Single polaron hopping in Fe doped glassy semiconductors: Structure–electrical transport relationship

Abstract

The development of glassy nanocomposites, xFe-(1−x) (0.5 [Formula: see text]–0.4 CdO–0.1 ZnO) is particularly important not only for exploring their microstructures using x-ray diffraction, FT-IR, and UV–Vis techniques but also for exploring their electrical conduction mechanism in terms of hopping of small polarons. The presence of various nanophases, such as ZnO, CdO, Cd9.5Zn0.5, ZnV, and Zn3V2O8, have been identified and the size of estimated nanocrystallites is found to decrease with more incorporation of the Fe content in the compositions. As the value of lattice strain increases with the increase of the Fe content in the compositions, the present system becomes more and more unstable, which may be favorable for better electrical transport phenomena via the polaron hopping process. Electrical conductivity of the system has been analyzed using modified correlated barrier hopping model, Almond–West formalism, and the alternating-current conductivity scaling. Experimental data reveal that both optical photon and acoustical phonon transitions are responsible for the entire electrical conduction process. Polaron hopping is expected to be of percolation type, which has been validated from an estimated range of frequency exponents. All experimental data have been used to frame a schematic model to explore the conduction mechanism inside the present glassy system.

Influence of Fe on Crystallization Behaviour and Electrical Conductivity of V2O5 ⋅ MoO3 ⋅ CdO ⋅ ZnO Glass Nanocomposite

“…[52][53][54] Figure 6 depicts the temperature-dependent DC electrical conductivity of the current system, demonstrating its thermally activated nature. [12,[23][24][53][54]56] It is also shown in Figure 6 that the current system agrees well with the DC conductivity ranges of a vanadium-doped nanostructured sample doped. [12,57] As can be observed in Figure 6, DC conductivity rises as temperature rises, indicating that the current system is of semiconducting type.…”

“…It is also shown in Figure 6 that the current system agrees well with the DC conductivity ranges of a vanadium‐doped nanostructured sample doped [12,57] . As can be observed in Figure 6, DC conductivity rises as temperature rises, indicating that the current system is of semiconducting type [12,23–24,53–54,56] . As the Fe content is doped gradually with the host glassy system, DC conductivity increases [24] .…”

“…We have observed that DC activation energy (E σ ), and activation energy (E H ) for hopping frequency (ω H ) increases with increasing Fe content in glass system based on xFe ⋅ (1‐x) (0.3 V 2 O 5 ⋅ 0.2MoO 3 ⋅ 0.4CdO ⋅ 0.1ZnO) [x=0.0, 0.05, 0.10] compare with other glassy systems [12,23–24,53–54,56] (Table 1).…”

“…This type of behaviour of DC conductivity and corresponding activation energy should be related to structural modifications, observed with the addition of Fe. [24] From XRD and FT-IR studies, it is evident that minimal energy is needed to vibrate the MoÀ O and ZnÀ O bands in order to incorporate acoustic phonon contributions as the compositions' Fe concentration rises. Although, when the compositions' doping of Fe concentration increases, DC conductivity steadily rises.…”

“…[60] Higher values of n would suggest the motion of a small polaron in the current nano glassy system is percolation type. [60][61][62][23][24]37] We have observed that DC activation energy (E σ ), and activation energy (E H ) for hopping frequency (ω H ) increases with increasing Fe content in glass system based on xFe ⋅ (1-x) (0.3 V 2 O 5 ⋅ 0.2MoO 3 ⋅ 0.4CdO ⋅ 0.1ZnO) [x = 0.0, 0.05, 0.10] compare with other glassy systems [12,[23][24][53][54]56] (Table 1).…”