Beilstein Arch. 2022, 202251. https://doi.org/10.3762/bxiv.2022.51.v1
Published 21 Jun 2022
Local photocurrents are commonly measured by photoconductive atomic force microscope (PC-AFM) which consists of standard conductive AFM (C-AFM) coupled with an external light source. Here we demonstrate that even basic C-AFM setup without external light sources and equipped with a built-in red laser aimed for AFM feedback loop is sufficient in order to measure local photocurrents of two dimensional (2D) materials. In this study, WS2 is taken as a test sample and typical representative of transition metal dichalcogenide based 2D semiconductors. We consider current-voltage characteristics and temporal response (current versus time) measured at single point as well as 2D current maps. Measurements are always performed for two cases, the AFM laser switched off and on, which correspond to dark and photocurrents, respectively. The special attention is devoted to the measurements of dark currents since they have to be done with AFM laser switched off. In that context, we demonstrate that only two-pass C-AFM provides stable scanning and current mapping. Although the presented approach provides a simple way to measure local photocurrents in 2D materials at the nanoscale, it inevitably has limitations which are discussed in detail.
Keywords: conductive atomic force microscopy; photocurrent; two dimensional materials
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Vasić, B. Beilstein Arch. 2022, 202251. doi:10.3762/bxiv.2022.51.v1
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