RESUMO
The transition-metal chalcogenides include some of the most important and ubiquitous families of 2D materials. They host an exceptional variety of electronic and collective states, which can in principle be readily tuned by combining different compounds in van der Waals heterostructures. Achieving this, however, presents a significant materials challenge. The highest quality heterostructures are usually fabricated by stacking layers exfoliated from bulk crystals, which - while producing excellent prototype devices - is time consuming, cannot be easily scaled, and can lead to significant complications for materials stability and contamination. Growth via the ultra-high vacuum deposition technique of molecular-beam epitaxy (MBE) should be a premier route for 2D heterostructure fabrication, but efforts to achieve this have been complicated by non-uniform layer coverage, unfavourable growth morphologies, and the presence of significant rotational disorder of the grown epilayer. This work demonstrates a dramatic enhancement in the quality of MBE grown 2D materials by exploiting simultaneous deposition of a sacrificial species from an electron-beam evaporator during the growth. This approach dramatically enhances the nucleation of the desired epi-layer, in turn enabling the synthesis of large-area, uniform monolayers with enhanced quasiparticle lifetimes, and facilitating the growth of epitaxial van der Waals heterostructures. This article is protected by copyright. All rights reserved.
