Chaudhary Saurabh, Panda Janmey Jay, Mundlia Suman, Mathimalar S, Ahmedof Aathif, Raman Karthik V
Tata Institute of Fundamental Research, Hyderabad 500107, India.
Rev Sci Instrum. 2021 Feb 1;92(2):023906. doi: 10.1063/5.0041037.
Imaging atomically resolved surfaces and performing spectroscopy of exotic surfaces at cryogenic temperature in the presence of the magnetic field is an engineering challenge. Additionally, performing these measurements in an all-cryogen-free environment compounds the above complexity due to the associated vibration and acoustic noise generated by the running of cryogenic cold heads. We here report successful integration of a cryogen-free scanning tunneling microscope (STM) with a cryogen-free superconducting vector-magnet, connected to an ultra-high vacuum cluster assembly for in situ sample transfer. We present details of the integration involving vibration and electrical noise isolation procedures allowing for operation of the STM at extremely low noise levels below 30 fA/Hz during normal operations of the complete vacuum-line assembly with multiple turbomolecular pumps. We demonstrate the above STM capability at cryogenic temperature and in the presence of the magnetic field through atomic resolution imaging of graphite and thin films of gold on the mica substrate transferred in situ to the STM chamber. We also demonstrate spectroscopy signatures of the superconducting gap in MgB thin films. The design of our in-house customized cluster-vacuum-line assembly provides unsought opportunities in continuous uninterrupted imaging of ultra-clean in-vacuum grown surfaces without the need for cryogenic refills in either the STM or the magnet.
在磁场存在的情况下，在低温下对原子分辨表面进行成像并对奇异表面进行光谱分析是一项工程挑战。此外，在全无液氦环境中进行这些测量会使上述复杂性增加，因为液氦冷头运行会产生相关的振动和噪声。我们在此报告了将无液氦扫描隧道显微镜（STM）与无液氦超导矢量磁体成功集成的成果，该磁体连接到一个用于原位样品转移的超高真空簇组件。我们介绍了集成的详细情况，包括振动和电噪声隔离程序，使得在配备多个涡轮分子泵的完整真空管路组件正常运行期间，STM能够在低于30 fA/Hz的极低噪声水平下运行。我们通过对原位转移到STM腔室的云母衬底上的石墨和金薄膜进行原子分辨率成像，展示了上述STM在低温和磁场存在情况下的能力。我们还展示了MgB薄膜中超导能隙的光谱特征。我们内部定制的簇状真空管路组件的设计为连续不间断地成像超清洁的真空生长表面提供了意想不到的机会，而无需在STM或磁体中进行液氦补充。
