photo-chemical conversion of layered transition metal ditellurides*

WTe₂ and MoTe₂ are good candidates for spintronics, thermoelectric and piezoelectric applications. In general, the 1T`phase of these 2D materials displays metallic behavior, making them interesting candidates for in-plane interconnects when combined with 2D semiconductors. In this study, we synthesize large-area WTe₂ and MoTe₂ films using a simple CVD process. Raman spectroscopy and TEM were used to study the crystal quality as well as phase and chemical composition. Subsequently, the as-grown films were chemically modified using an in situ laser-assisted method recently developed in our group. The entire process takes place within a home-made mini-chamber with an optical quartz window, were the samples are exposed to a laser beam in the presence of a controlled environment rich in a different chalcogen atom (sulfur in this case). For an optimized set of parameters (e.g. exposure time and laser power), the tellurium atoms are replaced by sulfur atoms and the chemical exchange process is monitored in real time via Raman spectroscopy. The site-selective replacement of the chalcogen atoms generate metal-semiconductor heterojunctions. FET-like devices where fabricated to study the electrical response of these junctions.