Controllable Phase Stabilities in Transition Metal Dichalcogenides through Curvature Engineering: First‐Principles Calculations and Continuum Prediction

Abstract

A controllable phase transition between the semiconducting 2H phase and metallic/semimetallic T (1T, 1T , and 1T ) isomorphs provides an effective route to tune and even switch physical and electronic properties within 2D transition metal dichalcogenides (TMDs). In this study, the feasibility of curvature engineering in manipulating the structural phase is investigated employing first-principles density functional theory (DFT) calculations and continuum mechanics analysis. With WSe 2 and MoTe 2 as TMD representatives, it is found that bending deformation can not only energetically induce 2H → T (1T, 1T , or 1T ) phase transformation, but also kinetically facilitate the phase transition by lowering transition activation barriers. Moreover, a phase stability diagram is constructed which suggests ways of achieving both uniformly 2H → T phase transition and programming printing of T phases in 2H-TMD membranes. The theoretical results not only suggest a new feasible experimental design strategy of phase engineering, but also sheds light on novel device design with the patterning of T phases on the 2H-TMD membrane.The fascinating physical and chemical properties of the atomically thin VI transition metal dichalcogenide (TMD), a material consisting of two layers of chalcogenide atoms sandwiching one layer of VI transition metal atoms in between, has inspired numerous research studies toward ultra-high light absorption and emission, [1] nanoscale piezoelectric behaviors, [2][3][4][5] and extraordinary valleytronics effects, [2,6,7] showing great promise in numerous applications, such as solar energy, [8][9][10][11][12][13][14] illumination, [11,[14][15][16][17] nano power generator, [2] and valleytronics devices. [6,7,14] Recently, the TMD family attracts further attention because of polymorphism. As shown by many studies, [7,[18][19][20][21] besides the normal octahedral 2H phase, TMDs may assume the form of

HfS2/MoTe2 vdW heterostructure: bandstructure and strain engineering based on first-principles calculation

“…For example, strain can also reduce photoluminescence and regulate polarization associated with direct or indirect band gap transitions. 43 There have been many reports on the simulation and modeling of strain-activated band structure conversion. The effects of strain on electrical, optical, and magnetic properties have also been well studied and predicted.…”