Tunable MoS2 bandgap in MoS2-graphene heterostructures

Articles you may be interested in Toward epitaxially grown two-dimensional crystal hetero-structures: Single and double MoS2/graphene hetero-structures by chemical vapor depositions Appl. Density functional theory study of chemical sensing on surfaces of single-layer MoS2 and graphene Using density functional theory calculations with van der Waals corrections, we investigated how the interlayer orientation affects the structure and electronic properties of MoS 2-graphene bilayer heterostructures. Changing the orientation of graphene with respect to MoS 2 strongly influences the type and the value of the electronic bandgap in MoS 2 , while not significantly altering the binding energy between the layers or the interlayer spacing. We show that the physical origin of this tunable bandgap arises from variations in the S–S interplanar distance (MoS 2 thickness) with the interlayer orientation, variations which are caused by electron transfer away from the Mo–S bonds. Two-dimensional (2-D) materials can vary in terms of their electronic properties (e.g., graphene is metallic, hexagonal-BN (hBN) is insulating, and MoS 2 is semicon-ducting) and, hence, are attractive, often in combinations, for technological applications. Among this class of materials, many studies have focused on molybdenum disulfide, which exhibits a number of interesting properties such as bandgap variation with the number of layers, 1,2 high carrier mobility, 3,4 high Seebeck coefficient, large excitonic effects, 8 environmental sensitivity, 9,10 and high mechanical strength, 11 —properties which make this material promising for next-generation optoelectronic and nanoelectronic devices. 12,13 Recent efforts have focused on taking advantage of the individual properties of different 2-D materials by fabricating heterostructures, 14 which are vertical stacks of 2-D layers of dissimilar materials held together by van der Waals (vdW) forces. Such heterostructures not only can lead to opening of a bandgap in graphene (e.g., in graphene-hBN bilayers) 15 without impairing its electronic mobility but can also develop direct bandgaps in multilayer heterostructures 16 or improve the on/off current ratios drastically ($10 4 in graphene-MoS 2). Motivation for the present study stems from the fact that interlayer orientation can affect the electronic properties of monolayers on their growth substrate, 19,20 as well in multi-layered structures of the same material. 21 In this Letter, we investigate the use of interlayer orientation between two different 2-D materials as a tuning parameter for the electronic properties of the bilayer heterostructure. We present results from vdW-corrected density functional theory (DFT) calculations on the effect of interlayer orientation on the electronic structure of the MoS …