The use of a linear piezoelectric actuator for coarse motion in a vacuum compatible scanning tunneling microscope

Coarse adjustment of the distance between the tunneling tip and the specimen is a major concern in the design of scanning tunneling microscopes (STMs). We present an STM design that uses a piezoelectric actuator to move a tubular piezoelectric scanning assembly and an attached tunneling tip perpendicular to the sample. The linear actuator employs piezoelectric elements driven at their resonant frequency to move a steel bar in steps. The smallest actuator step is much less than the roughly 1 μm total extension of the tubular scanning assembly. The actuators are compact and provide for tip motion from macroscopic distances to within the range of the scanning assembly without the need for additional lever or gear mechanisms. The stepper actuator assembly has the advantage of ultrahigh vacuum (UHV) compatibility when compared to other devices for achieving small linear motions such as motorized micrometers.