Scanning tunneling microscopy head having integrated capacitive sensors for calibration of scanner displacements

Abstract

Scanning tunneling microscopy heads having some tip–displacement measurement capability are essential for quantitative and accurate measurements. A scanning tunneling microscopy head based on a bimorph parallelogram scanner with a metallized glass cube situated above the tunneling tip is described. The cube acts as a counterelectrode or as a mirror for capacitance-based and interferometric measurements of scanner displacements. The capacitive sensors are mounted on differential screws facing the cube in such a way that the lateral Abbe error in the measurement of actual tip–displacements is minimized. The sensor electronics uses a Howland-type alternating current source, and has a deviation from linearity of less than 0.15% up to 30 μm and a low frequency bandwidth of 1 kHz.