Investigation of Intermixing/Implantation in Pulsed Laser Deposited Metallic Cr/Ni80Fe20 and Ni80Fe20/Polypyrrole Multilayer Thin Films

Abstract

Cr/Ni80Fe20 and Ni80Fe20/Polypyrrole multilayer thin films were prepared by pulsed laser deposition in vacuum and in Argon background gas at different pressures. Intermixing/implantation at their interfaces were investigated by scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS) analysis. Surface morphology (step height and roughness) of these samples were carried out by atomic force microscopy (AFM) and magnetic property (saturation magnetic flux) measurement by hysteresis loop tracer. The magnetic and surface morphology characterisations were used to calculate the interfacial mixing and/or implantation depth which have been found to agree with direct measured values. A correlation of these intermixing depths with Monte Carlo simulations of ion bombardment in the deposition process, using Stopping range of ion in matter (SRIM) incorporated with Transport of ion in matter (TRIM) gave the energy of the most implanted ionic species in a very simple way. Under high vacuum pressure, intermixing/implantation depth at the interfaces was high and occurs due to the presence of energetic species in the ablated plasma plume. With Argon gas background of increasing pressure, a reduction in energetic species energy is followed with a decrease in intermixing/implantation depth and the scattering of the ablated species leads to a decrease in the growth rate of Cr. An Argon background gas pressure of 20 mTorr gave the kinetic energy of the most energetic Cr species as 150 eV (from simulation) with 0.61 nm intermixing/implantation depth, while the vacuum pressure of 1.3 × 10− 7Torr gave the most energetic Cr energy as 3.2 keV with 2.38 nm depth of intermixing. Vacuum pressure 5 × 10− 7Torr with deposition of Permalloy (Py) Ni80Fe20 into polypyrrole gave measured intermixing/implantation depths of 6.81 nm with Ni80Fe20 energy of about 800 eV. The surface of the Py/polypyrrole (Ppy) was very rough at vacuum pressure 5 × 10− 3 Torr deposition as confirmed by the atomic force microscope measurement and STEM image than under background gas pressure 1 × 10− 3 Torr deposition. This is helpful for stoichiometric preparation of metallic multilayer thin films with well defined individual sharp interfaces and surface.