XPS and SIMS characterization of metal oxide/amorphous silicon—carbon interfaces

Abstract

AbstractFor different a‐SiC:H/metal oxide (TCO) layers—used for thin film solar cells—migration of metal atoms into the amorphous film, SiOx formation at the interface and reduction of TCO were investigated by SIMS and XPS depth profiling. Zinc oxide seems to be most suitable as a TCO and blocking layer, as the SiOx formation which limits transport of charge carriers is rather low compared to that from SnO2 contacts, and as no Zn is detected in a‐SiC:H in contrast to SnO2 and indium tin oxide ITO with 0.3% Sn and 20 ppm In, the latter acting as counterdopand in p+ a‐SiC:H layers. From correlations between SI yields and elemental concentrations determined by XPS, the quantification of different elements, as well as silicon oxide and metal migration can be deduced from SI intensities. In particular Si+ enhancement is a sensitive indicator for SiOx formation. By these correlations SIMS depth profiling enables fast, quantitative and highly sensitive investigations of numerous samples for optimization of preparation conditions. This is demonstrated in detail for a‐SiC:H/ZnO.