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Das, S., Pal, S., Larsson, K., Mandal, D., Giri, S., Banerji, P., . . . Basori, R. (2023). Hydrothermally grown SnS2/Si nanowire core-shell heterostructure photodetector with excellent optoelectronic performances. Applied Surface Science, 624, Article ID 157094.
Open this publication in new window or tab >>Hydrothermally grown SnS2/Si nanowire core-shell heterostructure photodetector with excellent optoelectronic performances
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2023 (English)In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 624, article id 157094Article in journal (Refereed) Published
Abstract [en]

Core-shell nanowire heterostructure is a new architecture for photodetector application with enlarged active surface area enhancing light absorption and photodetector performance. As an emanating coating material, SnS2 has a growing interest in next-generation optoelectronic materials. Here, we reported the enhanced optoelectronic performance of the hydrothermally grown SnS2 and Si nanowire (SiNWs) core-shell heterostructure. Hydrothermally grown SnS2 on Si nanowire creates a uniform coating over the entire surface of nanowires which enhances the heterostructure's effective junction area and improves optoelectronic performance over the broad spectral range (300 - 1100 nm). Specially, under 340 nm illumination, the core-shell photodetector exhibits large responsivity (-383 A/W) and extremely high external quantum efficiency (-2 x 105 %) at very low optical power (-20 nW/mm2). This SnS2/SiNWs core-shell heterostructure with significantly improved optoelectronic performance will be favourable for the development of photodetector with an ability to work with extremely high efficiency.

Place, publisher, year, edition, pages
Elsevier, 2023
Keywords
SnS 2, Si nanowire, Core -shell heterostructure, EQE, Responsivity, Low-power photodetector, Enhanced active junction area, Cylindrical built-in-potential
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-501323 (URN)10.1016/j.apsusc.2023.157094 (DOI)000968469400001 ()
Available from: 2023-05-05 Created: 2023-05-05 Last updated: 2023-05-05Bibliographically approved
Buchner, F., Kirschbaum, T., Venerosy, A., Girard, H., Arnault, J.-C., Kiendl, B., . . . Merschjann, C. (2022). Early dynamics of the emission of solvated electrons from nanodiamonds in water. Nanoscale, 14(46), 17188-17195
Open this publication in new window or tab >>Early dynamics of the emission of solvated electrons from nanodiamonds in water
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2022 (English)In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 14, no 46, p. 17188-17195Article in journal (Refereed) Published
Abstract [en]

Solvated electrons are among the most reductive species in an aqueous environment. Diamond materials have been proposed as a promising source of solvated electrons, but the underlying emission process in water remains elusive so far. Here, we show spectroscopic evidence for the emission of solvated electrons from detonation nanodiamonds upon excitation with both deep ultraviolet (225 nm) and visible (400 nm) light using ultrafast transient absorption. The crucial role of surface termination in the emission process is evidenced by comparing hydrogenated, hydroxylated and carboxylated nanodiamonds. In particular, a transient response that we attribute to solvated electrons is observed on hydrogenated nanodiamonds upon visible light excitation, while it shows a sub-ps recombination due to trap states when excited with deep ultraviolet light. The essential role of surface reconstructions on the nanodiamonds in these processes is proposed based on density functional theory calculations. These results open new perspectives for solar-driven emission of solvated electrons in an aqueous phase using nanodiamonds.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2022
National Category
Condensed Matter Physics Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-490740 (URN)10.1039/d2nr03919b (DOI)000888292300001 ()36394505 (PubMedID)
Funder
EU, Horizon 2020, 665085
Available from: 2022-12-14 Created: 2022-12-14 Last updated: 2022-12-14Bibliographically approved
Wang, X., Song, X., Qiao, Y., Larsson, K. & Sun, F. (2022). Effects of urea versus N-2 addition on growth and mechanical properties of HFCVD diamond films on WC-Co substrates. Diamond and related materials, 125, Article ID 108999.
Open this publication in new window or tab >>Effects of urea versus N-2 addition on growth and mechanical properties of HFCVD diamond films on WC-Co substrates
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2022 (English)In: Diamond and related materials, ISSN 0925-9635, E-ISSN 1879-0062, Vol. 125, article id 108999Article in journal (Refereed) Published
Abstract [en]

Nitrogen doped diamonds with great application potentials can be synthesized by using different doping sources (i.e., urea and N2), effects of which on growth behavior and properties of diamond films on WC-Co substrates were presented in this paper. The doping efficiency of urea was always higher than 0.12, much higher than that of N2 (always lower than 0.04). The sufficient N2 addition could increase growth rate, and induce apparent grain nanocrystallization, by modifying reactant gas phase chemistry. The grain nanocrystallization contributed more to the reduction of the surface roughness, and degradation of the diamond purity and mechanical properties. On the contrary, the urea doping resulted in much less degradation of the diamond purity and mechanical properties, while providing sufficient N incorporations into the diamonds. Besides, urea doping promoted the formation of the diamond (220) planes on the polycrystalline diamond surfaces, which had a close relationship with the actual N doping concentration in the diamond. The controllable adjustment of the growth and properties of diamond films, by selecting the doping source and optimizing the doping ratio, could help to meet distinctive application requirements, and balance the machining efficiency and application performance of diamond coated components.

Place, publisher, year, edition, pages
ElsevierElsevier BV, 2022
Keywords
Nitrogen, Urea, N-doped, Diamond film, WC-Co substrate, HFCVD
National Category
Materials Chemistry Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-474709 (URN)10.1016/j.diamond.2022.108999 (DOI)000790962500007 ()
Available from: 2022-05-23 Created: 2022-05-23 Last updated: 2024-01-15Bibliographically approved
Wang, X., Qiao, Y., Larsson, K. & Sun, F. (2021). Energetic stability and geometrical structure of variously terminated and N-doped diamond (111) surfaces - A theoretical DFT study. Materials Chemistry and Physics, 262, Article ID 124283.
Open this publication in new window or tab >>Energetic stability and geometrical structure of variously terminated and N-doped diamond (111) surfaces - A theoretical DFT study
2021 (English)In: Materials Chemistry and Physics, ISSN 0254-0584, E-ISSN 1879-3312, Vol. 262, article id 124283Article in journal (Refereed) Published
Abstract [en]

H-, O-, OH- and F-terminated N-doped diamond surfaces are calculated by the density functional theory in the present study. Combined effects of terminating species and substitutional N dopants in the 1st or 2nd carbon layers on several critical features (i.e., bond length, total electron density, bond population, atomic charge, Fukui function, and density-of-states) are systematically studied and discussed. The N dopant presents clear, but local, effects for all the terminating species and dopant positions. The adsorption of any individual species to the N dopant in the 1st carbon layer results in the reduction of adsorption energy (less negative), most probably owing to the full shell structure of this N dopant. The H, OH and F each provides one unpaired electron to occupy the antibonding states within the N-H, N-OH and N-F bonds, making the bonds elongated, reducing the corresponding electron densities and bond populations. On the contrary, the N dopant in the 2nd carbon layer induces slight increment of the adsorption energy for O, OH and F, attributed to the positive atomic charges of neighboring topmost C atoms. Amongst the four adsorbates, the O shows the highest reactivity to either an electrophilic or a nucleophilic attack. Besides, N dopants have slight influences on the reactivity of the adjacent adsorbates. The present results can help to understand some related chemical processes (such as the oxidation and electrochemical analysis) on N-doped diamond films.

Place, publisher, year, edition, pages
ElsevierELSEVIER SCIENCE SA, 2021
Keywords
Diamond film, Nitrogen doping, Termination, Energetic stability, Geometrical structure
National Category
Inorganic Chemistry Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-439821 (URN)10.1016/j.matchemphys.2021.124283 (DOI)000620878200001 ()
Available from: 2021-04-12 Created: 2021-04-12 Last updated: 2024-01-15Bibliographically approved
Kim, K. H., He, H., Rodner, M., Yakimova, R., Larsson, K., Piantek, M., . . . Lara-Avila, S. (2020). Chemical Sensing with Atomically Thin Platinum Templated by a 2D Insulator. Advanced Materials Interfaces, 7(12), Article ID 1902104.
Open this publication in new window or tab >>Chemical Sensing with Atomically Thin Platinum Templated by a 2D Insulator
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2020 (English)In: Advanced Materials Interfaces, ISSN 2196-7350, Vol. 7, no 12, article id 1902104Article in journal (Refereed) Published
Abstract [en]

Boosting the sensitivity of solid-state gas sensors by incorporating nanostructured materials as the active sensing element can be complicated by interfacial effects. Interfaces at nanoparticles, grains, or contacts may result in nonlinear current-voltage response, high electrical resistance, and ultimately, electric noise that limits the sensor read-out. This work reports the possibility to prepare nominally one atom thin, electrically continuous platinum layers by physical vapor deposition on the carbon zero layer (also known as the buffer layer) grown epitaxially on silicon carbide. With a 3-4 angstrom thin Pt layer, the electrical conductivity of the metal is strongly modulated when interacting with chemical analytes, due to charges being transferred to/from Pt. The strong interaction with chemical species, together with the scalability of the material, enables the fabrication of chemiresistor devices for electrical read-out of chemical species with sub part-per-billion (ppb) detection limits. The 2D system formed by atomically thin Pt on the carbon zero layer on SiC opens up a route for resilient and high sensitivity chemical detection, and can be the path for designing new heterogenous catalysts with superior activity and selectivity.

Place, publisher, year, edition, pages
WILEY, 2020
Keywords
atomically thin materials, buffer layer, chemical sensors, nanomaterials
National Category
Condensed Matter Physics Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-423819 (URN)10.1002/admi.201902104 (DOI)000528714500001 ()
Funder
Swedish Foundation for Strategic Research , IS14-0053Swedish Foundation for Strategic Research , GMT14-0077Swedish Foundation for Strategic Research , RMA15-0024Knut and Alice Wallenberg FoundationSwedish Research Council, 2015-03758
Available from: 2020-10-29 Created: 2020-10-29 Last updated: 2020-10-29Bibliographically approved
Bayani, A. & Larsson, K. (2020). Intercalation of Au Atoms into SiC(0001)/Buffer Interfaces: A First-Principles Density Functional Theory Study. ACS Omega, 5(24), 14842-14846
Open this publication in new window or tab >>Intercalation of Au Atoms into SiC(0001)/Buffer Interfaces: A First-Principles Density Functional Theory Study
2020 (English)In: ACS Omega, E-ISSN 2470-1343, Vol. 5, no 24, p. 14842-14846Article in journal (Refereed) Published
Abstract [en]

The process of Au intercalation into a SiC/buffer interface has been theoretically investigated here by using density functional theory (DFT) and the nudged elastic band (NEB) method. Energy barriers were at first calculated (using NEB) for the transfer of an Au atom through a free-standing graphene sheet. The graphene sheet was either of a nondefect character or with a defect in the form of an enlarged hexagonal carbon ring. Defects in the form of single and double vacancies were also considered. Besides giving a qualitative prediction of the relative energy barriers for the corresponding SiC/buffer interfaces, some of the graphene calculations also proved evidence of energy minima close to the graphene sheet. The most stable Au positions within the SiC/buffer interface were, therefore, calculated by performing geometry optimization with Au in the vicinity of the buffer layer. Based on these NEB and DFT calculations, two factors were observed to have a great influence on the Au intercalation process: (i) energy barrier and (ii) preferential bonding of Au to the radical C atoms at the edges of the vacancies. The energy barriers were considerably smaller in the presence of vacancies. However, the Au atoms preferred to bind to the edge atoms of these vacancies when approaching the buffer layer. It can thereby be concluded that the Au intercalation will only occur for a nondefect buffer layer when using high temperature and/or by using high-energy impacts by Au atoms. For this type of Au intercalation, the buffer layer will become completely detached from the SiC surface, forming a single layer of graphene with an intact Dirac point.

National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:uu:diva-416591 (URN)10.1021/acsomega.0c01985 (DOI)000543740600067 ()32596622 (PubMedID)
Funder
Swedish Foundation for Strategic Research
Available from: 2020-07-22 Created: 2020-07-22 Last updated: 2020-12-15Bibliographically approved
Wang, X., Song, X., Wang, H., Qiao, Y., Larsson, K. & Sun, F. (2020). Selective Control of Oxidation Resistance of Diamond by Dopings. ACS Applied Materials and Interfaces, 12(37), 42302-42313
Open this publication in new window or tab >>Selective Control of Oxidation Resistance of Diamond by Dopings
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2020 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 12, no 37, p. 42302-42313Article in journal (Refereed) Published
Abstract [en]

A method based on the density functional theory calculations is proposed for predicting the influences of dopants on the diamond oxidation, by evaluating the O adsorption energy, chemical bond weakening related to desorption, and probable products. It is proven by verification tests that oxidation resistances of the diamond materials can be indeed selectively controlled (e.g., -36 to 54.3% for diamond films, -36.5 to 45.1% for diamond grits) by adding various doping sources ((CH3O)(3)B, Si(OC2H5)(4), N-2, and CO(NH2)(2)), attributed to their direct impurity incorporation, or modified gas chemistry. B and Si dopings can improve the oxidation resistance, but the addition of N-2 or urea plays an opposite role. Reactive ion etching and chemomechanical polishing tests are also accomplished, further demonstrating the influences of dopings on oxidation-related processes. This study paves the way for enhancing the efficiencies of the ultraprecision machining and micro-nano machining on the diamonds. Most importantly, the proposed prediction method can be potentially used in similar cases with other dopants and in other materials.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2020
Keywords
diamond, oxidation resistance, doping, selective control, DFT calculations
National Category
Inorganic Chemistry Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-422995 (URN)10.1021/acsami.0c11215 (DOI)000572965700136 ()32803960 (PubMedID)
Available from: 2020-10-19 Created: 2020-10-19 Last updated: 2020-10-19Bibliographically approved
Larsson, K. (2020). The Combined Influence of Dopant Species and Surface Termination on the Electronic Properties of Diamond Surfaces. C-JOURNAL OF CARBON RESEARCH, 6(2), Article ID 22.
Open this publication in new window or tab >>The Combined Influence of Dopant Species and Surface Termination on the Electronic Properties of Diamond Surfaces
2020 (English)In: C-JOURNAL OF CARBON RESEARCH, ISSN 2311-5629, Vol. 6, no 2, article id 22Article, review/survey (Refereed) Published
Abstract [en]

The combined effects of geometrical structure and chemical composition on the diamond surface electronic structures have been investigated in the present study by using high-level theoretical calculations. The effects of diamond surface planes [(111) vs. (100)], surface terminations (H, F, OH, O-ontop, O-bridge, vs. NH2), and substitutional doping (B, N vs. P), were of the largest interest to study. As a measure of different electronic structures, the bandgaps, work functions, and electron affinities have been used. In addition to the effects by the doping elements, the different diamond surface planes [(111) vs. (100)] were also observed to cause large differences in the electronic structures. With few exceptions, this was also the case for the surface termination species. For example, O-ontop-termination was found to induce surface electron conductivities for all systems in the present study (except for a non-doped (100) surface). The other types of surface terminating species induced a reduction in bandgap values. The calculated bandgap ranges for the (111) surface were 3.4-5.7 (non-doping), and 0.9-5.3 (B-doping). For the (100) surface, the ranges were 0.9-5.3 (undoping) and 3.2-4.3 (B-doping). For almost all systems in the present investigation, it was found that photo-induced electron emission cannot take place. The only exception is the non-doped NH2-terminated diamond (111) surface, for which a direct photo-induced electron emission is possible.

Keywords
diamond, doping, surface termination, electronic structure, band gap, work function, electron affinity, electron emission
National Category
Inorganic Chemistry Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-420358 (URN)10.3390/c6020022 (DOI)000551266600008 ()
Available from: 2020-09-25 Created: 2020-09-25 Last updated: 2020-09-25Bibliographically approved
Bayani, A., Kishore, M. R. & Larsson, K. (2020). The influence by substrate morphology on the Rashba band splitting in graphene. Results in Physics, 17, Article ID 103065.
Open this publication in new window or tab >>The influence by substrate morphology on the Rashba band splitting in graphene
2020 (English)In: Results in Physics, ISSN 2211-3797, Vol. 17, article id 103065Article in journal (Refereed) Published
Abstract [en]

The influence of substrate morphology on the Rashba band splitting at the Dirac point of graphene, has been theoretically investigated. More specifically, the possibility for this splitting to be caused by spin–orbit coupling (with the heavy metal substrate) was of a special interest to study. The model system consisted of a 4H-SiC (0 0 0 1)/graphene interface, with an intercalated metal layer (Ag and Au, respectively). These intercalating metal layers were built with two different types of morphologies; either flat or buckled (with different buckling positions). The results show that depending on the position of the buckled metal atom, the size of the bandgap and band splitting (at the Dirac point of graphene) will either increase (or decrease). Moreover, the enlargement of the buckling size was also shown to affect the electronic properties of graphene (i.e., by increasing the bandgap). The sizes of the bandgaps and band splitting for the different intercalating metals (Ag and Au), were also found to be different. Spin-projected band structures was also implemented in the present study, with the purpose to show the spin-texture of graphene. It was thereby shown that the spins pined to the x and y spin components for most of the cases.

Place, publisher, year, edition, pages
Elsevier, 2020
Keywords
Graphene Substrate morphology Spin–orbit coupling Rashba effect DFT Hybridization Spin components BSSE
National Category
Inorganic Chemistry Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-408657 (URN)10.1016/j.rinp.2020.103065 (DOI)000548696600004 ()
Funder
Swedish Foundation for Strategic Research , RMA 15-0024
Available from: 2020-04-09 Created: 2020-04-09 Last updated: 2020-10-09Bibliographically approved
Bayani, A. & Larsson, K. (2020). The morphology of an intercalated Au layer with its effect on the Dirac point of graphene. Scientific Reports, 10(1)
Open this publication in new window or tab >>The morphology of an intercalated Au layer with its effect on the Dirac point of graphene
2020 (English)In: Scientific Reports, E-ISSN 2045-2322, Vol. 10, no 1Article in journal (Refereed) Published
Abstract [en]

This is a theoretical investigation where Density Functional Theory (DFT) has been used in studying the phenomenon of Au intercalation within the 4H-SiC/graphene interface. The electronic structure of some carefully chosen morphologies of the Au layer has then been of special interest to study. One of these specific Au morphologies is of a more hypothetical nature, whilst the others are, from an experimental point of view, realistic ones. The latter ones were also found to be energetically stable. Band structure calculations showed that intercalated Au layers with morphologies different from a planar Au layer will induce a band gap at the Dirac point of graphene (with up to 174 meV for the morphologies studied in the present work). It should here be mentioned that this bandgap size is four times larger than the energy of thermal motion at room temperature (26 meV). These findings reveal that a wide bandgap at the Dirac point of graphene comes from an inhomogeneous staggered potential on the Au layer, which non-uniformly breaks the sublattice symmetry. The presence of spin-orbit (SO) interactions have also been included in the present study, with the purpose to find out if SO will create a bandgap and/or band splitting of graphene.

National Category
Condensed Matter Physics Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-403372 (URN)10.1038/s41598-020-57982-z (DOI)000561033100001 ()31974486 (PubMedID)
Funder
Swedish Foundation for Strategic Research , RMA 15-0024
Available from: 2020-04-09 Created: 2020-04-09 Last updated: 2022-09-15Bibliographically approved
Projects
Development and tailoring of surfaces and interfaces for renewable energy applications - step II [2012-04107_VR]; Uppsala UniversityDevelopment of new hybrid materials for photocatalytic applications [2016-04674_VR]; Uppsala University
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-4156-9442

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