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The effect of microstructure on residual stress in diamond thin film was investigated. The diamond thin film was deposited by the hot filament chemical vapor deposition process with hydrogen/methane precursor gas and followed by annealing at 1150 °C for 1–30 min. The residual stresses of the diamond thin film were measured by Raman spectroscopy. A model to estimate the residual stress was proposed on the basis of grain boundary relaxation mechanism and microstructural analysis of diamond thin film. It is confirmed that the residual stress in diamond thin film is proportional to a microstructural factor, 1/ [D( f + 1)]1/2, where D is the grain size of diamond and f is the volume ratio of nondiamond carbon/diamond.

I. INTRODUCTION

In recent years, diamond thin film has been the most promising material in various fields of industry and science because of the outstanding properties of diamond such as high thermal conductivity, low electric conductivity, high wear resistance, and wide band gap. Moreover, the application areas become even broader with the advance of diamond deposition technology at low pressure. In spite of these numerous potential application areas, the issues on the residual stress in diamond thin film have not been clearly understood. Numerous researchers have been investigating the measurement and analysis of residual stress in diamond thin film.1–9 Windischmann et al.1 investigated the residual stress of diamond thin film by the curvature measurement technique based on Stoney’s equation. They measured the variation of residual stress in diamond thin film deposited by microwave plasma chemical vapor deposition (MPCVD) process according to the substrate temperature and methane volume fraction in precursor gas. Their analysis stated that the nondiamond carbon and hydrogen impurities in diamond thin film induced the compressive residual stress and grain size refinements, increasing tensile residual stress by the grain boundary relaxation mechanism. Chalker et al.3 investigated the residual stress of diamond thin film deposited by the hot-filament chemical vapor deposition (HFCVD) process by x-ray diffraction (XRD). They reported that the residual tensile stress is caused by the misfit stress at the interface between diamond and substrate. Chiou4 explained that the grain boundary caused tensile residual stress in diamond J. Mater. Res., Vol. 16, No. 7, Jul 2001

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thin film. Kuo et al. 5 found that the presence of nondiamond carbon within the diamond lattice induced the compressive stresses. Schwarzbach et al.8 and Baglio et al.6 issued grain size effects on the residual stress. It is generally accepted that the tensile stress increases with decreasing grain size by the grain boundary relaxation mechanisms, and the nondiamond carbon induces compressive stress in diamond thin film. However, in spite of the understanding about the origin of residual stresses in diamond thin film, the quantitative analyses to estimate the residual stress in diamond thi