The effect of pre-pattern on the morphology and growth speed of TiO2 nanotube

In this work, we presented a new method which directly acts on the surface of the Ti sheet by mechanical micro-etching using a grating ruling engine. The effect of the pre-pattern on the morphology and growth speed of TiO₂ nanostructure formed on the Ti sheet with the traditional anodization method was investigated. A novel wall structure was observed and the growth speed of TiO₂ nanotube (NT) was greatly affected by the pre-pattern. The wall structure increases the surface-to-volume ratio of the nanotube arrays. The new method provided the possibility of further optimization of fast growth of TiO₂ nanostructure and improving the efficiency of dye-sensitized solar cell (DSSC) and photocatalysis.     

Measurement of photoneutron doses in and out of high-energy X-ray beam of a SATURNE-20 medical linear accelerator by ECE polycarbonate detectors

Photoneutron contaminations in and out of high energy X-ray beams of the medical linear accelerator SATURNE 20 (CGR) of the Radiotherapy Department of Omeed Hospital in Isfahan, Iran, have been determined using 250 μm polycarbonate (PC) dosimeters, in strips or in sheets, processed by electrochemical etching (ECE) using specially designed ECE chambers to etch larger sheets. A two dimensional or topographical distribution of neutron contamination was also determined in a full size beam. The neutron dose equivalents (Hn) in the beam of 18 MV X-rays at 80 cm FSD were determined to be linear functions of X-ray dose equivalents (Hx) up to 1400 cSv. The distribution of the Hn at different X-ray doses showed bell-shape profiles with maxima at the isocenter. The ratios of dose equivalents of neutrons to those of X-rays increased as the field size increased having values of 0.22%, 0.28%, 0.31% and 0.37% for field sizes of 10×10, 20×20, 30×30, and 40×40 cm² respectively. Although such neutron dose equivalents can be corrected for patient treatment, it can cause radiation protection problems for workers where the design of the facility is not well planned.     

The growth and modification of materials via ion–surface processing

A wide variety of gas phase ions with kinetic energies from 1–10⁷ eV increasingly are being used for the growth and modification of state-of-the-art material interfaces. Ions can be used to deposit thin films; expose fresh interfaces by sputtering; grow mixed interface layers from ions, ambient neutrals, and/or surface atoms; modify the phases of interfaces; dope trace elements into interface regions; impart specific chemical functionalities to a surface; toughen materials; and create micron- and nanometer-scale interface structures. Several examples are developed which demonstrate the variety of technologically important interface modification that is possible with gas phase ions. These examples have been selected to demonstrate how the choice of the ion and its kinetic energy controls modification and deposition for several different materials. Examples are drawn from experiments, computer simulations, fundamental research, and active technological applications. Finally, a list of research areas is provided for which ion–surface modification promises considerable scientific and technological advances in the new millennium.     

电化学刻蚀法制备LaB6场发射微尖锥阵列

采用电化学刻蚀方法,成功制备出单尖的六硼化镧、钼、钨及钨铼合金场发射冷阴极尖锥,并对这几种场发射单尖锥阴极的电子发射性能进行了测试比较.结果表明,LaB₆作为场发射阴极,具有良好的发射性能和稳定性.在〈111〉面单晶LaB₆基片上,用PECVD法沉积非晶硅作掩膜,制备出具有一定高度的LaB₆微尖锥场发射阵列,结果发现,LaB₆基底较为平整,尖锥阵列呈现出各向异性.该结论对LaB₆材料在场发射阴极方面的进一步研究具有重要的指导意义.     

激光诱导直接化学光刻

本文利用Ar~+激光倍频257.3nm进行扫描蚀刻Si、GaAs和Zn片,获得的最小光刻线宽为1.2μm,给出蚀刻深度与光强/扫描速度的关系曲线等参量,首次利用光刻技术估计卤素自由基的扩散系数、自由路程以及激光聚焦光斑大小,以及观察到阈值现象。     

基于表面重建螺旋型铂铱电极的葡萄糖生物传感器

通过对螺旋型铂铱电极表面进行化学腐蚀和电化学沉积铂纳米粒子实现电极表面的重建和优化,研究了螺旋型铂铱电极在不同腐蚀时间和电沉积时间下的形貌及对过氧化氢(H2O2)的催化活性.对表面重建的工作电极涂覆氧化酶和半透膜,制备出了铂纳米粒子/葡萄糖氧化酶/环氧聚氨酯酶电极,并将其用作葡萄糖传感器的工作电极.传感器计时电流检测结果表明,表面重建后的酶电极传感器对葡萄糖的检测范围扩大为2~45 mmol/L,优于裸铂铱酶电极传感器,电流响应值和灵敏度得到明显提升,同时传感器还具有良好的稳定性和选择性.     

不同气体环境下532nm激光诱导硅表面形貌的研究

研究了在不同气体环境下,利用532 nm Nd∶YAG纳秒脉冲激光累积辐照单晶硅表面形成的微结构,结果表明,在其他条件相同,背景气体不同的情况下,背景气体对硅表面形貌的形成起着重要的作用。具体分析了真空、N2和SF6 3种环境气氛下形成的微结构,结果显示,在SF6中形成的锥形微结构的数密度比在N2和真空中的大,并且锥形具有更大的纵横比;在N2、真空和SF6中形成的微结构尺寸依次减小。SF6气氛下,激光辅助化学刻蚀的效率比在真空和N2气氛中的高。另外,辐照区域边缘有波纹微结构形成,分析认为,该微结构的形成是由表面张力波的冷却导致的。     

Loss reduction in silicon nanophotonic waveguide micro-bends through etch profile improvement

Single mode silicon photonic wire waveguides allow low-loss sharp micro-bends, which enables compact photonic devices and circuits. The circuit compactness is achieved at the cost of loss induced by micro-bends, which can seriously affect the device performance. The bend loss strongly depends on the bend radius, polarization, waveguide dimension and profile. In this paper, we present the effect of waveguide profile on the bend loss. We present waveguide profile improvement with optimized etch chemistry and the role of etch chemistry in adapting the etch profile of silicon is investigated. We experimentally demonstrate that by making the waveguide sidewalls vertical, the bend loss can be reduced up to 25% without affecting the propagation loss of the photonic wires. The bend loss of a 2 μm bend has been reduced from 0.039dB/90° bend to 0.028dB/90° bend by changing the sidewall angle from 81° to 90°, respectively. The propagation loss of 2.7 ± 0.1dB/cm and 3 ± 0.09dB/cm was observed for sloped and vertical photonic wires respectively was obtained.     

高功率垂直腔面发射激光器的湿法腐蚀工艺

为提高高功率垂直腔面发射激光器(VCSEL)光电性能,对氧化限制型高功率VCSEL湿法腐蚀工艺进行了实验研究。实验中采用H₃PO₄系溶液替代以往制备此类器件常用的H₂SO₄系溶液作为高功率VCSEL外延片的腐蚀液,利用扫描电镜(SEM)研究了腐蚀后外延片氧化窗口的腐蚀形貌变化与腐蚀液浓度的关系,消除了以往采用H₂SO₄系溶液腐蚀时,高功率VCSEL氧化层侧壁出现的"燕尾"结构;通过改变湿法腐蚀工艺的外部温度条件和腐蚀液的浓度配比,实验研究了高功率VCSEL湿法腐蚀速率规律,最后得出了制备高功率VCSEL时湿法腐蚀工艺的最佳外部温度条件与腐蚀液的最佳浓度配比。