In this article we present an alternative approach for the fabrication of silicon nanocrystals (Si–nc) prepared ex situ of the silicon dioxide (SiO2) host matrix. The Si–nc are scratched from porous silicon layers and incorporated into a host spin-on-glass SiO2 based matrix. High-resolution transmission electron microscopy and Raman spectroscopy revealed Si–nc of 2–5 nm size. These nanocrystallites exhibit visible room temperature photoluminescence (PL) with a maximum at about 700 nm. The presence of the dopant in the host matrix is shown to induce a blueshift of the PL maxima due to modified surface states of the Si–nc. This approach allows the fabrication of self-supporting samples with very high Si–nc concentrations. A bright photoluminescence at room temperature is obtained on such materials. Finally, strong indication of optical gain at room temperature is shown for samples with high Si–nc concentrations in a phosphorus doped sol gel host matrix.

Thin film hetero-emitter solar cells with large-grained poly-silicon absorbers of around 10 mm thickness have been prepared on glass. The basis of the cell concept is electron-beam-crystallization of an amorphous or nanocrystalline silicon layer deposited onto a SiC:B layer. The SiC:B layer covers a commercially well available glass substrate, serving as diffusion barrier, contact layer and dopand source. For silicon absorber deposition a low pressure chemical vapour deposition was used. The successively applied e-beam crystallization process creates poly-silicon layers with grain sizes up to 1 Â 10 mm 2 with low defect densities. The high electronic quality of the absorber is reflected in open circuit voltages as high as 545 mV, which are realized making use of the well-developed a-Si:H hetero-emitter technology.

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The growth of epitaxial Si on (100)-oriented Si wafers in a horizontal rapid thermal chemical vapor deposition (RTCVD) reactor has been investigated. Trichlorosilane was employed as a precursor diluted in H 2 carrier gas at 1 atm reactor pressure. The growth rates in dependence of the deposition uniformity, the input partial pressure of the precursor, and the fluid dynamics were analyzed by a three-dimensional numerical simulation. Good agreement between predicted and measured growth rates were found. Moreover, the experimental growth rates under mass transport limitation were discussed in terms of gas-phase supersaturation and its impact on the surface morphology. Finally, it is demonstrated that hydrodynamic effects in the RTCVD reactor influence strongly the Si growth in the delivery rate limited regime.