Hong Eunki, Trolier-McKinstry Susan, Smith Robert, Krishnaswamy Silai V, Freidhoff Carl B
Materials Research Institute, The Pennsylvania State University, University Park, PA 16802, USA.
IEEE Trans Ultrason Ferroelectr Freq Control. 2006 Apr;53(4):697-706.
Electrically and mechanically excited resonances in micromachined circular piezoelectric diaphragms have been investigated. The diaphragm structures were piezoelectric unimorphs consisting of Pb(Zr0.52,Ti0.48)O3 (PZT) films and thermally grown silicon oxide (SiO2) layers. For electrical excitation, ring-shaped interdigitated (IDT) electrodes formed on the top of the PZT layer were used to induce strain in the diaphragms. The diaphragm structures behaved much like circular membranes in which the membrane tension was approximately 206 N/m, at the fundamental modes. For higher modes, the resonance frequencies deviated from the theoretical values due to the finite stiffness of the diaphragms. Under mechanical drive, both symmetric and asymmetric modes were excited. However, for electrical excitation, the symmetric modes were dominant due to the symmetry of the driving IDT electrodes. At a pressure of 727 Torr, the quality factor was approximately 250, and this rose to 2000 at pressures below 1 Torr. When a forward bias was applied to the diaphragm, the membrane tension decreased, but under reverse biases the tension increased. However, because of repoling under reverse biases greater than the coercive field of the PZT film, the achievable increase in the membrane tension was limited. In the diaphragm structure, the nonlinear vibration was governed by geometric nonlinearity rather than material nonlinearity. In addition, evidence of non-180 degrees domain wall motion of the PZT layer in released diaphragms was observed.
对微机械加工圆形压电膜片中的电激励和机械激励共振进行了研究。膜片结构为压电单压电晶片，由Pb(Zr0.52,Ti0.48)O3（PZT）薄膜和热生长氧化硅（SiO2）层组成。对于电激励，在PZT层顶部形成的环形叉指式（IDT）电极用于在膜片中产生应变。在基模下，膜片结构的行为非常类似于圆形膜，其中膜张力约为206 N/m。对于高阶模，由于膜片的有限刚度，共振频率偏离理论值。在机械驱动下，对称和非对称模式均被激发。然而，对于电激励，由于驱动IDT电极的对称性，对称模式占主导。在727托的压力下，品质因数约为250，在低于1托的压力下，品质因数升至2000。当对膜片施加正向偏压时，膜张力降低，但在反向偏压下张力增加。然而，由于在大于PZT薄膜矫顽场的反向偏压下重新极化，膜张力可实现的增加受到限制。在膜片结构中，非线性振动由几何非线性而非材料非线性控制。此外，在释放的膜片中观察到了PZT层非180度畴壁运动的证据。
