Understanding the Dynamic Liquid-Assisted Chemical Vapor Deposition Growth of Copper Telluride and Its Low-Temperature Phase Transition

Abstract

Copper telluride is an emerging layered material that has been shown to undergo phase transitions with slight modifications in its stoichiometry (Cu2–xTe) at high temperatures. Using Raman spectroscopy and X-ray diffraction, we complete the spectrum of temperatures and detect a low-temperature phase transition of copper telluride for the first time. Moreover, liquid-assisted chemical vapor deposition (CVD) growth is heavily explored for its potential to grow various crystals at a large scale. However, the role that the liquid precursor plays in these growths remains largely elusive, and a theoretical study is impeded by the bulk amorphous liquid precursor. Here, we experimentally demonstrate how the liquid precursor contributes to the morphological orientations of Cu0.664Te0.336 crystals. Based on this, we propose a growth process in which tellurium supersaturation of the liquid precursor yields nucleation sites both on the surface and internally. Etching of Cu0.664Te0.336 via H2 flow is also achieved during CVD to increase the density of exposed sites. Optimal parameters to control H2 flow to achieve layer-by-layer thinning in geometric crystals are also realized. Our study thereby enhances the understanding of temperature-dependent copper telluride phases and presents liquid-assisted growth as a platform ripe with opportunities for materials engineering.