Catalyst-Free Growth of multi-layer h-BN on Sapphire Substrate

Hexagonal boron nitride (h-BN) has been regarded as a good substrate for twodimensional (2D) material based electronic, because ultra-flatness of h-BN surface can reduce the substrate-induce degradation in carrier mobility of 2D materials. Therefore, various approaches have been attempted for the large area growth of high-quality h-BN on metal substrate. However h-BN synthesized on metal substrate need to be transferred onto the other insulating substrate for device applications, as well as this process generally induces wrinkle formation on the surface. Hence, direct growth of h-BN on insulating substrate is promising for the transfer-free process. Herein, we present the catalyst free growth of multi-layer h-BN sheet on insulating sapphire substrate by low pressure chemical vapor deposition method. The surface roughness of synthesized multilayer h-BN on sapphire substrate was measured as ~0.168 nm, and an optical band gap was estimated as 5.65 eV from UV visible absorption spectroscopy