Effects of Frequency and Bias Voltage on Dielectric Properties and Electric Modulus of Au/Bi4Ti³O¹²/n-Si (MFS) Capacitors

15985

In this work, a metal-ferroelectric-semiconductor (MFS) type capacitor was fabricated and admittance measurements were held ina wide frequency range of 1 kHz-5 MHz at room temperature for the investigation of frequency and voltage dependence of complexdielectric constant, complex electric modulus and electrical conductivity of the MFS capacitor. Bismuth titanate (Bi4Ti3O12) withhigh dielectric constant was used as interfacial ferroelectric material and the structure of MFS capacitor was obtained asAu/Bi4Ti3O12/n-Si. Experimental results showed that dielectric, modulus and conductivity parameters are strong functions offrequency and voltage especially in depletion and accumulation regions due to the existence of surface states (Nss), series resistance(Rs), interfacial polarization and interfacial layer. It was found that Rs of the structure and interfacial ferroelectric layer are efectivein accumulation region whereas surface states (Nss) and interfacial polarization are efective in depletion region. Also the changesin dielectric, modulus and conductivity parameters become considerably high particularly at low frequencies due to high values ofRs and Nss. The observed anomalous peak in voltage dependent plots of capacitance and dielectric constant was atributed to theparticular density distribution of Nss, Rs and minority carrier injection. Moreover, the value of conductivity at low and intermediatefrequencies is almost independent of frequency thus low frequency data was used to extract d.c. conductivity. This work showedthat the use of high-dielectric Bi4Ti3O12 as ferroelectric interfacial layer in a MFS capacitor is preferable due to high values of itsdielectric constant compared with traditional insulator layer materials such as SiO2 and SnO2. Therefore, a MFS capacitor withBi4Ti3O12 interfacial layer can store more energy thanks to its high dielectric constant.

1003

MFS capacitors , frequency and voltage dependence , surface states and interfacial polarization , dielectric properties and electrical modulus

Journal Of Polytechnic

1008

Journal Of Polytechnic