Scanning Probe Microscopy in an Ultra-Low Vibration Closed-Cycle Cryostat

Context of project
​Liquid helium systems are the most used cryostats. However, the so-call wet systems are facing a critical period as a result of increasing cost and storage issues of liquid helium. Consequently, in many research labs and tech companies there are a rapidly growing demand for close cycle systems (so-called dry Cryo-systems). When it comes to applications such as SPM (Scanning Probe Microscopy), so far the residual vibrations created by the cryo-cooling mechanism in close cycle cryostats are a limiting factor. In this project we aim at reducing the spurious vibrations that limit cutting edge SPM characterization.  

Our work 
We report on state-of-the-art scanning probe microscopy measurements performed in a pulse tube based top- loading closed-cycle cryostat with a base temperature of 4K and a 9T magnet. We introduced measures to reduce the level of mechanical and acoustic noise coupling into the system to enable scanning probe experiments. The extremely low vibration amplitudes in our system enabled successful imaging of 0.39nm lattice steps on single crystalline SrTiO3 as well as magnetic vortices in Bi2Sr2CaCu2O8+x superconductor. Fine control over sample temperature and applied magnetic field further enabled us to probe the helimagnetic and the elusive skyrmion-lattice phases in Fe0:5Co0:5Si with unprecedented signal-to-noise ratio of 20:1. Finally, we demonstrate for the first time quartz-crystal tuning fork shear-force microscopy in a closed-cycle cryostat.​ 

Read more:
​Scanning probe microscopy in an ultra-low vibration closed-cycle cryostat: Skyrmion lattice detection and tuning fork implementation
F.P. Quacquarelli, J. Puebla, T. Scheler, D. Andres, C. Bödefeld, B. Sipos,  C. Dal Savio, A. Bauer, C. Pfleiderer, A. Erb, K. Karrai
Microscopy Today 23 (6), 12-17 (2015)
www.cambridge.org/core/journals/microscopy-today/article/scanning-probe-microscopy-in-an-ultralow-vibration-closedcycle-cryostat-skyrmion-lattice-detection-and-tuning-fork-implementation/3C35B165DBB2572559EA0F2C94E73B15#
arXiv: arxiv.org/abs/1404.2046 
​Personal contribution: Vibration analysis, decoupling of vibration from sample space, assistance on scanning probe microscopy