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21世纪以来, 扫描探针显微镜(scanning probe microscope, SPM)在微纳尺度形貌表征、物性测量及微纳加工等领域发挥着越来越重要的作用. 为了使扫描探针显微镜获得更稳定的运行环境、更高的能量分辨率, 人们研发了具备超高真空(ultra high vacuum, UHV)和低温(low temperature, LT)环境的SPM系统(UHV-LT-SPM). 目前, 大多数的UHV-LT-SPM系统通过向连续流式低温恒温器或低温杜瓦中输送液态氦-4( 4He), 使SPM的温度达到约4.2 K. 然而由于 4He元素在自然界中含量低且因需求日益增长, 导致液氦价格急剧飙升, 严重影响到了 4He相关低温设备的正常运行. 为应对上述问题, 干式制冷技术成为新一代低温技术的发展方向. 在此背景下, 将干式制冷技术与扫描探针显微镜相结合, 搭建干式低温扫描探针显微镜, 成为了目前扫描探针仪器领域的研究重点之一. 本文主要从扫描探针显微镜系统设计、降温设计、减振方法以及其设备性能等方面, 介绍目前已经报道的几种干式LT-SPM系统. 最后总结了干式LT-SPM系统目前所遇见的问题和挑战, 探讨了该技术未来的发展方向.
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 4He and its increasing demand, the significant increase in the price of liquid helium has seriously affected the normal operation of 4He-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. -
Keywords:
- cryogen-free/
- low temperature/
- scanning probe microscopy/
- vibration
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