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In this paper, the authors consider the processes that occur at the interfaces during nanowires (NWs) growth by the vapor→droplet liquid→solid mechanism (VLS), and how that leads to the faceting of the sidewall surface of the NWs. It is shown that faceting is possible only when the wetting scenario of the VLS growth of the NWs is accomplished due to the exit of the oblique closed‐packed faces to the sidewall surface of the NWs. Those oblique closed‐packed faces emerge at the crystallization front near the triple phase line. The faceting of the sidewall surface of the NWs can be controlled (i) by changing the contact angle of the catalyst droplet on the top of the NWs with the appropriate catalysts; (ii) by introducing the impurities into the gas phase, which decreases the free surface energy of the catalyst droplet; or (iii) by changing the temperature. [ABSTRACT FROM AUTHOR]

Silver nanowires (AgNW) mixed with nanocellulose nanowires (NCNW) are deposited in photolithgraphed gratings of varying depth. The nanocellulose onto which the AgNWs are mixed is of varying length. It is found that the recirculation flow is larger when the length of the NCNW is longer, and the grating used is deeper. The electrical properties of the resulting quasi‐1D electrode is tested both before it is transferred into the nanocellulose paper and after, and it is observed that it retains the same order of magnitude for the conductivities as the 0.3 and 0.2%wt concentrations for the bare AgNW. This is attributed to the use of the NCNW, at high concentrations. Using the NCNW in the mixtures allows for the AgNW to be transferred from the gratings to any substrate. Using the NC paper allows to obtain a nearly transparent or translucent nearly 1D electrode, where 1D refers to the fact the length of the obtained electrode far exceeds its width. [ABSTRACT FROM AUTHOR]

The ICPS series traditionally encompasses a variety of topics spanning device physics, quantum technologies, spin physics, wide bandgap materials, light-matter interactions, and other branches of materials science, physics and engineering. It is my pleasure to write this preface to the Special Section in the May 2023 issue of I pss(b) i , dedicated to the collection of selected works presented during the 35 SP th sp International Conference on Physics of Semiconductors (ICPS) held in Sydney, Australia in 2022. As we are preparing for the next meeting in Ottawa, Canada, the collection of papers should inspire our junior colleagues, that not only semiconductor physics is here to stay, but in fact, it is a multi-disciplinary and burgeoning field of research. [Extracted from the article]

The possibility of combining both optical transparency and high electrical conductivity in the same material makes transparent conducting oxides one of the most sought after materials in transparent electronics. This paper presents the investigations done on the conductivity mechanisms of n-type transparent conducting silver indium oxide thin films in different temperature ranges varying from 6 to 333 K. X-ray diffraction indicates the films to be amorphous, and the morphology of the films from scanning electron microscopy and atomic force microscopy shows agglomerations with average particle size ∼30 nm. X-ray photoelectron spectroscopy and energy-dispersive analysis of X-rays establish the films to be nearly stoichiometric with In/Ag at.% ratio in the range 1.1-1.2. The transmittance percentage obtained from optical transmittance and absorbance spectra is moderately high and the bandgap energy of the thin films is ∼3.5 eV. Transport parameters, such as carrier mobility ∼103 cm2/V s and carrier concentration ∼1018/cm3, are elucidated from Hall and thermopower data. [ABSTRACT FROM AUTHOR]

A physically valid parametrization of the crystal-field (CF) Hamiltonian HCF has to reproduce not only the energy of Stark sublevels but also the multipolar structure of the central ion surroundings. The square of the second moment $\sigma {}^{2} {\left( {\left| {J} \right\rangle } \right)}$ of $\left| {J} \right\rangle $ electronic state CF splitting must be a superposition of squares of the second moments of the partial splittings produced separately by the individual multipoles: $\sigma {}^{2} {\left( {\left| {J} \right\rangle } \right)} = \sum\nolimits_{k} {\sigma _{k}^{2} } {\left( {\left| {J} \right\rangle } \right)} = {\left[ {1/(2J + 1)} \right]}\sum\nolimits_{k} {A_{k}^{2} {\left( {\left| {J} \right\rangle } \right)}} S_{k}^{2} $, where $A_{k} {\left( {\left| {J} \right\rangle } \right)}$ represents the modulus of a k-rank multipole of the central ion electronic eigenstate $\left| {J} \right\rangle $, whereas $S_{k} = {\left( {[1/(2k + 1)]\sum\nolimits_{q} {\left| {B_{kq} } \right|^{2} } } \right)}^{1/2} $ is the k-rank CF strength. The relationship between $\sigma {}^{2} {\left( {\left| {J} \right\rangle } \right)}$ known from experiment and $S_{k}^{2} $ obtained from fitting procedure allows us to verify whether the parametrization is physically valid. It is demonstrated by several examples of CF splittings of electronic states of trivalent lanthanide ions in different crystal matrices. The approach is confined only to the states with good quantum numbers J. Nevertheless, by finding such states in any analyzed spectrum, the method can provide the actual multipole characteristics of HCF, and plays the role of a preparametrization. In general, the stepwise fitting procedure can never lead to parametrizations with a correct multipolar structure due to the limitation of the initial eigenfunctions. In consequence, the pertinent crystal-field parameters (CFPs) are burdened with a methodical inherent fault. The loss of physical meaning of fitted CFPs, its source and consequences, constitute the main theme of the paper. [ABSTRACT FROM AUTHOR]

In this paper, a modified transfer matrix method is proposed to solve the transverse vibration bandgaps (BGs) in phononic crystal (PC) Euler beams on a Winkler foundation. An equivalent critical frequency is introduced to facilitate the calculation of the end frequency of the first BG. The band structures of a lead-steel PC Euler beam either on a Winkler foundation or not show that the existence of a foundation has a significant influence on the distribution of BGs. A new BG that starts at 0 Hz appears. Additional results demonstrate that a very narrow passband could exist between the first two BGs. This study is aimed at searching for large BGs, especially at low frequencies. [ABSTRACT FROM AUTHOR]

Optical spectroscopy provides non-invasive, in-situ, real time (and sometimes femtosecond time-resolved) probing of surfaces and buried interfaces over macroscopic areas, features that complement atomic-scale probes such as scanning-tunneling microscopy. Since its inception back in 1995, the International Conference on Optics of Surfaces and Interfaces (OSI) has included cutting-edge experimental and theoretical work in ellipsometry, reflectance-anisotropy spectroscopy, magneto-optics, Raman scattering and surface second-harmonic generation. The seven peer-reviewed papers in this special section of I physica status solidi (b) i represent examples of both traditional and emerging OSI themes, as discussed at the 13 SP th sp International Conference on Optics of Surfaces and Interfaces (OSI-13), and include both theoretical and experimental work. [Extracted from the article]

Epitaxial growth of polar GaN is frequently made on AlN/Si substrates that contain a large density of threading dislocations induced by the mismatch of their lattice parameters and thermal expansion coefficients. In this paper, the structural and electrical properties of surface and extended defects found in 220 nm {0001} AlN films grown epitaxially on {111} oriented Si substrate by metalorganic chemical vapor deposition are characterized. Three types of surface depressions are recognized by atomic force microscopy (AFM) that correspond to V‐defects and their clusters and individual threading dislocations. Transmission electron microscopy studies prove that all V‐defects are attached to threading screw or mixed‐type threading dislocations. The electrical activity of the defects in the AlN film is assessed by measuring the electron beam induced current (EBIC) across Au/Ni/AlN Schottky barrier. The largest drop of EBIC compared to defect‐free regions is observed at clusters of V‐defects, which have a low density of (2.4 ± 0.4) × 107 cm−2. Only a very weak drop of EBIC is found at isolated threading dislocations, which have much higher density compared to clusters of V‐defects. Considering the defects studied, the electrical properties of AlN films are primarily affected by threading dislocations, despite the relatively weak recombination efficiency of individual dislocations. [ABSTRACT FROM AUTHOR]

This paper presents a polarization‐insensitive and ultra‐broadband metamaterial absorber (UMMA), which has higher absorption throughout the whole X‐band. The UMMA unit cell consists of a metal film and a multilayer‐cross‐cone structure separated by a dielectric layer. The calculation result shows that the UMMA's absorptivity is greater than 96% in the entire X‐band (8–12 GHz) and the UMMA is polarization‐insensitive for normal incident wave. Moreover, the absorption rate is also more than 80% in X‐band when the incident angle is less than 56° for TE polarization wave. The electric field, magnetic field, and surface current distribution of the UMMA are analyzed to study its absorption mechanism. The influences of different key structural parameters on the absorber are also discussed, including the arm length and arm width of the bottom and top of the cross‐cone structure and the number of layers of the cross metal, consequently, a set of optimized design parameters is obtained. The proposed UMMA has a higher absorption rate in the entire X‐band, the UMMA can be used in electromagnetic stealth, electromagnetic shielding, secret detection and so on. [ABSTRACT FROM AUTHOR]

Learning by human beings is achieved by changing the synaptic weights of a neural network in the brain. Low frequency stimulation temporarily increases a synaptic weight, which then decreases to the initial low state in the interval after each stimulation. Conversely, high frequency stimulation keeps a synaptic weight at an elevated level, even after the stimulation ends. These phenomena are termed short‐term plasticity (STP) and long‐term potentiation (LTP), respectively. These functions have been emulated by various nonvolatile devices, with the aim of developing hardware‐based artificial intelligent (AI) systems. In order to use the functions in actual AI systems with other conventional devices, control of the operating characteristics, such as matching a decay constant in STP, is indispensable. This paper reports an electrochemical method for controlling the characteristics of time‐dependent neuromorphic operations of molecular gap atomic switches. Pre‐doping of Ag+ cations into an ionic transfer layer (Ta2O5) changes the amount of shift in an electrochemical potential in the time‐dependent operation, which drastically improves the decaying characteristics in STP mode. [ABSTRACT FROM AUTHOR]

In this paper, the effects of the intense laser field (ILF) and position dependent mass (PDM) on the electronic structure in a Gaussian quantum well are theoretically deduced by using the diagonalization method for obtaining energy levels and corresponding wave functions. We find that, in the case of narrow PDM distribution, the dependence of the energy levels on the effective length of the electron mass distribution becomes more apparent, and the evolution of the dressed mass with ILF is significant. Given this feature, it is more meaningful to take into consideration the PDM of the electron in the low dimensional semiconductor heterostructures under the ILF. [ABSTRACT FROM AUTHOR]

This paper is devoted to a peculiar branch of surface electromagnetic waves, belonging to the visible spectral range. Contrary to the well known surface waves, supported by the sharp boundary of solid plasma in metals and semiconductors, the waves discussed here are shown a gradient interface of non‐conducting gradient dielectric without free carriers. The subsurface layer of this dielectric is characterized by the gradual decrease of dielectric permittivity ϵ(z) in the direction z, normal to the boundary z = 0, saturated in the depth of medium. Unlike the traditional condition ϵ<0, the field's localization near the interface of the dielectric is determined by another condition: grad ϵ<0, meanwhile ϵ<0. Spectra of surface modes are determined by the non‐local dispersion, stipulated by the spatial distribution ϵ(z). The spatial structure of surface wave fields is examined by means of two different exactly solvable models ϵ(z). The broadband and wide band spectral ranges of visible surface waves illustrating the sensitivity of their spectra to the fine details of distribution ϵ(z), presented by these models, are considered. [ABSTRACT FROM AUTHOR]

The physics behind nonlinear propagation of picosecond pulses in micro‐ and nano‐wire single mode waveguides either grown by chemical vapor deposition or etched into semiconductor microresonators are reviewed. If operated in the strong coupling regime exciton‐polaritons form in those wires and a highly nonlinear platform is established interfacing optical, condensed matter, quantum, and statistical physics. A theory of the exciton‐polariton pulse compression, pulse breaking, and emission of the backward Cherenkov radiation have been developed. This highly nonlinear dynamics is associated with the relaxation of the exciton‐polariton spectrum down to low momenta, mediated solely by the exciton–exciton scattering. Such nonlinearity‐enhanced thermalization results in a phase transition from propagating exciton‐polariton pulses toward the formation of a non‐equilibrium polariton condensate in the microwire system. The paper describes the physics behind nonlinear propagation of picosecond pulses in semiconductor microwires operating in the strong coupling regime. This includes a theory of the exciton‐polariton pulse compression, formation of solitary waves, and pulse breaking. The authors show the phase transitions of polariton wave packets toward bright solitons and then to standing waves polariton condensate, mediated by nonlinear polariton interactions. [ABSTRACT FROM AUTHOR]

In this paper, results on the optical properties and carrier dynamics in inorganic and hybrid inorganic/organic semiconductor nanowire structures based on the ZnO and GaN material systems, obtained by the involved groups in the last years, are reviewed. First, the recombination dynamics in 3D GaN‐based microrod LED structures is analyzed and discussed. In particular, the dynamics at high excitation densities close to the damage threshold of the material is studied. This is followed by a discussion of the carrier dynamics in nanowire structures functionalized with colloidal CdSe quantum dots (QDs) or carbon nanoparticles (C‐Dots). Here, the nanoparticles allow for light absorption at photon energies below the bandgap of the semiconductor nanowire, and subsequent electron tunneling couples the electronic systems of the nanoparticles and the nanowires (NWs). Finally, the fabrication of nanowire/polymer core–shell structures is demonstrated and the electrical properties of n‐nanowire/p‐polymer hybrid junctions are studied. This article highlights the recombination dynamics in 3D GaN‐based microrod light‐emitting diodes at high excitation densities close to the damage threshold. Furthermore, the carrier dynamics in hybrid structures like ZnO nanowires functionalized with colloidal CdSe quantum dots or carbon nanoparticles (C‐Dots) is elucidated and finally, the fabrication of nanowire/polymer core–shell structures and the electrical properties of n‐nanowire/p‐polymer hybrid junctions are presented. [ABSTRACT FROM AUTHOR]