Imaging of tip‐sample compliance in STM

SUMMARY An STM was built, in which the substrate is mounted on a piezoelectric bimorph. The compliance of the tip‐surface contact region is measured by modulating the vertical position of the tip and detecting the induced deflection of the bimorph. Tip‐surface compliances between 5 and 200 N/m were measured during STM operation. It is possible to use the compliance signal for operating the microscope's feedback loop. Stable feedback loop operation can be achieved for tip‐surface distances up to about 200 nm. By operating the microscope in this constant compliance mode, surfaces of arbitrary conductance can be imaged. For conductive surfaces the tunnelling current can be recorded simultaneously. On a Nb 3 Sn film conducting and isolating patches were detected using this method.