A method and apparatus for centrifugally forming thin semiconductor films or layers wherein centrifugal force is applied to a molten single-crystal forming material to overcome surface tension and evenly spread the material along a substrate surface substantially parallel to the axis of rotation. The material is thereafter cooled, uniformly or progressively from a seed single crystal, to form a thin layer or film of crystalline material. Desirably, the films or layers will be substantially single crystals. The process and apparatus are useful in forming thin, semiconductor crystal layers useful, for example, in solar cells. Semiconductor devices according to the invention have a porous graphite substrate, a thin film or layer of silicon and a gridwork plated onto the silicon. The interface between the silicon grid graphite substrate is substantially free from silicon carbide.