Effects of strain gradient on charge offsets and pyroelectric properties of ferroelectric thin films

The Landau-Ginzburg-Devonshire theory is used to study the effects of the strain gradient due to the epitaxial stresses in ferroelectric thin films sandwiched between two different substrates. The polarization in the film is found to be nonuniform, resulting in charge offsets and an asymmetric hysteresis response with characteristics similar to those in compositionally graded ferroelectric materials. The authors’ results suggest that the charge offset and pyroelectric effects can also be produced with effect of the strain gradient in film. In addition, such effects are found to be sensitive to an applied load.