Electromechanical coupling factors of single-domain 0.67Pb(Mg1∕3Nb2∕3)O3–0.33PbTiO3 single-crystal thin films

Abstract

Thin films of single c-domain/single-crystal (1−x)Pb(Mg1∕3Nb2∕3)O3−xPbTiO3 (PMN-PT) with x≅0.33 near a morphotropic boundary composition were heteroepitaxially grown on (110)SRO∕(001)Pt∕(001)MgO substrates. The heteroepitaxial growth was achieved by rf-magnetron sputtering at the substrate temperature of 600°C. After the sputtering deposition, the substrates were rapidly cooled from 600°C to room temperature by atmospheric air gas at a cooling rate of 100°C∕min. The rapid cooling process enhanced the heteroepitaxial growth of the single c-domain/single crystal PMN-PT thin films. Their electromechanical coupling factor kt measured by a resonance spectrum method was 45% at resonant frequency of 1.3GHz with phase velocity of 5500 to 6000m∕s for the film thickness of 2.3μm. The d33 and d31 were 194pC∕N and −104pC∕N, respectively. The observed kt,d33, and d31 were almost the same to the bulk single-crystal values. The present PMN-PT thin films are applicable for a fabrication of GHz planar bulk acoustic wave transducers.