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

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

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

Thermoelectric studies of electronic properties of ferromagnetic GaMnAs layers

Thermoelectric power, electrical conductivity, and high field Hall effect were studied over a broad temperature range in ferromagnetic Ga₁₋xMnxAs epitaxial layers (0.015 ≤ x ≤ 0.06). Thermoelectric power analysis gives information about carrier transport mechanisms in layers with both metallic and non-metallic types of conductivity and allows determination of the Fermi energy and carrier concentration. At high temperatures (T > 70 K), the thermoelectric power in GaMnAs linearly increases with increasing temperature. That indicates the presence of a degenerate hole gas with the Fermi energy EF = 220 ± 25 meV, nearly independent of Mn content (for 0.02 ≤ x ≤ 0.05). At lower temperatures, GaMnAs layers with metallic-type conductivity show an additional contribution to the thermoelectric power with the maximum close to the Curie temperature

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

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)