MoOx (x <= 2) ultrathin film growth from reactions between metallic molybdenum and TiO2 surfaces

Exposures to oxygen at room temperature and annealings under vacuum were ca rried out on deposits obtained from molybdenum interacting with(1 1 0) TiO2 surfaces in order to obtain molybdenum oxide ultra thin films. Exposures t o oxygen at room temperature show that the interfacial molybdenum oxide lay ers resulting from the TiO2/Mo interactions are inactive towards oxygen whe reas the metallic molybdenum clusters, which grew on top of the interfacial layers, oxidise into MoO3. Besides, during annealings under vacuum, substr ate oxygen anions can diffuse into the deposit. Thus, between 400 and 500 d egreesC, molybdenum oxide layers are progressively oxidised into MoO2. More over. from the annealing temperature, it is possible to control the him oxi dation and to select its stoichiometry. At higher temperatures, MoO2 layers oxidise. leading to MoO3 clusters which sublimate restoring a clean TiO2 s urface. As concerns the metallic clusters, if they are exposed to air and t hen oxidised in MoO3 prior to annealing. they sublimate below 300 degreesC. (C) 2001 Elsevier Science B.V. All rights reserved.