PNNL

Abstract

The ability to form reliable, low-resistance Ohmic contacts is of critical importance to the ongoing development of oxide electronics. Most metals form Schottky barriers when deposited on oxide surfaces. Ohmic contacts rarely occur, and the associated contact resistances are not particularly low. Little is known at an atomistic level about what leads to a good Ohmic contact on a wide-gap oxide. Here we describe the structure of a simple, yet exceptionally low-contact resistance Ohmic metal on an important oxide semiconductor -- epitaxial Cr on Nb-doped SrTiO3(001). Heteroepitaxial growth is accompanied by Cr diffusion into the STO and occupation of interstitial sites within the first few atomic planes. Interstitial Cr is ionized and the resulting electrons occupy the STO conduction band, resulting in effective metallization near the interface.