Room temperature deposition of Al-doped ZnO films on quartz substrates by radio-frequency magnetron sputtering and effects of thermal annealing

High-quality Al-doped zinc oxide (AZO) thin films have been deposited on quartz substrates by radio-frequency magnetron sputtering at room temperature for thin film solar cell applications as transparent conductive oxide (TCO) electrode layers. Effects of post-deposition annealing treatment in pure nitrogen and nitrogen/hydrogen atmosphere have been investigated. Annealing treatments were carried out from 300 degrees C to 600 degrees C for compatibility with typical optoelectronic device fabrication processes. A series of characterization techniques, including X-ray diffraction, scanning electron microscopy, Hall, optical transmission, and X-ray photoelectron spectroscopy has been employed to study these AZO materials. It was found that there were significant changes in crystallinity of the films, resistivity increased from 4.60 x 10(-4) to 4.66 x 10(-3) Omega cm and carrier concentration decreased from 8.68 x 10(20) to 2.77 x 10(20) cm(-3) when annealing in 400 degrees C pure nitrogen. Whereas there were no significant changes in electrical and optical properties of the AZO films when annealing in 300-500 degrees C nitrogen/ hydrogen atmosphere, the electrical stability of the AZO films during the hydrogen treatment is attributed to both desorption of adsorbed oxygen from the grain boundaries and production of additional oxygen vacancies that act as donor centers in the films by removal of oxygen from the ZnO matrix. These results demonstrated that the AZO films are stably suited for TCO electrodes in display devices and solar cells. (C) 2010 Elsevier B.V. All rights reserved

Annealing effects on the optical and structural properties of Al(2)O(3)/SiO(2) films as UV antireflection coatings on 4H-SiC substrates

Al(2)O(3)/SiO(2) films have been prepared by electron-beam evaporation as ultraviolet (UV) antireflection coatings on 4H-SiC substrates and annealed at different temperatures. The films were characterized by reflection spectra, ellipsometer system, atomic force microscopy (AFM), X-ray diffraction (XRD) and Xray photoelectron spectroscopy (XPS), respectively. As the annealing temperature increased, the minimum reflectance of the films moved to the shorter wavelength for the variation of refractive indices and the reduction of film thicknesses. The surface grains appeared to get larger in size and the root mean square (RMS) roughness of the annealed films increased with the annealing temperature but was less than that of the as-deposited. The Al(2)O(3)/SiO(2) films maintained amorphous in microstructure with the increase of the temperature. Meanwhile, the transition and diffusion in film component were found in XPS measurement. These results provided the important references for Al(2)O(3)/SiO(2) films annealed at reasonable temperatures and prepared as fine anti-reflection coatings on 4H-SiC-based UV optoelectronic devices. (c) 2008 Elsevier B.V. All rights reserved