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

高压（P）和高温（T）下的矿物提供了有关地球和其他行星内部的基本信息。了解它们在极端条件下的性质和相变，可以对地震不连续性、地幔柱、地幔翻转和行星内部发生的其他动力学效应提供独特的见解。透射电子显微镜（TEM）是唯一能够提供在原子水平上研究高磷矿物所需分辨率的仪器。在TEM内控制样品加热对于高P测量是至关重要的。然而，要在TEM的小样品区域内获得所需的机械稳定性、最小的热漂移和快速稳定时间是非常具有挑战性的。最近，加热台在热稳定性和机械稳定性方面以及精度方面已经被基于微型固态芯片上的MEMS（微机电系统）技术的全新TEM设计所取代。该技术还允许在高温下进行分析电子显微镜（AEM），包括能量色散X射线光谱（EDS）。这种在高Ts下的分析在TEM中是不可能的。MEMS加热系统尚未在地球科学中使用。 该项目的目标是发展这种在TEM中加热的方法，并将其用于研究地幔条件下的矿物。我们预计，这些发展的结果将提供一个显着的改善和扩展的高磷测量。这将是可能的，第一次，观察地球材料的结构，行为和性质，在原子分辨率原位在地球上的PT条件？下地壳和地幔。这些结果将提供有关极端条件下地质和矿物学重要矿物性质的基本新知识。

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 Heating stages have recently been greatly superseded in thermal and mechanical stability, and thereby accuracy, by a totally new design for TEMs that is based on MEMS (micro-electro-mechanical systems) technology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.