一种在亚皮米z噪声下运行并配备脉管和焦耳-汤姆逊冷却的超高真空扫描隧道显微镜
An Ultra-High Vacuum Scanning Tunneling Microscope with Pulse Tube and Joule-Thomson cooling operating at sub-pm z-noise
AI总结：
本文介绍了一种无需外部冷却液的超高真空扫描隧道显微镜系统，结合脉管与焦耳-汤姆逊冷却及多级振动解耦设计，实现了1.5 K低温和300 fmRMS的z噪声，并支持高达40 GHz的射频激发。
摘要：
我们描述了一种紧凑的超高真空（UHV）扫描隧道显微镜（STM）系统，该系统不需要任何外部冷却液供应。它实现了低至1.5 K的温度，并且在0.1 Hz至5 kHz的频率范围内（反馈回路关闭时）z噪声低至300 fmRMS。它采用脉管低温冷却器（PTC）和焦耳-汤姆逊（JT）级，在STM处仅引起幅度低于1 mK的微小温度振荡。将PTC的有效振动解耦与充分的热传导相结合的挑战，通过一种多部分方法得到解决。我们实现了连接PTC和STM腔室的UHV波纹管的最小刚度。细铜线在机械上将PTC各级与承载热屏蔽、JT级和STM的冷却板解耦。软弹簧将STM与JT级解耦。最后，STM主体具有优化的圆锥形状，由轻质且坚硬的材料Shapal Hi MSoft制成，从而在隧道结处实现了低频振动的强烈减少。隧道结处的电压噪声为0.12 mV，靠近隧道结的RF天线提供高达40 GHz的射频激发，幅度高达10 mV。
英文摘要：
We describe a compact ultra-high vacuum (UHV) scanning tunneling microscope (STM) system that does not need any external supply of cooling liquids. It achieves temperatures down to 1.5 K and a z-noise down to 300 fmRMS for the frequency range of 0.1 Hz - 5 kHz (feedback loop off). It employs a pulse tube cryocooler (PTC) and a Joule-Thomson (JT) stage inducing only small temperature oscillations at the STM with amplitude below 1 mK. The challenge to combine an effective vibrational decoupling from the PTC with sufficient thermal conduction is tackled by a multipartite approach. We realize a minimal stiffness of the UHV bellows that connect the PTC and the STM chamber. Fine Copper wires mechanically decouple the PTC stages from cooling plates that carry the thermal shields, the JT stage and the STM. Soft springs decouple the STM from the JT stage. Finally, the STM body has an optimized conical shape and is made of the light and stiff material Shapal Hi MSoft such that a strong reduction of low frequency vibrations results for the tunnel junction. The voltage noise in the tunnel junction is 0.12 mV and an RF antenna close to the tunnel junction provides radio frequency excitations up to 40 GHz with amplitudes up to 10 mV.
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