Ab initio simulation of the structure and transport properties of zirconium and ferromagnetic cobalt contacts on the two-dimensional semiconductor WS_2

Abstract

Using density-functional theory calculations, the atomic and electronic structure of single-layer WS_2 attached to Zr and Co contacts are determined. Both metals form stable interfaces that are promising as contacts for injection of n-type carriers into the conduction band of WS_2 with Schottky barriers of 0.45eV and 0.62eV for Zr and Co, respectively. With the help of quantum transport calculations, we address the conductive properties of a free-standing WS_2 sheet suspended between two Zr contacts. It is found that such a device behaves like a diode with steep I-V characteristics. Spin-polarized transport is calculated for such a device with a floating-gate Co electrode added. Depending on the geometrical shape of the Co gate and the energy of the carriers in WS_2, the transmission of spin majority and minority electrons may differ by up to an order of magnitude. Thus the steep I-V characteristics of the nanoscale device makes it possible to realize a spin filter.