Piezo tube stacked scanning tunneling microscope for use in extreme and confined environments

Abstract

Scanning Tunneling Microscopy (STM) is widely used for observing atomic structures due to its ultra-high spatial resolution. As the core units of STM, the coarse stepper motor and imaging unit, have conflicting size requirements for piezo tubes. Longer piezo tubes yield greater output force and easier movement for the motor, while shorter tubes enhance imaging precision and stability for the scanner. Traditional STMs typically employ a large piezo tube for coarse stepping and a smaller one for independent imaging to address this issue. Here, we present the new design of a piezo tube stacked STM, in which two independent piezo tubes act together during tip-sample approach process and only one shorter tube works during scanning imaging. Both tubes are fixed to the framework, ensuring high rigidity and compactness. The new design enables us to achieve both coarse stepping and imaging functions with a total length of only 25 mm for the two tubes, effectively reducing the length of whole STM, facilitating its integration into narrow low-temperature spaces for imaging applications. Using this device, we obtained high-quality atomic images of graphite sample surfaces at room temperature. Continuous scanning imaging of the same area on Au film at 300 K demonstrates the STM’s high stability in both X-Y and Z directions. Atomic images, I-V spectra, and di/dv spectra obtained at 2 K on graphite surface illustrate the excellent application potential of this device in low-temperature environments. Finally, atomic images obtained of graphite in sweeping the magnetic fields from 0 T to 11 T in a huge vibrational dry magnet prove the new STM’s excellent performance in extreme conditions.