Synchrotron radiation spectroscopy studies of ultrathin chromium films on titanium dioxide

We investigate the initial interaction of chromium in the sub-ML and ML regime with the surface of titanium dioxide. The reaction at the interface, in which TiO₂ is reduced and forms TiO_2-x, is monitored by electron spectroscopy. This reaction is reflected by appearance of Ti³⁺ state. Two chromium components are found already in the first step of growth. One component is assigned to Cr in the 3+ oxidation state, while the other one is assigned to metallic Cr. The reaction at the interface is also reflected by the appearance of two band gap states with a well defined character. With increasing overlayer thickness, the band gap emission develops to that of metallic Cr, but the properties are not bulk-like.