Liquid-Solid Assisted synthesis of 2D M₂X Materials

Two-dimensional transition metal dichalcogenides (TMDs) MX₂ with M = (W, Mo) and X = (Te, Se, S) are known for their layered structure which yields extraordinary electronic properties. However, other transition metal chalcogenides have been rarely reported. In this work, we have used liquid−solid interface growth which enables us to synthesize layered group 11 chalcogenides with a focus on hexagonal Cu₂X (X=Te, Se, S) crystal system. It is observed that liquid copper plays a significant role in synthesizing these new 2D material systems. Like traditional TMDs, thickness-dependent phonon signatures are observed, and a high-resolution atomic structure reveals a hexagonal layered phase of Cu₂Te that prefers to grow in lattice-matched layers. Theoretical calculations on these structures show thickness-dependent metallic and semiconducting natures, suggesting a promising potential for 2D material electronics. As theoretically predicted ¹ these materials cover a large range of bandgap i.e. 0.2 to 2.8 eV, high carrier mobilities, we believe this work opens a new paradigm in the utility of these materials in a variety of applications.