, Volume 21, Issue 2, pp 649-658

Synthesis and structure of chemically vapour-deposited boron nitride

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Abstract

Chemically vapour-deposited boron nitride (CVD-BN) plates have been synthesized on a graphite substrate by the reaction of the BCl3-NH3-H2 gas system in a deposition temperature (T dep) range from 1200 to 2000° C, with a total gas pressure (P tot) which was varied from 5 to 60 torr. The effects ofP tot andT dep on the crystal structure and the microstructure of the CVD-BN plate were investigated. Turbostratic BN(t-BN) was deposited above 10 torr, at anyT dep in the range investigated. The interlayer spacing (c 0/2), the crystallite size (Lc) and the preferred orientation (PO) were strongly affected byT dep. The t-BN obtained at lowT dep had largec 0/2 and smallLc andPO. AsT dep increased,c 0/2 tended to decrease whereasLc increased and thec-plane of the crystallites became oriented parallel to the deposition surface. At aP tot of 5 torr, a mixture of t-BN and h-BN (hexagonal BN) was deposited at anyT dep above 1700° C, and two kinds of t-BN different inc 0/2 co-deposited at aT dep below 1600° C. Moreover, it was indicated that r-BN (rhombohedral BN) was included in the deposits obtained at aP tot of 5 torr and aT dep of 1500 to 1600° C.