Noeth Andreas, Yamada Tomoaki, Sherman Vladimir O, Muralt Paul, Tagantsev Alexander K, Setter Nava
Ceramics Laboratory, Swiss Federal Institute of Technology EPFL, Lausanne, Switzerland.
IEEE Trans Ultrason Ferroelectr Freq Control. 2007 Dec;54(12):2487-92. doi: 10.1109/TUFFC.2007.565.
Direct current (DC) bias-dependent acoustic resonance phenomena have been observed in micromachined tunable thin film capacitors based on Ba(0.3)Sr(0.7)TiO3 (BST) thin films. The antiresonance frequency is only weakly DC bias dependent, and the resonance frequency exhibits a much stronger dependence on the applied DC bias. The resonance frequency shifted by 1.2% for a frequency of about 6.7 GHz and an applied field of 667 KV/cm. At the same time the effective electromechanical coupling constant k(2)(t,eff) increased to 2.0%. The tuning of the resonance frequency depends on the tunability of the film permittivity and on the mechanical load on the piezoactive layer. The experimental observations correlate well with the theoretical predictions derived from the free energy P expansion using Landau theory.
在基于Ba(0.3)Sr(0.7)TiO3（BST）薄膜的微机械可调薄膜电容器中，已观察到与直流（DC）偏置相关的声共振现象。反共振频率仅对直流偏置有微弱的依赖性，而共振频率对施加的直流偏置表现出更强的依赖性。对于约6.7GHz的频率和667kV/cm的施加电场，共振频率偏移了1.2%。同时，有效机电耦合常数k(2)(t,eff)增加到2.0%。共振频率的调谐取决于薄膜介电常数的可调性以及压电活性层上的机械负载。实验观察结果与使用朗道理论从自由能P展开推导的理论预测很好地相关。
