High-T-c/high-coupling relaxed PZT-based single crystal thin films

作者：Wasa K^*; Matsushima T; Adachi H; Matsunaga T; Yanagitani T; Yamamoto T

来源：Journal of Applied Physics, 2015, 117(12): 124106.

DOI：10.1063/1.4915947

Pb(Zr,Ti)O-3 (PZT)-based ferroelectric ceramics exhibit high piezoelectricity, however, their Curie temperature (T-c) values are not so high, i.e., T-c<400 degrees C. PZT-based piezoelectric thin films with higher T-c would be beneficial for improved micro actuators, sensors, memories, and piezoelectric micro-electro mechanical systems. In-plane biaxial strained PZT thin films in a laminated composite structure are known to exhibit enhanced T-c; however, the thickness of PZT-based thin films is limited to below a critical thickness typically <50 nm. The T-c of relaxed PZT-based thin films with thicknesses greater than the critical thickness is the same as bulk T-c. However, a sort of relaxed PZT-based single-crystal thin films exhibit extraordinary high T-c, T-c = similar to 600 degrees C. In addition, the films show extremely low dielectric constant, epsilon/epsilon(o) similar to 100 with high coupling factor, k(t) similar to 0.7, and large remnant polarization, P-r similar to 100 mu C/cm(2). These exotic properties would result from the single-domain/single-crystal structure. The enhanced T-c is possibly caused by the highly stable interface between the PZT-based thin films and substrates. Their ferroelectric performances are beyond those of conventional PZT. The high-T-c/high-coupling performances are demonstrated, and the possible mechanisms of the high T-c behavior in relaxed PZT-based single-crystal thin films are discussed.

• 出版日期2015-3-28