Controllable Synthesis of Vertically Aligned ReS2(1-x)Se2x Nanosheets with Tunable Chemical Compositions and Bandgaps

2D transition metal dichalcogenides (TMDs) have been extensively studied in recent years because of their appealing electrical and optical properties. Both morphology control and bandgap modulation of TMD alloys are critical for their applications in optoelectronics, photonics and nanoelectronics. In this work, the synthesis of vertically aligned ReS2(1-x)Se2x alloy nanosheets with tunable compositions on SiO2/Si substrate was achieved via CVD technology. The resulting ReS2(1-x)Se2x nanosheets were obtained by selenizing the vertically aligned ReS2 nanosheets at various temperatures for different durations. The ReS2(1-x)Se2x samples were characterized by XRD, SEM, XPS, HRTEM, elemental mapping, Raman spectra, and UV-Vis-NIR absorption spectra. Experimental results showed that the Se contents in ReS2(1-x)Se2x nanosheets can be gradually tuned from x=0 (pure ReS2) to x=0.86, and the bandgaps of the products were correspondingly modulated from 1.55 eV (800 nm) to 1.28 eV (969 nm). Moreover, the temperature and duration of selenization have huge effect on the morphology of the resulting ReS2(1-x)Se2x, alloyed nanosheets, as evidenced by SEM observation. The vertical ReS2(1-x)Se2x alloy nanosheets may have significant application potential, e. g. , in the electrochemical catalysis, functional electeonic and optoelectronic devices.