Advanced microheater for in situ transmission electron microscopy; enabling unexplored analytical studies and extreme spatial stability

Abstract

In this work we present our advanced in situ heating sample carrier for transmission electron microscopy (TEM). The TEM is a powerful tool for materials characterization, especially when combined with micro electro-mechanical systems (MEMS). These deliver in situ stimuli such as heating, in which case temperatures up to 1300 °C can be reached with high temporal stability without affecting the original TEM spatial resolution: indeed, atomic resolution imaging can be routinely performed. Previously, the thermal expansion of suspended microheaters caused vertical displacement of the sample (bulging). As a result, changing temperatures required either continuous focus or stage adjustments, inducing resolution loss or mechanical drift, respectively. Moreover, those actions hinder the possibility to capture fast dynamic events. This new MEMS-based sample carrier, however, keeps the sample at constant z-position (no bulging) up to 700 °C. Furthermore, it enables energy dispersive x-ray spectroscopy (EDS) acquisition in the TEM up to an unmatched temperature of 1000 °C, with a drift rate down to 0.1 nm/min. Its viewable area of 850 µm2 features a temperature homogeneity up to 99.5%.