Microstructural characterization of ZnO thin films deposited by RF magnetron sputtering

Abstract

Zn0 is attracting more attention because of the good optical, electrical, and piezoelectrical properties. It has potential uses in optoelectronical systems such as photodetectors, light emitting diodes, electroluminescence devices, solar cells, and flat cathode ray tubes. Its band gap is wide (3.3 eV). Recently, optically pumped ultraviolet (UV) ZnO-based lasers have been demonstrated at room temperature. . Some research have shown that textured Zn0 films might have higher quantum efficiency than GaN and could become the next generation UV semiconductor laser. Since Zn0 has large piezoelectrical and optical efficiency, it is also a promising material for the surface acoustic wave (SAW) device, a component of optical integrated circuit. Fabrication of Zn0/GaAs SAW devices has already been reported. Although some works concerning Zn0/Si heterostructures have been reported, almost all the heterostructures were grown by using either molecular beam epitaxy or metalorganic chemical vapor deposition. However, very few studies on ZnO/Si heterostructures with high-quality films grown via a simple method have been performed. Since the microstructural properties of ZnO thin films are strongly affected by their electrical and optical properties, studies concerning the effects of annealing and substrate temperature on the microstructural properties of ZnO thin films and ZnO/Si heterostructures are necessary for fabricating high-quality optoelectronic devices utilizing ZnO/Si heterostructures. In particular, since mismatches in the crystal lattices on opposite sides of the ZnO grain boundaries significantly deteriorate the optical properties of thin films, the atomic structure of [00011-tilt grain boundaries in ZnO was investigated using high-resolution transmission electron microscopy (HRTEM) and atomistic calculations. HRTEM observation was conducted for [0001) fiber-textured ZnO thin films. The atomic structure of the boundaries is discussed with a focus on grain boundary...