Mechanical modulation of 2D transition metal dichalcogenide alloys†

Abstract

Controlling the mechanical properties of two-dimensional transition metal dichalcogenides (TMDs) is essential for their integration into advanced flexible electronic and optoelectronic devices. Alloying these materials allows modulation of their optical characteristics and energy structure, greatly improving their design flexibility and functionality. However, the impact of alloying on their mechanical behavior has remained uncovered. We developed a novel means for alloying suspended TMD devices. Specifically, we synthesized Mo_1−xW_xS₂ nano-drumheads using a diffusion-based alloying process, in which we first mechanically exfoliated WS₂ nano-drumheads followed by the diffusion of Mo atoms into them, thereby yielding a wide range of possible atomic compositions (0 ≤ x ≤ 1). Then, we studied their mechanical properties via atomic force microscopy force-spectroscopy and Raman analyses, from which we correlated the mechanical resistance of the alloys with their atomic composition and showed that a high concentration of W atoms is associated with a high Young's modulus. Atomistic simulations demonstrate how the estimated Young's modulus follows the same trend. Therefore, this work presents a process for alloying nano-drumheads and sheds light on the fundamental mechanics of Mo_1−xW_xS₂. By doing so we demonstrate their tunability in terms of atomic composition and open the path for their integration into advanced applications, such as tunable sensors and flexible electronics.