Amorphization of Garnet by Ion Implantation

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AMORPHIZATION

OF GARNET BY

A. M. GUZMAN, T. YOSHIIE**, Carnegie-Mellon University,

ION IMPLANTATION* C. L. BAUER and M. H. Pittsburgh, PA 15213, USA.

KRYDER,

ABSTRACT Amorphization by ion investigated in films of garnet by transmission

implantation has been (SmYGdTm) 3Ga 04Fe 4.6012 electron microscopy, incorporating a special cross-sectioning technique. These films were produced by liquid phase epitaxy on (111) garnet substrates and subsequently implanted with ions of deuterium at 60 kX + and 2 doses ranging from 0.50 to 4.5x10 D /cm and ions of oxygen 110 keV and 2.+ doses ranging from 0.95 to 8.6x10 0 1cm . The amorphization process proceeds in separate stages involving the formation of isolated amorphous regions, merging of these regions into a continuous band and subsequent propagation of the amorphous band toward the implanted surface. Details of these processes are interpreted in terms of various atomic displacement mechanisms.

f

INTRODUCTION Ion implantation in magnetic garnet epitaxial thin films is of special interest because of its role in altering the magnetic anisotropy of garnet crystals. The effects of ion implantation recently been reported in various technical papers [1-3]. have From the viewpoint of the garnet crystal structure, the effect of ion implantation is to generate isolated vacancies and interstitials as well as displacements of the garnet ions from their regular lattice sites. As the implantation doses increase, however, the corresponding increase in lattice defects may be sufficient to induce a crystalline to amorphous transformation, thus rendering the implanted layer magnetically inactive since amorphous garnet is believed to be paramagnetic [4]. Komenou et al.[4) have investigated the amorphization of garnet films implanted with neon ions at 100 keV using a double-crystal diffraction technique. Their results indicate that the process evolves in three distinct stages involving the formation and propagation of an amorphous band. More recently, amorphization of garnet by ion implantation with deuterium and oxygen ions has been studied by Yoshiie et al. [5] using transmission electron microscopy (TEM). Their results show that the amorphization process evolves in three slightly different stages involving the initial formation of isolated amorphous particles at low implantation dose and the subsequent merging of these particles into an amorphous band at higher doses. We report on the investigation of the amorphization process of thin film garnets implanted with deuterium and oxygen ions by TEM, incorporating a special cross-sectioning technique. Direct observations of the structural changes and phase morphology are presented and discussed.

Mat. Res. Soc.Symp. Proc. Vol. 27 (1984) OElsevier science Publishing Co., Inc.

140

EXPERIMENTAL

TECHNIQUES

(SmYGdTm) Ga Fe 0 ,0 ranging Magnetic garnet films of 2 from 0.6 to 1.1 pm in thickness, were g0o.wn 4y quid phase (111) oriented Gd Ga 5 0 (GGG) substrates. epitaxy (LPE) on uniiormly implanted at room These films were subsequently t

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