Preparation and ferroelectric domain structure of micro-scale piezoelectric array fabricated by Mn doped Pb(In<sub>1/2</sub>Nb<sub>1/2</sub>)O<sub>3</sub>-Pb(Mg<sub>1/3</sub>Nb<sub>2/3</sub>)O<sub>3</sub>-PbTiO<sub>3 </sub>single crystal
Authors: Wang Ju-Shan , Ma Jin-Peng , Zhao Xiang-Yong , Chen Ming-Zhu , Wang Fei-Fei , Wang Tao , Tang Yan-Xue , Cheng Wei , Lin Di , Luo Hao-Su ,   Mathematics and Science College, Shanghai Normal University, Shanghai 200234, China,   Artificial Crystal Research Center, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 201899, China
Published: December 2020

Relaxor ferroelectric single crystal piezoelectric materials have become the core components of new piezoelectric devices such as ultrasonic transducers used in high-end medical ultrasound diagnostic and therapeutic equipment. High-element density array technology and micro-electro-mechanical systems have developed rapidly. For the new generation of 20–80 MHz medical high-frequency ultrasound transducers, the thickness of high-frequency piezoelectric composite material is usually 20–60 μm, and the width of each piezoelectric column is about 5–15 μm. However, the kerf of traditional cutting-and-filling method is too wide, and it is difficult to reduce the size of the array element, which is not conducive to the density of the array element and the demand for higher frequency applications with higher resolution. In this work, a micromechanical fabrication method based on deep reactive ion etching is used to reduce the slit width and increase the array density. We study the fabrication technology of novel and high-performance relaxor ferroelectric single crystal Mn doped Pb(In<sub>1/2</sub>Nb<sub>1/2</sub>)O<sub>3</sub>-Pb(Mg<sub>1/3</sub>Nb<sub>2/3</sub>)O<sub>3</sub>-PbTiO<sub>3</sub> (Mn-PIMNT) micro scale piezoelectric array. The influence of the parameters of lithography and deep reactive ion etching on the morphology of piezoelectric array are studied. We obtain the formation mechanisms of different kerfs, different shapes of piezoelectric array element and the relationship among etching rate of Mn-PIMNT single crystal with antenna power, bias power and etching gas ratio. Finally, the size of piezoelectric array element is less than 10 μm, the etching depth is more than 20 μm, the kerf width is less than 5 μm, the angle is controllable, and the maximum is more than 87°. The ferroelectric domain structure and the regulation of electric field effect of micro scale piezoelectric elements are studied by means of piezoelectric force microscope. The variation rules of piezoelectric properties and micro scale are obtained. This method can effectively bypass the shortcomings of the wide kerf and the destruction of the crystal orientation by the traditional cutting-and-filling method. It provides a new preparation technology for the development of high-frequency piezoelectric composites, high-density ultrasonic transducer arrays and new piezoelectric micro mechanical systems. This project presents the guidance and reference for the new micromachining technology of ferroelectric materials, and also lays the foundation for the high-frequency piezoelectric composite and high-frequency ultrasonic transducer.