Difference In Atomic Radii Research Articles

Extended Defects and Pile-Up of Interstitial Oxygen in Silicon Wafer Due to MeV-Level Nitrogen Ion Implantation

The interactions between buried defects and impurities formed by MeV-level nitrogen ion implantation in silicon have been investigated. The interactions between the oxygen atoms in a CZ Si wafer and the defects introduced during annealing after implantation are discussed in terms of the amount, nature, morphology, and depth distribution of the defects. Oxygen atoms are found to be gettered in two different regions in the implanted layers. A shallow oxygen peak appears in regions near the surface (between 0.5 and 1.5 µm). A deep oxygen peak is also observed at locations with secondary defects, which mainly consist of elongated dislocation loops and dislocation networks. In this case, the gettered oxygen content is not especially influenced by the amount or nature of the generated defects. Rather, there is a good correlation between the gettered oxygen amount and the mismatch stress induced by the atomic radius difference.

Alloying and Strengthening Effects of Rare Earths in Palladium

The effect of adding small amounts of rare earth elements to Palladium is to strengthen the Palladium. These strengthening effects are discussed here, based on known phase diagrams of Palladium-rare earths, Palladium-rare earth alloying behaviour and atomic (or ionic) size effects. The Solid solubilities of the rare earths in Palladium, transition temperatures of various intermediate phases and eutectic temperature in these systems are influenced by the ionic (or atomic) size of the rare earth elements. A parameter, Hs, the product of the relative difference in atomic weights and the relative difference in atomic radii, between a rare earth and Palladium is used to examine the Solid solution strengthening effects caused by dilute rare earths. The alloying behaviours of Palladium with the rare earths are very analogous, and could perhaps be used to predict alloying behaviour in some unexamined Palladium systems.

Mechanism of Improved Thermal Stability of B in Poly-SiGe Gate on SiON

Post-annealing characteristics of in situ B-doped poly-SiGe films have been investigated. Thermal stability of substitutional B atoms at a supersaturated concentration was significantly improved by Ge doping, for example, the stability at 800°C for poly-Si0.6Ge0.4 films was nine times as high as that for poly-Si films. Both fast and slow processes exist for the deactivation of B. The fast process was due to movement of B atoms from substitutional to interstitial sites, enhanced by a local strain induced by the difference in atomic radii between Si and B atoms, and the slow process was due to trapping of B at grain boundaries during grain growth. The mechanism of the improved thermal stability of B atoms is discussed on the basis of local strain compensation by Ge atoms.

Precipitation of icosahedral quasicrystalline and crystalline approximant phases in Zr–Cu–(Co, Rh or Ir) metallic glasses

Zr 70Cu 30, Zr 70Cu 20Co 10, Zr 70Cu 20Rh 10 and Zr 70Cu 20Ir 10 glassy alloys were prepared by the single roller melt-spinning method and the crystallization process was studied by differential scanning calorimetry, X-ray diffraction and transmission electron microscopy, with an emphasis on the initial stage. The Zr 70Cu 30 metallic glass crystallizes through the direct precipitation of the stable crystalline phase from the matrix. The addition of Co, Rh and Ir to the Zr 70Cu 30 metallic glass induces the precipitation of metastable phases prior to the formation of the stable ones. The metastable phases are a Ti 2Ni-type compound for Zr 70Cu 20Co 10, a mixture of the Ti 2Ni-type compound and an icosahedral quasicrystalline phase (I-phase) for Zr 70Cu 20Rh 10, and the I-phase for Zr 70Cu 20Ir 10 metallic glasses. The different effects of Co, Rh and Ir addition are explained based on their difference in atomic radius.

Ar and K partitioning between clinopyroxene and silicate melt to 8 GPa

The relative incompatibility of Ar and K are fundamental parameters in understanding the degassing history of the mantle. Clinopyroxene is the main host for K in most of the upper mantle, playing an important role in controlling the K/Ar ratio of residual mantle and the subsequent time-integrated evolution of 40Ar/36Ar ratios. Clinopyroxene also contributes to the bulk Ar partition coefficient that controls the Ar degassing rate during mantle melting. The partitioning of Ar and K between clinopyroxene and quenched silicate melt has been experimentally determined from 1 to 8 GPa for the bulk compositions Ab80Di20 (80 mol% albite-20 mol% diopside) and Ab20Di80 with an ultraviolet laser ablation microprobe (UVLAMP) technique for Ar analysis and the ion microprobe for K. Data for Kr (UVLAMP) and Rb (ion probe) have also been determined to evaluate the role of crystal lattice sites in controlling partitioning. By excluding crystal analyses that show evidence of glass contamination, we find relatively constant Ar partition coefficients (DAr) of 2.6 × 10−4 to 3.9 × 10−4 for the Ab80Di20 system at pressures from 2 to 8 GPa. In the Ab20Di80 system, DAr shows similar low values of 7.0 × 10−5 and 3.0 × 10−4 at 1 to 3 GPa. All these values are several orders of magnitude lower than previous measurements on separated crystal-glass pairs.DK is 10 to 50 times greater than DRb for all experiments, and both elements follow parallel trends with increasing pressure, although these trends are significantly different in each system studied. The DK values for clinopyroxene are at least an order of magnitude greater than DAr under all conditions investigated here, but DAr appears to show more consistent behavior between the two systems than K or Rb. The partitioning behavior of K and Rb can be explained in terms of combined pressure, temperature, and crystal chemistry effects that result in changes for the size of the clinopyroxene M2 site. In the Ab20Di80 system, where clinopyroxene is diopside rich at all pressures, DK and DRb increase with pressure (and temperature) in an analogous fashion to the well-documented behavior of Na. For the Ab80Di20 system, the jadeite content of the clinopyroxene increases from 22 to 75 mol% with pressure resulting in a contraction of the M2 site. This has the effect of discriminating against the large K+ and Rb+ ions, thereby countering the effect of increasing pressure. As a consequence DK and DRb do not increase with pressure in this system.In contrast to the alkalis (Na, K, and Rb), DKr values are similar to DAr despite a large difference in atomic radius. This lack of discrimination (and the constant DAr over a range of crystal compositions) is also consistent with incorporation of these heavier noble gases at crystal lattice sites and a predicted consequence of their neutrality or “zero charge.” Combined with published DAr values for olivine, our results confirm that magma generation is an efficient mechanism for the removal of Ar from the uppermost 200 km of the mantle, and that K/Ar ratios in the residuum are controlled by the amount of clinopyroxene. Generally, Ar is more compatible than K during mantle melting because DAr for olivine is similar to DK for clinopyroxene. As a result, residual mantle that has experienced variable amounts of melt extraction may show considerable variability in time-integrated 36Ar/40Ar.

Curie Temperature of Disordered Alloys

The analysis of numerous crystallographic, Mossbauer, and magnetic experiments on the disordered alloys Fe-M (M = Al, Si, Ga, Sn) allowed us to describe their general qualitative peculiarities in the framework of the twoband Hubbard model [1, 2]. Subsequent reduction of the Hamiltonian is justified at concentrations of Μ lower than 10 at.% [3], the concentrational variations of the hybridization of two bands being neglected. Really, the fact that some features in the behavior of the Curie temperature ΤC (Fig. 1) and of the magnetic moment that practically is constant on the Fe atom at low concentrations [4-6] are common to different alloys in spite of large differences in atomic radii and electron configuration of metalloid, is indicative of limited number of the factors which determine Τc and the moment. This allows the Hamiltonian to be written in the following form:

Solid solubility metastable extension of rare earth metals in gold

Metastable extended solid solubility of rare earth (RE) metals in gold was studied by measuring the lattice parameters of solid solutions of rapidly solidified Au-RE alloys using X-ray diffraction. The cooling rate used for the preparation of the alloys was about 106 K/s. It was found that the metastable solid solubilities of Ce, Sm, Gd, Dy, Er, Yb and Y in gold were 0.3, 0.4, 1.5, 9.0, 13, 13.4 and 10 atrespectively. The solid solubilities of RE metals in gold increased with decreasing relative difference of atomic radius between the RE metal and gold. The extended solid solubilities of RE metals in Au, Ag, and Cu were compared. The relatively large solid solubility in gold is explained in terms of electron transfer from the RE atoms to gold atoms. Under the conditions of rapid solidification, the Au-RE alloys tended to form amorphous alloys more readily than do Ag-RE alloys.

Origin of ordering in B2-type transition-metal aluminides: Comparative study of the defect properties of PdAl, NiAl, and FeAl.

The physical mechanism for ordering and the properties of lattice defects in {ital B}2-type transition-metal (TM) aluminides are presented. It is shown that the size effect is inadequate in explaining the defect structure (and ordering) in these intermetallics. Such is the case evident in the prototypical example of PdAl, which is found to exhibit all the physical characteristics of strongly ordered alloys even though the difference in atomic radii between constituent Pd and Al atoms is very small. We obtain a high heat of formation, high antiphase boundary energies associated with the partial 1/2{l_angle}111{r_angle} slip, and the existence of triple defect (for the point defect structure) in PdAl. Comparative analyses are presented for PdAl, NiAl, and FeAl, and results reveal that the electronic structure at the TM sites plays a decisive role in the energetics (and types) of defects. The strong ordering in late TM aluminides of the {ital B}2 type is due to the {ital lack} of electronic screening from the TM {ital d} band to compensate the energetically unfavorable nearest-neighbor interaction between Al atoms when ordering is disrupted.

Comparative study of Si(100) surface stresses with dimerized group-IV adatoms.

A comparison of stresses among Si, C, and Ge dimers on the Si(100) surface has been performed by using first-principles calculations. The C dimer has been found to induce both tensile and compressive stresses depending on its azimuthal direction, while the Ge dimer has been found to induce almost identical stress to that of the Si dimer in the asymmetric form. Not only the atomic-radius difference among these group-IV atoms but also differences in the flexibility of their bonds determines the nature of the surface stresses.

TiAl基合金の高温強度に及ぼす添加元素の影響

After the heat-treatment of 1473 K-10.8 ks, the yield stress of TiAl(γ) base alloys, Ti-50 mol%Al, Ti-(50-C)mol%Al-C mol%X, and Al-(50-C)mol%Ti-C mol%X, was examined by the compression test as a function of temperature (295-1273 K) and the amount, C(0.5∼2.0), of third elements, X(Cr, Ga, Zr, Nb, Sb, Hf, Pd, Pt, Ta). Micro-hardnesses of γ in the alloys were measured at room temperature to confirm solid solution hardening. The microstructures were examined using OM, SEM, EPMA and XRD. The results obtained were examined with regression analysis and compared with the microstructures.The micro-hardness increased with the amount of additives. The increase was remarkable with increasing difference in atomic radius between Ti or Al and X atoms. In the temperature range of 295-1073 K, the yield stress is in proportion to the micro-hardness and influenced by the amount of Ti3Al phase and the grain size of γ phase. At 1273 K, the effect of the microstructure on the yield stress decreased and the effect of solid solution hardening become prominent.

Glass forming ranges of cobalt-base thin film alloys

The glass forming ranges of cobalt-base binary and ternary thin film alloys containing zirconium, titanium, niobium, molybdenum, vanadium and silicon have been studied in the cobalt-rich region. The minimum solute concentration for glass formation decreased with increasing difference in atomic radii or Pauling's electronegativity, as well as the cooling rate. Cobalt-base binary alloys readily showing glass formation are shown on the glass formation diagram. The values of atomic size effect in alloys sputtered at room temperature were about 0.065, and decreased with increase of cooling rate. The value was decreased in alloys having a large heat of formation. In ternary cobalt alloys containing zirconium, niobium, molybdenum and vanadium, the glass forming range could not be interpreted as the concept of atomic size effect alone.

Structural study of amorphous hydrogenated and unhydrogenated titanium carbide thin films by extended x-ray-absorption fine structure and extended electron-energy-loss fine structure.

Thin films of hydrogenated and unhydrogenated titanium carbide, known to be amorphous from x-ray and electron diffraction studies, nevertheless exhibit short-range order at the level of the first-nearest-neighbor shell when studied by extended x-ray-absorption fine structure and extended electron-energy-loss fine structure. This short-range order appears to consist of the same octahedrally coordinated units present in crystalline titanium carbide (NaCl structure), where a titanium atom is surrounded by an octahedron of six carbon atoms and vice versa. The persistence of this basic structural unit is attributed to the difference in atomic radii between C and Ti and to the strong nature of the Ti-C bond. A slight relaxation in interatomic distance relative to the crystalline state, which increases upon hydrogenation, is also observed. The atomic positions in the first coordination shell in amorphous titanium carbide are slightly displaced relative to the crystalline form. Yet, upon hydrogenation, this displacement decreases in the first shell, made of carbon atoms and vacancies, surrounding a Ti atom by 40% for the 4.5 at. % H and 60% for the 6 at. % H relative to the unhydrogenated amorphous ${\mathrm{TiC}}_{\mathrm{x}}$ films. By contrast, the structural disorder in the first shell of Ti atoms surrounding a C atom is practically unaffected by the addition of hydrogen. These results imply that the hydrogen atoms, instead of occupying tetrahedral vacancies, fill carbon vacancies in the amorphous phase as they do in crystalline ${\mathrm{TiC}}_{\mathrm{x}}$, in agreement with our previous findings from static secondary-ion mass spectroscopy and x-ray photoelectron spectroscopy.

Ultramicrohardness experiments on vapour-deposited films of pure metals and alloys

The ultramicrohardness of thin alloy films is determined by indentation experiments at very low loads. The indentation apparatus is briefly described. We measured the hardness of a number of pure metal films, either vapour deposited or magnetron sputtered. In addition, a detailed study was made of the composition dependence of the hardness of the six binary alloy systems of AgAuCu and AuCoNi. These films were prepared by high vacuum vapour deposition. The thickness of all the films was 1 μm. The hardness data were interpreted with the help of the metastable alloy phase diagram, e.g. as obtained by transmission electron microscopy. The results are discussed in terms of the blocking of the motion of dislocations, solid solution hardening, compound formation, grain size reduction due to alloying, and differences in atomic radii.

ELECTRON DIFFRACTION INVESTIGATION OF AMORPHOUS Gd-Co ALLOY FILMS

Electron diffraction technique was used to study the structure of various amorphous films of Gd-Co alloy and Lorentz electron microscopy was used to observe the related magnetic structure. Seven halos could be seen clearly in all the electron diffraction patterns obtained and the two smallest halos were located in the range s-1 (s = (2sinθ)/λ). Magnetic bubbles or in-plane domain structures wereobserved in these amorphous films. For amorphous alloys of this type consisting of two elements, such as rare-earth and transition metals with a large difference in atomic radius, we showed how to derive directly and qualitatively the relative co-ordination number of nearest neighbours between rare-earth metal atoms, - between transition metal atoms, and between rare-earth and transition metal atoms, merely from the diffraction intensity profiles in the range s-1. The influence of phase separation in the film on the magnetic anisotropy was also discussed.

Relation between hyperfine field and lattice-location measurements for heavy impurities in iron: Influence of radiation damage

The relation between the hyperfine interaction (HFI) and the lattice location of heavy impurities in iron is discussed in the light of results (see companion papers) on $^{169}\mathrm{Yb}$, $^{175}\mathrm{Yb}$, and Au in Fe. A compilation of all known results in Fe and Cu reveals a simple correlation between the difference in atomic radii of implanted and host atoms and the corrected extinction ratio in lattice-location experiments. A simple model is developed to account simultaneously for the annealing- and implantation-temperature dependence of the impurity HFI and lattice location in Fe between room temperature and 800 K. It is based on existing information concerning the nature and evolution of radiation damage in Fe: Impurity evolution is described in terms of a two-stage process involving (i) vacancy migration towards the impurity and (ii) migration of the impurity-vacancy complex, with the latter stage being much faster than the former. Quantitative agreement is found with our experimental results, as well as with results obtained on other impurities in Fe. It is suggested that the model is applicable in all cases where vacancy motion determines impurity evolution.

Thermodynamische untersuchung der systeme GaSb-InSb, AlSb-GaSb und AlSb-InSb

The mixing enthalpies of liquid alloys of GaSb-InSb, AlSb-GaSb and AlSb-InSb quasi-binary systems have been determined with the aid of a high temperature calorimeter. The maximum deviations of the mixing enthalpy values of the ternary alloys from those linearly interpolated between the mixing enthalpies of the binary melts with the respective compounds are: δ ( ΔH) exp max = + 162 J mol −1 for GaSb-InSb, δ ( ΔH) exp max = − 417 J mol −1 for AlSb-GaSb, δ ( ΔH) exp max = + 562 J mol −1 for AlSb-InSb. For the AlSb-GaSb and AlSb-InSb melts, the concentration dependence of δ ( ΔH) is not in agreement with the values predicted by the regular solution model. The discrepancy originates from the misfit in the atomic structure of the melt as a result of differences in atomic radii and association effects.

Interaction between interstitial hydrogen and substitutional solute atoms in solid solutions of niobium-base ternary alloys

The interaction between interstitial hydrogen and substitutional solute atoms has been investigated by the measurements of the hydrogen solubility and the influence of hydrogen charging on the half-width of the X-ray reflection lines in pure Nb, Nb-5%V, Nb-5%Mo and Nb-5%Ta alloys. In Nb-5%V and Nb-5%Mo alloys, the solubility considerably increases with respect to pure Nb. On the other hand, the solubility hardly changes in Nb-5%Ta alloy. With addition of hydrogen, the half-widths in pure Nb and Nb-5%Ta alloy show a monotonic increase, but in Nb-5%V and Nb-5%Mo alloys they show a minimum. The results are explained by the interaction of hydrogen with substitutional solute atoms. The interaction is considered to be caused by the internal strain induced by the difference in atomic radii between substitutional and solvent (Nb) atoms.

Surface enrichment in Cu 3Au and Au 3Cu alloys

It is well known that in equilibrated solid alloys surface and bulk compositions can differ appreciably. For homogeneous alloys two theories of surface enrichment are available, which in the present work are checked against new experimental data. One of these theories is based on the regular solution model of liquids and neglects lattice strain effects. It predicts surface enrichment with the component having the lowest heat of atomization. The second theory, which concentrates on differences in atomic radii and is often used to compute grain boundary segregation, predicts enrichment with the atom having the largest radius. Auger electron spectroscopy results are reported for the alloys Au 3Cu and Au Cu 3, for which the two theories predict opposite surface enrichments. It is concluded that the effects due to strain and heats of atomization, which would cause surface enrichments of opposite sign, just cancel out.

Thermodynamische Untersuchung des systems gold—nickel

The enthalpies of solution of solid nickel in liquid gold at 1110°C in the concentration range between 0 and 42.2 at. % nickel were determined with the aid of a high temperature calorimeter. The enthalpies of solution of gold—nickel solid solutions of the entire concentration range in liquid copper were determined in like manner. From the experimental results the enthalpies of mixing of the liquid and solid gold—nickel solutions could be obtained. An evaluation of the melting equilibria provided the excess entropies and the free enthalpies of mixing of the liquid alloys. Besides the change of the interatomic attraction on alloy formation, the marked difference in atomic radii of the components in the gold—nickel system is of considerable influence on the thermodynamic properties of both the solid and the liquid alloys. This is shown in a discussion.

Abschätzung von Zustandsdichten des Silbers in a-Silber-Mischkristallen mit Gallium, Indium, Germanium und Zinn auf Grund thermodynamischer Untersuchungen mittels galvanischer Festkörperzellen / An estimation of densities of state of silver in a-solid solutions of silver with gallium, indium, germanium and tin based on thermodynamic investigations by means of solid state galvanic cells

Abstract The partial free enthalpies of formation of the binary a-solid solutions of silver with gallium, indium, germanium and tin were determined at 1000 °K from the EMF of suitable solid state galvanic cells. A further evaluation of the results taking into account known enthalpies of for­mation yielded the complete partial and integral excess functions of these solid solutions. An analysis of the difference of the excess values of the partial free enthalpies of formation of the components showed that the lattice distortion, due to differences in atomic radii of the solid solutions studied, is not very significant. Differences in the structure between the solid solution and its components can be clearly noted only in the case of the silver-germanium solid solutions. The energetics of the alloys are determined principally by the filling of the 5s1 conduction band of the silver by the electrons contributed by higher-valent constituents. From the thermodynamic results the density of state of the conduction band of the silver was estimated to be smaller than 0.31 electr. per atom and eV. The density of state increases with increasing concentration of the alloying component; this can be explained by a change in the Fermi surface in the silver host lattice