more equiaxed and exhibit a more random orientation. At even higher Ge contents, the structure also becomes denser. The porous structure of the low Ge content films result in O uptake from the ambient. With higher C content in the films both the amount of amorphous C and C/Nb-ratio increases. The contact resistance was measured by four-point technique as a function of contact force between 0 and 10 N. The lowest contact resistance (1.7 m Omega) is obtained at 10 N. The resistivity varies between 470 and 1700 mu Omega center dot cm depending on porosity and O content.  

  • 477.
    Tian, Yuan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Biomolecule Functionalization of Diamond Surfaces for Implant Applications - A Theoretical Study2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Diamond is a promising material with unique chemical properties. In this thesis, nano-scale diamond quantum size effects were investigated using several chemical property indicators. The results show that the chemical properties are strongly dependent on size for film thicknesses smaller than 1 nm (1D), and for nanodiamond particle diameters less than 2 nm (3D). When the sizes exceed these ranges there are no longer any quantum effects.

    The influence of surface termination coverage on the surface chemical properties has been calculated for the 2×1 reconstructed diamond (100) surface and for the diamond (111) surface. The terminating species included COOH and NH2 groups, which both are beneficial for the immobilization of biomolecules. The results of the calculations show that it is energetically possible to terminate the diamond surfaces up to 100% with NH2, while it is only possible to cover the surfaces up to 50% with COOH species. The reason for the latter result is most probably the larger sterical hindrance amongst the adsorbates. Both types of termination species were shown to influence the diamond surface electronic properties (e.g., HOMO/LUMO levels).

    In order to extend the diamond utility for biomedical applications, especially implant design, interactions of various growth factors with the diamond surfaces were also simulated. For non-solvent diamond-biomolecule systems, the results show that adhesion affinities are strongly dependent on biomolecule molecular weights. When including a water based solvent in the systems, the results show good physisorption affinities between proteins and diamond. Proteins structures, before and after physisorption, were visualized, and further investigated with respect to electrostatic properties and functional groups. By comparing the biomolecular structural changes during the adhesion processes, it can be concluded that both the general structures, as well as the binding pocket structures, were kept intact after the adhesion to the diamond surfaces (regardless of the adhesion affinities). In addition, the surface electronic potential distributions were maintained, which indicate preserved biomolecule functionalities.

    List of papers
    1. Effect by diamond surface modification on biomolecular adhesion
    Open this publication in new window or tab >>Effect by diamond surface modification on biomolecular adhesion
    2019 (English)In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, no 6, article id 865Article in journal (Refereed) Published
    Abstract [en]

    Diamond, as material, show very attractive properties. They include superior electronic properties (when doped), chemical inertness, controllable surface termination, and biocompatibility. It is thus clear that surface termination is very important for those applications where the implant material is based on diamond. The present theoretical work has focused on the effect of diamond surface termination, in combination with type of surface plane, on the adhesion of important biomolecules for vascularization and bone regeneration. These biomolecules include Arginine-Glycine-Aspartic acid (RGD), Chitosan, Heparin, Bone Morphogenetic Protein 2 (BMP2), Angiopoietin 1 (AGP1), Fibronectin and Vascular Endothelial Growth Factor (VEGF). The various surface planes are diamond diamond (100)-2x1 and (111). The theoretical results show that the non-covalent binding of these biomolecules is in proportion with their molecular weights. Moreover, three groups of biomolecules were observed for both types of surface planes. The most strongly binding biomolecule was the BMP2 molecule. The smaller polypeptides (RGD, Chitosan and Heparin) formed a less strongly binding group. Finally, the biomolecules VEGF, Fibronectin and Angiopoietin showed bond strengths numerically in between the other two groups (thereby forming a third group). Moreover, the (111) surface was generally observed to display a stronger bonding of the biomolecules, as compared with the (100)-2x1 surface.

    Keywords
    Diamond; Theory; Biomolecules
    National Category
    Manufacturing, Surface and Joining Technology Medical Materials
    Research subject
    Chemistry with specialization in Materials Chemistry
    Identifiers
    urn:nbn:se:uu:diva-236954 (URN)10.3390/ma12060865 (DOI)000464362100016 ()30875868 (PubMedID)
    Projects
    Vascubone
    Funder
    EU, FP7, Seventh Framework Programme, 242175
    Note

    Title in thesis list of papers: Effect of diamond surface modification by biomolecular adhesion – a quantum mechanical study

    Available from: 2014-11-25 Created: 2014-11-25 Last updated: 2019-05-09Bibliographically approved
    2. Theoretical Study of Size Effects on Surface Chemical Properties for Nanoscale Diamond Particles
    Open this publication in new window or tab >>Theoretical Study of Size Effects on Surface Chemical Properties for Nanoscale Diamond Particles
    2014 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, no 45, p. 26061-26069Article in journal (Refereed) Published
    Abstract [en]

    Nanodiamond has displayed some unique physical and chemical properties compared to bulk diamond, which broadens its applications in various areas. However, a more detailed picture of nanodiamond quantum confinements is still missing from a theoretical point of view. This investigation presents a study where the effects of one-dimension (i.e., diamond thin films) and three-dimension (i.e., nanodiamond particles) confinement on surface reactivity, and properties, have been calculated using density functional theory (DFT) and tight binding density functional theory (DFTB) methods. Surface specific parameters like (i) surface C–H bond length, (ii) atomic charges, (iii) H adsorption energy, (iv) highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), (v) band gap, and (vi) Fukui functions were thereby carefully calculated and compared. For both the one-dimensional diamond thin films of different surface planes, quantum confinements have strong influences on these factors from thickness of 0.2 to ∼1 nm, while for thin films thicker than 1 nm, the values stabilize around a plateau value. For three-dimensional situations, these factors were found to change within a range of nanodiamond diameter of 0.4 to ∼2 nm, followed by oscillations around specific values as well. These results reveal that nanoscale diamond quantum confinements exist for a nanodiamond particle of a diameter smaller than 2 nm, but not for larger particle sizes. It must here be stressed that all surface specific parameters did independently show the existence of the here presented size ranges for quantum confinement.

    Place, publisher, year, edition, pages
    Washington, D.C.: American Chemical Society (ACS), 2014
    Keywords
    Nano-scale diamond, DFTB, Nanodiamond
    National Category
    Nano Technology
    Research subject
    Chemistry with specialization in Materials Chemistry
    Identifiers
    urn:nbn:se:uu:diva-236449 (URN)10.1021/jp507421u (DOI)000344978000029 ()
    Projects
    Vascubone
    Funder
    EU, FP7, Seventh Framework Programme, 242175
    Available from: 2014-11-19 Created: 2014-11-19 Last updated: 2017-12-05Bibliographically approved
    3. Protein Functionalized Diamond Surfaces in a Water Solvent – A Theoretical Approach
    Open this publication in new window or tab >>Protein Functionalized Diamond Surfaces in a Water Solvent – A Theoretical Approach
    (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    In order to improve the performances of a diamond-based implant material, surface functionalization with different proteins is a promising approach. The main goal of the present study has been to theoretically investigate the diamond functionalization by physisorption of different proteins onto different surface planes. The protein candidates selected are growth factors which can promote cell adhesion and growth, and subsequent vascularization surrounding the implanted materials. They include Bone Morphogenetic Protein 2 (BMP2), Vascular Endothelial Growth Factor (VEGF), Fibronectin (FN), and Angiopoietin (AGP). Moreover, it is well-known that diamond surface properties are strongly dependent on diamond surface planes and surface terminations. Therefore, the following two different diamond surface planes [diamond (100)-2x1 and diamond (111)], and four different kinds of terminations species (H, OH, COOH and NH2), where used in the present study. The results from force-field calculations show that the surface wettability is crucial for the protein adhesion onto the diamond surfaces, and the different proteins possess distinct preferences for diamond surface planes and terminations. For the identification of protein functionality, the atomic structures, in addition to corresponding electrostatic maps, were also visualized in the comparison of protein structures before and after adhesion to the diamond surfaces. It could be concluded that the protein structures and binding pocket electrostatic distributions are maintained as a result of the functionalization process, regardless of adhesion energy strength. These results provide a solid base for experimental protein functionalization of the diamond surfaces.  

    Keywords
    Diamond, Functionalization, BMP2, Angiopoietin, Fibronectin, VEGF
    National Category
    Medical Materials Manufacturing, Surface and Joining Technology
    Research subject
    Chemistry with specialization in Materials Chemistry
    Identifiers
    urn:nbn:se:uu:diva-236955 (URN)
    Projects
    Vascubone
    Funder
    EU, FP7, Seventh Framework Programme, 242175
    Available from: 2014-11-25 Created: 2014-11-25 Last updated: 2015-02-03
    4. Process of Diamond Surface Termination by Carboxylic and Amino groups: A Quantum Mechanics Approach
    Open this publication in new window or tab >>Process of Diamond Surface Termination by Carboxylic and Amino groups: A Quantum Mechanics Approach
    2019 (English)In: Journal of Material Sciences & Engineering, ISSN 2169-0022, Vol. 8, no 1, article id 506Article in journal (Refereed) Published
    Abstract [en]

    The main goal with the present work has been to study the possibility and thermodynamical stability for a sequential termination with either carboxylic groups (COOH), or amino groups (NH2), from an initially H-terminated diamond (111), or diamond (100)-2x1 surface. When sequentially substituting the H species with COOH groups, the total energy of adsorption onto the diamond (100)-2x1 surface was observed to drop from -5.45 eV (6.25%) to -26.22 eV (50%).  It was not possible to cover the surface with COOH species at a higher surface coverge. For the diamond (111) surface, the corresponding adsorption energy was calculated as -5.10 eV (6.25%) to -20.03 eV (50%). The values in parentheses are the COOH surface coverages. These values show that it is energetically preferable to terminate both types of surface planes to 50%. For NH2, it was observed possible to terminate both types of surface planes up to 100% coverage. The total adsorption energies went from -3.83 eV (6.25%) to -45.84 eV (100%) for the diamond (100)-2x1 surface, and from -3.61 eV (6.25%) to -39.91 eV (100%) for the diamond (111) surface.

    In order to follow the individual bond energy variations with variations in surface coverage, the averaged adsorption energies have also been calculated. As expected, the lowest COOH coverage resulted in the energetically most preferable adsorption energies [(-5.45 eV for diamond (100)-2x1, and -5.10 eV for diamond (111)]. The corresponding situation for the NH2 group was identical for the diamond (111) surface only, with the lowest surface leading to the most preferable adsorption situation (-3.61 eV for the first NH2 group). For the situation with diamond (100)-2x1, a continuous decrease in average adsorption energy was obtained when going from the lowest surface energy of 6.25 % (-3.83 eV) up to 43.75% (-3.95 eV). Hence, there is a thermodynamically preference for diamond (100)-2x1 to be terminated with NH2 groups for higher concentration up to 43.75%.

    Partial Density of States were calculated with the purpose to analyse the COOH-induced surface electronic properties, The results showed that NH2 groups will contribute to the shift of the LUMO or HOMO energy levels. As a result, this will lead to a decrease in the HOMO-LUMO gaps, being valid for both diamond surface planes. Moreover, partially filled states were observed in the HOMO-LUMO gaps for COOH-terminated diamond (100)-2x1 surface, as well as for both COOH- and NH2-terminated diamond (111) surfaces. These specific types of surface terminations thereby display surface conductivities, which were not observed for 100% H-terminated surfaces. 

    Keywords
    Carboxylic, Amino, Theory, Diamond
    National Category
    Materials Engineering Materials Chemistry
    Research subject
    Chemistry with specialization in Materials Chemistry
    Identifiers
    urn:nbn:se:uu:diva-236956 (URN)10.4172/2169-0022.1000506 (DOI)
    Projects
    Vascubone
    Funder
    EU, FP7, Seventh Framework Programme, 242175
    Available from: 2014-11-25 Created: 2014-11-25 Last updated: 2019-03-21Bibliographically approved
  • 478.
    Tian, Yuan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Larsson, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Effect by diamond surface modification on biomolecular adhesion2019In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, no 6, article id 865Article in journal (Refereed)
    Abstract [en]

    Diamond, as material, show very attractive properties. They include superior electronic properties (when doped), chemical inertness, controllable surface termination, and biocompatibility. It is thus clear that surface termination is very important for those applications where the implant material is based on diamond. The present theoretical work has focused on the effect of diamond surface termination, in combination with type of surface plane, on the adhesion of important biomolecules for vascularization and bone regeneration. These biomolecules include Arginine-Glycine-Aspartic acid (RGD), Chitosan, Heparin, Bone Morphogenetic Protein 2 (BMP2), Angiopoietin 1 (AGP1), Fibronectin and Vascular Endothelial Growth Factor (VEGF). The various surface planes are diamond diamond (100)-2x1 and (111). The theoretical results show that the non-covalent binding of these biomolecules is in proportion with their molecular weights. Moreover, three groups of biomolecules were observed for both types of surface planes. The most strongly binding biomolecule was the BMP2 molecule. The smaller polypeptides (RGD, Chitosan and Heparin) formed a less strongly binding group. Finally, the biomolecules VEGF, Fibronectin and Angiopoietin showed bond strengths numerically in between the other two groups (thereby forming a third group). Moreover, the (111) surface was generally observed to display a stronger bonding of the biomolecules, as compared with the (100)-2x1 surface.

  • 479.
    Tian, Yuan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Larsson, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Process of Diamond Surface Termination by Carboxylic and Amino groups: A Quantum Mechanics Approach2019In: Journal of Material Sciences & Engineering, ISSN 2169-0022, Vol. 8, no 1, article id 506Article in journal (Refereed)
    Abstract [en]

    The main goal with the present work has been to study the possibility and thermodynamical stability for a sequential termination with either carboxylic groups (COOH), or amino groups (NH2), from an initially H-terminated diamond (111), or diamond (100)-2x1 surface. When sequentially substituting the H species with COOH groups, the total energy of adsorption onto the diamond (100)-2x1 surface was observed to drop from -5.45 eV (6.25%) to -26.22 eV (50%).  It was not possible to cover the surface with COOH species at a higher surface coverge. For the diamond (111) surface, the corresponding adsorption energy was calculated as -5.10 eV (6.25%) to -20.03 eV (50%). The values in parentheses are the COOH surface coverages. These values show that it is energetically preferable to terminate both types of surface planes to 50%. For NH2, it was observed possible to terminate both types of surface planes up to 100% coverage. The total adsorption energies went from -3.83 eV (6.25%) to -45.84 eV (100%) for the diamond (100)-2x1 surface, and from -3.61 eV (6.25%) to -39.91 eV (100%) for the diamond (111) surface.

    In order to follow the individual bond energy variations with variations in surface coverage, the averaged adsorption energies have also been calculated. As expected, the lowest COOH coverage resulted in the energetically most preferable adsorption energies [(-5.45 eV for diamond (100)-2x1, and -5.10 eV for diamond (111)]. The corresponding situation for the NH2 group was identical for the diamond (111) surface only, with the lowest surface leading to the most preferable adsorption situation (-3.61 eV for the first NH2 group). For the situation with diamond (100)-2x1, a continuous decrease in average adsorption energy was obtained when going from the lowest surface energy of 6.25 % (-3.83 eV) up to 43.75% (-3.95 eV). Hence, there is a thermodynamically preference for diamond (100)-2x1 to be terminated with NH2 groups for higher concentration up to 43.75%.

    Partial Density of States were calculated with the purpose to analyse the COOH-induced surface electronic properties, The results showed that NH2 groups will contribute to the shift of the LUMO or HOMO energy levels. As a result, this will lead to a decrease in the HOMO-LUMO gaps, being valid for both diamond surface planes. Moreover, partially filled states were observed in the HOMO-LUMO gaps for COOH-terminated diamond (100)-2x1 surface, as well as for both COOH- and NH2-terminated diamond (111) surfaces. These specific types of surface terminations thereby display surface conductivities, which were not observed for 100% H-terminated surfaces. 

  • 480.
    Tian, Yuan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Larsson, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Protein Functionalized Diamond Surfaces in a Water Solvent – A Theoretical ApproachManuscript (preprint) (Other academic)
    Abstract [en]

    In order to improve the performances of a diamond-based implant material, surface functionalization with different proteins is a promising approach. The main goal of the present study has been to theoretically investigate the diamond functionalization by physisorption of different proteins onto different surface planes. The protein candidates selected are growth factors which can promote cell adhesion and growth, and subsequent vascularization surrounding the implanted materials. They include Bone Morphogenetic Protein 2 (BMP2), Vascular Endothelial Growth Factor (VEGF), Fibronectin (FN), and Angiopoietin (AGP). Moreover, it is well-known that diamond surface properties are strongly dependent on diamond surface planes and surface terminations. Therefore, the following two different diamond surface planes [diamond (100)-2x1 and diamond (111)], and four different kinds of terminations species (H, OH, COOH and NH2), where used in the present study. The results from force-field calculations show that the surface wettability is crucial for the protein adhesion onto the diamond surfaces, and the different proteins possess distinct preferences for diamond surface planes and terminations. For the identification of protein functionality, the atomic structures, in addition to corresponding electrostatic maps, were also visualized in the comparison of protein structures before and after adhesion to the diamond surfaces. It could be concluded that the protein structures and binding pocket electrostatic distributions are maintained as a result of the functionalization process, regardless of adhesion energy strength. These results provide a solid base for experimental protein functionalization of the diamond surfaces.  

  • 481.
    Tian, Yuan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Larsson, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Protein-Functionalized Diamond Surfaces in a Water Solvent: A Theoretical Approach2015In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 119, no 16, p. 8608-8618Article in journal (Refereed)
    Abstract [en]

    In order to improve the performance of a diamond-based implant material, surface functionalization with different proteins is a promising approach. The main goal of the present study has been to theoretically investigate the diamond functionalization by physisorption of different proteins onto different surface planes. The protein candidates selected are growth factors which can promote cell adhesion and growth and subsequent vascularization surrounding the implanted materials. They include Bone Morphogenetic Protein 2 (BMP2), Vascular Endothelial Growth Factor (VEGF), Fibronectin (FN), and Angiopoietin (AGP). Moreover, it is well-known that diamond surface properties are strongly dependent on diamond surface planes and surface terminations. Therefore, the following two different diamond surface planes [diamond (100)-2 x 1 and diamond (111)] and four different kinds of terminations species (H, OH, COOH, and NH2) were used in the present study. The results from force-field calculations show that the surface wettability is crucial for the protein adhesion onto the diamond surfaces, and the different proteins possess distinct preferences for diamond surface planes and terminations. For the identification of protein functionality, the atomic structures, in addition to corresponding electrostatic maps, were also visualized in the comparison of protein structures before and after adhesion to the diamond surfaces. It could be concluded that the protein structures and binding pocket electrostatic distributions are maintained as a result of the functionalization process, regardless of adhesion energy strength. These results provide a solid base for experimental protein functionalization of the diamond surfaces.

  • 482.
    Tian, Yuan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Larsson, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Theoretical Study of Size Effects on Surface Chemical Properties for Nanoscale Diamond Particles2014In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, no 45, p. 26061-26069Article in journal (Refereed)
    Abstract [en]

    Nanodiamond has displayed some unique physical and chemical properties compared to bulk diamond, which broadens its applications in various areas. However, a more detailed picture of nanodiamond quantum confinements is still missing from a theoretical point of view. This investigation presents a study where the effects of one-dimension (i.e., diamond thin films) and three-dimension (i.e., nanodiamond particles) confinement on surface reactivity, and properties, have been calculated using density functional theory (DFT) and tight binding density functional theory (DFTB) methods. Surface specific parameters like (i) surface C–H bond length, (ii) atomic charges, (iii) H adsorption energy, (iv) highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), (v) band gap, and (vi) Fukui functions were thereby carefully calculated and compared. For both the one-dimensional diamond thin films of different surface planes, quantum confinements have strong influences on these factors from thickness of 0.2 to ∼1 nm, while for thin films thicker than 1 nm, the values stabilize around a plateau value. For three-dimensional situations, these factors were found to change within a range of nanodiamond diameter of 0.4 to ∼2 nm, followed by oscillations around specific values as well. These results reveal that nanoscale diamond quantum confinements exist for a nanodiamond particle of a diameter smaller than 2 nm, but not for larger particle sizes. It must here be stressed that all surface specific parameters did independently show the existence of the here presented size ranges for quantum confinement.

  • 483.
    Travnikova, Oksana
    et al.
    Sorbonne Univ, LCPMR, CNRS, UMR7614, Paris, France;LOrme Merisiers, Synchrotron Soleil, F-91192 Gif Sur Yvette, France.
    Patanen, Minna
    Univ Oulu, Fac Sci, Nano & Mol Syst Res Unit, POB 3000, Oulu 90014, Finland.
    Söderström, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Lindblad, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Kas, Joshua J.
    Univ Washington, Dept Phys, Box 351560, Seattle, WA 98195 USA.
    Yila, Fernando D.
    Univ Washington, Dept Phys, Box 351560, Seattle, WA 98195 USA.
    Ceolin, Denis
    LOrme Merisiers, Synchrotron Soleil, F-91192 Gif Sur Yvette, France.
    Marchenko, Tatiana
    Sorbonne Univ, LCPMR, CNRS, UMR7614, Paris, France;LOrme Merisiers, Synchrotron Soleil, F-91192 Gif Sur Yvette, France.
    Goldsztejn, Gildas
    Sorbonne Univ, LCPMR, CNRS, UMR7614, Paris, France.
    Guillemin, Renaud
    Sorbonne Univ, LCPMR, CNRS, UMR7614, Paris, France;LOrme Merisiers, Synchrotron Soleil, F-91192 Gif Sur Yvette, France.
    Journel, Loic
    Sorbonne Univ, LCPMR, CNRS, UMR7614, Paris, France;LOrme Merisiers, Synchrotron Soleil, F-91192 Gif Sur Yvette, France.
    Carroll, Thomas X.
    Keuka Coll, Div Nat Sci, Keuka Pk, NY 14478 USA.
    Borve, Knut J.
    Univ Bergen, Dept Chem, Allegaten 41, NO-5007 Bergen, Norway.
    Decleva, Piero
    Univ Trieste, Dipartimento Sci Chim & Farmaceut, I-34127 Trieste, Italy;CNR, IOM, I-34127 Trieste, Italy.
    Rehr, John J.
    Univ Washington, Dept Phys, Box 351560, Seattle, WA 98195 USA.
    Mårtensson, Nils
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Simon, Marc
    Sorbonne Univ, LCPMR, CNRS, UMR7614, Paris, France;LOrme Merisiers, Synchrotron Soleil, F-91192 Gif Sur Yvette, France.
    Svensson, Svante
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Saethre, Leif J.
    Univ Bergen, Dept Chem, Allegaten 41, NO-5007 Bergen, Norway.
    Energy-Dependent Relative Cross Sections in Carbon 1s Photoionization: Separation of Direct Shake and Inelastic Scattering Effects in Single Molecules2019In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 123, no 35, p. 7619-7635Article in journal (Refereed)
    Abstract [en]

    We demonstrate that the possibility of monitoring relative photoionization cross sections over a large photon energy range allows us to study and disentangle shake processes and intramolecular inelastic scattering effects. In this gas-phase study, relative intensities of the carbon 1s photoelectron lines from chemically inequivalent carbon atoms in the same molecule have been measured as a function of the incident photon energy in the range of 300-6000 eV. We present relative cross sections for the chemically shifted carbon 1s lines in the photoelectron spectra of ethyl trifluoroacetate (the "ESCA" molecule). The results are compared with those of methyl trifluoroacetate and S-ethyl trifluorothioacetate as well as a series of chloro-substituted ethanes and 2-butyne. In the soft X-ray energy range, the cross sections show an extended X-ray absorption fine structure type of wiggles, as was previously observed for a series of chloroethanes. The oscillations are damped in the hard X-ray energy range, but deviations of cross-section ratios from stoichiometry persist, even at high energies. The current findings are supported by theoretical calculations based on a multiple scattering model. The use of soft and tender X-rays provides a more complete picture of the dominant processes accompanying photoionization. Such processes reduce the main photoelectron line intensities by 20-60%. Using both energy ranges enabled us to discern the process of intramolecular inelastic scattering of the outgoing electron, whose significance is otherwise difficult to assess for isolated molecules. This effect relates to the notion of the inelastic mean free path commonly used in photoemission studies of clusters and condensed matter.

  • 484.
    Tsigkourakos, Menelaos
    et al.
    IMEC, B-3001 Leuven, Belgium.;Katholieke Univ Leuven, Dept Phys & Astron, B-3001 Leuven, Belgium..
    Hantschel, Thomas
    IMEC, B-3001 Leuven, Belgium..
    Xu, Zheng
    IMEC, B-3001 Leuven, Belgium.;Katholieke Univ Leuven, Dept Phys & Astron, B-3001 Leuven, Belgium..
    Douhard, Bastien
    IMEC, B-3001 Leuven, Belgium..
    Meersschaut, Johan
    IMEC, B-3001 Leuven, Belgium..
    Zou, Yiming
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Larsson, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Boman, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Vandervorst, Wilfried
    IMEC, B-3001 Leuven, Belgium.;Katholieke Univ Leuven, Dept Phys & Astron, B-3001 Leuven, Belgium..
    Suppression of boron incorporation at the early growth phases of boron-doped diamond thin films2015In: Physica Status Solidi (a) applications and materials science, ISSN 1862-6300, E-ISSN 1862-6319, Vol. 212, no 11, p. 2595-2599Article in journal (Refereed)
    Abstract [en]

    The presence of O during the chemical vapour deposition (CVD) of B-doped diamond results in the suppression of B incorporation into the diamond film. In this study, we demonstrate that the amount of residual O within the chamber is higher at the beginning of the diamond growth due to the O-contaminated chamber walls, and is decreased after a certain time period. This leads to a gradual increase of the B incorporation by more than one order of magnitude during the early growth phases of nanocrystalline diamond (NCD). We further show that this suppression of B incorporation at the early growth phases of B-doped diamond is influenced by the growth rate of the film. This is attributed to the constant time period whereby most of the residual O interacts with the B-precursors in the gas phase by forming stable B-O species, which are flushed out from the chamber exhaust. Furthermore, the constant B profile of an NCD film grown in a loadlock hot-filament CVD (HFCVD) system reveals that the amount of residual O is constant and minimal during the growth process. Therefore, our work proves that the use of a loadlock overcomes the B-suppression problem at the early growth phases of diamond, making it the optimal solution for the growth of highly conductive thin diamond films.

  • 485.
    Unger, Eva L.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Edvinsson, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Roy-Mayhew, Joseph D.
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Johansson, Erik M. J.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Excitation Energy Dependent Charge Separation at Hole-Transporting Dye/TiO2 Hetero Interface2012In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 116, no 40, p. 21148-21156Article in journal (Refereed)
    Abstract [en]

    Interfacial charge separation in hybrid solar cells depends on both the energetic alignment and electronic coupling between the inorganic and organic semiconducting materials at the hetero interface. In the present work, bilayer solar cells comprising the small molecular semiconducting dye TDCV-TPA (tris-(thienylene-vinylene)-triphenylamine) and dense titanium dioxide (TiO2) films were investigated. The internal quantum efficiency and degree of photoluminescence quenching were found to be excitation energy dependent. The molecular interaction and interfacial energy level alignment was investigated using a combination of UV-vis and photoelectron spectroscopy (PES). Stationary and time-dependent density functional theory calculations were used to assign and distinguish between different experimentally determined molecular energy levels (PES) and electronic transitions (UV-vis). Photoelectron spectroscopy results suggest surface induced interactions of TDCV-TPA with TiO2 involving the peripheral CN-groups of the molecule which would imply a favorable electronic coupling for photoinduced interfacial charge transfer. In an energy level diagram distinguishing between the different electronic transitions in the molecule, the differences in the thermodynamic driving force for electron injection from the excited states were found small. Therefore, it is suggested that the observed higher internal quantum efficiency at shorter wavelength can be rationalized by a more favorable driving force for the regeneration of holes created at the hetero interface at higher excitation energy.

  • 486.
    Unger, Eva L.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Edvinsson, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Roy-Mayhew, Joseph D.
    Department of Chemical and Biological Engineering, Princeton University, USA.
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Johansson, Erik M. J.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Excitation energy dependent charge separation at small-molecular semiconductor/TiO2 interfaceManuscript (preprint) (Other academic)
    Abstract [en]

    Interfacial charge separation in hybrid solar cells depends on the energetic alignment and electronic coupling between the inorganic and organic semiconducting materials at the hetero-interface. In the present work, bilayer solar cells comprising the small molecular semiconducting dye TDCV-TPA (tris-(thienylene-vinylene)-triphenylamine) and dense titanium dioxide (TiO2) films were investigated. The internal quantum efficiency and degree of photoluminescence quenching were found to be excitation energy dependent. The molecular interaction and interfacial energy level alignment was investigated by a combination of UV-Vis and photoelectron spectroscopy. Stationary and time-dependent density functional theory calculations were used to assign and distinguish between experimentally determined molecular energy levels and electronic transitions. Photoelectron spectroscopy results suggest surface induced interactions of TDCV-TPA involving peripheral CN-groups. This may imply a favourable electronic coupling to the inorganic semiconductor for interfacial charge transfer. In an energy level diagram distinguishing between the different electronic transitions in the molecule the differences in the thermodynamic driving force for electron injection were found small. Therefore it is suggested that the observed higher internal quantum efficiency at shorter wavelength can be rationalized by a more favourable driving force for the regeneration of holes created at the hetero-interface at higher excitation energy.

  • 487.
    Valvo, Mario
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Rehnlund, David
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Lafont, Ugo
    Hahlin, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Nyholm, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.