Thickness dependence of the ferroelectric PbTiO3 thin films on the dipolar relaxation in the microwave-frequency range

The effects of film thickness on the dipolar relaxation of ferroelectric PbTiO3 thin films were investigated in the microwave-frequency range. The real and imaginary dielectric constants (ε′–iε″) were measured up to 30GHz using interdigital capacitors on high-quality SiO2. As the polycrystalline PbTiO3 film thickness increased from 42 to 407nm, the dipolar-relaxation frequency reduced with increasing grain size. The observed relaxation behavior for ε′–iε″ was explained in terms of the convolution of Debye relaxation. The relaxation frequency in the thin films was higher than the previous values reported in bulk PbTiO3, due to the smaller grain size of the thin films.