In situ Thermal Shock of Lunar and Planetary Materials Using A Newly Developed MEMS Heating Holder in A STEM/SEM

Abstract

The US Department of Energy's Basic Energy Sciences Office published a report entitled, "Future Electron Scattering and Diffraction" in 2014. In the report, it listed the "Lab-in-gap" dynamic microscope as one of the major instrumentation needs for enabling breakthrough scientific opportunities. Specifically, it called for sample stage and holder designs that would allow advanced in situ analyses [1]. We have recently manufactured a MEMS-based heating and electric bias holder that fits into the sample stage of the newly developed 200-kV Hitachi HF5000 transmission electron microscope. The new sample stage enables a wider, jewel-less sample holder design, providing a larger platform which is advantageous for laying out electric contacts and transportation of stimuli. As shown in Fig. 1a, the Hitachi "Blaze" Heating Holder comes with the MEMS-based heating chips, which are SiN membranes sandwiching a heating element, manufactured by Norcada Inc. The contact pad to the heating chip is a replaceable. Simulated temperature profiles at 850 and 1100 o C indicated the central 160 µm-diameter is isothermal (Figs.1b and 1c). At the center of the isothermal region, there are 19 sample wells in 5 arrays. These sample wells have a 30 nm-thick SiN support film, providing electron transparency and exceptional chemical, thermal and mechanical stability.In this paper, we report the in situ heating study of lunar and planetary materials using the Blaze heating holder [2]. The lunar soil samples were acquired from the Apollo 14 and 17 missions. To prepare the samples for in situ heating, we suspended particles in methanol and then transferred them onto the heating chip using a micro pipette. We analyzed the samples after the methanol had completely evaporated. Part of the heating study was carried out using the 300 kV Hitachi HF3300 TEM/STEM located at the University of Toronto. Complementary work is also being pursued with in-depth heating studies in the probe-corrected 200 kV Hitachi HF5000 TEM/STEM at the University of Arizona. Both microscopes are equipped with a secondary electron (SE) detector, which allow simultaneous secondary and transmitted election imaging to obtain the information from the surface (SEM) and bulk (annular dark field (ADF) and bright field (BF) of the lunar soil particles. Figure 2 documents the structural evolution of one particle before and after a total of eight thermal shocks with 1-sec duration over a temperature range from 20 to 940 o C. Iron nanocrystals developed on the surface of the grain after the first thermal shock and continued to increase in size with each subsequent heat treatment. EELS analysis (not shown) further confirms the metallic nature of these iron nanocrystals.In summary, the Blaze heating holder is proven to have enabled simulation of heating events occurred on airless bodies such as lunar and planetary materials. It can also be used to address questions on thermal annealing of ceramics and nanostructured materials [3].

The ferroelectric phase transition in a 500 nm sized single particle of BaTiO3 tracked by coherent X-ray diffraction

“…The thickness of the heating chip was 2.6-2.8 μm, with a laminated membrane with spirally-patterned (Au) heating elements sandwiched between SiN membranes. 28) The optical microscope (VHX-7000, Keyence Corp.) measurement results of the samples supported onto the MEMS heating chip are shown in Fig. 2(a).…”

Enabling In Situ Studies of Metal-Organic Chemical Vapor Deposition in a Transmission Electron Microscope

“…The calibration between the sample pressure and the microscope column pressure was performed in two steps. First, we use a MEMS device, normally used for heating of a membrane (Howe et al, 2017), as a pulsed Pirani gauge for measuring the resistance through the heating coil (i.e., the temperature) at constant biasing. This is used to correlate the measured bias of the MEMS for known pressure for a set of resistances (temperatures), which were in turn measured in a closed ex situ environment as the one described in Hetherington et al (2020).…”

“…At present, two primary designs are used. The first type of chip, used for most of the results presented here, is provided by Norcada Inc. and consists of an electron transparent amorphous film (Howe et al, 2017), which can be heated and operated to at least 700C. Some chips of this type are also prepared with 2.3 m diameter holes in the thin , such that growing crystals can be imaged in vacuum.…”

“…At present, two primary designs are used. The first type of chip, used for most of the results presented here, is provided by Norcada Inc. and consists of an electron transparent amorphous SiN x film (Howe et al, 2017), which can be heated and operated to at least 700 • C. Some chips of this type are also prepared with 2.3 mm diameter holes in the thin SiN x , such that growing crystals can be imaged in vacuum. The second system is based on singlecrystal silicon microcantilevers on which the same is grown directly (Kallesøe et al, 2010), allowing for a defined epitaxial relationship between the sample and the microcantilever.…”

In-Situ High-Temperature Heating Setup for Spectronanoscopy at Pohang Light Source

“…There have been improvements that have made performing in-situ heating easier such as the development of microelectromechanical system (MEMS)-based heating microchips [4,5]. MEMS-based chips enable researchers to conduct thermal studies in a controlled and stable environment, even at 1000 ∘ C [6,7]. It is believed that equipping scanning transmission X-ray microscopes (STXMs) with in-situ heating chips can enhance their imaging capabilities.…”