汽相生长金刚石膜中的高温灯丝

热丝CVD（Chemical Vapor Deposition）法生长金刚石，热灯丝常用钨丝。在实验中，实验人员发现了钨丝的局限性，于是又选用了钽丝。经实验后，发现钽丝有更高的灯丝温度，但又具有自己的缺限。而将钨丝与钽丝结合起来，不仅能使灯丝温度更高，更兼有钨的优良性能。     

金刚石薄膜制备和评价

采用平直钨丝作热解源,并借助钨丝支架的弹性恢复力,较好地解决了热丝热解化学气相沉积法(HFCVD)合成金刚石过程中热解丝的变形问题.样品独立加热,基片温度、钨丝温度、钨丝与样品基片距离均可独立调节.装置改进后,在Si(100)上合成了面积大约45mm×25mm的比较均匀的金刚石膜.用扫描电子显微镜(SEM)、Raman光谱和X射线衍射仪对制备的金刚石膜进行了分析.     

钨单晶的热电性能

对于钨热电性能的研究已有大量文献作过报导。鉴于所研究的钨丝是用不同纯度的钨并采用各种不同方法制取的,故所得的钨的分度特性也不一样。而对所研究的钨丝的化学分析大量文献中均无报导。文献所提供的资料证明,用粉末冶金材料制取的钨丝做热电极使用起来有一系列困难,因为由于这种钨的纯度低、再加上生产     

MIM点接触二极管性能研究有初步结果

金属—氧化物—金属(MIM)点接触二极管是对可见光到近红外波段绝对测量激光频率的关键元件。中国计量科学研究院量子室对自控的钨镍点接触二极管的性能开展了初步的研究工作。我们用直径为3毫米的镍丝作成小柱并一端面抛光成镜面作为一个电极,而另一电极是用直径为25微米的钨丝在二个克分子浓度的氢     

钨丝/锆基非晶复合材料研究进展

钨丝/锆基非晶复合材料作为近20年新出现的穿甲工程材料,是一种极有可能替代具有放射性危害的贫铀合金和穿甲威力稍差的钨合金的新兴材料。自从钨丝/锆基非晶复合材料被制备出来以后,各学者先后对材料中钨丝和锆基非晶合金之间的界面接触强度、钨丝/锆基非晶复合材料中钨丝的参数、环境温度、应变率、仿真计算以及穿甲应用等方面进行了研究。研究表明,制备过程中保温温度,钨丝/锆基非晶复合材料中钨丝的排布方式、体积分数、直径,环境温度,应变率等因素都能对钨丝/锆基非晶复合材料的性能产生影响;随着计算机技术的发展,钨丝/锆基非晶复合材料的有限元仿真计算已经从等效模型发展到准细观建模,能够模拟其动静态压缩过程、侵彻过程,仿真结果和试验结果基本吻合;在应用方面,试验研究验证了钨丝/锆基非晶复合材料弹芯在侵彻过程中的"自锐"性能。文章概述了钨丝/锆基非晶复合材料在上述领域的研究进展并展望了该材料的发展方向。     

He等离子体辅助的纳米钨结构材料的制备

利用He等离子体辅助的方法制备了纳米钨结构材料,采用扫描电子显微镜、轻敲模式原子力显微镜对不同辐照离子剂量和功率变化条件下处理的样品形貌、表面粗糙度等特征进行了分析。结果表明,在放电功率为6 kW,离子能量为220 eV条件下,钨表面先出现纳米孔结构,随着离子辐照剂量的增加,纳米孔径逐渐增加,辐照剂量为1.0×10~(26) ions·m~(-2)时,样品表面呈现密集的无序分布的纳米丝结构层,纳米结构层的厚度也随辐照剂量的增加而增加。高分辨扫描电子显微镜的测试结果表明纳米丝根部与钨基体界面处存在大量的纳米级He泡,由此给出了纳米钨丝是由He泡演化而来的直接证据。     

钨灯丝再结晶行为研究

钨灯丝的再结晶温度和晶粒结构同钨丝抗下垂能力密切相关.荷兰Philips照明研发中心CJ.M.Denissen等人对灯用钨丝的再结晶行为进行了深入的研究.他们从热力学的观点出发,用热激活过程来描述钨丝在升温时从形核到晶粒长大的过程.为了区别与普通钨丝的再结晶温度的不同,特意给灯用钨丝的再结晶温度定义为:钨丝在升温过程中,当其50%(体积分数)发生再结晶时的温度叫该钨丝的再结晶温度,用TR表示,与此刻对应的时间(从加热开始时算起)称为特征时间,用t0.5表示.TR,t0.5与钨丝的再结晶激活能Q的关系由方程(1)表达.     

铼改善了钨丝的性能

比头发丝还细的钨丝,除做灯泡灯丝外,可用于静电吸尘器、复印机、真空金属喷镀设备、辐射加热设备、电视显像管和其它有特殊性能要求的产品,钨丝还可用于硼化学蒸发涂镀,强化航空和航天构件的高温合成材料。普通钨丝由于韧性的极限使其在许多领域的应用受到一定的限制,但是用铼与钨的合金制成的钨丝,可大大提高自身的延伸率。含铼3%的钨丝可     

超细钨丝

本文研究了用连续电解抛光的方法制造超细钨丝的工艺。建立的一套装置,可以制备直径小于5μ的钨丝。观察了丝材在连续抛光时的行为,讨论了各项工艺参数的影响。使用证明,制得的丝材性能良好。这种工艺不仅可用于超细钨丝的工业生产,也可用于其它金属细丝、薄带的清洗及制备。     

水份对粘胶强力丝在空气中热解的影响

本文首先对粘胶强力丝的脱水过程进行研究，然后对含水量分别为１０％、１４％、２５％、５６％的粘胶强力丝在空气气氛中热处理时的热失重以及在２％ＮａＯＨ溶液中的溶解度进行了对比，并结合绝干粘胶强力的热解从而对热解中水份的影响作了初步探讨。结果认为：粘胶强力丝所含水份可分为物理吸附水与结合水，而水份的存在极大地加快了热解反应的进行，并使得最大失重速率所对应的温度值大大下降，另外，由于含水粘胶强力丝在热解时     

Continuum source tungsten coil atomic fluorescence spectrometry

A simple continuum source tungsten coil atomic fluorescence spectrometer is constructed and evaluated. The heart of the system is the atomizer: a low-cost tungsten filament extracted from a 150 W light bulb. The filament is resistively heated with a small, solid-state, constant-current power supply. The atomizer is housed in a glass chamber and purged with a 1 L/min flow of a conventional welding gas mixture: 10% H(2)/Ar. A 25 μL sample aliquot is pipetted onto the tungsten coil, the liquid is dried at low current, and then the atomic vapor is produced by applying a current in the range 3.5-5.5 A. The atomization current does not produce temperatures high enough to excite atomic emission. Radiation from a 300 W xenon lamp is focused through the atomic vapor, exciting atomic fluorescence. Fluorescence signals are collected using a hand-held charge-coupled device (CCD) spectrometer. Simultaneous determination of ten elements (Ag, Bi, Cr, Cu, Ga, In, Mg, Mn, and Tl) results in detection limits in the range 0.3 to 10 ng. The application of higher atomization currents (10 A) leads to straightforward detection of atomic emission signals with no modifications to the instrument.     

Vacancy‐Induced Synaptic Behavior in 2D WS2 Nanosheet–Based Memristor for Low‐Power Neuromorphic Computing

Memristors with nonvolatile memory characteristics have been expected to open a new era for neuromorphic computing and digital logic. However, existing memristor devices based on oxygen vacancy or metal‐ion conductive filament mechanisms generally have large operating currents, which are difficult to meet low‐power consumption requirements. Therefore, it is very necessary to develop new materials to realize memristor devices that are different from the mechanisms of oxygen vacancy or metal‐ion conductive filaments to realize low‐power operation. Herein, high‐performance and low‐power consumption memristors based on 2D WS₂ with 2H phase are demonstrated, which show fast ON (OFF) switching times of 13 ns (14 ns), low program current of 1 µA in the ON state, and SET (RESET) energy reaching the level of femtojoules. Moreover, the memristor can mimic basic biological synaptic functions. Importantly, it is proposed that the generation of sulfur and tungsten vacancies and electron hopping between vacancies are dominantly responsible for the resistance switching performance. Density functional theory calculations show that the defect states formed by sulfur and tungsten vacancies are at deep levels, which prevent charge leakage and facilitate the realization of low‐power consumption for neuromorphic computing application.     

Design,analysis and application of high set-up ZVT DC–DC converter with direct power transfer

In this paper, a new snubber cell for soft switched high set-up DC–DC converters is introduced. The main switch is turned on by zero-voltage transition and turned off by zero-voltage switching (ZVS). The main diode is turned on by ZVS and turned off by zero-current switching. Besides, all auxiliary semiconductor devices are soft switched. Any semiconductor device does not expose the additional current or voltage stress. The new snubber transfers some of the circulation energy to the output side when it ensures soft switching for main semiconductor devices. Thus, the current stress of auxiliary switch is significantly reduced. Besides, the total efficiency of converter is high due to the direct power transfer feature of new converter. A theoretical and mathematical analysis of the new converter is presented, and also verified with experimental set-up at 500 W and 100 kHz. Finally, the overall efficiency of new converter is 97.4% at nominal output power.     

Investigation of thermal and hot-wire chemical vapor deposition copper thin films on TiN substrates using CupraSelect as precursor

Copper films were deposited on oxidized Si substrates covered with TiN using a novel chemical vapor deposition reactor in which reactions were assisted by a heated tungsten filament (hot-wire CVD, HWCVD). Liquid at room temperature hexafluoroacetylacetonate Cu(I) trimethylvinylsilane (CupraSelect) was directly injected into the reactor with the aid of a direct-liquid injection (DLI) system using N2 as carrier gas. The deposition rates of HWCVD Cu films obtained on TiN covered substrates were found to increase with filament temperature (65 and 170 degrees C were tested). The resistivities of HWCVD Cu films were found to be higher than for thermally grown films due to the possible presence of impurities into the Cu films from the incomplete dissociation of the precursor and W impurities caused by the presence of the filament. For HWCVD films grown at a filament temperature of 170 degrees C, smaller grains are formed than at 65 degrees C as shown from the taken SEM micrographs. XRD diffractograms taken on Cu films deposited on TiN could not reveal the presence of W compounds originating from the filament because the relative peak was masked by the TiN [112] peak.     

A novel method for suppressing silicidation of tungsten catalyzer during silane decomposition in Cat-CVD

Growth of tungsten silicide (WSi_x) on tungsten (W) catalyzer surface is investigated by monitoring resistance change of heated W wire in silane (SiH₄) atmosphere. To know a method suppressing the silicide formation, the effect of carbonization of W surface is also studied. Resistance change of heated W, observed in initial stage just after SiH₄ introduction, is brought about increase in power consumption due to decomposition of SiH₄. This power consumption can be drastically reduced when W surface is carbonized. Therefore, carbonization of tungsten surface is effective to stabilize the catalyzer temperature and to suppress W silicidation.     

Diamond deposition on cemented carbide by chemical vapour deposition using a tantalum filament

Diamond deposition on WC-Co cemented carbide was examined by chemical vapour deposition using a tantalum filament. The filament was much superior to conventional tungsten filament for high-temperature use. Diamond film was deposited at a filament temperature up to about 2600 °C for tantalum filament, which was much higher than the maximum filament temperature available for tungsten (2000 °C). The critical methane concentration in H₂-CH₄ gas for diamond deposition became higher with increasing filament temperature. A deposition rate about 20 times higher was obtained when using a tantalum filament compared with a tungsten filament. The origin of the improved deposition rate of diamond on WC-Co substrate using a tantalum filament is discussed.     

Nanoscale Plasmon‐Enhanced Spectroscopy in Memristive Switches

Resistive switching memories are nonvolatile memory cells based on nano‐ionic redox processes and offer prospects for high scalability, ultrafast write and read access, and low power consumption. In two‐terminal cation based devices a nanoscale filament is formed in a switching material by metal ion migration from the anode to the cathode. However, the filament growth and dissolution mechanisms and the dynamics involved are still open questions, restricting device optimization. Here, a spectroscopic technique to optically characterize in situ the resistive switching effect is presented. Resistive switches arranged in a nanoparticle‐on‐mirror geometry are developed, exploiting the high sensitivity to morphological changes occurring in the tightly confined plasmonic hotspot within the switching material. The focus is on electrochemical metallization and the optical signatures detected over many cycles indicate incomplete removal of metal particles from the filament upon RESET and suggest that the filament can nucleate from different positions from cycle to cycle. The technique here is nondestructive and the measurements can be easily performed in tunable ambient conditions and with realistic cell geometries.     

Atomically Thin Femtojoule Memristive Device

The morphology and dimension of the conductive filament formed in a memristive device are strongly influenced by the thickness of its switching medium layer. Aggressive scaling of this active layer thickness is critical toward reducing the operating current, voltage, and energy consumption in filamentary‐type memristors. Previously, the thickness of this filament layer has been limited to above a few nanometers due to processing constraints, making it challenging to further suppress the on‐state current and the switching voltage. Here, the formation of conductive filaments in a material medium with sub‐nanometer thickness formed through the oxidation of atomically thin two‐dimensional boron nitride is studied. The resulting memristive device exhibits sub‐nanometer filamentary switching with sub‐pA operation current and femtojoule per bit energy consumption. Furthermore, by confining the filament to the atomic scale, current switching characteristics are observed that are distinct from that in thicker medium due to the profoundly different atomic kinetics. The filament morphology in such an aggressively scaled memristive device is also theoretically explored. These ultralow energy devices are promising for realizing femtojoule and sub‐femtojoule electronic computation, which can be attractive for applications in a wide range of electronics systems that desire ultralow power operation.     

Deposition of thermal and hot-wire chemical vapor deposition copper thin films on patterned substrates

In this work we study the hot-wire chemical vapor deposition (HWCVD) of copper films on blanket and patterned substrates at high filament temperatures. A vertical chemical vapor deposition reactor was used in which the chemical reactions were assisted by a tungsten filament heated at 650 degrees C. Hexafluoroacetylacetonate Cu(I) trimethylvinylsilane (CupraSelect) vapors were used, directly injected into the reactor with the aid of a liquid injection system using N2 as carrier gas. Copper thin films grown also by thermal and hot-wire CVD. The substrates used were oxidized silicon wafers on which trenches with dimensions of the order of 500 nm were formed and subsequently covered with LPCVD W. HWCVD copper thin films grown at filament temperature of 650 degrees C showed higher growth rates compared to the thermally ones. They also exhibited higher resistivities than thermal and HWCVD films grown at lower filament temperatures. Thermally grown Cu films have very uniform deposition leading to full coverage of the patterned substrates while the HWCVD films exhibited a tendency to vertical growth, thereby creating gaps and incomplete step coverage.