Technique development of a MEMS-based heating stage for high-pressure transmission electron microscopy in the earth sciences

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Minerals at elevated pressure (P) and temperature (T) provide essential information about the interior of Earth and other planets. Knowledge of their properties and phase transitions under extreme conditions provides unique insights into seismic discontinuities, mantle plumes, mantle turnover, and other dynamic effects that occur inside planets. Transmission electron microscopes (TEMs) are the only instruments that provide the resolution needed to study high-P minerals at the atomic level. Controlled sample heating within a TEM is critical for the high-P measurements. However, it is highly challenging to obtain the required mechanical stability, minimal thermal drift, and rapid settle times, all within the small sample area of a TEM. Heating stages have recently been greatly superseded in thermal and mechanical stability, and thereby accuracy, by a totally new design for TEMs that is based on MEMS (micro-electro-mechanical systems) technology on tiny solid-state chips. This technology also permits analytical electron microscopy (AEM), including energy-dispersive X-ray spectroscopy (EDS), at elevated temperatures. Such analyses at high Ts were heretofore not possible in a TEM. MEMS heating systems have not yet been used in the earth sciences. The goal of this project is to develop this method of heating within a TEM and its utilization for studying minerals at mantle conditions. We anticipate that the results of these developments will provide a significant improvement and expansion of high-P measurements. It will be possible, for the first time, to observe the structure, behavior, and properties of earth materials at atomic resolution in situ at the PT conditions in Earth?s lower crust and mantle. The results will provide fundamental new knowledge about the nature of geologically and geophysically important minerals at extreme conditions.