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The ac conduction mechanism and dielectric relaxation behavior of amorphous Te81Ge15Bi4 chalcogenide glass thin films

2022; Springer Science+Business Media; Volume: 33; Issue: 15 Linguagem: Inglês

10.1007/s10854-022-08196-8

1573-482X

E.G. El-Metwally, N.A. Hegab, M. Mostfa,

Liquid Crystal Research Advancements

Abstract Various chalcogenide amorphous films of Te 81 Ge 15 Bi 4 in the range (143–721 nm) were synthesized using the thermal evaporation technique. The ac electrical conductivity $${\sigma }_{ac}\left(\omega \right)$$ σ ac ω and dielectric measurements were examined for the studied films over the temperature and frequency ranges of (303–393 K) and (100 Hz–1 MHz), respectively. The obtained results of ac conductivity $${\sigma }_{ac}\left(\omega \right)$$ σ ac ω are temperature dependent and follow the relation $${\sigma }_{ac}\left(\omega \right)\propto {\omega }^{s}$$ σ ac ω ∝ ω s , where the frequency exponent $$s$$ s decrements with temperature through the examined range. These results of $${\sigma }_{ac}\left(\omega \right)$$ σ ac ω and $$s$$ s are explained based on the correlated barrier hopping CBH model. Values of ac activation energy $$\Delta {E}_{\sigma }\left(\omega \right)$$ Δ E σ ω show thickness independence and decrease from 0.270 to 0.144 eV as the frequency increases. The estimated maximum barrier height $${W}_{M}$$ W M values decrement with temperature in the considered frequency range. The density of localized states near the Fermi level $$N\left({E}_{F}\right)$$ N E F increases with increasing temperature and frequency. The dielectric constant $${\varepsilon }_{1}(\omega )$$ ε 1 ( ω ) and loss $${\varepsilon }_{2}(\omega )$$ ε 2 ( ω ) were found to increment with temperature and decrement with frequency. The obtained results indicate that $${\sigma }_{ac}\left(\omega \right)$$ σ ac ω , $$N\left({E}_{F}\right)$$ N E F , $${\varepsilon }_{1}\left(\omega \right)$$ ε 1 ω and $${\varepsilon }_{2}\left(\omega \right)$$ ε 2 ω are enhanced by decreasing the thickness of the film sample in the investigated ranges of temperature and frequency. The real $${M}_{1}(\omega )$$ M 1 ( ω ) and imaginary $${M}_{2}(\omega )$$ M 2 ( ω ) parts of the electric modulus were studied for the films under test, and the value of the activation energy for relaxation $$\Delta {E}_{r}$$ Δ E r (0.143 ± 0.002 eV) is thickness independent in the investigated range.