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Publications (10 of 81) Show all publications
Jablonka, L., Riekehr, L., Zhang, Z., Zhang, S.-L. & Kubart, T. (2018). Highly conductive ultrathin Co films by high-power impulse magnetron sputtering. Applied Physics Letters, 112(4), Article ID 043103.
Open this publication in new window or tab >>Highly conductive ultrathin Co films by high-power impulse magnetron sputtering
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2018 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 112, no 4, article id 043103Article in journal (Refereed) Published
Abstract [en]

Ultrathin Co films deposited on SiO2 with conductivities exceeding that of Cu are demonstrated. Ionized deposition implemented by high-power impulse magnetron sputtering (HiPIMS) is shown to result in smooth films with large grains and low resistivities, namely, 14 mu Omega cm at a thickness of 40 nm, which is close to the bulk value of Co. Even at a thickness of only 6 nm, a resistivity of 35 mu Omega cm is obtained. The improved film quality is attributed to a higher nucleation density in the Co-ion dominated plasma in HiPIMS. In particular, the pulsed nature of the Co flux as well as shallow ion implantation of Co into SiO2 can increase the nucleation density. Adatom diffusion is further enhanced in the ionized process, resulting in a dense microstructure. These results are in contrast to Co deposited by conventional direct current magnetron sputtering where the conductivity is reduced due to smaller grains, voids, rougher interfaces, and Ar incorporation. The resistivity of the HiPIMS films is shown to be in accordance with models by Mayadas-Shatzkes and Sondheimer which consider grain-boundary and surface-scattering.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2018
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-340315 (URN)10.1063/1.5011109 (DOI)000423724300039 ()
Funder
Swedish Foundation for Strategic Research , SE13-0033Swedish Foundation for Strategic Research , RIF14-0053Swedish Research Council, C0514401
Available from: 2018-01-29 Created: 2018-01-29 Last updated: 2018-04-04Bibliographically approved
Jablonka, L., Kubart, T., Gustavsson, F., Descoins, M., Mangelinck, D., Zhang, S.-L. & Zhang, Z. (2018). Improving the morphological stability of nickel germanide by tantalum and tungsten additions. Applied Physics Letters, 112(10)
Open this publication in new window or tab >>Improving the morphological stability of nickel germanide by tantalum and tungsten additions
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2018 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 112, no 10Article in journal (Refereed) Published
Abstract [en]

To enhance the morphological stability of NiGe, a material of interest as a source drain-contact in Ge-based field effect transistors, Ta or W, is added as either an interlayer or a capping layer. The efficacy of this Ta or W addition is evaluated with pure NiGe as a reference. While interlayers increase the NiGe formation temperature, capping layers do not retard the NiGe formation. Regardless of the initial position of Ta or W, the morphological stability of NiGe against agglomeration can be improved by up to 100 °C. The improved thermal stability can be ascribed to an inhibited surface diffusion, owing to Ta or W being located on top of NiGe after annealing, as confirmed by means of transmission electron microscopy, Rutherford backscattering spectrometry, and atom probe tomography. The latter also shows a 0.3 €‰at. % solubility of Ta in NiGe at 450 °C, while no such incorporation of W is detectable.

National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-344676 (URN)10.1063/1.5019440 (DOI)
Funder
Swedish Foundation for Strategic Research , SE13- 0033Swedish Foundation for Strategic Research , RIF14- 0053Swedish Research Council, C0514401
Available from: 2018-03-07 Created: 2018-03-07 Last updated: 2018-03-08Bibliographically approved
Zhang, D., Solomon, P., Zhang, S.-L. & Zhang, Z. (2018). Low-frequency noise originating from the dynamic hydrogen ion reactivity at the solid/liquid interface of ion sensors. In: : . Paper presented at China Semiconductor Technology International Conference (CSTIC).
Open this publication in new window or tab >>Low-frequency noise originating from the dynamic hydrogen ion reactivity at the solid/liquid interface of ion sensors
2018 (English)Conference paper, Oral presentation only (Refereed)
Abstract [en]

Low-frequency noise (LFN) is of significant implications in ion sensing. As a primary component of LFN for ion sensing in electrolytes, the solid/liquid interfacial noise remains poorly explored especially regarding its relation to the surface binding/de-binding dynamic properties. In this talk, the solid/liquid interfacial noise will first be characterized by direct electrical measurements. It will then be correlated to the dynamic properties of surface protonation (i.e., hydrogen binding) and deprotonation (i.e., hydrogen de-binding) processes using an impedance spectroscopy. Finally we will provide insights into how detailed surface properties may affect the noise performance of an ion sensor operating in electrolytes.

National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-347580 (URN)
Conference
China Semiconductor Technology International Conference (CSTIC)
Available from: 2018-04-04 Created: 2018-04-04 Last updated: 2018-04-09
Zhang, D., Solomon, P., Zhang, S.-L. & Zhang, Z. (2017). An impedance model for the low-frequency noise originating from the dynamic hydrogen ion reactivity at the solid/liquid interface. Sensors and actuators. B, Chemical, 254, 363-369
Open this publication in new window or tab >>An impedance model for the low-frequency noise originating from the dynamic hydrogen ion reactivity at the solid/liquid interface
2017 (English)In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 254, p. 363-369Article in journal (Refereed) Published
Abstract [en]

Understanding the dynamics of hydrogen ion reactivity at the solid/liquid interface is of paramount importance for applications involving ion sensing in electrolytes. However, the correlation of this interfacial process to noise generation is poorly characterized. Here, the relationship is unveiled by characterizing the interfacial process with impedance spectroscopy assisted by a dedicated electrochemical impedance model. The model incorporates both thermodynamic and kinetic properties of the amphoteric hydrogen ion site-binding reactions with the surface OH groups. It further takes into consideration the distributed nature of the characteristic energy of the binding sites. The simulated impedance matches the experimental data better with an energy distribution of the kinetic parameters than with that of the thermodynamic ones. Since the potentiometric low-frequency noise (LFN) originating from the solid/liquid interface correlates excellently with the real part of its electrochemical impedance spectrum, this work establishes a method for evaluating sensing surface quality aimed at mitigating LFN.

National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-326714 (URN)10.1016/j.snb.2017.07.054 (DOI)000413308000045 ()
Funder
Swedish Research Council, VR 2014-5588Göran Gustafsson Foundation for promotion of scientific research at Uppala University and Royal Institute of Technology, GG 1459BCarl Tryggers foundation , CTS14-527Stiftelsen Olle Engkvist Byggmästare, 2016/39
Available from: 2017-07-26 Created: 2017-07-26 Last updated: 2018-04-11Bibliographically approved
Netzer, N. L., Must, I., Qiao, Y., Zhang, S.-L., Wang, Z. & Zhang, Z. (2017). Biomimetic supercontainers for size-selective electrochemical sensing of molecular ions. Scientific Reports, 7, Article ID 45786.
Open this publication in new window or tab >>Biomimetic supercontainers for size-selective electrochemical sensing of molecular ions
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2017 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, article id 45786Article in journal (Refereed) Published
Abstract [en]

New ionophores are essential for advancing the art of selective ion sensing. Metal-organic supercontainers (MOSCs), a new family of biomimetic coordination capsules designed using sulfonylcalix[4] arenes as container precursors, are known for their tunable molecular recognition capabilities towards an array of guests. Herein, we demonstrate the use of MOSCs as a new class of size-selective ionophores dedicated to electrochemical sensing of molecular ions. Specifically, a MOSC molecule with its cavities matching the size of methylene blue (MB+), a versatile organic molecule used for bio-recognition, was incorporated into a polymeric mixed-matrix membrane and used as an ion-selective electrode. This MOSC-incorporated electrode showed a near-Nernstian potentiometric response to MB+ in the nano-to micro-molar range. The exceptional size-selectivity was also evident through contrast studies. To demonstrate the practical utility of our approach, a simulated wastewater experiment was conducted using water from the Fyris River (Sweden). It not only showed a near-Nernstian response to MB+ but also revealed a possible method for potentiometric titration of the redox indicator. Our study thus represents a new paradigm for the rational design of ionophores that can rapidly and precisely monitor molecular ions relevant to environmental, biomedical, and other related areas.

Place, publisher, year, edition, pages
NATURE PUBLISHING GROUP, 2017
National Category
Chemical Sciences Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-321839 (URN)10.1038/srep45786 (DOI)000398960200001 ()28393841 (PubMedID)
Funder
Swedish Foundation for Strategic Research , SSF ICA 12-0047Swedish Research Council, VR 2014-5588Göran Gustafsson Foundation for Research in Natural Sciences and Medicine, GG 1459BCarl Tryggers foundation , CTS14-527
Available from: 2017-05-15 Created: 2017-05-15 Last updated: 2017-05-16Bibliographically approved
Zhang, D., Solomon, P., Zhang, S.-L. & Zhang, Z. (2017). Correlation of Low-Frequency Noise to the Dynamic Properties of the Sensing Surface in Electrolytes. ACS Sensors, 2(8), 1160-1166
Open this publication in new window or tab >>Correlation of Low-Frequency Noise to the Dynamic Properties of the Sensing Surface in Electrolytes
2017 (English)In: ACS Sensors, E-ISSN 2379-3694, Vol. 2, no 8, p. 1160-1166Article in journal (Refereed) Published
Abstract [en]

Low-frequency noise (LFN) is of significant implications in ion sensing. As a primary component of LFN for ion sensing in electrolytes, the solid/liquid interfacial noise remains poorly explored especially regarding its relation to the surface binding/debinding dynamic properties. Here, we employ impedance spectroscopy to systematically characterize this specific noise component for its correlation to the dynamic properties of surface protonation (i.e., hydrogen binding) and deprotonation (i.e., hydrogen debinding) processes. This correlation is facilitated by applying our recently developed interfacial impedance model to ultrathin TiO2 layers grown by means of atomic layer deposition (ALD) on a TiN metallic electrode. With an excellent fitting of the measured noise power density spectra by the model for the studied TiO2 layers, we are able to extract several characteristic dynamic parameters for the TiO2 sensing surface. The observed increase of noise with TiO2 ALD cycles can be well accounted for with an increased average binding site density. This study provides insights into how detailed surface properties may affect the noise performance of an ion sensor operating in electrolytes.

Keyword
impedance, ion-sensing, low frequency noise, site-binding model, solid/liquid interface
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-326716 (URN)10.1021/acssensors.7b00285 (DOI)000408702500011 ()28745041 (PubMedID)
Funder
Swedish Research Council, VR 2014-5588Göran Gustafsson Foundation for Research in Natural Sciences and Medicine, GG 1459BCarl Tryggers foundation , CTS14-527Stiftelsen Olle Engkvist Byggmästare, 2016/39Swedish Foundation for Strategic Research
Available from: 2017-07-26 Created: 2017-07-26 Last updated: 2017-12-11Bibliographically approved
Jablonka, L., Kubart, T., Primetzhofer, D., Abedin, A., Hellstrom, P.-E., Ostling, M., . . . Zhang, Z. (2017). Formation of nickel germanides from Ni layers with thickness below 10 nm. Journal of Vacuum Science & Technology B, 35(2), Article ID 020602.
Open this publication in new window or tab >>Formation of nickel germanides from Ni layers with thickness below 10 nm
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2017 (English)In: Journal of Vacuum Science & Technology B, ISSN 1071-1023, E-ISSN 1520-8567, Vol. 35, no 2, article id 020602Article in journal (Refereed) Published
Abstract [en]

The authors have studied the reaction between a Ge (100) substrate and thin layers of Ni ranging from 2 to 10 nm in thickness. The formation of metal-rich Ni5Ge3 was found to precede that of the monogermanide NiGe by means of real-time in situ x-ray diffraction during ramp-annealing and ex situ x-ray pole figure analyses for phase identification. The observed sequential growth of Ni5Ge3 and NiGe with such thin Ni layers is different from the previously reported simultaneous growth with thicker Ni layers. The phase transformation from Ni5Ge3 to NiGe was found to be nucleationcontrolled for Ni thicknesses < 5 nm, which is well supported by thermodynamic considerations. Specifically, the temperature for the NiGe formation increased with decreasing Ni (rather Ni5Ge3) thickness below 5 nm. In combination with sheet resistance measurement and microscopic surface inspection of samples annealed with a standard rapid thermal processing, the temperature range for achieving morphologically stable NiGe layers was identified for this standard annealing process. As expected, it was found to be strongly dependent on the initial Ni thickness.

Place, publisher, year, edition, pages
A V S AMER INST PHYSICS, 2017
National Category
Materials Engineering
Identifiers
urn:nbn:se:uu:diva-320866 (URN)10.1116/1.4975152 (DOI)000397858500029 ()
Funder
Swedish Foundation for Strategic Research , SE13-0033 RIF14-0053Swedish Research Council, C0514401
Available from: 2017-04-26 Created: 2017-04-26 Last updated: 2018-04-11Bibliographically approved
Wen, C., Zeng, S., Arstila, K., Sajavaara, T., Zhu, Y., Zhang, Z. & Zhang, S.-L. (2017). Generalized Noise Study of Solid-State Nanopores at Low Frequencies. ACS Sensors, 2(2), 300-307
Open this publication in new window or tab >>Generalized Noise Study of Solid-State Nanopores at Low Frequencies
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2017 (English)In: ACS Sensors, ISSN 2379-3694, Vol. 2, no 2, p. 300-307Article in journal (Refereed) Published
Abstract [en]

Nanopore technology has been extensively investigated for analysis of biomolecules, and a success story in this field concerns DNA sequencing using a nanopore chip featuring an array of hundreds of biological nanopores (BioNs). Solid-state nanopores (SSNs) have been explored to attain longer lifetime and higher integration density than what BioNs can offer, but SSNs are generally considered to generate higher noise whose origin remains to be confirmed. Here, we systematically study lowfrequency (including thermal and flicker) noise characteristics of SSNs measuring 7 to 200 nm in diameter drilled through a 20-nmthick SiNx membrane by focused ion milling. Both bulk and surface ionic currents in the nanopore are found to contribute to the flicker noise, with their respective contributions determined by salt concentration and pH in electrolytes as well as bias conditions. Increasing salt concentration at constant pH and voltage bias leads to increase in the bulk ionic current and noise therefrom. Changing pH at constant salt concentration and current bias results in variation of surface charge density, and hence alteration of surface ionic current and noise. In addition, the noise from Ag/AgCl electrodes can become predominant when the pore size is large and/or the salt concentration is high. Analysis of our comprehensive experimental results leads to the establishment of a generalized nanopore noise model. The model not only gives an excellent account of the experimental observations, but can also be used for evaluation of various noise components in much smaller nanopores currently not experimentally available.

Keyword
flicker noise, nanopore, electrical double layer, model, power spectrum density, low frequency range, Hooge’s theory
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-315230 (URN)10.1021/acssensors.6b00826 (DOI)000395047000017 ()
Funder
Swedish Research Council, 621-2014-6300Stiftelsen Olle Engkvist Byggmästare, 2016/39Swedish Foundation for Strategic Research
Note

Chenyu Wen and Shuangshuang Zeng contributed equally to this work.

Available from: 2017-02-10 Created: 2017-02-10 Last updated: 2017-04-21Bibliographically approved
Wen, C., Zhang, Z. & Zhang, S.-L. (2017). Physical Model for Rapid and Accurate Determination of Nanopore Size via Conductance Measurement. ACS SENSORS, 2(10), 1523-1530
Open this publication in new window or tab >>Physical Model for Rapid and Accurate Determination of Nanopore Size via Conductance Measurement
2017 (English)In: ACS SENSORS, ISSN 2379-3694, Vol. 2, no 10, p. 1523-1530Article in journal (Refereed) Published
Abstract [en]

Nanopores have been explored for various biochemical and nanoparticle analyses, primarily via characterizing the ionic current through the pores. At present, however, size determination for solid-state nanopores is experimentally tedious and theoretically unaccountable. Here, we establish a physical model by introducing an effective transport length, L (eff) that measures, for a symmetric nanopore, twice the distance from the center of the nanopore where the electric field is the highest to the point along the nanopore axis where the electric field falls to e-(1)of this maximum. By G = sigma(s0)/L-eff, a simple expression S-0=/(G, sigma, h, beta) is derived to algebraically correlate minimum nanopore cross-section area S (0)to nanopore conductance G, electrolyte conductivity a, and membrane thickness h with (3 to denote pore shape that is determined by the pore fabrication technique. The model agrees excellently with experimental results for nanopores in graphene, single-layer MoS2, and ultrathin SiNx films. The generality of the model is verified by applying it to micrometer-size pores.

Keyword
nanopores, physical model, effective transport length, algebraic solution, conductance measurement in electrolyte
National Category
Nano Technology
Identifiers
urn:nbn:se:uu:diva-340952 (URN)10.1021/acssensors.7b00576 (DOI)000414238600021 ()28974095 (PubMedID)
Funder
Swedish Research Council, 621-2014-6300
Available from: 2018-02-13 Created: 2018-02-13 Last updated: 2018-04-11Bibliographically approved
Makaraviciute, A., Xu, X., Nyholm, L. & Zhang, Z. (2017). Systematic approach to the development of microfabricated biosensors: relationship between the gold surface pretreatment and thiolated molecule binding. ACS Applied Materials and Interfaces, 9(31), 26610-26621
Open this publication in new window or tab >>Systematic approach to the development of microfabricated biosensors: relationship between the gold surface pretreatment and thiolated molecule binding
2017 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 9, no 31, p. 26610-26621Article in journal (Refereed) Published
Abstract [en]

Despite the increasing popularity of microfabricated biosensors due to advances in technologic and surface functionalization strategies, their successful implementation is partially inhibited by the lack of consistency in their analytical characteristics. One of the main causes for the discrepancies is the absence of a systematic and comprehensive approach to surface functionalization. In this article microfabricated gold electrodes aimed at biosensor development have been systematically characterized in terms of surface pretreatment, thiolated molecule binding, and reproducibility by means of X-ray photoelectron scattering (XPS) and cyclic voltammetry (CV). It has been shown that after SU-8 photolithography gold surfaces were markedly contaminated, which decreased the effective surface area and surface coverage of a model molecule mercaptohexanol (MCH). Three surface pretreatment methods compatible with microfabricated devices were compared. The investigated methods were (i) cyclic voltammetry in dilute H2SO4, (ii) gentle basic piranha followed by linear sweep voltammetry in dilute KOH, and (iii) oxygen plasma treatment followed by incubation in ethanol. It was shown that all three methods significantly decreased the contamination and increased MCH surface coverage. Most importantly, it was also revealed that surface pretreatments may induce structural changes to the gold surfaces. Accordingly, these alterations influence the characteristics of MCH functionalization.

National Category
Other Engineering and Technologies not elsewhere specified
Identifiers
urn:nbn:se:uu:diva-326715 (URN)10.1021/acsami.7b08581 (DOI)000407540400106 ()28726367 (PubMedID)
Funder
Swedish Foundation for Strategic Research , SSF ICA 12-0047, FFL15-0174Swedish Research Council, VR 2014-5588Carl Tryggers foundation
Available from: 2017-07-26 Created: 2017-07-26 Last updated: 2017-12-28Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0003-4317-9701

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