In-situ Cryogenic and Biasing STEM and EELS for Quantum Materials

Understanding how the emergent phases of quantum materials form and behave during operation at the atomic scale is crucial to future quantum technology design. Cryogenic Scanning Transmission Electron Microscopy (STEM) and Electron Energy Loss Spectroscopy (EELS) have emerged as powerful tools, enabling scientists to explore quantum materials under extreme conditions of ultra-low temperatures, vacuum condictions and applied stimiulus such as bias. This cutting-edge combination of techniques integrates the high-resolution imaging and diffraction capabilities of STEM with cryogenic technology and the analytical capabilities of EELS, allowing for the investigation of materials at these low temperature exotic emergent phases, while simultaneously probing their electronic structure. <br/>In this presentation firstly the multiple ferroic phases below room temperture of Fe,I Boracite are investigated using a cryogenic STEM holder with temperature control. We investigate the change in strain, polarisation and domain configuration via 4D-STEM during temperature cycling and thus changing ferroic phases. By switching from 4D-STEM to EELS we can also collect changes in band gap and crystal field splitting. The dyamics of the domain wall topologies within these materials were investiagted using in-situ biasing at these various tempertaures and phases. <br/>Secondly, this presentation will detail how cryogenic vacuum transfer STEM can be used to probe the superconducting phase of a doped Fe(Se,Te) system. Here we show the emergence of nanoscale superconducting puddles by complementary low temperature conducting atomic force microscopy. We could pick out these region using focsued ion beam and with a vacuum transfer system we can do all sample preparation and analysis under vacuum and cryogenic conditions. We reveal the clear changes in physical structure and band gap between the superconducting and high temperature phase using controlled in-situ heating from liquid nitrogen to room temperature.