Lateral forces and topography using scanning tunneling microscopy with optical sensing of the tip position

A technique is described for measurement of lateral forces on a scanning tunneling microscopy (STM) tip simultaneously with surface topography, using optical sensing of the STM tip vibration. The STM tip is caused to vibrate near a resonant mode in the lateral direction, using the capacitive forces between the tip and the surface under study. Topography is monitored using the z-displacement feedback voltage, in a low-frequency loop, while optical sensing of the high-frequency tip vibration amplitude monitors lateral forces acting on the tip.