Integrated cryogenic optical microscopy and transport measurement system for spatiotemporal studies across phase transitions from 100 K to 400 K

Abstract We discuss the design and performance of a liquid nitrogen-cooled optical microscopy system that also allows for simultaneous transport measurements. Incorporating a cold-finger based design, the system operates at temperatures between 100 and 400 K with a controlled ramp rate (0.1 K min −1 to 42 K min −1 ) and thermal stability (±5 mK) at any given temperature. The cryostat forms part of a modular and versatile experimental set-up, particularly suitable for low temperature bright-field reflection microscopy under Köhler illumination. With careful selection of optical components, an active focus correction system to account for the thermal expansion, along with effective vibration isolation, a sub-micron spatial resolution has been achieved. Finally, we demonstrate optical imaging of the electric breakdown in vanadium dioxide using this setup.