A workflow for correlative <i>in situ</i> nanochip liquid cell transmission electron microscopy and atom probe tomography enabled by cryogenic plasma focused ion beam

<i>Operando</i>/<i>in situ</i> liquid cell transmission electron microscopy (LCTEM) allows for real time imaging of dynamic nanoscale liquid-based processes. However, due to the thick liquid cell of traditional LCTEM holders and thus scattering of the electron beam passing through the cell, the achievable spatial and chemical resolution is limited. Cryogenic atom probe tomography (cryo-APT) overcomes these limitations by offering (near-)atomic scale compositional analysis of frozen liquid-solid interfaces. However, APT provides limited structural analysis and has no capacity for dynamic or <i>operando</i> liquid cell studies. This work presents a novel workflow for site-specific cryo-APT sample preparation of liquid-solid interfaces from <i>in situ</i> electrochemical LCTEM micro-electro-mechanical systems (MEMS) chips. Using a cryogenic inert gas transfer suitcase and a cryogenic plasma-focused ion beam (PFIB), a MEMs nanochip containing a Li electrolyte from an electrochemistry LCTEM holder was successfully frozen, transferred to the cryo stage of a PFIB and prepared into APT needle samples containing the electrolyte-electrode interface at cryogenic temperatures, followed by cryogenic transfer to an atom probe for nanoscale compositional analysis. This correlative approach enables both dynamic nanoscale imaging and near atomic scale compositional analysis of air sensitive and reactive liquid-solid interfaces. This method enables reliable and reproducible APT sample preparation of these frozen interfaces from MEMs based nanochips and can hence be used across materials systems and energy-conversion or storage devices.