Models of cBN Formation

An important and typical experimental result is the strong biaxial compressive stress which is always found in cBN thin film. The stress usually has values of 4-lOGPa which is high enough to cause serious adhesion problems as soon as the film thickness exceed a few 100 nm. In fact, bad film adhesion is the most important obstacle in making cBN ready for application. 

Most cBN deposition experiments reported so far were carried with silicon substrates. Only a few papers concerned non-silicon substrates. Mirkarimi et al. [46] used different metallic substrates and found a decrease of the cBN content with decreasing metal hardness. Schiitze et al. [47] found that it is not possible to deposit cBN films on steel substrates under conditions which are suitable for silicon substrates. On steel cBN could only be prepared after deposition of a high-density hBN buffer layer. Concerning the effect of the substrate material on the cBN film growth there are still a lot of open questions. 

The authors back up their model by experimental results. For instance they have varied the conditions for boron nitride thin film deposition which yielded different 

5 Vapor Phase Deposition of Cubic Boron Nitride Films 

In addition, based on their ion impact approach, Mirkarimi et al. [17] established a quantitative model of defect generation during ion-assisted film growth. They found that the maximum height of the defect production distribution exhibits the same (mion ion) dependence as cBN formation. Moreover, as the authors emphasize, this is the very same dependence as that found by Windischmann [51] for the formation of intrinsic compressive stress in thin films deposited under ion bombardment. 

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