First-Principles Study On The Electronic Structure Modulation Of Two Kinds Of Van Der Waals Heterostructures

Two-dimensional materials and their heterostructures have always been one of the frontier research topics in the fields of condensed matter physics and materials science.They play an important role in the development of basic science and breaking through bottlenecks in nanoelectronics and optoelectronic technology.In this paper,through first-principles calculations,we present a comprehensive study of the electronic structure of HfSe₂/PtSe₂van der Waals heterostructure.We find that the electronic properties of HfSe₂/PtSe₂vd WH can be tuned effectively by applying strain and an electric field.Besides,we demonstrate that WTe₂/ZrS₂vd WH possess type-? band alignment,and their electronic properties have been systematically investigated under strain and electric field.Firstly,we found that the stacking pattern can modulate the band alignment of the HfSe₂/PtSe₂vd WH,such as type-?(AA,AB'and AC'stacking patterns)and type-?(AA',AB,AC stacking patterns).Among all of the stacking patterns,AA stacking pattern is the most stable configuration,with a interlayer distance of 2.87(?)at equilibrium and the band gap is1.0 e V.Moreover,the band gap of heterostructure can be modulated effectively by vertical strain,and when the interlayer distance increase to 3.24(?),the band alignment from type-? to type-? is happen.Further,when applying biaxial tensile strain,the band gap of HfSe₂/PtSe₂vd WH does not change much,and the band structure preserve type-? band alignment;when the compressive strain exceeds 3%,the transition between type-? to type-? band alignment can be observed.In addition,HfSe₂/PtSe₂vd WH always exhibits type-? band alignment under various electric field,and with a little change for the band gap.Secondly,we predict that the WTe₂/ZrS₂heterostructure possess stable type-? band alignment,and were not affected by the stacking patterns.We find that the WTe₂/ZrS₂vd WH preserves the type-? band alignment with various interlayer distances,which indicates that it can withstand vertical stress.Although the biaxial strain did not change the type of band alignment for WTe₂/ZrS₂vd WH,when the tensile strain exceeds 3%,it is interesting that the band structure of the WTe₂layer changes from direct gap to indirect gap.At the same time,the band alignment for WTe₂/ZrS₂vd WH preserves type-? under the various electric field.Therefore,this kinds of heterostructure with stable type-? band alignment was expected to be used in microelectronic devices,such as tunnel field effect transistors(TFETs).