18J,20 Hz固体热容激光器

为研究同体热容激光器运转的物理机制,研制了一台演示验证样机。激光器使用钕玻璃板条为工作物质,脉冲灯抽运,平-凹式稳定谐振腔。固体热容激光器运转有两个工作相,样机达到的技术性能如下：第一工作相输出激光,以20Hz重复频率工作10S,输出能量开始时23．81J／脉冲,结束时18．51J／脉冲;第二工作相冷却工作物质,经编程控制的氮气冷却5min后,激光器可重新进入第一工作相循环工作。分析了限制激光器输出激光时间的两个主要原因。试验表明：固体热容激光器输出激光时,沉积在工作物质中的废热使工作物质处于表面温度高于内部温度的状态。由此工作物质产生了向内的压应力,它使工作物质破坏阈值上升,激光器可以工作在较高的温度状态。对第二工作相冷却工作物质的热管理模型进行了讨论．     

II–VI heterojunction device physics

II–VI compounds are mainly used for their large bandgap. They serve as host materials in electroluminescent devices and as collector or window materials in thin film solar cells. Besides the band discontinuities, the physics of II–VI heterojunctions depends to a great extent on the presence of deep trap levels within the large bandgap. As a typical example we treat the cross-over phenomenon, which can be observed in heat-treated Cu₂S/CdS thin film solar cells.     

智能温度传感器DS18B20

DS18B20是美国DALLAS半导体公司继DS1820之后最新推出的一种改进型智能温度传感器。与传统的热敏电阻相比,它能够直接读出被测温度,并且可根据实际要求通过简单的编程实现9~12位的数字值读数方式。可以分别在93.75ms和750ms内完成9位和12位的数字量,而且从DS18B20读出的信息或写入DS18B20的信息仅需要一根口线(单线接口)读写,温度变换功率来源于数据总线,总线本身也可以向所挂接的DS18B20供电,而无需额外电源。因而使用DS18B20可使系统结构更趋简单,可靠性更高。它在测温精度、转换时间、传输距离、分辨率等方面较DS1820有了很大…     

MBE-Grown II–VI and Related Nanostructures

Nanostructures of II–VI semiconductor materials could potentially offer novel and superior physical (in particular, optoelectronic) properties with respect to their bulk counterparts. Herein, we present our most recent research on several II–VI and related nanostructures grown by molecular beam epitaxy (MBE) technique. These include a ZnSe nanograting. This nanograting structure was realized at the surface of Fe/ZnSe bilayers grown on GaAs(001) substrates by thermal annealing. A model based on an Ewald construction is presented to explain its unusual reflection high-energy electron diffraction (RHEED) patterns. The formation mechanism of this one-dimensional (1D) nanostructure is possibly related to surface energy minimization, together with an Fe–Se exchange interaction and Fe-induced decomposition of several top ZnSe atomic layers during thermal annealing. Another nanostructure investigated was the ZnS Schottky barrier embedded with Fe quantum dots (QDs). Here, a Au/ZnS/Fe-QDs/ZnS/n ⁺-GaAs(100) Schottky barrier structure containing five layers of spherical Fe quantum dots with a diameter of ~3 nm was fabricated. Its I–V characteristic measured from 5 K to 295 K displays negative differential resistance (NDR) for temperature ≤50 K. Staircase-like I–V characteristics were also observed at low temperature in some devices fabricated from this structure. Possible mechanisms that can account for the observed unusual I-V characteristic in this structure are presented. Finally, laterally grown Fe nanowires (NWs) on a ZnS surface were prepared. Under high growth/annealing temperature, two types of Fe NWs with specific orientations can be grown on the ZnS(100) surface. We propose a mean-field model that the torque exerted by type A Fe NWs could effectively turn the two components of type B Fe NWs slightly toward the ZnS [110] direction, leading to the observed misalignment of type B Fe NWs.     

Optimization of II–VI based heterojunctions

The performance of heterojunction devices can be optimized by proper choice of characteristics of the two semiconductors forming the junction and by proper design. One very important element in design is the termination of the active volume of the device with surfaces of low, preferably zero surface recombination velocity. This paper discusses the rules governing the choice of ratios of energy gaps, electron affinities, doping levels, minority carrier lifetimes, lattice constants, etc. for the semiconductors comprising the pair. It also discusses the use of heterostructures to produce the low surface recombination velocity surfaces bounding the active volume of the device. The paper reviews principles of materials science which govern the choice of semiconductors for both the active regions of the device and the heterostructure “encapsulants”. The few attempts to realize electronic structures having the properties required by optimization theory will be described.     

The 3rd MBE workshop — Bratislava 15–17 May 1996

My overall impression is that Slovak scientists are looking for collaboration with the West and are eager to demonstrate their strength and capability. They are very keen to host international conferences ‘to put themselves on the map’, and I hope this workshop on molecular beam epitaxy (MBE) will serve this purpose. I feel privileged to be invited for the second time to give a talk at this meeting. It is also an exciting time to be here and to witness the beginning of a bright new future.     

数字式温度传感器DS18B20及其应用

文章介绍了新一代数字式温度传感器DS18B2 0 ,它集温度感知、数字量转化、高低温限设定和报警于一体。文章详细地阐述了DS18B2 0的测量原理、特性以及在多路温度测量应用中的测量电器设计和软件设计     

基于DS18B20的测温系统设计

针对传统温度检测装置存在的问题,提出了以AT89S51单片机和单总线数字温度传感器DS18820构成的新型温度测量系统。介绍DS18820的特性、内部结构以及单总线技术的特点。详细论述了该系统的设计方案、硬件组成及软件设计流程图。经测试,基于DS18820的测温系统具有结构简单、测温精度高、稳定可靠的优点。     

基于DS18B20的测温系统设计

DS18820数字温度计是DALLAS公司生产的1-Wire,即单总线器件,具有线路简单、体积小、低功耗、高精度、抗干扰能力强等特点的数字温度传感器。简要介绍了DS18820的基本特点、引脚功能、内部结构和工作原理,给出了DS18820的实用电路、使用中的注意事项、硬件及软件设计方法。经过测试,该系统的测量精度及速度等指标均能满足设计要求。     

基于DS18B20倒车雷达系统设计

在光线不足、有灰尘或烟雾、强电磁干扰、有毒等恶劣的环境下,目前国产的倒车雷达即使也是采用超声波测距,但是其灵敏度、准确度受到很大的影响,笔者采用DS18B20温度补偿传感器设计的倒车雷达系统,有效减少了上述的缺陷,减少电路之间的相互干扰,减少电噪声。本系统测距范围为0.1～6m,最大测距误差不超过1cm,且具有硬件结构简单、工作可靠、流程清晰、精度高、成本低等优点,测量时与被测物体无直接接触并能实现距离的实时显示。     

基于DS18B20的温度控制系统设计

在工业生产中温度是常用的被控参数,而采用单片机来对这些被控参数进行控制已成为当今的主流。文中介绍了以AT89S52单片机为核心,以数字温度计芯片DS18B20为测温单元的的温度控制系统,该系统通过三极管的通断控制继电器,来控制电热器调节温度,较好实现了温度的智能控制。     

DS18B20温度传感器的应用设计

该设计介绍了DS18B20型数字温度传感器内部结构及工作时序,并提出了以 DS18B20和 AT89C51为核心设计的数字温度计设计方案。实践证明,该数字式温度计的测温范围为-50～＋110℃,精度误差在0.1℃以内,具有测温精度高,控制性能良好等特点。设计还介绍了一种基于51单片机和DS18B20数字温度传感器来进行温度测量的方法,包括温度传感器芯片的选取、单片机与温度传感器接口电路的设计,以及实现温度信息采集和数据传输的软件设计。该温度计完全适用于一般的应用场合,也可在高低温报警、远距离多点测温控制等方面进行应用。     

Formation of II–VI nanostructures on vicinal surfaces

We report on the peculiar aspects of the growth of CdTe by atomic layer epitaxy compared to the one developed for other compound semiconductors. It is self-organized from two points of view, the amount of material deposited by ALE cycle, namely 0.5 ML/cycle for substrate temperatures around 260°C and the geometry of the deposited CdTe which tends to form preferentially square islands with 〈100〉 edges. Using these results, we demonstrate the possibility of growing tilted superlattices made out of CdTe and MnTe. However, the lateral ordering created by this structure is strongly limited by two effects, the Cd/Mn atomic exchange and the step array disorder.     

A 18-mW,20-MHz bandwidth,12-bit continuous-time∑△modulator using a power-efficient multi-stage amplifier

正A fourth-order continuous-time sigma delta modulator with 20-MHz bandwidth,implemented in 130nm CMOS technology is presented.The modulator is comprised of an active-RC operational-amplifier based loop filter,a 4-bit internal quantizer and three current steering feedback DACs.A three-stage amplifier with low power is designed to satisfy the requirement of high dc gain and high gain-bandwidth product of the loop filter.Non-return-to -zero DAC pulse shaping is utilized to reduce clock jitter sensitivity.A special layout technique guarantees that the main feedback DAC reaches 12-bit match accuracy,avoiding the use of a dynamic element matching algorithm to induce excess loop delay.The experimental results demonstrate a 64.6-dB peak signal-to-noise ratio,and 66-dB dynamic range over a 20-MHz signal bandwidth when clocked at 480 MHz with 18-mW power consumption from a 1.2-V supply.     

Atomic and electronic structure of the silicon and silicon-metal Si20, Si 20 − , NaSi20, KSi20 nanoparticles

The results of atomic-structure optimization and calculation of the electronic structure of the Si₂₀, Si ₂₀ ^? , NaSi₂₀, and KSi₂₀ clusters are reported. The PM3 and AM1 semiempirical methods were used in the calculations. It is shown that the Na and K atoms stabilize the fullerene-like silicon structure. The effect of configuration of the clusters on their electronic structure is analyzed.