Место издания:Завойский физико-технический институт, ФНЦ Казанский научный центр РАН, Казань г. Казань, Татарстан
Первая страница:147
Последняя страница:148
Аннотация:We have studied nitrogen doped microspheres: TiO2/MoO3, TiO2/WO3, TiO2/V2O5, TiO2/MoO3/V2O5, TiO2/WO3/V2O5, TiO2/MoO3/WO3, TiO2/MoO3/V2O5/WO3 using our new method based on EPR spectroscopy for constructing the band diagram of nanostructured semiconductors. Different paramagnetic centers (Ti3+, Mo5+, V4+, N•) were found in the microspheres depending on their composition. The EPR signal intensity of the revealed radicals was changing underillumination. We have measured the dependence of the EPR signal intensity of different paramagnetic centers on the photon energy (hν). Let us discuss as example the results obtained for the TiO2/MoO3/V2O5/WO3 samples. It was found that at values of the photon energy hν = 2.7 eV, an increase in the intensity of the EPR signal from Ti3+ centers occurs, and at hν = 1.55 eV,the EPR signal from N• radicals increases (TiO2 nanocrystals, Eg = 3.2 eV). We suppose, taking into account the data of, that the defects are recharged under illumination due to impurity absorption: N– + hν → N• + e (in the conductionband); Ti4+ + hν →Ti3+ + h (in the valence band). It was found that at values of the photon energy hν = 2.8 eV, an increase in the intensity of the EPR signal from Mo5+ centers occurs (MoO3 nanocrystals, Eg = 3.1 eV), and at hν = 2.1 eV,the EPR signal from V4+ radicals increases (V2O5 nanocrystals, Eg = 2.5 eV).No paramagnetic centers were detected in WO3. Using the obtained values, wecan estimate the position of the energy levels of these defects in the band gap.