Crystallographic Orientation Control of NanoCrystals Formed by FIB under a Bending Strain
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0908-OO16-02.1
Crystallographic Orientation Control of NanoCrystals Formed by FIB under a Bending Strain Masaki Kubota, Timothy P. Halford & Yakichi Higo Precision & Intelligence Laboratory, Tokyo Institute of Technology, 4259-R2-18, Nagatsuta, Midori-ku, Yokohama 226-8503, Japan ABSTRACT: The application of nanocrystalline material for data-storage applications requires control over the in-plane and out –of-plane NanoCrystal (NC) orientation. In order to attempt to control the out-of-plane orientation of NCs introduced by the irradiation of Ni-P material with Ga+ ions, this processing has been completed upon material under tensile and compressive strains. The orientations of NCs nucleated have been compared to those introduced into the same material without the application of an external strain. Samples introduced under no external strain have previously been shown to be oriented with parallel to the irradiated plane normal and parallel to the irradiation direction. In this work, NCs nucleated under tensile strains in excess of ≈ 2 x 10-3 have been oriented with parallel to the irradiated plane normal and parallel to the applied stress direction, although is still parallel to the irradiation direction. NCs formed under tensile strains lower than this critical value, as well as those formed under the compressive strain values tested, have been formed in the same orientation as those formed without the application of an external strain. KEYWORDS: Amorphous, Nanocrystallization, Ion beam, Orientation 1. INTRODUCTION Oriented nickel NanoCrystals (NCs) have previously been formed in Ni-11.5wt.%P amorphous alloy thin film as a result of Focused Ion Beam (FIB) irradiation by Ga+ ions at 30keV [1, 2]. Exposure, using a beam direction parallel (±20°) to the sample surface has been shown to avoid gallium implantation into the material [3]. Application of a Ga+ ion beam perpendicular to the sample surface can return NanoCrystalline regions to the amorphous state, as well as introducing ≈ 8at.% gallium [3, 4]. The NCs formed within the amorphous matrix in this manner have a maximum grain size of approximately 10 nm, with {111} orientated parallel to the irradiated plane and parallel to the projected ion beam direction [1, 2]. In addition to utilizing a strengthening effect [5], orientation control of NCs formed in similar amorphous materials would allow potential application of their magnetic properties for data storage. NCs orientated to two variants of {111}, with a twin relation on the irradiated plane have been generated using irradiation parallel ± 20°, whilst angles in the range 35o - 40o and 50° - 60°, have provided single variant {111} NCs of changing in-plane orientation [6]. Variations in irradiation angle have not, however, been sufficient to control the out of plane orientation of formed NCs. This has been attempted through NC formation by ion irradiation under varied tensile and compressive bending strains.
0908-OO16-02.2
2. EXPERIMENTAL PROCEDURE Ni-11.5wt.%P amorphous alloy thin film, with a thickness of 12μ
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