Showing papers on "Single crystal published in 2005"
TL;DR: A review of surface science studies of single crystal surfaces, but selected studies on powder and polycrystalline films are also incorporated in order to provide connecting points between surface sciences studies with the broader field of materials science of tin oxide as discussed by the authors.
2,232 citations
TL;DR: This work reports a general approach for the fabrication of monodisperse, hydrophilic, and single-crystalline ferrite microspheres by a solvothermal reduction method, and is the first report on the synthesis of single- Crystalline magneticmicrospheres.
Abstract: It has been thought that many novel properties and potential applications would emerge from monodisperse materials with small dimensions. Therefore, the synthesis of monodisperse nanoparticles has been intensively pursued for their technological and fundamental scientific importance. The synthesis of nanostructured magnetic materials has become a particularly important area of research and is attracting a growing interest because of the potential applications such materials have in ferrofluids, advanced magnetic materials, catalysts, colored pigments, high-density magnetic recording media, and medical diagnostics. Spinel ferrites (MFe2O4; M = Fe, Mn, Zn, or Co) are among the most important magnetic materials and have been widely used in electronic devices, information storage, magnetic resonance imaging (MRI), and drug-delivery technology. 14] Magnetite (Fe3O4) has recently been considered an ideal candidate for biological applications, both as a tag for sensing and imaging, and as an activity agent for antitumor therapy. For high performance in function-specific biological applications, magnetic particles must be spherical and have smooth surfaces, narrow size distributions, large surface areas (for maximal protein or enzyme binding), high magnetic saturation (ss) to provide maximum signal, and good dispersion in liquid media. 18,19] After Sugimoto and Matijević reported the preparation of magnetite particles with a narrow size distribution in the early 1980s, monodisperse ferrite has been fabricated by various chemistry-based synthetic methods, including coprecipitation, the reverse micelle method, microwave plasma synthesis, solgel techniques, freeze drying, ultrasound irradiation, hydrothermal methods, laser pyrolysis techniques, and thermal decomposition of organometallic and coordination compounds. 9,14, 18, 20–27] However, most of these approaches were focused on the synthesis of ferrite particles limited to diameters below 30 nm. There are no reports on the synthesis of well-crystallized ferrite nanoparticles with sizes similar to protein molecules. The development of a facile and economic synthetic strategy for the synthesis of hydrophilic, biocompatible magnetite nanoparticles would benefit their technical use in biomedical fields, especially for applications in vivo. Herein we report a general approach for the fabrication of monodisperse, hydrophilic, and single-crystalline ferrite microspheres by a solvothermal reduction method. To the best of our knowledge, this is the first report on the synthesis of single-crystalline magnetic microspheres. The ferrite spheres had monodisperse diameters that were tunable in the range of 200–800 nm. This work resulted in an important method for obtaining various monodisperse, magnetic, and single-crystalline microspheres, and provided an opportunity to further apply these promising materials. Typical syntheses of Fe3O4 and ferrite microspheres were carried out in a solvothermal system by modified reduction reactions between FeCl3 and ethylene glycol. We confirmed the production of Fe3O4 by conducting controlled oxidation reactions in which aand g-Fe2O3 were produced (Supporting Information). 28–29] The crystalline structures of MFe2O4 were characterized by XRD. As shown in Figure 1, the
1,910 citations
546 citations
440 citations
TL;DR: In this article, the first measurements of magnetization hysteresis loops on a diluted single crystal of (Pc)2Ho]-·TBA+ in the sub-kelvin temperature range are reported.
Abstract: The first measurements of magnetization hysteresis loops on a diluted single crystal of [(Pc)2Ho]-·TBA+ (Pc = phthalocyaninato, TBA = tetrabutylammonium) in the subkelvin temperature range are reported. Characteristic staircase-like structure was observed, indicating the occurrence of the quantum tunneling of magnetization (QTM), which is a characteristic feature of SMMs. The quantum process in the new lanthanide SMMs is due to resonant quantum tunneling between entangled states of the electronic and nuclear spin systems, which is an essentially different mechanism from those of the known transition-metal-cluster SMMs. Evidence of the two-body quantum process was also observed for the first time in lanthanide complex systems.
424 citations
306 citations
TL;DR: A metal-organic honeycomb-like 2D pillared-bilayer open framework has been constructed which shows dynamic sponge-like single-crystal-to-single-Crystal transformation upon dehydration and rehydration.
Abstract: A metal−organic honeycomb-like 2D pillared-bilayer open framework has been constructed which shows dynamic sponge-like single-crystal-to-single-crystal transformation upon dehydration and rehydration. The dehydrated acentric nonporous phase transformed to the porous centric phase with the selective adsorbate concomitant with the structural transformation correlated with the single-crystal structure determination.
305 citations
TL;DR: It was deduced that the four phenyl groups substituted into the imidazole ring of HPI and HPI-Ac allowed the crystals free from concentration quenching of fluorescence by limiting the excessive tight-stacking responsible for intermolecular vibrational coupling and relevant nonradiative relaxation.
Abstract: We have synthesized a novel class of imidazole-based excited-state intramolecular proton-transfer (ESIPT) materials, i.e., hydroxy-substituted tetraphenylimidazole (HPI) and its derivative HPI-Ac, which formed large single crystals exhibiting intense blue fluorescence and amplified spontaneous emission (ASE). Transparent, clear, and well-defined fluorescent single crystals of HPI-Ac as large as 20 mm x 25 mm x 5 mm were easily grown from its dilute solution. From the X-ray crystallographic analysis and semiempirical molecular orbital calculation, it was deduced that the four phenyl groups substituted into the imidazole ring of HPI and HPI-Ac allowed the crystals free from concentration quenching of fluorescence by limiting the excessive tight-stacking responsible for intermolecular vibrational coupling and relevant nonradiative relaxation. Fluorescence spectral narrowing and efficient ASE were observed in the HPI-Ac single crystal even at low excitation levels attributed to the intrinsic four-level ESIPT photocycle.
299 citations
TL;DR: In this paper, the 2-inch ZnO single crystals were grown by the hydrothermal method using a platinum inner container and the electrical resistivity is highly uniform over the entire wafer area.
Abstract: Zinc oxide (ZnO) single crystals were grown by the hydrothermal method using a platinum inner container. The 2 inch ZnO wafers obtained from these bulk crystals possess an extremely high crystallinity and purity. The electrical resistivity is highly uniform over the entire wafer area. After annealing, the step-and-terrace structure was observed on the surface of the wafer. The etch pit density was decreased to less than 80 cm−2. These results suggest that these 2 inch ZnO wafers are suitable for wide band gap device applications.
278 citations
250 citations
TL;DR: The effect of high pressure on the crystal structures of α-, β-, and γ-glycine has been investigated in this article, where a new polymorph, δ-Glycine, was obtained from β glycine.
Abstract: The effect of high pressure on the crystal structures of α-, β-, and γ-glycine has been investigated. A new polymorph, δ-glycine, is obtained from β glycine. δ-Glycine is monoclinic, P21/a, a = 11.156(4), b = 5.8644(11), c = 5.3417(17) A, β = 125.83(4)° at 1.9 GPa. The transition, which occurs between 0 and 0.8 GPa, proceeds from a single crystal of β-glycine to a single crystal of δ-glycine, resulting in an equal number of NH···O hydrogen bonds but an increase in the number and strength of CH···O hydrogen bonds, which act to close-up “holes” that are formed within the layers of β-glycine in the centers of R-type hydrogen-bonded motifs. Trigonal γ-glycine begins to undergo a transition to another high-pressure phase, e-glycine, at 1.9 GPa, but the transformation is destructive; it is essentially complete at 4.3 GPa. The structure is monoclinic Pn, a = 4.8887(10), b = 5.7541(11), c = 5.4419(11) A, β = 116.682(10)° at 4.3 GPa. The structure consists of layers similar to those observed in α-glycine with inte...
TL;DR: In this paper, single crystal In(OH)3 nanocubes were synthesized by a designed novel hydrothermal treatment, and the size can be simply moderated by varying the Hydrothermal temperature.
Abstract: Single crystal In(OH)3 nanocubes were synthesized by a designed novel hydrothermal treatment, and the size can be simply moderated by varying the hydrothermal temperature By calcining the In(OH)3 nanocubes in air at 400 °C, single crystal In2O3 nanocubes were also prepared with the size slightly shrinking Room temperature photoluminescence showed a broad photoluminescence emission spectrum in the blue-green region with its maximum intensity centered at 450 nm, which was mainly attributed to the effect of the oxygen deficiencies
TL;DR: Nikl et al. as mentioned in this paper showed the structure of a Lu3Al5O12:Ce single crystal, a possible high performance scintillator material, whose scintillation performance is degraded by the occurrence of antisite defects.
Abstract: The cover picture of the current issue refers to the Rapid Research Letter by Martin Nikl et al. [1]. It depicts the structure of a Lu3Al5O12:Ce single crystal, a possible high performance scintillator material. Its scintillation performance is, however, degraded by the occurrence of antisite defects. Such defects arise in the material structure sketched in the figure due to the occurrence of Lu3+ ions at the Al3+ octahedral sites as seen in the middle left octahedron. This defect constitutes a shallow electron trap, which delays energy delivery to the Ce3+ emission centers, and thus slows down the scintillation response of the material. Thermoluminescence measurements appear as sensitive diagnostic tool to evidence these defects in the single crystals grown.
Martin Nikl is senior scientist and head of the Laboratory of Luminescence and Scintillation Materials at the Institute of Physics of the Czech Academy of Sciences. His main research activities include the characterization of the luminescence and scintillation properties of wide band-gap materials and the influence of material defects on them.
TL;DR: In this article, a two-step vapor phase transport method on sapphire was used to obtain high energy excitonic emission at low temperatures close to the band-edge which was assigned to the surface exciton in ZnO at $\ensuremath{\sim}3.366\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$.
Abstract: We report ZnO nanowire/nanowall growth using a two-step vapor phase transport method on $a$-plane sapphire. X-ray diffraction and scanning electron microscopy data establish that the nanostructures are vertically well aligned with the $c$ axis normal to the substrate and have a very low rocking curve width. Photoluminescence data at low temperatures demonstrate the exceptionally high optical quality of these structures, with intense emission and narrow bound exciton linewidths. We observe a high energy excitonic emission at low temperatures close to the band-edge which we assign to the surface exciton in ZnO at $\ensuremath{\sim}3.366\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$. This assignment is consistent with the large surface to volume ratio of the nanowire systems and indicates that this large ratio has a significant effect on the luminescence even at low temperatures. The band-edge intensity decays rapidly with increasing temperature compared to bulk single crystal material, indicating a strong temperature-activated nonradiative mechanism peculiar to the nanostructures. No evidence is seen of the free exciton emission due to exciton delocalization in the nanostructures with increased temperature, unlike the behavior in bulk material. The use of such nanostructures in room temperature optoelectronic devices appears to be dependent on the control or elimination of such surface effects.
TL;DR: The optical determination implies that the photoluminescence behavior of these In2O3 nanocrystals is different from that of the bulk, probably due to the combination of weak quantum-confinement-effects and the nature of high crystallinity in nanocry crystals.
Abstract: In this communication, we report a successful synthesis of quasi-monodisperse In2O3 nanocrystals with high crystallinity in a high-temperature organic solution. The average size of nanocrystals can be tuned using a dynamic injection technique. TEM and XRD investigations indicate that each nanocrystal is a single crystal. The optical determination implies that the photoluminescence behavior of these In2O3 nanocrystals is different from that of the bulk, probably due to the combination of weak quantum-confinement-effects and the nature of high crystallinity in nanocrystals.
TL;DR: In this paper, 1.1-at.%-Nd-doped YAG ceramics with controlled amounts of grain-boundary phase were fabricated by a solid-state reaction method using high-purity powders.
Abstract: For the present study, 1.1-at.%-Nd-doped YAG ceramics with controlled amounts of grain-boundary phase were fabricated by a solid-state reaction method using high-purity powders. The optical scattering loss of the Nd:YAG ceramics, obtained from Fresnels equation, increased simply with increased amounts of grain-boundary phase. The continuouswave laser output power of the Nd:YAG ceramics clearly was related to the scattering loss coefficients of the specimens that, in turn, were affected by the amount of grain-boundary phase. Although the scattering loss coefficients of Nd:YAG ceramics with grain-boundary-free structure and a lower pore volume (}150 vol ppm) were almost equivalent to those of a 0.9-at.%-Nd-doped YAG single crystal grown by the Czochralski method, the laser output power of the Nd:YAG ceramics exceeded that of the Nd:YAG single crystal with increased exciting power under excitation with an 808 nm diode laser because of the large amount of neodymium additives. Lasing performance was not affected by the existence of grain boundaries in the polycrystalline specimen.
TL;DR: In this article, a novel crystal growth method has been established for the growth of single crystal with selective orientation at room temperature using volatile solvent, the saturated solution containing the material to be crystallized was taken in an ampoule and allowed to crystallize by slow solvent evaporation assisted with a ring heater.
TL;DR: Growing nanobelts along different equivalent directions opens a new avenue for the preparation of novel nanostructured materials.
Abstract: Zigzag SnO2 nanobelts have been synthesized by evaporating tin grain in air. XRD, SEM, and TEM were employed to characterize the prepared samples. SEM images showed large amounts of zigzag nanobelts with periodic morphology. XRD result showed a pure tetragonal SnO2 phase. HRTEM and SAED revealed a single crystal structure with [010] zone axis on the whole zigzag zone. The zigzag structure is deduced to be formed by shifting the growth direction from [101] to [10] or vice versa. Growing nanobelts along different equivalent directions opens a new avenue for the preparation of novel nanostructured materials.
TL;DR: In this article, the formation of one-dimensional (1D) Fe3O4 nanostructures could be attributed to ethylenediamine, and the benzene used in this study is important to prevent ferrous ion to be oxygenated by oxygen in air.
TL;DR: In this article, the strengthening effects of Re and Ru additions in high refractory content single crystal Ni-base superalloys were investigated, and significant increases in flow stress were observed with the addition of Ru or Re.
TL;DR: Four diamine adducts of bis(hexafluoroacetylacetonato)zinc [Zn(hfa)(2).(diamine)] can be synthesized in a single-step reaction and single crystal X-ray diffraction studies reveal monomeric, six-coordinate structures.
Abstract: Four diamine adducts of bis(hexafluoroacetylacetonato)zinc [Zn(hfa)2·(diamine)] can be synthesized in a single-step reaction. Single crystal X-ray diffraction studies reveal monomeric, six-coordinate structures. The thermal stabilities and vapor phase transport properties of these new complexes are considerably greater than those of conventional solid zinc metal−organic chemical vapor deposition (MOCVD) precursors. One of the complexes in the series, bis(1,1,1,5,5,5-hexafluoro-2,4-pentadionato)(N,N‘-diethylethylenediamine)zinc, is particularly effective in the growth of thin films of the transparent conducting oxide Zn−In−Sn−O (ZITO) because of its superior volatility and low melting point of 64 °C. ZITO thin films with In contents ranging from 40 to 70 cation % (a metastable phase) were grown by low-pressure MOCVD. These films exhibit conductivity as high as 2900 S/cm and optical transparency comparable to or greater than that of commercial Sn-doped indium oxide (ITO) films. ZITO films with the nominal c...
TL;DR: The rational control of high-yield synthesis of piezoelectric ZnO nanosprings could open a new era in ZnNO-based electromechanical-coupled nanodevices.
Abstract: Zinc oxide, an important member in the II–VI group semiconductors, has profound applications in optics, optoelectronics, sensors, and actuators due to its semiconducting, piezoelectric, and pyroelectric properties. Structurally, wurtzite-structured ZnO has 13 fast growth directions: [0001], <011̄0> , and <21̄1̄0> ; 12 lower energy facets, {011̄0} and {21̄1̄0}; as well as a pair of polar surfaces, {0001}. These structural features allow ZnO to exhibit a group of unique and novel nanostructures, such as nanowires, nanotubes, nanobelts, nanocombs, nanosprings, nanorings, nanobows, nanojunction arrays, nanopropeller arrays, nanoplatelets, and nanodiskettes. The diversity and splendid nanostructures of ZnO could confer on it the same importance as that of carbon nanotubes for exploring nanoscale phenomena and devices. The single-crystal nanorings and nanosprings of ZnO, for example, are potential candidates for building semiconducting and piezoelectric resonators, actuators, and sensors for chemical and biological detection. It is necessary, as the first step, to synthesize nanosprings at high yield. However, the formation of nanosprings relies on nanobelts that are dominated by the {0001} polar surfaces, which have higher energy than the {011̄0} and {21̄1̄0} planes, and are energetically unfavorable to form during growth. An energy barrier has to be overcome by controlling growth kinetics to form polar-surface-dominated nanosprings. Therefore, the yield of nanosprings was lower than 5%, greatly limiting their application in electromechanical-coupled nanodevices. In this paper, we report the successful manipulation of growth kinetics to synthesize single-crystal ZnO nanorings at a high yield of more than 50%. This work pushes ZnO nanosprings from a scientific phenomenon to a practical material for carrying out a wide range of physical, mechanical, chemical, and biological experimental studies. The rational control of high-yield synthesis of piezoelectric ZnO nanosprings could open a new era in ZnO-based electromechanical-coupled nanodevices.
TL;DR: In this paper, high pressure recrystallisation of aqueous and methanolic solutions of piracetam (2-oxo-pyrrolidineacetamide) contained in a diamond-anvil cell at pressures of 0.07-0.4 GPa resulted in the formation of a new high-pressure polymorph of the drug, which has been characterised by in situ X-ray diffraction.
Abstract: High-pressure recrystallisation of aqueous and methanolic solutions of piracetam (2-oxo-pyrrolidineacetamide) contained in a diamond-anvil cell at pressures of 0.07–0.4 GPa resulted in the formation of a new high-pressure polymorph of piracetam that has been characterised by in situ X-ray diffraction. The molecular packing arrangement of the new form is very different from those of forms I, II, and III, and the piracetam molecules also adopt a very different conformation in this new phase. Depressurisation to ambient pressure resulted in the formation of form II via a single-crystal to single-crystal transition. By contrast, crystallisation of piracetam from water at ambient pressure resulted in the formation of a new monohydrate of piracetam, which has been characterised by single crystal X-ray diffraction.
TL;DR: In this paper, the fabrication and characterization of field-effect transistors based on single crystals of the organic semiconductor dibenzo-tetrathiafulvalene (DB-TTF) was reported.
Abstract: We report on the fabrication and characterization of field-effect transistors based on single crystals of the organic semiconductor dibenzo-tetrathiafulvalene (DB-TTF). We demonstrate that it is possible to prepare very-good-quality DB-TTF crystals from solution. These devices show high field-effect mobilities typically in the range 0.1–1?cm2/V?s. The temperature dependence was also studied revealing an initial increase of the mobility when lowering the temperature until it reached a maximum, after which the mobility decreased following a thermally activated behavior with activation energies between 50 and 60?meV. Calculations of the molecular reorganization energy and intermolecular transfer integrals for this material were also performed and are in agreement with the high mobility observed in this material.
TL;DR: The incorporation of hydrogen into wadsleyite (β-Mg 2 SiO 4 ) was investigated using poltarized FTIR spectroscopy and X-ray diffraction on oriented single crystals as mentioned in this paper.
Abstract: The incorporation of hydrogen into wadsleyite (β-Mg 2 SiO 4 ) was investigated using poltarized FTIR spectroscopy and X-ray diffraction on oriented single crystals. The experiments were carried out with a new suite of samples containing between ~100 and ~10 000 ppm H 2 O by weight (wt ppm), encompassing the H-contents most relevant to Earth’s potentially hydrous mantle transition zone. Attempts to synthesize anhydrous wadsleyite resulted in water contents of no less than ~50 wt ppm H 2 O. An empirical relation between the b / a axial ratio against estimated wt ppm concentrations of H 2 O in wadsleyite ( C H 2 O ) was determined: ( b / a ) = 2.008(1) + 1.25(3) × 10 −6 · C H 2 O Polarized infrared absorption spectra were measured in the three orthogonal sections perpendicular to the major axes of the optical indicatrix ellipsoid and are used in concert with results from new structure refinements to place constraints on the main absorbers in the structure. All of the main bands in the O-H stretching region of the FTIR can be explained by protonation of O1, the anomalous non-silicate oxygen site. We assign the band at 3614 cm −1 to a bent hydrogen bond O1···O1 (2.887 A) along the M3 edge in the a-c plane. The band at 3581 cm −1 is assigned to a bent hydrogen bond on O1···O3 (3.016 A) of the M3 edge in the b-c plane. The absorption bands at 3360, 3326, and 3317 cm −1 are best explained by hydrogen bonds on O1···O4 (3.092 A) and O1···O4 (2.795 A) along the M3 and M2 edges with possible splitting of one band due to vacancy ordering, but we cannot rule out contributions from three other (O1···O3) edges. The broad absorption feature at 3000 cm −1 is unambiguously assigned to the O4···O4 (2.720 A) tetrahedral edge of the Si 2 O 7 group pointing along the [100] vector. On hydration to ~1 wt% H 2 O, M-site vacancies are observed exclusively at M3. A systematic shortening of several (interpreted) hydrogen bonded O···O M-site edges is attributed to reduced O-O repulsive forces on protonation in the vicinity of an M-site vacancy.
TL;DR: In this paper, a review of single-crystal-to-singlecrystal (SCSC) reactions based on the [2+2] photodimerization is presented.
Abstract: The purpose of this review is to address fundamentals and applications of single-crystal-to-single-crystal (SCSC) reactions, based on the [2+2] photodimerization. An overview of SCSC [2+2] photodimerizations, which comprise single- and multi-component solids, will be given. We reveal that materials that exhibit SCSC reactivity can be considered to have been achieved via either discovery or design. We suggest that SCSC [2+2] photodimerizations, if generally achieved, could provide new avenues to control bulk physical properties of solid-state materials.
TL;DR: In this paper, the authors report the observation of ambipolar transport in field effect transistors fabricated on single crystals of copper and iron-phthalocyanine, using gold as a high work-function metal for the fabrication of source and drain electrodes.
Abstract: We report the observation of ambipolar transport in field-effect transistors fabricated on single crystals of copper- and iron-phthalocyanine, using gold as a high work-function metal for the fabrication of source and drain electrodes. In these devices, the room-temperature mobility of holes reaches 0.3?cm2/V?s in both materials. The highest mobility for electrons is observed for iron-phthalocyanines and is approximately one order of magnitude lower. Our measurements indicate that these values are limited by extrinsic contact effects due to the transistor fabrication and suggest that considerably higher values for the electron and hole mobility can be achieved in these materials.