Influence of magnetic annealing on high-frequency magnetic properties of FeCoNd films

FeCoNd thin film with thickness of 166 nm has been fabricated on silicon (1 1 1) substrates by magnetron co-sputtering and annealed for one hour under magnetic field at different temperatures (T_a) from 200 °C to 700 °C. The As-deposited and annealed FeCoNd film samples at T_a ≤ 500 °C were amorphous while the ones obtained at T_a ≥ 600 °C were crystallized. We found that the perpendicular anisotropy field gradually decreases as the annealing temperature increases from room temperature to 300 °C. A well induced in-plane uniaxial anisotropy is achieved at the annealing temperature between 400 and 600 °C. The variation of the dynamic magnetic properties of annealed FeCoNd films can be well explained by the Landau-Lifshitz equation with the variation of the anisotropy field re-distribution and the damping constant upon magnetic annealing. The magnetic annealing might be a powerful post treatment method for high frequency application of magnetic thin films.     

Magnetic properties and microstructures of sputtered epitaxial Co-rich Co-Pt films

Co₃Pt films of various thicknesses were deposited on Pt underlayers by conventional sputtering in order to investigate the effects of Pt underlayers and annealing temperatures on their microstructure and the magnetic properties. XRD and HRTEM analyses reveal perpendicular magnetic anisotropy in films of good epitaxial growth of Co₃Pt (002) on the Pt (111) underlayer when annealed at 300 °C. However, Pt atoms in the Pt underlayer will diffuse seriously into the Co₃Pt layer when the annealing temperature is increased to 375 °C. This changes the compositions to approach equiatomic CoPt, and shows in-plane magnetic anisotropy with soft magnetic properties.     

Microstructure and electrical properties of Al2O3-ZrO2 composite films for gate dielectric applications

Al₂O₃-ZrO₂ composite films were fabricated on Si by ultrahigh vacuum electron-beam coevaporation. The crystallization temperature, surface morphology, structural characteristics and electrical properties of the annealed films are investigated. Our results indicate that the amorphous and mixed structure is maintained up to an annealing temperature of 900 °C, which is much higher than that of pure ZrO₂ film, and the interfacial oxide layer thickness does not increase after annealing at 900 °C. However, a portion of the Al₂O₃-ZrO₂ film becomes polycrystalline after 1000 °C annealing and interfacial broadening is observed. Possible explanations are given to explain our observations. A dielectric constant of 20.1 is calculated from the 900 °C-annealed ZrO₂-Al₂O₃ film based on high-frequency capacitance-voltage measurements. This dielectric characteristic shows an equivalent oxide thickness (EOT) as low as 1.94 nm. An extremely low leakage current density of ∼2×10⁻⁷ A/cm² at a gate voltage of 1 V and low interface state density are also observed in the dielectric film.     

Si1 − xGex metal-oxide-semiconductor capacitors with HfTaOx gate dielectrics

Interfacial reactions and electrical properties of RF sputter deposited HfTaO_x high-k gate dielectric films on Si_1 − xGe_x (x = 19%) are investigated. X-ray photoelectron spectroscopic analyses indicate an interfacial layer containing GeO_x, Hf silicate, SiO_x (layer of Hf-Si-Ge-O) formation during deposition of HfTaO_x. No evidence of Ta-silicate or Ta incorporation was found at the interface. The crystallization temperature of HfTaO_x film is found to increase significantly after annealing beyond 500 °C (for 5 min) along with the incorporation of Ta. HfTaO_x films (with 18% Ta) remain amorphous up to about 500 °C anneal. Electrical characterization of post deposition annealed (in oxygen at 600 °C) samples showed; capacitance equivalent thickness of ~ 4.3-5.7 nm, hysteresis of 0.5-0.8 V, and interface state density = 1.2-3.8 × 10¹² cm^− 2 eV^− 1. The valence and conduction band offsets were determined from X-ray photoelectron spectroscopy spectra after careful analyses of the experimental data and removal of binding energy shift induced by differential charging phenomena occurring during X-ray photoelectron spectroscopic measurements. The valence and conduction band offsets were found to be 2.45 ± 0.05 and 2.31 ± 0.05 eV, respectively, and a band gap of 5.8 ± 05 eV was found for annealed samples.     

Atomic Vapor Depositions of Ti-Ta-O thin films for Metal-Insulator-Metal applications

Atomic Vapor Deposition technique was applied for the depositions of Ti-Ta-O oxide films for Metal-Insulator-Metal capacitors used in back-end of line for Radio Frequency applications. Composition, crystallinity, thermal stability and electrical properties were studied. Ti-Ta-O films, with the ratio of Ta/Ti ~ 1.5, deposited at 400 °C on TiN electrodes, were amorphous and possessed a dielectric constant of 50 with low voltage linearity coefficients and leakage currents densities as low as 10^− 7 A/cm² at 1 V. The films, deposited on Si wafers, were amorphous up to the annealing temperature of 700 °C and crystallized in orthorhombic Ta₂O₅ phase at higher temperatures.     

Deposition and microhardness of SiC from the Si2Cl6-C3H8-H2-Ar system

We obtained SiC coating layers on a graphite substrate using hexachlorodisilane (Si₂Cl₆, boiling point 144° C) as a silicon source and propane as a carbon source. We examined the deposition conditions, contents of carbon, silicon and chlorine in the deposits, and the microhardness. Mirror-like amorphous silicon layers were deposited in the reaction temperature range 500 to 630° C. well-formed silicon carbide layers with good adherency to the substrate were obtained above 850° C. The lowest deposition temperature of SiC was estimated to be 750 to 800° C. The Vickers microhardness of the SiC layer was about 3800 kg mm^–2 at room temperature and 2150 kg mm^–2 at 1000° C.     

Nanocomposite magnetic films for high-density perpendicular magnetic recording media

Multi-layer nanocomposite structures of Ta/Ru/CoCr₁/FeCoTaCr(soft magnetic layer)/CoCr₂/CoCrPt-SiO₂(hard magnetic layer or recording layer)/C and Ta/Ru/CoCr₁/CoCrPt-SiO₂/CoCr₂/FeCoTaCr/C were proposed. This exchange coupled composite (ECC) media consisting of hard/soft stacked magnetic layers were promising in improving the writability of perpendicular magnetic recording media. A small CoCrPt c-axis orientation dispersion of about 3° was achieved with the optimized sputter conditions. The CoCrPt-SiO₂ grains were well segregated by SiO₂ at grain boundaries. The macro-magnetic properties showed that the stacked magnetic grains switched in a coherent mode and that switching field decreased with increasing the thickness of the soft magnetic layer.     

Characterization of (Pb,La) TiO3 thin films prepared by the sol-gel method

Pb_(1–1.5x)La_xTiO₃ thin films were synthesized by the sol-gel spin-coating technique. The films became crystallized when the spin-coated films were annealed at 600 °C and at higher temperature, and became amorphous when annealed at 550 °C. The breakdown voltage, V _B, was recorded at around 30 V for 600–650 °C annealed films and varied only slightly with the composition. The V _B value of the amorphous films was observed to be higher than that of the crystalline films. The ferroelectric properties of both the amorphous and crystalline films were found to be similar. The dielectric constant, charge storage density and optical index of refraction of the films were _r =5–20, Q _c=0.12–0.54 C cm^–2 and n=1.6–2.3, respectively. They all increased moderately with La³⁺ content in the films. One possible reason why the ferroelectric properties are not modified as the amorphous films crystallize, may be that the octahedra are equilateral, whether the films are amorphous or crystalline. Additionally, a possible cause which lowers the breakdown voltage in crystalline film, is the formation of lead vacancies due to lead loss. The electrical properties of films coated on bare silicon become significantly lowered due to interdiffusion between films and substrate. The diffusion of Si⁴⁺ ions into-the films can be prevented by coating SrTiO₃ on the silicon substrate as a buffer layer. The charge storage capacity consequently becomes substantially enhanced.     

Characterisation of amorphous silica in air-oxidised Ti3SiC2 at 500–1000 °C using secondary-ion mass spectrometry,nuclear magnetic resonance and transmission electron microscopy

In this paper we have described the use of secondary-ion mass spectrometry (SIMS), solid state ²⁹Si magic-angle-spinning (MAS) nuclear magnetic resonance (NMR) and transmission electron microscopy (TEM) to detect the existence of amorphous silica in Ti₃SiC₂ oxidised at 500–1000 °C. The formation of amorphous SiO₂ and growth of crystalline TiO₂ with temperature was monitored using dynamic SIMS and synchrotron radiation diffraction. A duplex structure with an outer TiO₂-rich layer and an inner mixed layer of SiO₂ and TiO₂ was observed. Results of NMR and TEM verified for the first time the direct evidence of amorphous silica formation during the oxidation of Ti₃SiC₂ at the temperature range 500–1000 °C.     

Temperature dependence of the microstructure and resistivity of indium zinc oxide films deposited by direct current magnetron reactive sputtering

Indium zinc oxide (IZO) films were deposited as a function of the deposition temperature using a sintered indium zinc oxide target (In₂O₃:ZnO = 90:10 wt.%) by direct current (DC) magnetron reactive sputtering method. The influence of the substrate temperature on the microstructure, surface roughness and electrical properties was studied. With increasing the temperature up to 200 °C, the characteristic properties of amorphous IZO films were improved and the specific resistivity was about 3.4 × 10^− 4 Ω cm. Change of structural properties according to the deposition temperature was also observed with X-ray diffraction patterns, transmission electron microscopy, X-ray photoelectron spectroscopy, and atomic force microscopy. IZO films deposited above 300 °C showed polycrystalline phases evolved on the amorphous IZO layer. Very flat surface roughness could be obtained at lower than 200 °C of the substrate temperature, while surface roughness of the films was increased due to the formation of grains over 300 °C. Consequently, high quality IZO films could be prepared by DC magnetron sputtering with O₂/Ar of 0.03 and deposition temperature in range of 150-200 °C; a specific resistivity of 3.4 × 10^− 4 Ω cm, and the values of peak to valley roughness and root-mean-square roughness are less than 4 nm and 0.5 nm, respectively.     

Effects of preparation conditions on the magnetic anisotropy of amorphous Fe78B13Si9 alloy

The in-plane magnetic anisotropy of amorphous Fe₇₈B₁₃Si₉ alloy prepared under various forming conditions was investigated. The anisotropy of circular discs was measured using the torque method. The experimental results indicate that the degree of magnetic anisotropy decreases, as does the depth of the surface grooves on the roller side, with the increase of the cooling rate or the melt temperature before jet casting. This shows that the directional surface irregularities are a principal reason for the in-plane anisotropy of the amorphous Fe₇₈B₁₃Si₉ ribbons. The results also indicate that the value of the anisotropy constant is about 10⁴ erg cm⁻³ and that the easy direction coincides with the longitudinal direction (of the amorphous Fe₇₈B₁₃Si₉ alloy). At the same time, the effects of the distribution of stress aligned predominantly along one direction and of the directional structural units or defects on the magnetic anisotropy are discussed.     

Study on microstructure and magnetic domain structure in sputtered (Ni66Fe22Co12) x C1−x nanocomposite films

Composition and annealing temperature dependence of microstructure and magnetic domain structure in sputtered (Ni₆₆Fe₂₂Co₁₂) _x C_1–x nanocomposite films with x=10–75 at % were studied by X-ray diffraction and magnetic force microscopy (MFM). Films with x20 at % showed amorphous structures, and no domain structure could be found due to the disappearance of magnetocrystalline anisotropy. For the films with x=30–55 at %, face-centered cubic (fcc) NiFeCo nanocrystals encapsulated in graphite-like carbon could be found in the samples annealed beyond 400 °C, and stripe domains with typical dimension of 120–150 nm were observed. For the films with x62 at %, the as-deposited films went through a meta-stable stage at which a rhombohedral Ni₃C phase and fcc NiFeCo co-existed after annealing to a temperature between about 300–400 °C (dependent on composition). Upon further annealing to a sufficiently high temperature between about 350–500 °C, the carbide phase decomposed into fcc NiFeCo and graphite. While short-range domain structures were observed in the samples before the formation of carbide phase, long-range domain structure with dispersed domains in the meta-stable stage were observed. After the decomposition of carbide, large domains with typical size of 500–700 nm were observed due to the formation of large grain aggregators.     

Influence of the calcining temperature on the sintering and properties of PZT ceramics

Niobia-doped PZT powders were prepared by both hydroxide and oxalate coprecipitation methods. The resulting amorphous powders were calcined at two different temperatures (550 and 700 °C) and the morphology and size of the calcined particles were studied. It was found that hydroxide powders, when calcined at 700 °C, gave 98% theoretical density,d _th, bodies at a sintering temperature as low as 1100°C in air. The high agglomeration present in oxalate powders strongly retarded densification. Of the piezoelectric properties, ak _p higher than 60% and ad ₃₃ constant of 360 × 10^–12 CN^–1 were measured. Dielectric parametersT _c andk _3T, 310° C and 1100, respectively, were determined.     

Improving the Bs and soft magnetic properties of Fe-based amorphous ribbons by manipulating the surface crystallization behavior

A novel amorphous structure coupling with ultra-fine nano α-Fe grains in the surface crystallization layer was fabricated successfully through composition regulation and proper quenching conditions. The microstructure of the newly formed surface crystallization layer and its effects on soft magnetic properties of FeMnCuMoCPSiB amorphous alloy were investigated systematically. The FeMnCuMoCPSiB amorphous alloy with surface α-Fe crystallization layers exhibits an excellent comprehensive performance of soft magnetic properties (SMPs) with high B_s of 1.67 T, low H_c of 1.6 A/m, and high μ_i of 9.3?×?10³ at 1 kHz. The SMPs of the amorphous alloy is considerably superior to that of widely used commercial soft magnetic materials METGLAS 2605, promising a potential engineering application. It is noteworthy that a nanoscale surface precipitation was found in the alloy, which favors SMPs of the alloy.

     

Low temperature ordering of FePt films by in-situ heating deposition plus post deposition annealing

FePt thin films with 40 nm thickness were prepared on thermally oxidized Si (001) substrates by dc magnetron sputtering at the nominal growth temperature 375 °C. The effects of annealing on microstructure and magnetic properties of FePt thin films were investigated. The as-deposited FePt thin films show soft magnetic properties. After the as-deposited FePt thin films were annealed at various temperatures and furnace cooled, it is found that the ordering temperature of L1₀ FePt phase could be reduced to 350 °C. For FePt thin films annealed at 350 °C, the in-plane and out-of-plane coercivities of the films increased to 510 and 543 kA/m, respectively, and the films had hard magnetic properties. A highly (001) orientation was obtained, when FePt thin films were annealed at 600 °C. And the hysteresis loops of FePt thin films annealed at 600 °C show out-of-plane magnetic anisotropy.     

Synthesis and photoluminescence properties of CaSiO3:Eu spheres prepared by the reverse micelles soft template

We report here the successful synthesis of CaSiO₃:Eu³⁺ spheres using the reverse micelles soft template. The influence of the calcination temperature on the shape, crystallization and photoluminescence properties of the prepared spheres was investigated by DTA-TG, XRD, IR, SEM and PL. The results showed that the temperature of crystallization (from amorphous phase to β-CaSiO₃) is 668 °C. The temperature of phase transition (from β-CaSiO₃ to α-CaSiO₃) is 790 °C. The average size of CaSiO₃:Eu³⁺ spheres calcined at 700 °C was about 350 nm. The radiation was dominated by the red emission peak at 613 nm and the highest emission intensity was observed when the spheres were calcined at 700 °C. When calcined at 800 °C, the spheres are almost cracked and melted down, due to the high temperature.     

Self-assembled nano-size FePt islands for ultra-high density magnetic recording media

To find a method to form nano-size FePt alloy for ultra-high density magnetic recording media, this work concentrated on the formation mechanisms of nano-island FePt films on amorphous glass substrates. FePt films of different thicknesses (1-10 nm) were deposited on amorphous glass substrates and post-annealed at 700 °C for 10 and 30 min. The configuration of the film changed during the annealing process due to the surface energy difference between the glass substrate and FePt alloy. Investigation of the microstructures and magnetic properties of the ordered L1₀ FePt films revealed that the 1 nm FePt film annealed at 700 °C for 10 min had perpendicular magnetic anisotropy and good reproducibility of forming well-separated FePt nano-size islands for ultra-high density magnetic recording media.     

Structural and electrical properties of sputtered indium-zinc oxide thin films

In this study, indium-zinc oxide (IZO) thin films have been prepared at a room temperature, 200 and 300 °C by radio frequency magnetron sputtering from a In₂O₃-12 wt.% ZnO sintered ceramic target, and their dependence of electrical and structural properties on the oxygen content in sputter gas, the substrate temperature and the post-heat treatment was investigated. X-ray diffraction measurements showed that amorphous IZO films were formed at room temperature (RT) regardless of oxygen content in sputter gas, and micro-crystalline and In₂O₃-oriented crystalline films were obtained at 200 and 300 °C, respectively. From the analysis on the electrical and the structural properties of annealed IZO films under Ar atmosphere at 200, 300, 400 and 500 °C, it was shown that oxygen content in sputter gas is a critical parameter that determines the local structure of amorphous IZO film, stability of amorphous phase as well as its eventual crystalline structure, which again decide the electrical properties of the IZO films. As-prepared amorphous IZO film deposited at RT gave specific resistivity as low as 4.48 × 10^− 4 Ω cm, and the highest mobility value amounting to 47 cm²/V s was obtained from amorphous IZO film which was deposited in 0.5% oxygen content in sputter gas and subsequently annealed at 400 °C in Ar atmosphere.     

Post deposition annealing of aluminum oxide deposited by atomic layer deposition using tris(diethylamino)aluminum and water vapor on Si(100)

Thin stoichiometric aluminum oxide films were deposited using tris(diethylamino)aluminum precursor and water. Changes in aluminum oxide film and interfacial regions were studied after post deposition annealing under inert ambience at 600, 800 and 1000 °C using Fourier Transform InfraRed (FTIR) spectroscopy, X-ray Photoelectron Spectroscopy, and Scanning Transmission Electron Microscopy (STEM)/Electron Energy Loss spectroscopy (EELS) techniques. STEM/EELS analyses were also done on samples annealed in situ, i.e., inside the electron microscope at temperatures as high as 800 °C. Up to an annealing temperature of 600 °C, the atomic layer deposited alumina film was thermally stable and remained amorphous with no interfacial silica growth observed. After annealing at 800 °C for 5 min, the only change observed was a small increase in the interfacial layer thickness which was found to be mainly silicon oxide without any significant silicate content. Annealing at 1000 °C induced a significant increase in the interfacial layer thickness which consisted of a mixture of silicon oxide and aluminum silicate. The composition of the interfacial layer was found to change with depth, with silicate concentration decreasing with distance from the Si substrate. Also, the FTIR spectra exhibited strong absorption features due to Al-O stretching in condensed AlO₆ octahedra which indicate crystallization of the alumina film after annealing at 1000 °C for 5 min.     

Chemical vapour deposition of tantalum diboride

Tantalum diboride (TaB₂) was deposited on a quartz substrate from a gas mixture of TaCl₅, BCl₃, H₂, and Ar at a temperature between 900 and 1300° C. When the atomic ratio (B/Ta) in source gas was held above 1.0 at 1000° C, TaB₂ with a composition of between TaB_1.90 and TaB_1.95 was obtained in a single phase. The deposits grew to grain crystals with an increase in temperature and with an increase in the atomic ratio (B/Ta) in the source gas. The mass transfer of TaCl₅ was supposed to be the rate-determining step. The Vickers microhardness values for the coating deposited at 1100° C from a source gas with atomic ratio (B/Ta) above 1.0 were 3500 to 4100 kg mm^–2. Dispersing Ni or Pd on the substrate as an impurity, woolly crystals of up to 100m in length were grown in 30 min at 1050° C, and the growth mechanism was thought to be that of tip-VLS.