Martina Werner

Elemental evolution of the SiOxFy self-masking layer of plasma textured silicon and its modification during air exposure

The influence of the SiOxFy selfmasking process on the formation of black-Silicon (b-Si) textures by maskless SF6/O2 plasma etching is of great interest with regard to the optimization of the texturing process for highly antireflective silicon. For that reason, the elemental composition of plasma textured silicon surfaces is analyzed by transmission electron microscopy and X-ray photoelectron spectroscopy. The chemical composition of a fluorine containing oxide layer on top of the surface was confirmed and determined quantitatively. A strongly reduced F content was found after ambient air exposure. A qualitative model of the chemical and physical processes caused by maskless plasma texturing was developed to explain the observed experimental results. The decrease in the F content is assumed to be caused by hydrolysis of F by air moisture, resulting in a successive desorption of HF and transformation of SiOxFy to silicon oxide.

Investigation of modified p-n junctions in crystalline silicon on glass solar cells

In this paper various methods for studying p-n junctions in thin film solar cells are applied with the aim to localize and investigate defects on a microscopic scale. Different electron and ion beam characterization methods are introduced to determine the p-n junction position using two different examples from crystalline silicon on glass thin film technology. In a first example, planview and cross section electron beam induced current measurements revealed that oxygen rich columnar growth at textured substrates strongly disturbs the p-n junction. In a second example, diffusion from glass substrate is identified by ToF-SIMS to influence the electrical and structural characteristics of the thin Si layer resulting in a modified p-n junction. A model describing the formation of both defect structures is introduced.