The formation of epitaxial hexagonal boron nitride on nickel substrates

Abstract

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.

Low‐Temperature Synthesis and Growth of Hexagonal Boron‐Nitride in a Lithium Bromide Melt

“…It is interesting because it opened an avenue toward soft growth of refractory nitrides in solution. The crystallization at low temperature in metal fluxes, such as in sodium at 700°–800°C 27,28 and in molten hydrogen‐saturated nickel below 1000°C, 29 has been reported. Moreover, the synthesis and growth of different shapes of hBN nanocrystals at 350°C in organic solution have also been reported 30 …”

Facile Synthesis of Highly Crystalline and Large Areal Hexagonal Boron Nitride from Borazine Oligomers

“…Crystallization of the 2-dimensional structures into h-BN on Ni catalyst might not be same to the metal induced crystallization (MIC) of amorphous carbon into graphite or graphene, where carbon soluble metal catalysts such as Ni and Co were used. The dissolution-precipitation mechanism that governed the crystallization of amorphous carbon cannot be adapted to that of polyborazylene because Ni has 0.3 at.% solubility of boron at 1085 °C and almost zero solubility of nitrogen above 445 °C32. Though boron can be dissolved into Ni catalyst considering its solubility, boron atoms within the cross-linked 2-dimensional BN structures formed during initial growth cannot be dissolved in Ni catalyst due to the strong bonds between boron and nitrogen.…”

Chemical Vapor Deposition of Hexagonal Boron Nitride

“…• C [31]), N solubility has been reported to be almost zero in molten Ni [31] and ∼ 0.005 at.% even at an extremely high temperature of 1600…”