Nano-tubes, fibers, and wires are interested as an intelligent material supporting the "nano-technology". Silicon nano-wire@footnote 1@ and other semiconductor nano-wires@footnote 2@,@footnote 3@ had already been produced before the discovery of carbon nano-tube by Iijima.@footnote 4@ Recently, Homma et al.@footnote 5@ succeeded to form Si nano-columns on a Si substrate arranged with Au-islands by using vapor-liquid-solid (VLS) reaction of disilane (Si@sub 2@H@sub 6@). In the present work, we have demonstrated the formation of the Si stem (a bundle of nano-fibers) without using VLS reaction. Small Si particles for the seeds of the Si stems were scattered on a Si(111) wafer. After introducing the wafer in an ultrahigh vacuum (UHV) chamber, monolayer-equivalent Au atoms were deposited on the wafer by the vacuum evaporation. After the deposition, the wafer was annealed at 1000°C for 260 minutes. Then the Si stems were formed on the Si surface, which were observed by scanning electron microscope (SEM). The stems looked like tiny mushrooms in micro-meter scale. The Au atoms worked as a catalyst for the stem formation by inducing the surface segregation of the bulk-materials. @FootnoteText@ @footnote 1@ R.S. Wagner, W.C. Ellis, Appl. Phys. Lett. 4 (1964) 89. @footnote 2@ G.A. Boostma, H.J. Gassen, J. Cryst. Growth. 10 (1971) 223. @footnote 3@ E.I. Givargizov, J. Cryst. Growth. 32 (1975) 20. @footnote 4@ S. Iijima, Nature 354 (1991) 56. @footnote 5@ Y. Homma, P. Finnie, T. Ogino, H. Urisu, J. Appl. Phys. 86 (1999) 3083.