Synthesis of -FeSi2-films by pulsed laser deposition

: Panzner, M.; Mai, H.; Schöneich, B.; Witke, T.; Lenk, A.; Selle, B.; Lange, H.; Henrion, W.; Grötzschel, R.; Theresiak, A.

Abstract
The investigation of transition metal silicides has found growing interest due to its suitability for photopholtaic applications. Ecological benefits and the widely available iron and silicon based substances are substantial arguments for a broad technical use. For thin film absorbers in solar cells beta-FeSi sub2 could offer certain advantages because of its direct band transition with a gap energy of 0.85 eV and its high absorption coefficient (10 high5 cm high-1 at 1064 nm). This contribution deals with the utilization of pulsed laser deposition for the preparation of FeSi sub2 films. For that purpose, a laser beam is focussed onto the surface of a compound target to cause a stoichiometric material ablation. The appropriate particle flux than condenses at the surface of a silicon substrate held at a distance of 8 cm to the target. The influence of laser wavelength, pulse power density and substrate temperature on the properties of the synthesized films was studied by RBS, XRD, SEM a nd ellipsometry. Alpha-FeSi sub2 and FeSi were found in the films beside the main phase beta-FeSi sub2. Information about the spatial distribution of the particle flux that will influence film thickness homogenity and target material utilization by the PLD-source have been deduced from lateral thickness distributions measured in dependence on pulse power density. The results obtained support the activities for large area coating in PLD.