Investigation of the topography-dependent current in conductive AFM and the calibration method

TL;DR

This paper investigates the influence of topography on current measurements in conductive AFM and proposes a calibration method to improve accuracy, validated on various nanostructures and biological samples.

Contribution

It introduces a calibration technique to eliminate topography-induced current errors in CAFM, enhancing measurement precision in nanoscale characterization.

Findings

The current depends linearly on the height derivative during CAFM.

The calibration method effectively reduces topography-related errors.

Validated on nanowires, 2D materials, and biological samples.

Abstract

The topography and the electrical properties are two crucial characteristics in determining roles and functionalities of materials. Conductive atomic force microscopy (CAFM) is widely recognized for its ability to independently measure the topology 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, the possibility of topography interference with the measured current during CAFM scanning leads to an inaccurate estimation of the sample's conductivity. Herein, we investigated the topography-dependent current originating from variation in capacitance between the probe and sample during CAFM testing. Based on the linear dependence between the current and the first derivative of height derived from topographic mapping, the calibration method has been proposed to eliminate the current error that is attributed to the variation in height on sample surfaces. This method is evaluated on one-dimensional ZnO nanowire, two-dimensional (2D) NbOI2 flake, and biological lotus leaf, further demonstrating the feasibility and university of this method. This work effectively addresses the challenge of topographic crosstalk in CAFM characterization, which provides significant benefits for research on demanding high-accuracy CAFM measurements.