Native oxide layers, which form on metal surfaces in ambient atmosphere, negatively impact the performance of materials in different industrial fabrication processes like coating, welding or rolling. Therefore, removal of oxygen contaminations from metal surfaces i.e. deoxidation is an important cleaning step, which is a subject of intense research. Up to date, most common methods of metal surface deoxidation are connected with polishing or annealing of surfaces in protective or reducing atmospheres. Although such methods have been found to be effective, their application causes a strong change to the surface structure. An alternative way of surface oxide reduction uses non-thermal plasmas in hydrogen-contained atmospheres. Although the deoxidation effect of plasmas, which operate at low pressures, have been actively studied, there is a lack of information on reduction efficiency of plasmas, that operate in the atmospheric pressure range.
In the current work, the application of a dielectric barrier discharge (DBD) plasma for metal deoxidation was shown on natively oxidized copper in Ar/H₂ and Ar/SiH₄ atmospheres at 100 and 1000 hPa. Plasma treatments were performed at room temperature and a discharge voltage of 10 kV and a frequency of 8.8 kHz, which resulted in a complete removal of native oxide layers from copper surfaces within seconds of treatment in both atmospheres. The surface morphology remains almost unaffected after treatment in an Ar/H₂ gas, whereas Ar/SiH₄ plasma treatment additionally results in the deposition of loosely adsorbed silicon-contained particles on the surface. The chemical state and the morphology of samples were studied via X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM), respectively. The plasma phase was analysed by optical emission spectroscopy (OES).

Acknowledgements
The project was funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – Project-ID 394563137 – SFB1368.