Towards reliable electrical measurements of superconducting devices inside a transmission electron microscope

TL;DR

This paper demonstrates reliable low-temperature electrical measurements of superconducting NbN devices inside a TEM, highlighting the importance of thermal shielding and revealing perturbations caused by electron beam and lens excitation.

Contribution

It introduces a method for performing stable, low-temperature electrical transport measurements of quantum devices inside a TEM with optimized thermal shielding.

Findings

Achieved an estimated base temperature of 8-9 K for NbN devices inside TEM.

Found that electron beam and lens excitation perturb superconductivity.

Validated imaging of magnetic domains in CrBr3 at low temperature.

Abstract

Correlating structure with electronic functionality is central to the engineering of quantum materials and devices whose properties depend sensitively on disorder. Transmission electron microscopy (TEM) offers high spatial resolution together with access to structural, electronic, and magnetic degrees of freedom. However, operando electrical transport measurements on functional quantum devices remain rare, particularly at liquid helium temperature. Here, we demonstrate electrical transport measurements of niobium nitride (NbN) devices inside a TEM using a continuous-flow liquid-helium-cooled sample holder. By optimizing a thermal radiation shield to limit radiation from the nearby pole pieces of the objective lens, we achieve an estimated base sample temperature of 8-9 K, as inferred from the superconducting transition temperatures of our devices. We find that both electron beam illumination and objective lens excitation perturb the superconducting state. In addition, we evaluate the imaging capabilities and stability of the sample holder at low temperature by imaging the magnetic domain structure of the van der Waals ferromagnet CrBr$_3$. Finally, we perform calculations that underscore the importance of cryo-shielding for minimizing thermal radiation onto the device. This capability enables correlative low-temperature TEM studies, in which structural, spectroscopic, and electrical transport data can be obtained from the same device, thereby providing a platform for probing the microscopic origins of quantum phenomena.