Surface Potential Measurement by Atomic Force Microscopy Using Quartz Resonator

Scanning Kelvin probe microscopy (SKPM) is demonstrated using a 1 MHz quartz length extension resonator as a force sensor. A tungsten probe tip glued onto the end of the quartz rod is electrically connected to the electrode of the resonator for the detection of Coulomb force between the tip and the surface. To detect Coulomb force, a frequency shift signal is used instead of the oscillation amplitude of the resonator. Surface potential mapping is measured on a Au(111) single crystal with nanoscale carbon dots. A potential difference of 100 mV is observed between the Au surface and the carbon dots. The resolution of surface potential mapping is discussed in terms of sharpness of tip, tip–sample separation and Kelvin probe measurement technique.