University College London
I work in the general area of computational materials modelling, focusing on the properties of complex oxides. Here I provide a lay explanation of one of my recent papers (published in Advanced Materials) on a pathway to creating low-resistance Ohmic contacts at nanoscale, a development which is of critical importance to the on-going advancement of oxide electronics.
In collaboration with researchers from the Pacific Northwest National Laboratory and the University of California, Davis, I worked to determine the physical drivers required to facilitate formation of an “Ohmic contact”, which is highly desirable type of an electrical junction, between a metal and an oxide semiconductor.
When a metal and a semiconductor are joined, there are two possible types of contact that can result. An “Ohmic contact”, in which electrical current can pass in either direction, and a “Schottky barrier”, in which case the current has preferential direction.
The type of contact depends on the combination of metal and semiconductor used but the vast majority of metals form Schottky barriers when deposited on oxide surfaces. Not only do Ohmic contacts rarely occur but also little is known at an atomistic level about what leads to a good Ohmic contact on a wide-gap oxide.
The study, which reports both experimental and theoretical results, suggests that an overlayer of Chromium metal deposited on the (001) surface of Niobium-doped strontium titanate (SrTi03), an oxide semiconductor of considerable interest in science and technology, forms a low-resistance Ohmic contact.
It is revealed that in-diffusion of metal atoms into the first few atomic planes of the oxide is of critical importance to both anchoring the overlayer of Chromium for good adhesion and metalizing the oxide surface for very low contact resistance. These results provide a new strategy for generating Ohmic contacts in other metal/oxide interfaces as well as optimizing their characteristics.
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