Effect of Magnetic Field on the Nanohardness of Monocrystalline Silicon and Its Mechanism

The effect of magnetic field on the nanohardness of monocrystalline silicon doped with phosphorous by ion implantation is studied. It is found that a magnetic field of certain parameters can increase the nanohardness of monocrystalline silicon doped with phosphorous by ion implantation, and this increase can be eliminated by annealing monocrystalline silicon doped with phosphorous by ion implantation at 800°C for 780 s. For the monocrystalline silicon doped with phosphorous by ion implantations that have not been exposed to a magnetic field, annealing them at 800°C for 780 s cannot affect their nanohardness, but exposing them to the magnetic field mentioned previously can no longer affect their nanohardness after annealing. The mechanism of all these phenomena is discussed. A possible mechanism that a magnetic field can promote the disbanding of vacancy clusters, and a possible mechanism of magnetically stimulated clusters’ disbanding and magnetoplastic effect are put forward.     

Comparative study of samples implanted at room temperature and below 1 K by NMR/ON and NO

²⁰⁶Bi was implanted into iron and nickel at T<0.2 K and room temperature. In all cases nuclear magnetic resonance of oriented²⁰⁶Bi was observed. Nuclear orientation data are compatible with nearly 100 per cent of the²⁰⁶Bi nuclei experiencing the hyperfine interaction corresponding to the resonance frequency but strength and shape of the resonance depend on the sample preparation which is discussed in detail. Nuclear orientation experiments with^122,124SbZn and²⁰⁶BiZn show a sizably smaller average quadrupole interaction frequency immediately after on-line implantation than after annealing at room temperature.     

The fabrication of nickel silicide ohmic contacts to n-type 6H-silicon carbide

This paper reports that the nickel silicide ohmic contacts to n-type 6H-SiC have been fabricated. Transfer length method test patterns with NiSi/SiC and NiSi硅化镍;欧姆触点;n型碳化硅;制造;能带;带隙Project supported by the National Basic Research Program of China (Grant No~2002CB311904), the National Defense Basic Research Program of China (Grant No~51327010101) and the National Natural Science Foundation of China (Grant No~60376001).2006-09-192006-10-30This paper reports that the nickel silicide ohmic contacts to n-type 6H-SiC have been fabricated. Transfer length method test patterns with NiSi/SiC and NiSi2/SiC structure axe formed on N-wells created by N^＋ ion implantation into Si-faced p-type 6H-SiC epilayer respectively. NiSi and NiSi2 films are prepared by annealing the Ni and Si films separately deposited. A two-step annealing technology is performed for decreasing of oxidation problems occurred during high temperature processes. The specific contact resistance Pc of NiSi contact to n-type 6H-SiC as low as 1.78× 10^-6Ωcm^2 is achieved after a two-step annealing at 350 ℃for 20 min and 950℃ for 3 min in N2. And 3.84×10-6Ωcm^2 for NiSi2 contact is achieved. The result for sheet resistance Rsh of the N＋ implanted layers is about 1210Ω/□. X-ray diffraction analysis shows the formation of nickel silicide phases at the metal/n-SiC interface after thermal annealing. The surfaces of the nickel silicide after thermal annealing are analysed by scanning electron microscope.     

Magnetoimpedance effect of current-annealed CoNiFe/Cu microtubes

A cobalt/nickel/iron (CoNiFe) magnetic layer was electrodeposited on a 50-μm-diameter non-magnetic Cu wire in a sulphate bath using a constant voltage. Electrodeposited CoNiFe composite wires were submitted to current annealing at 540 mA. It was found that annealing time less than 1 min removes internal stresses produced during fabrication and that annealing times longer than 5 min induce circumferential anisotropy. Non-annealed sample showed a magnetoimpedance (MI) ratio of 412%. A maximum MI ratio of 583% was obtained after 1 min of current annealing.     

Mössbauer spectroscopy effectiveness in investigating the influence of special heat treatments of metallic glasses

The as quenched amorphous ribbons are in a metastable condition and need a thermal treatment to relax internal stresses and/or to induce magnetic anisotropy. The evaluation of the results of various annealing treatments of the alloy Metglas 2826 was performed by magnetic measurements and Mossbauer spectroscopy, for the characterization of structural relaxation, easy magnetization axis changes and transition to crystalline order. Heat treatments considered include conventional (batch), laser and magnetic annealing (in transversal field).     

Thermal annealing effects in LiF crystals implanted with57Fe ions

Thermal annealing effects in lithium fluoride single crystals implanted with⁵⁷Fe ions were studied by conversion electron Mössbauer spectroscopy. It was found that annealing in vacuum leads mostly to the precipitation of metallic aggregates in contrast to the annealing in He and H₂ when the formation of ferric compounds, having high magnetic transition temperatures, takes place.     

Properties investigation of GaN films implanted by Sm ions under different implantation and annealing conditions

GaN films grown by MOCVD were implanted by Sm ions under different implantation and annealing conditions, in order to optimize the implantation parameters. The structural and magnetic measurements indicated a reduction of defect concentration and an increase of saturation magnetization when samples were implanted at 400°C, most probably due to the increased substitutional fraction of Sm ions. While the subsequent annealing process further decreased the damage in GaN lattice, but reduced the saturation magnetization on the contrary, caused by the decomposition of the surface layer and the formation of Sm-defect complexes during high-temperature annealing.     

Magnetic and electrical properties of oxygen stabilized nickel nanofibers prepared by the borohydride reduction method

Fine nickel fibers have been synthesized by chemical reduction of nickel ions in aqueous medium with sodium borohydride. The thermal stability and relevant properties of these fibers, as-prepared as well as air-annealed, have been investigated by structural, magnetic and electrical measurements. As-prepared samples appear to have a novel crystal structure due to the presence of interstitial oxygen. Upon annealing in air, the fcc-Ni phase emerges out initially and develops into a nanocomposite subsequently by retaining its fiber-like structure in nano phase. The as-prepared sample is observed to be weakly magnetic at room temperature, but attains surprisingly high magnetization values at low temperatures. This is attributed to the modified spin structure, presumably due to the presence of interstitial oxygen in the lattice. Development of a weakly ferromagnetic and electrically conducting phase upon annealing in air is attributed to the formation of the fcc-Ni phase. The structural phase transformations corroborate well with magnetic and electrical measurements.     

Damage studies on the system^{111} \mathop {In}\limits^ \to \underline {Ni}

Lattice damage after implantation of¹¹¹In in Ni has been studied applying the DPAC technique to the 171–245 keV -ray cascade in the daughter nucleus¹¹¹Cd. Implantations were carried out at 10 K and at 300 K. The low temperature implantation yields a higher regular substitutional fraction (80%) than the room temperature implantation (40%). The annealing behaviour of both implants above RT is the same. In addition, two distinct defect-associated sites were observed in isochronal annealing sequences. A microscopic model for these defects is presented, which takes into account magnetic and electric hyperfine interaction strengths, binding energies and site populations as a functions of temperature.     

Anisotropic ferromagnetism induced in rutile single crystals by Co implantation

The magnetic and electrical properties of Co-implanted single crystalline TiO₂ rutile are presented. For fluences of the order of 10¹⁷ cm^-2 and implantation energy of 150 keV the maximum atomic concentration of cobalt is 13 at% at a depth of 65 nm from the surface. The as implanted single crystals exhibit superparamagnetic behaviour attributed to the formation of nanosized cobalt clusters. After annealing at 1073 K an anisotropic ferromagnetic behaviour emerges with the easy magnetization axis lying in the (001) plane of rutile. The ferromagnetic behaviour is associated with oriented cobalt aggregates. Electrical conductivity of the implanted samples annealed in vacuum also exhibits anisotropic behaviour at low temperatures, but no magnetoresistive effects were detected.     

Influence of film morphology on thin film ferromagnetism

Cobalt, nickel and their alloy, Co₁Ni₉, films were epitaxially grown on Cu(100) under different growth conditions and subsequent treatments and studied using surface magneto-optic Kerr effect (SMOKE) in an attempt to understand the effects of film morphology on the magnetic properties. CO contamination can significantly reduce the magnetization and Curie temperature. Thermal desorption spectroscopy (TDS) shows that CO desorbs at 422 K from Ni and 410 K from Co₁Ni₉ at a heating rate of 6 K per minute. Annealing the films below 450 K produces smooth and clean films with stable magnetic behavior. However, annealing at higher temperatures results in Cu segregation and island formation leading to the finite-size ferromagnetic or even superparamagnetic behavior.     

Synthesis,structure stability and magnetic properties of nanocrystalline Ag–Ni alloy

Silver–nickel alloy nanoparticles with an average size of 30–40 nm were synthesized by chemically reducing the mixture of silver and nickel salts using sodium borohydride. The structure and the magnetic properties of the alloy samples with different compositions were investigated. The phase stability of the material was analysed after annealing the sample in vacuum at various temperatures. The material exhibits single fcc phase which is stable up to 400 °C and Ni precipitation sets in when the sample is annealed to 500 °C. The thermal analysis using DSC was carried out to confirm the same. The alloy compositions are found to be in close correlation with the metal salt ratios in the precursors. The synthesized samples exhibit weak paramagnetic to ferromagnetic behaviour. The magnetic measurements reveal that by adjusting the precursor ratio, the Ni content in the material can be altered and hence its magnetic properties tailored to suit specific requirements. The formation of Ag–Ni alloy is confirmed by the observed Curie temperature from the magneto thermogram. Annealing the sample helps to produce significant enhancement in the magnetization of the material.     

Rutherford backscattering study of crystal orientation dependent annealing effects in high-dose antimony implanted silicon

High dose implantations (10¹⁶ ions/cm²) of antimony in silicon result in concentrations far above the solid solubility of antimony in silicon. Rutherford backscattering was used to study the behaviour of damage and antimony concentration profiles for 〈100〉 and 〈111〉 substrates. The measurements were performed for various annealing treatments, implantation temperatures and implantation energies. A crystal orientation dependent outdiffusion of antimony towards the surface, a highly supersaturated phase of substitutional antimony at 600°C and a strong reverse annealing effect at higher temperatures were found.     

Ti离子注入和退火对ZnS薄膜结构和光学性质的影响

利用真空蒸发法在石英玻璃衬底上制备了ZnS薄膜,将能量80 keV,剂量1×10¹⁷ cm^-2的Ti离子注入到薄膜中,并将注入后的ZnS薄膜进行退火处理,退火温度500—700 ℃.利用X射线衍射（XRD）研究了薄膜结构的变化,利用光致发光（PL）和光吸收研究了薄膜光学性质的变化.XRD结果显示,衍射峰在500 ℃退火1 h后有一定程度的恢复;光吸收结果显示,离子注入后光吸收增强,随着退火温度的上升,光吸收逐渐降低,吸收边随着退火温度的提高发生蓝移;PL显示,薄 关键词： ZnS薄膜 离子注入 X射线衍射 光致发光     

Hyperfine interactions of111Cd in ion-implanted face centered cubic cobalt

The magnetic-dipole and electric-quadrupole hyperfine interactions of¹¹¹Cd probes in fcc cobalt after implantation of radioactive¹¹¹In⁺ ions have been investigated by PAC measurements with fast BaF₂ detectors. Six different sites of the probe atoms could be distinguished and characterized by their hyperfine parameters and annealing behaviour. Besides the substitutional site, three sites are assigned to In-vacancy complexes which are formed athermally in the implantation process or by thermally-activated trapping of lattice defects in annealing stage III. The remaining two sites are attributed to In located in stacking faults or hcp regions of the host. Systematic trends of impurity hyperfine fields in defect sites become evident from a comparison with other impurity-host combinations. The temperature dependence of the magnetic hyperfine fields has been measured between 20 K and 390 K. Large differences found for the various sites are discussed.     

Flash – lamp annealing of phosphorus and antimony implanted silicon

The structure and electrophysical properties of a silicon layers after P⁺ and Sb⁺ ion implantation and subsequent pulse annealing of millisecond lengths have been investigated by the transmission electron microscopy and four-point probe measurements. It has been demonstrated, that for certain implantation and annealing conditions the epitaxially grown layers can involve the microtwins and dislocation loops. The impurity redistribution under the pulse annealing depends on the implantation dose and rather weaker the light irradiation energy density.     

Dispersion of laser droplets using H+ ions and annealing effect on pulsed laser deposited nickel ferrite thin films

Nickel ferrite thin films were deposited by a pulsed laser deposition (PLD) technique on silicon substrate at room temperature in a vacuum of 5×10⁻⁵ mbar. The films were subjected to different annealing temperatures from 300–900°C and were also exposed to single shot energetic hydrogen ions using a Dense Plasma Focus (DPF) device. The changes induced in the films exposed at different distances from the top of the anode were investigated. The structural, morphological and magnetic properties of the annealed and exposed samples were investigated. X-ray diffraction (XRD) studies reveal the presence of a single phase of nickel ferrite after annealing. SEM micrographs indicate an increase in the grain size, both on annealing as well as on exposure to hydrogen ions. Annealing and hydrogen ion irradiation induced an enhancement in the magnetic moments. Laser droplets which are inherent in films deposited by laser ablation were found to be dispersed as a result of single shot hydrogen ion irradiation from the DPF.     

Effect of thermal annealing on spectral properties of electrodeposited carbon films

The effect of thermal annealing on properties of carbon films deposited on nickel electrodes by the electrodeposition method was studied. It has been shown that annealing at a temperature of 300°C results in the formation of nanosize diamond clusters. With an increase in the annealing temperature, the size of diamond clusters diminishes. At an annealing temperature of 900°C, all of the carbon enters into reaction with nickel, thus forming nickel carbide.     

Role of Chromium in the Formation of Phases in Mechanically Synthesized Alloys of Cementite Composition Alloyed with Chromium and Nickel

Phase transformations and aspects of alloying the phases of alloys of cementite composition, alloyed with chromium and nickel in the state immediately after mechanical synthesis and subsequent annealing, are studied. It is shown that cementite after mechanical synthesis is basically alloyed with chromium, while the amorphous phase is alloyed with chromium and nickel. Cementite produced upon the crystallization of the amorphous phase at T_ann = 300°C is enriched with nickel. At medium temperatures of annealing, the cementite regions with the highest nickel content decompose to form para- or ferromagnetic austenite.     

Superferromagnetic state of α-Fe in Fe implanted Co6Ag94 studied by Mössbauer spectroscopy

After having introduced by ion implantation ⁵⁷Fe to a local concentration of 7 at% into Co₆Ag₉₄, we observed it by conversion electron Mössbauer spectroscopy in the as-prepared state and after isochronal annealing. A superferromagnetic state is inferred, which is correlated with the ordering of the magnetic moments on the Fe clusters through chain-like or dendritic Co/Fe linear structures. The magnetic moment disordering temperature lies above 473 K.