Nickel Silicon Research Articles

Development of metallic ion beams using ECRIS

The low energy metallic ion beams find wide applications in various research fields of the materials science. Several metallic ion beams have been developed successfully using the electron cyclotron resonance (ECR) ion source based low energy ion beam facility (LEIBF) at Inter University Accelerator Centre (IUAC), New Delhi. These metallic ion beams were developed by different techniques and utilized for the synthesis of the metal nanoparticles inside various host matrices. The special emphasis was put on the development of the nickel (Ni) and iron (Fe) ion beams using volatile compounds. The hydrocarbon cluster beams were also observed in the charge state distribution (CSD) of the ECR plasma produced by the dissociation of the vapors from the volatile compound of iron. Ni and Fe ion beams were utilized to make a dilute magnetic semiconductor phase (nickel in silicon and iron in silicon) by implantation method. The ion beams extracted from the metallic ECR plasma have been analyzed in energy and momentum using a high mass resolution dipole magnet. Studies of the CSD of the output metallic ion beams and the co-relations among various source parameters are presented.

Two-dimensional facet crystal growth of silicon from undercooled melt of Si–Ni alloy

The two-dimensional facet crystal growth of silicon from the undercooled melt of silicon–nickel alloys has been investigated using a phase-field model. The phase-field parameters derived at the thin interface limit and the anisotropic interface energy model proposed by Eggleston et al. have been used in the simulation. The calculated dendrite growth velocity depends on the interface width and the correct values are obtained when the interfacial Péclet number is sufficiently small. The growth velocity follows a power law relation to undercooling and the exponents are approximately two for Si–10 wt.% Ni alloy and approximately three for Si–20 wt.% Ni alloy. A dendrite grows maintaining its tip shape and a scaling law between the tip size of a dendrite and the growth velocity is confirmed. The phase-field simulations have been compared with the experimental data on the facet dendrite growth velocity in a thin liquid film of Si–6 wt.% Ni alloy and both are acceptable in agreement.

Improved contacts on a porous silicon layer by electroless nickel plating and copper thickening

In this paper stable, low-resistance contacts on porous silicon have been realized by electroless nickel deposition from a very weakly alkaline solution followed by copper thickening. The porous silicon layer after nickel deposition has been analysed by x-ray diffraction, which shows that a porous silicon nickel structure is successfully achieved from the bath. FESEM studies have been performed which show that the surface morphology of the porous silicon layer remains intact after nickel–copper plating. The mean roughness of the porous silicon surface has been found to improve after nickel plating from the AFM studies. Electrical characterization shows that the J–V characteristics of the nickel–copper-plated porous silicon lateral structure contact is fairly linear up to a certain value of applied voltage. Specific contact resistance of the nickel on porous silicon has been measured for the first time and has been found to be of an order of magnitude lower than that of other metals. No significant ageing is visible in this electroless nickel contact contrary to the vacuum-evaporated nickel contact.

Electrodeposition and Thermal Treatment of Nickel Coatings Containing Molybdenum and Silicon

Ni+Mo+Si coatings were obtained by electrolytic codeposition of crystalline nickel with molybdenum and silicon powders from an electrolyte containing suspension of these powders. These coatings were obtained in galvanostatic conditions, at the current density of -0.100 A cm-2. Thermal treatment of these coatings in argon atmosphere was done at temperature of 1100oC for 1 hour. A scanning electron microscope was used for surface morphology characterization of the coatings. Chemical composition of obtained coatings was determined by Xray fluorescence spectroscopy method and phase composition investigations were conducted by Xray diffraction method. It was found that introduction of molybdenum and silicon into nickel matrix, causes of obtained coatings about very rough surface. Thermal treatment of these coatings influenced their surface. The surface after thermal treatment is more compact and less rough than the as-deposited one.

Recombination activity of nickel in Czochralski silicon during rapid thermal process

The recombination activity of nickel in p- and n-type Czochralski silicon after rapid thermal process (RTP) in N 2, O 2 or Ar ambient has been investigated by the microwave photoconductivity decay technique. The effective lifetime of silicon decreases monotonically with increasing nickel in-diffusion temperature, and exhibits a step-like behavior at nickel in-diffusion temperature of 900 °C, which indicates that most of nickel atoms precipitate in the bulk no matter what kind of conducting type if the annealing temperature is above 900 °C under RTP. It is also found that the ambient during RTP almost has no effect on the recombination activity of nickel in silicon, which suggests point defects almost have no influence on the nickel precipitation.

On the thermostability of electrical properties of p-Si<P, Ni> and p-Si<P, Cu>

Silicon samples with various nickel and copper concentrations were studied by the method of isochronal annealing. In so doing, the temperature of total decomposition of Ni and Cu centers was found to depend on the concentration of nickel and copper atoms in silicon overcompensated from the n-to the p-type. The decomposition temperatures of Ni and Cu centers increase with decreasing the distance between the impurity atoms. This effect is explained by the peculiarities in the distribution of the compensating-impurity atoms within the fluctuation regions being formed in silicon during doping.

Improvement in strength and electrical conductivity of Cu–Ni–Si alloys by aging and cold rolling

In order to find the optimum conditions to obtain copper–nickel–silicon (Cu–Ni–Si) alloys with high strength and high electrical conductivity, the aging characteristics of micro-Vickers hardness and electrical resistivity of different Cu–Ni–Si alloys were systematically measured at room temperature. The alloys were isochronally or isothermally aged after solution treatment. The effects of cold rolling after solution treatment as well as the alloy composition on the hardness and resistivity were studied. The results show that there appears to be an optimum composition ratio of nickel to silicon for obtaining high strength and high electrical conductivity, and cold rolling after solution treatment is effective in increasing the strength and electrical conductivity. The addition of a small amount of iron to the copper base alloys appears to improve these above-mentioned properties. A multi-step aging process coupled with cold rolling was proposed for realizing Cu–Ni–Si alloys with high strength and high electrical conductivity. The mechanism of precipitation in cold-rolled alloys was discussed on the basis of the results obtained.

Nickel silicon thin film as barrier in under-bump-metallization by magnetronsputtering deposition for Pb-free chip packaging

In the search for a Pb-free compatible under-bump-metallization (UBM) barrier material, magnetron sputtering of a nonmagnetic nickel silicon alloy (NiSi) target was used to deposit a low-stress polycrystalline NiSi thin film. In the reaction with SnAg3.0Cu0.5 solder, NiSi was found to have greatly reduced reaction and intermetallics (IMC) formation rates compared with sputtered NiV. A continuous layer of IMCs in NiSi UBM-solder joint remains stable after 10 reflows and 1000 h thermal aging tests, resulting in preferred bulk solder failure mode in ball shearing/pull testing. Our results demonstrate that NiSi is a highly promising thin film barrier material suitable for Pb-free solder bumping.

Mechanical characterization of single crystal silicon and UV-LIGA nickel thin films using tensile tester operated in AFM

This paper describes the mechanical characteristics of microscale single crystal silicon (SCS) and UV-LIGA nickel (Ni) films used for microelectromechanical systems (MEMS). A compact tensile tester, operated in an atomic force microscope (AFM), was developed for accurate evaluation of Young's modulus, tensile strain and tensile strength of microscale SCS and UV-LIGA Ni specimens. SCS specimens with nominal dimensions of 20 μm in thickness, 50 μm in width and 600 μm in length were prepared by a conventional photolithography and etching process. UV-LIGA Ni specimens, with a thickness of 15 μm, a width of 50 μm and a length of 600 μm in nominal dimensions, were also fabricated by electroplating using a UV thick photoresist mould. All specimens have line patterns on their specimen gauge section to measure axial elongation under tensile loading. The SCS specimens showed a linear stress–strain response and fractured in a brittle manner, whereas the UV-LIGA Ni specimens showed elastic–inelastic deformation behaviour. Young's modulus of SCS and UV-LIGA Ni specimens obtained from tensile tests averaged 169.2 GPa and 183.6 GPa, respectively, close to those of bulk materials. However, the tensile strength of both materials showed a larger value than the bulk materials: 1.47 GPa for the SCS and 0.98 GPa for the Ni specimens. Yield stress and breaking elongation of UV-LIGA Ni specimens were also quite different from those of the bulk Ni because of the specimen size effect on inelastic properties.

Microstructure and abrasion resistance of Ni-Cr-B-Si alloys

In this study the microstructural characterization and the abrasion resistance of a series of Ni based alloys containing 10 at. % Cr, 5-15 at. % B and 5-20 at. % Si are presented. The formed hard components are borides of chromium and nickel (CrB, Cr 5 B 3 , Ni 3 B) and a silicon nickel compound (Ni 5 Si 2 ) in a matrix. These phases appear either in primary solid solution form or in biphased eutectic form or in secondary fine precipitates form. The loss of mass, the abrasion factor and the microhardness of the various phases versus time were measured. The best results are obtained for 10 at. % B and Si contents of about 10 at. %.

Effect of ultrasonic power on the heavy aluminum wedge bonding strength

Eleven groups of wire bonding experiments are carried out on an experiment platform (restructured with a U3000 heavy aluminum wedge wire bonder). Pure silicon aluminum wire (300 μm in diameter, 2.94～3.92 N in average pull force) and nickel coated aluminum substrates are used in the experiments. During the experiment process, only ultrasonic power rate parameter is changed and the other bonding parameters are kept as constant. The bonding force and time are 4.90 N and 100 ms respectively. After the bonding experiments, shear strength tests are carried out on the bonds as the bonding strength criterion. From those experiments and test results, some conclusions are obtained: In the small ultrasonic power rate conditions (about 20%～30%), with the power increasing, the bonding strength enhances accordingly; However, in the large ultrasonic power rate conditions (about 45%～70%), the bonding strength decreases accordingly and over bonding happens. Only when the ultrasonic power rate is in a moderate condition (about 35%～40%) can good and stabilized bonding strength be acquired.

Precipitation of γ′ phase and helium bubbles during proton and α-particle irradiation of nickel–silicon

Segregation of silicon was induced by light-ion irradiation at elevated temperatures in Ni–8Si specimens. Its occurrence at external surfaces, helium-induced cavities, dislocation loops, coherent twin boundaries, grain boundaries, and precipitate-matrix interfaces has been investigated by transmission electron microscopy. Layers of ordered γ′ (Ni3Si) phase were formed at most of these point defect sinks. The behaviour of grain boundary precipitation was found to be exceptional in various respects. In particular, a high rate of precipitation distinguishes grain boundaries from all other kinds of point defect sinks investigated here. This phenomenon of rapid precipitation was found to be adjoined to precipitation-driven grain boundary migration and is attributed to a radiation-induced “discontinuous” precipitate reaction. Observations of helium bubble distributions created during α-particle irradiations at growing dislocation loops and at migrating grain boundaries are also briefly discussed.

An Additive Micromolding Approach for the Development of Micromachined Ceramic Substrates for RF Applications

The selective removal of the substrate from under devices can help improve Q-factors, reduce losses and parasitics and can be applied to microwave components (transmission lines, spiral inductors, and capacitors) critical to high-frequency communications systems. A novel molding process has been developed to produce cavities in ceramic substrates over which gold transmission lines can be suspended. The "additive" method of fabricating cavities in ceramics was primarily based on the production of a substrate with preexisting cavities, as opposed to generation of cavities by the removal or the "subtraction" of material. The preexisting cavities were generated using a transfer mold technique based on photolithography, anisotropic silicon etching and nickel electroplating. The approach was demonstrated successfully using a commercial glass ceramic material (DuPont 951 Green Tape) to yield 100-/spl mu/m-deep cavities that showed shape retention and dimensional stability.

Fe—Ni—Si—Zn (Iron—Nickel—Silicon—Zinc)

AbstractFor Abstract see ChemInform Abstract in Full Text.

Nickel in silicon studied by electron paramagnetic resonance

We have investigated nickel in silicon samples with a wide range of initial doping concentrations by EPR, DLTS and photo-EPR techniques. Our results show that the two different Ni-centers which were observed previously by EPR, but whose structure could not be interpreted unambiguously, are both associated with Ni in a substitutional position. They are distinguished by their charges and by slightly different displacements from the ideal substitutional site. A model for the Ni+s-center is suggested which explains the symmetry of this center.

Fe‐—Ni—Si (Iron—Nickel—Silicon)

AbstractFor Abstract see ChemInform Abstract in Full Text.

Length-scale dependent variation of the first nucleated phase in nickel–silicon multilayers

We have studied the first phase nucleation behavior of a series of equiatomic Ni–Si multilayers with ultrathin repeating subunits (λ=1.7–5.8 nm) using x-ray reflectivity and x-ray diffraction. The variation in first nucleated phase is understood in terms of the model of Gösele and Tu, who predicted three length-scale dependent reaction routes in thin film diffusion couples: (i) For multilayers with λ>5.0 nm, interfacial nucleation of Ni2Si is observed, consistent with studies of bulk diffusion couples. (ii) For multilayers with 3.8<λ<5.0 nm, interfacial nucleation tends towards phases richer in Si due to a waning supply of Ni within the multilayer. (iii) For multilayers with λ<2.0 nm complete mixing of the Ni–Si multilayers prefigures first phase nucleation of NiSi. In this regime the composition of the first nucleation phase is determined by the amorphous precursor, which in turn is dictated by the relative ratios of Ni and Si in the initial multilayer. A fourth scenario, between (ii) and (iii), in which Ni2Si is the first nucleated phase is also observed. A possible mechanism for this unexpected result is discussed.

A galling-resistant substitute for silicon nickel

Silicon nickel, a cast nickel alloy containing about 3% silicon, had been used for threaded couplings in chemical delivery systems for over 40 years because it had necessary corrosion resistance and did not gall when mated with 316 and other stainless steels. In 2001, it was learned that this material was no longer available from long-time sources, and a laboratory study was undertaken to find a substitute alloy. Laboratory tests evaluated the threshold galling stress (using a modified ASTM G98 procedure) of six stainless steels against two titanium alloys and two proprietary alloys that allegedly (by their manufacturer) have good galling resistance. Silicon nickel was also tested as the material to “beat” in galling tests. The silicon nickel exhibited poor galling characteristics against all test counterfaces. Titanium with 6% A1 and 4% V showed good galling resistance against all counterfaces, but produced significant transfer to some counterfaces. One of the galling-resistant alloys exhibited good galling characteristics but transferred less. The galling-resistant alloy, which was essentially an austenitic stainless steel with increased nitrogen, silicon and manganese, was recommended as the substitute for the silicon nickel. It is thought that the silicon nickel worked in service because its porosity and silicide inclusions produced very high surface roughness in machining, and it was the porous, rough surface that provided its apparent galling resistance.

Tribological characteristics of nickel based composite coatings

Nickel composite coatings have been prepared on mild steel substrates by sediment electro-co-deposition (SECD) technique. Silicon nitride, fly ash and calcium fluoride are used as the reinforcements. Metallographic studies, microhardness, friction and wear tests under various loads and sliding speeds have been carried out on these coatings. Optical and scanning electron microscopy (SEM) studies on the worn surfaces were conducted. A theoretical model was used to predict the wear rates of the composite coatings. All the composite coatings exhibited a lower coefficient of friction and better wear resistance when compared with nickel coatings at all loads and sliding velocities studied. However, nickel–calcium fluoride composite coatings possessed the lowest coefficient of friction and wear rates. Significant effect of load and sliding speed on both the coefficient of friction and wear rates of nickel, nickel–silicon nitride and nickel–fly ash coatings has been observed. SEM studies of the worn surfaces reveal delamination process at higher loads. The predicted wear rates are in reasonable agreement with the experimental values.

Recombination current instability in epitaxial p +-n structures with impurity atoms locally incorporated into the n-type region and determination of the deep center parameters

The physical processes causing the recombination current instability in silicon epitaxial p+-n structures with a local contact formed in the n-type region of the structure and produced by incorporation of impurity atoms that introduced deep energy levels in the silicon band gap were studied. Based on the study of the current instability, the parameters (density, energy position, and cross section of electron capture) of deep-level centers generated by tin, lead, cadmium, and nickel in silicon, were determined.