A method of forming a hermetic barrier layer comprises sputtering a thin film from a sputtering target, wherein the sputtering target includes a sputtering material such as a low Tg glass, a precursor of a low Tg glass, or an oxide of copper or tin. During the sputtering, the formation of defects in the barrier layer are constrained to within a narrow range and the sputtering material is maintained at a temperature of less than 200° C.