Solubility Limit Of Si Research Articles

Processing and characterization of MoAl1-xSixB solid solutions

The MAB phase MoAlB has attractive properties both at room and high temperatures. To further improve its properties, a possible way is to form solid solutions by partially substituting one of constituting elements in MoAlB. This work reports on the synthesis of MoAl1-xSixB solid solutions by powder metallurgy. Influences of sintering temperature, dwelling time, and composition of starting mixture on the solubility limit of Si in MoAlB have been investigated. The maximum solubility of Si was 0.91 at.%, corresponding to x = 0.03. Increase of Si content in the starting mixtures caused the formation of other competing phases. Phase composition and microstructure were characterized by x-ray diffraction method and scanning electron microscopy. A dense MoAl0·97Si0·03B solid solution has been achieved by hot-pressing a MoB/1.3Al/0.1Si mixture at 1200 °C with 25 MPa for 1 h, and its mechanical properties have been measured. An increase in strength and hardness is achieved by solid-solution strengthening. The flexural strength and the hardness of the solid solution are higher than those of MoAlB, viz. 385 MPa vs 307 MPa, and 14.89 GPa vs 8.43 GPa.

Investigation of the Cross-Sectional Structure and Isothermal Section at 1150°C of a Nb-Re-Si Alloy Fabricated Using a Tetra-Arc Furnace

Ternary Nb-Re-Si alloy samples were melted and pulled simultaneously in a tetra-arc furnace and rapidly water-quenched after heat treatment at 1150°C for 1200 h. The microstructures of the samples that had been water-quenched after heat treatment were observed and the Nb, Re and Si concentrations in the constituent phases were measured using an electron probe microanalyzer (EPMA). In the cross-sectional structure of the obtained alloy samples, the lower portion of the pulled part consists of Nb5Si3 and Nb-Re-Si ternary compound phases. By contrast, the upper portion consists of Nb5Si3 and Nb solid solution phases. The Nb solid-solution phase, Nb5Si3 and Nb-Re-Si ternary compound are in equilibrium. It was found that the solubility limit of Si in the Nb solid-solution phase ranges from 0.6 to 1.7 at%, while the solubility limit of Re in the Nb5Si3 phase is 1.3-2.0 at%. The maximum amount of Re in the Nb5Si3 phase in equilibrium with the Nb solid solution is about 0.9 at%.

First-principles investigation of activity and solubility of Si in Mo solid solution

The activity and solubility of Si in Mo solid solution were studied by the first-principles calculations and quasi-harmonic approximation. The lattice constants, bulk modulus, and formation enthalpies of Mo-Si intermetallics were investigated, and the thermodynamic properties of Mo were also calculated. The Si activity coefficient [Formula: see text] is approximately 10[Formula: see text] at 100 K, while it increases by about 15 orders of magnitude over the investigated temperature range (100–2000 K). It is clear that Si activity coefficient in Mo solid solution increased rapidly with the increasing temperature, which should be ascribed to the Si–Mo interaction being evidently stronger than Mo–Mo interaction. According to the calculated thermodynamic properties, the solubility curve of Si in Mo solid solution was also predicted. The solubility limit of Si in Mo solid solution is [Formula: see text]5.5 at.%, which agrees well with the other experiment and assessed results.

Solubility limit of Si in YAG at 1700 °C in vacuum

Measurement of the solubility limit of Si in yttrium aluminum garnet (YAG-Y3Al5O12) is crucial for understanding the mechanisms by which Si influences grain boundary mobility, and the mechanisms by which grain boundaries migrate. In the present work, the solubility limit of Si in YAG at 1700°C in vacuum (5×10−6Torr), which are the most common sintering temperature and environment for YAG, was measured for the first time. Measurements were conducted by wavelength dispersive spectroscopy (WDS), using polished YAG specimens with 3700ppm Si (0.8wt% SiO2). Si content to ensure saturation with Si. The accuracy of the WDS result was confirmed by using a series of doped specimens and by comparing to inductively coupled plasma mass spectrometry ICP-MS results. The results indicate that the solubility limit of Si in YAG at 1700°C (5×10−6Torr), is 980±60ppm. The measured Si solubility was found to significantly depend on the cooling rate, where for furnace cooled specimens the measured Si solubility was 650±60ppm. A second phase in triple junction was repeatedly observed when higher content of Si was used, confirming this work results.

The solubility limit of SiO2 in α-alumina at 1600 °C

The solubility limit of Si in α-alumina was measured using wavelength-dispersive spectroscopy on a scanning electron microscope. Samples were doped with Si such that the equilibrated material would contain two phases: mullite (3Al 2 O 3 ·2SiO 2 ) and alumina saturated with Si. Thus the amount of Si measured in the alumina grains represents the solubility limit. Measurements were conducted on water-quenched and furnace-cooled samples. For the quenched samples the Si solubility limit in Al 2 O 3 was found to be 188 ± 7 ppm at 1600 °C.

Cathodic arc deposited (Cr,Six)N coatings: From solid solution to nanocomposite structure

This paper aims to investigate the effect of silicon addition on the microstructure and mechanical properties of CrN coatings with an emphasis on their stability at high temperature. Thin films were deposited onto M2 tool steels using a cathodic arc deposition process. Silicon was introduced using duplex Cr–Cr3Si targets, allowing Si enrichment within the 0.6–10.8at.% range.The microstructure of the films was characterized by SEM and TEM, while their crystalline structure at room temperature and after high temperature annealing treatments (up to 1000°C) was determined by XRD analyses. Mechanical properties were deduced from nanoindentation measurements and from residual stress experiments.A minimum content of 2at.% was evidenced as the solubility limit of Si in CrN. Below this value, Si substituted Cr in the CrN lattice to form a solid solution. Above 2at.% Si, a nanocomposite bi-phased structure appeared, composed of Si-poor CrN nanograins surrounded by an amorphous Si-rich CrN matrix. Si addition induced significant grain shrinkage, without a significant effect on hardness at room temperature. For (Cr,Six)N films annealed at high temperatures, the nanocomposite structure allowed a delay in structural transformations linked to nitrogen losses, preserving better and more stable mechanical properties.

Near surface layer evolution in Zn+ ions implanted Si upon annealing treatments

The damaged layer in Zn implanted n-type CZ-Si(100) substrates was investigated by a secondary ion mass-spectrometry (SIMS), an X-ray diffraction (XRD) and an atomic force microscopy (AFM). The substrates were implanted with 64Zn+ ions at an energy of 100keV and an ion dose of 2×1016cm−2 with subsequent annealing at 400, 600, 700, 800, 900 and 1000°C for 60min in neutral/inert and oxygen atmosphere. A significant redistribution of Zn atoms in the damaged layer caused by the thermal annealing was found by SIMS. Zn concentration maximum exceeds a Zn solubility limit in Si; therefore, a decomposition of Zn solid solution in Si resulting in formation of zinc-containing phases in the surface layer should be expected. In an as-implanted state, the amorphous layer with thickness about 100nm, which located inside of a substrate on the depth more than value Rp, is formed. After thermal annealing at 800°C nanoparticles on the sample surface were revealed. After 1000°C annealing the radiation-induced defects completely disappeared, and Zn implanted atoms are revealed in the near surface layer.

Complex phase compositions in nanostructured coatings as evidenced by photoelectron spectroscopy: The case of Al–Si–N hard coatings

The chemical state evolution of the Al–Si–N thin films at various Si contents is investigated by x-ray photoelectron spectroscopy (XPS). The detailed evolution of the Al 2p, Si 2p, and N 1s photoelectrons line positions and widths are used to identify different chemical environments as the Si content is changed. The results are compared to x-ray diffraction (XRD) data that indicate the formation of a two-phase Al1−xSixN/SiNy composite when the solubility limit of 6 at. % of Si in AlN is exceeded. In contrast to XRD data, no particular effect is observed in the XPS data at the solubility limit of Si. Instead, two compositional regions can be identified that are separated by a distinct change in the evolution of core level binding energy differences and chemical shifts at about 10–15 at. % of Si. This silicon concentration is identified as the onset of the formation of a SiNy intergranular phase that is a few monolayers thick, having a chemical bonding similar to that in bulk silicon nitride. The observed changes in the XPS data coincide well with the structural changes in the material at different silicon contents. The unambiguous identification of phases, especially of minority phases from XPS data, is, however, not possible.

Titanium doped silicon layers with very high concentration

Ion implantation of Ti into Si at high doses has been performed. After laser annealing the maximum average of substitutional Ti atoms is about 1018 cm−3. Hall effect measurements show n-type samples with mobility values of about 400 cm2/V s at room temperature. These results clearly indicate that Ti solid solubility limit in Si has been exceeded by far without the formation of a titanium silicide layer. This is a promising result toward obtaining of an intermediate band into Si that allows the design of a new generation of high efficiency solar cell using Ti implanted Si wafers.

Structure, morphology and electrical properties of sputtered Zr–Si–N thin films: From solid solution to nanocomposite

DC reactive magnetron co-sputtering was used for the deposition of Zr–Si–N thin films. Si content ( C Si) was varied by changing the power applied on the Si target, whereas that on Zr target was kept constant. Three series of samples have been deposited at various substrate temperatures: room temperature, 240 °C and 440 °C. The evolution of morphology, crystalline structure, grain size and lattice constant has been investigated by X-ray diffraction analyses. Nanohardness, stress and resistivity measurements provide complementary information, which validate the proposed 3-step model for the film formation of the Zr–Si–N system deposited by reactive magnetron co-sputtering. For low Si content the Si atoms substitute the Zr atoms in the ZrN lattice. Above the solubility limit, a nanocomposite film containing ZrN:Si nanocrystallites and amorphous SiN y is formed. Further increase of Si content results in a reduction of grain size ( D), while the thickness of the SiN y layer at the crystallite surface remains constant. The increasing amount of the SiN y amorphous phase in the films is realized by increasing the surface to volume ratio of the crystallites. In this concentration range, the size of the crystallites in the Zr–Si–N films decreases according to the relationship C Si ∼ 1 / D. With increasing substrate temperature, the solubility limit of Si in ZrN decreases whereas the films' global nitruration ( C N / ( C Si + C Zr)) increases. The concentration dependence of the electrical resistivity is interpreted in terms of the variation of the SiN y layer thickness.

The effect of thermal treatments on the local geometry around indium in In and In + C high dose implanted Si

In the quest of new p-type dopants for Si, indium represents a promising candidate for its low diffusivity even if it presents a very low solubility and a very deep acceptor state. It has been recently shown that by co-doping In implanted Si with C, a shallower state forms related to In–C complexes. In this contribution we investigate the effect of C co-implantation on the In local configuration for In concentration higher than the solid solubility limit in Si. We find evidence that C has the property of preventing the formation of In clusters by binding In also at high concentrations. This interaction has a clear effect on the dopant concentration profile and on electrical properties of the material.

Gas immersion laser doping (GILD) for ultra-shallow junction formation

Gas immersion laser doping (GILD) is a very attractive technique to realize the ultra-shallow and highly doped junctions required by the International Technology Roadmap for Semiconductors (ITRS) for future CMOS technologies. In the present work, gaseous dopant precursors (BCl3) are chemisorbed on the Si surface, and partially incorporated during the melting/recrystallisation of the Si top layer induced by an UV laser pulse (λ=308 nm, pulse duration ≈25 ns). The resulting thickness and dopant concentration of the doped layer depend on the laser energy density and the number of chemisorption/laser-induced incorporation cycles (up to 200). GILD processed junctions are box-like and exhibit depths ranging from 14 nm to 65 nm, with sheet resistances ranging from ≈110 to 20 Ω/□ (respectively), dopant concentrations well above the B solubility limit in Si (up to 3×1021 at/cm3) at local thermodynamic equilibrium (LTE) and abruptness of 5–2 nm/decade. Moreover, in situ optical characterization shows the GILD technique capabilities to realize the sub-10 nm thick shallow junctions needed for the sub-40 nm node ITRS predictions.

Effects of Si addition on the microstructural evolution and hardness of Ti–Al–Si–N films prepared by the hybrid system of arc ion plating and sputtering techniques

Ti–Al–Si–N films were deposited on WC–Co substrates by the hybrid coating system of arc ion plating method for Ti–Al sources and dc magnetron sputtering technique for Si incorporation. The synthesized Ti–Al–Si–N films were revealed as composites of solid-solution (Ti,Al,Si)N crystallites and amorphous Si3N4 by instrumental analyses such as x-ray diffraction, high-resolution transmission electron microscopy, and x-ray photoelectron spectroscopy. The Si addition in Ti–Al–N films affected the refinement and uniform distribution of crystallites by percolation phenomenon of amorphous silicon nitride similar to that of the Si effect in TiN film. The solubility limit of Si in the Ti0.76Al0.24N crystal is believed to be about 6 at. %. No free Si was observed due to the very high ionization rate of nitrogen gas in the arc plasma. As the Si content increased up to about 9 at. %, the hardness of Ti–Al–N film steeply increased from 30 GPa to about 50 GPa. Ti–Al–Si–N films having the maximum hardness showed the nanocomposite microstructure consisting of fine (Ti,Al,Si)N crystallites, about 8 nm in size, dispersed uniformly in the amorphous Si3N4 matrix.

Formation and thermal stability of ultra-shallow p+ junctions in Si and Si1−x Gex formed by molecular beam epitaxy

Ultra-shallow junction layers are required for deep-submicron complementary metal-oxide-semiconductor transistors and quantum devices. The use of low temperature Si molecular beam epitaxy (MBE) has been investigated for the formation of 10 nm ultra-shallow doped layers. Uniformly B-doped Si layers, B delta-doped Si, and uniformly B-doped Si1−x Gex (x=0, 0.2, or 0.4) layers have been studied. Regardless of the growth technique (uniform versus delta-doped) or Ge concentration, the sheet resistance of the optimally-doped, as-grown samples were equivalent to idealized, box profiles having a carrier concentration equal to the B solid solubility limit in Si, 6×1020/cm3, which is a substantial improvement over the best reported, ion implanted shallow layers. The B in the as-grown, optimally-doped MBE layers is fully electrically active and does not require a post-growth anneal. The thermal budget of the layers was established so that the layers can be employed in a device fabrication process. The MBE-grown shallow-doped layers were not affected by 10 min thermal processing up to 700 °C. While substantial B redistribution occurred as a result of the 800 °C 10 min anneal, the sheet resistances of the MBE-grown layers are still less than ion implanted samples having the same junction depth. In addition, it was observed that the Ge alloy layers impeded the diffusion of B at 800 °C.

Effect of si addition on mechanical alloying behavior and creep properties of Al-10Ti-xSi alloys

Al-10Ti-xSi alloys (x=0∼6wt.%) have been mechanically alloyed under Ar atmosphere using an attritor and the alloying process has been investigated. From Al-10Ti composite powders, supersaturated Al(Ti) powders were obtained after mechanical alloying. In the ternary mixture, fine Si particles were observed to be distributed in the Al(Ti) matrix due to both the negligible solid solubility of Si in the Al matrix and the weaker chemical interaction of Si with Al, as compared with Ti. The sealed compacts were hot extruded to full density at 450°C with an extrusion ratio of 12:1. The microstructures and creep properties of the hot extruded alloys were examined. During consolidation, Si particles were dissolved in Al3Ti up to 4 wt.% Si to form the (Al(Si))3Ti phase, and the Ti7Al5Si12 phase was formed beyond the solubility limit of Si in Al3Ti. The transition from the Coble creep mechanism at low stresses and temperatures to dislocation one at high stresses and temperatures was observed. The stress and temperature of the transition from diffusional to dislocation creep became higher as Si concentration increased. This was due to an enhancement of Al3Ti particle strength with increasing Si content as a result of Si incorporation. Thus, the addition of Si enhances the creep resistance of the MA Al-10Ti alloy.

Broadening of the Si doping layer in planar-doped GaAs in the limit of high concentrations

Abstract A series of samples of GaAs planar doped with Si, grown by MBE at low substrate temperatures and with different doping concentrations, is investigated. A comparison of Shubnikov-de Haas measurements and self-consistent numerical calculations shows that a broadening of the doped region occurs in spite of the low growth temperature. The broadening occurs via segregation of the Si impurities with the growth surface when the solid solubility limit of Si in GaAs is exceeded. For the growth conditions used this limit is determined to be (2.1 ± 0.2) × 1019 cm−3. At high doping densities an intrinsic compensation mechanism becomes active, limiting the concentration of conduction electrons.

Direct evidence of arsenic clustering in high dose arsenic-implanted silicon

High dose (5–7.5×1015 cm−2) arsenic implantation was conducted in the energy range 50–120 keV into three types of (100)Si substrates: (i) bare Si, (ii) with a thermally grown screen oxide (775 Å), and (iii) preamorphized surface layer produced by self-implantation. The substrates were subsequently furnace annealed at 600 °C in N2. Cross-section transmission electron microscopy (XTEM) revealed that in all cases discrete layers of As related clusters and small dislocation loops occurred at depths matching the projected ranges of As into the Si substrates and original amorphous/crystalline interfaces respectively. The atomic profiles of As obtained by secondary ion mass spectrometry (SIMS) from these samples did not show any redistribution of As. The carrier concentration profiles from the spreading resistance measurements indicate that only 30% of As was electrically active. Comparison of XTEM and SIMS suggests that nucleation of the clusters occurred in the regions where As was present above the solid solubility limit in Si. The presence of recoiled oxygen has been found to stabilize the clusters.

Radiation-induced solute redistribution and precipitation

Abstract A simplified model for radiation-induced second-phase precipitation at point-defect sinks is proposed. The model yields a simple analytical expression for the shift of the solubility limit under irradiation. This shift is a function of the vacancy supersaturation, which includes kinetic parameters and the sink density. Qualitative agreement with the observed behaviour of the solubility limit of Si in Ni under irradiation is obtained. The model is shown to account only for extensions by irradiation of the two-phase fields of the phase diagrams, and points to yet unobserved behaviour of alloys under irradiation.

Solid Solubility of Si in Al under High Pressure

By making use of a 15 mm cubic anvil apparatus, Al–Si alloys of Si-concentration up to 15 at% were studied at a pressure of 54 kbar. The liquidus, solidus and solvus of the Al-rich alloys were determined by means of the 4-probe electric resistance measurement. The solubility limit of Si in Al was extended beyond 15 at% at 54 kbar in comparison with 1.59 at% at 0 kbar. The resistivity of the alloy was increased by a solution of Si with a gradient of 0.5 µΩcm/at% up to 15 at%Si. The alloy quenched under high pressure was examined by X-ray diffractometry showing that Si was completely solid-dissolved in Al. The quenched alloy was much more hardened than the ordinary two-phase alloy at 0 kbar.

Study of Tin Diffusion into Silicon by Backscattering Analysis

Diffusion of tin into Si from tin-doped oxide is studied by the backscattering and channeling analyses. The depth distribution of tin in Si can be fitted to complementary error functions. The diffusion coefficient can be expressed as D=0.054exp (-3.5eV/kT). The solubility limit in Si and the segregation constant between Si and SiO2 are estimated to be 6∼8×1019/cm3 and 0.066 at 1100°C∼1200°C, respectively. The lattice location of tin in Si is also determined by angular scan, and it is found that more than 90% of tin atoms occupy substitutional sites. Uniformity of the concentration over a silicon wafer is also checked with the microanalysis system by using backscattering and is found to be good. Effect of post-diffusion of phosphorous or boron on the depth profile of tin is also studied.