Abinitio simulation of the structure and transport properties of zirconium and ferromagnetic cobalt contacts on the two-dimensional semiconductor WS2

Abstract

Using density-functional theory calculations, the atomic and electronic structure of single-layer ${\mathrm{WS}}_{2}$ 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 ${\mathrm{WS}}_{2}$ with Schottky barriers of 0.45 eV and 0.62 eV for Zr and Co, respectively. With the help of quantum transport calculations, we address the conductive properties of a freestanding ${\mathrm{WS}}_{2}$ 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 ${\mathrm{WS}}_{2}$, 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.