Two-dimensional materials have emerged as promising candidates for next-generation electronic and optoelectronic applications . With electronic properties spanning the spectrum from insulating (e.g., hexagonal boron nitride and montmorillonite) to semiconducting (e.g., transition metal dichalcogenides and phosphorene) to conducting (e.g., graphene and borophene), nearly any electronic device can be fabricated by stacking two-dimensional materials into heterostructures . However, in the atomically thin limit, the influence of surface chemistry, defects, interfaces, and the surrounding environment play an important if not dominant role, especially in comparison to bulk materials . Consequently, methods for controlling and characterizing heterostructure interfaces with atomic precision are critical steps in the realization of the full technological potential of two-dimensional materials. Towards this end, this talk will outline the latest efforts in our laboratory to engineer surfaces and interfaces in two-dimensional heterostructures. For example, lateral and vertical heterostructure interfaces between graphene and silicon have been prepared and characterized using atomic-resolution scanning tunneling microscopy and spectroscopy in ultra-high vacuum [4,5]. Similarly, rotationally commensurate heterostructures between graphene and MoS2 have been realized through chemical vapor deposition growth on epitaxial graphene on SiC substrates [6,7]. Finally, this talk will address methods for encapsulating and passivating phosphorene [8,9] and borophene [10,11], which are emerging elemental two-dimensional materials with high surface chemical reactivity.
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