Investigation of the dielectric properties of Au/Bi4Ti3O12-SiO2/n-Si (MFIS) type structures depending on gamma-irradiation

Abstract

In this study, capacitance/conductance-voltage (C/G-V) measurements of the Au/(Bi4Ti3O12-SiO2)/n-Si (MFIS) structures were performed at 500 kHz before and after gamma-radiation doses (5 and 22 kGy). Both the real/imaginary parts of complex-dielectric (Ɛ′, Ɛ″) and electric-modulus (M′, M″), loss-tangent (tanδ), and AC electrical-conductivity (σac) were obtained before and after irradiation using the C/G-V data. A decrease in Ɛ′ and Ɛ″ values was observed with the impact of radiation, and this behavior can be explained by Koop's theory based on the Maxwell-Wagner type polarization. It was also foreseen that the ferroelectric material (Bi4Ti3O12), including as an interfacial layer, causes the structure to exhibit hysteric and asymmetrical behavior due to its polarization effect. The correction was made in the Ɛ′, Ɛ″, and tanδ to eliminate series-resistance (Rs) effects on them. It was determined that radiation-induced defects or surface states, and expansion of the depletion region significantly affect the dielectric parameters as well as the Rs. The obtained value of σac decreased with increasing radiation while the values of M′ and M″ increased. In conclusion, it has been determined that dielectric parameters of MFIS structure are strongly affected by the voltage and change considerably under radiation.