Nanoscale Ferroelectric Characterization with Heterodyne Megasonic Piezoresponse Force Microscopy

Qibin Zeng; Hongli Wang; Zhuang Xiong; Qicheng Huang; Wanheng Lu; Kuan Sun; Zhen Fan; Kaiyang Zeng

doi:10.1002/advs.202003993

Nanoscale Ferroelectric Characterization with Heterodyne Megasonic Piezoresponse Force Microscopy

Adv Sci (Weinh). 2021 Feb 15;8(8):2003993. doi: 10.1002/advs.202003993. eCollection 2021 Apr.

Authors

Qibin Zeng¹, Hongli Wang^{1

2}, Zhuang Xiong³, Qicheng Huang⁴, Wanheng Lu⁵, Kuan Sun³, Zhen Fan⁴, Kaiyang Zeng^{1

6}

Affiliations

¹ Department of Mechanical Engineering National University of Singapore Singapore 117576 Singapore.
² The Key Lab of Guangdong for Modern Surface Engineering Technology National Engineering Laboratory for Modern Materials Surface Engineering Technology Institute of New Materials, Guangdong Academy of Science Guangzhou 510650 China.
³ MOE Key Laboratory of Low-Grade Energy Utilization Technologies and Systems, School of Energy & Power Engineering Chongqing University Chongqing 400044 China.
⁴ Institute for Advanced Materials, South China Academy of Advanced Optoelectronics South China Normal University Guangzhou 510006 China.
⁵ Department of Electrical and Computer Engineering National University of Singapore Singapore 117583 Singapore.
⁶ NUS (Suzhou) Research Institute (NUSRI) Suzhou 215123 China.

Abstract

Piezoresponse force microscopy (PFM), as a powerful nanoscale characterization technique, has been extensively utilized to elucidate diverse underlying physics of ferroelectricity. However, intensive studies of conventional PFM have revealed a growing number of concerns and limitations which are largely challenging its validity and applications. In this study, an advanced PFM technique is reported, namely heterodyne megasonic piezoresponse force microscopy (HM-PFM), which uses 10⁶ to 10⁸ Hz high-frequency excitation and heterodyne method to measure the piezoelectric strain at nanoscale. It is found that HM-PFM can unambiguously provide standard ferroelectric domain and hysteresis loop measurements, and an effective domain characterization with excitation frequency up to ≈110 MHz is demonstrated. Most importantly, owing to the high-frequency and heterodyne scheme, the contributions from both electrostatic force and electrochemical strain can be significantly minimized in HM-PFM. Furthermore, a special measurement of difference-frequency piezoresponse frequency spectrum (DFPFS) is developed on HM-PFM and a distinct DFPFS characteristic is observed on the materials with piezoelectricity. By performing DFPFS measurement, a truly existed but very weak electromechanical coupling in CH₃NH₃PbI₃ perovskite is revealed. It is believed that HM-PFM can be an excellent candidate for the ferroelectric or piezoelectric studies where conventional PFM results are highly controversial.

Keywords: CH3NH3PbI3 (MAPbI3) perovskite; electrostatic force; ferroelectric; heterodyne detection; high‐frequency excitation; piezoelectric; piezoresponse force microscopy.