Effect of the geometry of precursor crucibles on the growth of MoS2 flakes by chemical vapor deposition

Abstract

Chemical vapor deposition (CVD) employing a furnace with multiple temperature zones is still the best and most widely used method for preparing high-quality MoS₂ flakes. In this work, MoO₃ powder was chosen as the molybdenum precursor to explore the influence of the size of boat crucibles holding molybdenum precursors on the morphology of resultant MoS₂ crystals. It is found that shorter or open-ended boat crucibles are not favorable for the reaction between the vapor of sulfur and molybdenum precursors, i.e. no MoS₂ crystals can be produced under these conditions. In contrast, the use of longer boat crucibles as the precursor carrier facilitates the growth of triangular MoS₂ crystals. Furthermore, the width of the boat crucibles was also found to have a substantial impact on the structural and optical properties of the as-grown MoS₂ crystals. More monolayers, regular shapes, uniform surfaces and better optical properties were evident in MoS₂ crystals prepared using narrower boat crucibles, as confirmed by the results of the atomic force microscopy (AFM), Raman spectroscopy and photoluminescence (PL). This work clarifies the critical role of the geometry of the molybdenum precursor container and suggests a facile yet efficient way for obtaining monolayer high-quality MoS₂ crystals by the CVD technique.