ELECTRONIC-STRUCTURES OF LAYERED POLYSILANES

The electronic band structure of a newly characterized polysilane (Si6 H6) Sheet has been studied with Hartree-Fock and local density-functio nal calculations. A direct band gap was found with a calculated absorp tion edge at 3 eV. Layered structures (Si6nH6) With thicker Si sheet c ores can be constructed by linking several layers followed by hydrogen termination of the exposed surfaces. The multiply linked materials ar e found to develop a weak indirect band gap approaching that of bulk s ilicon as the number of layers increases. The observed band-gap variat ion in hydrogen-passivated porous silicon (p-Si) may be related by rec ognizing that the p-Si is made of cross-linking Si sheet structures (S i6nH6) whose Si core thickness (n) varies with preparation conditions.