Plasma immersion ion implantation for SOI synthesis: SIMOX and ion-cut

We have demonstrated feasibility to form silicon-on-insulator (SOI) substrates using plasma immersion ion implantation (PIII) for both separation by implantation of oxygen and ion-cut. This high throughput technique can substantially lower the high cost of SOI substrates due to the simpler implanter design as well as ease of maintenance. For separation by plasma implantation of oxygen wafers, secondary ion mass spectrometry analysis and cross-sectional transmission electron micrographs show continuous buried oxide formation under a single-crystal silicon overlayer with sharp Si/SiO₂ interfaces after oxygen plasma implantation and high-temperature (1300°C) annealing. Ion-cut SOI wafer fabrication technique is implemented for the first time using PIII. The hydrogen plasma can be optimized so that only one ion species is dominant in concentration and there are minimal effects by other residual ions on the ion-cut process. The physical mechanism of hydrogen induced silicon surface layer cleavage has been investigated. An ideal gas law model of the microcavity internal pressure combined with a two-dimensional finite element fracture mechanics model is used to approximate the fracture driving force which is sufficient to overcome the silicon fracture resistance.     

Inductive learning from preclassified training examples: anempirical study

Many real-world decision-making problems fall into the general category of classification. Algorithms for constructing knowledge by inductive inference from example have been widely used for some decades. Although these learning algorithms frequently address the same problem of learning from preclassified examples and much previous work in inductive learning has focused on the algorithms' predictive accuracy, little attention has been paid to the effect of data factors on the performance of a learning system. An experiment was conducted using five learning algorithms on two data sets to investigate how the change in labeling the class attribute can alter the behavior of learning algorithms. The results show that different preclassification rules applied on the training examples can affect either the classification accuracy or classification structure     

Optimal structural design with damping constraint limitations

The algorithm optimization presented uses the optimality criteria method so as to minimize the total weight of the structure in the presence of a constraint of the damping type. The goal of this study is to increase the structural damping by optimizing the viscoelastic and elastic material distribution over the structure. The types of damping considered are hysteristic. The gradient of the constraint function in relation to the design variables is calculated with the aid of a complex variable sensitivity method. Several numerical results are presented to validate the algorithm proposed.     

Quartz microbalance study of4He and H2 on sodium

A quartz microbalance technique has been used to study the growth of⁴He and H₂ adsorbed on sodium. In contrast to cesium, adsorption of⁴He and H₂ do occur on a sodium surface.     

Convection in a concentric annulus with heat generating porous media and a permeable inner boundary

The effects of a permeable inner boundary on the maximum temperature and the convective flows were investigated numerically for a two-dimensional horizontal annulus containing a uniformly heat generating porous media. The time-dependent governing equations were nondimensionalized and put into an explicit finite difference numerical form. The finite difference equations were obtained from truncated Taylor series expansions using a central differencing scheme. Nondimensional temperatures and streamlines were obtained for heat generation rates ranging from 20 to 1,500 W/m³ corresponding to a range of modified Rayleigh numbers of 324 to 24,340 and for several combinations of isothermally heated wall conditions for annuli of radius ratio of 2. It was found that multi-cellular flows occur at the highest Rayleigh numbers investigated.     

Simple approximations of the DC flux influence on the core losspower electronic ferrites and their use in design of magnetic components

The effect of DC flux on the core loss is examined for the practical range of power and frequency. Relevant core loss equations are derived and applied to an optimization algorithm to determine the minimum core loss at a given ratio of s (DC flux density to AC peak flux density). It has been found that the curves of hysteresis loss density versus the ratio of s exhibit a peak at a critical ratio. Below or above this critical ratio, the loss density decreases drastically. On the other hand, the curves of eddy-current loss density versus the ratio of s exhibits a minimum point at a critical ratio. Below or above this critical ratio, the loss density increases gradually     

High-power 980-nm AlGaAs/InGaAs strained quantum-well laser grown by OMVPE

High-power lattice-strained AlGaAs/InGaAs graded index separate-confinement heterostructure (GRINSCH) quantum-well lasers emitting at a 980-nm wavelength have been grown by organometallic vapor phase epitaxy (OMVPE) and fabricated with a self-aligned ridge-waveguide structure. Using a 3- mu m-wide and 750- mu m-long AR-HR coated laser, 30 mV of optical power was coupled into optical fibers with 28.6% efficiency. A dominating single-lobe far-field radiation pattern was obtained from a wedge-shaped ridge-waveguide laser for output power as high as 240 mW with a maximum output power of 310 mW.<>     

Regulating contents and furnishings.

The criteria in the 1991 edition of the Life Safety Code are a first attempt to address the fire hazards associated with upholstered furniture and mattresses. Recognizing that the criteria do not represent a complete hazard analysis, it is anticipated that the subcommittee will continue its efforts and will evaluate the appropriateness of additional criteria. The NFPA Standards Council also has appointed a Technical Committee on Contents and Furnishings, which will meet in August 1991. This committee will have primary responsibility for developing fire hazard calculation procedures and documents that other committees can use to control the fire hazards of contents and furnishings.     

The on-line texture analysis of steel strips

A new on-line texture-analyzing system and its application to nondestructive r value determination is discussed. In addition to providing a brief theoretical background and describing the instrumental set-up, the article presents off-line measurements with this equipment and demonstrates the high accuracy of the determined r-values. A special feature of the unit is the possibility to simultaneously measure the most important r values—r₀, r₄₅, r₉₀, and r_m.     

Rapid isothermal processing for fabrication of GaAs-basedelectronic devices [HBTs]

The use of rapid isothermal processing (RIP) is detailed for each of the three annealing steps in the fabrication of heterostructure-based devices such as heterojunction bipolar transistors (HBTs). RIP can be used for the alloying of ohmic metal contacts, annealing of ion-bombarded regions for device isolation or parasitic capacitance reduction, and for conventional implant activation annealing. High-speed (f_T=65 GHz) HBTs were achieved using RIP for all of the required heating steps. The authors compare the use of several types of silicon carbide-coated graphite susceptors for eliminating slip formation on 2- and 3-in-diameter GaAs wafers during high-temperature implant activation annealing