Silicon-Based Materials --Syntheses and Properties--

Silicon backbone materials as illustrated in Fig. 1 show interesting opto-electronic properties, depending on their backbone geometry. We have been focusing on these materials and investigating their physical properties.

The silicon backbone of these materials corresponds to a part of the crystalline silicon. It is interesting to realize how the semiconducting property of the silicon materials is varied based on their geometry structure. In our studies, we found that the band gap is extended over the range from 1.1 eV to 4.5 eV, as the backbone structure varies crystalline (3-dimensional), sheet-like (2-dimensional), and chain-like (1-dimensional). In contrast to the nonradiavative crystalline silicon, the chain- and sheet-like silicon materials emit intense light in the UV and visible region.

A conventional method to synthesize a chain-like polysilane is the chemical reduction of organo-substituted dichlorosilanes, R¹R²SiCl₂, with alkali metals. We have applied this reaction to organotrichlorosilanes, RSiCl₃, which has yielded silicon network polymers with a sheet-like silicon backbones [1] and an octasilacubane with a cubic silicon backbone of Si₈ [2]. Regular hetero-copolymers with other group 14 elements have also been prepared from well-designed starting materials [3].