| 摘要 |
PROBLEM TO BE SOLVED: To provide a diamond substrate for a surface acoustic wave element and the surface acoustic element comprising a diamond thin film that has a large propagation velocity of a surface acoustic wave and a small propagation loss to achieve a surface acoustic wave element having a good frequency response. SOLUTION: A filament CVD process is used to form a diamond thin film 240 having a thickness of 20μm on a silicon wafer 220. In this process, an adjustment is made so that the ratio I<SB>(220)</SB>/IT is 0.8 or more, wherein I<SB>(220)</SB>refers to the peak intensity for the diamond crystal face (220) and IT refers to the sum of the peak intensities for the diamond crystal faces (111), (220), (311), (400) and (331), when the diamond thin film 240 is measured by X-ray diffraction, and a hydrogen content in the diamond thin film 240 is in the range 1%-5%, by atomic percent. The diamond thin film is smoothed by a mechanical polishing using a grindstone containing diamond abrasive grains so that the arithmetical mean roughness (Ra) of the surface is 20 nm or less. COPYRIGHT: (C)2003,JPO
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