Various Si and SiOx (x = I to 2) nanostructures were formed via a thermal evaporation method of heating pure silicon powder at 1373 K under Ar flow. An alkali-treated quartz glass plate coating with catalyst precursor of a Fe(NO3)(3) aqueous solution was used as substrate. The product exhibited morphologies of fist-capped SiOx fibers (Si-core), tree-like SiOx nanofibers and tadpole-like SiOx nanofibers in different areas of the substrate. The different local temperature gradient, concentration of silicon vapor and silicon oxide vapor, and also the substrate surface condition were suggested to be responsible for the versatile morphologies of the products.