Epitaxial Growth of Hexagonal Boron Nitride on Sapphire Surfaces by Metal-organic Chemical Vapor Deposition

Abstract

Hexagonal boron nitride (h-BN) is a two-dimensional (2D) material with unique properties, making it crucial for next-generation photonics and optoelectronics. Despite its potential, achieving high-crystalline and large-area growth of h-BN films remains challenging due to non-uniform nucleation and random domain orientations on substrate surfaces, which increase grain boundaries. Furthermore, lattice mismatch between h-BN and the substrate surface causes structural distortions in the thin films, leading to a degradation in crystallinity. Therefore, to develop high-crystalline and large-area h-BN films for next- generation photonics and optoelectronics applications, it is essential to study the impact of substrate surface characteristics on the growth of h-BN. In this study, we investigated the effects of sapphire substrate surface characteristics on the epitaxial growth of h-BN. By annealing the sapphire substrates, we fabricated step-terrace morphology and improved surface characteristics, using both C-plane and A-plane sapphire to understand the impact of crystallographic orientation. We successfully grew uniform h-BN thin films on 2-inch sapphire substrates using metal-organic chemical vapor deposition (MOCVD). Comprehensive spectroscopic and diffraction analyses demonstrated that high-crystalline h-BN with well-aligned domains was epitaxially grown on sapphire surfaces. The improvement in surface characteristics through annealing significantly enhanced the crystallinity of the h-BN films, and our results suggest that A-plane sapphire surfaces are promising candidates for the epitaxial growth of h-BN. These findings highlight the potential of sapphire substrates for high- crystalline h-BN growth, offering valuable insights for advancing photonic and optoelectronic applications. This study not only demonstrates the effectiveness of sapphire substrates for h-BN growth but also contributes to the broader understanding of epitaxial growth for 2D materials. Furthermore, it can pave the way for developing high-performance 2D material-based devices.