The deposition and characterisation of metallic thin films and magnetic multilayers prepared by pulsed laser ablation deposition

• Main Author: Widdowson, Anna Marie
• Published: University of Warwick 1999
• Subjects: 530.41; QC Physics
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342514

This thesis investigates the use of pulsed laser deposition (PLAD) for the preparation of metallic films and magnetic multilayers. Initial work focuses on the effects of the laser wavelength and the laser pulse temporal profile on the deposition rates of nickel and silver and the droplet numbers deposited on to films. The results show that the deposition of silver films is affected by the sputtering of material from the substrate by energetic ions in the plasma and that this leads to saturation of the deposition rate at high fluences. The saturation features are not as pronounced in nickel deposition rates. We see that droplet numbers are only weakly dependent upon the laser wavelength, with fewer being present at shorter wavelengths. The effect that the number of pulses has on droplet numbers is also investigated. In the case of the pulse profile study more droplets were observed on films deposited using the picosecond (ps) pulse profiles. As for the nanosecond (ns) pulse profile the saturation in the deposition rates was observed in silver but not in nickel. The results of the ps laser pulse profiles showed that the ns background was dominant in the ablation process. Two further investigations into reducing droplet numbers were performed. These showed that a uniform beam profile was not sufficient for eliminating droplets from the PLAD process and that the use of a tape target in conjunction with a ps pulse profile did not reduce droplet numbers either. The aims of the second section of this thesis were to assess the suitability of PLAD for depositing multilayers and obtain PylPt multilayers showing a sensitive giant magnetoresistance (GMR) effect at low applied magnetic field. Samples prepared by two PLAD systems and by RF sputtering were compared. An anisotropic magneto resistance effect was measured, however GMR was not. The multilayer structures were characterised using x-ray reflectivity and cross sectional transmission electron micrographs. The results showed greater uniformity in the layers deposited by sputtering than PLAD.