A universal calibration method for eliminating topography-dependent current in conductive AFM and its application in nanoscale imaging

The topography and electrical properties are two crucial characteristics that determine the roles and functionalities of materials. Conductive atomic force microscopy (CAFM) is widely recognized for its ability to independently measure the topography and conductivity. The increasing trend towards miniaturization in electrical devices and sensors has encouraged an urgent demand for enhancing the accuracy of CAFM characterization. However, when performing CAFM tests on Bi_0.5Na_0.5TiO₃ bulk ceramic, it is interesting to observe significant currents related to the topography. Why do insulators exhibit “conductivity” in CAFM testing? Herein, we thoroughly investigated the topography-dependent current during CAFM testing for the first time. Based on the linear dependence between the current and the first derivative of topography, the calibration method has been proposed to eliminate the topographic crosstalk. This method is evaluated on Bi_0.5Na_0.5TiO₃ bulk ceramic, one-dimensional (1D) ZnO nanowire, two-dimensional (2D) NbOI₂ flake, and biological lotus leaf. The corresponding results of negligible topography-interference current affirm the feasibility and universality of this calibration method. This work effectively addresses the challenge of topographic crosstalk in CAFM characterization, thereby preventing the erroneous estimation of the conductivity of any unknown sample.