Electronic states at the interface of Ti–Si oxide on Si(100)

Abstract

The requirement for high K dielectrics for Si devices includes both a low interface state density and a band alignment that blocks both electrons and holes. Titanium dioxide materials are known to exhibit dielectric constants of 80 or higher depending on the crystal structure and, as such, are prime candidates for gate dielectrics. We employ an ultrathin layer of SiO2 prior to the formation of a Ti oxide to limit the density of defect states. The electronic structure is observed during the stepwise growth of the oxide using x-ray and ultraviolet photoemission spectroscopy. Measurements indicate Ti oxide states at approximately 2 eV below the Si valence band maximum suggesting that the TiO2 conduction band aligns with the Si conduction band. The results indicate nearly flat bands in the silicon consistent with a low interface state density.