First-principles based study of graphene inserted tellurene-metal interface

Abstract

Atomically thin two-dimensional (2D) materials have attracted extensive research interest since the journey started with the successful isolation of graphene in 2004. 2D materials have shown remarkable advancement in the design of the sensor, optoelectronic devices, and flexible electronics. Continuous efforts are being made to fabricate the electronic devices based on these two-dimensional layered materials such as graphene, hexagonal boron nitride, transition metal dichalcogenides (TMD), phosphorene etc. Recently a new 2D material, tellurene has joined the 2D material family and its potential application is demonstrated through the fabrication of metal-oxide-semiconductor field effect transistor. This new 2D material has similar properties that of black phosphorene (BP) however shows better environment stability and lower synthesis cost. Bulk tellurium (Te) is one of the chalcogen group-VI materials possessing a unique helical chain structure with a narrow bandgap of 0.35eV, however the bandgap increases to 1.23eV at monolayer limit. Understanding electronic properties of 2D material interfaces with metal is crucial for designing any electronic devices. Although most of the 2D materials offer dangling-bond free, naturally passivated surface, unusual Fermi-level pinning is observed while interfacing with metals with wide range of work functions. First principles-based calculations based on density functional theory (DFT) provide us atomistic insight to the electronic properties of such 2D material-metal interface, which is difficult to probe even with most sophisticated experimental setup. In this work using DFT calculations we show that tellurene exhibits a very unusual Ohmic nature while interfacing with metals commonly used in experiments. The origin of such violation of classical Schottky-Mott rule is found to be hidden in its electronic localization function. Since a Schottky diode is also a useful device which finds several applications in an electronic system, we explore the possibility of realizing a tellurene based Schottky diode. We surprisingly observed that a Schottky barrier between tellurene and metal could be induced by insertion of graphene, a technique earlier used to reduce the Schottky barrier height between Molybdenum-di-sulphide and various metals. Tellurene is physiosorbed in the graphene interface, insertion of graphene screens the extent of hybridization between the tellurene and metal and thus a Schottky barrier is formed. A Schottky barrier can be useful in the design of tellurene based photodetector, sensor, and in high frequency switching response