Affiliation: National Institute of Standards and Technology, MD, United States

Talk: July 4, 2019

Improvement of milli-Kelvin Scanning Probe Microscope System and Edge State Studyof Graphene Quantum Hall Device

In this talk, I present the improvement of functionality and energy resolution of tunneling spectroscopy of the NIST milliKelvin SPM system, and recent studies performed by this system on graphene quantum Hall device. The NIST millikelvin SPM system was constructed in 2010 as the first generation of millikelvin STM by using dilution refrigerator, and it has been operated to conduct the number of researches on 2D materials such as graphene, topological insulators. Recently, implementation of qPlus sensor AFM on the SPM module made it overcome the limitation of tunneling current measurement. By applying multi-contact sample holder and auto navigating algorithm we accomplished the in-situ transport measurement. In addition, by combining RF filters and proper electrical grounds, we achieved an ultra-high energy resolution tunneling spectroscopy – better than 10ueV energy resolution – for measuring Josephson peak spectrum on superconductor-superconductor junction, which is the best level of energy resolution in tunneling spectroscopy measurement by using SPM so far. For the analysis of high energy resolution spectroscopy, P(E) model and Maki’s theory are applied. In addition, recent studies of graphene quantum Hall edge state by AFM and KPFM measurements will be introduced.

The information about time and location of the talk will be updated soon.