Frequency dependent electrical characteristics and origin of anomalous capacitance–voltage (C–V) peak in Au/(graphene-doped PVA)/n-Si capacitors

Abstract

Au/(7% graphene-doped PVA)/n-Si capacitors were fabricated and their electrical characteristics were investigated using complex impedance spectroscopy method (ISM) in the wide frequency range at room temperature. Experimental results show that the values of capacitance (C) and conductance (G/ω) decrease with increasing frequency. Such behavior of these parameters, especially at low frequencies, was attributed to the surface polarization; surface states (Nss) and their relaxation time (τ). Main electrical parameters such as doping concentration of donor atoms (ND) and barrier height (ΦB(C–V)) were obtained from the reverse bias C−2–V plots for various frequencies. While the value of ND decreases, ΦB(C–V) increases with increasing frequency. The large values of C especially at low frequencies were attributed to the high dielectric graphene-doped PVA. C–V plots in depletion region show a distinctive anomalous peak such that its intensity increases with increasing frequency whereas its position shifts toward negative biases due to the effects Nss and series resistance (Rs). The plots of Nss versus V and Rs versus V are also obtained using low–high frequency capacitance (CLF–CHF) and Nicollian and Brews methods, respectively. Obtained results are promising considering the performance of capacitors in storing large amounts of charge, thus 7% graphene-doped PVA can be used as an alternative material for replacement of conventional silicon dioxide (SiO2).