KINETIC-ENERGY DISTRIBUTIONS OF IONS EJECTED DURING LASER-ABLATION OFLEAD-ZIRCONATE-TITANATE AND THEIR CORRELATION TO DEPOSITION OF FERROELECTRIC THIN-FILMS

Highly oriented lead zirconate titanate (PZT) has been deposited on Mg O(100) by pulsed laser deposition, using Nd:YAG (532 nm, 4 ns) laser r adiation, followed by subsequent annealing at 570 degrees C. An estima ted Pb/Zr + Ti ratio of 0.86, obtained from an as-deposited calibratio n curve, showed the formation of a lead depleted PZT thin film, The fu ll-width half-maximum (FWHM) of the PZT(001) peak decreased sharply as a function of increasing laser fluence indicated good crystallinity a t 12 J/cm(2) (FWHM 0.17 degrees). The effect of extended laser irradia tion on the durability of the target, the plume constituents and the s toichiometry of the PZT thin films was investigated by electron probe microanalysis and energy-dispersive mass spectrometry: The laser plasm a contained excess quantities of Pb+ ions at low fluences (1.67 J/cm(2 )) whilst congruent transfer was observed under high fluence (> 6 J/cm (2)) conditions. High laser fluence and the presence of oxygen serves to stabilise the PZT stoichiometry at temperatures (i.e. 570 degrees C ) which promote perovskite phase formation. Kinetic energy (KE) and ma ss spectrometric measurements were also used to characterise ionic spe cies generated in the ablation plume. Pb+, Ti+, TiO+, Zr+, ZrO+ and O ions were detected and showed a trimodal KE distribution with the low est energy peak constant between 10-40 eV. ZrO+ ions were also found t o be particularly stable within the laser ablation plasma with respect to TiO+ species. At moderate laser fluences (< 10 J/cm(2)) mean kinet ic energies of up to 180 eV of the ions were detected, The average KE increased linearly with laser fluence, with ion acceleration by electr on-ion space charge interaction the most likely mechanism.