Abstract:

Epitaxial graphene is an excellent platform for future high performance nanoelectronics and fundamental transport studies.  However, due to its pristine crystalline surface, nearly free of dangling bonds, integrating dielectric and semiconducting materials into the epitaxial graphene system is challenging.  High-K metal oxides, such as Al₂O₃, have been widely investigated as a top gate; yet, despite innovative surface treatments and deposition techniques, metal oxide top gates reduce graphene transport performance and reliability.  Crystalline 2D materials, such as hexagonal boron nitride (hBN), have promised to overcome many of the challenges associated with metal oxides on graphene surfaces due to weak interlayer interactions.  Transferred 2D layers enable arbitrary stacking, but impart charged impurities at the interface and are not compatible with precise lattice alignment, making the technology ill-suited for high performance electronics.  Direct deposition of heterostructures is required.  To date, several attempts have been made to directly grow epitaxial hBN/graphene heterostructures, but none display long range order at the critical graphene interface.  This work demonstrates a pristine interface between epitaxial graphene and hBN using a commercially available deposition system.  The refractory SiC substrate and high-quality graphene surface support a novel lateral atomic deposition process (LAD) to selectively grow 2D hBN on graphene surfaces. LAD is the 2D analog of atomic layer deposition technology where, ideally, a single row of atoms is deposited for each cycle, compared to a monolayer in ALD.  The structure of the hBN/epitaxial graphene is confirmed with HRTEM, XPS, EELS, and HRXRD.