| 초록 |
The fundamental aspects and applications of semiconducting transparent thin films are always one of the attractive and important fields in modern material science. Belong in oxide material class; ZnO crystallizing in the wurtzite structure is a typical semiconductor has attracted much attention due to its numerous interesting properties. ZnO has direct and wide bandgap, high transparency, high temperature stability, high electrical carriers’ mobility, tunable electronic and phonon transport properties. Recently, ZnO and related materials have been concentrated studied as promising materials for wide range of applications in piezoelectric transducers, phosphors-transparent conducting films, high-power devices and thermoelectric devices. For all these applications or other basic researches, the film growth with high quality, particularly the growth of high crystalline films is very important. The wurtzite structure of ZnO is an anisotropy structure so and the properties of crystalline ZnO films’ must be depended a lot on their growth directions. However, the growth behaviors and properties of ZnO with different growth directions haven’t been studied much. In this work, we report the growth and characterization of crystalline epitaxial Ga-doped ZnO films grown on sapphire substrates with different growth directions by plasma-assisted molecular beam epitaxy. The growth of ZnO with different orientations was done by the choosing of different orientations of sapphire substrates. The effects of Ga doping level to the growth of ZnO films and to the structural properties of grown films were also studied. The growths of the films were characterized by in-situ observations via reflection high-energy diffraction (RHEED). After growth finish, the morphology and structural properties of the films were characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM) and high-resolution x-ray diffraction (XRD). About the thermoelectric properties of these doped films, Seebeck’s coefficient, electrical conductivity and power factor were also investigated and compared. |
