ULTRA HARD COATINGS
Diamond is not only the hardest material known to man it also has a number of other remarkable properties including a very high thermal conductivity (approximately four times that of copper), high chemical innertness, very low electrical conductivity and, when properly prepared, very low surface friction comparable to TEFLON. Most remarkable of all, however, is the fact that diamond can be created as a thin or thick coating at low pressure and high temperature using plasma enhanced chemical vapor deposition (PECVD) methods. With these properties diamond coatings can achieve exceptional levels of performance in a wide variety of applications including:
The potential uses for diamond coatings are virtually unlimited yet as of this time relatively few applications have come to fruition mainly due to technical issues associated with achieving stable coatings on commercially useful surfaces.
With all of its remarkable properties and outstanding applications one has to wonder why diamond coatings are not already in wide use throughout industry. The primary reason for this is the difficulty in achieving stable coatings on surfaces of commercial interest. At present diamond coatings have been successfully applied to a limited range of materials known as the "refractories" which already have physical properties approaching that of diamond. These materials include single crystal silicon, silicon carbide, silicon nitride and similar compounds of tungsten. However, when one attempts to coat diamond onto common surfaces such as ferrous metals severe problems arise due to physical-chemical incompatibilities. Without careful surface preparation, nucleation of the diamond growth process will fail and no coating will be achieved. Also, even if this problem can be overcome the resulting coating will have very poor adhesion and will quickly delaminate. Finally, even assuming that the interface incompatibility problem can be solved, the resulting coating is still compromised by high levels of intrinsic stress. All of these difficulties result in coatings of marginal quality which must be kept very thin.
The staff of MST have spent their careers in the microelectronics industry solving the very problems which prevent the successful implementation of diamond coatings. Problems of adhesion and interface compatibility commonly arise when trying to build multilevel wiring structures using insulators, metals and and semiconductor materials. C4 has carried its expertise from the field of microelectronics to that of diamond coatings and has determined effective processes for achieving compatibility of diamond with ferrous metal substrates. In addition, C4 has developed methods for controlling the level of stress buildup in diamond coatings which has led to a patented process for coating diamond onto ferrous metals. Details on the MST approach to controlling stress driven failure modes in coatings is outline in the following case study.
Case study: Diamond coatings on metal 
Copyright © 2004 MST CONFERENCES,LLC
Revised --
URL: http://ourworld.compuserve.com/homepages/rhlacombe/carbonc.htm