MoOx(x≤2) ultrathin film growth from reactions between metallic molybdenum and TiO2surfaces

Exposures to oxygen at room temperature and annealings under vacuum were carried out on deposits obtained from molybdenum interacting with (110) TiO2surfaces in order to obtain molybdenum oxide ultra thin films. Exposures to oxygen at room temperature show that the interfacial molybdenum oxide layers resulting from the TiO2/Mo interactions are inactive towards oxygen whereas the metallic molybdenum clusters, which grew on top of the interfacial layers, oxidise into MoO3. Besides, during annealings under vacuum, substrate oxygen anions can diffuse into the deposit. Thus, between 400 and 500°C, molybdenum oxide layers are progressively oxidised into MoO2. Moreover, from the annealing temperature, it is possible to control the film oxidation and to select its stoichiometry. At higher temperatures, MoO2layers oxidise, leading to MoO3clusters which sublimate restoring a clean TiO2surface. As concerns the metallic clusters, if they are exposed to air and then oxidised in MoO3prior to annealing, they sublimate below 300°C.