Cao Leonard Weihao, Wu Chen, Bhattacharyya Rajarshi, Zhang Ruolun, Allen Monica T
Department of Physics, University of California, San Diego, California 92093, USA.
Rev Sci Instrum. 2023 Sep 1;94(9). doi: 10.1063/5.0159548.
Microwave impedance microscopy (MIM) is a near-field imaging technique that has been used to visualize the local conductivity of materials with nanoscale resolution across the GHz regime. In recent years, MIM has shown great promise for the investigation of topological states of matter, correlated electronic states, and emergent phenomena in quantum materials. To explore these low-energy phenomena, many of which are only detectable in the milliKelvin regime, we have developed a novel low-temperature MIM incorporated into a dilution refrigerator. This setup, which consists of a tuning-fork-based atomic force microscope with microwave reflectometry capabilities, is capable of reaching temperatures down to 70 mK during imaging and magnetic fields up to 9 T. To test the performance of this microscope, we demonstrate microwave imaging of the conductivity contrast between graphite and silicon dioxide at cryogenic temperatures and discuss the resolution and noise observed in these results. We extend this methodology to visualize edge conduction in Dirac semi-metal cadmium arsenide in the quantum Hall regime.
微波阻抗显微镜（MIM）是一种近场成像技术，已被用于在吉赫兹范围内以纳米级分辨率可视化材料的局部电导率。近年来，MIM在研究物质的拓扑态、相关电子态以及量子材料中的涌现现象方面显示出巨大潜力。为了探索这些低能现象（其中许多现象仅在毫开尔文温度范围内可检测到），我们开发了一种集成到稀释制冷机中的新型低温MIM。该装置由具有微波反射测量能力的基于音叉的原子力显微镜组成，在成像过程中能够达到低至70 mK的温度，施加高达9 T的磁场。为了测试该显微镜的性能，我们展示了低温下石墨和二氧化硅之间电导率对比的微波成像，并讨论了这些结果中观察到的分辨率和噪声。我们将这种方法扩展到在量子霍尔效应中可视化狄拉克半金属砷化镉中的边缘传导。
