Synthesis and surface acoustic wave property of aluminum nitride thin films fabricated on silicon and diamond substrates using the sputtering method

C-axis oriented aluminum nitride (AIN) thin films with a thickness of 1 mum were prepared by reactive DC magnetron sputtering on polycrystalline diamond substrates at a substrate temperature of 623 K. The average surface roughness (R-a) of the AIN thin films was less than 2 nm obtained by locating the diamond substrates at a position of 100 mot from the aluminum target, The full width at half maximum (FWHM) of the rocking curve for the AlN(002) peak deter-mined by X-ray diffraction analysis was about 0.2 degrees. The surface acoustic wave (SAW) structures were completed by the deposition of aluminum electrodes on the as-deposited AIN surfaces. The SAW characteristics of an interdigital transducer (IDT)/AlN/diamond structure were investigated. The phase velocity and coupling coefficient were 10,120 m/s and 0.3%, respectively.