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Structural features of thick c-boron nitride coatings deposited via a graded B-C-N interlayer

 
: Yamamoto, K.; Keunecke, M.; Bewilogua, K.; Czigany, Z.; Hultman, L.

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Surface and coatings technology 142-144 (2001), pp.881-888
ISSN: 0257-8972
English
Journal Article
Fraunhofer IST ()
c-boron nitride film; si-substrate; graded interlayer; structural feature

Abstract
Thick c-BN films (up to 2.7 m) were deposited onto Si substrates by an r. f. diode apparatus using boron carbide (B4C) targets. The c-BN films were deposited on a compositionally graded interlayer, which consisted of B, C and N. A thin B4C layer (~200 nm) had been initially deposited onto Si substrate in a pure Ar gas discharge. The following formation of the graded interlayer was conducted by step-like or smoothly replacing Ar with N2 gas. Depending on the method implemented, the secondary ion mass spectroscopy (SIMS) depth profile showed relatively smooth or step-like changes in the elemental concentration of B, C and N. The primary analysis on the chemical bond of the graded interlayer was conducted by measuring the chemical shift of B1s, C1s and N1s spectra by X-ray photoelectron spectrometry (XPS). It is shown that the B-C bond, which was a major bonding component in the B4C layer, was gradually replaced by a mixture of B-N and C-C bond as the N2 fraction was increased. Transmission electron microscopy (TEM) images of the gradient layer showed that (0002) oriented turbostratic BN (t-BN) structure started to appear after the N2 concentration was increased by more than 2 %. It was also observed that the c-BN phase nucleated non-uniformly in the gradient layer at 1 % of N2 fraction.

: http://publica.fraunhofer.de/documents/N-7180.html