Plasma surface treatment of GeSn layers and its subsequent impact on Ni / GeSn solid-state reaction

The plasma surface treatment of GeSn layers was monitored by quasi in-situ parallel angle-resolved X-ray photoelectron spectroscopy (pAR-XPS) and atomic force microscopy (AFM). The combination of a wet cleaning and an Ar plasma treatment appeared to be the best compromise to reduce the quantity of native oxides on GeSn surfaces without impacting the surface roughness. In particular, the passivation effect of HCl was particularly beneficial to control the regrowth of oxides at the GeSn surface before the plasma treatment and to obtain a final relative low amount of oxides.