晶态Si3N4／非晶SiO2同轴纳米线的电子显微学研究

Si3N4是一种用途广泛的功能材料，Si3N4纳米线有望在电子、光学和机械领域展现其特殊性能：在没有催化剂情况下，我们在硅衬底上直接合成了Si3N4／SiO2同轴纳米线。生长条件：氮气氛．生长温度1250℃．1.5h，自然冷却。利用电子衍射、高分辨像和电子X射线能谱技术，我们用Tacnai F30场发射电子显微镜研究了Si3N4／SiO2同轴纳米线的微观组织结构，探讨了这种纳米线的生长机制。     

具有汇聚特性的场发射电子源的模拟研究

提出了一种具有汇聚特性的新型场发射阴极结构,利用有限元方法模拟计算了此种阴极结构在不同参数条件下的电场分布、电子轨迹,考察了不同参数对电子汇聚效果的影响,给出了此种场发射阴极的栅极-阴极间距、栅极宽度、阳极电压、栅极电压等基本参数对汇聚效果的影响.模拟计算结果表明,电子束的汇聚程度随着栅极-阴极间距的增大而增大,随着栅极宽度的增大而减小;电子束的汇聚程度与阳极电压、栅极电压参数密切相关,并存在最优参数.     

FESEM在Bi系高温超导材料研究中的应用

利用热场发射扫描电镜 (ＦＥＳＥＭ)的基本功能 ,通过对比样品的简单分析 ,展示Ｂｉ系高温超导材料的微观特性。ＬＥＯ15 30热场发射扫描电镜 (ＦＥＳＥＭ)有 3种成像方式 :二次电子 (ＳＥ2 )像、背散射 (ＱＢＳＤ)像和ＩＮＬＥＮＳ像 (内镜像 )。由于采用场发射的电子枪 ,ＦＥＳＥＭ的电子束斑在几个ｎｍ的量级[1] ,ＩＮＬＥＮＳ像分辨率可以达到 1ｎｍ(2 0ｋＶ)～ 3ｎｍ(10ｋＶ)。ＩＮＬＥＮＳ像只接收从样品表面几个ｎｍ深度垂直反射的电子信号 ,因而适于分析样品表面的细节 ,而ＳＥ2像适于观察景深较大的样品 ,如图Ａ(1,2 )。此外 ,由图…     

场发射扫描电镜上探头探测效率下降的现象及原因分析

针对部分日立场发射扫描电镜上探头探测效率下降而导致图片分辨率下降等现象,分析了上探头探测效率下降的原因,指出在高加速电压下高能背散射电子经反弹进入上探头的概率随之增加,导致铝膜的损坏和闪烁体的充电,空气可以中和并带走电荷。这对延长电镜上探头的寿命及保持电镜处在较好的使用状态具有重要意义。     

Performance improvement in tensile-strained In/sub 0.5/Al/sub 0.5/As/In/sub x/Ga/sub 1-x/As/In/sub 0.5/Al/sub 0.5/As metamorphic HEMT

This paper proposes a In/sub 0.5/Al/sub 0.5/As/In/sub x/Ga/sub 1-x/As/In/sub 0.5/Al/sub 0.5/As (x=0.3-0.5-0.3) metamorphic high-electron mobility transistor with tensile-strained channel. The tensile-strained channel structure exhibits significant improvements in dc and RF characteristics, including extrinsic transconductance, current driving capability, thermal stability, unity-gain cutoff frequency, maximum oscillation frequency, output power, power gain, and power added efficiency.     

Morphological and electrical characterization of SixCryCzBv thin films

Si_xCr_yC_zB_v thin films with several compositions have been studied for integration of high precision resistors in 0.8 μm BICMOS technology. These resistors, integrated in the back-end of line, have the advantage to provide high level of integration and attractive electrical behavior in temperature, for analog devices. The film morphology and the structure have been investigated through transmission electron microscopy analysis and have been then related to the electrical properties on the base of the percolation theory. According to this theory, and in agreement with experimental results, negative thermal coefficient of resistance (TCR) has been obtained for samples with low Cr content, corresponding to a crystalline volume fraction below the percolation threshold.Samples with higher Cr content exhibit, instead, a variation of the TCR as a function of film thickness: negative TCR values are obtained for thickness lower than 5 nm, corresponding to a crystalline volume fraction below the percolation threshold; positive TCR are obtained for larger thickness, indicating the establishment of a continuous conductive path between the Cr rich grains. This property seems to be determinant in order to assure the possibility to obtain thin film resistors almost independent on the temperature.     

Very low-noise Al/sub 0.3/Ga/sub 0.7/As/Ga/sub 0.65/In/sub 0.35/As/GaAs single quantum-well pseudomorphic HEMTs

AlGaAs/GaInAs/GaAs pseudomorphic HEMTs with an InAs mole fraction as high as 35% in the channel has been successfully fabricated. The device exhibits a maximum extrinsic transconductance of 700 mS/mm. At 18 GHz, a minimum noise figure of 0.55 dB with 15.0 dB associated gain was measured. At 60 GHz, a minimum noise figure as low as 1.6 dB with 7.6 dB associated gain was also obtained. This is the best noise performance yet reported for GaAs-based HEMTs.<>     

A 12 /spl times/ 12 In/sub 0.53/Ga/sub 0.47/As-In/sub 0.52/Al/sub 0.48/As avalanche photodiode array

We report a 12 /spl times/ 12 In/sub 0.53/Ga/sub 0.47/As-In/sub 0.52/Al/sub 0.48/As avalanche photodiode (APD) array. The mean breakdown voltage of the APD was 57.9 V and the standard deviation was less than 0.1 V. The mean dark current was /spl sim/2 and /spl sim/300 nA, and the standard deviation was /spl sim/0.19 and /spl sim/60 nA at unity gain (V/sub bias/ = 13.5 V) and at 90% of the breakdown voltage, respectively. External quantum efficiency was above 40% in the wavelength range from 1.0 to 1.6 /spl mu/m. It was /spl sim/57% and /spl sim/45% at 1.3 and 1.55 /spl mu/m, respectively. A bandwidth of 13 GHz was achieved at low gain.     

Comparison between Pt/TiO2/Pt and Pt/TaOX/TaOY/Pt based bipolar resistive switching devices

Nonvolatile memories have emerged in recent years and have become a leading candidate towards replacing dynamic and static random-access memory devices. In this article, the performances of TiO₂ and TaO₂ nonvolatile memristive devices were compared and the factors that make TaO₂ memristive devices better than TiO₂ memristive devices were studied. TaO₂ memristive devices have shown better endurance performances (10⁸ times more switching cycles) and faster switching speed (5 times) than TiO₂ memristive devices. Electroforming of TaO₂ memristive devices requires~4.5 times less energy than TiO₂ memristive devices of a similar size. The retention period of TaO₂ memristive devices is expected to exceed 10 years with sufficient experimental evidence. In addition to comparing device performances, this article also explains the differences in physical device structure, switching mechanism, and resistance switching performances of TiO₂ and TaO₂ memristive devices. This article summarizes the reasons that give TaO₂ memristive devices the advantage over TiO₂ memristive devices, in terms of electroformation, switching speed, and endurance.