Fig. 3: Changes in the electric potential landscapes.
a Schematic diagram of the operando cross-sectional SKPM analysis. The surface potentials of the cross-sectional samples are scanned in charge-injection directions in the SKPM mode, while a constant bias (Vbias) is applied between the cathode and anode of the device. The height images b, d, phase images c, e of the pristine and aged devices, respectively. The surface potential images obtained from SKPM measurements f, h are used to extract the corresponding electric-field strengths in the lateral directions g, i. The interfaces between the electrodes and the functional layers are illustrated by dashed white lines. The overall thickness of the functional layers is consistent with the cross-sectional STEM measurement. j, Representative surface potential profiles of the pristine (red dashed curve) and aged (blue curve) under the same bias voltage of 3 V. k Electric-field distribution profiles of the pristine (red dashed curve) and aged (blue curve) devices extracted from j.
