Simulations of cubic-tetragonal ferroelastics

We study domain patterns in cubic-tetragonal ferroelastics by solving numerically equations of motion derived from a Landau model of the phase transition, including dissipative stresses. Our system sizes, of up to 256^3 points, are large enough to reveal many structures observed experimentally. Most patterns found at late stages in the relaxation are multiply banded; all three tetragonal variants appear, but inequivalently. Two of the variants form broad primary bands; the third intrudes into the others to form narrow secondary bands with the hosts. On colliding with walls between the primary variants, the third either terminates or forms a chevron. The multipy banded patterns, with the two domain sizes, the chevrons and the terminations, are seen in the microscopy of zirconia and other cubic-tetragonal ferroelastics. We examine also transient structures obtained much earlier in the relaxation; these show the above features and others also observed in experiment.Comment: 7 pages, 6 colour figures not embedded in text. Major revisions in conten

High Voltage Transmission Electron Microscopy of Low-Power Pulsed Laser Annealing of Zn-implanted GaAs

Crystals of (100) GaAs implanted with Zn+-ions were treated by low-power pulsed-laser annealing (LPPLA) technique. The first investigations about the effect of this treatment on the damage structure distribution in the GaAs by means of high voltage transmission electron microscopy are shown. Typical rearrangement and accumulation trends of the initially uniformly dispersed damage clusters were established after the LPPLA. The morphology of gallium oxide films grown on the surface of GaAs during LPPLA treatment and their specific behavior under electron bombardment during the observation in the microscope are reported too