Speeding-up effects of hard carbon films on surface acoustic wave on crystalline quartz

Hard diamond-like carbon (DLC) films and tetrahedral amorphous carbon (Ta-C ) films have been deposited on X-Y cut quartz substrates. The 1-mum-thick D LC films prepared by a plasma enhanced CVD system possess typical Young's m odulus (and hardness) of approximately 150 (19) GPa, whereas the 0.12-mum-t hick Ta-C films grown using filtered cathodic vacuum arc technique have a Y oung's modulus (and hardness) of 340 (38) GPa. Velocity tests of surface ac oustic wave (SAW) were performed by introducing SAW into two delay lines on the quartz; one coated with the carbon films and the other free of the fil ms. It has been confirmed that the DLC and Ta-C films speed up SAW by 2.3% and 3.4%. respectively. These findings are interpreted in terms of the film properties. (C) 2001 Elsevier Science B.V. All rights reserved.