High Quality Epitaxial ZnO Films Grown Using Magnetron Sputtering

Zinc oxide films were sputter-deposited at 500 $^{\circ}$C on sapphire, SiC and GaN substrates using different mixtures of Ar and O$_{2}$. Post-deposition annealing up to 900 $^{\circ}$C in N$_{2}$ with rapid thermal processor resulted in films whose crystalline quality improved with the annealing temperature. The effects of deposition and annealing using different Ar-O$_{2}$ gas mixtures were also investigated. Films grown on sapphire in a 1:1 Ar-O$_{2}$ mixture and annealed in N$_{2}$ at 900 $^{\circ}$C for 5 min had the best quality. Room-temperature photoluminescence spectroscopy measurements revealed a near band edge luminescence at 3.25 eV with a FWHM value of 126 meV. The two-theta XRD measurements of these films showed a peak at 34.8$^{\circ}$, which corresponds to the diffraction from the (0 0 2) plane of the ZnO and indicates a strong c-axis orientation perpendicular to the surface at the sapphire substrate. Results from the transport properties of these films determined using Hall-effect measurements will be discussed.