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a b s t r a c tThere is a deficit of ways to detect higher order silane isomers during silane pyrolysis. Thus, a novel instrument utilizing gas chromatography-mass spectrometry (GC-MS) for detection of higher order silanes has been developed. The instrument enables us to separate higher order silane species using gas chromatography before they are introduced to the mass spectrometer, thereby obtaining spectra of separate isomers, rather than overlaid spectra. In this contribution we describe the details of the GC-MS system. We compare our GC-separated mass spectra of mono-, di-and trisilane to mass spectra of these species available in the literature. Further, we present mass spectra of the tetrasilane isomers n-tetrasilane (n-Si 4 H 10 ), silyltrisilane (i-Si 4 H 10 ) and cyclotetrasilane (cyclo-Si 4 H 8 ) and of the pentasilane isomers n-pentasilane (n-Si 5 H 12 ), silyltetrasilane (i-Si 5 H 12 ) disilyltrisilane (neo-Si 5 H 12 ) and cyclopentasilane (cyclo-Si 5 H 10 ). Six of these mass spectra are previously unpublished. Based on the fragmentation pattern in the tetra-and pentasilane mass spectra, we are able to acquire mass spectra of silanes with up to eight silicon atoms. Finally, we apply the novel detection technique to a silane pyrolysis reactor to track the outlet concentration of higher order silanes as function of reactor temperature. We believe that the detection technique that we present here may open the door for validation of monosilane pyrolysis models, and thus constitute a roadmap for future research in this field.

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Defect related luminescence (DRL) of mc-Si wafers, including the four D line emissions D1-D4, is investigated by hyperspectral photoluminescence (PL) imaging. The background subtraction scheme for the hyperspectral imaging setup is improved in order to obtain enhanced possibilities for comparing the DRL of different samples. In combination with PL based techniques for lifetime and iron imaging, the improved hyperspectral imaging technique is used to compare DRL of n-type and p-type mc-Si material, and to study changes of the DRL spectrum along the height of a crystalline ingot. Further, the correlation between DRL and metallic impurities as well as changes of DRL due to solar cell processing steps are investigated. No differences in the D line emissions that with certainty can be attributed to differences in material type (n/p) are found. We suggest that the spectral shape rather is determined by the recombination mechanism through which the charge carrier lifetime of a sample mainly is limited. In regions with high concentration of iron and other contaminations, we observe reduced intensities of the D3 and D4. It is thus likely that precipitates of iron or other impurities partly supress the D4 and D3 emission intensities.