Microwave conductivity and Raman spectroscopy of porous TiO2статья
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Дата последнего поиска статьи во внешних источниках: 19 июля 2013 г.
Аннотация:Microwave conductivity and Raman spectroscopy were applied to study the influence of light and thermal annealing on porous TiO2 properties. Microwave absorption in porous TiO2 (anatase) showed an anomalous behaviour in the presence of light excitation (at 514nm, i.e. below, or 356 nm, i.e. above the band Sap). Exposure to light at a time scale of minutes reduces the microwave conductivity, in contrast to many bulk semiconductors excited above band gap. A reduced content of oxygen after heating in vacuum leads also to a reduction of microwave absorption. Both observations ale in apparent contradiction with de conductivity in TiO2. By comparison with light-induced EPR experiments, we conclude that the oxygen removal creates deep defects to which are transferred electrons previously trapped in shallow donors. As a consequence, this decreases the polarisability of TiO2 nanoparticles, the microwave absorption, and the dielectric constant.