Further resolution enhancement of high-sensitivity laser scanning photothermal microscopy applied to mouse endogenous
Photothermalmicroscopy has intrinsically super resolution capability due to the bilinear dependence of signal intensity of pump and probe. In the present paper, we have made further resolution improvement of high-sensitivity laser scanningphotothermalmicroscopy by applying non-linear detection. By this, the new method has the following advantages: (1) super resolution with 61% and 42% enhancement from the diffraction limit values of the probe and pump wavelengths, respectively, by a second-order non-linear scheme, (2) compact light source using inexpensive conventionaldiode lasers, (3) wide applicability to nonfluorescent ...
Source: Journal of Applied Physics - December 2, 2016 Category: Physics Authors: Kazuaki Nakata, Hiromichi Tsurui and Takayoshi Kobayashi Source Type: research
Charge transfer at organic-inorganic interfaces —Indoline layers on semiconductor substrates
We studied theelectron transfer from excitons in adsorbed indoline dye layers across the organic-inorganicinterface. The hybrids consist of indoline derivatives on the one hand and different inorganic substrates (TiO2,ZnO, SiO2(0001), fusedsilica) on the other. We reveal theelectron transfer times from excitons in dye layers to the organic-inorganicinterface by analyzing thephotoluminescence transients of the dye layers after femtosecond excitation and applying kinetic model calculations. A correlation between the transfer times and four parameters have been found: (i) the number of anchoring groups, (ii) the distance betw...
Source: Journal of Applied Physics - December 2, 2016 Category: Physics Authors: I. Meyenburg, J. Falgenhauer, N. W. Rosemann, S. Chatterjee, D. Schlettwein and W. Heimbrodt Source Type: research
Polarization states and dielectric responses of elastically clamped ferroelectric nanocrystals
Polarization states and physicalproperties of ferroelectrics depend on the mechanical boundary conditions due to electrostrictive coupling between electricpolarization and lattice strains. Here, we describe theoretically both equilibrium thermodynamic states and electric permittivities of ferroelectricnanocrystals subjected to theelastic three-dimensional (3D) clamping by a surroundingdielectric material. The problem is solved by the minimization of a special thermodynamic potential that describes the case of an ellipsoidal ferroelectricinclusion embedded into a linearelastic matrix. Numerical calculations are performed fo...
Source: Journal of Applied Physics - December 2, 2016 Category: Physics Authors: A. V. Azovtsev and N. A. Pertsev Source Type: research
Limits for the graphene on ferroelectric domain wall p-n-junction rectifier for different regimes of current
Here, we present the theory of the conductivity of a pn junction (pnJ) in agraphene channel, placed on aferroelectric substrate, caused by theferroelectricdomain wall for the case of the arbitrary current regime: fromballistic to diffusive one. We calculated the ratio of the pnJ conductions for opposite polarities of voltages, applied to source and drainelectrodes of the channel,G+total/G−total, as a function ofgraphene channel lengthL, electron mean free path λ, andferroelectric substratepermittivityε33f. We have demonstrated that the small values ofG+total/G−total (0.1 and smaller), which correspond to the efficien...
Source: Journal of Applied Physics - December 2, 2016 Category: Physics Authors: Maksym V. Strikha and Anna N. Morozovska Source Type: research
The influence of laser ablation plume at different laser incidence angle on the impulse coupling coefficient with metal target
A calibrated pendulum measuring device and a dimensionless analysis method were used to measure the impulse coupling coefficient at different laser intensities withaluminum, steel, andiron targets. The experiment was performed with a pulsed laser with the wavelength of 1.06μm and the pulse duration of 7 ns. The experimental measurements of the variation of the impulse coupling coefficient versus the laser energy density agree with thetheoretical prediction, and the optimum laser energy density correlated with the maximum impulse coupling coefficient corresponding to thetheoretical predictions. The impulse coupling coeffic...
Source: Journal of Applied Physics - December 2, 2016 Category: Physics Authors: Xiong-Tao Zhao, Feng Tang, Bing Han and Xiao-Wu Ni Source Type: research
Migration processes of the As interstitial in GaAs
Thermal migration processes of the Asinterstitial inGaAs were investigated using density-functionaltheory and the local-density approximation for exchange and correlation. The lowest-energy processes were found to involve the −1, 0, and +1 charge states, and to produce migration along ⟨110⟩-type directions. In the −1 and 0 charge states, migration proceeds via hops betweensplit-interstitial stable configurations at bulk As sites throughbridging saddle-point configurations in which theinterstitial atom is equidistant from two adjacent bulk As sites. In the +1 charge state, the roles of these two configurations are a...
Source: Journal of Applied Physics - December 2, 2016 Category: Physics Authors: A. F. Wright and N. A. Modine Source Type: research
Continuum mechanics at the atomic scale: Insights into non-adhesive contacts using molecular dynamics simulations
Classicalmolecular dynamics (MD) simulations were performed to study non-adhesive contact at the atomic scale. Starting from the case of Hertzian contact, it was found that the reducedYoung's modulusE* for shallow indentations scales as a function of, both, the indentation depth and the contact radius. Furthermore, the contact of two representativerough surfaces was investigated: one multi-asperity, Greenwood-Williamson-type (GW-type) rough surface — where asperities were approximated as spherical caps — and a comparable randomly rough one. The results of theMD simulations were in agreement for both representa...
Source: Journal of Applied Physics - December 1, 2016 Category: Physics Authors: Soheil Solhjoo and Antonis I. Vakis Source Type: research
Charged vacancy diffusion in chromium oxide crystal: DFT and DFT+U predictions
In this work, we computationally studied the latticediffusion through the ion-vacancy exchange mechanism in α-Cr2O3 crystal using the first-principlesdensity functional theory(DFT) and DFT+U calculation methods. For both O and Crvacancies, we have identified four elementarydiffusion paths in α-Cr2O3 crystal. Our DFT+U calculations predict that the Ovacancy with charge +2 (VO2+) is stable when Fermi energy is near to valence band maximum, whereas the Crvacancy with charge −3 (VCr3−) is stable when Fermi energy is close to conduction band minimum. Moreover, the DFT+U calculations predict that the migration energy forVO...
Source: Journal of Applied Physics - December 1, 2016 Category: Physics Authors: Corinne Gray, Yinkai Lei and Guofeng Wang Source Type: research
Flow units perspective on elastic recovery under sharp contact loading in metallic glasses
The obscure nature ofglass physics has led to develop various correlations between different parameters andproperties ofmetallic glasses. Despite these correlations, the clear picture ofplastic deformation is still lacking. We have measured elastic recovery inmetallic glasses by indentation, and found the elastic recovery correlate with differentproperties and parameters ofmetallic glasses. All these observations can be quite well explained with flow unit model which could provide clearer picture on theplastic deformations and nature of themetallic glasses. (Source: Journal of Applied Physics)
Source: Journal of Applied Physics - December 1, 2016 Category: Physics Authors: K. Shahzad, A. Gulzar and W. H. Wang Source Type: research
Simultaneous ohmic contacts to p- and n-type 4H-SiC by phase segregation annealing of co-sputtered Pt-Ti
A new concept, Phase Segregation Annealing (PSA), was investigated for implementing simultaneousohmic contacts(SOCs) top- andn-type 4H-SiC. Test structures with selected ratio compositions of co-sputtered Pt:Ti contacts were fabricated inp-type 4H-SiC epitaxial layers having aluminum acceptor concentrations, Na = 2 × 1019, 7 × 1019, and 2.5 × 1020 cm−3, and a nitrogendopedn-type epitaxial layer having donor concentration, Nd = 7 × 1018 cm−3. The ratios of the co-sputtered Pt-Timetallization were 80:20, 50:50, and 30:70 at. %. After rapid thermal annealing (RTA) ranging between 800 an...
Source: Journal of Applied Physics - December 1, 2016 Category: Physics Authors: R. S. Okojie and D. Lukco Source Type: research
Analysis of the PEDOT:PSS/Si nanowire hybrid solar cell with a tail state model
In this paper, the electrical properties of the poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS)/siliconnanowirehybridsolar cell have been analyzed and an optimized structure is proposed. In addition, the planar PEDOT:PSS/c-Sihybridsolar cell is also modeled for comparison. We first developed a simulation software which is capable of modeling organic/inorganichybridsolar cells by including Gaussian shape density of states into Poisson and drift-diffusion solver to present the tail states and trap states in theorganic material. Therefore, the model can handle carrier transport, generation, and recombinat...
Source: Journal of Applied Physics - December 1, 2016 Category: Physics Authors: Kuan-Ying Ho, Chi-Kang Li, Hong-Jhang Syu, Yi Lai, Ching-Fuh Lin and Yuh-Renn Wu Source Type: research
Exciton delocalization incorporated drift-diffusion model for bulk-heterojunction organic solar cells
Modeling thecharge-generation process is highly important to understand device physics and optimize power conversion efficiency of bulk-heterojunction organicsolar cells (OSCs). Free carriers aregenerated by both ultrafastexciton delocalization and slowexcitondiffusion anddissociation at the heterojunctioninterface. In this work, we developed a systematic numerical simulation to describe thecharge-generation process by a modified drift-diffusion model. The transport, recombination, and collection of free carriers are incorporated to fully capture the device response. The theoretical results match well with the state-of-the...
Source: Journal of Applied Physics - December 1, 2016 Category: Physics Authors: Zi Shuai Wang, Wei E. I. Sha and Wallace C. H. Choy Source Type: research
Experimental and theoretical investigation of Cr1-xScxN solid solutions for thermoelectrics
The ScN- and CrN-based transition-metal nitrides have recently emerged as a novel and unexpected class of materials forthermoelectrics. These materials constitute well-defined model systems for investigating mixing thermodynamics, phase stability, and band structure aiming for property tailoring. Here, we demonstrate an approach to tailor theirthermoelectric properties bysolid solutions. The trends in mixing thermodynamics and densities-of-states (DOS) of rocksalt-Cr1-xScxNsolid solutions (0 ≤ x ≤ 1) are investigated by first-principles calculations, and Cr1-xScxNthin films are synthesized by magnetron sputter...
Source: Journal of Applied Physics - December 1, 2016 Category: Physics Authors: Sit Kerdsongpanya, Bo Sun, Fredrik Eriksson, Jens Jensen, Jun Lu, Yee Kan Koh, Ngo Van Nong, Benjamin Balke, Bj örn Alling and Per Eklund Source Type: research
In situ analysis of post-annealing effect on Sn-doped indium oxide films
Oxygen post-annealing effects on tin (Sn)doped indium oxide (ITO) film are investigated with various analytical tools as a function of temperature, includingin situXRD, ambient pressureXPS (AP-XPS), and Hall measurement. As the annealing temperature increases up to 200 °C under the oxygen pressure of 100 mTorr, thein situXRD shows the evidence ofcrystallization of the film while the AP-XPS reveals the formation of oxygenvacancy and Sn4+ states on surface. In addition, themobility of ITO thin film is increased as the post-annealing temperature increases, supporting the results of bothin situXRD and AP-XPS. The results o...
Source: Journal of Applied Physics - November 30, 2016 Category: Physics Authors: Hojoon Lim, Hyeok-Jun Yang, Ji Woong Kim, Jong-Seung Bae, Jin-Woo Kim, Beomgyun Jeong, Ethan Crumlin, Sungkyun Park and Bongjin Simon Mun Source Type: research
Observation of in situ oxidation dynamics of vanadium thin film with ambient pressure X-ray photoemission spectroscopy
The evolution of oxidation/reduction states ofvanadium oxidethin film was monitoredin situ as a function of oxygen pressure andtemperature via ambient pressure X-ray photoemission spectroscopy. Spectra analysis showed that VO2 can begrown at a relatively low temperature, T ∼ 523 K, and that V2O5 oxide develops rapidly at elevated oxygen pressure. Raman spectroscopy was applied to confirm the formation of VO2 oxide inside of thefilm. In addition, thetemperature-dependentresistivitymeasurement on thegrownthin film, e.g., 20 nm exhibited a desirable metal-insulator transition of VO2 with aresistivity change of ∼...
Source: Journal of Applied Physics - November 30, 2016 Category: Physics Authors: Geonhwa Kim, Joonseok Yoon, Hyukjun Yang, Hojoon Lim, Hyungcheol Lee, Changkil Jeong, Hyungjoong Yun, Beomgyun Jeong, Ethan Crumlin, Jouhahn Lee, Jaeyoung Lee, Honglyoul Ju and Bongjin Simon Mun Source Type: research
