Calibrated Kelvin-probe force microscopy of 2D materials using Pt-coated probes

Abstract Nanoscale characterization techniques are fundamental to continue increasing the performance and miniaturization of consumer electronics. Among all the available techniques, Kelvin-probe force microscopy (KPFM) provides nanoscale maps of the local work function, a paramount property related to many chemical and physical surface phenomena. For this reason, this technique has being extremely employed in the semiconductor industry, and now is becoming more and more important in the growing field of 2D materials, providing information about the electronic properties, the number of layers, and even the morphology of the samples. However, although all the collective efforts from the community, proper calibration of the technique to obtain reliable and consistent work-function values is still challenging. Here we show a calibration method that improves on current procedures by reducing the uncertainty. In particular, it allows grading probes more easily, thus being a tool to calibrate and to judge calibration in itself. The calibration method is applied to optimize Pt-coated probes, which are then used to characterize the work function of a 2D material, i.e. graphite flakes. The results demonstrate that the metallic probes are stable over time and exposure to high humidity levels, and that the calibration allows comparing measurements taken with several different probes on different samples, thus completely fulfilling the requirement of a good calibration method.