The growth, epitaxy and reactivity of ultrathin metal films on a metal oxide surface.

摘要

In order to understand the nucleation, growth, interfacial reactivity and chemisorption properties of ultrathin metal films on oxide surfaces, we have studied ultrathin metal Au and Pt films on the TiO2 (110) substrate, together with Au on a polyimide (polymer) substrate, using a variety of surface science techniques.;The Au and Pt films are evaporated under UHV conditions onto clean and stoichiometric TiO2 (110) at elevated substrate temperatures. We present here a detailed investigation of the initial stage growth mode of Au on TiO2 (110) by means of low energy ion scattering (LEIS), and the interfacial reactivity of Au and Pt films with TiO2 (110) by X-ray photoelectron spectroscopy (XPS). The chemisorption of carbon monoxide and chemisorption-induced surfactant effects on Pt films are also studied by combined LEIS and XPS techniques.;The growth and surface morphology of nanometer Au islands are studied using high resolution scanning electron microscopy (HRSEM). It has been found that Au evolves at room temperature from compact islands, to worm-like islands, to percolation and to rough but continuous films. Epitaxial studies of individual Au islands have been performed on both high temperature annealed and deposited samples using electron back-scattered diffraction (EBSD). Different epitaxial orientations are observed under these two cases.;The combination of XPS, LEIS, HRSEM and EBSD allows us to study the growth of ultrathin metal films in a controlled manner. It turns out that the control of growth morphology of metal particles is of major importance in determining the surface properties of catalyst particles and sensor materials.