High Structural Quality (high + structural_quality)

Distribution by Scientific Domains


Selected Abstracts


Growth and characterization of near stoichiometric LiNbO3 single crystal

CRYSTAL RESEARCH AND TECHNOLOGY, Issue 2 2007
S. H. Yao
Abstract A near stoichiometric LiNbO3 single crystal has been grown by the Czochralski method from a 58.5% Li melt hold in a large platinum crucible. High resolution X-ray rocking curves of 300 and 0006 reflections indicated that the near stoichiometric LiNbO3 crystal possesses the high structural quality. Compared with the congruent LiNbO3, the near stoichiometric LiNbO3 possesses shorter ultraviolet absorption edge, thus higher Li concentration. The OH, infrared absorption band analyses showed that the Li concentration in the near stoichiometric LiNbO3 crystal is higher than that in the congruent LiNbO3 crystal. This result is in good agreement with that of the ultraviolet absorption edge. The electro-optic (EO) coefficient ,22 of the near stoichiometric LiNbO3 crystal was measured to be 6.75 pm/V higher than that of congruent LiNbO3 crystal. It also proves the near stoichiometric LiNbO3 electro-optic Q-switched requires a low driving voltage and it is advantageous for the device performance. ( 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


High-Conductivity Polymer Nanocomposites Obtained by Tailoring the Characteristics of Carbon Nanotube Fillers,

ADVANCED FUNCTIONAL MATERIALS, Issue 20 2008
Nadia Grossiord
Abstract We present a detailed study of the influence of carbon nanotube (CNT) characteristics on the electrical conductivity of polystyrene nanocomposites produced using a latex-based approach. We processed both industrially-produced multi-wall CNT (MWCNT) powders and MWCNTs from vertically-aligned films made in-house, and demonstrate that while the raw CNTs are individualized and dispersed comparably within the polymer matrix, the electrical conductivity of the final nanocomposites differs significantly due to the intrinsic characteristics of the CNTs. Owing to their longer length after dispersion, the percolation threshold observed using MWCNTs from vertically-aligned films is five times lower than the value for industrially-produced MWCNT powders. Further, owing to the high structural quality of the CNTs from vertically-aligned films, the resulting composite films exhibit electrical conductivity of 103,S m,1 at 2,wt% CNTs. On the contrary, composites made using the industrially-produced CNTs exhibit conductivity of only tens of S m,1. To our knowledge, the measured electrical conductivity for CNT/PS composites using CNTs from vertically-aligned films is by far the highest value yet reported for CNT/PS nanocomposites at this loading. [source]


Optical studies on paramagnetic/superparamagnetic ZnO:Co films grown by magnetron sputtering

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2010
Limei Chen
Abstract A series of Zn0.9Co0.1O thin films was grown by UHV-magnetron reactive sputtering at different Ar:O2 flow rates. Decreasing the oxygen flow rates towards oxygen deficient growth lowers the structural quality of the films. Furthermore, it alters the magnetic properties of the films measured by SQUID magnetometry. Paramagnetic behaviour was observed for samples of high structural quality grown under optimized conditions whereas superparamagnetism was observed for oxygen deficient samples due to the emergence of magnetic clustering. Optical spectroscopic methods such as Raman spectroscopy, transmission and photoluminescence reveal that the altered growth conditions even affect the optical spectra of the films, and indicate that the magnetic properties are strongly associated with the structural quality of the ZnO:Co films. ( 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Optical characterization of bulk GaN substrates with c -, a -, and m -plane surfaces

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue S2 2009
P. P. Paskov
Abstract Thick free-standing GaN grown by hydride vapour phase epitaxy and epi-ready substrates with c -, a -, m -plane surfaces are examined by variable-temperature photoluminescence (PL), polarized PL and spatially resolved micro-PL. Both as-grown samples and polished substrates exhibit linewidth of the donor-bound exciton emission below 0.7 meV at 2 K indicative of a high structural quality of the material. For as-grown samples the relative intensity of green (2.4 eV) and red (1.8 eV) deep-level-defect emissions are found to decrease with increasing sample thickness. Based on plentiful two-electron-transition spectra measured in the samples the electronic fine structure of the donors and their bound-exciton complexes was examined and discussed. ( 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]