Study of coloration effects on glass slides exposed in an oxygen plasma asher

The atomic oxygen environment present in low earth orbit is extremely harmful to spacecraft materials. Simulation of this space environment is frequently done with a plasma asher. We observed a browning effect of common microscope glass slides placed in a plasma asher. After a detailed analysis, we conclude that this browning effect was not due to deposition of a film on the material surface; rather; it was the effect of optical color centers created by the depletion of F, Mg and Na from the glass surface generated by the plasma. Thus ashing experiments can be safely carried out on space materials, without fears of spurious film deposition.