A very low temperature scanning tunneling microscope for the local spectroscopy of mesoscopic structures

We present the design and operation of a very low temperature scanning tunneling microscope (STM) working at 60 mK in a dilution refrigerator. The STM features both atomic resolution and micron-sized scanning range at low temperature. We achieved an efficient thermalization of the sample while maintaining a clean surface for STM imaging. Our spectroscopic data show unprecedented energy resolution. We present current–voltage characteristics and the deduced local density of states of hybrid superconductor–normal metal systems. This work is the first experimental realization of a local spectroscopy of mesoscopic structures at very low temperature.