Showing papers on "Lattice constant published in 1992"
TL;DR: In a comprehensive study, the modified embedded-atom method is extended to a variety of cubic materials and impurities, including metals, semiconductors, and diatomic gases, all of which exhibit different types of bonding.
Abstract: In a comprehensive study, the modified embedded-atom method is extended to a variety of cubic materials and impurities. In this extension, all functions are analytic and computationally simple. The basic equations of the method are developed and applied to 26 elements: ten fcc, ten bcc, three diamond cubic, and three gaseous materials. The materials modeled include metals, semiconductors, and diatomic gases, all of which exhibit different types of bonding. Properties of these materials, including equation of state, elastic moduli, structural energies and lattice constants, simple defects, and surfaces, are calculated. The formalism for applying the method to combinations of these elements is developed and applied to the calculation of dilute heats of solution. In all cases, comparison is made to experiment or higher-level calculations when possible.
1,683 citations
TL;DR: In this article, high precision voltage measurements and in situ x-ray diffraction indicate a sequence of three distinct phase transitions as varies from 1 to 0.4, two of which are situated slightly above and below and are caused by an order/disorder transition of the lithium ions.
Abstract: Electrochemical properties of are studied as Li is deintercalated from . High precision voltage measurements and in situ x‐ray diffraction indicate a sequence of three distinct phase transitions as varies from 1 to 0.4. Two of the transitions are situated slightly above and below and are caused by an order/disorder transition of the lithium ions. The order/disorder transition is studied as a function of temperature allowing the determination of an order/disorder phase diagram. In situ x‐ray diffraction measurements facilitate a direct observation of the effects of deintercalation on the host lattice crystal structure. The other phase transition is shown to be first order (coexisting phases are observed for ) involving a significant expansion of the parameter of the hexagonal unit cell. We report the variation of the lattice constants of with and show that the phase transition to the lithium ordered phase near is accompanied by a lattice distortion to a monoclinic unit cell with , , and . Finally we report an overall phase diagram for and .
1,529 citations
TL;DR: In this article, a large lattice constant on Si has been obtained by growing compositionally graded GexSi1−x on Si, and these buffer layers have been characterized with electron-beam-induced current, transmission electron microscopy and x-ray diffraction to determine the extent of relaxation, threading dislocation density, the surface morphology, and the optical properties.
Abstract: To obtain a large lattice constant on Si, we have grown compositionally graded GexSi1−x on Si. These buffer layers have been characterized with electron‐beam‐induced current, transmission electron microscopy, scanning electron microscopy, x‐ray diffraction, and photoluminescence to determine the extent of relaxation, the threading dislocation density, the surface morphology, and the optical properties. We have observed that it is possible to obtain completely relaxed GexSi1−x layers with 0.1
549 citations
TL;DR: In this article, the authors reported the isolation of an alkaline-earth-deficient infinite-layer phase, (Ca1-xSrx)1-yCuO2 (y~Ol), with Tc up to 110 K.
Abstract: THE 'infinite-layer' parent structure1 of the copper oxide superconductors (Fig 1) is the simplest structure containing the CuO2 sheets that are apparently essential to high-transition-temperature (high-Tc) superconductivity At ambient pressure only Ca1-x SrxCuO2 with x≈Ol can be stabilized in this structure1,2but at high pressures and temperatures compounds ranging from Ba1/3Sr2/3CuO2 to Ca2/3Sr1/3CuO2 through SrCuO2 can be synthesized3 We have previously reported superconductivity with Tc = 40–100 K in the Ba–Sr–Cu–O system4,5 but have not until now been able to isolate a superconducting phase Here we report the isolation of an alkaline-earth-deficient infinite-layer phase, (Ca1-xSrx)1-yCuO2 (y~Ol), with Tc up to 110 K In contrast to Sr1-xRxCuO2 (with R a rare-earth element and Tc⩽43 K), which from the composition dependence of the lattice constants is thought to be an n-type superconductor6,7 our data suggest that the present superconductor is of p-type, with the carriers arising from calcium and strontium vacancies High-resolution electron micrographs reveal defect layers, which we suggest are where the calcium and strontium vacancies are concentrated
344 citations
TL;DR: In this paper, the synthesis of pseudomorphic Si1−xGex and Si 1−x−yGexCy alloy layers on a silicon substrate by molecular beam epitaxy using solid sources and the controlled strain compensation that results from the introduction of the ternary system was discussed.
Abstract: Strain compensation is an important aspect of heterostructure engineering. In this letter, we discuss the synthesis of pseudomorphic Si1−yCy and Si1−x−yGexCy alloy layers on a silicon (100) substrate by molecular beam epitaxy using solid sources and the controlled strain compensation that results from the introduction of the ternary system. The introduction of C into substitutional sites in the crystal lattice is kinetically stabilized by low‐temperature growth conditions (400–550 °C) against thermodynamically favored silicon‐carbide phases. The lattice constant in Ge is about 4% larger than in Si, whereas in diamond it is 52% smaller. Consequently, the compressive strain caused by 10.8% Ge in a pseudomorphic Si1−xGex alloy can be compensated by adding about 1% carbon into substitutional lattice sites of the film assuming Vegard’s law of linear change of the lattice constant in the alloy as a function of the composition. Using x‐ray diffraction, we observe a partial strain compensation in Si0.75−yGe0.25Cy...
277 citations
TL;DR: In this article, the relaxation process of the thermal strain in a GaN film due to the thermal expansion coefficient difference in the GaN(0001)/α-Al2O3(0001) heterostructure is studied by varying the film thickness of GaN in a wide range from 1 to 1200 µm.
Abstract: The relaxation process of the thermal strain in a GaN film due to the thermal expansion coefficient difference in the GaN(0001)/α-Al2O3(0001) heterostructure is studied by varying the film thickness of GaN in a wide range from 1 to 1200 µm. The lattice constant c has a large value of 5.191 A at a film thickness less than a few microns, while it decreases to about 150 µm, and becomes constant above 150 µm, indicating that the strain is almost completely relaxed. The intrinsic lattice constants of wurtzite GaN free from the strain, a0 and c0, are determined to be 3.1892±0.0009 and 5.1850±0.0005 A, respectively.
232 citations
NEC1
TL;DR: In this article, a monotonic relationship is observed between Tc and lattice constant a0 for these face-centred cubic M3C0 compounds, all of which have a0 values larger than that of pure C60.
Abstract: THE discovery1 of superconductivity, with a transition temperature Tc of 18 K, in potassium-doped C60 was followed by the synthesis of other superconducting M3C60 phases: Rb3C60 (Tc = 28K and 30 K; refs 2, 3), CsRb2C60 (Tc = 31K; ref. 4) and Cs2RbC60 (Tc = 33 K; ref. 4). A monotonic relationship is observed5 between Tc and lattice constant a0 for these face-centred cubic M3C0 compounds, all of which have a0 values larger than that of pure C60. Here we study this relationship over a wider range using mixed alkali compounds incorporating sodium (Na2MC60, where M is K, Rb or Cs) and lithium (Li2CsC60). The Na2MC60 compounds have face-centred cubic structures and are superconducting, with Tc = 12 K (M = Cs), 2.5 K (M = Rb) and 2.5 K (M = K); these Tcs are lower than those predicted on the basis of high-pressure studies6–8. This departure from the previous relationship between Tc and a0 for lattice parameters smaller than that of pristine C60 may provide new insights into what controls superconductivity in these materials.
212 citations
TL;DR: In this article, a spincoating technique was used to obtain thin Pb(ZrxTi1−x)O3 films with zirconium concentrations ranging from x=0.2 to 0.75.
Abstract: The deposition of thin Pb(ZrxTi1−x)O3 films by sol‐gel and by metallo‐organic decomposition (MOD) processes has been studied. Powders obtained from different precursor solutions were analyzed with respect to their decomposition and crystallization. Using a spin‐coating technique, Pb(ZrxTi1−x)O3 films with zirconium concentrations ranging from x=0.2 to 0.75 have been deposited on Pt‐electroded Si wafers. The lattice constants of the perovskite films and their dielectric and ferroelectric properties (permittivity, remanent polarization, coercive field strength) have been measured as a function of the zirconium concentration. The results are compared to the data obtained on bulk ceramics. For Pb(ZrxTi1−x)O3 films with a composition located at the morphotropic phase boundary (x≊0.53) the influence of the processing and the lead excess of the starting solutions on the film properties was examined. First measurements on the resistance degradation of thin Pb(Zr0.53Ti47)O3 films deposited by the MOD process are r...
199 citations
Journal Article•
TL;DR: In this article, MgFe204 spinel was synthesized in equilibrium with excess MgO using a flux method and the time needed to reach equilibrium at low temperatures (450650 0C) was assessed by monitoring the change of lattice parameter with time.
Abstract: Magnesioferrite (MgFe204 spinel) was synthesized in equilibrium with excess MgO using a flux method. Chemical analysis shows that the MgFe204 is stoichiometric, within analytical uncertainty. Samples were annealed at intervals of 50 °C between 450 and 1250 °C and quenched in H20. The time needed to reach equilibrium at low temperatures (450650 0C) was assessed by monitoring the change of lattice parameter (ao) with time. In addition, the changes in ao at 550-650 °C were reversed, using material annealed at 400 °C for 50 d. Some samples were further characterized by measuring their Neel temperatures, using DSC. The cation distributions in the quenched samples were determined using both powder X-ray diffraction and M6ssbauer spectroscopy. To increase the resolution in the latter, the samples were studied in an applied magnetic field of 4.5 T at 12-171 K. The cation distribution changes smoothly with temperature, with the cation inversion parameter (x) decreasing from 0.90 at 450 °C to 0.72 at 1100 0c. The precision with which x can be determined is ::to.004 from XRD and -::to.O! from the M6ssbauer spectroscopy. The two sets of measurements agree well with each other, the mean difference in x being 0.0056 ::t 0.0102. Thermodynamic modeling shows that the cation distribution can be described with a nonlinear enthalpy of disordering model, with aMg-Fe}+ = 26.6 ::t 0.4 and {1= - 21. 7 ::t 0.3 kJ/g-atom. Incorporation of a small excess (nonconfigurational) entropy term into the model gives a slightly better fit, however. The disordering in MgFe204 as a function of temperature is virtually identical to that found in Fe,04 from thermopower measurements. The present results differ to a greater or lesser extent from most of the previous work on MgFe204. This is most likely attributable to differences in stoichiometry. We also present some results on nonstoichiometric "MgFe204," i.e., solutions of MgFe204 and 1'-Fe20" which tend to confirm this hypothesis, at least for some of the earlier studies.
189 citations
TL;DR: Results of an ab initio density-functional study of interlayer binding in graphite obtain good agreement with experimental results for the equilibrium c-axis lattice parameter, exfoliation energy, and uniaxial compressibility.
Abstract: Results of an ab initio density-functional study of interlayer binding in graphite are presented. We obtain good agreement with experimental results for the equilibrium c-axis lattice parameter, exfoliation energy, and uniaxial compressibility for this highly anisotropic material. We also present the calculated band structure of graphite
183 citations
TL;DR: In this paper, a metastable zinc-blende-structure β-AlN was synthesized by the solid-state reaction between single-crystal Al(001) and TiN(001), grown on MgO(001).
Abstract: Epitaxial metastable zinc‐blende‐structure β‐AlN was synthesized by the solid‐state reaction between single‐crystal Al(001) and TiN(001) layers grown on MgO(001) by ultrahigh vacuum magnetron sputter deposition. At an annealing temperature Ta=600 °C, the interaction proceeded according to the following overall reaction: 4Al+TiN→Al3Ti+AlN, in which β‐AlN was formed pseudomorphically between cubic TiN and tetragonal Al3Ti layers. The lattice constant of β‐AlN was found to be 0.438 nm, which corresponds to a 3.3% lattice mismatch with the underlying TiN layer.
TL;DR: A universal first-order relation between Tc and the lattice parameter a is established over a broad range, between 13.9 and 14.5 angstroms, which appears to rule out the participation of intercalate-fullerene optic modes in the pairing interaction.
Abstract: X-ray diffraction and diamond anvil techniques were used to measure the isothermal compressibility of K 3 C 60 and Rb 3 C 60 , the superconducting, binary alkali-metal intercalation compounds of solid buckminsterfullerene. These results, combined with the pressure dependence of the superconducting onset temperature T c measured by other groups, establish a universal first-order relation between T c and the lattice parameter a over a broad range, between 13.9 and 14.5 angstroms. A small secondorder intercalate-specific effect was observed that appears to rule out the participation of intercalate-fullerene optic modes in the pairing interaction.
TL;DR: In this paper, it was shown that any force model using short-range pair-functional interactions can only have three independent h.c.p. elastic constants, and a new parametrization of a Finnis-Sinclair-type many-body potential for titanium was presented using these relations.
Abstract: It is shown that any force model using short-range pair-functional interactions can only have three independent h.c.p. elastic constants. Empirical data show that these elastic properties are nearly realized in a number of materials. A new parametrization of a Finnis-Sinclair-type many-body potential for titanium is presented using these relations. Particular care is taken to describe the anisotropy of the shear constants and the deviation of the c/a lattice parameter ratio from ideal, while maintaining smooth monotonic functions. Energies, stresses and reconstruction modes of various low-index surfaces are calculated and general rules for surface stability are proposed. Various stacking faults on the basal and pyramidal plane are investigated.
TL;DR: In this paper, the intercalation of fulleride with barium, in which a pure body-centred cubic phase with a lattice constant of 11.171 A is realized near a stoichiometry of Ba6C60, suggesting that the mechanism of superconductivity is related to an intrinsic property of the C60 molecules, rather than the external coordination number.
Abstract: INTERCALATING solid C60 with dopant atoms yields materials with a remarkable range of properties1. Alkali metal atoms, for example, readily form charge-transfer compounds2,3, AxC60 (where A is an alkali metal), which can be metallic, superconducting or insulating depending on the dopant concentration4–9. In all cases, the superconducting phase has a face-centred cubic (f.c.c.) structure and stoichiometry A3C60, which suggests a common mechanism for superconductivity dependent, at least in part, on the external coordination number of the C60 molecules. More recently, it has been shown10 that the alkaline earth metal calcium can also be intercalated with fulleride to form a superconducting phase, again with a f.c.c.-derived structure, near a Ca:C60 ratio of 5:1. Here we report the intercalation of fulleride with barium, in which a pure body-centred cubic phase with a lattice constant of 11.171 A is realized near a stoichiometry of Ba6C60. This phase is also superconducting (with a transition temperature of 7 K), suggesting that the mechanism of superconductivity is related to an intrinsic property of the C60 molecules, rather than the external coordination number.
TL;DR: In this article, an algorithm is described which automatically adjusts values of lattice parameters or high voltage for best fit to the high-order Laue zone (HOLZ) lines in experimental convergent-beam electron diffraction (CBED) patterns for both cubic and non-cubic cell.
TL;DR: The dependence of the lattice parameter of γ-aluminium oxynitride (Alon) on its composition was investigated in this article, where it was found that the width of the homogeneity of Alon varies with temperature.
Abstract: The dependence of the lattice parameter of γ-aluminium oxynitride (Alon) on its composition was investigated. It was found that the width of the homogeneity of Alon varies with temperature: at 1850°C Alon is the stable phase between 66 mol% Al2O3 (lattice parameter 0·7953 nm) and 81 mol% Al2O3 (lattice parameter 0·7932 nm). This region becomes smaller with lower temperatures. Below 1640 ± 10°C Alon is not stable.
TL;DR: X-ray and neutron-diffraction measurements have been used to study the evolution of the lattice parameter of solid C{sub 60} through the orientational-ordering transition and observe phase coexistence over a 5-K range, but little if any hysteresis.
Abstract: X-ray and neutron-diffraction measurements have been used to study the evolution of the lattice parameter of solid C{sub 60} through the orientational-ordering transition. The lattice parameter jumps by +0.044{plus minus}0.004 A on heating, indicating a strongly first-order transition. The average isobaric volume thermal-expansion coefficient both above and below the transition is 6.2{plus minus}0.2{times}10{sup {minus}5} K{sup {minus}1}. We observe phase coexistence over a 5-K range, but little if any hysteresis.
TL;DR: In this paper, the lattice constants of boron carbides are determined by powder X-ray diffraction for samples with compositions between about 7.7 and 20.5 at.% carbon.
Abstract: In this paper, the lattice constants of boron carbides are determined by powder X-ray diffraction for samples with compositions between about 7.7 and 20.5 at.% carbon. The boundaries of the single-phase region are at about 9 at.% carbon and near, but likely somewhat less than 20 at.% carbon. The composition dependence of the lattice constants thus established provides a method of assessing the carbon concentration of unknown materials. In particular, assignment of the approximate composition of single crystals used in previous studies allows for a systematic examination of changes in interatomic separation as a function of composition. These changes are discussed in terms of a structural model of the boron carbide solid solution.
TL;DR: Sr 2 CuO 2 (CO 3 ) was prepared at 1273 K and 0.01 MPa CO 2 partial pressure in a flowing gas of O 2 CO 2 using a mixture of SrCO 3 and CuO powders as a starting material as mentioned in this paper.
Abstract: Sr 2 CuO 2 (CO 3 ) was prepared at 1273 K and 0.01 MPa CO 2 partial pressure in a flowing gas of O 2 CO 2 using a mixture of SrCO 3 and CuO powders as a starting material. The compound has a tetragonal structure with lattice constants a = 7.8045(1), and c = 14.993(1) A , and its space group is 14. The formula per unit cell is 8 Sr 2 CuO 2 (CO 3 ), and measured and calculated densities are D m = 4.71 g/cm 3 , and D x = 4.81 g/cm 3 , respectively. The crystal structure was refined by Rietveld analysis on X-ray powder diffraction and neutron powder diffraction data. The final residuals ( R F ) were 4.31 and 4.27% for the X-ray and neutron data, respectively. The structure consists of deformed [CuO 6 ] octahedrons and layers of ordered triangular CO 3 groups. Sr atoms having eight near oxygen neighbors are between the [CuO 6 ] octahedrons and the CO 3 layers.
TL;DR: In this paper, the refined spin-pairing energy theory (RSPET) has been improved in order to understand quantitatively the tetrad or double-double effects recognized in the Ln3+ ionic radii.
Abstract: The refined spin-pairing energy theory (RSPET) has been improved in order to understand quantitatively the tetrad or double-double effects recognized in the Ln3+ ionic radii. Since the ionic radii have been determined from the lattice constants and structural parameters of LnO1.5 and LnF3, the lattice energies of the compounds and the enthalpy difference of ΔHfo(LnF3)-ΔHfo(LnO1.5) have been examined by the improved RSPET. The RSPET parameters for the lowest levels of 4fq electronic configurations strongly depend upon the effective nuclear charge (Z*). Such effects due to Z* have been taken into account. This made it possible to separate the variations in the lattice energies and the enthalpy difference across the Ln3+ series into the following two parts: (1) the large variation as a smooth function of q (the lanthanide contraction trend), and (2) the small zig-zag variation referred to the tetrad or double-double effect. The lattice energy of LnO1.5 and ΔHfo(LnF3) − ΔHfo(LnO1.5) exhibit upward concave tetrad curves in their plots against q of Ln3+. The tetrad effect in the lattice energy of LnF3 is less conspicuous. This means that the Racah parameters for Ln3+ decrease very slightly in going from the gaseous free Ln3+ to LnF3, and then decrease greatly to LnO1.5, in accordance with the nephelauxetic series. The differences in Racah parameters between LnF3 and LnO1.5 have been estimated from ΔHfo(LnF3) − ΔHfo(LnO1.5) by means of an inversion technique based on the improved RSPET. The RSPET results for the thermochemical data are consistent with the careful spectroscopic determinations of Racah parameters for NdF3 and NdO1.5. Both the tetrad effect and the smooth lanthanide contraction seen in the Ln3+ ionic radii can be interpreted in terms of the quantum mechanical energetics of 4f electrons.
TL;DR: The crystal structures of two ternary, chalcopyrite-structured semiconductors, CuInSe2 and CuInTe2, have been determined from single crystal X-ray diffraction data as mentioned in this paper.
TL;DR: In this paper, the authors performed total energy calculations by the scalar-relativistic augmented plane wave method in the local density and muffin-tin approximations for all 3D, 4d, and 5d transition metals in the fcc and bcc structures.
Abstract: We performed total-energy calculations by the scalar-relativistic augmented-plane-wave method in the local-density and muffin-tin approximations for all 3d, 4d, and 5d transition metals in the fcc and bcc structures. These calculations predict the correct equilibrium structure and give good agreement with experiment and other calculations for lattice constants and bulk moduli.
TL;DR: In this article, X-ray diffraction indicated a widening of the vertical lattice parameter and a simultaneous increase of the arsenic content at low growth temperature, and the epitaxial layers were single-crystalline down to Ts=125°C.
Abstract: Undoped Ga0.47In0.53As layers were grown by molecular beam epitaxy lattice matched to InP at substrate temperatures, Ts, in the range from 100 to 600 °C. X‐ray diffraction indicated a widening of the vertical lattice parameter and a simultaneous increase of the arsenic content at low growth temperature. The epitaxial layers were single‐crystalline down to Ts=125 °C. The room‐temperature residual carrier concentrations and the related mobilities for layers grown below 350 °C are strongly affected by Ts, whereas at 77 K an influence of Ts on these parameters is already visible at 450 °C. At the very low growth temperatures the epitaxial layers show highly conductive behavior attributed to defect induced ionized deep centers.
TL;DR: The crystal structure of a new compound, (C0.4Cu0.6)Sr2(Y0.86Sr0.14)Cu2O7, is derived from the structure of YBa2Cu3O7.
Abstract: The crystal structure of a new compound, (C0.4Cu0.6)Sr2(Y0.86Sr0.14)Cu2O7, is derived from the structure of YBa2Cu3O7. Forty percent of CuO chains in the YBa2Cu3O7 structure are replaced by CO3 groups. This new compound has a superstructure along the a-axis and the c-axis. Diffuse superlattice reflections having periods of a∗/2-a∗/3 and c∗/2 were observed in electron diffraction patterns. Locally ordered distributions of C and Cu atoms were seen high-resolution images taken by transmission electron microscopy with an incident beam parallel to [010]. The basic structure of this superstructure was determined by neutron powder diffraction, assuming orthorhombic symmetry with the space group, Pmmm (lattice constants: a=3.8278(2), b=3.8506(2) and c=11.1854(5) A ).
TL;DR: In this article, the room temperature structure of the ferroelastic and presumably ferroelectric Aurivillius type compound Bi5(Ti3Fe)O15 (Mr = 1484.4, Dx = 8.065 Mg/m3 Z = 4) was refined by X-rays on a weakly twinned crystal prepared in a Bi2O3/B2O-3 flux with TiO2/Fe 2O3 in stoichiometrical proportions.
Abstract: The room temperature structure of the ferroelastic and presumably ferroelectric Aurivillius type compound Bi5(Ti3Fe)O15 (Mr = 1484.4, Dx = 8.065 Mg/m3 Z = 4) was refined by X-rays on a weakly twinned crystal prepared in a Bi2O3/B2O3 flux with TiO2/Fe2O3 in stoichiometrical proportions. The lattice constants were found to be orthorhombic with a = 5.4318(6), b = 41.149(4) and c = 5.4691(12)A. Refinement in space group Fmm2 converged at R(Rw). = 4.6 (4.2%) with 538 averaged reflections. As the crystal showed <5% of twin domains, a supplementary powder refinement was performed to confirm space group Fmm2. The refinement gave confidential values R(Rw) = 3.1 (4.3%) and R Bragg = 7.4%. No superstructure reflections were found. The structure is built up of layers, composed of two slightly and two strongly distorted perovskite units. These layers are separated by oxygen layers. Birefringence, Δn, was restudied at room temperature on a wedge shaped crystal and found to be 0.080 ± 4. When studied as a funct...
TL;DR: In this paper, the Debye-Waller parameter of nanocrystalline Pd was found to be due to increased static displacement of atoms from their equilibrium sites compared with the static displacements in coarse-grained material.
Abstract: Quantitative X-ray diffraction measurements made over a temperature range 16–300K on a Pd sample of 8·3nm median grain size were compared with data acquired from a coarse-grained Pd reference sample. The larger Debye-Waller parameter of nanocrystalline Pd was found to be due to increased static displacements of atoms from their equilibrium sites compared with the static displacements in coarse-grained material. Consistent with this behaviour, the strain distribution determined from the width of intensity peaks was significantly broader in the nanocrystalline sample than in the coarse-grained sample. No grain-size-correlated differences in either thermal vibrational amplitude or lattice parameter were observed. In contradiction to previous reports of greatly increased thermal expansion coefficients in nanocrystalline metals, the change in lattice parameter of Pd from 16 to 300 K was observed to be independent of grain size. The results indicate that some regions of the nanocrystalline sample are i...
TL;DR: In this paper, the authors determined the bandgap energies of diamond semiconductors as a function of temperature and pressure and showed that the decrease in bandgap energy with increasing temperature is caused by the interaction of the free electrons, holes and recombined electron-hole pairs with lattice phonons and linear expansion of the lattice constant.
Abstract: Semiconductor bandgap energies are shown to be equal to the difference between the sum of the standard chemical potentials of free electrons and holes and standard chemical potential of the recombined electron-hole pairs when equilibrium occurs at a given temperature and pressure. The decrease in the bandgap energies of diamond semiconductors with increasing temperature is shown to be caused by the interaction of the free electrons, holes and recombined electron-hole pairs with lattice phonons and linear expansion of the lattice constant. The determined bandgap energies and other intrinsic properties of nondegenerate GaAs are found to be in excellent agreement with experimental data as a function of temperature and pressure. The proposed model is also shown to be useful in determining the effects of temperature and pressure on the intrinsic properties of epilayers and substrate in the metal-semiconductor junctions and heterojunctions.
TL;DR: In this paper, the elastic stiffness constants of various Ni-based intermetallic Ni3X (X = Mn, Fe, Al, Ga, Ge and Si) with L12 structure have been determined at room temperature by the rectangular parallelepiped resonance method.
Abstract: The three elastic stiffness constants of various Ni-based intermetallic Ni3X (X = Mn, Fe, Al, Ga, Ge and Si) with L12 structure have been determined at room temperature by the rectangular parallelepiped resonance method The elastic anisotrophy factor, A, of the compounds is generally large, ranging from 25 to 33 except for Ni3Ge (A = 171) The large anisotropy is believed to be responsible at least partly for the positive temperature dependence of the flow stress observed for these compounds The elastic constants exhibit some correlation with the lattice constants The minor element, X, can be regarded as exerting “chemical pressure” which causes the expansion of the Ni lattice, thus resulting in the decrease of the elastic constant
TL;DR: In this article, field ion-scanning tunneling microscopy was employed to study the monolayer and multilayer adsorption behaviors of the C60 fullerene on the Si(100)2×1 surface.
Abstract: Field ion-scanning tunneling microscopy was employed to study the monolayer and multilayer adsorption behaviors of the C60 fullerene on the Si(100)2×1 surface. The C60 molecules reside stably in the trough at room temperature without rotation, encompassing the 8 neighbouring dimer-forming surface Si atoms with the nearest neighbour distance of 12 A. For the first and second layers, only local ordering of square and quasi-hexagonal patterns was observed. The orderly Stranski-Krastanov mode island formation with the hexagonal packing was observed above the third layer with its lattice constant of 10.4 A.
TL;DR: In this paper, the constrained lattice parameter distribution in the microstructure of a single crystal nickel-base superalloy caused by thermal mismatch is calculated along with the relation between constrained and unconstrained misfit.
Abstract: The constrained lattice parameter distribution in the microstructure of a single crystal nickel-base superalloy caused by thermal mismatch is calculated along with the relation between constrained and unconstrained misfit. The results are applied to interpret the diffraction spectra obtained from a neutron diffraction study of the temperature dependence of the lattice mismatch in SRR 99. The results are compared with other misfit measurements on SRR 99 and on superalloys containing high volume fractions of gamma-prime phase. 11 refs.