Impedancemetry of Ag-=SUB=-2-=/SUB=-S nanocrystallites embedded in nanoporous glasses

Abstract

The temperature dependences of the dielectric spectra of Ag2S nanocrystallites synthesized inside the channels of nanoporous glasses NPG-17 with an average diameter of filamentous pores of 17 nm are studied. The macroscopic mechanism for the occurrence of the frequency dependence of the electrical response of a nanoporous structure NPG-17 + Ag2S is proposed. Formation of the model of mechanism is based superionic phase transition in Ag2S nanocrystallites fixed inside the channels of nanoporous glass is discussed. Keywords: silver sulfide, Ag2S, nanoporous glasses, nanostructured materials, impedancemetry.

Ellipsometric characterization of VO-=SUB=-2-=/SUB=-, VO-=SUB=-2-=/SUB=- : Mg, VO-=SUB=-2-=/SUB=- : Ge nanocrystalline films

“…Mg impurity in VO 2 film crystallites is an electrons donor [24]. According to our measurements (Fig.…”

“…Therefore, doping with Mg increases the average material density and results in increase of refraction index n 0 [28]. At the same time, Mg 2+ ion in VO 2 has poorly expressed donor properties [24], resulting in growth of extinction coefficient in VO 2 : Mg film, that we observed experimentally (Fig. 2).…”

“…This happens due to Coulomb transformation of FDoS conductivity band, caused by reduction of free electrons concentration. At the same time, the dielectric spectra of VO 2 : Ge film [24] indicate increase of temperature T C of phase transition and, thus, expansion of the forbidden band (not narrowing, as for VO 2 : Mg). Such expansion is caused by acceptor properties of Ge impurity.…”

“…Ge ions have not donor, but acceptor properties [24]. Doping with Ge should, as opposed to VO 2 : Mg, move the value of " zero' point of n(λ) (dotted line) towards lower energy.…”

“…Unusualness of the results appears due to presence of strong interelectronic correlations in vanadium oxides. Novelty of the obtained data is related to usage of high-information modern study methods: photonic crystals spectroscopy with VO 2 -filling [5], pico-and femtosecond spectroscopy [6], near-field optical microscopy along with atomic force microscopy [7][8][9], as well as EXAFS methods [10].…”