New design, construction and evaluation of a stable scanning tunneling microscope with large-area searching and accurate positioning ability

Abstract

Investigating micron-sized sample with high spatial resolution and energy resolution greatly promotes the development of materials science. Here we present a novel scanning tunneling microscope (STM) that offers a smaller tip-sample mechanical loop, increased stability, a novel searching method, accurate positioning ability and compatibility with low temperature and high magnetic fields. The piezoelectric tube of the motor not only provides the driving force, but also allows adjustment of the sample position by applying opposite voltages on its external electrodes. The piezoelectric tube based X-Y motor is omitted from the mechanical loop to increase the stability of the STM, as evidenced by low rates of 23.5 pm/min and 36.2 pm/min in the X-Y plane and Z direction. The STM’s controllable searching ability is convincingly demonstrated through continuous large-area topographical images acquired on a graphite surface, and its positioning precision is exemplified by acquiring an atomic image of a 20 μm isolated triangular graphite flake. The new STM is also capable of working at 1.8 K low temperature and in a 12 T cryogen-free superconducting magnet, as demonstrated by the atomic image of charge density wave on TaS2 surface, dI/dV spectrums of NbSe2, and atomically resolved images in sweeping the magnet fields from 0 T to 11.5 T. These unique advantages offer new opportunities for exploring micron-sized materials and devices.