Chiang Mai Journal of Science

In this study, dynamic pyroelectric properties of  La-doped PbTiO₃ (PLT) thin films with dopant  amounts  of  5,  10,  and  15mol%  have  been  investigated.  The  voltage  responsivity corresponding to the pyroelectric voltage is almost constant at low modulation frequency and decreases in proportional  to  the  frequency  at high modulation  frequency  for the PLT thin films of  three compositions. The noise voltages for the three compositions decrease with the square root of the modulation frequency due to the predominance of dielectric loss component in Johnson noise. Among the films investigated, the PLT thin film with 10mol% of  La (PLT(10) thin film) shows the best pyroelectric characteristics. The pyroelectric coefficient of  PLT(10) thin film is 6.6×10^-9 C/cm²K with no modulation frequency dependence. Its figures of merit for the voltage responsivity and specific detectivity are 1.03×10^-11 Ccm/J and 1.46×10^-9 Ccm/J, respectively. These results indicate that PLT(10) thin film is well applicable to the pyroelectric infrared sensor.