The formation of epitaxial hexagonal boron nitride on nickel substrates
The various crystallographic forms of boron nitride (BN) are of great technological interest because of their demonstrated tribological, high-temperature, thermally conducting, electrically insulating, and wide-bandgap semiconductor properties. Unfortunately, the synthesis of crystalline BN films is still in the early stages of development. Furthermore, although polycrystalline BN films have been prepared by a variety of physical and chemical vapor deposition techniques, the capability does not currently exist for depositing large area single-crystal or oriented films of BN. Such single-crystal films are required for many applications of interest, especially in electronics. The present paper reports on a new approach to the oriented growth of boron nitride using a novel molten layer epitaxy technique. Well-oriented hexagonal boron nitride (h-BN) crystals were obtained with highly faceted crystal shapes. The h-BN was formed via precipitation from a molten, hydrogen-saturated Ni surface layer. Solid cubic BN was utilized as the source material and was dissolved into the substrate surface during a brief high-temperature anneal. It was found that surface melting occurred during this process and the B diffused into the Ni substrate, whereas the N was expelled into the growth chamber. Oriented BN was then precipitated as the surface layer was allowed to resolidify.
Yang, PC; Prater, JT; Liu, W; Glass, JT; Davis, RF
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