Calibration of scanning tunneling microscope transducers using optical beam deflection

An accurate, sensitive, easily implemented method of calibration of the elastic displacement of piezoelectric transducers used in scanning tunneling microscopes has been developed. The axial displacement for both static and harmonic excitation has been measured using laser beam deflection amplified by an optical magnification system. For harmonic excitation where lock-in amplifier detection can be utilized, displacements as small as 0.03 Å have been measured. Measurements on PZT-5H and PZT-8 transducers over a range of five orders of magnitude in applied voltage demonstrate the power of the method in calibration of displacements from the subangstrom to the nonlinear region with an uncertainty of about 4%.