AC Conduction and Time–Temperature Superposition Scaling in a Reduced Graphene Oxide–Zinc Sulfide Nanocomposite

Abstract

We report, herein, the results of an in depth study and concomitant analysis of the AC conduction [σ'(ω): f=20 Hz to 2 MHz] mechanism in a reduced graphene oxide-zinc sulfide (RGO-ZnS) composite. The magnitude of the real part of the complex impedance decreases with increase in both frequency and temperature, whereas the imaginary part shows an asymptotic maximum that shifts to higher frequencies with increasing temperature. On the other hand, the conductivity isotherm reveals a frequency-independent conductivity at lower frequencies subsequent to a dispersive conductivity at higher frequencies, which follows a power law [σ'(ω)∝ω(s) ] within a temperature range of 297 to 393 K. Temperature-independent frequency exponent 's' indicates the occurrence of phonon-assisted simple quantum tunnelling of electrons between the defects present in RGO. Finally, this sample follows the "time-temperature superposition principle", as confirmed from the universal scaling of conductivity isotherms. These outcomes not only pave the way for increasing our elemental understanding of the transport mechanism in the RGO system, but will also motivate the investigation of the transport mechanism in other order-disorder systems.

Reduced‐Graphene‐Oxide Zinc‐Telluride Composite: Towards Large‐Area Optoelectronic and Photocatalytic Applications

“…The electrical conductivity plays a crucial role in the solid state device performance. In this stand point, the studies on ac transport mechanism in the composite is highly desirable as it provides better insight on the conduction mechanism, which is highly significant for electronic and optoelectronic devising . The complex ac conductivity can be expressed as σ * (ω)=σ′(ω) + jσ′′(ω) ; where, σ′(ω) and σ′′(ω) represents the real and imaginary parts of ac conductivity respectively.…”

Reduced Graphene Oxide ‐ Zinc Phthalocyanine Composites as Fascinating Material for Optoelectronic and Photocatalytic Applications

“…The best fitted photoresponse time constants of our RGO‐ZnTTBPc device are about 5 and 87 seconds for growth and 18 and 97 seconds for decay,indicating rapid photocurrent growth (decay) initially followed by very slow growth (decay) process. In RGO‐ZnTTBPc composite the transport is dominated by the disorder of the individual sheet, charge trapping between different sheets and the defects present in RGO, which leads the diffusion of charge carriers and are responsible for the slow time response . In the next section we have studied the conductivity relaxation in the composite material to get a detail idea on the electrical transport mechanism.…”

“…Where, ω c is the cross over frequency from dc to dispersive conductivity, and n is the frequency exponent. This power law model has been widely used to analyze the conductivity spectra in different RGO based systems, conducting glasses, conducting polymers and MoS 2 based systems below microwave frequency range . The σ dc , ω c and n were calculated from the fittings of Eqn.…”

“…The frequency exponent n remains independent of temperature ( n ∼ 0.85) within the studied temperature range. The temperature independent n indicates that the frequency dependent ac conductivity arises due to the phonon‐assisted simple quantum tunneling of electrons between the localized defects states ,. These localized defect states are mainly responsible for the slow photoresponse time of RGO‐ZnTTBPc composite [Figure B and 4C].We have also investigated an interesting problem: does the relaxation mechanism depend on temperature in this RGO‐ZnTTBPc composite?…”

Thermal, electrical, and dielectric properties of reduced graphene oxide–polyaniline nanotubes hybrid nanocomposites synthesized by in situ reduction and varying graphene oxide concentration

“…However, as the frequency is increased, the mean displacement of the charge carriers is reduced and the conductivity increases due to the activation of trapped charges in the system that undergoes localized motion . The frequency dependent conductivity is explained by the Jonscher's universal power law represented by the following equation and the fitted curves are presented in solid lines in Figure . where σ dc is the dc conductivity, A is a constant, ω = 2πν, ν being the frequency, and s is a frequency dependent exponent having values in between 0 and 1.…”