Investigation of the magnetic characteristic of amorphous Fe40Ni40B20 and Fe6Co70Ni13Si7B4 foils by a magnetooptical method

Magnetic parameters, the local anisotropy field H_k, the effective field h related to the correlation radius, and the coercive force H_c, are determined for free and contact surfaces by investigating the magnetization curves of amorphous Fe₄₀Ni₄₀B₂₀ and Fe₆Co₇₀Ni₁₃Si₇B₄ foils by a highly-sensitive method of measuring the magnetooptical phase.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 49–52, November, 1989.     

Magnetostriction characteristics of the iron rich Fe-B-Si metallic glasses

Linear longitudinal and transverse magnetostriction and forced volume magnetostriction curves versus magnetic field for some as-quenched iron-rich amorphous alloys are presented. For the Fe₇₈Si₈B₁₄, Fe₇₈Si₉B₁₃ and Fe₇₉Si₁₂B₉ alloys the linear saturation magnetostriction was equal to 37·6×10^–6, 28·9×10^–8 and 34×10^–6, respectively.This work was in part financially supported by the Warsaw Technical University Institute of Material Science and Technology within the framework of the Project CPBR 2·4.     

Effects of high-temperature annealing on magnetic ordering in thin films of Bi2O3-CaO-Fe2O3

Magnetic properties of rf sputtered (0.5–x) Bi₂O₃-x CaO-0.5 Fe₂O₃ (x=0–0.5) have been studied through magnetization and ferromagnetic resonance (FMR) measurements. Films prepared in a mixed oxygen-argon atmosphere are amorphous and paramagnetic. Samples annealed in air at temperatures of 700–1000 K show a ferrimagnetic behavior even though X-ray diffraction data for the films do not indicate the precipitation of any crystalline ferrimagnetic compounds. The room-temperature saturation magnetization 4M and the uniaxial anisotropy field H _u , decrease with increasing x. The Curie temperature and the gyromagnetic ratio increase with increase in the concentration of CaO. Studies on the effects of sputtering atmospheres on magnetic parameters show that films sputtered in oxygen-rich atmospheres have a large 4M and H _u , and a relatively small and FMR line-width. Ordered amorphous clusters are suggested to give rise to the observed ferrimagnetic character in the annealed films.     

Si-nanostructures formation in amorphous silicon nitride SiNx:H deposited by remote PECVD

The formation of silicon nanoclusters embedded in amorphous silicon nitride (SiN_x:H) can be of great interest for optoelectronic devices such as solar cells. Here amorphous SiN_x:H layers have been deposited by remote microwave-assisted chemical vapor deposition at 300 °C substrate temperature and with different ammonia [NH₃]/silane [SiH₄] gas flow ratios (R=0.5−5). Post-thermal annealing was carried out at 700 °C during 30 min to form the silicon nanoclusters. The composition of the layers was determined by Rutherford back scattering (RBS) and elastic recoil detection analysis (ERDA). Fourier transform infrared spectroscopy (FTIR) showed that the densities of SiH (2160 cm⁻¹) and NH (3330 cm⁻¹) molecules are reduced after thermal annealing for SiN:H films deposited at flow gas ratio R>1.5. Breaking the SiH bonding provide Si atoms in excess in the bulk of the layer, which can nucleate and form Si nanostructures. The analysis of the photoluminescence (PL) spectra for different stoichiometric layers showed a strong dependence of the peak characteristics (position, intensity, etc.) on the gas flow ratio. On the other hand, transmission electron microscopy (TEM) analysis proves the presence of silicon nanoclusters embedded in the films deposited at a gas flow ratio of R=2 and annealed at 700 °C (30 min).     

Thermal stability and electrical properties of Zr silicate films for high-k gate-dielectric applications, as prepared by pulsed laser deposition

Zirconium silicate films with high thermal stability and good electrical properties have been prepared on n-Si(100) substrates and commercially available Pt-coated Si substrates to fabricate metal–insulator–metal (MIM) structures by the pulsed laser deposition (PLD) technique using a Zr_0.69Si_0.31O_2- ceramic target. Rapid thermal annealing (RTA) in N₂ was performed. X-ray diffraction indicated that the films annealed at 800 °C remained amorphous. Differential thermal analysis revealed that amorphous Zr silicate crystallized at 830 °C. X-ray photoelectron spectroscopy showed that RTA annealing of Zr silicate films at 900 °C led to phase separation. The dielectric constant has been determined to be about 18.6 at 1 MHz by measuring the Pt/Zr silicate/Pt MIM structure. The equivalent oxide thicknesses (EOTs) and the leakage-current densities of films with 6-nm physical thickness deposited in O₂ and N₂ ambient were investigated. An EOT of 1.65 nm and a leakage current of 31.4 mA/cm² at 1-V gate voltage for the films prepared in N₂ and RTA annealed in N₂ at 800 °C were obtained. An amorphous Zr-rich Zr silicate film fabricated by PLD looks to be a promising candidate for future high-k gate-dielectric applications. PACS 77.55.+f; 81.15.Fg; 73.40.Qv     

Diffusion of Au and Cu in amorphous Fe80B20 and Fe82B18 alloys

Diffusion rates (D) of Au in two amorphous alloys, Fe₈₀B₂₀ and Fe₈₂B₁₈, and of Cu in amorphous Fe₈₂B₁₈ alloy were measured in the temperature range 546–645 K by using the technique of Rutherford backscattering spectrometry (RBS) and Auger electron spectroscopy (AES), respectively. The diffusion of Au was found to be 3 to 6 times faster in Fe₈₀B₂₀ than in Fe₈₂B₁₈, though both the alloys had almost similar crystallization temperatures. The observed differences in the diffusion rates corroborate the fact that Fe₈₀B₂₀ has a more open structure than Fe₈₂B₁₈ as revealed from the reported values of the metal packing fractions of these two alloys. Also, the diffusivities of smaller sized Cu atoms (radius: 0.128 nm) were found to be higher by more than an order of magnitude than those of larger sized Au atoms (radius: 0.146 nm), suggesting a dependence ofD on the size of the diffusing species.     

Magnetic properties of Fe and Ni films evaporated in poor vacuum

To examine the pressure dependence of magnetic characteristics of Fe and Ni films, the films were prepared in vacuum ranging from 10^–5 to 10^–2 torr.Saturation magnetizationM _s ^* , perpendicular anisotropyK ^* and coercive forceH _c for Fe and Ni films deposited at around 10^–5 torr were in good agreement with the values obtained by others. When the film thickness was less than 500 ,M _s ^* for Fe films increased with pressure, while it decreased monotonically for Ni films. At pressures between 2×10^–3 and 10^–2 torr,M _s ^* decreased rapidly for Fe but it increased slightly for Ni. This interesting behaviour was most marked with film thickness of about 500 . Corresponding to the change inM _s ^* , bothK ^* andH _c also changed with deposition pressure.The result should be explained in terms of the presence of Fe₄N, Fe₈N and Ni₃N, as well as the macroscopic and microscopic structures of films.     

Radio-frequency induced effects in amorphous and nanocrystalline Fe73.5Cu1Nb3Si13.5B9

The rf collapse and sideband effects are used to study the microstructure of the Fe_73.5Cu₁Nb₃Si_13.5B₉ alloy in the amorphous and nanocrystalline state. Nanocrystalline grains of -Fe(Si) are formed as a result of annealing of the amorphous alloy at 520–570 °C. The results show that the complete rf collapse of magnetic hfs in the Mössbauer spectra occurs only in the amorphous phase. The rf collapse is strongly affected by the onset of the nanocrystalline phase and is suppressed when the Fe₃B and Fe₂B phases are formed. Partial collapse allows us to follow the remaining crystalline fractions during the crystalline process. The rf sidebands disappear due to the formation of nanocrystals because of the vanishing magnetostriction.     

ArF laser CVD of hydrogenated amorphous silicon: The role of buffer gases

ArF laser-induced CVD has been employed to generate hydrogenated amorphous silicon (a-Si:H) from Si₂H₆ gas dilute with He, Ar, or H₂. The formation of amorphous films or powder is found to depend critically on the kind of buffer gas, the stationary total and partial gas pressures, and the substrate temperature. These dependences have been investigated in the 1–5 Torr pressure and 100–400 °C temperature ranges. They are semiquantitatively discussed in terms of ArF laser photolysis of disilane, gas heating by heat flow from the substrate and laser irradiation, diffusion, and gas phase polymerization. Furthermore, photo ionization has been observed but found irrelevant for the a-Si:H layer properties. The photo and dark conductivities ( _ph, _d) of the semiconductor layers are determined by the substrate temperature. The _ph values range between 10^–7 and 10^{–4 –1} cm^–1 and the _d values between 10^–11 and 10^{–8 –1} cm^–1. The maximum ratio _ph/ _d amounts to 4×10⁴. The layers are further characterized by their optical band gap and activation energy. The layer properties are compared to literature values of amorphous films prepared by various photo, HOMO, and plasma CVD methods.     

Magnetic behavior of amorphous Sm-Co alloy films

Amorphous films of Sm_100–x Co _x with 70x90 were made by vapor deposition on flat glass substrates kept at 300 K. The films crystallize above 700 K. The film plane is the easy plane with the planar anisotropy of the order of 10⁷ erg cm^–3, indicating a local anisotropy of the order 10⁸ erg cm^–3. With regard to local anisotropy and magnetization, the films appear to correspond to the random anisotropy concept of amorphous magnets. Films evaporated in a magnetic field parallel to the film plane have an induced uniaxial anisotropy of the order of 10⁶ erg cm^–3. Hysteresis loops in fields parallel to the easy axis are perfectly rectangular with coercive fieldsH _c in the range 30 Oe<H _c<3000 Oe, depending on composition, temperature and heat treatment. The magnetization reverses by a thermally activated domain nucleation and growth process having a narrow distribution of time constants. Aging at temperatures below the crystallization temperature reduces the anisotropies andH _c.     

Dielectric constant and current transport for HfO2 thin films on ITO

The dielectric constant and leakage current mechanisms for HfO₂ thin films deposited on indium–tin–oxide using reactive rf sputtering deposition were examined. Indium–tin–oxide was selected as the bottom metal as it is of interest as an electrode in transparent field-effect transistor development. The dielectric constant of HfO₂ films was approximately 20 and did not vary significantly with deposition conditions. Temperature-dependent leakage current measurements indicate that Schottky emission is the dominant transport mechanism in films deposited at low temperature and/or low oxygen pressure. The HfO₂/indium–tin–oxide barrier height was extracted to be 1.1±0.2 eV. Films deposited at high temperature and/or oxygen pressure deviate from the Schottky emission model, presumably due to the formation of polycrystalline material with grain boundary conduction. PACS  73.61.Ng; 73.50.Lw; 77.55.+f     

The influence of hydrogen on the atomic distribution function and electrical resistance of amorphous chromium films

Electrical resistivity of amorphous chromium films (20–37 nm thick) deposited in a hydrogen atmosphere (P _{H 2}=8·10^–6–2·10^–4 hPa) onto a substrate cooled by liquid helium down to 2 K is measured, and electron-diffraction studies have been performed immediately after the quench condensation and after annealing to different temperatures up to 300 K. The preparation method employed permits a considerable hydrogen enrichment of the films to be reached. The maximum hydrogen concentration corresponds approximately to a stoichiometric composition of CrH. It is found that as the maximum concentration is approached the atomic distribution functionG(r) changes remarkably. The interatomic distances increase considerably (by 10%) and the atomic densities decrease. It is quite possible that amorphous chromium hydride is a final state with the maximum hydrogen concentration. For films with intermediate concentration,G(r) is found to vary substantially under annealing up to 90 K. The electron-diffraction and electronmicroscopic data, as well as the variations in resistivity due to annealing, suggest that with annealing up to 90 K, a hydrogen redistribution occurs in the amorphous films, initially homogenous in concentration. We observe also distinct indications of separation into phases with increased and reduced hydrogen contents.     

Correlation between the optical properties of surface layers and bulk characteristics of amorphous alloys

Spectral ellipsometry was used to study surface layers of Fe₈₀ A ₅B₁₅ (A = Ti, V, Cr, Mn, Fe, Co, Ni) and Fe_78-x Ni_xSi₉B₁₃ (x = 0, 1, 4, 8, 16, 21 at. %) amorphous metal alloys obtained by melt spinning. The optical characteristics of the alloys were determined by solving the inverse problem of ellipsometry. A correlation between the optical properties of the surface layers of amorphous alloys and their thermal stability was found.     

Crystallisation progress in Si-rich ultra-soft nanocomposite alloy fabricated by melt spinning

The crystallisation process and the ultras-soft magnetic properties of amorphous/nanocomposite alloy Fe_73.5Si_17.5B₅Nb₃Cu₁ fabricated by conventional melt-spinning technique are systematically investigated in terms of thermal analysis and in-situ measurement of magnetisation dynamics. The thermal analysis using differential scanning calorimetry showed that crystallisation from Fe-based amorphous state to α-Fe(Si) started at . Further heating the sample leads to a transformation from the α-Fe(Si) to Fe-B phases at . Crystallisation activation energies were determined using two models: Kissinger and John-Mehl-Avrami (JMA), which were consistent to each other with a value of . High resolution transmission electron microscopy investigation revealed an ultrafine structure of α-Fe(Si) nanocrystallite with mean size of 12.5 nm embedded in an amorphous matrix. At a volume fraction of 86% of α-Fe(Si) phase, optimum soft magnetic properties were obtained with very high permeability of 110,000 and a very low coercivity of 0.015 Oe by annealing the amorphous alloy at in 40 min.     

Thermal oxidation of n-type ZnN films made by -sputtering from a zinc nitride target, and their conversion into p-type films

Transparent p-type thin films, containing zinc oxide phases, have been fabricated from the oxidation of n-type zinc nitride films. The zinc nitride thin films were deposited by rf-magnetron sputtering from a zinc nitride target in pure N₂ and pure Ar plasma. Films deposited in Ar plasma were conductive (resistivity 4.7×10⁻² Ω cm and carrier concentrations around 10²⁰ cm⁻³) Zn-rich Zn_xN_y films of low transmittance, whereas Zn_xN_y films deposited in N₂ plasma showed high transmittance (>80%), but five orders of magnitude lower conductivity. Thermal oxidation up to 550 C converted all films into p-type materials, exhibiting high resistivity, 10²–10³ Ω cm, and carrier concentration around 10¹³ cm⁻³. However, upon oxidation, the Zn_xN_y films did not show the zinc oxide phase, whereas Zn-rich Zn_xN_y films were converted into films containing ZnO and ZnO₂ phases. All films exhibited transmittance >85% with a characteristic excitonic dip in the transmittance curve at 365 nm. Low temperature photoluminescence revealed the existence of exciton emissions at 3.36 and 3.305 eV for the p-type zinc oxide film.     

Severe plastic deformation of amorphous alloys: II. Magnetic properties

The influence of severe plastic deformation in a Bridgman cell on the magnetic properties of amorphous alloys of metal-metalloid type, Ni₄₄Fe₂₉Co₁₅Si₂B₁₀, Fe₇₄Si₁₃B₉Nb₃Cu₁, Fe_57.5Ni₂₅B_17.5, Fe_49.5Ni₃₃B_17.5, and Fe₇₀Cr₁₅B₁₅, obtained by melt spinning, has been investigated. It is found that the saturation magnetization significantly changes (increases or decreases), depending on the number of ferromagnetic and antiferromagnetic components in the alloy. It is suggested that very high shear stress causes internal phase decomposition in the amorphous matrix into nanoscale regions, enriched or depleted with ferromagnetic components.     

Ni83Cr7Fe3Si4B3非晶态合金在常压及高压下的晶化过程

本文研究了Ni₈₃Cr₇Fe₃Si₄B₃非晶态合金在1bar及100kbar压力下的晶化过程,得到了“时间-温度-变态”图。其结果表明:经高压热处理后的非晶合金其晶化温度降低,fcc-Ni相区域加宽及亚稳Ⅱ相没有形成。另外,还分别计算了常压及100kbar压力下的晶化激活能。 关键词：     

The hyperfine magnetic field of172Yb in Fe and Ni

Time-differential perturbed angular correlation measurements have been performed on the 91–1095 keV -ray cascade emitted by¹⁷²Yb nuclei in the capture decay of¹⁷²Lu, using implanted sources of¹⁷²Lu in Fe and Ni. From these measurements hyperfine field valuesB(YbFe)=–1253±83 kG andB(YbNi)=–143±12 kG follow at room temperature. From the modulation amplitude of the spectra it follows that only about 20% of the ytterbium nuclei participate in the precession.     

The formation of glassy alloys by irradiation with intense proton beams

Using a 50 ns pulse of an intense proton beam 1.5 J cm^–2 of energy was deposited in a 1 m thick surface layer of glass forming alloys. In Fe₈₀B₂₀, the formation of a glassy surface layer of 1.9 m thickness was observed by x-ray diffraction. Etching experiments performed with alloys containing phosphorus yielded similar results. Applying a mask technique amorphous and crystalline zones were structured with a resolution of better than 2 m.On leave from Central Electronics Engineering Research Institute, Pilani, Rajasthan, India     

Structure peculiarities of material formed by dynamic compacting of amorphous powders

Abstract

Structure and some properties of compacts dynamically produced from powders of Fe₈₂B₁₂Si₄C₂ and Co₅₉Ni₁₀Fe₅B_15.5Si_10.5 amorphous alloys are analyzed. The compacts of amorphous materials exhibit higher thermal stability as compared with that of starting powders.