Some design criteria in scanning tunneling microscopy

Optimum functioning of a scanning tunneling microscope (STM) requires tip-to-sample position control with picometer precision, a rough and fine positioning capability in three dimensions, a scanning range of at least 100 times the lateral resolution, a scanning speed as high as possible, and also, preferably, simplicity of operation. These requirements have to be satisfied in the presence of building vibrations with up to micrometer-size amplitudes, temperature drift, and other perturbations. They result in design rules, presented and discussed here, for the optimization of damping, stiffness, electrical control circuitry, and the performance of the piezoelectric actuators usually employed in STMs.