MoO sub x (x < = 2) ultrathin film growth from reactions between metallic molybdenum and TiO sub 2 surfaces

Exposures to oxygen at room temperature and annealings under vacuum were carried out on deposits obtained from molybdenum interacting with (110) TiO sub 2 surfaces 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 TiO sub 2 /Mo interactions are inactive towards oxygen whereas the metallic molybdenum clusters, which grew on top of the interfacial layers, oxidise into MoO sub 3 . Besides, during annealings under vacuum, substrate oxygen anions can diffuse into the deposit. Thus, between 400 and 500 deg C, molybdenum oxide layers are progressively oxidised into MoO sub 2 . Moreover, from the annealing temperature, it is possible to control the film oxidation and to select its stoichiometry. At higher temperatures, MoO sub 2 layers oxidise, leading to MoO sub 3 clusters which sublimate restoring a clean TiO sub 2 surface. As concerns the metallic clusters, if they are exposed to air and then oxidised in MoO sub 3 prior to annealing, they sublimate below 300 deg C.