79 research outputs found
Evidence for a charge Kondo effect in Pb(1-x)Tl(x)Te from measurements of thermoelectric power
We report measurements of the thermoelectric power (TEP) for a series of
Pb(1-x)Tl(x)Te crystals with x = 0.0 to 1.3%. Although the TEP is very large
for x = 0.0, using a single band analysis based on older work for dilute
magnetic alloys we do find evidence for a Kondo contribution of 11 - 18 uV/K.
This analysis suggests that Tk is ~ 50 - 70 K, a factor 10 higher than
previously thought.Comment: 4 pages, 3 figure
Особенности влияния условий роста на структурные и оптические свойства пленок Zn0.9Cd0.1O
The influence of the magnetron power and the gas ratio Ar/O2 on the microstructure and the optical properties of Zn0.9Cd0.1O films is studied. The films were deposited with the use of the dc magnetron sputtering technique at a temperature of 250 ◦C. Atomic force microscopy (AFM) and X-ray diffraction (XRD) researches of a surface morphology demonstrated a strong influence of deposition procedure parameters on the film microstructure. The XRD analysis revealed that all grown films were polycrystalline and single-phase. The increase of the gas ratio Ar/O2 was found to be beneficial for the crystalline structure of Zn0.9Cd0.1O ternary alloys. Peculiarities of the control over the band gap and the surface morphology for Zn0.9Cd0.1O ternary alloys by varying the growth parameters are discussed.Дослiджено вплив потужностi магнетрона i спiввiдношення тискiв робочих газiв Ar/O2 на мiкроструктуру та оптичнi властивостi плiвок Zn0.9Cd0.1O. Плiвки осаджено методом магнетронного розпилювання на постiйному струмi при температурi пiдкладки 250 C. Дослiдження морфологiї поверхнi, здійснені за допомогою атомно-силової мiкроскопiї (АСМ), i рентгено-фазовий аналiз (РФА) виявили сильний вплив технологічних параметрiв осадження на мiкроструктуру плiвок. РФА аналiз показав, що всi вирощенi плiвки є полiкристалiчними i однофазними. Встановлено, що зростання парцiального тиску аргону в газовiй сумiшi Ar/O2 сприятливо впливає на кристалічну структуру твердих розчинiв Zn0.9Cd0.1O. Обговорено особливостi контролю ширини забороненої зони та морфологiї поверхнi твердих розчинiв Zn0.9Cd0.1O шляхом змiни параметрiв вирощування.В работе исследовано влияние мощности магнетрона и соотношения давлений рабочих газов Ar/O2 на микроструктуру и оптические свойства пленок Zn0.9Cd0.1O. Пленки осаждены методом магнетронного распыления на постоянном токе при температуре подложки 250 C. Исследования морфологии поверхности, проведенные с помощью атомно-силовой микроскопии (АСМ), и рентгенофазовый анализ (РФА) выявили сильное влияние технологических параметров роста на микроструктуру пленок. РФА анализ показал, что все выращенные пленки являются поликристаллическими и однофазными. Было установлено, что рост парциального давления аргона в газовой смеси Ar/O2 благоприятно влияет на кристаллическую структуру твердых растворов Zn0;9Cd0;1O. Обсуждены особенности контроля ширины запрещенной зоны и морфологи поверхности твердых растворов Zn0;9Cd0;1O путем изменения параметров осаждени
Optical and structural studies of phase transformations and composition fluctuations at annealing of Zn₁₋xCdxO films grown by dc magnetron sputtering
Ternary Zn₁₋xCdxO (x < 0.12) alloy crystalline films with highly preferred
orientation (002) have been successfully deposited on sapphire c-Al₂O₃ substrates using
the direct current (dc) reactive magnetron sputtering technique and annealed at
temperature 600 °C in air. The structural and optical properties of Zn₁₋xCdxO thin films
were systematically studied using X-ray photoelectron spectroscopy (XPS), X-ray
diffraction (XRD), micro-Raman and photoluminescent (PL) spectroscopy. XPS
measurements clearly confirmed Cd incorporation into ZnO lattice. XRD data revealed
that the growth of wurtzite Zn₁₋xCdxO films occurs preferentially in the (002) direction.
Also, when the Cd content is increased, the XRD peaks shift towards smaller angles and
the full width at half-maximum of the lines increases. When the Cd content increases,
LO A1 ( Zn₁₋CdxO )-like Raman modes show composition dependent frequency decrease
and asymmetrical broadening. The near band-edge PL emission at room temperature
shifts gradually to lower energies as the Cd content increases and reaches 2.68 eV for the
highest Cd content (x = 0.12). The analysis of NBE band emission and Raman LO A1 ( Zn₁₋xCdxO ) mode shows that at a higher Cd content the coexistence of
Zn₁₋xCdxO areas with different concentrations of Cd inside the same film occurs. The
presence of CdO in annealed Zn₁₋xCdxO films with the higher Cd content was
confirmed by Raman spectra of cubic CdO nanoinclusions. The XRD data also revealed
phase segregation of cubic CdO in annealed Zn₁₋xCdxO films (Tann = 600 °C) for
x ≥ 0.013
Phase Field Modeling of the Solid Solutions
The analysis of spinodal decomposition in the ternary alloy was carried out by means of the nonlinear Cahn-Hilliard equation. Interaction parameter as a function of composition x was provided by valence force field simulations and was used in this analysis. The morphological patterns for the ternary alloys with different Cd content (x=5, 10, 50%) were experimentally obtained using the semi-implicit Fourier-spectral method. The simulated microstructure evolution demonstrates that the microstructure having a form of bicontinuous worm-like network is evolved with the progress of aging. An effect of the phase-field mobility and the gradient energy on the microstructure evolution of the alloys is discussed. It was found that the higher driving force for the decomposition in the higher Cd content film results in a higher decomposition rate revealed by the simulations. The temporal evolution of the simulated microstructure is in good agreement with experimental results, which have been obtained for this solid solution
Trends in the kinetic and magnetic properties of Pb0.8Sn0.2Te single crystals of high structural perfection
Light Flux Effect on the Electron Gas Dimension
The suggested spatial-energy model for electron spectrum of layered InSe semiconductor explains the magnetoresistance behaviour in the case of optical excitation, physical nature of rapid and slow photoconduction relaxations and absence of two-dimensional excitons (not surface)
Copyright: Elsevier
The local features of light emission from ZnO microrods were studied: it is revealed that ZnO luminescence spectra are significantly influenced by the crystal morphology. It is shown that the near and edge ultraviolet emission occurs primarily from the top (0001) planes of ZnO microrods; while the defect related visible emission was found to occur dominantly from the side facets. The room temperature cathodoluminescence analysis revealed that visible emission consists of a few overlapping peaks, arising due to recombination on common points and surface defects (Zni, Vo, Vo 0 /Vo * * , Vo ** and surface defects.). While at low temperature, only the luminescence due to neutral donor bound exciton (D 0 X) emission is observed. The data obtained suggest that the light emission spectra of ZnO material of diverse morphology can not be directly compared, although some common spectral features are present
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