Effects of Growth Parameters on the Morphology of ReS₂ Nanoflakes Prepared by Chemical Vapor Deposition

The development of efficient ReS<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>-based optoelectronic devices depends on the ability to synthesize high-quality nanoflakes with the desired morphology. In this work, we report the synthesis of ReS<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> nanoflakes with vertical and horizontal orientations via chemical vapor deposition (CVD) on SiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>/Si substrates at atmospheric pressure. The ReS<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> samples were grown using rhenium trioxide (ReO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf>) and sulfur precursors. It was found that growth temperature and ReO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf>-substrate distance significantly influenced the nucleation density and morphology of the ReS<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> flakes, as observed by optical and field-emission scanning electron microscope images. High Re vapor environment favors the formation of vertical flakes. The growth then switches to a mixture of both vertical and horizontal flakes as the Re concentration decreases. Raman spectroscopy data show the characteristic Eg and Cp vibrational modes which belong to the ReS<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>. The full-width-at-half-maximum of the 210.3 cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> peak is 8 cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> which is comparable to the high-quality ReS<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> flakes prepared by mechanical exfoliation. This work provides valuable insights on the effect of CVD parameters on the growth and morphology of ReS<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> nanoflakes.