Showing papers on "Single crystal published in 1996"
TL;DR: In this paper, the magnetoresistance and the field dependent magnetization have been systematically examined in the low temperature ferromagnetic metallic state of single crystal and polycrystalline.
Abstract: The magnetoresistance (MR) and the field dependent magnetization have been systematically examined in the low temperature ferromagnetic metallic state of single crystal and polycrystalline ${\mathrm{La}}_{2/3}{\mathrm{Sr}}_{1/3}{\mathrm{MnO}}_{3}$. We find that the intrinsic negative MR in single crystal is due to the suppression of spin fluctuations, and magnetic domain boundaries do not dominate the scattering process. In contrast, we demonstrate that the MR in the polycrystalline samples exhibits two distinct regions: large MR at low fields dominated by spin-polarized tunneling between grains and high field MR which is remarkably temperature independent from 5 to 280 K.
1,594 citations
TL;DR: In this article, the electrochemical and photoelectrochemical behavior of a single crystal of anatase was scrutinized for the first time, and it was shown that anatase (101) and rutile (001) electrodes differ mainly in the position of the...
Abstract: Single crystals of TiO2 anatase containing 0.22% of Al and traces of V, Zr, Nb, and La were grown by chemical transport reactions employing TeCl4 as the transporting agent. Electrodes having the (101) face exposed doped by reduction with hydrogen were employed. The electrochemical and photoelectrochemical behavior of a single crystal of anatase were scrutinized for the first time. Properties were compared to those of single-crystal rutile having the (001) face exposed. Impedance analysis established that the flatband potential of anatase (101) is shifted negatively by 0.2 V with regards to that of rutile (001). Interfacial capacitance measurements under forward bias indicate smaller density of surface states on anatase. Photoelectrochemical oxidation of water occurs on both rutile and anatase with incident photon-to-current conversion efficiencies close to unity at λ = 300 nm. From the comparison of Ufb and Eg, it follows that anatase (101) and rutile (001) electrodes differ mainly in the position of the ...
1,311 citations
TL;DR: Deposited conductors made using this technique offer a potential route for the fabrication of long lengths of high‐Jc wire capable of carrying high currents in high magnetic fields and at elevated temperatures.
Abstract: A method to obtain long lengths of flexible, biaxially oriented substrates with smooth, chemically compatible surfaces for epitaxial growth of high‐temperature superconductors is reported. The technique uses well established, industrially scalable, thermomechanical processes to impart a strong biaxial texture to a base metal. This is followed by vapor deposition of epitaxial buffer layers (metal and/or ceramic) to yield chemically compatible surfaces. Epitaxial YBa2Cu3Ox films grown on such substrates have critical current densities exceeding 105 A/cm2 at 77 K in zero field and have field dependencies similar to epitaxial films on single crystal ceramic substrates. Deposited conductors made using this technique offer a potential route for the fabrication of long lengths of high‐Jc wire capable of carrying high currents in high magnetic fields and at elevated temperatures.
902 citations
TL;DR: In this article, the reaction of M(II) acetate hydrate (M = Co, Ni, and Zn) with 1,3,5-benzenetricarboxylic acid yields a material formulated as M3(BTC)2·12H2O.
Abstract: The reaction of M(II) acetate hydrate (M = Co, Ni, and Zn) with 1,3,5-benzenetricarboxylic (BTC) acid yields a material formulated as M3(BTC)2·12H2O. These compounds are isostructural as revealed by their XRPD patterns and a single crystal structure analysis performed on the cobalt containing solid [monoclinic, space group C2, a = 17.482 (6) A, b = 12.963 (5) A, c = 6.559 (2) A, β = 112.04°, V = 1377.8 (8) A, Z = 4]. This solid is composed of zigzag chains of tetra-aqua cobalt(II) benzenetricarboxylate that are hydrogen-bonded to yield a tightly held 3-D network. Upon liberating 11 water ligands per formula unit a porous solid results, M3(BTC)2·H2O, which was found to reversibly and repeatedly bind water without destruction of the framework. The proposed 1-D channels of the monohydrate have a pore diameter of 4 × 5 A, which is typical of those observed in zeolites and molecular sieves. The successful inclusion of ammonia into the porous solid was demonstrated. Larger molecules and others without a reactiv...
759 citations
TL;DR: Henderson et al. as mentioned in this paper used temperature-programmed desorption (TPD) and oxygen isotopic labeling studies to probe the dissociation of water on the (100) and (110) surfaces of TiO2 (rutile).
Abstract: Temperature-programmed desorption (TPD) and oxygen isotopic labeling studies were used to probe the dissociation of water on the (100) and (110) surfaces of TiO2 (rutile). Water TPD spectra from these two surfaces were distinctive. Three monolayer desorption states were observed for the (100) surface (at 205, 250, and 305 K), while only a single desorption state was observed for the (110) surface (at 270 K). TPD experiments on the surfaces enriched with 18O revealed that water desorbing in the 305 K state from TiO2(100) was isotopically scrambled with the lattice oxygen atoms, strongly suggesting that this TPD state resulted from recombination of surface hydroxyl groups. Isotopic scrambling was not observed for any other desorption state on either surface (in the absence of defects). Since very little water desorption occurred from the (110) surface in the temperature range in which exchange was observed on the (100) surface and since previous HREELS work (Henderson, M. A. Surf. Sci. 1996, 355, 151) indic...
457 citations
TL;DR: Ways to control film cracking during deposition and heat treatment and why many precursors synthesize metastable crystalline structures are discussed, and the different mechanisms that convert the polycrystalline film into a single crystal are reviewed.
Abstract: Epitaxial thin films of inorganic single crystals can be grown on single-crystal substrates with a variety of different solution chemistries. This review emphasizes chemical solution deposition, in which a solution is used to deposit a layer of precursor molecules that decompose to low-density, polycrystalline films during heating. Ways to control film cracking during deposition and heat treatment and why many precursors synthesize metastable crystalline structures are discussed, and the different mechanisms that convert the polycrystalline film into a single crystal are reviewed. Hydrothermal epitaxy, in which single crystal thin films are directly synthesized on templating substrates in an aqueous solution at temperatures <150°C, is also discussed.
408 citations
327 citations
TL;DR: In this paper, the structure of single lipid bilayers adsorbed to a planar silicon surface from aqueous solution was characterized using a novel experimental setup which significantly decreased the incoherent background scattering and allowed us to measure neutron reflectivities as low as 5 × 10-7 Thicknesses and neutron scattering length densities were determined by fitting procedure using (i) randomly generated smooth functions represented by parametric B-splines and (ii) stepped functions based on the theoretical lipid composition.
Abstract: Specular reflection of neutrons has been used to characterize the structure of single lipid bilayers adsorbed to a planar silicon surface from aqueous solution We used a novel experimental setup which significantly decreased the incoherent background scattering and allowed us to measure neutron reflectivities as low as 5 × 10-7 Thicknesses and neutron scattering length densities were determined by a fitting procedure using (i) randomly generated smooth functions represented by parametric B-splines and (ii) stepped functions based on the theoretical lipid composition The size of lipid domains at the surface and the degree of surface coverage were determined by atomic force microscopy Chain-protonated and -deuterated dipalmitoylphosphatidylcholine (DPPC) bilayers were investigated in 2H2O and a mixture of 2H2O and H2O which matches the scattering density of silicon Also, one measurement on a distearoylphosphatidylcholine bilayer which has longer acyl chains was performed for comparison The lipid adsor
302 citations
TL;DR: In this paper, the mechanical properties of (001), (011) and (111) oriented MgO wafers and 1μm-thick TiN overlayers, grown simultaneously by dc magnetron sputter deposition at 700 °C in a mixed N2 and Ar discharge, were investigated using nanoindentation.
Abstract: The mechanical properties of (001)‐, (011)‐, and (111)‐oriented MgO wafers and 1‐μm‐thick TiN overlayers, grown simultaneously by dc magnetron sputter deposition at 700 °C in a mixed N2 and Ar discharge, were investigated using nanoindentation. A combination of x‐ray‐diffraction (XRD) pole figures, high‐resolution XRD analyses, and Auger electron spectroscopy was used to show that all TiN films were single crystals with N/Ti ratios of 1.0±0.05. The nanoindentation measurements were carried out using a three‐sided pyramidal Berkovich diamond indentor tip operated at loads ranging from 0.4 to 40 mN. All three orientations of MgO substrates, as‐received, exhibited identical hardness values as determined using the Oliver and Pharr method. After a 1 h anneal at 800 °C, corresponding to the thermal treatment received prior to film growth, the measured hardness of MgO(001) was 9.0±0.3 GPa. All TiN films displayed a completely elastic response at low loads. Measured hardness values, which decreased with increasin...
238 citations
TL;DR: In this article, the role of hydrogen as inhibitor of methanol adsorption was confirmed once more by means of in situ FTIR spectra, which indicated that the splitting off of hydrogen atoms is superimposed on hydrogen desorption and gives rise to a well defined peak at polycrystalline and at Pt(100).
230 citations
TL;DR: In this paper, single-crystal niobium nitride (NbN) thin films were fabricated at ambient substrate temperature so that photoresist lift-off techniques could be used in fabricating Josephson tunnel junctions.
Abstract: Single‐crystal niobium nitride (NbN) thin films were fabricated at ambient substrate temperature so that photoresist lift‐off techniques could be used in fabricating Josephson tunnel junctions In this article, we describe the superconducting properties and crystal structure of the NbN films Even though the substrates were not heated, the NbN films had excellent superconducting properties: a high Tc of 16 K, low normal‐state resistivity (ρ20=62 μΩ cm), and residual resistivity ratios RRR=ρ300/ρ20 above one The film structures, which were investigated by x‐ray diffraction, electron diffraction patterns and transmission electron micrographs, show a single‐phase orientation without columnar and granular structures We have found that the superconducting properties depend on the lattice parameter, and the best films had a lattice parameter of 0446 nm NbN/AlN/Nb tunnel junctions were fabricated to measure the superconducting energy gap of the NbN films We estimated the energy gap ΔNbN to be 26 meV and th
TL;DR: In this article, the authors explore the origins of the capacitance dispersion observed for single crystal electrodes, voltammetric and impedance measurements on Au(l 11) and Au(100), in the absence and the presence of specifically adsorbed anions, mostly Br−, have been carried out.
TL;DR: In this paper, the potential dependent bands near 3100 and 1620 cm−1 correspond to the O-H stretching and H-O-H in-plane deformation of adsorbed water molecules.
TL;DR: In this paper, the electrochemical oxidation of glucose has been studied in phosphate buffer (pH = 7.4) on single crystal and polycrystalline gold electrodes using electrochemical techniques, ex situ NMR, in situ FTIR spectroscopy, and isotope labeling.
Abstract: The electrochemical oxidation of glucose has been studied in phosphate buffer (pH = 7.4) on single crystal and polycrystalline gold electrodes using electrochemical techniques, ex situ NMR, in situ FTIR spectroscopy, and isotope labeling. Under these conditions, the results indicate that the rate determining step for the electro-oxidation of glucose is bond breaking between the hydrogen atom and the C 1 carbon atom. Gluconolactone appears to be an intermediate and sodium gluconate is the reaction product. First order kinetics with respect to glucose were also found. Gold would be a useful electrode for sensor applications, if the inhibition of the glucose oxidation by the adsorption of Cl - could be avoided
TL;DR: In this paper, a La 3 Ga 5 SiO 14 (LGS) single crystal with dimensions of 1 or 2 inch in diameter was grown using the Czochralski technique.
TL;DR: In this paper, X-ray photoelectron spectroscopy and ex situ scanning tunneling microscopy measurements have been combined to investigate the thickness, the chemical composition, and the structure of passive films formed in 0.5 M H{sub 2}SO{sub 4} on Fe-22Cr(110).
Abstract: X-ray photoelectron spectroscopy and ex situ scanning tunneling microscopy measurements have been combined to investigate the thickness, the chemical composition, and the structure of passive films formed in 0.5 M H{sub 2}SO{sub 4} on Fe-22Cr(110). Aging under polarization at +500 mV/SHE causes a dehydration (anodic) reaction of the outer chromium hydroxide layer of the passive film. This anodic reaction results in a thickening of the inner mixed Cr(III) and Fe(III) oxide layer enriched in Cr{sub 2}O{sub 3}. It also causes a coalescence of the oxide nuclei of the passive film and a crystallization of the inner Cr{sub 2}O{sub 3}. It also causes a coalescence of the oxide nuclei of the passive film and a crystallization of the inner Cr{sub 2}O{sub 3} oxide layer in epitaxy with the substrate. The epitaxial relationship is {alpha}-Cr{sub 2}O{sub 3}(0001) {parallel} Fe-22Cr(110) with three different azimuthal orientations. Aging under polarization is beneficial to the stability of the passive film in air and prevents the dehydration reaction of the hydroxide coupled to an oxidation reaction of iron which are observed on freshly passivated surfaces. Polarization at +700 mV/SHE activates the dissolution of substrate terrace atoms whereas polarization at +300 or + 500 mV/SHE activates the dissolutionmore » of substrate atoms at step edges only.« less
TL;DR: In this paper, the physical and chemical properties of the Au(hkl) surface were investigated by rotating disk electrode and rotating disk ring electrode techniques, with a goal to correlate the physicochemical properties of electrode surface with its catalytic activity.
TL;DR: In this article, the water desorption rate from nanoscale thin films of water vapor deposited on Au(111) and Ru(001) single crystal metallic substrates was studied.
TL;DR: In this paper, the crystal structures of ReSe, ReS., ReSSe, and TeS2 were determined using single crystal X-ray diffraction, and the compounds are triclinic with space groupPl.
TL;DR: In this article, a combination of molecular beam reflection and temperature programmed desorption techniques was used to study adaption of water on well-ordered and sputter-damaged single crystal MgO(100) surfaces.
Abstract: Adsorption and desorption of water on well‐ordered and sputter‐damaged single crystal MgO(100) surfaces were studied by a combination of molecular beam reflection and temperature programmed desorption techniques. Adsorption exhibits precursor‐mediated kinetics and desorption exhibits a strong dependence on substrate treatment, demonstrating the importance of surface defects.
TL;DR: In this article, a grazing-incidence X-ray absorption fine structure (GI-XAFS) measurement was performed on α-Al2O3 (0001) single crystal surface.
TL;DR: In this paper, it is shown that the epitaxial film grown on CoO(100) at 625 K and 5×10−7 Torr is Co3O4-like in both oxygen content and XP/HREEL spectroscopic characteristics.
Abstract: Under mildly oxidizing ultrahigh vacuum conditions, it is possible to form on top of CoO(100) single crystal substrates, thin films that have higher oxygen content but that preserve the overall symmetry of the CoO(100) low‐energy electron diffraction pattern. X‐ray photoelectron spectroscopy (XPS) and high‐resolution electron‐energy‐loss spectroscopy (HREELS) data indicate that the epitaxial film grown on CoO(100) at 625 K and 5×10−7 Torr is Co3O4‐like in both oxygen content and XP/HREEL spectroscopic characteristics. Both materials are closest packed in lattice oxygen, with the mismatch of bulk O2−–O2− distances of approximately 5%. However, the Co3O4 is only able to grow to a thickness of approximately 5 A before the oxidation process halts. It is proposed that the orientation of Co3O4 that forms most readily on the CoO(100) surface does not present a thermodynamically stable orientation of the bulk Co3O4 substrate but is that which grows under the constraint of the best CoO(100)/Co3O4 epitaxial arrange...
TL;DR: In this article, the elastic constants of single crystals of several intermetallic compounds have been measured in our laboratory by the rectangular parallelepiped resonance method, and the numerical results for materials measured so far: Ni-base L12 compounds Ni3X (X = Mn, Fe, Al, Ga, Ge and Si), TiAl, Ti3Al, CoTi, Co3Ti and CoSi2
TL;DR: In this paper, a series of neutron single-crystal structure refinements at five temperatures ranging from 175 K, where Arrhenius behaviour holds, down to 20 K where translational tunnelling is dominant.
Abstract: Hydrogen-atom transfer across the hydrogen bonds of benzoic acid dimers has been studied previously by spectroscopic and X-ray methods, but no high-resolution neutron single crystal structures have ever been reported. The system is of interest because the hydrogen-atom dynamics change from classical Arrhenius behaviour to phonon-assisted quantum tunnelling as a function of decreasing temperature. Here we present a series of neutron single-crystal structure refinements at five temperatures ranging from 175 K, where Arrhenius behaviour holds, down to 20 K, where translational tunnelling is dominant. The refinements yield accurate atomic coordinates, thermal parameters and site occupancy factors for all atoms, and show that conversion of the B dimer configuration to the lower energy A dimer configuration in the range 175 to 50 K is primarily enthalpy driven, in good agreement with spectroscopic data. Site occupancies for the hydrogen-bonded hydrogen atom at 20 K do not fit the trend in occupancies observed at the four higher temperatures, and a further series of structure refinements at temperatures below 50 K is planned to investigate this.
TL;DR: The surface structure of the cleaved (1014) face of calcite single crystal in an aqueous environment has been studied using atomic force microscopy as discussed by the authors, which is interpreted in terms of the 1 × 1 symmetry from the top-lying surface oxygen atoms.
TL;DR: In this paper, fine particles of barium titanate single crystal with an average particle size of about 66 nm were prepared by a hydrothermal method, and the crystal structure was assigned to cubic with an expanded lattice using a Rietveld method.
Abstract: Fine particles of barium titanate single crystal with an average particle size of about 66 nm were prepared by a hydrothermal method. In the as‐prepared sample, there was a large amount of the hydroxyl group and barium vacancy, and its crystal structure was assigned to cubic with an expanded lattice using a Rietveld method. The hydroxyl group desorbed with increasing calcination temperature, especially desorbing remarkably in the range from 200 to 300 °C. Above 700 °C, there was no hydroxyl group in the particle, and the crystal structure of the sample treated at 800 °C was assigned to tetragonal with tetragonality of 1.001 using a Rietveld method. The state of the lattice vibration was measured by an infrared reflection method, and analyzed using a nonlinear least‐squares method with a four‐parameter semiquantum model. As the result, the crystal structure of the as‐prepared sample estimated using Fourier transform infrared and Raman was assigned to tetragonal. On the O6 octahedra deformation mode, the re...
TL;DR: The magnetic properties of the NiFe2O4 films are strongly affected by the structural changes; unannealed films are not magnetically saturated even in an applied field of 55 kOe, while the annealed films have properties comparable to those of bulk, single crystal NiFe 2O4.
Abstract: Thin films of NiFe2O4 were deposited on SrTiO3 (001) and Y0.15Zr0.85O2 (yttria-stabilized zirconia) (001) and (011) substrates by 90°-off-axis sputtering. Ion channeling, x-ray diffraction, and transmission electron microscopy studies reveal that films grown at 600 °C consist of ∼300 A diameter grains separated by thin regions of highly defective or amorphous material. The development of this microstructure is attributed to the presence of rotated or displaced crystallographic domains and is comparable to that observed in other materials grown on mismatched substrates (e.g., GaAs/Si or Ba2YCu3O7/MgO). Postdeposition annealing at 1000 °C yields films that are essentially single crystal. The magnetic properties of the films are strongly affected by the structural changes; unannealed films are not magnetically saturated even in an applied field of 55 kOe, while the annealed films have properties comparable to those of bulk, single crystal NiFe2O4. Homoepitaxial films grown at 400 °C also are essentially single crystal.
TL;DR: In this paper, N,N'-dineopentyl-1,2-phenylenediaminodichlorosilane Si[{N(CH2tBu)}2C6H3-1-2-R-4] [R = H (3) or Me (4)] were obtained from reaction with K in refluxing THF.