Alteration of the chemical composition of fused silica surfaces via combined hydrogenous plasma treatment and UV laser irradiation

In this contribution, we report on the influence of nitrogen-hydrogen plasma treatment on the chemical composition of fused silica surfaces with and without additional argon fluoride laser irradiation. Therefore, the compositions of pristine and plasma treated fused silica samples were investigated by secondary ion mass spectrometry before and after laser irradiation. Transmission data were moreover obtained via UV-VIS spectroscopy. The plasma treatment most likely generates optically active defects such as non-bridging oxygen hole centers (NBOHCs), oxygen-deficiency-related defects (ODCs), and E' centers, which serve as precursor sites for hydrogen saturated defects. The resulting enhanced laser coupling leads to a loss of oxygen from the fused silica network and a further generation of defect centers. Possible explanatory approaches for the observed plasma- and laser-induced changes in carbon, hydrogen, and oxygen content are discussed. This includes the formation of silicon monoxide, hydrogen saturated defects, and nanocrystalline domains in the matrix containing silicon-carbon bonds.