| 91. |
- Suyatin, Dmitry, et al.
(författare)
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Strong Schottky barrier reduction at Au-catalyst/GaAs-nanowire interfaces by electric dipole formation and Fermi-level unpinning
- 2014
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Ingår i: Nature Communications. - London : Springer Science and Business Media LLC. - 2041-1723. ; 5
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Tidskriftsartikel (refereegranskat)abstract
- Nanoscale contacts between metals and semiconductors are critical for further downscaling of electronic and optoelectronic devices. However, realizing nanocontacts poses significant challenges since conventional approaches to achieve ohmic contacts through Schottky barrier suppression are often inadequate. Here we report the realization and characterization of low n-type Schottky barriers (~0.35 eV) formed at epitaxial contacts between Au-In alloy catalytic particles and GaAs-nanowires. In comparison to previous studies, our detailed characterization, employing selective electrical contacts defined by high-precision electron beam lithography, reveals the barrier to occur directly and solely at the abrupt interface between the catalyst and nanowire. We attribute this lowest-to-date-reported Schottky barrier to a reduced density of pinning states (~1017 m−2) and the formation of an electric dipole layer at the epitaxial contacts. The insight into the physical mechanisms behind the observed low-energy Schottky barrier may guide future efforts to engineer abrupt nanoscale electrical contacts with tailored electrical properties.
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| 92. |
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| 93. |
- Suyatin, Dmitry, et al.
(författare)
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Sulfur passivation for ohmic contact formation to InAs nanowires
- 2007
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 18:10
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the formation of ohmic contacts to InAs nanowires by chemical etching and passivation of the contact areas in an ammonium polysulfide, (NH4)(2)S-x, water solution. The nanowires were exposed to different dilution levels of the (NH4)(2)Sx solution before contact metal evaporation. A process based on a highly diluted ( NH4)S-2(x) solution was found to be self-terminating, with minimal etching of the InAs. The stability of the contacts was investigated with electrical measurements as a function of storage time in vacuum and air.
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| 94. |
- Tønnesen, Siren, et al.
(författare)
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Brain Age Prediction Reveals Aberrant Brain White Matter in Schizophrenia and Bipolar Disorder : A Multisample Diffusion Tensor Imaging Study
- 2020
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Ingår i: Biological Psychiatry. - : Elsevier BV. - 2451-9022 .- 2451-9030. ; 5:12, s. 1095-1103
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Schizophrenia (SZ) and bipolar disorder (BD) share substantial neurodevelopmental components affecting brain maturation and architecture. This necessitates a dynamic lifespan perspective in which brain aberrations are inferred from deviations from expected lifespan trajectories. We applied machine learning to diffusion tensor imaging (DTI) indices of white matter structure and organization to estimate and compare brain age between patients with SZ, patients with BD, and healthy control (HC) subjects across 10 cohorts.METHODS: We trained 6 cross-validated models using different combinations of DTI data from 927 HC subjects (18-94 years of age) and applied the models to the test sets including 648 patients with SZ (18-66 years of age), 185 patients with BD (18-64 years of age), and 990 HC subjects (17-68 years of age), estimating the brain age for each participant. Group differences were assessed using linear models, accounting for age, sex, and scanner. A meta-analytic framework was applied to assess the heterogeneity and generalizability of the results.RESULTS: Tenfold cross-validation revealed high accuracy for all models. Compared with HC subjects, the model including all feature sets significantly overestimated the age of patients with SZ (Cohen's d = -0.29) and patients with BD (Cohen's d = 0.18), with similar effects for the other models. The meta-analysis converged on the same findings. Fractional anisotropy-based models showed larger group differences than the models based on other DTI-derived metrics.CONCLUSIONS: Brain age prediction based on DTI provides informative and robust proxies for brain white matter integrity. Our results further suggest that white matter aberrations in SZ and BD primarily consist of anatomically distributed deviations from expected lifespan trajectories that generalize across cohorts and scanners.
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| 95. |
- Whitlow, Harry J, et al.
(författare)
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Lithography of high spatial density biosensor structures with sub-100 nm spacing by MeV proton beam writing with minimal proximity effect
- 2004
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 15:1, s. 223-226
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Tidskriftsartikel (refereegranskat)abstract
- Metal electrode structures for biosensors with a high spatial density and similar to85 nm gaps have been produced using focused megaelectronvolt (MeV) proton beam writing of poly-(methyl methacrylate) positive resist combined with metal lift-off. The minimal proximity exposure and straight proton trajectories in (similar to100 nm) resist layers for focused MeV proton beam writing are strongly indicative that ultimate electrode gap widths approaching a few nanometres are achievable.
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| 96. |
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| 97. |
- Zakharov, Alexei, et al.
(författare)
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Quantative photoelectron spectromicroscopy for investigation of PMMA resist residues
- 2002
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Ingår i: 7th International Conference on Nanometer-Scale Science and Technology and 21st European Conference on Surface Science.
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Konferensbidrag (refereegranskat)abstract
- We show that photoelectron spectroscopy (PES) due to its surface sensitivity can be used as a straightforward method to quantify the PMMA resist residues which remain on SiO2 surfaces after electron beam exposure and resist development. The attenuation of the SiO2 valence band and Si2p photoelectrons has been measured by using a photoelectron microscope and it has been found that correctly exposed and developed PMMA resist leaves residues with an average thickness of about 0.7 nm. Higher exposure doses result in decrease of the film thickness, but still with residues of about 0.5 nm. The technique can be applied as a powerful tool for surface and interface quality control in technology of electronic devices
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| 98. |
- Zankovych, S, et al.
(författare)
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Nanoimprint-induced effects on electrical and optical properties of quantum well structures
- 2003
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Ingår i: Microelectronic Engineering (Proceedings of the 28th International Conference on Micro- and Nano-Engineering). - 0167-9317 .- 1873-5568. ; 67-8, s. 214-220
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Konferensbidrag (refereegranskat)abstract
- A study of optical and transport properties of semiconductor quantum well structures subjected to nanoimprint lithography (NIL), with its pressure and temperature cycles, has been undertaken to ascertain if this lithography technique induces detrimental changes in these properties of the active layers over a range of pressures and temperatures, typically used in this printing process. Ga0.47In0.53As-InP and GaAs-Al0.3Ga0.7As multiple quantum well samples were investigated. Luminescence and the photoluminescence excitation were recorded before and after printing. No impact upon the luminescence energy and intensity were detected. From the photoluminescence spectrum no evidence of induced strain was found. The magneto transport experiments yielded no evidence of deterioration of neither the mobility nor carrier concentration of a two-dimensional electron gas in a modulation-doped Ga0.25In0.75As/InP heterostructure. Results on samples subjected to the NIL process over a wide range of applied pressure and temperature are presented and discussed. (C) 2003 Elsevier Science B.V. All rights reserved.
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