Crystalline properties of ferroelectric-relaxor PMN-PT thin films by pulsed laser deposition

The dielectric and crystalline properties of ferroelectric thin films of 0.9[Pb(Mg₁3/Nb₂3/)O₃]-0.1PbTiO₃ (.9PMN-.1PT) have been investigated. Ceramic targets of 0.9PMN-0.1PT with and without excess PbO were used for thin film deposition and were grown on substrates of SrTiO₃ LaAlO₃, MgO, and Pt/TiO₂/SiO₂/Si using pulsed laser ablation deposition. It was shown that the phase purity of the films was dependent on the film thickness. Furthermore we have shown that as the thickness of the films increases from 100nm to 600nm there is a progressive decline in the local strain and hence an improvement in the local crystallinity of the films. The dielectric constant for our films (3900 at 10KHz) is higher than previous reports on 0.9PMN-0.1PT films. We have also shown that there is considerable benefit in changing lower electrodes. The XRD shows that the films are highly c-axis orientated as grown on YBa₂Cu₃O₇ (001) or SrRuO₃ (001) and (111) orientated on Pt(111) lower electrodes. The sizes of the grains depend upon the nucleation density and the rate of growth onto the lower electrode used. Slower growth rates lead to excess of lead in the film at the grain boundaries while accelerated growth rates lead to higher porosity´s. It was shown that annealing for 1 hour at 600°C reduces porosity and improves surface quality.