A Solid Mechanics-Informed Continuum Model Approach to Phase Engineering Bendable Group VI Transition Metal Dichalcogenide Monolayers

Abstract

Materials science research towards atomically thin materials that can offer many unique properties has taken off in the 21st century. Two-dimensional transition metal dichalcogenides (2D TMDs) are one such class of atomically thin materials that has garnished heightened attention due to the fact that 2D TMDs express two crystal phase structures, where one crystal phase is electrically semi-conductive, while the other crystal phase is electrically conductive. It has been shown in recent research that the local strain state governs the expression of the two crystal phase structures. Therefore, intentional strain application has emerged as a promising method to achieve precise crystal phase manipulation in 2D TMDs. In particular, pre-applied in-plane strain coupled with out-of-plane deformation has been shown to realize predefined arrangements of conductive crystal phase. Using the principles of solid mechanics, two methods are proposed that simulate the crystal phase distribution of two commonly studied 2D TMDs: MoTe2 and WTe2. The resulting continuum model simulates the crystal phase distribution as a function of both applied in-plane biaxial strain and out-of-plane displacement, where the out-of-plane displacement is set through two separate local imprintings. One method, inherently elegant in design, is proven to be practically infeasible to implement, while the other less elegant method is implemented. Using tensile biaxial strain, several different phase patternings were achieved using 2D MoTe2, particularly arrangements of conductive vertical lines and diamond-like shapings. Using compressive biaxial strain, only arrangements of conductive vertical lines were able to be realized with 2D WTe2. It is clear that conductive phase engineering is easier to accomplish in 2D MoTe2 as opposed to 2D WTe2.