Electrical properties of compositionally graded lead calcium titanate thin films

The compositional gradient (Pb1−xCax)TiO3 (PCT) thin films of x=0 and 24 mol% were fabricated on Pt/Ti/SiO2/Si substrates by using a modified sol–gel process. The final structure consists of two layers, up-graded films starting from PbTiO3 on the Pt electrode to the top PCT(24) layer, whereas films with opposite gradient are called down-graded films. Highly (100)-oriented graded PCT thin films have been obtained when the graded PCT thin films were annealed at 600 °C. At 100 kHz, the dielectric constants were 79 and 128, respectively, for the up-graded and down-graded PCT films. The pyroelectric coefficient (p) of the graded films was measured by a dynamic technique. At room temperature, the values of p and figure-of-merits (FD) of the up-graded and down-graded PCT films are 95 μC/m2 K and 9.1×10−6 Pa−0.5, 112 μC/m2 K and 8.6×10−6 Pa−0.5, respectively.