CMOS-compatible dense arrays of Ge quantum dots on the Si(001) surface: hut cluster nucleation, atomic structure and array life cycle during UHV MBE growth

We report a direct observation of Ge hut nucleation on Si(001) during UHV molecular beam epitaxy at 360°C. Nuclei of pyramids and wedges were observed on the wetting layer (WL) (M × N) patches starting from the coverage of 5.1 Å and found to have different structures. Atomic models of nuclei of both hut species have been built as well as models of the growing clusters. The growth of huts of each species has been demonstrated to follow generic scenarios. The formation of the second atomic layer of a wedge results in rearrangement of its first layer. Its ridge structure does not repeat the nucleus. A pyramid grows without phase transitions. A structure of its vertex copies the nucleus. Transitions between hut species turned out to be impossible. The wedges contain point defects in the upper corners of the triangular faces and have preferential growth directions along the ridges. The derived structure of the {105} facet follows the paired dimer model. Further growth of hut arrays results in domination of wedges, and the density of pyramids exponentially drops. The second generation of huts arises at coverages >10 Å; new huts occupy the whole WL at coverages ~14 Å. Nanocrystalline Ge 2D layer begins forming at coverages >14 Å

Life events as antecedents and triggers of manifestation and recurrence of mental and somatic disorders

The purpose of the study is to assess the difference between the type of stressful life events, distressing feelings and coping strategies that precede mental and somatic disorders.Цель исследования – оценить разницу между типом стрессогенных жизненных событий, дистрессирующих чувств и копинг-стратегий, предшествующих рецидивами или манифестациям психических и соматических расстройств

Current hysteresis due to changes in magnetization of magnetic tunnel junctions by spin-polarized current

We measured the current-voltage characteristics of magnetic tunnel junctions using novel dielectric materials -diamond-like carbon and polyimide barriers-which have a well-controlled chemical composition. For most of our as grown samples we observed hysteresis loops which were independent of the barrier material chosen. Their non-reproducible shape was dependent on bias and external field. We ascribe the hysteresis to the existence of a dynamic change in the domain magnetization of the electrodes due to a feed-back mechanism between the tunnel current and the magnetic structure. In an external magnetic field the hysteresis loops vanish, and the current-voltage characteristics are reproducible