表面改性FeS纳米微粒的结构表征

采用表面改性的方法，以双十八烷基二硫代磷酸盐(DDP)为表面改性剂。制备了双十八烷氧基二硫代磷酸盐(DDP)表面改性的FeS纳米微粒。采用TEM。DSC，XRD和FTIR对表面改性FeS纳米微粒进行结构分析。结果表明，表面改性FeS纳米微粒是由DDP表面改性层和FeS纳米核心所构成，微粒尺寸在4nm～6nm之间。DDP表面改性FeS纳米微粒在氯仿、苯和甲苯等有机溶剂中都具有良好的分散性。     

基于表面等离子体的微纳光刻技术

首先介绍了光刻技术的发展及其面临的挑战。随着纳米加工技术的发展,纳米结构器件必将成为未来集成电路的基础,而纳米光刻技术是纳米结构制作的基础,基于表面等离子体的纳米光刻作为一种新兴技术有望突破45nm节点从而极大提高光刻的分辨力。介绍了表面等离子体的特性,对表面等离子体(SPs)在光刻中的应用作了回顾和分析,指出在现有的利用表面等离子体进行纳米光刻的实验装置中,或采用单层膜的超透镜(Superlens),或采用多层膜的Super-lens,但都面临着如何克服近场光刻这一难题;结合作者现有课题分析了表面等离子体光刻的发展方向,认为结合多层膜的远场纳米光刻方法是表面等离子体光刻的发展方向。     

高放电容量二氧化锰纳米材料的水热合成及微结构表征

利用表面活性剂辅助水热反应合成了二氧化锰纳米棒束和纳米片状结构;分析讨论了表面活性剂分子结构对纳米粒子微观形貌的影响。聚乙二醇的长链结构有助于一维纳米结构的形成,阴离子型表面活性剂十六烷基苯磺酸钠通过配合物的方式影响纳米材料的生长。用TEM、SEM对纳米材料进行微结构表征,进一步探讨了其对材料放电性能的影响。     

硅基太阳电池的表面纳米织构及制备

综述了用于硅基太阳电池高效陷光的四种表面纳米织构,即金属纳米颗粒、纳米线、纳米锥和纳米孔。相对于其他三种表面纳米织构,纳米孔具有更好的结构特性和陷光能力。详细介绍了各种表面纳米织构的制备方法,如金属薄膜退火、金属诱导化学腐蚀、干法刻蚀、深紫外光刻和纳米球光刻等。通过表面纳米织构提高效率是太阳电池领域的重点研究内容。表面纳米织构以其优异的光电特性,将在未来高效光伏器件中得到重要应用。     

Au纳米颗粒的形状和尺寸对表面等离子体的影响

通过调控Au纳米颗粒的形状和尺寸,研究了Au纳米颗粒的形状和尺寸与表面等离子体之间的关系。通过直流磁控溅射的方法在外延片上溅射Au薄膜,并采用快速热退火和常规热退火两种方式对其进行热退火,制备出Au纳米颗粒。使用不同热退火方式、不同热退火温度及不同Au薄膜厚度来改变Au纳米颗粒的形状和尺寸,并对Au纳米颗粒的表面形貌及它的消光谱进行了分析,对比了不同形貌的Au纳米颗粒对表面等离子体共振特性的影响。实验结果表明,使用普通热退火制备的Au纳米颗粒形状接近球体,而使用快速热退火得到的Au纳米颗粒的形状更接近棒体;随着热退火温度的升高,表面等离子体的共振波长发生红移;随着Au薄膜厚度的增加,表面等离子体的共振波长也发生红移。     

纳米机械加工与材料表面性质研究

纳米科技的发展和应用涉及纳米器件的加工、制作以及加工表面特征、性质和功能等研究。获得能够控制在微小区域的纳米加工技术手段、能对不同材料进行纳米加工以及能对过程和加工表面进行检测分析等是十分重要的。本文结合扫描探针显微镜和金刚石超精密加工技术，对金刚石纳米切削展开实验研究。实验表明，结合扫描探针显微技术直接使用金刚石刃具进行材料的纳米量级机械加工，能够适应对不同材料微去除加工的要求，可同时对加工表面、机械加工机理以及表面的加工力学性能等进行综合研究，是一种良好的纳米加工方法。     

络合剂DTPA对纳米磁性Fe_3O_4粒子的表面改性研究

采用表面化学修饰法由络合剂DTPA对纳米磁性Fe3O4粒子进行表面化学修饰改性,制备出具有表面螯合性能的纳米磁性Fe3O4/DTPA复合粒子。用多种分析手段对复合粒子进行了性能表征。结果表明,螯合剂DTPA对纳米磁性Fe3O4粒子进行了有效的表面修饰,通过化学键合牢固地结合在粒子表面,不仅提高了粒子的抗氧化性和耐候性,而且使该复合粒子对多种金属粒子具有螯合性能。     

聚酰亚胺薄膜表面微纳米尺度下电荷特性的研究

利用静电力显微镜(electrostatic force microscope,EFM)在微纳米尺度下对聚酰亚胺薄膜表面的电荷起因及特性进行研究.采用Dimension 3100型扫描探针显微镜的导电探针摩擦聚酰亚胺薄膜表面,在薄膜微纳米区域内产生电荷分布.通过静电力显微镜对微纳米区域产生的电荷进行表征,得出探针摩擦速度、探针电压对表面电荷的极性、密度、区域分布有很大的影响.同时也为微纳米尺度下探索聚合物绝缘材料表面电荷生成规律和机理提供了一个新的研究方法和途径.     

表面等离子体受激辐射放大领结型纳米天线的SERS单分子探测(英文)

基于表面等离激子受激辐射放大原理,提出了一种应用于表面增强拉曼散射(SERS)单分子探测的领结型纳米天线结构。采用有限元方法(FEM)研究其局域表面等离子体共振(LSPR)和SERS特性。结果表明,该领结型纳米天线的局域表面等离子体共振强度和局域电场强度得到明显的增强,其散射截面为非表面等离激子受激辐射放大领结型纳米天线的1.1×104倍,局域电场强度为1×102倍。同时,该领结型纳米天线的表面增强拉曼散射增强因子最大达到1016,足以进行精确的单分子探测;整个纳米天线表面的增强因子也可达到1012,足以应用于单个生物分子的探测。     

SOI纳米光波导表面粗糙度的研究进展

SOI纳米光波导表面粗糙度会显著增加波导散射损耗,降低表面粗糙度是其在许多方面应用中亟待解决的关键问题之一。首先介绍了表面粗糙度概念,总结了表面散射损耗理论方面的研究进展。随后回顾了多种SOI纳米光波导表面粗糙度测量方法,以及在表面形貌表征中存在的问题。此外,还对几种波导表面光滑工艺进行介绍,并结合具体的工作对光波导表面粗糙度各方面研究进展进行了总结。     

宽带KrF激光抽运SF6受激布里渊散射的脉宽稳定性

从理论和实验上对利用宽带KrF激光抽运SF6产生的受激布里渊散射(SBS)的脉宽稳定性进行了研究。获得了受激布里渊散射脉宽稳定性随抽运功率密度稳定性、抽运脉宽稳定性及介质气压变化的规律。发现受激布里渊散射脉宽的稳定性与抽运激光的稳定性直接相关,抽运激光的稳定性越好,获得的受激布里渊散射脉宽相对稳定性也越好。抽运光脉宽和能量的不稳定都会造成所产生的受激布里渊散射脉宽不稳定。在较低抽运功率密度情况下抽运光脉宽和能量的波动对受激布里渊散射脉宽稳定性的影响都不可忽略,但在较高抽运功率密度情况下受激布里渊散射脉宽稳定性主要受抽运光脉宽波动的影响。对结果进行了分析和讨论,获得脉宽稳定性较好的受激布里渊散射输出的条件是,使用脉宽稳定性较好的抽运光和在保证没有其他非线性效应产生的情况下,尽可能提高抽运光的功率密度和介质气压。     

Simultaneous compression and amplification of ultrashort pulses atMHz repetition rates

The authors report simultaneous compression and chirped pulse amplification at megahertz repetition rates of ultrashort pulses using a cavity-dumped dye laser with a pumping argon ion laser as the amplifier. In a single stage, the pulse is compressed by a factor of 25 and the energy per pulse is simultaneously increased by a factor of 2, without reducing the repetition rate. Starting with a pulse that has a duration of 4.3 ps and a peak power of 5.8 kW, a pulse with a duration of 170 fs and a peak power of 294 kW is obtained. A second stage of pulse compression is used to obtain a broadband pulse with a duration >~50 fs and a peak power of ~100 kW at 2 MHz     

The effect of pulse walkoff on stimulated Raman scattering in fibers

We have experimentally investigated stimulated Raman scattering in single-mode fibers in the regime of large Raman Stokes pulse walkoff from the pump pulse by the effect of group-velocity dispersion. Measurements are made with 36 ps duration pulses at 532 nm produced from a frequency-doubled and harmonically mode-locked Nd:YAG laser. We find that for 20 percent conversion, the Raman output is produced about two walkoff lengths into the fiber as a pulse of approximately the same duration as the input pulse. We also find that the Raman pulse is produced with a strong frequency chirp.     

Propagation of a chirp radio pulse in isotropic plasma

The problem of space-time deformation of a chirp radio pulse propagating in cold isotropic collisional plasma is solved analytically. Pulses with rectangular and biexponential initial envelopes are considered as examples to show that, as the covered distance grows, a chirp pulse is at first compressed and then broadened and, simultaneously, the linear increase of the instantaneous frequency observed within the pulse duration changes into an approximately linear decrease. The distance at which a chirp pulse is compressed to the minimum possible duration is estimated, and the effect of absorption on the current shape of the pulse envelope is analyzed.     

Recruitment data for nerve cuff electrodes: implications for designof implantable stimulators

Recruitment characteristics of nerve cuff electrodes implanted in four cats for five months were measured. Monopolar, bipolar, and tripolar configurations were considered. Approximately twice the current was required to achieve a given response using the tripolar configuration as compared with monopolar stimulation. Bipolar stimulation also required more current than monopolar stimulation. Using the recruitment data, a number of strategies for modulating muscle tension were considered. It was shown that both pulse amplitude and pulse duration should be software-selectable to achieve adequate control of muscle tension when using either pulse amplitude modulation or pulse duration modulation. When using pulse amplitude modulation, it was found to be desirable to operate at a low pulse duration in the high end of the allowable range for pulse amplitude. For pulse duration modulation, one should operate at a low pulse amplitude in the high end of the allowable range for pulse duration. The effect of pulse amplitude and pulse duration step size on the maximum step change in muscle tension and the linearity of the recruitment curves were examined. The use of logarithmic steps in the modulation parameter was examined and was shown to result in improved controllability and linearity.     

激光脉冲时域特性与探测器响应关系探讨

针对激光与光电探测器两种相互作用方式,选择四种常见的激光脉冲波形,建立简单数学模型,计算了光电探测器接收到的激光脉冲能量和脉冲激光在探测器上的有效持续时间,并据此分析激光脉冲时域特性与光电探测器的响应关系.计算结果表明,不同的激光脉冲波形引起的光电探测器的响应会有差异,并且,相对较长的大能量激光脉冲波形可能在探测器中引起较好的作用效果.     

长腔被动锁模掺镱光纤激光器的方波脉冲产生

报道了一种基于非线性光纤环形镜(NOLM)、工作在耗散孤子共振(DSR)区的长腔被动锁模掺镱光纤激光器,该激光器谐振腔的总长度约为1502 m,可以输出重复频率为133.18 kHz的高能量方波脉冲,且输出脉冲的宽度和单脉冲能量均随泵浦功率的增大而呈线性增大。当泵浦功率增大到414.47 mW时,输出的方波脉冲具有最大宽度(761.6 ns),同时单脉冲能量达到了最大值(60.2 nJ)。通过改变NOLM中单模光纤的长度,进一步研究了谐振腔长度对输出方波脉冲特性的影响,结果表明:谐振腔越长,所得DSR方波脉冲越宽,脉冲峰值功率越低。     

激光脉宽对光学薄膜元件热损伤的影响

纳秒量级及以下脉宽激光致光学薄膜元件的损伤研究持续了几十年,但纳秒量级以上脉宽却很少提及。因此,针对10 ns~1 ms量级区间不同脉宽激光辐照光学薄膜元件产生的热损伤进行了研究,计算了高反膜、增透膜和干涉滤光片三种典型光学薄膜元件的温度场分布,并分析了其激光热损伤特性。结果表明,对于长脉宽激光,热扩散深度大,薄膜损伤的电场效应被削弱,热传导效应在损伤中占据主导地位,损伤可至基底;短脉宽激光损伤对薄膜内部的电场分布更为敏感,损伤发生在温度最高值附近的膜层区域。进而开展了10 ns与1 ms脉宽激光致光学薄膜元件的损伤实验,损伤阈值及形貌特征与温度场计算结果显示的热损伤特性相符。     

Impulsive noise measurements and characterization in a UHF digitalTV channel

This paper presents the results of a study covering measurement and characterization of the wide-band impulsive noise present in a digital TV radio channel. Measurements were conducted at a frequency of 762 MHz in different outdoor and indoor environments using vertical and horizontal polarization. The measurement system was built on commercial equipment only. The calibration process, which is an important stage of this kind of measurements, is described. To analyze the measurements the impulsive noise has been modeled as a pulse train where the pulse amplitude, pulse duration and elapsed time between pulses are considered random variables. It has been found that the pulse duration and elapsed time between pulses is not dependent on the antenna polarization while the pulse amplitude is, especially in the case of the noise generated by a fluorescent lamp. It has also been found that the pulse duration of the noise measured in the outdoor environments presents some clustering features and is correlated with the pulse amplitudes. This correlation may be caused by a RF noise bandwidth that is larger than the bandwidth of the measurement system. The noise in busy streets presents larger pulse durations, larger amplitude, and shorter elapsed time between pulses that the noise measured in a pedestrian area. Several statistical tests have been done to find the distribution function that best fits these random variables. Power Rayleigh, lognormal, exponential, Poisson, and Gamma distributions have been tested. According to the assessment carried out, none of the distribution functions is adequate to model the pulse amplitudes or the elapsed time between pulses, while the pulse duration seems to be Gamma distributed     

微细群孔电解加工试验研究

基于微细电解加工理论,采用微细圆柱群电极进行了微细群孔电解加工工艺试验,研究了加工电压、脉冲宽度、电解液浓度、成分等因素对群孔加工精度的影响。结果表明,减小加工电压和脉冲宽度,采用低浓度钝化性电解液可以显著提高群孔电解加工精度。研究结果对实现微细群孔结构高精度和高效率加工具有指导意义。