Micro-nano manipulator based localized micro-area electrical impedance measurement for polycrystalline ZnO in scanning electron microscope

•Micro-area impedances of ZnO grain boundary and grain perform in demand in SEM.•High fitting degree infers relatively uniform doping in a single grain.•Quantitative studies interpret the uneven degree of grain boundary. A measurement approach of localized micro-area electrical impedances based on micro-nano manipulator was developed for polycrystalline ZnO in scanning electron microscope. Two probes as microelectrodes clamped onto the manipulator were applied to probe the electrical impedances by positioning operations in demand across a single grain boundary and within adjacent grains. Equivalent circuits were performed to fit experimental data, represented by impedance complex planes, in the frequency range 20 Hz to 1 MHz. The minor fitting errors indicated the validity of equivalent circuit parameters, which demonstrated the fact that grain boundaries were the intrinsic nature of high-resistive impedance at low-frequency DC. A quantitative method of contact resistance was proposed by equivalent circuit fitting. High linear fitting degree of impedances at 20 Hz versus probing distances can be inferred that relatively uniform impurity doping exists in a single grain. The quantitative studies of electrical impedances, vertical and parallel to a single grain boundary, can account for the uneven degree of resistive capacity existing in different locations. Electrical resistances of multi-single grain boundaries can also be statistically utilized to predict the impedance properties of bulk ZnO at the certain lower frequency.