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

Abstract

Various chalcogenide amorphous films of Te81Ge15Bi4 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.

Dielectric, Conductivity and Modulus Properties of Au/ZnO/p-InP (MOS) Capacitor

“…This deals with the increase in orientation polarization, which leads to an increase in dielectric constant. [22][23][24][25][26][27][28][29][30][31][32][33] The mobility of charge carriers increases due to increased temperature. This case causes an increase in the dielectric loss.…”

“…Besides, the temperature-dependent σ ac is for the reason that the increase in thermally activated carrier mobility and thermal activation of hopping frequency. [27][28][29][30][31][32][33] Therefore, the current transport in the MOS capacitor may be the result of the hopping conduction of thermally activated electrons under ac field. Also, the frequencydependent σ ac is due to the polarization effects.…”

“…In addition, the ac conductivity may be analyzed by Arrhenius equation defined as follows 23,28,[38][39][40][41] I indicates the computed values of E a and σ 0 . While the E a value for Region 1 decreases with increase in the frequency, the E a value for Region 2 increases with the increase in temperature.…”

“…As the temperature increases in semiconductor devices, electrons in the valence band can jump to the conduction band. Besides, the temperature-dependent σ ac is for the reason that the increase in thermally activated carrier mobility and thermal activation of hopping frequency [27][28][29][30][31][32][33]. Therefore, the current transport in the MOS capacitor may be the result of the hopping conduction of thermally activated electrons under ac field.…”

Impedance Spectroscopy and Structural Characterization of Nanostructured ZnO and Hf-Doped ZnO Ceramics

“…In the Nonoverlapping Small Polaron tunneling (NSPT) Model, the exponents increase with increasing temperature. 24,68,69 s parameters are calculated from slope of frequency dependent region in Figs. 14a and 14b.…”