X-ray photoelectron spectroscopy study of low-temperature molybdenum oxidation process

The low-temperature oxidation during deposition by evaporation of molybdenum thin films has been investigated. Analysis by x-ray photoelectron spectroscopy and x-ray diffraction reveals that small differences in the substrate temperature during deposition may give rise to important changes in the final composition and structure of the molybdenum oxide. Changes in binding energy and line shape of the Mo 3d(5/2)-Mo 3d(3/2) doublet attributed to oxygen incorporation have been studied. Two principal steps can be distinguished, with a transition temperature of similar to 310 degrees C. Up to substrate temperatures of similar to 310 degrees C, the superficial Mo remains almost unaffected, with some oxygen dissolved. At similar to 310 degrees C, mixing of Mo-0 metal and molybdenum oxide (Modelta+ 0 < delta < 4) clusters or islands is observed. Finally, above this temperature a surface layer of molybdenum oxide, Mo6+, is formed. In addition, an abrupt change in d(100) interplanar parameter of Mo is observed. (C) 1999 American Institute of Physics. [S0021-8979(99)00312-6].