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Discusses the utilities of corrugated quantum well infrared photodetectors (QWIP) in detector material characterization. Capability of the characterization technique of providing accurate and detailed information on the intrinsic properties of QWIP materials under actual operating conditions.

Presents a method for the calculation of the deformation profiles in chiral nematic liquid crystal cells. Illustration of the method in cases of an asymmetric twisted nematic cell; Applicability of the method to the study on the stability of ultraviolet type two-domain twisted nematic.

The magnetoresistance (MR) ratio is enhanced by 35% by inserting the nano-oxide layer (NOL) at the Ta/Co interface in the FeMn-based top spin valves (Ta/NOL/Co/Cu/Co/FeMn/Ta). The enhancement is attributed to specular reflection, resulting in a large resistance change and small sheet resistance. However, the formation of NOL at the interface of Ta/Co suppresses the (111) texture, resulting in small exchange fields. Top spin valves with NOLs show good thermal stability up to 200 °C annealing. The MR ratio is further increased after annealing at temperatures below 200 °C. Enhancement of the MR ratio by 61% can be achieved by annealing at 150 °C. For bottom spin valves (Ta/NiFe/FeMn/Co/Cu/NiFe/Ta), NOLs formed at FeMn/Co and NiFe/Ta interfaces increase MR ratios, but NOLs at Co/Cu or Cu/NiFe deteriorate the differential spin scattering and significantly reduce MR ratios. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Investigates the effect of partial substitution neodymium-fluorine or chlorine for neodymium-oxygen on the reduction-diffusion process of neodymium-iron-boron powders. Reaction of neodymium-fluorine or chlorine with calcium; Distribution of calcium-chlorine around neodymium-iron-boron grains after reaction; Reaction of calcium-chlorine with water.

Investigates the effect of alloying concentration of dysprosium and the absorption amount of hydrogen on the magnetic properties of PrFeB magnets. Preparation of the sintered magnets; Demagnetization curves of the magnets; Information on the alloying effect of hydrogen.

Presents a novel low-temperature preparation of Ni-Zn ferrite and the properties of the ultrafine particles formed. Saturation magnetization of the ferrites; Outcome of an increase in hydrazine concentrations; Variations of the magnetic properties and lattice parameters as a function of preparation conditions.

Provides information on a study which investigated the effect of nitrogen interstitial in an alpha-iron crystalline on the magnetic soft properties of an iron compound thin film. Methods; Results; Discussion.

Examines the effect of grain size of densely sintered manganese-zinc ferrites. Details on the experiment; Influence of the reduction of grain boundary layer on high-electrical-resistivity boundary layer; Frequency dependence of resistivity for samples; Information on the domain configuration effect.

Provides information on a study that investigated the effect of the addition of Er[sub2]O[sub3] on the microstructure and physical properties of manganese-zinc ferrites for high-power use. Experimental procedure; Results and discussion on the study; Conclusions.

Investigates the peak value of switching field distribution, coercivity and saturation magnetization as functions of temperature in Co-δ-Fe[sub2]O[sub3] and δ-Fe[sub2]O[sub3] powders. Correlation of the coercivity of the powders with temperature; Formula for studying the temperature dependence of magnetization.

Extensive efforts have been made to develop metallic-glasses with large casting diameter. Such efforts were hindered by the poor understanding of glass formation mechanisms and the origin of the glass-forming ability (GFA) in metallic glass-forming systems. In this work, we have investigated relaxation dynamics of a model bulk glass-forming alloy system that shows the enhanced at first and then diminished GFA on increasing the percentage of micro-alloying. The micro-alloying did not have any significant impact on the thermodynamic properties. The GFA increasing on micro-alloying in this system cannot be explained by the present theoretical knowledge. Our results indicate that atomic caging is the primary factor that influences the GFA. The composition dependence of the atomic caging time or residence time is found to be well correlated with GFA of the system. [ABSTRACT FROM AUTHOR]

Studies the optimization of blazed quantum-grid infrared photodetectors. Purposes of the grid; Optimization of the grid parameters; Numerical simulation using the modal transmission-line theory.

Studies the capacitance-voltage characteristics of liquid crystal displays with periodic interdigital electrodes. Extreme capacitances at high and low driving voltages; Technique of conformal mapping.

In quantum well infrared photodetectors, the detector dark current usually is composed of a wide range of energies originated from thermionic emission as well as thermally assisted tunneling. Yet, it is a common practice to assign a single noise gain to all electrons irrespective of their energies. This assigned value can only represent the mean since both the hot-electron lifetime and the transit time, whose ratio determines the gain, are energy dependent. In this work, we have resolved the energy dependence of the noise gain using an electron energy filter. We find that although the noise gain increases initially with energy as expected, it reaches a maximum at 0.27 eV above the GaAs conduction band edge, and then decreases and forms a minimum at 0.31 eV. We attribute this decrease to the Γ-L intervalley scattering, which increases the transit time of the electrons. © 1998 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The sensitivity of a focal plane array in terms of the noise equivalent temperature difference ultimately depends on the detector photocurrent to dark current ratio r[sub I]. In this work, we have integrated two approaches in the quantum well technology that can increase r[sub I] into a single detector structure. The new detector is referred to as the corrugated infrared hot-electron transistor (CI-HET). In this detector structure, an energy filter is grown next to a standard quantum well infrared photodetector (QWIP) for more selective collection of the photocurrent. At the same time, corrugated structures are physically fabricated into the detector pixel to increase light absorption in the QWIP. With this combined approach, r[sub I] is able to increase by more than a factor of five compared to a standard QWIP. In addition, the new structure reduces the total current of the detector to a level that is suitable for signal integration. © 1998 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A quantum-well infrared photodetector (QWIP) based on the corrugated light-coupling scheme has been fabricated and tested for remote temperature sensing. The QWIP consists of two stacks of multiple quantum wells (MQWs), each sensitive in one of the atmospheric infrared transmission windows and each with a separate readout circuit. High optical coupling efficiency is obtained in both wavelength ranges, demonstrating the use of the corrugated structure for two-color detection. By monitoring the ratio of the photocurrent generated simultaneously in each MQW stack, the temperature of the object emitting the radiation can be determined, regardless of its emissivity and the geometrical factors. This temperature sensing ability is tested by using a blackbody radiator with precision temperature control as the target. The agreement between the measured and the preset temperatures indicates that the corrugated QWIP is capable of precision thermometric measurements. © 1998 American Institute of Physics. [ABSTRACT FROM AUTHOR]