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Photocreated metastable states in polysilanes

1994; American Physical Society; Volume: 50; Issue: 8 Linguagem: Inglês

10.1103/physrevb.50.5171

1095-3795

Kyozaburo Takeda, Kenji Shiraishi, Michiya Fujiki, Michio Kondo, Kazuo Morigaki,

Glass properties and applications

Photocreated metastable states in organopolysilane (PSi) solids are observed using the electron-spin-resonance (ESR) technique. Two types of light-induced ESR (LESR) spectra are found depending on the excitation photon energy. These two types of LESR centers are annihilated by thermal annealing. Based on a first-principle electronic calculation, the origins of these LESR centers have been discussed. The lowest photoexcitation (\ensuremath{\sim}3.5 eV) in PSi induces the Si skeleton stretching forces, which creates a weak bond (WB) in several places of the Si skeleton. Electronically, this WB acts as a self-trapping center for the photoexcited \ensuremath{\sigma} electron. The other higher photoexcitation (over 4.8 eV) causes side-pendant dissociation, which creates a dangling bond (DB) and causes the localized midgap state. The four lines found in the higher-energy excitation are considered to arise from hyperfine interaction between this DB electron and a sodium impurity nucleus.