O− bound small polarons in oxide materials

摘要: Holes bound to acceptor defects in oxide crystals are often localized by lattice distortion at just one of the equivalent oxygen ligands defect. Such holes thus form small polarons symmetric clusters a few ions. An overview on mainly optical manifestations those is given. The article essentially divided into two parts: first covers basic features phenomena and their explanations, exemplified several paradigmatic defects; second part numerous materials presented which exhibit polaron properties. starts with summaries production hole identification structure. It demonstrated why they show strong, wide absorption bands, usually visible, based stabilization energies typically 1 eV. process detailed fictitious two-well system. Clusters four, six twelve ions realized various compounds. In these cases degenerate optically excited states occur, leading characteristic final state resonance splittings. peak bands as well sign transfer energy depend topology clusters. A special section devoted distinction between interpolaron intrapolaron transitions. latter comparatively weak. compounds exhibiting absorptions include alkaline earth oxides (e.g. MgO), BeO ZnO, perovskites BaTiO3 KTaO3, quartz, sillenites Bi12TiO20), Al2O3, LiNbO3, topaz other materials. There indications that magnetic NiO, doped Li, LaMnO3, Sr, also caused polarons. Beyond being elementary paradigms for properties general, defect species treated can be used explain radiation light induced especially laser non-linear materials, role some photorefractive compounds, coloration gemstones, structure certain catalytic surface centres, etc. relation further discussed: free polarons, similar distorted centres sulfides selenides, trapping holes.