Publications (4)6.01 Total impact
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Article: Impact of solid phase crystallization of amorphous silicon on the chemical structure of the buried Si ZnO thin film solar cell interface
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ABSTRACT: The chemical interface structure between phosphorus doped hydrogenated amorphous silicon and aluminum doped zinc oxide thin films is investigated with soft x ray emission spectroscopy XES before and after solid phase crystallization SPC at 600 C. In addition to the expected SPC induced phase transition from amorphous to polycrystalline silicon, our XES data indicates a pronounced chemical interaction at the buried Si ZnO interface. In particular, we find an SPC enhanced formation of Si O bonds and the accumulation of Zn in close proximity to the interface. For an assumed closed and homogeneous SiO2 interlayer, an effective thickness of 5 2 nm after SPC could be estimatedApplied Physics Letters 09/2010; · 3.84 Impact Factor -
Article: Improved electrical transport in Al-doped zinc oxide by thermal treatment
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ABSTRACT: A postdeposition thermal treatment has been applied to sputtered Al-doped zinc oxide films and shown to strongly decrease the resistivity of the films. While high temperature annealing usually leads to deterioration of electrical transport properties, a silicon capping layer successfully prevented the degradation of carrier concentration during the annealing step. The effect of annealing time and temperature has been studied in detail. A mobility increase from values of around 40 cm <sup>2</sup>/ V s up to 67 cm <sup>2</sup>/ V s , resulting in a resistivity of 1.4×10<sup>-4</sup> Ω cm has been obtained for annealing at temperatures of 650 ° C . The high mobility increase is most likely obtained by reduced grain boundary scattering. Changes in carrier concentration in the films caused by the thermal treatment are the result of two competing processes. For short annealing procedures we observed an increase in carrier concentration that we attribute to hydrogen diffusing into the zinc oxide film from a silicon nitride barrier layer between the zinc oxide and the glass substrate and the silicon capping layer on top of the zinc oxide. Both are hydrogen-rich if deposited by plasma-enhanced chemical vapor deposition. For longer annealing times a decrease in carrier concentration can occur if a thin capping layer is used. This can be explained by the deteriorating effect of oxygen during thermal treatments which is well known from annealing of uncapped zinc oxide films. The reduction in carrier concentration can be prevented by the use of capping layers with thicknesses of 40 nm or more.Journal of Applied Physics 02/2010; · 2.17 Impact Factor -
Article: GIXRF NEXAFS investigations on buried ZnO Si interfaces A first insight in changes of chemical states due to annealing of the specimen
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ABSTRACT: GIXRF NEXAFS is a combination of X ray spectroscopy methods which allows for a non destructive, depth dependant chemical speciation of layer systems in the range of a few to several hundred nanometers. We applied this technique to a model system for thin film silicon solar cells, a Si ZnO layer system, which was investigated in its as deposited and its annealed state. By means of total reflection at the buried ZnO Si interface we could gain access to chemical information on the interface. In addition, a diffusion of contaminants from the ZnO into the Si was observed after annealing -
Article: Boosting mobilitiy in highly doped zinc oxide films by post deposition thermal treatment
