Metal-rich Phases Research Articles

Intermetallic and metal-rich phases in the system Li–Ba–In–N

Three new intermetallic phases, BaLi 2.1In 1.9, BaLi 1.12In 0.98, and BaLi 1.06In 1.16 and two subnitrides Li 35In 45Ba 39N 9 and LiIn 2Ba 3N 0.83 have been synthesized and their crystal structures have been determined. According to single crystal X-ray diffraction data BaLi 2.1In 1.9 and BaLi 1.12In 0.98 crystallize with hexagonal symmetry (BaLi 2.1In 1.9: P6 3/ mmc, a=10.410(2), c=8.364(2) Å, Z=6, V=785.0(2) Å 3) and BaLi 1.12In 0.98: P6/ mmm, a=17.469(1), c=10.6409(7) Å, Z=30, V=2813.5(8) Å 3), while BaLi 1.06In 1.16 has a rhombohedral structure ( R-3 c, a=18.894(3), c=85.289(17) Å, Z=276, V=26368(8) Å 3). BaLi 2.1In 1.9 is isostructural with the known phase BaLi 4. The phase BaLi 1.12In 0.98 is structurally related to Na 8K 23Cd 12In 48, while BaLi 1.06In 1.16 is isostructural with Li 33.3Ba 13.1Ca 3. A sample containing structurally similar BaLi 1.12In 0.98 and BaLi 1.02In 1.16 was also investigated by transmission electron microscopy. Li 35In 45Ba 39N 9 and LiIn 2Ba 3N 0.83 crystallize with tetragonal ( I-42 m, a=15.299(2), c=30.682(6) Å, Z=2, V=7182(2) Å 3) and cubic ( Fd-3 m, a=14.913(2) Å, Z=8, V=3316.7(7) Å 3) symmetry, respectively. While the first-mentioned subnitride belongs to the Li 80Ba 39N 9 structure type, the second extends the structural family of Ba 6In 4.78N 2.72. The structural features of the new compounds are discussed in comparison to the known phases and the results of total energy calculations.

Leakage Reduction by Thermal Annealing of NiPtSi Silicided Junctions and Anomalous Grain-Incompatible Pt Network

Using highly reliable damage-free junctions, the effectiveness and limitation of Pt addition for the stabilization of thin NiSi films are accurately specified and practically formulated in terms of the thermally induced leakage. In addition to the thermal leakage, the unexpected emergence of initial leakage is also witnessed and attributed to the emission of Si interstitials during silicidation and the subsequent formation of boron interstitial clusters. Rapid evanescence of the initial leakage by post-annealing is also successfully demonstrated owing to the Pt-induced thermal stabilization. Moreover, unlike other Pt distributions considered so far, Pt atoms are revealed to concentrate in a distinctive manner, forming an anomalous in-layer web-like structure which even extends within single NiSi grains. This grain-incompatible Pt network is thought to be a remnant of Pt-aggregation around grain boundaries of an earlier metal-rich silicide phase (e.g., Ni2Si), incorporated and left intact in the final phase (i.e., NiSi). Such intermediate-phase Pt-rearrangement may have interfered with the phase transition sequence and reoriented the final NiSi grains to constitute a crystallographically stable and thermally robust interface structure, resulting in the effective stabilization by Pt addition.

The post-depositional accumulation of metal-rich cyanide phases in submerged tailings deposits

Abstract The characterization and accumulation pathway of metal-rich cyanide phases in mine-contaminated Balmer Lake (Ontario, Canada) were assessed through detailed examination of sediment mineralogy and porewater composition. The near-surface deposits in the lake consist of fine-grained calcareous tailings intermixed with natural organic-rich lake sediments. The tailings contain blue to greenish Fe-dominant cyanide that has formed in situ within the tailings. X-ray diffraction confirmed the presence of a mixed ferri/ferrocyanide [ Fe 4 III ( Fe II ( CN ) 6 ) 3 ] , commonly referred to as “Prussian Blue” but it is likely other metal–cyanide complexes are present as evidenced by the distinct colour variations. The cyanide phases occur in up to 1 wt.% as discrete particles and as bedded layers, where the cyanide phases act to cement other siliceous tailings components into a heterogeneous blend. Energy Dispersion X-ray Spectroscopy (EDS) analyses indicate that the authigenic cyanide precipitates contain variable amounts of Ni, Cu and Zn. Quantitatively, the cyanide compounds represent the dominant repository for Cu in Balmer Lake sediments. For Ni and Zn, cyanide associations are secondary in importance to Fe oxyhydroxides. High-resolution porewater profiles and solubility considerations suggest that the formation of the cyanide complexes is a feature of historical (pre-1990) conditions when aqueous cyanide concentrations were higher in the lake.

In situ study of the formation of silicide phases in amorphous Ni–Si mixed layers

In this paper, we investigated Ni silicide phase formation when Si is added within an as deposited 50 nm Ni film. A series of 22 samples with a Si content varying from 0 to 50 at. % was prepared and systematically investigated with in situ x-ray diffraction. The inert oxide substrate was used to identify the phases which first crystallize in an amorphous Ni–Si mixture of a given concentration. The noncongruent silicides Ni3Si and Ni3Si2 are never observed to crystallize readily out of the mixture. A remarkable observation is the initial crystallization at low temperature of a hexagonal Ni-silicide, observed over a broad mixed layer composition [35–49%Si]; this hexagonal phase nucleates readily as a single phase [39–47%Si] or together with Ni2Si [35–38%Si] or NiSi [49%Si]. This low-temperature phase is related to the high temperature θ-phase, but covers a wide composition range up to 47%Si. For the same Ni–Si films deposited on Si(100), the initial nucleation of the Ni(Si) mixture is similar as for the samples deposited on SiO2, such that the complex sequence of metal-rich Ni-silicide phases typically observed during Ni/Si reactions is modified. For samples containing more than 21%Si, a simpler sequential phase formation was observed upon annealing. From pole figures, the phase formation sequence was observed to have a significant influence on the texture of the technologically relevant NiSi phase. For mixture composition ranging from 38% to 43%Si, the initial transient θ-phase appears extremely textured on Si(100). The observed transient appearance of a hexagonal phase is of importance in understanding the phase formation mechanisms in the Ni–Si system.

As-rich InAs(001)-(2×4) phases investigated by in situ surface x-ray diffraction

Surface x-ray diffraction has been employed, in situ, to measure InAs(001)-(2×4) surface phases under technologically relevant growth conditions. For the As-rich (2×4) phase, the authors obtain good agreement between the data and the β2(2×4) surface reconstruction model. Comparison of our measurements on the (2×4) phase measured close to the metal-rich phase transition to models from density functional theory suggests a mixture of α2(2×4) and β2(2×4) surface structures present on the surface.

Ni–Pt silicide formation through Ti mediating layers

With Ni 1− x Pt x Si, the variation in queue time between the final surface cleaning and Ni–Pt deposition represents a significant manufacturability issue. A short queue time is often difficult to maintain, leading to the formation of an oxide layer on the Si substrate prior to Ni–Pt deposition that can affect the formation of Ni 1− x Pt x Si and its texture. In this manuscript, it will be shown that an extended queue time prior to Ni–Pt deposition leads to morphological changes in the Ni 1− x Pt x Si formation sequence. A layer of Ti deposited between Ni–Pt and Si reduces the native oxide and may facilitate Ni 1− x Pt xSi formation. With increasing Ti thickness, the presence of metal-rich phases is gradually reduced and the formation temperature of Ni 1− x Pt x Si increases, suggesting a direct formation of Ni 1− x Pt x Si from Ni–Pt. In the presence of an interfacial oxide, an increase in formation temperature is also observed with increasing Ti interlayer thickness. When the Ti layer is sufficiently thick, the phase formation sequence becomes relatively insensitive to the presence of an interfacial oxide or extended queue time.

Rare‐Earth Metal‐Rich Antimonides: Syntheses, Structures, and Properties of Tm3Sb and Lu7Sb3.

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Phase evolution during crystallization of nanocomposite alloys with Co:Fe ratios in the two-phase region of the binary Fe–Co phase diagram

A series of alloys was prepared to investigate the crystallization of Co-rich HiTPerm-type alloys [(Co1−xFex)88Zr7B4Cu1] with Fe:Co ratios within or near the two-phase (bcc+fcc) region of the binary phase diagram. The goal of this work is to better understand the phase evolution and crystallization of alloys in which the Fe–Co binary phase diagram predicts more than one transition metal rich primary crystalline phase to be present in equilibrium at the primary crystallization temperature. X-ray diffraction, transmission electron microscopy, and high-temperature vibrating-sample magnetometry have been performed to identify the first phase to crystallize and to follow the evolution of phases during crystallization. The bcc phase appears to be the primary crystalline phase that forms first after annealing at 450°C for 1h, in agreement with previous work on Co-rich nanocomposite alloys. We observe that as the Co concentration is increased, the fcc crystalline phase forms at lower annealing temperatures and its volume fraction increases for a given annealing temperature.

Rare-Earth Metal-Rich Antimonides: Syntheses, Structures, and Properties of Tm3Sb and Lu7Sb3

The two most metal-rich lanthanide antimony phases known were obtained from high-temperature solid state syntheses, that for Tm3Sb being of greater difficulty because of its apparent incongruent melting. The Tm3Sb phase crystallizes in the tetragonal space group P42/n (No. 86) with a Ti3P-type (Pearson: tP32) structure, a = 12.2294(5) Angstrom, c = 5.9852(5) Angstrom, and Z = 8. The phase Lu7Sb3 exhibits a Sc7As3-type tetragonal structure, I4/mcm (No. 140) (tI56), with a = 15.5974(7) Angstrom, c = 8.8130(7) Angstrom, and Z = 8. Both structures are described in terms of compact arrays of condensed chains of metal polyhedra (tetrahedral, tetrahedral star, trigonal prismatic, cubic) together with six- to nine-coordinate Sb in metal polyhedra. Magnetic susceptibility data on the paramagnetic Tm3Sb are also reported.

Formation and morphological stability of NiSi in the presence of W, Ti, and Ta alloying elements

The formation and degradation of NiSi films has been studied when elements with a high melting point (W, Ta, and Ti) were added to pure Ni films as an alloying element. In situ techniques were used to characterize the phase stability and the morphological stability of the NiSi layers. Depending on the concentration of the alloying element, two distinct regimes could be distinguished. First, the addition of a small quantity of an alloying element (e.g., <10 vol % W) had little impact on the formation of NiSi, but significantly improved the morphological stability. In some cases, the agglomeration temperature was increased by 100 °C. Second, for higher concentrations (e.g., <10 vol % W), no crystalline metal rich phases (NixSiywith x>y) could be observed prior to NiSi formation. Furthermore, a significant increase was observed of the apparent activation energy for NiSi formation.

Nanostructure and microstructure of laser-interference-induced dynamic patterning of Co on Si

We have investigated the nanostructure and microstructure resulting from simultaneous ns laser irradiation with deposition of Co films on Si(001) substrates. The spatial order and length scales of the resulting nanopatterns and their crystalline microstructure were investigated as a function of film thickness h and laser energy density E using a combination of atomic force, scanning electron and transmission electron microscopies. The results could be classified into two distinct categories based on the laser energy density used. It was observed that the thickness-dependent E required to melt the Co film (ECo) was lower than for Si (ESi) primarily because of the higher reflectivity of Si. Consequently, for energy densities ECo < E1 < ESi that preferentially melted the Co film, spatially ordered nanoparticles were formed and were attributed to capillary-driven transport in the liquid phase. The ordering length scale corresponded to the interference fringe spacing Λ and the microstructure was primarily Co metal and a metal-rich silicide phase. The native oxide layer played an important role in minimizing the Co–Si reaction. For laser energy densities E2 ⩾ ESi, spatially ordered patterns with periodic length scales L < Λ were observed and resulted from interference of an incident laser beam with a beam transmitted into the Si substrate. These nanopatterns showed one- as well as two-dimensional spatial ordering of the nanostructures. The microstructure in this laser energy regime was dominated by silicide formation. These results suggest that various nanostructures and microstructures, ranging from nearly pure metal to a Si-rich silicide phase, can be formed by an appropriate choice of the laser energy simultaneously with film growth.

Effects of additive elements on the phase formation and morphological stability of nickel monosilicide films

Alloying elements can substantially affect the formation and morphological stability of nickel monosilicide. A comprehensive study of phase formation was performed on 24 Ni alloys with varying concentrations of alloying elements. Silicide films have been used for more than 15 years to contact the source, drain and gate of state-of-the-art complementary-metal-oxide-semiconductor (CMOS) devices. In the past, the addition of alloying elements was shown to improve the transformation from the high resistivity C49 to the low resistivity C54-TiSi 2 phase and to allow for the control of surface and interface roughness of CoSi 2 films as well as produce significant improvements with respect to agglomeration of the films. Using simultaneous time-resolved X-ray diffraction (XRD), resistance and light scattering measurements, we follow the formation of the silicide phases in real time during rapid thermal annealing. Additions to the Ni–Si system lead to modifications in the phase formation sequence at low temperatures (metal-rich phases), to variations in the formation temperatures of NiSi and NiSi 2, and to changes in the agglomeration behavior of the films formed. Of the 24 elements studied, additions of Mo, Re, Ta and W are amongst the most efficient to retard agglomeration while elements such as Pd, Pt and Rh are most efficient to retard the formation of NiSi 2.

Simultaneous growth of Ni5Ge3 and NiGe by reaction of Ni film with Ge

The reaction between nanometric Ni films and Ge is analyzed using isothermal x-ray diffraction measurements and transmission electron microscopy. It is found that NiGe is formed during deposition at room temperature. The metal rich phase that grows during heat treatment has been clearly identified to be Ni5Ge3. The simultaneous growths of Ni5Ge3 and NiGe have been observed on amorphous and polycrystalline germanium. This is in contrast with the usual sequential growth reported in thin films.

Formation of optically active osmium silicide in silica using ion implantation and thermal annealing

Optically active metal silicides offer an interesting direct band gap material that in principle can be integrated into Si-based microelectronics to provide optoelectronic functionality. In particular the isostructual phases of Os2Si3 and Ru2Si3 and their alloys could be tailored to yield a response ranging from the visible blue to the near infrared. The metal-rich phase, Os2Si3 poses some difficulties for the annealing process since it is the low temperature phase, and thus difficult to fabricate in silica due to the high temperature needed for precipitation. Ion implantation of Os and Si ions above the stoichiometric ratio resulted in the formation of Os2Si3 at 1100°C, as indicated by Rutherford backscattering. Faint visible photoluminescence was detected with a peak centered near (520nm) corresponding to the previously reported bandgap of 2.3eV [L. Schellenberg, H.F. Braun, J. Muller, J. Less-Common Met. 144 (1988)]. To the best of our knowledge this is the first reported photoluminescence from this material.

Exploratory synthesis of reduced rare-earth-metal halides, chalcogenides, intermetallics: New compounds, structures, and properties

A new direction in reduced rare-earth-metal (R) compounds opened up when tantalum (and niobium) were adapted to use as virtually faultless containers for these reactions, as these gave immediate access to many new metal-rich phases and structures. Examples are summarized for the new binary dihalides (e.g., Pr, Nd, Dy, Ho, Tm), metallic diodides (Sc, La, Ce, Gd), and metal–metal bonded chains (Sc, Y, Gd, Lu) that were so discovered. Furthermore, a large array of condensed metal cluster, chain, and sheet halides arise when a stoichiometric amount of a diverse variety of nonmetal or metal atoms is included to serve as an interstitial, the earliest examples originating with traces of common impurities. A change in anion charge type to telluride affords a whole new regime of condensed metal-rich cluster compounds and structures, including such remarkable examples as (Sc, Gd, Dy) 2Te, Lu 11Te 4, Lu 8Te, and Sc 6PdTe 2. Also, a number of novel Zintl phases, interstitial derivatives of the type R 5Ge 3Z, quasicrystals, and their approximants are generated in other intermetallic systems. Generalities in structures and bonding are described along the way.

NiGe on Ge(001) by reactive deposition epitaxy: An in situ ultrahigh-vacuum transmission-electron microscopy study

We use an ultrahigh-vacuum transmission-electron microscopy, equipped with an electron-beam evaporator directed at a heating stage in the pole piece, to follow the reaction pathway of Ni on Ge(001) substrate at 300 °C. Using reactive deposition, we illustrate that epitaxial orthorhombic NiGe (a=5.381Å, b=3.428Å, and c=5.811Å) phase can be grown directly without the initial formation of metal-rich Ni2Ge phase. The epitaxial orientation of the NiGe islands and the underlying Ge(001) substrate were found to be NiGe(1¯01)∕∕Ge(001) and NiGe[010]∕∕Ge[110].

Reactive Diffusion in the Ni-Si System: Phase Sequence and Formation of Metal-Rich Phases

Reactive Diffusion in the Ni-Si System: Phase Sequence and Formation of Metal-Rich Phases

Evolution of microstructure in Ti–Ta bilayer thin films on polycrystalline-Si and Si(001)

We have studied the formation of titanium silicides in the presence of an ultra-thin layer of Ta, interposed between Ti and Si, using in situ X-ray diffraction (XRD), resistance measurements, elastic light scattering and exsitu transmission electron microscopy. On both poly-Si and Si(001) substrates the Ta thickness was varied from 0 to 1.5 nm while the Ti thickness was held constant at ∼27 nm. The time-resolved XRD shows that the volume fraction of the C40 and metal-rich silicide phases grows with increasing Ta layer thickness. Among the Ta thicknesses we examined, 0.3 nm is the most effective in lowering the C49–C54 transformation temperature. Ex situ texture analysis shows that the C54 disilicide film is predominantly (010) textured for the Ti/0.3 nm Ta sample on both poly-Si and Si(001). The final C54 texture is significantly different for Ta layers thinner or thicker than the optimal 0.3 nm. This suggests that the most effective thickness for lowering the C54 formation temperature could be related to the development of a strong (010) texture.

Application of diamond-like carbon coatings on steel tools in the production of precision glass components

The application of highly wear-resistant diamond-like carbon (DLC) coatings with an extremely low friction coefficient and a low wettability with regard to glass melt has been performed on steel substrates. These coatings are of high interest for the glass industry to improve the performance of high precision glass forming tools for various products like high precision glass tubes for laboratory equipment or in the fabrication of wine glasses. Me-DLC coatings are a special type of DLC coating and consist of a metal-rich carbon phase near the metal substrate interface, which is graded into a carbon-rich diamond-like phase towards the interacting surface. The metal-rich phase optimises the adhesion to the ground substrate and the metal type can be varied (Ti, Cr, Si, etc.). The metal content influences the surface properties of the coating like its wettability. For the glass-producing industry there are mainly two advantages: environmentally hazardous release agents can be abandoned and the purity and surface quality of the produced glass products can be drastically improved. The presentation describes related vacuum deposition techniques and gives examples for industrial applications.

Low-Metallicity Gas Clouds in a Galaxy Protocluster at Redshift 2.38

We present high-resolution spectroscopy of a QSO whose sight line passes through the halo of a pair of elliptical galaxies at redshift 2.38. This pair of galaxies probably lies at the center of a galaxy protocluster and is embedded in a luminous extended Lyα nebula. The QSO sight line intersects two small gas clouds within this halo. These clouds have properties similar to those of high-velocity clouds seen in the halo of the Milky Way. The gas is in a cool (<2 × 104 K) and at least 20% neutral phase, with metallicities in the range -3.0 < [Fe/H] < -1.1 and neutral hydrogen column densities of ~1019.5 cm-2. The origin of these clouds is unclear. The presence of low-metallicity gas within this possible protocluster implies either that the intracluster medium has not been enriched with metals at this redshift, or the clouds are embedded within a hot, ionized, metal-rich gas phase.