Growth and morphology of Te films on Mo

Tellurium films were deposited by thermal evaporation on a molybdenum substrate held at 120°C. The growth of the films was monitored by quantitative X-ray photoelectron spectroscopy and by atomic force microscopy. Reaction of the Te films with K vapour was also used to evaluate the thickness of the films. It has been found that for low exposures Te grows as a uniform layer, up to a thickness of about 0.4 nm. For higher exposures we observed the formation of islands of increasing thickness that cover an increasing fraction of the substrate, the remaining fraction being covered by a continuous thin layer. Implications of such a morphology on the performances of Te-based photocathodes in photo-injectors technology are discussed.