Single electron tunneling to insulator surfaces measured by frequency detection electrostatic force microscopy

Single-electron tunneling events between a metal probe and an insulator surface are measured by frequency detection electrostatic force microscopy. Single-electron tunneling events typically cause 1-10 Hz shifts in the 300 kHz resonance frequency of the oscillating force probe. The frequency shifts appear only within a sub-2 nm tip-sample gap and their magnitude is roughly uniform under fixed experimental conditions. An electrostatic model of the probe-sample system yields results consistent with the measurements.