Remagnetization of a circularly anisotropic amorphous wire in an alternating magnetic field

Remagnetization of an amorphous ferromagnetic wire with circular anisotropy in an alternating longitudinal magnetic field was theoretically studied within the framework of a quasistationary approximation. A frequency spectrum of the emf generated in a probing coil wound on the wire was determined, and analytical expressions describing the dependence of the emf amplitude on the alternating magnetic field amplitude H ₀ and the constant magnetic bias field value H _e were derived. The results can be applied to the development of weak magnetic field sensors.     

Compositional dependence of magnetoresistance in TbFeCo amorphous film

The dependence of Tb and Co concentration on the magnetoresistance (MR) of TbFeCo amorphous films with perpendicular magnetic anisotropy have been studied at room temperature. Tb/sub x/Fe/sub (88-x-y)/Co/sub y/ films (where x=15--37 at% and y=5--25 at%) with thickness of 200 nm are deposited by dc-magnetron sputtering. The MR ratio is sensitively dependent on the Tb concentration. The MR ratio is increased up to about 2.8% for a Tb concentration of about 22.4 at% then decreased for more Tb content. No significant effect of Co concentration on the MR ratio has been observed. The relation between MR ratio and film composition can be ascribed to the dependence of the domain wall width on the film concentration. The domain wall width decreases with an increase in Tb concentration and again increases for more Tb content showing its minimum value at about 22.4 at % of Tb concentration. It may be considered that the observed MR is contributed from the domain wall.     

玻璃包覆钴基非晶丝巨磁阻抗的长度效应

通过测量长度不同的玻璃包覆钴基非晶丝在频率为100kHz时的GMI值,近似计算出玻璃包覆钴基非晶丝的圆周磁导率.玻璃包覆钴基非晶丝圆周磁导率下降随着长度增加而变得剧烈,导致GMI变化更剧烈.利用玻璃包覆钴基非晶丝的磁畴模型,分析不同长度时玻璃包覆钴基非晶丝的磁化过程,合理解释了GMI效应随玻璃包覆钴基非晶丝长度增加而明显的现象.     

The frequency spectrum of a voltage measured in an amorphous wire magnetized in alternating magnetic field

We have studied the process of magnetization reversal in amorphous microwires under the action of a longitudinal (axial) high-frequency magnetic field. The amplitudes of harmonics in the frequency spectrum of the response voltage between the wire ends were measured as functions of the high-frequency field amplitude and a dc axial magnetic field strength. For relatively large amplitudes of the high-frequency field, the first several harmonics in the frequency spectrum of the response voltage are highly sensitive with respect to the dc magnetic field. The experimental results are interpreted within the framework of a simple electrodynamic model.     

On the temperature dependence of disturb properties in plated wire

Theory relating the temperature coefficient of the zero point and digit disturb threshold to the random anisotropy field is discussed. Certain assumptions about the relationship between the random anisotropy of ripple theory and the uniaxial anisotropy field yield relationships that predict the temperature sensitivity of these properties fairly well in Permalloy films. The temperature dependence of most disturb properties appears to be related to the temperature coefficient of the uniaxial anisotropy field from an experimental point of view. Several process variations that can affect the temperature coefficient of the uniaxial anisotropy field are considered.     

Temperature dependence of hydrogenated amorphous silicon thin-film transistors

The temperature dependence characteristics of hydrogenated amorphous silicon thin-film transistors were investigated. The results indicate that as the temperature was increased, the threshold voltage and the field-effect mobility were first increased, and then decreased, which may be controlled by different mechanisms at low and high temperatures. In addition, if the temperature was higher than 420 K, the Fermi level was promoted to the degenerate-like states, the current channel always existed due to the temperature effect, and the threshold voltage became negative.     

Stress induced crystallization of hydrogenated amorphous silicon

Hydrogenated amorphous silicon films were grown on to thermally oxidized silicon wafers by Radio Frequency magnetron sputtering, and SiN_x and Al₂O₃ capping layers were used to control the residual thermal stress. After annealing, a comparison of the silicon films with and without capping layers indicates that tensile stress induced by the capping layer enhances the crystallinity of the annealed amorphous silicon film. The stress is due to the mismatch between the coefficients of thermal expansion for the capping layer and amorphous silicon film. These results highlight the potential of thermal stress as a means to alter the crystallization in thin film architectures and suggest that even larger effects can be obtained with suitable choices of capping layer chemistry.     

Anomaly of the thickness dependence of photodarkening in amorphous chalcogenide films

The reversible photodarkening phenomenon in evaporated films of amorphous As-S and As-Se was investigated as a function of film thickness. For stoichiometric films irradiated by band gap illumination at room temperature, the photodarkening disappears when the films are thinner than 50 nm. This anomaly implies that the structure of the films is dependent on the film thickness and /or that the photodarkening exhibits a surface behaviour that is different from bulk bahaviour.     

Stress in hydrogenated amorphous silicon determined by X-ray diffraction

The residual strain in an a-Si:H layer has been directly determined with X-ray diffraction techniques from variations in the diffraction angle of the first amorphous peak using CuK radiation. The layer was deposited by HW-CVD on glass substrates at a growth temperature of 300 °C, and is known from previous studies to be highly disordered. It was found to have an average compressive stress of 750 MPa, using the c-Si lattice parameter as a reference, and typical values of the elastic constants for a-Si:H, increasing strongly towards the surface.     

Thermal annealing dependence of high-frequency magnetoimpedance in amorphous and nanocrystalline FeSiBCuNb ribbons

The magnetoimpedance (MI) effect in Fe73.5Si13.5B9Nb3Cu1 melt-spun amorphous ribbons has been studied in the frequency range (1-500 MHz). Isothermal heating treatments in a furnace have been employed to nanocrystallize the ribbons (1 h at 565 degrees C in a vacuum of 10(-3) mbar), while other samples were annealed at lower temperatures (400 and 475 degrees C during 1 h), in order to evaluate the influence of the annealing temperature on the MI effect. The high-frequency impedance was measured using a technique based on the reflection coefficient measurements of a specific transmission line by using a network analyzer. Frequency dependence of the MI ratio, DeltaZ/Z, and both resistive, DeltaR/R, and reactive, DeltaX/X, components of magnetoimpedance were measured in the amorphous and annealed states, at different temperatures. A maximum value of the MI ratio of about 50% at a driving frequency of 18 MHz is obtained in the nanocrystalline (annealed at 565 degrees C) ribbon. Maxima for DeltaR/R of about 81% at 85 MHz and DeltaX/X around 140% at 5 MHz were also achieved. It is revealed that the microstructural evolution in the nanocrystalline sample leads to a magnetic softening, an optimum domain structure and a permeability which is sensitive to frequency and applied magnetic field, generating a large MI response.     

芯片尺度封装中焊线的应力分析研究

芯片尺度封装(CSP)技术是近年来发展最为迅速的微电子封装新技术。通过对WB-CSP器件中金线(GoldWire)所受应力的有限元模拟,发现金线所受应力与塑封材料的膨胀系数、焊点大小、金线粗细、金线拱起高度等因素有关。结果表明:由于热失配引起的金线应力最大处位于金线根部位置,SEQVmax=625.202MPa,在通常情况下,这个部位在所承受的应力作用下产生的形变最大,最有可能发生断裂,引起器件的失效。模拟结果与实际失效情况相一致。此外,发现:当环氧树脂塑封料热膨胀系数为1.0×10-5/oC时,金线最大等效应力出现最小值,SEQVmax=113.723MPa,约为原来的1/6;随着金线半径减小、焊点增大,金线所受应力也将减小。模拟结果对于WB-CSP封装设计具有一定的指导意义。     

Temperature dependence of the magnetic properties of amorphous Co-Gd-Mo thin films

RF sputter deposited amorphous Co-Gd-Mo thin films have previously been shown to be potential materials for bubble device applications. However, the operation of a bubble device over a realistic temperature range requires materials with magnetic properties which are relatively temperature insensitive. An assessment of the temperature dependence of the magnetic properties of amorphous Co-Gd-Mo films is reported. The results of a mean field analysis of the magnetization data of Co-Gd-Mo thin films over wide composition and temperature ranges allowed optimization of the film composition for obtaining most suitable temperature dependences of magnetic properties. It has been found that even with the optimum compositions, the degree of temperature insensitivity improves with decreasing bubble diameters and is satisfactory only for sub-half-micron bubble materials. These results and analysis suggest that similar qualitative behavior may also be expected for other transition metal-rare earth alloys.     

非晶Ni-Mo-P化学镀层的应力和抗腐蚀性能

研究了非晶Ni-Mo-P沉积层的应力、成分及气孔率，它们对镀层在5％NaCl中的抗腐蚀性能的影响。同时研究了气孔、应力产生的原因。研究结果表明：在合适的Na2MoO4浓度及pH值下获得的非晶Ni-Mo-P沉积层具有最佳抗腐蚀性。随着镀液中Na2MoO4含量的增加，镀层应力很快从压应力向拉应力转变，镀层的气孔率增加。当Na2MoO4浓度大约为0．05g／L时，容易获得低孔隙率、低应力的非晶镀层。镀层气孔率，应力增加，镀层的耐蚀性显著降低。试样的长期腐蚀抵抗主要取决于镀层的应力．短期腐蚀抵抗则取决于镀层的气孔率。镀层具有低应力无气孔时，非晶镀层中Mo的含量越高，镀层在5％NaCl中的抗腐蚀性越好．而P含量的变化对镀层抗腐蚀性能无明显影响。镀层的应力采用X射线应力仪测定，并通过观察试样在5％HCl中浸泡25d后的外观进一步验证。采用浸泡腐蚀测试、硝酸变黑腐蚀测试、气孔率贴滤纸测试及电化学腐蚀测试技术对比研究了沉积层的腐蚀行为．     

Composition dependence of photo-induced refractive index changes in amorphous AsS films

Photo-induced refractive index changes in As_xS_100?x films were investigated as a function of composition in the range 15?x?45. The irreversible changes showed a maximum at x=40, which implies that the photopolymerization of As₄S₆ molecules plays a fundamental role. The reversible processes are roughly correlated with arsenic content. In the reversible processes, however, an annealing at the glass transition temperature of the bulk glasses does not produce an internal metastability in the evaporated chalcogenide-rich films. Anomalies at x ≈ 20 are observed in the irreversible and reversible changes. Speculations on these observations are presented.     

Structural whiteness of the multi-component glaze dependence on amorphous photonic crystals

A kind of enhancing mechanism of structural whiteness dependence on amorphous photonic crystal (APC) structure is introduced in this paper. In the glaze system composed of albite, kaolin, talc, calcite, quartz, titanium dioxide and zinc oxide, the APC structure will be produced by using quartz as a variable to induce the phase separation. Under different polarities between Ti, Zn etc. and Siion, the separated spheres with the core-shell structure can be obtained and then make up opal-like APCs in the glaze layer. In addition to inner and outer layers of core-shell spheres, the calculated results of refractive indices clearly show the great difference between the particles and the matrix. As a result of different refractive indices, the multiple scatting of visible light plays a key rote in the structural whiteness. However, due to the decrease of the cationic content, APCs with the reverse opal structure would be formed in the interface between glaze and body. Ultimately, the glaze appearance reveals extremely high structural whiteness due to the special APC structure.     

Stress formation and relaxation in amorphous Ta–Cr films

In the present paper, measurements of the intrinsic stress of thin amorphous Ta–Cr alloy films made by magnetron sputtering have been carried out. From the curvature of the substrates and by use of the Stoney formula, the stresses were determined. The bombardment of the growing film with energetic particles is shown to control the magnitude and sign of the intrinsic stress. When changing the deposition parameters, compressive or tensile stresses can be generated in the films in a range from about −2 GPa to +1 GPa. Also the stress relaxation, the change in the stress with time, has been studied for various temperatures. The stress relaxation was measured with a cantilever beam technique using a three-terminal capacitance method to detect the beam (substrate) deflection. The stress-relaxation data have been fitted to a mathematical model for stress relaxation related to inhomogeneous flow in amorphous films. This behaviour is expected to occur in the low-temperature, high-stress regime with deformation taking place along localized shear bands.