JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, vol.12, no.10, pp.2139-2144, 2010 (Journal Indexed in SCI)
The frequency and temperature dependence of dielectric constant (epsilon'), dielectric loss (epsilon ''), dielectric loss tangent (tan delta) and the ac electrical conductivity (sigma(ac)) of Au/Bi4Ti3O12/SiO2/Si (MFIS) structures were studied in the frequency range of 1 kHz-5 MHz and in the temperature range of 80-400 K. The dielectric parameters of MFIS structure were calculated from C-V and G/omega-V measurements. It was found that both dielectric and conductivity were quite sensitive to temperature and frequency at relatively high temperatures and at low frequencies. Experimental results show that the epsilon' and epsilon '' decrease with increasing frequency, while they increase with increasing temperature. On the other hand, the ac electrical conductivity (sigma(ac)) increases with increasing frequency and temperature alike. The interfacial polarization can be more easily occurred at low frequencies, and the number of interface states density between semiconductor/insulator interfaces, consequently, contributes to the improvement of dielectric properties of MFIS structure. The values of activation energy (E-a) were obtained from the slope of the Lnn vs q/kT plots, and found as 122.3 meV and 109.3 meV for 100 kHz and 500 kHz, respectively. In addition, the real (M') and imaginary (M '') components of the electrical modulus were calculated from the values of epsilon' and epsilon '' for two different frequencies. It was found that the values of real component M' decreases with increasing temperature up to room temperature, and then becomes independent of temperature and frequency.