CHARACTERIZATION OF PB0.97ND0.02(ZR0.55TI0.45)O3 THIN-FILMS PREPARED BY PULSED-LASER ABLATION

Pulsed laser ablation was used to deposit Nd-doped lead zirconate titanate (PZT) thin films with thickness 100-200 nm from a Pb0.97Nd0.02(Zr0.55Ti0.45)O3 target. The films were ablated onto sapphire substrates with R -plane surfaces, without heating and at a pressure of 5 x 10(-5) mbar using a XeCl excimer laser (pulse energy about 50 mJ, wavelength 308 nm, pulse duration about 20 ns). Energy dispersive spectroscopy (EDS) of x rays was used for the composition analysis of both annealed and unannealed (amorphous) films deposited using various substrate-target distances and laser-beam fluences. It was found that the distance between target and substrate together with the laser-beam energy density on the surface of the target had a significant effect on the composition of the films. From the composition analysis, a suitable range of values was found for the target-substrate distance and fluence to deposit films with correct composition of each component. Lead deficiency was also found in the films in the case of high fluence (>1.5 J cm-2 with the target-substrate distance <40 mm), probably due to resputtering, while low fluence values (<1.0 J cm-2 with the target-substrate distance >40 mm) gave an excess of lead and too high Ti/(Zr+Ti) ratios. The films were annealed 2 h at 750-degrees-C with and without PZT powder. The composition analysis revealed that the films with an excess of lead before annealing had almost the correct amount of lead after annealing. On the other hand, it was not possible to compensate the lead deficiency through annealing in a lead atmosphere. EDS and x-ray diffraction were used to determine the crystal structure of annealed films. Trigonal and tetragonal perovskite structures were the major and minor phases of the films, respectively. Some Raman spectra measured from annealed films were found to be typical to PZT.