Description: Pure Ag films were deposited on SiO2/Si with and without introduction of W0.7Ti0.3 barrier layers. The films were annealed in vacuum for 1 h at temperatures up to 650 °C. X-ray diffraction pole figure analysis was used to investigate the texture information in as-deposited and annealed films. After annealing, the {111} texture in Ag films increased; however, the degree of increase was significantly higher in Ag/W–Ti/SiO2. In Ag/SiO2 structures, the {200} tex...
Description: We have observed the distribution of electron trapping centers on distorted carbon nanotubes (CNTs) by a unique x-ray analysis technique that has both elemental and spatial selectivities. This technique involves the use of scanning probe microscopy (SPM) under synchrotron radiation excitation of the inner shell of carbon. The probe detects the Coulomb force that results from the relaxation of an electron bound to a defect site into the core hole state create...
Description: Previous analyses [ Z. Yan and J. Chen, J. Appl. Phys. 72, 1 (1992) ; J. Chen and Z. Yan, ibid., 84, 1791 (1998) ; Lin et al., Physica B 344, 147 (2004) ; Yang et al., ibid., 364, 33 (2005) ; Xia et al., ibid., 381, 246 (2006). ] of irreversibilities in magnetic refrigerators overlooked several important losses that could be dominant in a real active magnetic regenerative refrigerator (AMRR). No quantitative expressions have been provided yet to estimate the...
Description: Low temperature photoluminescence and reflectance measurements on epitaxially lifted-off (ELO) bulk GaAs and GaAs/AlGaAs multiple quantum wells (MQWs) bonded to Si and MgO substrates are reported. Photoluminescence measurements indicate no strain at room temperature for the ELO bulk GaAs film but show biaxial strain at 10 K. Si-bonded films undergo tensile strain, while films with MgO host substrates experience compressive strain. Reflectance measurements at...
Description: When the Kissinger method is used to investigate thin film growth kinetics, activation energies obtained are often significantly higher than those of Arrhenius plots based on isothermal studies. The reason for the higher activation energies is related to the sensitivity of the Kissinger analysis to nucleation effects. In fact, this often undesirable effect opens the possibility of studying nucleation barriers in a semiquantitative way. Furthermore, we show t...
Description: The LaNiO3−δ perovskite has been studied during its reoxygenation process at the reversible insulator-metal transition by spectroscopic ellipsometry for different pressures and temperatures conditions. First, it was demonstrated that the reoxygenation dynamics increases with both increasing pressure and temperature. Considering the temperature dependent experiments, two regimes of kinetics have been identified: a slow reoxygenation dynamics at low temperatur...
Description: Since the glassy alloys have structural homogeneity on a nanoscopic scale and wide supercooled liquid region, ΔTx (temperature interval between glass transition and crystallization), these materials are recognized as promising micro/nano-materials for nanomachines or micro electro-mechanical systems (MEMS). As one of the micro/nano components, the hard magnetic one is immensely desired. We systematically investigated the effect of metalloids composition in F...
Description: We investigate the charge and spin dynamics of optically injected currents in multiple quantum well structures using a hydrodynamic model. The dynamics is very complex even on time scales of the order of 1 ps due to the interplay of Coulomb forces, electron-hole drag effects, and nonlinearity of the equations of motion. Our analysis is based on a numerical approach employing an expansion of the calculated quantities in a Hermite–Gaussian basis. We calculate ...
Description: Exciton dissociation process at indium tin oxide (ITO)/copper phthalocyanine (CuPc) interface of ITO/CuPc(370 nm)/Al is studied by transient photovoltage method. A negative-to-positive change in the polarity of photovoltage upon pulsed laser irradiation is observed in CuPc thin film. The polarity change is regarded as a summation of the effect of exciton dissociation at ITO/CuPc interface (fast process) and that of free carrier separation by built-in field (...
Description: Electron accumulation at the oxidized surface of In- and N-polarity indium nitride is shown to exhibit no dependence on the growth conditions (varied from In- to N-rich), revealing the surface Fermi level to be pinned 1.4±0.1 eV above the valence band maximum for all cases. This is in contrast to the interpretation of recent multiple-field Hall effect measurements, which suggested almost an order of magnitude increase in the sheet density of the accumulation...
Description: Voltage-controlled negative resistance (VCNR) and unipolar resistive switching that can be used for memory applications can develop in the current-voltage (I-V) curves of metal-insulator-metal diodes. Electroluminescence is intimately connected with the occurrence of VCNR in I-V curves. The temperature dependence of VCNR and electroluminescence of Al–Al2O3–Au diodes with anodic Al2O3 thicknesses between 12 and 54 nm has been studied between 300 and 180 K. Th...
Description: Computer simulations are carried out to investigate the sensitivity of simultaneous determination of three electronic transport properties (carrier lifetime, carrier diffusivity, and front surface recombination velocity) of silicon wafers by modulated free carrier absorption (MFCA) via a multiparameter fitting procedure. The relative accuracy of the transport parameter determination by laterally resolved MFCA (LR-MFCA), in which the amplitude and phase are m...
Description: Time dependence of the electronic structure of an electron-beam (EB) irradiated C60 film (20–30 nm thick) has been examined using in situ high-resolution ultraviolet photoelectron spectroscopy. It is found that the electronic states of the C60 film have been changed continuously from an insulator (pristine C60 films) to a semiconductor and finally to a metal as EB-irradiation time increased. This can be explained by the increase in polymerization degree of a...
Description: The change in resistance of nanostructured metals with respect to an applied field is believed to be due to a change in carrier concentration and hence a linear variation of resistance with the surface charge is expected. In this article, we propose a different approach to explain the resistance variation based on a change in the effective thickness of the film due to a shift of the electron density profile resulting from the applied surface charge. The chan...
Description: The method to calculate the electrical resistance of a multilayered film consisting of any finite number of ferromagnetic and nonmagnetic layers for a given collinear magnetic configuration is proposed. The problem is solved for the geometry when the current flows perpendicular to the film plane. The method is based on the description of the resistance of a multilayered film by the differential equation for the current polarization which satisfies two bounda...
Description: Remotely doped In0.35Ga0.65As layers of different coverages 6, 9, 11, and 13 ML were grown by molecular beam epitaxy on (100) GaAs. Quantum dot (QD) nucleation was observed in situ by reflection high-energy electron diffraction at 8 ML growth of In0.35Ga0.65As, while for 6 ML, only two-dimensional (2D) growth was observed. Atomic force microscopy, low temperature photoluminescence, and Hall effect measurements confirmed this transition from 2D to three-dimen...
Description: Optical and dc resistivity measurements as well as x-ray spectroscopies have been performed on (Ga,Mn)N films containing Mn at up to 11 at. %. The results indicate that at higher Mn contents, the Fermi level is situated within extended states, while GaN host interband optical transitions are unaffected. The Mn state is confirmed to be 3d5, as in the case of lower Mn content films; however, the high Mn content merges the 3d levels into a band located just bel...
Description: The effects of SiO2 addition, in the range 0–3 at. %, on the high field electrical characteristics of positive temperature coefficient of resistance (PTC) thermistors have been characterized at several temperatures above the ferroelectric transition temperature TC. It was found that decreases in SiO2 content and increases in measurement temperature both decreased the field dependency of the current-voltage response. The electrical data were analyzed in terms...
Description: The aim of this article is to study the properties of the crystalline face centered cubic Ge1Sb2Te4 phase as a function of annealing and measuring temperature. This material is one of the stoichiometric members of the Ge:Sb:Te family, which is widely used in the phase change data storage and one candidate for multistate recording. The electrical properties of this material have been investigated using two independent methods, the four probe impedance and the...