SYNCHROTRON-RADIATION-INDUCED PHOTOEMISSION-STUDY OF VO2 ULTRATHIN FILMS DEPOSITED ON TIO2(110)

Synchroton-radiation-induced photoemission spectroscopy (SRPES) measur ements were carried out on clean and VO2-deposited TiO2 (110) surfaces . Metal V was deposited at room temperature (RT) onto the TiO2 surface and then oxidized to VO2 at 473 K. At a V coverage of 0.2 ML on TiO2 (110), both metallic and oxidized states of V 3d are clearly seen near the Fermi level (E-F), indicating a strong interaction of metal V wit h O even at RT. After oxidation of V, a clear (1 x 1) VO2 superstructu re appears. A semiconductor-to-metal phase transition occurs when the VO2 film is heated. The energy shift near E-F is 0.1 eV over the RT to 393 K temperature range. This process for the ultrathin film was foun d to be reversible in that temperature range. (C) 1998 Elsevier Scienc e B.V. All rights reserved.