Residual Stresses in Mo2C/Diamond Coatings
	Users and Staff Arthur J. McGinnis and K. Jagannadham, North Carolina State University Thomas R. Watkins, ORNL Background Diamond has the highest known thermal conductivity as well as high hardness Interest exists to utilize diamond coatings in various applications such as heat spreaders in electronic device Utilization of these coatings can be limited by poor adhesion due in part to residual stresses Insertion of an appropriate intermediate layer between the coating and substrate can be used to reduce the residual stresses arising from thermal expansion mismatch X-ray diffraction and Raman spectroscopy were used to characterize the residual stresses Results Multilayer coating processing: A layer of diamond islands deposited via hot filament CVD; Mo2C also formed by carburization of Mo during this deposition Interposing layer of AlN deposited via pulsed laser PVD Coating polished until the underlying layer of diamond islands was exposed A continuous top layer of diamond deposited Hydrostatic stresses measured by X-ray diffraction and Macro-Raman spectroscopy. Sample Diamond Layer Thickness (µm) Mean Hydrostatic Stress (GPa) (321) Mo# (213) Mo2C# Diamond´ Multilayer Coating 5 - 0.07 (0.06)* 0.49 (0.06) -4.5 Single layer Diamond 8.5 - 0.08 (0.07) 0.53 (0.05) -4.5  #     X-ray diffraction  ´     Macro Raman data  *( )  Denotes standard deviation Sign of residual stresses consistent with thermal expansion mismatch. Current results indicate no stress reduction benefit of interposing AlN layer despite the observed improvement in adhesion (i.e., lack of delamination). Publication A. J. McGinnis, T. R. Watkins and K. Jagannadham, "Residual Stresses in a Multilayer System of Coatings," in preparation for Advances in X-ray Analysis, V. 41., 1998.
	Instruments | Applications | Recent Projects | Publications | Staff  User Facility Access and Proposal Form Diffraction UC | Residual Stress UC | Thermophysical Properties UC Diffraction & Thermophysical Prop. Group | High Temperature Materials Laboratory Metals & Ceramics Division | Oak Ridge National Laboratory Acknowledgments URL: http://www.html.ornl.gov/rsuc/diam.html