An Ar-H-2 plasma treatment was applied on an ultrathin RCA oxide to create well-passivated silicon wafers with symmetric c-Si/SiOx:Hia-Si:H passivation layer stacks. The effective lifetime of these samples increased from 10 mu s to 4 ms after annealing at 200 degrees C throtigh Ar-H-2 plasma treatment of the oxide. The results indicate that the plasma treatment can modify the RCA oxide and this enables atomic hydrogen diffusion at low annealing temperature, leading to a well passivated c-Si/SiOx:H interface. This might provide new possibilities to use wet chemical oxides in c-Si solar cells, for example as tunnel contacts. (C) 2016 Elsevier B.V. All rights reserved.