Spontaneous pyro- and piezoelectricity of sol-gel La-modified lead titanate thin films

Polycrystalline La-modified lead titanate thin films have been processed, b y a diol-based sol-gel route, on Si-based substrates. Multiple deposition a nd crystallization steps were carried out in order to promote heterogeneous nucleation and, as a consequence, a preferred crystallographic orientation and self polarization. Crystallization was achieved by rapid thermal proce ssing at 650 degreesC for 50 s, at a heating rate of similar to 30 degreesC /s. The films developed either a < 111 > or a mixed < 100 >/< 001 > preferr ed orientation, which were determined by quantitative texture analysis of X -ray pole figures. Hysteresis cycles of the piezoelectric d(33) coefficient versus electric field were obtained by a double-beam laser interferometric technique and found to strongly depend on the film texture. < 111 > orient ed films present a thickness-dependent spontaneous pyroelectric coefficient and field endurance of the piezoelectric coefficient. These films are thus , appropriate to be used in non-switching applications, such as pyroelectri c infra-red detectors and integrated piezoelectric sensors.