The Zn_{1-x}Cd_xO ternary alloys with a narrow band gap, which are useful for light emitters in the visible wavelengths, are studied with respect to the unsteady region in mixing. This unstable region in mixing is calculated from the free energy of mixing using the strictly regular solution model. The interaction parameter used in this calculation is obtained by means of the valence-force-field model. An influence of the strain energy induced by substrate on the region of the spinodal decomposition for the Zn_{1-x}Cd_xO system is studied and discussed.
The analysis of spinodal decomposition in the Zn_{1-x}Cd_xO 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 Zn_{0.95}Cd_{0.05}O 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 Zn_{1-x}Cd_xO 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 Zn_{0.95}Cd_{0.05}O microstructure is in good agreement with experimental results, which have been obtained for this solid solution.
The structural, cohesive and electronic properties of fullerene-like isolated Zn₄₄Cd₄O₄₈ cluster with consideration of CdO phase clusterization are studied in the frames of density functional theory B3LYP/3-21G(d). It is revealed that an enlargement of CdO phase content in Zn₄₄Cd₄O₄₈ cluster leads to nonlinear rapid increase in cohesive energy and cluster stability, as well as band-gap energy shrinkage.
Se-doped ZnO films have been deposited on the sapphire substrates by the radio-frequency magnetron sputtering technique. An influence of the isoelectronic impurity Se on the room-temperature luminescence of the ZnO films is studied. It is revealed that the Se doping leads to an appearance of the intense near-band edge emission spectrum, which consists of three emission bands. The dominant emission band is related to the recombination of the bound excitons. The radiation caused by the band-to-band transitions of free carriers is observed in the high-energy side of the spectrum (ħω > E_{g}).
X-ray photoelectron spectroscopy was employed to characterize the surface chemistry and electronic properties of the Zn_{1-x}Cd_{x}O semiconductor systems obtained at the different growth conditions. The effect of the growth conditions on the core and valence band spectra as well as room-temperature photoluminescence of the Zn_{1-x}Cd_{x}O films was investigated and discussed. Behavior of the X-ray photoelectron spectroscopy peaks indicated an increase of the cadmium and a depletion of the oxygen concentrations upon changing the Ar/O_2 gas ratio and dc power.
We have fabricated photosensitive anisotype n-Cd_{x}Zn_{1-x}O/p-CdTe heterojunctions by a deposition of Cd_{0.5}Zn_{0.5}O film onto freshly-cleaved CdTe monocrystalline wafers using a radiofrequency magnetron reactive sputtering of a zinc-cadmium alloy target. Fundamental electrical properties of the heterojunctions were studied. Dominant mechanisms of a current transport were found. n-Cd_{x}Zn_{1-x}O/p-CdTe heterojunctions were photosensitive and were able to operate both in photovoltaic and photodiode modes.
Undoped, nitrogen-doped and aluminum-nitrogen co-doped ZnO films were deposited on Si substrates by magnetron sputtering using layer-by-layer method of growth. X-ray photoelectron spectroscopy was employed to characterize electronic properties of undoped and nitrogen doped ZnO films. The effects of N and N-Al incorporation into the ZnO matrix on the X-ray photoelectron spectroscopy core-level and valence-band spectra of the films were studied and discussed.
Here we report the effect of the irradiation by 167 MeV Xe^{26+} ions (in the fluence range up to 3× 10^{12} ions/cm^2) on the undoped and Cd-doped (0.4, 0.5 at.%) ZnO films deposited by radiofrequency magnetron sputtering. As-grown and irradiated samples were investigated by cathodoluminescence spectroscopy. It was found that the radiation causes a decrease in intensity of luminescent peaks and a redistribution of the radiative recombination channels. We revealed that the cadmium incorporation into ZnO lattice enhances the radiation resistance of ZnO film.
Zn_{0.9}Cd_{0.1}O ternary alloys have been grown on the sapphire substrates by using the direct current (dc) magnetron sputtering. X-ray diffraction measurements showed that all samples were highly oriented films along the c-axis perpendicular to the substrate surface. X-ray diffraction confirmed that the crystal quality of Zn_{0.9}Cd_{0.1}O films can be controlled by changing the gas ratio of Ar/O_2. The optical properties of these films have been investigated by means of the optical transmittance and the low-temperature photoluminescence spectra. It was found that the optical band gap of the deposited films can be tuned by growth parameters. The luminescence processes are considered in the terms of alloy fluctuation.
Zinc oxide films were grown on sapphire substrates by direct current magnetron sputtering and irradiated by electrons with energy 10 MeV and fluences 10^{16} and 2 × 10^{16} cm^{-2}. As-grown and irradiated samples were investigated by X-ray diffraction and photoluminescence spectroscopy. It was found that radiation causes the appearance of complex defects, reducing the size of coherent scattering regions and the increase of the defect PL band.
ZnO films doped with the cadmium (0.4-0.6%) were grown on crystalline sapphire c-Al_2O_3 substrates applying radiofrequency magnetron sputtering at the temperature of 400°C in Ar-O_2 atmosphere. The as-grown films were investigated in detail using X-ray diffraction, X-ray photoelectron spectroscopy, and cathodoluminescence spectra. The X-ray diffraction analysis revealed that the films possess a hexagonal wurtzite-type structure with the dominant crystallite orientation along the c axis. It was found that the small concentration of the cadmium significantly enhances the ultraviolet emission associated with excitonic transitions. We suggest that this enhancement effect mainly results from appearance of the cadmium isoelectronic traps, which may bind an exciton, thereby increasing the probability of radiation recombination. The effect of Cd isoelectronic impurity on structural and luminescent properties of ZnO films is discussed.
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