Preferred Orientation in Ti Films Sputter-Deposited on SiO2 Glass: The Role of Water Chemisorption on the Substrate

Abstract
Ti thin films have been grown on SiO2 glass layers at 350°C by ultrahigh vacuum magnetron sputtering with a small amount of H2O, H2 or O2 gas introduction to investigate the influence of adsorption on the crystallographic orientation of the Ti films. In situ reflection high-energy electron diffraction (RHEED) and ex situ X-ray diffraction (XRD) studies showed that a water vapor introduction at the beginning of sputter deposition promotes a highly preferred (002) orientation, whereas H2 gas or O2 gas introduction does not affect the orientation. These results indicate that the increase of water chemisorption on the substrate by H2O gas introduction and reduction of the surface free energy enhance the self-assembly of the Ti atoms toward the most stable C-axis orientation.