Influence of growth parameters on the morphology of transition metal dichalcogenides films

Transition metal dichalcogenides (TMDs) have been widely investigated for their potential in microelectronic technologies and a broad range of applications [1]. Two-dimensional TMDs (2D-TMDs), such as MoS₂ and WS₂, are the most studied materials of this class, which stand out due to its interesting electronic and optical properties, offering a direct band gap in the monolayer form. The most employed method to synthesize TMDs is chemical vapor deposition (CVD), where solid precursors (MoO₃ or WO₃ and sulfur) are individually heated under a carrier gas flow. Crystal formation is often evidenced by the appearance of triangular domains under optical microscopy. Controlling film growth is crucial for overcoming the dimensional limitations of monolayer films and enabling large-scale applications. One way to reduce the number of growth parameters is the use of silicon substrates with pre-deposited metal precursors, forming a molten liquid intermediated during synthesis [2]. With this vapour-solid-liquid (VLS) growth methodology, the morphology of the obtained material varies from triangular domains to a continuous film as a function of the growth parameters. The present work aims to investigate which parameters have influence in the growth process and to understand the mechanisms underlying the VLS method. Samples were characterized using Rutherford Backscattering Spectrometry (RBS), Optical Microscopy, X-ray Photoelectron Spectroscopy (XPS), Raman Spectroscopy, and Photoluminescence (PL). Results obtained so far indicate that prolonged high temperature steps in the growth process, induces material loss from the already grown TMD crystal.