Investigation of negative dielectric constant in Au/1 % graphene (GP) doped-Ca1.9Pr0.1Co4Ox/n-Si structures at forward biases using impedance spectroscopy analysis

Abstract

The dielectric properties of Au/(1 % graphene doped-Ca1.9Pr0.1Co4Ox)/n-Si structures were investigated by the impedance spectroscopy method including capacitance–voltage (C–V) and conductance–voltage (G/ω–V) measurements in the frequency range of 10–2 MHz at room temperature. The experimental results show that the real and imaginary parts of dielectric constant (e′, e′′) and electric modulus (M′ and M′′), and ac electrical conductivity (σ ac ) are a strong functions of frequency and voltage, both. Negative dielectric constant behavior was observed at sufficiently high forward bias voltages at low frequencies and it was attributed to the interfacial polarization, interface traps and series resistance. e′ decreases with increasing frequency at sufficiently high biases whereas e′′ increases. Since interfacial polarization and interface states, both, can follow the ac external signal easily at low frequencies, there occurs a contribution to the measured capacitance and conductance. The negative values of e′ correspond to maximum value of e′′. Such contrary behavior in the e′ and e′′ appears as an abnormality when compared to the conventional behavior metal–semiconductor structures with and without interfacial layer. Experimental results confirmed that the dielectric properties of these structures are quite sensitive to the frequency and applied bias voltage, both, especially at low frequencies and high voltages because of density distribution of interface states and interfacial polarization.