Dynamics of Laser Ablation and Vaporization of Lead Zirconate Titanate: Target Effects
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Dynamics of Laser Ablation and Vaporization of Lead Zirconate Titanate: Target Effects R.E. Leuchtner*, J.S. Horwitz, and D.B. Chrisey Naval Research Laboratory Washington, DC 20375 *- Current address: Department of Physics, University of New Hampshire, Durham, NH 03824 ABSTRACT Using the pulsed laser deposition (PLD) technique to prepare PbZrxTi(1-x)03 (PZT) films from stoichiometric targets, it has been found that the Pb content of the films is very sensitive to, among other parameters, the phase of the ablation target. In an effort to better understand PZT film growth, a time-of-flight quadrupole mass spectrometer (TOF/QMS) was used to obtain the temporal and mass profiles of material ejected from two different solid targets with a nominal composition of PbZr0.54TiO.4603 over a laser fluence range of 0.2 to 2.0 J/cm 2. The ablation targets were made from either a compressed mixture of oxides or a fully reacted PZT solid. The composition of the plume varied significantly depending upon the phase of the target and the laser fluence. In general, two distinct ejection processes were identified and the TOF profiles observed could be characterized as either thermal vaporization (fluence < 0.3 J/cm 2), ablation, with a highly forward directed ejection pattern normal to the target surface, or a combination of the two processes (fluences > 0.3 J/cm 2). The thermal vaporization (or low energy) component of the ejected species were modeled using a MaxwellBoltzmann distribution. The fully reacted target yielded atomic species which had higher translational temperatures (about 100-700K) than the corresponding components of the pressed oxide target. The translational temperatures ranged from about 1000-6500K, depending upon the species and the laser fluence. Both targets showed distinctly different behavior as a function of laser fluence with regard to the production of PbO: the PbO/Pb ratio from the pressed oxide target was roughly constant while the PbO/Pb ratio from the fully reacted target decreased significantly with increased laser fluence. It is postulated that PbO plays an important role in the incorporation of Pb into the film during film growth. INTRODUCTION Pulsed laser deposition (PLD) is becoming the method of choice for the preparation of multicomponent materials in thin film form. 1 The PLD process has gained considerable attention with regard to the preparation of high temperature (Hi Tc) superconducting thin films. Hi Tc films prepared by PLD have been used in microelectronic devices, for example in passive microwave filters, 2 and kinetic inductance delay lines. 3 Many other types of materials have been successfully deposited using PLD; these include metals, 4 biomaterials, 5 and ferroelectrics. 6 The intensity of research in ferroelectric thin films has been driven primarily by their attractiveness for use in non-volatile random access memory devices. One material, in particular, PbZrxTi(l-x)0 3 , or PZT, shows great promise for this application because of its intrinsically high remanent polarization and di
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