Coexistence of epitaxial Ta(111) and Ta(110) oriented magnetron sputtered thin film on c-cut sapphire

Abstract

Epitaxial Ta films were grown on c-cut and r-cut sapphire substrates using magnetron sputtering. X-ray diffraction measurements indicate that the Ta films grown on c-cut sapphire substrates have two different crystal orientations. Low vacuum base pressure produced films with the (111) plane parallel to the basal plane after an initial (110) plane growth phase, whereas high base pressure resulted in the growth of (110) plane parallel to the basal plane with three azimuthally oriented domains coexisting. The superconducting critical temperatures Tc of the films grown on c-cut substrates were found to be slightly higher than those for the films grown on r-cut substrates. The x-ray photoelectron spectroscopic data show oxygen content in the high vacuum base pressure deposited films and a difference in the valance band with different Ta surface planes.