Effects of substrate temperature and precursor separation on the morphology of ReSnanoflakes prepared by chemical vapor deposition.

Rhenium disulfide (ReS) is a 2-dimensional transitional metal dichalcogenides that exhibits unique properties such as a direct band gap irrespective of thickness, weak interlayer coupling, and exceptional anisotropic properties, making it a promising material for optoelectronics applications. In this work, we synthesized ReSnanoflakes on SiO/Si substrates using chemical vapor deposition (CVD). The effects of Re precursor-substrate distance () and growth temperature on flakes morphology were systematically investigated. Field-effect scanning electron microscopy images revealed that shorter Re precursor-substrate distance (= 8 cm) favored the formation of high density and vertical flakes due to the high concentration of Re vapor. However, samples grown with the largest separation distance (= 11 cm) and higher substrate temperature (850 °C) demonstrated a low density of planar flakes. Raman spectroscopy measurements showed the,, andvibrational modes which belong to ReS. The full-width-at-half-maximum of themode at 212 cmis 6.7 cm, comparable to the mechanically exfoliated ReSreference. The thicknesses of the flakes range from bilayer to multilayer and the measured band gap energy is ∼1.57 eV. The XPS data verified that the atomic ratio between Re and S is 1.9, which confirms the stoichiometry of the ReSflakes. Finally, the TEM images and diffraction pattern confirmed that the ReSflake is a single-crystal with distorted 1 T-phase. This work emphasizes the influence of CVD parameters on the morphology of ReSflakes, which is vital for developing high performance ReSbased optoelectronics devices.