Controllable growth of large-area monolayer ReS₂ flakes by chemical vapor deposition

Two-dimensional (2D) ReS₂ flakes are synthesized by the chemical vapor deposition under atmospheric pressure using Re–Te binary eutectic and sulfur as precursors. The morphologies, crystal structure, phonon vibration modes, chemical states and optical property of the 2D ReS₂ flakes are characterized using optical microscopy, scanning electron microscope, transmission electron microscopy, the Raman spectroscopy, X-ray photoelectron spectroscopy and transmittance spectra. The lateral size of 2D ReS₂ flakes can be tuned via changing the synthesis parameters. The monolayer 2D ReS₂ flakes is single crystal structure. Its maximum lateral size is 30 μm, and optical band gap is 1.42 eV. The absorption coefficient is as large as 10⁵ cm⁻¹, transmittance of 92–98% and refractive index of 1.5–1.3 in the wavelength range from 400 to 800 nm. The effect of synthesis parameters on the morphologies and growth mechanism of 2D ReS₂ flakes are investigated in detail. This is helpful for further application of ReS₂ in electronic and optoelectronic devices.