Wafer-Scale Anion Exchange Conversion of Nonlayered PtS Films to van der Waals Two-Dimensional PtTe2 Layers with Negative Photoresponsiveness

Abstract

This study reports on the controlled vapor-phase anion exchange conversion of three-dimensional (3D) platinum(II) sulfide (PtS) thin films to two-dimensional platinum ditelluride (2D PtTe2) van der Waals (vdW) layers. The low temperature (i.e., 400 ?) thermal tellurization of chemical vapor deposition (CVD)-grown PtS thin films leads to the formation of 2D PtTe2 vdW layers with a modulated crystallographic orientation, i.e., a mixture of horizontally and vertically oriented 2D layers. This chemical conversion enables the tunable electrical transport accompanying semiconducting-to-metallic transition as well as negative photoresponsiveness in the 2D PtTe2 layers. Density functional theory (DFT) calculations verify the thermodynamic principle for the conversion in the frame of free energy landscapes. The present work suggests a new chemical route for controlling the atomic and chemical structures of 2D transition metal dichalcogenides (TMDs) toward their wafer-scale modulation of electrical and opto-electrical properties.