Environmental transmission electron microscopy (ETEM) is becoming an increasingly important field of study as it is possible to investigate the material-environment interactions on a nanoscale, the scale at which most of these interactions initiate. In a TEM, this can be achieved by one of the following approaches: the opened type, using a differentially pumped vacuum system where the reactive gases are spread around the specimen area of the TEM; and the closed type, using a windowed environmental cell. In the first case the maximum achievable pressure around 1 bar [1] but it is limited to flat samples and for the second type (where two chips are often put on top of each to obtain a closed cell) the maximum pressure rarely exceeds 4 bars [2]. However the last configuration is much closer to what happens in industrial applications.

We present in this paper, a new MEMS nanoreactor fully integrated on a single die. It enables atomic-scale imaging of nanostructured materials under the high pressures and temperatures that are typical for many industrial applications (10 bar and 650°C). The reactor can therefore be used to study the behavior of e.g. catalysts in a transmission electron microscope (TEM). It has a channel of 5 μm (allowing therefore an efficient loading of the samples to study), which is made with surface micromachining techniques and contains pillars that prevent bulging. The channel high can be adjusted by adjusting the right layers in the devices processing. Integrated with the device are 22 very thin windows (20 nm) and a resistive heater. The material chosen for the heater is Molybdenum. It offers a very high stability at 650 C for up to 10 h. The reactor is very transparent and clean (the windows being etched in a such way that contamination/residues are prevented) enabling the imaging of atomic lattice fringes with a spacing down to at least 0.15 nm. The maximum working pressure measured over 50 devices is above 9 bars in 90% of the cases.

References

[1] A. K. Erdamar, S. Malladi, F.D. Tichelaar, H.W. Zandbergen,  Controlled Atmosphere Transmission Electron Microscopy, 165-210, Springer International Publishing Switzerland (2016).

[2] T. Yokosawa, T. Alan, G. Pandraud, B. Dam, H. Zandbergen, Ultramicroscopy 112 (1), 47–52, (2012)

Figures:

Fig. 1. Top view of a nanoreactor with a zoom in view (top right) of the heater with the 22 transparent windows and a zoom in view of the channel during loading (bottom right).

Fig. 2. The stability of the Mo heaters used in the nanoreactors and their calibration (between 20 C and 200 C) before and after operating at 650 C for 10 H.

Fig. 3. TEM viewing windows after 10 min exposure to a 100 nm beam. No process residues are observed as well as no contaminationv (right). Max pressure test results with more than 90 % of the devices survive 9 bars (left).

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