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Showing papers on "Single crystal published in 1985"


Journal ArticleDOI
TL;DR: In this article, a review of the available experimental and theoretical understanding on the structure and electronic properties of grain boundaries in semiconducting materials is presented, where high-resolution electron microscope images of interfaces are interpreted within the framework of the structural unit model of grain boundary, and the electronic properties are discussed with relation to the popular symmetric Schottky barrier model for charge trapping and potential barrier formation.
Abstract: This review presents the available experimental and theoretical understanding on the structure and electronic properties of grain boundaries in semiconducting materials. High-resolution electron microscope images of interfaces are interpreted within the framework of the structural unit model of grain boundaries, and the electronic properties of the grain boundaries discussed with relation to the popular symmetric Schottky barrier model for charge trapping and potential barrier formation. It is shown that these models give some limited understanding of the physical processes that occur at grain boundaries in elemental semiconductors, but that in compound semiconducting materials the effects of non-stoichiometry at the boundary regions must also be considered. Segregation of impurity and dopant species to the boundaries can have significant influence on their electrical properties, and the question of what structural or chemical features are responsible for the observed properties is posed. Diffusion at semiconductor grain boundaries is also discussed, and finally the electrical properties of zinc oxide varistor material are presented in the light of the models of carrier interactions with grain boundaries.

431 citations


Journal ArticleDOI
TL;DR: The crystal structure of the martensite in Ti-49.2 at.%Ni alloy was analyzed by the single crystal X-ray diffraction method in a straightforward manner.

364 citations


Journal ArticleDOI
TL;DR: Amorphous Si and Ge layers, produced by noble gas (Ar or Xe) implantation of single crystal substrates, have been crystallized in a differential scanning calorimeter (DSC) as discussed by the authors.
Abstract: Amorphous Si and Ge layers, produced by noble gas (Ar or Xe) implantation of single crystal substrates, have been crystallized in a differential scanning calorimeter (DSC). The MeV implantation energies resulted in amorphous layers of micron thickness whose areal densities were determined using the Rutherford backscattering and channeling of 1‐MeV protons. These techniques allow determination of the amorphous‐crystal interface velocity (which is proportional to the rate of heat evolution ΔHac) and the total enthalpy of crystallization ΔHac. Amorphous Ge was found to relax continuously to an amorphous state of lower free energy, with a total enthalpy of relaxation of 6.0 kJ/mol before the onset of rapid crystallization. The interface velocity for crystallization on (100) substrates, was found to have an Arrhenius form with an activation energy of 2.17 eV. The value of ΔHac was found to be 11.6±0.7 kJ/mol, the same as for samples prepared by deposition. For Si, ΔHac was determined to be 11.9±0.7 kJ/mol wit...

364 citations


Journal ArticleDOI
TL;DR: In this article, the room temperature structure of BaFe12O19 hexagonal ferrite has been refined from X-ray single crystal data, and three different models are considered for the structural and dynamic characteristics of the bipyramidal Fe ions: (1) a nondisordered configuration, (2) a static disorder between two adjacent pseudotetrahedral sites, and (3) a dynamical disorder between these sites.

213 citations



Journal ArticleDOI
TL;DR: In this paper, the tracer diffusion of the impurity ions, 46 Sc, 51 Cr, 54 Mn, 59 Fe, 60 Co, 63 Ni and 95 Zr, in rutile single crystals was measured as functions of crystal orientation, temperature, oxygen partial pressure and Al impurity content.

157 citations


Journal ArticleDOI
TL;DR: In this article, the rate of inrramolecular electron transfer in mixed-valence biferrocenium triiodide, 1, and four mixedvalence dialkyl-substituted biferricium triide salts is controlled by dynamics in the solid state.
Abstract: Data are presented to indicate that the rate of inrramolecular electron transfer in mixed-valence biferrocenium triiodide, 1, and four mixed-valence dialkyl-substituted biferrocenium triiodide salts is controlled by dynamics in the solid state. The X-ray structure of 1 at 296 K has been determined: Pi, a = 7.5779 (20) A, b = 8.4742 (14) A, c = 9.5577 (21) A, LY = 112.619 (14)', p = 104.646 (20)O, and y = 94.610 (19)'; Z = 1, Dcalcd = 2.32 g ~m-~, R,, = 0.042 for 2185 observed (F, 2 2.5u(F0)) reflections. The mixed-valence biferroceqium cation assumes a trans conformation where the Fe(q5-C5Hs) moieties are on opposite sides of a planar fulvenide ligand. The two rings bonded to each Fe atom are eclipsed. Both the cation and the anion sit on centers of symmetry in 1. The 300 K Mossbauer spectrum of 1, however, shows equal-area Fe" and Fe"' doublets. It is probable that a well-formed single crystal has Mossbauer-delocalized molecules, whereas a microcrystalline sample tends to have localized molecules. Several different samples of 1 were examined with the Mossbauer technique to find that at 300 K the ratio of delocalized to localized molecules can vary from -0 to - 1 depending on the history of the sample. At temperatures above 300 K the Mossbauer spectrum of compound 1 does change to eventually become a single average-valence doublet at -357 K. Differential scanning calorimetry curves in the range of -303 to -363 K were run for several samples of 1. For samples that show 300 K Mossbauer spectra comprised essentially of a localized signal, a relatively sharp endothermic peak is seen at -335 K. Samples of 1 which show appreciable amounts of a signal for the delocalized species at 300 K give a broad DSC peak shifted to lower temperature than -335 K. In one case the peak was apparently even so broad as to be not detectable. The X-ray structure of 1',6'-di-n-butylbiferrocenium triiodide, 7, has been determined at 150, 298, and 363 K. At all three temperatures 7 crystallizes in the P2,/c space group. At 150 K the structure of 7 is characterized as a = 10.0201 (8) A, b = 13.5203 (9) A, c = 21.6080 (23) A, and p = 106.015 (8)'; Z = 4, RF = 0.042, and RwF = 0.052 for 5145 observed (IqZ > 2.0~14~) reflections. The mixed-valence di-n-butylbiferrocenium cation assumes a trans conformation with a planar fulvenide ligand. The two halves of the cation are inequivalent at 150 K by virtue of the positioning of the 13- anion and differences in the configuration of the two butyl groups. Analysis of the X-ray diffraction results for 7 at 298 and 363 K shows that at these higher temperatures positional disorder sets in for both the cation and the anion. One of the butyl groups develops pronounced positional disorder at the higher temperatures. It is suggested that this butyl group is dynamically disordered at the higher temperatures. This is supported by the observation that the c axis of a crystal of 7 expands appreciably from 150 to 363 K. Both 7 and 1',6'-dibenzylbiferrocenium triiodide, 8, exhibit an interesting phenomenon. Microcrystalline samples of 7 and 8 give 300 K Mossbauer spectra which show appreciable intensity signals from valence-localized species, whereas recrystallized samples give 300 K Mossbauer spectra exhibiting only a signal for a delocalized species. At temperatures below -200 K there are two doublets for crystalline 7 and 8. The two doublets became a single doublet at -275 and -260 K, respectively, for 7 and 8 as the temperature is increased. The above results indicate that these mixed-valence compounds are undergoing phase transitions. It is suggested that the observed temperature dependence of the Mossbauer spectra for the dialkyl-substituted complexes 7 and 8 and the analogous ethyl- and propyl-substituted complexes results from I< anions undergoing a transformation from a static situation which tends to localize the charge in the mixed-valence cation to a dynamic situation where on the average the environment about each half of a mixed-valence cation is identical. ~~~~~~~ ~

143 citations


Journal ArticleDOI
TL;DR: The reduction of single crystal NiO(100) under hydrogen has been followed by AES, XPS and LEED for the pressure range of 1.0 × 10 −7 to 1.3 × 10−6 Torr and for substrate temperatures of 150-350°C as mentioned in this paper.

141 citations


Journal ArticleDOI
TL;DR: Physical, optical and electrical properties of thin films of chemically deposited CdS are reported in this paper, where the resistivity of as-deposited films was ca. 109 ω cm and was lowered by both vacuum and hydrogen annealing.

138 citations


Journal ArticleDOI
TL;DR: The first all-silicon integrated-optical components for 1.3/1.6 µm have been demonstrated in this paper, where an optical power divider with end-fire coupling was constructed from intersecting channel waveguides.
Abstract: The first all-silicon integrated-optical components for 1.3/1.6 μm have been demonstrated. An optical power divider with end-fire coupling was constructed from intersecting channel waveguides. Guides were fabricated by plasma-etching of an intrinsic Si layer grown epitaxially on a heavily doped Si substrate (n on n + or p on p + ). Active components are proposed.

135 citations



Journal ArticleDOI
TL;DR: The influence of composition on the microstructure of single crystal nickel-base superalloys was investigated in this article, where Co was replaced by Ni, and Ta was replaced with either Ni or W, according to a matrix of compositions based on MAR-M247.
Abstract: The influence of composition on the microstructure of single crystal nickel-base superalloys was investigated. Co was replaced by Ni, and Ta was replaced by either Ni or W, according to a matrix of compositions based on MAR-M247. Substitution of Ni for Co caused an increase inγ′ solvus temperature, an increase inγ-γ′ lattice mismatch, and the precipitation of W-rich phases in the alloys with high refractory metal levels. Substitution of Ni for Ta caused large decreases inγ′ solvus temperature,γ′ volume fraction, andγ-γ′ lattice mismatch, whereas substitution of W for Ta resulted in smaller decreases in these features. For the alloys withγ′ particles that remained coherent, substitution of Ni for Co caused an increase inγ′ coarsening rate. The two alloys with the largest magnitude of lattice mismatch possessedγ′ particles which lost coherency during unstressed aging and exhibited anomalously low coarsening rates. Creep exposure at 1000 °C resulted in the formation ofγ′ lamellae oriented perpendicular to the applied stress axis in all alloys.

Journal ArticleDOI
TL;DR: In this article, the reactivity of the edge planes of MoS2 has been studied on single crystals and it has been shown that Co incorporated at low levels into single crystals tends to surface segregate at MoS 2 edge planes.

Journal ArticleDOI
01 May 1985-Zeolites
TL;DR: In this paper, single crystals of ZSM-5 of up to 280 μm were synthesized and an X-ray structure analysis was performed on one such crystal, and precise atomic positions and an R -factor of 0.0965 were measured.

Journal ArticleDOI
TL;DR: In this article, single crystals of MoSi2 with very high resistivity ratios have been grown using a Crochralski technique and a modified Hukin-type crucible.

Journal ArticleDOI
TL;DR: In this article, the infrared spectrum was used to study the vibration of CO adsorbed on small, silica-supported platinum particles, and three bands can be detected on each of the different samples.

Journal ArticleDOI
TL;DR: In this paper, a model is proposed to elucidate the variation of transport properties of doped SnO/sub 2/ as a function of film thickness, and the conductivities of the films can be computed using this model and taking a single value for the electron mobility of 19 cm/sup 2/ (V-s)/sup -1/ for all film thickness and a total donor concentration of 2 x 10/sup 20/ cm /sup -3/.
Abstract: Tin oxide films were deposited by chemical vapor deposition on borosilicate and fused silica substrates using dibutyltin diacetate (DBTD) as tin feedstock and SbC/sub 5/ or CC/sub 3/-CF/sub 3/ as dopants. The film growth rate was measured as a function of dopant/DBTD ratio, temperature, and film thickness. Scanning electron microscopy and x-ray diffraction spectra of the films were used to determine the grain sizes and the preferential orientations of the crystallites in the film as a function of film thickness. Optical and electrical properties were measured. A model is proposed to elucidate the variation of transport properties of doped SnO/sub 2/ as a function of film thickness. It could b shown with this model that the thickness dependence of the conductivity of doped SnO/sub 2/:Sb and SnO/sub 2/:F films could be analyzed in terms of carrier concentration taking into consideration deep-level compensation. The number of carriers is decreased by electron trapping at Sb(III) or Sn(II) surface states when antimony or fluorine are used as dopant, respectively. The model based on results of the literature related to a single crystal with (110) orientation is extended in this work to other crystallite orientations. The present analysis indicates that deep levels appear onlymore » on the grain boundary surfaces with (110), (211), and (301) orientations, and not on the (200) and (400) ones. The concentration of free carriers can be calculated on the basis of x-ray diffraction spectra indicating an estimate of the relative fraction of the crystallites with each orientation as a function of the film thickness. The conductivities of the films can be computed using this model and taking a single value for the electron mobility of 19 cm/sup 2/ (V-s)/sup -1/ for all film thickness and a total donor concentration of 2 x 10/sup 20/ cm/sup -3/. All the obtained experimental data can be accounted for exclusively on the basis of film-thickness dependent carrier concentration.« less

Journal ArticleDOI
TL;DR: In this article, a structural mechanism for the pyroelectric effect is discussed in terms of large oxygen displacements, which occurs at 160°C, perhaps caused by the cancellation of primary and secondary effects.
Abstract: Crystal structure parameters have been refined from single crystal x-ray intensity data collected on Ba2TiSi2O8 at 24 and 300°C. Anisotropic refinements in space group P4bm yielded residuals of 0.035 and 0.042 at 24 and 300°C, respectively. Pyroelectric measurements give a room temperature pyroelcctric coefficient of + 10 μC m -2 K -1. A structural mechanism for the pyroelectric effect is discussed in terms of large oxygen displacements. A sign reversal in the pyroeleetric coefficient occurs at 160°C, perhaps caused by the cancellation of primary and secondary effects.

Patent
08 Oct 1985
TL;DR: Improved bipolar transistors with minimum base collector and collector-substrate junction area are formed by using multiple polycrystalline (e.g. doped poly silicon) layers to make lateral contact to a pillar shaped single crystal device region as discussed by the authors.
Abstract: Improved bipolar transistors having minimum base-collector and collector-substrate junction area are formed by using multiple polycrystalline (e.g. doped poly silicon) layers to make lateral contact to a pillar shaped single crystal device region. The lateral poly silicon contacts are isolated from each other and the substrate and extend to the upper surface of the device for external connections. The structure is made by depositing two dielectric-poly layer sandwiches, etching and oxidizing part of the poly silicon layers to provide isolated overlapping poly silicon regions, etching a first hole through both poly silicon regions to the substrate, etching a second hole to the lower poly silicon layer, and filling the first and second holes with single and poly-crystalline silicon, respectfully. A sidewall oxide is formed at the periphery of the top of the single crystal pillar for defining the emitter location without additional masking.

Journal ArticleDOI
TL;DR: In this article, the existence of grain boundary dislocation (GBD) related cusps on the boundary energy vs θ curve at ∑1 and ∑5 was shown.

Journal ArticleDOI
TL;DR: The Scanning Kinetic Spectroscopy (SKS) method as mentioned in this paper uses a calibrated and collimated beam of reactant molecules incident upon a clean single crystal surface in UHV.

Journal ArticleDOI
TL;DR: In this paper, a simple relationship between the c/a ratio and the cationic sublattice ordering was suggested for AGa2X4 compounds, and X-ray structural investigations indicated blende or defect chalcopyrite structures.


Journal ArticleDOI
TL;DR: In this paper, the properties of ternary borides with composition R1+eFe4B4 (R = Ce, Pr, Nd, Sm, Gd, Tb, 0.11(Pr) ≤e≤ 0.15(Tb) are reported).

Journal ArticleDOI
TL;DR: In this article, it was shown that a metal ion is not required for high electrical conductivity, and that the simplest phthalocyanine (Pc)I ion does not require a metal atom for high conductivity.

Journal ArticleDOI
TL;DR: In this article, the lattice parameters of the body-centered cells used in the present refinements were: K0.30MoO3,a = 16.2311(7),b = 7.361(3),c = 9.8614(4)A˚,β = 94.87(5)o.

Journal ArticleDOI
TL;DR: In this paper, the dielectric, piezoelectric and pyroelectric properties of fresnoite (Ba2TiSi2Os) single crystal and polar glass-ceramics were studied in the temperature range - 150 to 200°C.
Abstract: The dielectric, piezoelectric and pyroelectric properties of fresnoite (Ba2TiSi2Os) single crystal and polar glass-ceramics were studied in the temperature range - 150 to 200°C. The sign of pyroelectric coefficient is positive at room temperature and becomes negative at 190°C. The dielectric constant, pyroelectric coefficient and planar coupling coefficient show a maximum value at 160°C and the frequency constant shows a minimum at the same temperature. The probable reasons for the anomaly in these properties are discussed.

Journal ArticleDOI
TL;DR: In this article, a model of the layer system Si/SiOx/SiO2, which is valid for a broad range of silicon oxide layers, was presented, and the results were combined to give a model for a wide range of Si oxide layers.

Journal ArticleDOI
TL;DR: AES, ELS, LEED, AES and XPS investigations of the surface segregation of tin dissolved in a Fe-4wt%Sn alloy were performed in ultra-high vacuum at elevated temperatures as discussed by the authors.

Journal ArticleDOI
TL;DR: In this article, it was shown that ribbon-like defects are the coesite phase which forms at prolonged anneals of the same material at higher temperatures of 630-650°C.
Abstract: Prolonged annealing of Czochralski silicon at 485°C leads to the formation of a number of defects which is accompanied by a reduction in the concentration of oxygen interstitials in the matrix. High‐resolution electron microscopy has been used to investigate the structure of these defects which are basically of three types: (1) ribbonlike, (2) looplike defects which result in local lattice strains and hence are also visible in conventional transmission electron microscopy, and (3) dark regions visible in high‐resolution micrographs with no lattice strains. Based on image characteristics and a comparison of the reduction in interstitial oxygen, from infrared spectroscopy, with the sizes of the ribbons, estimated from high‐resolution micrographs, it is proposed that the ribbonlike defects are, in fact, the coesite phase which forms at prolonged anneals of the same material at the higher temperatures of 630–650°C. Using a simple model for the diffusion of oxygen to ribbons, the diffusivity of oxygen in silic...