Constantin G. Tretiatchenko

Three-dimensional computer simulations of high-Tc epitaxial film growth

Abstract A three-dimensional Monte Carlo model of the anisotropic thin film growth has been developed. The model assumes on-lattice positioning of growth units and directional interaction between them, it takes into account processes of reevaporation and thermal hopping of the growth units, and involves anisotropic bond energies as parameters. Using this model the dependences of the film morphology on the substrate temperature and supersaturation can be computed. The model allows one to explain experimentally observed complicated transformations of the surface morphology as the substrate temperature is varying. It also allows one to predict the preferential orientation of the growing film and the density of defects.

Influence of planar defects on mixed state dynamics of high-Tc epitaxial films

Abstract The resistive state behaviour of YBa 2 Cu 3 O 7 films deposited by laser ablation has been studied. The analysis of the creep and viscous flux flow regimes allowed to conclude that the one dimensional “easy slip channels”, within which vortices preferably move, play an important role. Such channels arise at planar defects (twin boundaries). Easy slip regime has been observed at temperatures above t ⩾ T/T c ⋍ 0.9 , where drastic decrease of elementary pinning force occured.

Defects-induced thermal instability in YBCO films in microwave field

Abstract The heat instability induced by linear defects is assumed to enhance the remarkable difference between microwave properties of YBCO single crystals and thin films due to extended strain fields near out-of-plane edge dislocations. We have shown theoretically and confirmed experimentally that a single dislocation cannot have a strong effect on the surface resistance R s , but dislocation arrays, which were observed experimentally, can induce the thermal instability, if edge dislocations in the arrays are spaced closer than the heat relaxation length. Ordered dislocation structures provide much higher local temperature perturbation than randomly distributed dislocations.