A millikelvin all-glass scanning probe microscope*

Milli-Kelvin scanning probe microscopy (mK-SPM) presents an ongoing experimental challenge due to the intense vibrations[1] in a closed-cycle dilution fridge and the low cooling power available at mK temperatures. A viable approach is to make the system exceptionally rigid and thermally insulative to decouple external vibrations and isolate heat dissipation from the piezo elements. Here we present a low-cost and large scan-area mK-SPM that operates below 100 mK. All the essential parts of our mK-SPM, including the motors, scanners, and microscope body, are made of fused silica glass by taking advantage of its high specific modulus, extremely low thermal expansion coefficient, and excellent thermal insulation properties. We carefully balance the scan area (25 µm×25 µm), heat dissipation, and rigidity of the system to reach optimal performance at mK temperatures.