Structural study of ultrathin metal films on TiO 2 using LEED, ARXPS and MEED

Abstract

A structural study of ultrathin Cr, Fe and Cu metal films on stoichiometric and Ar + sputtered TiO 2(110) surfaces has been carried out using low energy electron diffraction (LEED), angle-resolved XPS (ARXPS) and two-dimensional medium energy backscattered electron diffraction (MEED). Although LEED results indicate only weak long range order for all three metal films (Cr, Fe and Cu) on TiO 2(110), clear evidence for a locally ordered structure can be observed using ARXPS and MEED. Both Cr and Fe films grow with bcc(100) structures on stoichiometric TiO 2(110) yielding pronounced forward scattering features in ARXPS and MEED data. Cu overlayers grow with fcc(111) structures exhibiting two equivalent domain orientations on TiO 2(110) that yield less pronounced features in ARXPS. However, MEED measurements of Cu films with different electron surface incidence angles show clear fcc(111) patterns for different domains. Both bcc(100) and fcc(111) MEED patterns are simulated by single scattering cluster (SSC) calculations, and the results are qualitatively consistent with experimental data. A bcc(100) short range ordering is also observed for ultrathin Cr and Fe films on long range disordered Ar + sputtered TiO 2(110) surfaces.