K.L. Ma

Photoemission spectroscopic study of nitrogen-incorporated nanocrystalline diamond films

The variation of composition and chemical bonding structures of the nanocrystalline diamond (ND) films induced by nitrogen incorporation in CH4(10%)∕H2∕N2 plasmas was investigated by x-ray photoelectron spectroscopy. The sp2∕sp3 phase ratio of hybridized carbon bonds in ND films was shown to depend strongly on the nitrogen concentration in plasma, coinciding with Raman observations. The depth profile analysis, however, revealed only about 1at.% of nitrogen in all samples, suggesting that the variation of conductivity of ND films is mainly associated with the development of highly ordered graphitic sp2 phase induced by the nitrogen incorporation.

Nanocubic boron nitride/nanodiamond multilayer structures

Nanocubic boron nitride/nanodiamond (N-cBN/ND) multilayer structures with each alternating layer being ∼100nm thick have been prepared by magnetron sputter and microwave plasma enhanced chemical vapor depositions. These multilayers exhibit remarkable properties, in particular, the mechanical properties. The multilayer structure is characteristic with (i) extreme hardness (82GPa) considerably surpassing the values of the individual materials from which the multilayer is composed, (ii) high surface smoothness, (iii) significantly reduced film stress when compared with a single cBN layer of equivalent thickness, and (iv) great chemical stability. The N-cBN/ND multilayers developed have therefore important implications in mechanical and chemically resistant applications.

Structural analysis of cubic boron nitride films by ultraviolet raman spectroscopy

Cubic boron nitride (BN) films with improved crystallinity are deposited by physical vapor deposition at an extremely low substrate bias (−35V). The films are characterized by UV Raman in association with Fourier transformed infrared (FTIR) spectroscopy. The influences of bias voltage and film thickness on the characterizations are investigated. UV Raman, in contrast to FTIR, is demonstrated to be a more powerful tool with high sensitivity for quantitative and/or qualitative evaluation of the phase purity and crystallinity, especially as the film thickness increases. Hexagonal BN inclusions (less than 1%), not evident in FTIR, are clearly revealed by UV Raman analysis.