Shenzhen Key Laboratory of Nanobiomechanics;
Shenzhen Institutes of Advanced Technology;
Chinese Academy of Sciences;
Shenzhen 518055;
China;
Hunan Provincial Key Laboratory of Thin Film Materials and Devices;
Xiangtan University;
Xiangtan 411105;
China;
Department of Mechanical Engineering;
University of Washington;
Seattle 98195;
WA;
USA;
Key Laboratory of Low Dimensional Materials and Application Technology of Ministry of Education;
and School of Materials Science and Engineering;
Xiangtan University;
Xiangtan 411105;
China;
Piezoresponse force microscopy; Electrostatic interactions; Capacitive excitation;