Subnanometer behavior of a capacitive feedback, piezoelectric displacement actuator

This paper presents the calibration of piezoelectrically actuated capacitance micrometers for use as a transfer standard of nanometer level precision using x-ray interferometry. Because of the interferometer’s extreme sensitivity to twisting moments, there is a pressing need for high-quality transfer systems to widen its range of applicability. Two promising candidates for this are piezoelectric actuators controlled by internal capacitive sensors and parallel-plate capacitive micrometry. Both are investigated to determine useful precision for the discrimination and traceability over the range 1–20 nm. It is shown that systems of high mechanical stability can readily be produced. They offer at the very worst traceable accuracy of a few tenths of a nanometer, with, in the case of the gauge, a wide bandwidth of greater than 1 kHz. It is argued that existing technologies can provide calibrators working at relatively rapid speeds with uncertainties better than around 20 pm over usefully large ranges, presently 15 μm.