Synthesis of Wafer-Scale WS₂ Thin Films via Chelant-Assisted Solution-Based Processing

Two dimensional, atomically thin van der Waals Heterostructures such as transition metal dichalcogenides (TMDs) are of high interest due to their mechanical, electrical, and optical properties. Owing to their highly tunable nature, they make excellent candidates for optoelectronic devices. The growth of TMDs is a well-studied topic. During synthesis, a metal oxide or salt decomposes and is then reduced by the target chalcogen. For WS₂, uniform, wafer-scale growth has been a challenge in all types of growth methods, especially so for solution-based processes. Previous studies conducted by our group have shown that chelating agents such as Ethylenediaminetetraacetic acid (EDTA) greatly increase the surface coverage and uniformity of solution based MoS₂ thin films. The chelant effectively anchors the molecule to the substrate before thermolysis. The effects of varying chelating agents have not yet been studied. Here, we present a chelant-enhanced, spin coat based growth of wafer-scale, uniform WS₂ and MoS₂ thin films. There are three chelating agents used in the study: EDTA, glutamic acid, and glycine. Our results show the chelating agent’s critical role in growing uniform films. Our work provides a template for the wafer-scale synthesis of other two-dimensional materials.