713 research outputs found
Ruddlesden-Popper faults in LaNiO3/LaAlO3 superlattices
Scanning transmission electron microscopy in combination with electron
energy-loss spectroscopy is used to study LaNiO3/LaAlO3 superlattices grown on
(La,Sr)AlO4 with varying single-layer thicknesses which are known to control
their electronic properties. The microstructure of the films is investigated on
the atomic level and the role of observed defects is discussed in the context
of the different properties. Two types of Ruddlesden-Popper faults are found
which are either two or three dimensional. The common planar Ruddlesden-Popper
fault is induced by steps on the substrate surface. In contrast, the
three-dimensionally arranged Ruddlesden-Popper fault, whose size is in the
nanometer range, is caused by the formation of local stacking faults during
film growth. Furthermore, the interfaces of the superlattices are found to show
different sharpness, but the microstructure does not depend substantially on
the single-layer thickness.Comment: 14 pages, 6 figure
МНОГОФАЗНО-ОДНОФАЗНыЕ РЕВЕРСИВНыЕ ЭЛЕКТРОМАШИННО-ВЕНТИЛЬНыЕ ПРЕОБРАЗОВАТЕЛИ БЕСКОНТАКТНыХ МАШИН ДВОЙНОГО ПИТАНИЯ
Розглянуто процеси в багатофазно-однофазних реверсивних електромашинно-вентильних перетворю-
вачах безконтактних машин подвійного живлення.
Рассмотрены процессы в многофазно-однофазных реверсивных электромашинно-вентильных преобра-
зователях бесконтактных машин двойного питания
Combined Spectroscopy and Electrical Characterization of La:BaSnO Thin Films and Heterostructures
For La-doped BaSnO thin films grown by pulsed laser deposition, we
combine chemical surface characterization and electronic transport studies to
probe the evolution of electronic states in the band structure for different
La-doping content. Systematic analyses of spectroscopic data based on fitting
the core electron line shapes help to unravel the composition of the surface as
well as the dynamics associated with increasing doping. This dynamics is
observed with a more pronounced signature in the Sn 3d core level, which
exhibits an increasing asymmetry to the high binding energy side of the peak
with increasing electron density. The present results expand the current
understanding of the interplay between the doping concentration, electronic
band structure and transport properties of epitaxial La:BaSnO films.Comment: 7 Figures, 4 Tables in manuscript; and 6 Figures and 1 Table in the
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Negatively Charged In-Plane and Out-Of-Plane Domain Walls with Oxygen-Vacancy Agglomerations in a Ca-Doped Bismuth-Ferrite Thin Film.
The interaction of oxygen vacancies and ferroelectric domain walls is of great scientific interest because it leads to different domain-structure behaviors. Here, we use high-resolution scanning transmission electron microscopy to study the ferroelectric domain structure and oxygen-vacancy ordering in a compressively strained Bi0.9Ca0.1FeO3-δ thin film. It was found that atomic plates, in which agglomerated oxygen vacancies are ordered, appear without any periodicity between the plates in out-of-plane and in-plane orientation. The oxygen non-stoichiometry with δ ≈ 1 in FeO2-δ planes is identical in both orientations and shows no preference. Within the plates, the oxygen vacancies form 1D channels in a pseudocubic [010] direction with a high number of vacancies that alternate with oxygen columns with few vacancies. These plates of oxygen vacancies always coincide with charged domain walls in a tail-to-tail configuration. Defects such as ordered oxygen vacancies are thereby known to lead to a pinning effect of the ferroelectric domain walls (causing application-critical aspects, such as fatigue mechanisms and countering of retention failure) and to have a critical influence on the domain-wall conductivity. Thus, intentional oxygen vacancy defect engineering could be useful for the design of multiferroic devices with advanced functionality
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