TRIPLET EXCITONS IN POROUS SILICON AND SILOXENE

The microscopic nature of the excited state responsible for the strong visible photoluminescence in porous silicon and siloxene is determine d by optically detected magnetic resonance (ODMR). The observation of dipole-forbidden Delta m = +/-2-transitions proves that this excited s tate is a triplet exciton. The allowed Delta m = +/-1-transition has t he characteristic shape of a Pake-doublett due to spin-spin interactio n, with a linewidth of approximate to 500 G independent of the photon energy monitored. These results are qualitatively incompatible with ge ometric quantum confinement, and point to a molecular origin of the ra diative center.