Advances in dry low-temperature scanning probe microscopy system development

Since the beginning of the 21st century, scanning probe microscopy (SPM) has played an increasingly important role in investigating the micro- and nanoscale surface characterization, physical property measurement, and micro/nano fabrication. To provide a more stable operating environment and higher energy resolution for SPM, researchers have developed low-temperature scanning probe microscopy (LT-SPM) systems that operate under the conditions of ultra-high vacuum and low temperature. Currently, most of LT-SPM systems have achieved temperatures around 4.2 K by supplying liquid helium-4 (4He) to continuous flow cryostats or low-temperature Dewars. However, due to the low natural abundance of 4 He and its increasing demand, the significant increase in the price of liquid helium has seriously affected the normal operation of 4 He- based low temperature equipment. To solve this problem, dry (cryogen-free) refrigeration technology has emerged as a promising alternative to the next-generation low-temperature systems. In this context, the integration of dry refrigeration technology with SPM to construct Dry-LT-SPM systems has become a key research focus in the field of scanning probe instruments. This paper mainly discusses several reported closed-cycle Dry-LT-SPM systems, focusing on aspects such as system design, refrigeration schemes, vibration reduction methods, and overall performance. Finally, this paper summarizes the current challenges and problems faced by Dry-LT-SPM systems and explores potential future developments in this field.