Structural Investigation of B+ Ion Implantation Induced Amorphization in Polycrystalline Ni Thin Films

Abstract

High fluence metalloid ion implantation have been shown to induce amorphous phase formation in transition metals systems1,2 In this study Electron Energy Loss Spectroscopy (EELS) and Energy Filtered Selective Area Electron Diffraction (EFSAED) techniques have been employed along with conventional TEM to characterize the structural and electronic changes resulting from B+ ion implantation into polycrystalline Ni thin films.Polycrystalline Ni thin films of thickness ~500Å have been prepared by evaporating pure Ni (99.99%) onto commercial Bioden R.F.A. acetyl cellulose films in a vacuum of 5 × 106 Torr at room temperature. The TEM samples are obtained by dissolving the underlying acetyl cellulose layer using acetone wetting from below the TEM grids. The resulting films exhibit a continuous, non-textured fee polycrystalline rings pattern with an average grain size of 17 ± 4 nm.Ion implantation was performed in an implantation chamber using 50 keV B+ ions directed at normal incidence to the Ni TEM samples. The sample configuration consists of a -500 Å Ni energy degrader films on the 100 mesh Cu grids situated in front of the polycrystalline Ni thin films on the 300 mesh Cu grids. Such configuration maintains optimum efficiency of B+ ion implantation while producing a more homogeneous profile. After a total incident dose of 4.22x1017 ions/cm2, the implanted polycrystalline Ni thin films was transferred to the Philips EM420 electron microscope equipped with a Gatan (M-607) serial EELS detector for structural characterization.