Heat treatment of thin carbon films and the effect on residual stress, modulus, thermal expansion and microstructure

• Published in: Carbon (New York) Vol. 41; no. 10; pp. 1867 - 1875
• Main Authors: Taylor, Craig A., Wayne, Mark F., Chiu, Wilson K.S.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 2003; Elsevier Science
• Subjects: A. Pyrolytic carbon; B. Heat treatment; C. Raman spectroscopy; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; D. Elastic properties; Exact sciences and technology; Fullerenes and related materials; diamonds, graphite; Materials science; Mechanical and acoustical properties; Physical properties of thin films, nonelectronic; Physics; Specific materials; Structure and morphology; thickness; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Thin film structure and morphology; C. Raman spectroscopy; D. Elastic properties; A. Pyrolytic carbon; B. Heat treatment; Scanning electron microscopy; Elastic modulus; Raman spectra; Films; Mechanical properties; Pyrolytic carbon; Residual stresses; Experimental study; Carbon; Heat treatments; Thin films; Nonmetals; Elastic properties
• ISSN: 0008-6223; 1873-3891
• DOI: 10.1016/S0008-6223(03)00181-7

Thin carbon films are used to hermetically seal and improve the performance of devices exposed to extreme conditions. Such films, which are deposited by chemical vapor deposition, develop residual thermal stresses due to a mismatch in the coefficient of thermal expansion between the film and substrate. Residual stresses reduce the adhesion of the film, and are a common cause of coating failure. This work investigates heat treatment as a potential technique to reduce residual stresses in thin carbon films. The magnitude of the residual stress has been challenging to measure due to the associated size scales and mechanical properties. In this study, experimental measurements of mechanical properties and residual stresses in thin carbon films are performed using nanoindentation and Raman spectroscopy. The results relate surface residual stresses to film thickness and heat treatment temperature. The approach presented in this study is a nondestructive and non-intrusive method for measuring residual surface stress and properties in thin films, and is ideal for small or curved-surface specimens such as optical fibers and other photonic devices.