Pulsed thermal deposition of binary and ternary transition metal dichalcogenide monolayers and heterostructures

Application of transition metal dichalcogenides (TMDC) in photonic, optoelectronic or valleytronic devices requires the growth of continuous monolayers, heterostructures and alloys of different materials in a single process. We present a facile pulsed thermal deposition method which provides precise control over layer thickness and stoichiometry of two-dimensional systems. The versatility of the method is demonstrated on ternary monolayers of Mo$_{1-x}$W$_{x}$S$_{2}$ and on heterostructures combining metallic TaS$_{2}$ and semiconducting MoS$_{2}$ layers. The fabricated ternary monolayers cover the entire composition range of $x$ = 0...1 without phase separation. Band gap engineering and control over the spin-orbit coupling strength is demonstrated by absorption and photoluminescence spectroscopy. Vertical heterostructures are grown without intermixing. The formation of clean and atomically abrupt interfaces is evidenced by high-resolution transmission electron microscopy. Since both the metal components as well as the chalcogenides are thermally evaporated complex alloys and heterostructures can thus be prepared.