Polarization offsets of compositionally graded Nd-substituted Bi_4Ti_3O_(12) ferroelectric thin films

摘要

The vertical offsets of hysteresis loops of compositionally graded Nd-substituted Bi_4Ti_3O_(12) (BNdT) ferroelectric films were studied as functions of the Nd gradient, the temperature, and the amplitude of driving voltage. We show that graded BNdT films may exhibit no offsets at room temperature and both graded and nongraded BNdT films exhibit pronounced offsets at elevated temperatures. The offset does not have a direct relation with the composition gradient but increases as the maximum voltage is increased. It is verified that the offset increases with the increase in asymmetry of leakage currents at positive and negative biases.