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We have studied charge transport anisotropy in microcrystalline silicon (µc-Si:H) by comparing diffusion length measured parallel to the substrate by steady stage photocarrier grating and perpendicular to the substrate by surface photovoltage method (SPV). We have developed a SPV evaluation procedure which allowed us to exclude the effect of light scattering at the naturally rough surface of the µc-Si:H. The procedure allows us to deduce not only the diffusion length, but also the depth of the depletion layer at the surface and recombination coefficients at both top and bottom interfaces of the film. With growing µc-Si:H film thickness the size of the crystallites increases, leading to higher roughness and thus also light scattering. At the same time density of grain boundaries decreases, resulting in an increase of the diffusion length and of the surface depletion layer depth. For all samples the diffusion length perpendicular to the substrate was several times higher than the diffusion length parallel to it, clearly confirming previous indication of the transport anisotropy resulting from the measurements of coplanar and sandwich conductivity. [ABSTRACT FROM AUTHOR]

A characteristic photoluminescence of a superficial Si nanolayer realized by ion implantation has been observed. This effect, being totally independent of those shown recently for a nanoscale Si-layered system, is similar to that produced by Si nanocrystals (Si nc). To visualize the nature and give evidence of this effect, we fabricated samples in two different ways: (i) by incorporation of Si nc into thin SiO[SUB2] films deposited on Si wafer by the spin-on-glass method and (ii) by a nanoscale superficial crystalline-Si modification using medium-energy ion implantation and thermal treatment. In both cases the UV-to-red light conversion has been observed to be independent of wafer post-implantation damage. To show the UV-to-red conversion contribution, we use the ion modified superficial Si layer with its well-defined potential barrier, the so-called carrier collection limit. Such a modified Si structure gives us a method of deconvoluting several optoelectronic features observed experimentally on modified Si. The practical realization is compatible with well-established Si technology. [ABSTRACT FROM AUTHOR]