Impedance switching for neural recording with ferroelectric microelectrodes

• Published in: Applied physics letters 2023-04, Vol.122 (17)
• Main Authors: Becker, Maximilian T., Oldroyd, Poppy, Strkalj, Nives, Müller, Moritz L., Malliaras, George G., MacManus-Driscoll, Judith L.
• Format: Article
• Language: English
• Subjects: Applied physics; Barium titanates; Configurations; Electric potential; Electrochemical impedance spectroscopy; Ferroelectric materials; Ferroelectricity; Microelectrodes; Saline solutions; Space charge; Switching; Thick films; Voltage
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/5.0143391

We demonstrate ferroelectric and bipolar impedance switching behavior in 18-nm-thick epitaxial BaTiO3 (BTO) films in an electrolyte–ferroelectric–semiconductor (EFS) configuration. The system is explored for its potential as a ferroelectric microelectrode in bioelectronics. Cyclic voltammetry measurements in EFS configuration, with a phosphate-buffered saline solution acting as the liquid electrolyte top contact, indicate characteristic ferroelectric switching peaks in the bipolar current–voltage loop. Moreover, small-signal electrochemical impedance spectroscopy measurements (applied root mean square voltage VRMS = 10 mV) on pre-poled EFS devices indicate bipolar impedance switching behavior. Also, a maximum ratio of the two different impedance magnitudes of ∼1.5 was observed at frequency f = 100 Hz. The observed impedance switching corresponds to a resistive switching effect, which could be explained by the modulation of the space charge region at the BTO/electrolyte interface via fixed ferroelectric polarization charges. Our approach represents a key step toward neural recordings with ferroelectric microelectrodes.