The role of nitrogen-related defects in high-k dielectric oxides: Density-functional studies

Using ab initio density-functional total energy and molecular-dynamics simulations, we study the effects of various forms of nitrogen postdeposition anneal(PDA) on the electric properties of hafnia in the context of its application as a gate dielectric in field-effect transistors. We consider the atomic structure and energetics of nitrogen-containing defects which can be formed during PDA in various N-based ambients: N2, N2+, N, NH3, NO, and N2O. We analyze the role of such defects in fixed charge accumulation, electron trapping, and in the growth of the interface SiO2 layer. We find that nitrogen anneal of the oxides leads to an effective immobilization of native defects such as oxygen vacancies and interstitial oxygen ions, which may inhibit the growth of a silica layer. However, nitrogen in any form is unlikely to significantly reduce the fixed charge in the dielectric.Peer reviewe

Few-body Studies at Nuclotron-JINR

Recent results on the deuteron analyzing powers in dp- elastic scattering obtained at Nuclotron (JINR, Dubna) are compared with the calculations performed within relativistic multiple scattering model. The data demonstrate strong deviation form the predictions at large angles in the cm

Photo-induced processes in heterogeneous nanosystems. From photoexcitation to interfacial chemical transformations

This article briefly reviews some of our recent work carried out both from an experimental point of view as well as from a theoretical perspective to gain further understanding of the events that take place in Heterogeneous Photocatalysis. Previously, the multitude of reports from our laboratory and from many others looked at the primary photocatalytic events as involving (a) absorption of light, (b) formation of the free (electrons and holes) and/or trapped charge carriers (Ti3+ and •OH radicals), and (c) reaction of pre-adsorbed acceptor or donor molecules with the relevant trapped carrier. Our recent work notes that this view is reasonable if the only purpose of photocatalysis is elimination of undesirable environmental pollutants. But when we begin to query how to render a process more efficient, we need to address the primary events following photoexcitation of the photocatalyst, which in most instances has been titanium dioxide (in the anatase form). Owing to the nature of light absorption by TiO2 we resorted to examining other metal oxides, most of which are dielectric insulators with very large bandgap energies, for example zirconia (ZrO2) and scandia (Sc2O3). These dielectrics have provided added information on the photophysical events, many of which are masked by the strong light absorption in titania. Despite some of our recent progress, much remains to be done for a fuller understanding of the events that occur at the surface, which we have often considered to be the greatest and most complex defect in metal oxide particulates

The limiting state of welded joints with adjacent sharp cavities under multiaxial static and cyclic loading

Translated from Russian (Report of the E.O. Paton Welding Inst., Kiev, 1996)Available from British Library Document Supply Centre-DSC:9023.190(VR-Trans--9094)T / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo

Late-glacial and Holocene palaeoenvironments in the Baltic Sea based on a sedimentary record from the Gdansk Basin

The focus of this study was the 11.55 m long sediment core 303700-7, which was retrieved from the Gdansk Basin during a cruise of RV ‘Poseidon’ within the frame of the Russian–German Project GISEB. The core was analysed for grain size, elemental chemical composition, organic carbon and palynological spectra. The age control was based on palynostratigraphy and 7 radiocarbon datings of bulk sedimentary organic matter. These data provide a high-resolution record of climatic and marine palaeoenvironments in the Gdansk Basin for the last ca. 13 kyr, from the Bølling to late Holocene time. Sedimentation rates were estimated to vary between 0.37 and 1.62 mm yr–1. Major variations in palaeosalinity were estimated from bromine concentrations in the sediment. This method allows the first quantitative reconstruction of palaeosalinity changes in the Baltic Sea, especially profound during the Littorina and Postlittorina periods (middle to late Holocene). In addition, grain size data indicated several Littorina transgressive–regressive stages and a few episodes of increased near-bottom current activity. Our results from the Gdansk Basin are consistent with palaeoceanographic data from other deep basins of the Baltic Sea and provide new insights into the regional Holocene history