Mitigation of Structural Defects during the Growth of 2D van der Waals Chalcogenides by Molecular Beam Epitaxy

The growth of wafer-scale van der Waals (vdW) thin films and heterostructures by molecular beam epitaxy (MBE) is important for future applications in quantum technologies, next-generation optoelectronic devices, and fundamental physics investigations. When grown using co-deposition methods that are typically used for compound semiconductor MBE, vdW materials typically show a high density of structural defects, including twin or antiphase domains, spiral growth, and pyramidal growth. These defects are caused by the relatively weak film/substrate interaction and/or the poor wettability of typical substrates by many vdW materials. These difficulties can be mitigated using a multi-step growth procedure in which growth stages, including nucleation and coalescence, can be rigorously controlled, resulting in high-quality deposition of vdW thin films. This article will describe a general recipe for the growth of highly-crystalline wafer-scale vdW thin films by MBE.