Correlation of Ba:Gd ratio and film thickness to the dielectric, ferroelectric and leakage current mechanism of nanostructure Ba1-xGdxTiO3 thin films

Abstract

Perovskite Ba1-xGdxTiO3 thin films at different Ba:Gd ratios (0 = x ≤ 0.3, with 0.05 step) and film thicknesses have been fabricated in MFM configuration using sol-gel technique. The dielectric constant has been measured as a function of frequency in the range of 100 Hz and 1 MHz using impedance analyzer. The results show that at 1 kHz, ε decreases as Gd3+ ratio increases, which attributed to the reduction of tetragonality c/a ratio. Whereas, it increases as film thickness increases, which attributed to grain size increment. The ferroelectric hysteresis of the films is characterized using Sawyer-Tower circuit that shows a degradation for ferroelectric hysteresis as Gd+3 ratio increases due to permanent dipoles and grain size effect. Whereas, it enhances with film thickness due to grains enlargement. The leakage current has been analyzed via semiconductor parameter analyzer in the range from 0 to 8 V. It is found that at distinct electric field, the leakage current density reduces as Gd+3 ratio increases, resultant from grain size reduction. Whereas, it reduces as the film thickness increases according to inverse relation with film thickness. Moreover, SCLC, Schottky and Poole-Frenkel emission mechanisms have been modeled for the films to conclude that the former is the predominant mechanism.