QUANTITATIVE-DETERMINATION OF ELEMENT DISTRIBUTIONS IN SILICON-BASED THIN-FILM SOLAR-CELLS USING SNMS

The determination of elemental distributions in thin film solar cells based on amorphous silicon using electron beam SNMS is possible by qua ntifying the measured ion intensities. The relative sensitivity factor s (RSFs) for all elements measured have to be known. The RSFs have bee n determined experimentally using implantation and bulk standards with known concentrations of the interesting elements. The measured RSFs h ave been compared with calculated RSFs. The model used for the calcula tion of the RSFs takes into account the probability for electron impac t ionization and the dwell time of the neutrals inside the postionizat ion region. The comparison between measured and calculated RSF shows, that this model is capable to explain the RSFs for most elements. Diff erences between calculated and measured values can be explained by the formation of hydride and fluoride molecules (in case of H and F) and influences of the angular distribution of the sputtered neutrals in ca se of Al. The experimentally determined RSFs have been used for a quan tification of depth profiles of the i-, buffer-, p- and front contact layers of a-Si solar cells.