Geometric shapes and vacancy rates for the modulation of the electronic and transport properties in MoS2 nanoflakes

Abstract

The electronic and transport properties of MoS2 nanoflakes are investigated using a six-band tight-binding model. The energy band structures are modified by changing the shape, size, vacancy rate, and vacancy distribution of the flakes, resulting in additional energy states in the energy bandgap region. For large flakes, the effects of their geometric shape are found to be negligible, because shape effects on the density of states (DOS) decrease with increasing flake size. The positions and DOS of these additional in-gap states are strongly related to the vacancy rate as well as to the distribution of vacancies. The number of in-gap states and the magnitude of the density of these states are both proportional to the vacancy rate. However, if the rate is high enough for vacancy clusters to form, the transmission is somewhat degraded at certain incident energies, owing to backscattering and capture of carriers by the clusters. Since the current transmission is determined primarily by the detailed energy band structure, the in-gap states due to vacancies enable the realization of low-energy currents in devices based on low-dimensional materials.