13 research outputs found
Close-circuit domain quadruplets in BaTiO nanorods embedded in SrTiO film
Cylindrical BaTiO3 nanorods embedded in (100)-oriented SrTiO3 epitaxial film
in a brush-like configuration are investigated in the framework of the
Ginzburg-Landau-Devonshire model. It is shown that strain compatibility at
BaTiO3/SrTiO3 interfaces keeps BaTiO3 nanorods in the rhombohedral phase even
at room temperature. Depolarization field at the BaTiO3/SrTiO3 interfaces is
reduced by an emission of the 109-degree or 71-degree domain boundaries. In
case of nanorods of about 10-80 nm diameter, the ferroelectric domains are
found to form a quadruplet with a robust flux-closure arrangement of the
in-plane components of the spontaneous polarization. The out-of-plane
components of the polarization are either balanced or oriented up or down along
the nanorod axis. Switching of the out-of-plane polarization with coercive
field of about V/m occurs as a collapse of a 71-degree cylindrical
domain boundary formed at the curved circumference surface of the nanorod. The
remnant domain quadruplet configuration is chiral, with the macroscopic
symmetry. More complex stable domain configurations with coexisting clockwise
and anticlockwise quadruplets contain interesting arrangement of strongly
curved 71-degree boundaries.Comment: Erratta - corrected error in Fig.
Migration kinetic of primary radiation defects at nonuniform irradiation
The migration of interstitial atoms and vacancies under nonuniform irradiation is theoretically studied. The possibility
of the formation of regions with increased concentration of point defects of certain kind in crystalls with low concentration
of dislocatios at the surface and at Bragg peak is demonstrated. The region of the penetration of interstitials beyond the irradiated area is estimated. It might be of order of 0.02 sm at the dislocation density 104 cm-2. The difference of the flows of interstitials and vacancies changes its sign in process of irradiation which can lead to different processes of macroscopic defect formation at the imitial stages of irradiation and in the stationary state