Binary Si:H materials are prepared by means of the rf sputtering technique in pure hydrogen atmosphere on low temperature (about 100 K) and room temperature substrates. The physical properties of the obtained materials are very much affected by the rf power and substrate temperature during the deposition. The material prepared at a low substrate temperature with a low rf power has a wide optical gap, and shows a visible photoluminescence at room temperature. On the other hand, the material prepared at room temperature with a high rf power contains many Si microcrystals, whose diameters are relatively large, and its optical gap becomes very small. The latter condition causes the dependence of the crystalline direction of the material film on the substrate crystal even at the room temperature. An rf power-modulated multi-layered structure (superlattice) is also proposed, and an apparent diffraction peak can be observed in the low-angle X-ray scattering measurement.