Charge transport mechanism in intercalated Cu x HfSe2 compounds

Specific features of the charge and mass transfer in a silver-intercalated hafnium diselenide

“…These data allow us to find the characteristic relaxation times τ = 1/ω m which are 1.6 × 10 -6 s and 2.4 × 10 -7 s and can be interpreted as the lifetimes of the charge carriers. The values obtained are substantially lower than those found in our similar studies performed on copper containing samples of comparable compositions [20]. This differ ence testifies that, when the same matrices (HfSe 2 ) are used for intercalation, the charge transfer in the silver containing samples is faster than that in the copper containing samples; this fact seems to be related to higher mobility of the silver ions.…”

“…It is found that the increase in the silver content in the Ag x HfSe 2 com pounds decreases the relaxation times from 1.6 × 10 -6 s at x = 0.1 to 2.4 × 10 -7 s at x = 0.2. These values are substantially lower as compared to the relaxation times in Cu x HfSe 2 [20]; this fact demonstrates higher charge carrier mobility in the silver intercalated compounds. This is also confirmed by the increase in the hopping frequency, at which the frequency dispersion of the complex conductivity begins to be observed.…”

“…The power depen dence of the complex conductivity on frequency is characteristic of many materials, in which the charge carriers behave by the hopping mechanism, and is known as "universal dynamic response" (UDR) [21][22][23]. According to the theoretical concepts [24], in the [20], which indicate the identity of the conduc tivity mechanisms in these compounds. However, the frequencies (ω), at which the frequency dispersion begins to be pronounced in the Ag x HfSe 2 samples and which are called hopping frequencies [25], are 270 and 1190 kHz for x = 0.1 and 0.2, respectively.…”

Influence of the concentration of intercalated atoms and temperature on relaxation processes upon charge transfer in Cu x HfSe2 compounds

“…Previously, we investigated the temperature depen dences of the direct current (dc) resistance of copper intercalated Cu x HfSe 2 samples and revealed a sharp increase in the electrical resistance as compared to the initial hafnium diselenide [17]. It was assumed that the reason for this behavior can be the localization of charge carriers at impurity centers and that the charge transfer in this case can occur through the hopping mechanism.…”

“…The efficiency of this method is explained by the fact that the majority of synthesized functional materials are ceramics, like the samples studied in the present work. However, earlier impedance studies of samples in the Cu-HfSe 2 system [17] were performed only at room temperature. In this work, we investigated the impedance spectra of these samples in a much broader frequency range and at different temperatures, which, together with the already available data, will provide a more detailed information on the specific features of charge transfer in alternating current (ac) electric fields and the influence of temperature on the trans port properties and relaxation processes in intercala tion compounds.…”