Strain effects on the energy band structure and electronic states of single-layer MoTe₂, WTe₂ and their heterostructures

ABSTRACT

First-principle calculations are done to investigate the strain effects on the energy band structure and electronic states of single-layer MoTe₂, WTe₂ and their vertically stacked heterostructures. It is illustrated that their band gaps decrease with increasing tensile strain, but increase with compressive strain, and have a maximum value at a compressive strain of 2%. The ideal single-layer MoTe₂, WTe₂ and their hybrid structure are direct band-gap semiconductors, which are maintained up to a tensile strain of 3%, but change into indirect ones at a compressive strain of 2–3%. The band gap of the MoTe₂/WTe₂ heterostructures is substantially reduced owing to the coupling between MoTe₂ and WTe₂ sublayers. The band structure is type II alignment, and is advantageous to photoelectric applications. In brief, lattice straining might induce the rearrangement of band structure, and thus could be adopted to tune the physical properties of 2D materials as well as their hybrids.

KEYWORDS:

• Heterostructure
• MoTe₂
• WTe₂
• electronic states
• strain