First-principles study on the electronic structure of transition-metal dichalcogenides/metal interfaces and effect of strain

Abstract

Two dimensional Transition Metal Dichalcogenides have been extensively studied as an emerging material for future semiconductor channel. However, the high contact resistance between conventional metal/TMDCs interface, along with Fermi Level Pinning effect, is the major issues impeding the further development for industrial applications. In this study, the Schottky barrier height and charge distribution of various TMDC/metal interfaces including its isolated states were calculated in First Principle Calculation with Density Functional Theory. The calculation results indicated that TMDC/metal interfaces exhibited Fermi Level Pinning effect even in clean interfaces, deviating from the ideal Schottky barrier heights. With investigation on electronic structure including charge density, the observed fermi level pinning was attributed to the Metal Induced Gap States and charge redistribution including Pushback effect. Additionally, the effects of in-plane strain on interfaces were investigated. For Ag and Au interfaces under tensile strain, reduced Schottky barrier height was identified. However, mixed trends with increase of Schottky barrier height was observed for other interfaces. This variation was attributed to the response of isolated TMDCs for strain. Isolated TMDCs exhibited varying response to the in-plane strain due to orbital contribution on local band edges, while linear response was observed for metal. This behavior was preserved after interface formation and dominant for the modulation of Schottky barrier, implying different suitability for strain engineering to Schottky barrier control. With the calculation on tunneling property, it was further revealed that the strain can reduce the tunneling barrier of interfaces.