Atomically resolved probe-type scanning tunnelling microscope for use in harsh vibrational cryogen-free superconducting magnet
Atomically resolved probe-type scanning tunnelling microscope for use in harsh vibrational cryogen-free superconducting magnet
复制标题
用于恶劣振动无制冷剂超导磁体的原子分辨探针式扫描隧道显微镜
DOI：
10.1016/j.ultramic.2019.06.006
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发表时间：
2019-10-01
期刊：
影响因子：
2.2
通讯作者：
Lu Qingyou
中科院分区：
文献类型：
--
作者：
Meng Wenjie;Wang Jihao;Lu Qingyou
我们提出了一个探针型扫描隧道显微镜（STM）的原子分辨率，被设计为直接插入和工作在一个苛刻的振动无制冷剂超导磁体系统。当在磁体中安装商业可变温度插入件（VTI）并且STM容纳在VTI中时，可以实现1.6K的最低温度，在该温度下STM仍然良好地工作。我们在用脉冲管制冷机冷却的8 T超导磁体中测试了STM，并获得了原子分辨的石墨和NbSe 2图像以及扫描隧道谱（即，dI/dV谱）数据，表明超导带隙的形成过程是温度的函数。STM在1.6K时在X-Y平面和Z方向的漂移速率分别为1.15和1.71 pm/min。隧穿电流的噪声分析表明，当我们将电流设置为0.5 nA并打开反馈回路时，主峰（6.84和10.25 Hz）的幅度低至1.5 pA.Hz（-1/2）。这一点很重要，因为无冷冻剂的磁体系统长期以来被认为对任何原子分辨率测量都过于苛刻。
We present a probe-type scanning tunnelling microscope (STM) with atomic resolution that is designed to be directly inserted and work in a harsh vibrational cryogen-free superconducting magnet system. When a commercial variable temperature insert (VTI) is installed in the magnet and the STM is housed in the VTI, a lowest temperature of 1.6 K can be achieved, at which the STM still operates well. We tested the STM in an 8 T superconducting magnet cooled with a pulse-tube cryocooler and obtained atomically resolved graphite and NbSe2 images as well as the scanning tunnelling spectrum (i.e., dI/dV spectrum) data of the latter near its critical temperature, which show the formation process of the superconducting gap as a function of temperature. The drifting rates of the STM at 1.6 K in the X-Y plane and Z direction are 1.15 and 1.71 pm/min, respectively. Noise analysis for the tunnelling current shows that the amplitudes of the dominant peaks (6.84 and 10.25 Hz) are as low as 1.5 pA.Hz(-1/2) when we set the current to 0.5 nA and open the feedback loop. This is important as a cryogen-free magnet system has long been considered too harsh for any atomic resolution measurement.