| AVS 60th International Symposium and Exhibition | |
| In Situ Spectroscopy and Microscopy Focus Topic | Friday Sessions |
| Session IS+AS+SP-FrM |
| Session: | Evolving In Situ Microscopic and Spectroscopic Techniques and Applications |
| Presenter: | M. Picher, National Institute of Standards and Technology |
| Authors: | M. Picher, National Institute of Standards and Technology R. Blankensihp, National Institute of Standards and Technology S. Mazzuco, National Institute of Standards and Technology R. Sharma, National Institute of Standards and Technology |
| Correspondent: | Click to Email |
In situ imaging, using an environmental scanning transmission electron microscope (ESTEM), has been successfully used to reveal and better understand the crucial chemical and physical processes occurring at the nanoscale, e.g. oxidation/reduction, coalescence, Ostwald ripening, surface reconstruction, substrate/catalyst interaction… However, the relevance of such ETEM studies can be diminished if the following two questions cannot be satisfactorily answered: i) Do high energy electrons affect the reaction mechanism? In other words: is the probed area representative of what is happening on the whole sample? ii) What is the sample temperature in the gaseous environment? Here, we present unique instrumentation that helps to solve these two issues by collecting Raman data during ETEM observation. We can now combine and compare the structural information and kinetics obtained from large (micrometer-scale) areas by the Raman spectrometer with the local information collected by the ETEM at the nanoscale. This system also enables us to simultaneously monitor the actual temperature of the probed material by analyzing shifts in Raman peak frequency. Moreover, this versatile optical setup can be used i) to investigate light/matter interactions (the current 532 nm laser can be easily replaced by any IR/Vis/UV wavelength) ii) as a heating source: the sample can be heated up to 1000°C at 15 mW with a 532 nm laser, iii) for general spectroscopy (absorption, photoluminescence, cathodoluminescence…).
This combined approach is made possible by the insertion of a parabolic mirror in between the sample holder and the lower pole piece of the microscope (Fig1. in Supp Info). It focuses a laser on the sample and collects the scattered Raman photons. A set of optics then carries the Raman signal to the spectrometer.