应用激光化学的发展近况

本文报导了近年来激光在化学中期应用取得进展的一些成功实例，并提出了激光化学在今后十年内一些看来很有前途的应用领域。请如激光分离同位素，激光提纯化学品，激光热解合成超细粉末材料，激光在分析化学中的应用，激光催化，激光化学沉积及重要化学药品的合成等。由所取得的成果可以予期，应用激光化学将会有一个美好的前景。     

低能电子显微方法的新进展

本文综述入射电子在样品中的散射、二次电子的产生机制和低能电子逸出的能量阈值效应。在大能隙半导体或绝缘体中,低能电子的非弹性散射自由程显著大于金属,从而为纳米材料的表征提供了条件。综述了低能电子显微术（LEEM）、低能电子投影显微术、弹道电子发射显微术（BEEM）、光发射电子显微技术（PEEM）等低能电子显微方法,介绍了这些方法得到的许多结果。     

Recent developments in magnetic levitation

New developments in magnetic levitation by tuned circuits are described. Suspension of relatively large weights at low frequencies is now possible. The system is extremely simple and therefore reliable. Owing to the high reliability and cylindrical symmetry, the levitation is suitable for magnetic bearings.     

Recent developments in power transistors

Power transistors capable of providing five watts output are now in production. Because these units are relatively non-linear in their characteristics, large signal graphical analysis of their behavior is necessary. To facilitate this, the static characteristics of the grounded base, grounded emitter, and grounded collector circuits are presented for several temperatures. Since power transistors are seldom driven with a high impedance source, the input voltages must be known as well as the input currents. These characteristics are drawn to indicate both simultaneously on one chart. The power that must be removed from the junction of these transistors requires that the mounting for the transistor be thermally adequate to remove the heat without allowing the temperature of the Junction to exceed its critical value. The temperature power relationship is discussed and the theoretical size requirements for a heat dissipator are shown for free air convection and forced convection.     

Recent developments in feedback communication

The use of a noiseless feedback communication channel to improve both digital and analog transmission is discussed. The feedback channel is used in an iterative signaling procedure called center-of-gravity feedback. Suboptimum schemes having a less severe-feedback requirement are also treated.     

Recent developments in light-emitting-diode technology

This paper describes recent trends in LED technology. Emphasis is placed on the LED materials and device-fabrication technologies that have resulted in larger and brighter LED displays with a variety of colors, and on the monolithic red-emitting LED displays that are commonly employed as watch and calculator displays.     

Recent developments in micromachined silicon

This paper provides a review, directed at scientists and engineers concerned with microsystems technology, of advances in microelectromechanical systems (MEMS). The emphasis is on silicon technology, where the electrical properties of the material are exploited in circuitry and the mechanical properties are used in sensor and microstructure applications. Developments in surface micromachining are discussed, and applications in sensors, microelectronic devices, vacuum microanalysis systems, microfluidics, and optoelectronic subsystems are reviewed. Some emerging technologies are assessed and promising new research directions are identified     

Recent developments in rapid thermal processing

Rapid thermal annealing (RTA) with a short dwell time at maximum temperature is used with ion implantation to form shallow junctions and polycrystalline-Si gate electrodes in complementary, metal-oxide semiconductor (CMOS) Si processing. Wafers are heated by electric lamps or steady heat sources with rapid wafer transfer. Advanced methods use “spike anneals,” wherein high-temperature ramp rates are used for both heating and cooling while also minimizing the dwell time at peak temperature to nominally zero. The fast thermal cycles are required to reduce the undesirable effects of transient-enhanced diffusion (TED) and thermal deactivation of the dopants. Because junction profiles are sensitive to annealing temperature, the challenge in spike annealing is to maintain temperature uniformity across the wafer and repeatability from wafer to wafer. Multiple lamp systems use arrayed temperature sensors for individual control zones. Other methods rely on process chambers that are designed for uniform wafer heating. Generally, sophisticated techniques for accurate temperature measurement and control by emissivity-compensated infrared pyrometry are required because processed Si wafers exhibit appreciable variation in emissivity.     

Recent developments in silicon optoelectronic devices

Due to the rapid growth of the internet and multi-media communication networks, there are urgent needs and tremendous commercial values in the development of optoelectronics integrated circuits (OEICs). This work reviews the recent developments and the prospect of silicon-based integrated optoelectronic circuits (Si-OEICs). The technological aspects of porous silicon and oxynitride devices for integrated optoelectronic applications are discussed. Some optoelectronic devices being realized with these technologies are described. Recent achievements indicate that the present constraints for using Si-based materials in optoelectronics are mainly technological rather than physical. Once these technological difficulties are resolved, the realization and applications of Si-OEICs will grow rapidly.