Implementation of a microplasma cell for in situ TEM

Abstract text (incl. figure legends and references)

Introduction

We built an in situ microplasma cell for integration into a TEM holder. The goal is in situ investigation of plasma surface processes on the nanoscale. Here we present the current state as well as preliminary results.

Objectives

In situ transmission electron microscopy is an area of growing interest. Observation and analysis of fabrication and/or modification processes of nanostructured materials and surfaces are essential for basic plasma physics and materials science. Also, plasma processes are a suitable method to modify nanostructures but have been largely neglected so far and are not part of the standard repertoire of in situ TEM investigations. To date, plasma treatment and material analysis are mostly separated in two steps including a sample transfer from the plasma environment into the electron microscope. To overcome this separation a microplasma cell for in situ plasma treatment inside a TEM based on the idea of Tai et al. [1] was chosen and further developed.

Materials & Methods

We use a custom sample holder from Hummingbird Scientific with high voltage capabilitites. The cell design is optimized for vacuum-tightness and reproducibility, see Fig. 1. Due to the single-shot design cells can be tested for function and being vacuum sealed before introduction into the TEM. Principle TEM studies were carried out using a JEOL JEM-2100.

Results

The choice of the geometry and discharge parameters to create a stable plasma is critical and challenging. On the one hand, gas and its purity and pressure as well as the electrical parameters to ignite the plasma have, on the other hand, to be combined with the design of a vacuum-proof but electron beam transparent cell. A stable atmospheric pressure DC normal glow microplasma discharge was studied outside the TEM fulfilling the demands in stability and size for the in situ TEM integration. The operation in the normal glow regime could be proved by electrical and optical diagnostics [2].

Conclusion

The current design and potential impact of a microplasma cell for TEM integration is given. The authors further present an outlook for adaptation of plasma treatment experiments to the microcell environment.

Acknowledgements

The authors thank the Deutsche Forschungsgemeinschaft (DFG, german research foundation) for funding (KI 1263/17-1, KE 574/8-1).

Figure 1: Sketch of the Design of the in situ microplasma cell.

References

[1] K. Tai et al., Scientific Reports, Vol. 3, pp 1325, year 2013.

[2] L. Hansen et al., 2022 Plasma Sources Sci. Technol. 31 035013