A beetle-type, variable-temperature scanning tunneling microscope for video-rate imaging

Abstract

A setup is described that combines video-rate imaging with temperature variability for a beetle-type scanning tunneling microscope (STM). The STM is operated in the constant height mode. Sinusoidal driving voltages are used for the scan lines; the resulting image distortions are corrected by a straightforward mathematical operation. A phase shifter is used to compensate the time lag between the driving voltage and the tip motion. A preamplifier with a bandwidth of 300 kHz and an rms noise of ∼0.1 nA has been developed. Software has been written for data acquisition rates of up to 2 MHz and for saving movies of more than 3700 STM images of 200 × 200 pixels. Frame rates between 10 and 50 frames s−1 have been achieved, where the highest line rates are above the lowest resonance frequency of the STM. The accessible temperature range of 50–500 K is not impaired by the video mode.