A X-ray topography investigation of the microdeformation of oriented bicrystals of silicon

Abstract

Force field calculations can be used in three--dimensional crystallography as an aid in structure solution, and are particularly useful in the case of disordered crystals. When the molecules can be treated as rigid objects the study of thermal vibrations and rotations is quite feasible and the potential to be included in dynamic calculations is easily obtained. In two-dimensional crystallography the method is now more useful, since the alternative tec'hnique, multiple scattering theory in a trial and errOT procedure, is very time consuming and, at least for organic adsorbates on metal surfaces, not completely reliable. The results from molecular mechanics calculations can provide the screening to eliminate energetically unfavoured structures. Ion implantation in ferrirnagnetic garnet epilayers supporting bubbles has been primarily developped "ith the aim of overcoming bubble dynamic conversion, i.e. a process resulting in a drastically reduced bubble mobility. Besides, boundaries bet,,,een implanted and non-implanted regions define propagation paths for the bubbles tvhich are attached to the boundaries by so-called "charged walls tl •It is now widely accep.t-ed that stresses/strains around implantation boundaries control the morphology' and the dynamic behaviour of Hcharf,ed walls ll • In order to allow for a full understanding of ll charged walls" properties, stress/strain profiles around planar implantation boundaries have been derived accordinf to the methodology belo,,:I) the dilation of the implantation was first rocking curve analysis iynamical theory; p lattice, E: ;z (z), due to uniform determined by means of plane \Vave according to X-Ray diffraction 2) a model of the stress/strain distribution based on a distribution of edge dislocations with Burgers vectors p b(z) = f (s zz) was then constructed;3) the results of the strain calculation were compared to experimental data obtained by means of plane wave X-Ray imaging with varying incidence angles; 4) finally, the stress-induced easy magnetization directions were deduced from the stress calculations. ttesults pertaining to garnet epilayers implanted with Neon or Hydrogen ions will be described and discussed.It will be shown that stress-induced anisotropy predicts "charged walls" properties 't.J'hich agree with experimental data" at distances frOID the boundary exceeding a fraction of a micron. In particular, the observed three-fold symmetry in the propagation of "charged walls" may easily be deduced from the present elas'tic model. Hmvever, in the close vicinity ·of an implantation boundary, the complex spatial dependence of the various stress components imposes a three-dimensional treatment of implantation boundaries magnetoelastic properties. ~£~~£~!~Qg~~~~!~:The author is indebted to Ph. Gerard from LETI-Grenoble, France, for providing the implanted samples used in the present work. X-3A When helped by stress concentrations developed by pile-ups, other dislocations could cross the boundary. The correspondence between the slip systems activated in adj...