Nanoscale contact charging of MoS₂ by atomic force microscope

Abstract

Contact Electrification of MoS₂ at nanometer level was demonstrated using a tapping mode Atomic Force Microscope or AFM. A highly doped n-type Si tip, d.c. biased from 0 to ±2 V with a resonant frequency of 300 kHz and a fixed amplitude set-point amplitude of 20 nm, was used to generate contact electrification on the surface of 5 mm x 3 mm MoS₂ sample. Using the Kelvin Probe Force Microscope or KPFM, the surface potential images were shown to have bipolar charging and the surface charge affinity is more influenced by the positive bias voltage.