Nanoscale Cathodoluminescence Thermometry with a Lanthanide-Doped Heavy-Metal Oxide in Transmission Electron Microscopy.

When navigated by the available energy of a system, often provided in the form of heat, physical processes or chemical reactions fleet on a free-energy landscape, thus changing the structure. In in situ transmission electron microscopy (TEM), where material structures are measured and manipulated inside the microscope while being subjected to external stimuli such as electrical fields, laser irradiation, or mechanical stress, it is necessary to precisely determine the local temperature of the specimen to provide a comprehensive understanding of material behavior and to establish the relationship among energy, structure, and properties at the nanoscale. Here, we propose using cathodoluminescence (CL) spectroscopy in TEM for in situ measurement of the local temperature. Gadolinium oxide particles doped with emissive europium ions present an opportunity to utilize them as a temperature probe in CL measurements via a ratiometric approach. We show the thermometric performance of the probe and demonstrate a precision of ±5 K in the temperature range from 113 to 323 K with the spatial resolution limited by the size of the particles, which surpasses other methods for temperature determination. With the CL-based thermometry, we further demonstrate measuring local temperature under laser irradiation.