Propagation properties of ferromagnetic insulator guide

In order to realize new ferrite planar devices for applications at millimeter-wavelength frequencies, the authors have developed nonreciprocal ferrite devices schemes for incorporating ferromagnetic layers in dielectric insulator guide geometries. Their research program involves both the calculation and the measurement of device characteristics. For the calculation, a method of effective permeability, in which the permeability is a tensor, is introduced to characterize the ferrite material. The propagation properties of the insular guide are calculated by using a single-mode approach. The calculated results for dispersion, dielectric, and conductivity losses show resonant behavior with the application of a magnetic bias field for a guide configuration in which the ferrite replaces the insular dielectric. Ferrite phase shifters, filters, isolators, and circulators are potential applications of this guide configuration. For the experimental part of the study, wave dispersion and attenuation were measured in a purely dielectric insular guide from 26.5 to 40GHz. In addition to these experiments wave attenuation was measured as a function of magnetic bias field for the case where a hexagonal ferrite platelet was mounted on the ground plane near the insulator guide. General agreement is found between calculated and measured attenuation     

炭基/锌掺杂铁磁体复合材料制备及其消光性能研究

为了实现抗红外烟幕高效环保的要求,同时实现质轻、宽波段吸波性能,采用一步水热法制备了炭基-锰锌铁氧体/镍锌铁氧体/钴锌铁氧体复合材料的前驱体,并在500~900 ℃的温度区间进行焙烧得到了炭基/锌掺杂铁磁体复合材料。通过X射线粉末衍射仪（XRD）、傅里叶红外光谱仪（FT-IR）、扫描电子显微镜（SEM）等表征方法,分析了复合材料的物相和形貌。根据朗伯比尔定律,采用傅里叶红外光谱仪的KBr压片法测试并计算了各材料在2.5~25 μm区间的红外消光系数,并且研究了焙烧温度对材料消光性能的影响。研究结果表明:炭基/锌掺杂铁氧体前驱体焙烧后生成的炭基/锌掺杂铁磁体复合材料的红外消光性能均有所增强,经过700 ℃焙烧后的炭/钴锌铁磁体红外消光系数最大,为0.25 m2/g,具有较好的红外消光性能。     

热处理时间对铁磁性微晶玻璃磁性能的影响

以Fe2O3-CaO-SiO2-B2O3-P2O5系统为基础,采用基础玻璃析晶法制备铁磁性微晶玻璃热种子材料。通过XRD,确定了热处理样品中的主晶相为磁铁矿、硅灰石和赤铁矿;采用振动样品磁强计(VSM),测试样品室温下的磁性能;通过SEM,观察样品中晶体的形貌。研究了热处理时间对其磁性能的影响。结果表明:合理的热处理时间为2h,制得的铁磁性微晶玻璃的比饱和磁矩为26.2A·m2·kg–1。     

The properties of some metal-InSb surface barrier diodes

Metal-semiconductor surface barriers were formed by the vacuum evaporation of Au, Ag and Al onto n-type InSb. The current and capacitance curves of these devices were measured as a function of voltage at 77°K and analyzed in terms of existing theory. Surfaces etched in CP-4A followed by H100 and rinsed in 10^?5 M Na₂S formed inversion layers. Omission of the H100 step led to the formation of Schottky-type barriers.     

Microstructure and barrier properties of reactively sputtered Ti-W nitride

The materials properties of Ti-W, sputter deposited in pure Ar, and Ti-W-N deposited in Ar-N₂ mixtures containing up to 50% N₂ have been reported. Films with N contents between 0 and 45 at.% have been produced. The W/Ti ratio in the nitrided alloy has been varied from that corresponding to pure W, to that of pure Ti. The metastable ter-nary phase diagram Ti-W-N was composed from data presented in this paper and lit-erature data. For low N contents (up to about 20 at.%) the film consists of a metastable solid solution of N in bcc Ti-W. For high N contents (from about 35 to 45 at.%). We observed the film to consist of an fcc ternary Ti-W nitride. The barrier performance was evaluated in an Al-Cu metallization to TiSi₂/Si contacts by Auger electron spectroscopy and junction leakage measurements. In clean sputtering environments, we need to cre-ate the ternary nitride to form a reliable barrier. Adding some N to “stuff” the grain boundaries of the bcc phase, or contaminating the Ti-W surface by an exposure to at-mosphere, was found to be less effective in producing a reliable barrier.     

Investigation of the properties of ferromagnetic ZnO:Cr2O3 nanocomposites

Present work focuses on the structural, optical and magnetic properties of ZnO:Cr₂O₃ nanocomposites. ZnO nanoparticles were synthesized and the structure was confirmed using powder x-ray diffraction. ZnO nanoparticles was grown in the hexagonal wurtzite structure with the preferential orientation along (101) plane. ZnO:Cr₂O₃ composites have been synthesized by doping different concentration of Cr₂O₃ (1, 3 and 5 wt%) into ZnO. The incorporation of Cr₂O₃ was confirmed using Fourier transformed infrared spectroscopy. UV–visible absorption spectra have been observed and interpreted for the determination of optical constants of ZnO:Cr₂O₃ composites. The optical constants like optical band gap, refractive index were determined and the effect of Cr₂O₃ on these constants was investigated. Relation between optical band gap and the refractive index were obtained. Magnetic studies using vibrating sample magnetometer reveal the ferromagnetism at 150 K in the composites with 3 and 5 wt% of Cr₂O₃.     

Microscopic barrier properties in electron-beam scribed YBCO Josephson junctions

We present an analysis of the microscopic properties of the Josephson barrier in electron-beam junctions scribed at low temperatures in YBa₂Cu₃O₇. These junctions behave as high-quality, uniform super-normal-superconductor (SNS) junctions which allows their characteristics to be compared in detail to well-established SNS theory. Combining this data with a Boltzmann transport model of the irradiated region, and treating the oxygen-sublattice defects as pair-breaking, allows quantification of the interlayer’s microscopic properties such as normal coherence length, quasiparticle mean-free path, and resistivity. We find that the barrier exhibits properties of a dirty metal near the metal–insulator transition, with a Fermi surface area reduced an order of magnitude from that of the unirradiated film. In addition, we analyze the limiting normal properties of irradiated YBCO, showing that the normal coherence length at the original transition temperature is constrained to less than twice the zero-temperature superconducting coherence length of the original film. This analysis applies in general to weak-link structures in which the barrier is created from the electrode material through weakening by a pair-breaking mechanism.     

Breakdown and capacitance properties of hyperabrupt epitaxial Schottky barrier diodes

An analysis of the breakdown and capacitance properties of punch-through hyperabrupt epitaxial Schottky barrier diodes has been carried out. Results are given for the dependence of breakdown voltage of such a device on surface concentration and epitaxial layer thickness. Design curves are given for epitaxial hyperabrupt schottky varactor diodes. The design procedure yields an optimal impurity profile in which just-punch-through occurs at the highest voltage of operation. This gives a maximum dynamic range of operation still keeping the series resistance to a minimum. A corrected boundary condition to determine the profile constants associated with an n/n⁺ (high/low) junction is also given.     

Non-ideal Schottky barrier model for impedance measurements of materials properties

Theory of a non-ideal Schottky barrier biased by dc voltage with a small ac signal is presented. Theoretical considerations based on general transport equations enabled to derive a formula on structure impedance.     

Optical and barrier properties of thin-film encapsulations for transparent OLEDs

We investigate the optical and barrier properties of thin-film encapsulations (TFEs) for transparent organic light-emitting diodes (TOLEDs). To improve the barrier property of OLEDs, the number of dyads (Al₂O₃/polymer) and the thickness of polymer layer in the TFE structure are required to be increased. It is, however, demonstrated that a sharp dip appears in the transmittance of TFE films due to the interference of light caused by organic/inorganic multi-layered configuration, resulting in a dip in the top emission spectrum of TOLEDs. We have found that such a transmittance dip deepens when the number of dyads is large. What is worse, the number of transmittance dips and their sharpness are raised with increased thickness of the polymer layer. When the number of dyads is small, however, the effect of the polymer layer thickness on such a transmittance dip is weak. Therefore, we have addressed that the number of dyads needs to be reduced, but the thickness of the polymer layer should be increased to meet both optical and barrier properties of TOLEDs at the same time.     

势垒层对黑硅光电探测器性能影响的研究

讨论势垒层Si3N4的引入对黑硅光电探测器光电性能的影响。探测器采用金属一半导体一金属（MSM）器件结构在黑硅层和电极间增加一层势垒层以提高肖特基势垒,从而减低器件的暗电流。实验表明,在相同的光照情况下,有势垒层的探测器暗电流比无势垒层的探测器暗电流至少低1个数量级,且势垒层厚度增加30nm其暗电流降低约1个数量级,而...     

铁磁性微晶玻璃的制备

采用熔融法制备了SiO_2-Na_2O-CaO-P_2O_5-Fe_2O_3系微晶玻璃。制备过程中磁铁矿晶相在玻璃自然冷却时自然析出,故不需要对玻璃进行核化和晶化等热处理。利用XRD确定了样品晶相组成并计算了样品中晶体的晶格常数和晶粒度,采用振动样品磁强计(VSM)测试了样品的磁性能。结果表明:所制微晶玻璃只含有磁铁矿晶相并具有生物活性;Fe_2O_3质量分数为45%的样品性能最佳,其比饱和磁矩为20.24A·m~2/kg,内禀矫顽力H_(cj)为7kA/m。     

Effect of hydrogenation on the properties of metal-GaAs Schottky barrier contacts

The effect of hydrogenation (incorporation of atomic hydrogen) on the properties of n-GaAs and the characteristics of Au-GaAs Schottky barrier contacts (the ideality factor of the current-voltage characteristic n, the barrier height ϕ _b, and the reverse voltage V _r at a current of 10 μA) has been investigated. The n-GaAs surface was bare (A-type samples) or was protected by an ultrathin (∼50 ?) layer of SiO₂ (B-type samples) during hydrogenation. It was shown that there was an optimal hydrogenation regime for the A-type samples (temperature range 150–250 °C and duration 5 min), for which n and V _r reached their minimum and maximum values, respectively. For the B-type samples, n and V _r improve starting from minimal durations and temperatures of hydrogenation and remain constant or even improve over the entire investigated range of temperatures (100–400 °C) and durations (1–50 min). The donor impurity passivation processes are roughly the same for the A-and B-type samples. Fiz. Tekh. Poluprovodn. 32, 1343–1348 (November 1998)     

Tunnel excess current in nondegenerate barrier (p-n and m-s) silicon-containing III–V structures

Data are scaled from a study of the forward current in three types of barrier structure: p-n homostructures p-n-GaP/n-Si, p-n-GaAs-n-GaP/n-Si, and p-n-GaAs-n-GaAs/n-Si; heterostructures n-GaP/p-Si, p-GaP/n-Si, n-GaAsP/p-Si, and n-GaAs/p-Si; and Au-n-GaP/ n-Si surface-barrier structures. Epitaxial layers of GaP and GaAs were created on Si-substrates by gaseous phase epitaxy in a chloride system. Temperature measurements show that the forward current has a tunnel character, although the width of the space charge region greatly exceeds the tunneling length. A model is proposed for nonuniform tunneling along dislocations that intersect the space charge region. This type of tunneling is taken into account by introducing a phenomenological “dilution” factor for the barrier. The model makes it possible to calculate the dislocation density in device structures from the current-voltage characteristic. Fiz. Tekh. Poluprovodn. 31, 216–222 (February 1997)     

Intermodulation properties of double- and triple-circuit parametric amplifiers with nonlinear barrier capacitance

There have been performed an experimental investigation of intermodulation effects in narrowband regenerative double- and triple-circuit parametric amplifiers (RDPA and RTPA) with nonlinear barrier capacitance. It has been obtained that their single-signal and double-signal intermodulation characteristics are of the conventional form, and their phase shifts in the vicinity of the resonance frequency are close to 90°, that is not enough for the compensation of nonlinear distortions in the case of amplifiers cascading. It has been demonstrated that the introduction of the additional oscillatory circuit at the double signal frequency into RDPA does allow effective compensation of the intermodulation interferences of odd order in the single-stage parametric amplifier.     

Investigation of electroless cobalt-phosphorous layer and its diffusion barrier properties of Pb-Sn solder

The capability of a cobalt-phosphorous [Co(P)] layer, which was grown via the electroless plating process, to serve as the diffusion barrier of lead-tin (PbSn) solder was investigated in this work. The Auger electron spectroscopy (AES) and energy dispersive spectrometry (EDX) indicated that the phosphorous contents in Co(P) films decrease with increasing film thickness and that the average contents are no less than 8.7 at.% for the specimens prepared in this work. X-ray diffraction in conjunction with composition analyses revealed that the electroless Co(P) layer was a mixture of amorphous and nanocrystalline structures; however, the AES depth profile and subsequent analyses indicated that the first-formed Co(P) layer should be amorphous because it contains as much as 18 at.% P. This implied a good barrier capability for electroless Co(P) because, as revealed by EDX line scan, the Sn and Cu atoms could not penetrate the Co(P) layer after the PbSn/Cu/Co(P)/Cu/Ti/Si sample was subjected to annealing at 250°C in a forming gas ambient for 24 h. The fact that Sn and Cu underlayers could not penetrate the Co layer after such a liquid-state annealing step was evidence that the Co(P) layer may simultaneously serve as a diffusion-barrier interlayer dielectric and as an under-bump metallization for flip-chip copper (Cu) ICs.     

Microwave characterization of the properties and performance of GaAs Schottky barrier mixer diodes

Microwave measurements have been made of the equivalent circuit parameters and performance characteristics of unpackaged GaAs Schottky barrier mixer diodes. The dependence of mixer performance on series inductance, junction capacitance, and series resistance is delineated. Performance of mixer diodes in packaged and unpackaged form is compared.     

Charge current polarization and magnetoresistance in ferromagnetic/organic semiconductor/ferromagnetic devices

Spin-polarized injection and transport in ferromagnetic/organic semiconductor/ferromagnetic devices are studied theoretically. Based on the spin diffusion theory and Ohm’s law, we obtain the charge current polarization and the magnetoresistance, which takes into account the special carriers in organic semiconductors. From the calculation, it is found that the charge current polarization decreases exponentially from the ferromagnetic layer into the organic layer and polarons are effective spin carriers in organic semiconductors for polarized charge current. To get an apparent magnetoresistance in an organic device, it is better to adopt a spin-dependent interface, and the thickness of the organic interlayer is much smaller than the spin diffusion length. Spin polarons are effective carriers for gaining remarkable magnetoresistance in ferromagnetic/organic semiconductor/ferromagnetic devices.     

High barrier properties of transparent thin-film encapsulations for top emission organic light-emitting diodes

This paper reported a low-temperature thin film encapsulation (TFE) process based on atomic layer deposition Al₂O₃ layer for top-emission organic light-emitting devices (TE-OLEDs). The barrier characteristics of both H₂O-based and O₃-based Al₂O₃ films were investigated. O₃-based Al₂O₃ TFE showed lower water vapor transmission rate (WVTR) of 8.7 × 10⁻⁶ g/m² day and longer continuous operation lifetime of 5 folds compared to the device with H₂O-based Al₂O₃ TFE under identical environmental and driving conditions. Furthermore, the extraction of emitting light of the devices with barrier layer was enhanced compared to the bared one. The theory simulation data were consistent with our experimental results and showed the potential for the design of TFE structures optimized for enhancing light transmission.     

Preparation and properties of Ni/InGaN/GaN Schottky barrier photovoltaic cells

Ni/In_xGa_1−xN/GaN Schottky barrier solar cells with different In contents (x = 0.07/0.13) and two types of Schottky patterns (semitransparent current spreading layer and grid contact) are fabricated and the dependences of photovoltaic performances of these solar cells on In contents and Schottky patterns are studied. Solar cells with semitransparent contact have almost the same open-circuit voltages (V_oc) as solar cells with grid contact and exhibit a higher fill factor (FF). However, solar cells with grid contact exhibit a higher maximum output power density (P_max) than semitransparent contact due to their larger short-circuit current density (J_sc). On the other hand, V_oc and FF decrease significantly with increasing In content (beyond the decrease expected from the band gap of InGaN). By comparing the X-ray rocking curves, AFM images, dark current characteristics and spectral responsivities, it could be concluded that the deterioration of InGaN crystal quality with increasing In content is the dominant reason accounting for the strong decrease of V_oc and FF. In addition, using AMPS simulation, the band structure and ideal spectral responsivities are obtained. Comparison of the experimental and simulated results also shows that high crystal quality is a key factor to obtain high performance InGaN-based Schottky barrier photovoltaic cells.