The synthesis of competing phase GeSe and GeSe₂ 2D layered materials

We demonstrate the synthesis of layered anisotropic semiconductor GeSe and GeSe₂ nanomaterials through low temperature (∼400 °C) and atmospheric pressure chemical vapor deposition using halide based precursors. Results show that GeI₂ and H₂Se precursors successfully react in the gas-phase and nucleate on a variety of target substrates including sapphire, Ge, GaAs, or HOPG. Layer-by-layer growth takes place after nucleation to form layered anisotropic materials. Detailed SEM, EDS, XRD, and Raman spectroscopy measurements together with systematic CVD studies reveal that the substrate temperature, selenium partial pressure, and the substrate type ultimately dictate the resulting stoichiometry and phase of these materials. Results from this work introduce the phase control of Ge and Se based nanomaterials (GeSe and GeSe₂) using halide based CVD precursors at ATM pressures and low temperatures. Overall findings also extend our fundamental understanding of their growth by making the first attempt to correlate growth parameters to resulting competing phases of Ge-Se based materials.