Silicon nanostructures were produced by sputter deposition of silicon in mixtures of hydrogen and argon, on the surface of a silicon substrate with dispersed gold islands, at a substrate temperature of 450 degrees C. Continuous Si films were deposited when the hydrogen concentration in the working gas was less than 50%. Silicon nanocone arrays were grown when the hydrogen concentration exceeded 50%. The lateral size of silicon nanocones increased with the deposition time. However, the length of the silicon nanocones saturated as the deposition time was increased. Mechanisms of the growth of Si nanocones by sputter deposition in mixtures of hydrogen and argon were discussed.