Atomic structure of interfaces in van der Waals epitaxial nitrides on graphene
Peng Gao(1),(2), Tongbo Wei(3), Zhiqiang Liu(3),(4), Zhongfan Liu(2),(5)
(1).Electron Microscopy Laboratory, and International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China.
(2).Beijing graphene institute (BGI), Beijing 100095, China.
(3).State Key Laboratory of Solid-State Lighting, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China.
(4).Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China.
(5).Center for Nanochemistry (CNC), Beijing Science and Engineering Center for Nanocarbons, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China.
E-mail: p-gao@pku.edu.cn
Recently, two-dimensional materials such as graphene has been employed to act as a buffer/ sacrifice layer to growth group-III nitrides (III-Ns). The advantage of weak van der Waals interactions between nitrides and two-dimensional materials enables to alleviate the lattice and thermal mismatch between substrate and epilayer, tune nucleation behavior, reduce growth time, and/or achieve damage-free transfer for high-power and flexible optoelectronics and electronics devices. Despite significant progress has been made in the nitride film growth and device fabrication, the role of two-dimensional materials in such systems is far from clear. In this talk, we share some insights obtained from the atomical resolution characterization of the microstructures of interfaces in such van der Waals epitaxial growth systems. We study the interface between graphene and sapphire substrate [1] and find that unexpected C-O-Al bond, which causes non-van der Waals interaction at the interface and different structural relaxation behavior of the sapphire surface. After growth of the nitrides, we also revealed the atomic structures of nitrides-graphene-sapphire interfaces and observed unusual structural distortions. These observations are helpful for us to understand the what role the graphene plays and how we should better take the advantages of van der Waals interactions.
Fig.1 (a-b) Atomic structure of the Gr/α-Al2O3 interface. (c-d) Mechanical properties. (e) Sturctural relaxation of sapphire.
[1] Dou et al., Nature Communications 10, 5013 (2019)
