Wavelength multiplexing and tuning in nano-Ag/dielectric multilayers

Multicolored optical active planes have been fabricated with magnetron sputter method coupled with selective masking technique. The plane is multilayer structured with Ag nanoparticles and TiO2 thin layer as the building blocks. It was found that the formed multilayer can be readily wavelength multiplexed by simply overlapping several nano-Ag/TiO2 layered structures, each of which may have different surface plasmon resonance wavelength. Unlike high order multiple resonances of large particles each of the multiplexing wavelengths in such a system is separately tunable. Importantly, it reveals that modification of the TiO2 layer thickness generates a fine tuning of the resonance wavelength.

Wavelength multiplexing and tuning in nano-Ag/dielectric multilayers

Multicolored optical active planes have been fabricated with magnetron sputter method coupled with selective masking technique. The plane is multilayer structured with Ag nanoparticles and TiO2 thin layer as the building blocks. It was found that the formed multilayer can be readily wavelength multiplexed by simply overlapping several nano-Ag/TiO2 layered structures, each of which may have different surface plasmon resonance wavelength. Unlike high order multiple resonances of large particles each of the multiplexing wavelengths in such a system is separately tunable. Importantly, it reveals that modification of the TiO2 layer thickness generates a fine tuning of the resonance wavelength.

多层膜组装及其电催化研究

本论文主要是利用在化学修饰电极基础上建立起来的有序分子自组装膜技术，来制备能高效催化氧还原的有机一无机复合膜以及贵金属纳米粒子膜，以达到对氧的四电子还原。具体工作为：1．金属叶琳如钻叶琳单独修饰在电极表面通常只能通过两电子还原氧生成过氧化氢。而杂多酸是一种很好的电子媒介体，对很多小分子比如过氧化氢等都有很好的催化作用。我们用杂多阴离子作为对离子制备了含金属叶琳的复合膜，由于这两种物质的协同催化作用，所制备有机一无机复合膜表现了很高的催化活性，几乎达到了氧的四电子还原。2．很早人们就发现杂多酸电聚合在电极表面在酸性介质中可以催化析氢。我们通过层层组装的方法在功能化玻碳电极表面制备SiW_(12)／CoTMPyP多层复合膜，该复合膜可以高效催化析氢，同时该多层膜又能两电子催化氧还原。3．通过在一定电位下直接还原在CoTMPyP夹层间的氯铂酸根离子，在电极表面合成了三维铂纳米粒子膜。该纳米粒子膜对氧有很高的催化作用，旋转圆盘电极实验和旋转环盘电极实验证明该铂纳米粒子膜在0.5 MH_2SO_4溶液中可以实现对氧的四电子还原。4．在裸的金电极表面成功地欠电位沉积了把纳米粒子单层膜，该纳米粒子单层膜对氧还原有很好的催化作用。在这一工作基础上，研制了DO在线监侧仪。5．通过层层组装的方法，金溶胶纳米粒子与CoTMPyP的复合膜成功地组装在各种基底上。被聚丙烯酸稳定的金纳米粒子很容易吸附在CoTMPyP上，形成非常紧密分布的纳米粒子膜。6．在多壁碳纳米管表面吸附MP-11，实现了MP-11的直接电化学，同时研究了其对氧和过氧化氢的催化作用。

INTERFACIAL REACTIONS IN THE CO/SI/GAAS AND SI/CO/GAAS SYSTEMS

The interfacial reactions between thin films of cobalt and silicon and (100)-oriented GaAs substrates in two configurations, Co/Si/GaAs and Si/Co/GaAs, were studied using a variety of techniques including Auger electron spectroscopy, x-ray diffraction, and transmission electron microscopy. The annealing conditions were 200, 300, 400, 600-degrees-C for 30 min, and rapid thermal annealing for 15 s. It was found that Si layer in the Co/Si/GaAs system acts as a barrier at the interface between Co and GaAs when annealed up to 600-degrees-C. The interfacial reaction between Co and Si is faster than that between Co and GaAs in the system of Si/Co/GaAs. The sequence of compound formation for the two metallizations studied (Co/Si/GaAs and Si/Co/GaAs) depends strongly on the sample configuration as well as the layer thickness of Si and Co (Co/Si atomic ratio). From our results, it is promising to utilize Co/Si/GaAs multilayer film structure to make a CoSi2/GaAs contact, and this CoSi2 may offer an alternative to the commonly used W silicides as improved gate metallurgies in self-aligned metal-semiconductor field effect transistor (MESFET) technologies.

Carrier relaxation and thermal activation of localized excitons in self-organized InAs multilayers grown on GaAs substrates

We have investigated the temperature dependence of photoluminescence (PL) properties of a number of self-organized InAs/GaAs heterostructures with InAs layer thickness ranging from 0.5 to 3 ML. The temperature dependence of InAs exciton emission and linewidth was found to display a significant difference when the InAs layer thickness is smaller or larger than the critical thickness around 1.7 ML. The fast redshift of PL energy and an anomalous decrease of linewidth with increasing temperature were observed and attributed to the efficient relaxation process of carriers in multilayer samples, resulting from the spread and penetration of the carrier wave functions in coupled InAs quantum dots. The measured thermal activation energies of different samples demonstrated that the InAs wetting layer may act as a barrier for the thermionic emission of carriers in high-quality InAs multilayers, while in InAs monolayers and submonolayers the carriers are required to overcome the GaAs barrier to escape thermally from the localized states.

Design and fabrication of polarization-insensitive 1550 mm semiconductor optical amplifiers

Polarization-insensitive semiconductor optical amplifiers (SOA's) with tensile-strained multi-quantum-wells as actice regions are designed and fabricated. The 6x6 Luttinger-Kohn model and Bir-Pikus Hamiltonian are employed to calculate the valence subband structures of strained quantum wells, and then a Lorentzian line-shape function is combined to calculate the material gain spectra for TE and TM modes. The device structure for polarization insensitive SOA is designed based on the materialde gain spectra of TE and TM modes and the gain factors for multilayer slab waveguide. Based on the designed structure parameters, we grow the SOA wafer by MOCVD and get nearly magnitude of output power for TE and TM modes from the broad-area semiconductor lasers fabricated from the wafer.

Self-assembled InAs quantum wires on InP(001)

Self-assembled InAs quantum wires (QWRs) embedded in In0.52Al0.48As In0.53Ga0.47As, and (In0.52Al0.48As)(2)/(In(0.53)Ga(0.47)AS)(2)-short-period-lattice matrixes on InP (001) were fabricated with molecular beam epitaxy (MBE). These QWR lines are along [110], x4 direction in the 2x4 reconstructed (001) surface as revealed with high energy electron diffraction (RHEED). Alignment of quantum wires in a multilayer structure depends on the composition of spacer layers.

Structural and infrared absorption properties of self-organized InGaAs GaAs quantum dots multilayers

Self-organized InGaAs/GaAs quantum dots (QDs) stacked multilayers have been prepared by solid source molecular beam epitaxy. Cross-sectional transmission electron microscopy shows that the InGaAs QDs are nearly perfectly vertically aligned in the growth direction [100]. The filtering effect on the QDs distribution is found to be the dominant mechanism leading to vertical alignment and a highly uniform size distribution. Moreover, we observe a distinct infrared absorption from the sample in the range of 8.6-10.7 mu m. This indicates the potential of QDs multilayer structure for use as infrared photodetector.

Influence of interdot electronic coupling on photoluminescence spectra of self-assembled InAs/GaAs quantum dots

The influence of interdot electronic coupling on photoluminescence (PL) spectra of self-assembled InAs/GaAs quantum dots (QDs) has been systematically investigated combining with the measurement of transmission electron microscopy. The experimentally observed fast red-shift of PL energy and an anomalous reduction of the linewidth with increasing temperature indicate that the QD ensemble can be regarded as a coupled system. The study of multilayer vertically coupled QD structures shows that a red-shift of PL peak energy and a reduction of PL linewidth are expected as the number of QD layers is increased. On the other hand, two layer QDs with different sizes have been grown according to the mechanism of a vertically correlated arrangement. However, only one PL peak related to the large QD ensemble has been observed due to the strong coupling in InAs pairs. A new possible mechanism to reduce the PL linewidth of QD ensemble is also discussed.

Homogeneous Epitaxial Growth of N,N '-di(n-butyl)quinacridone Thin Films on Ag(110)

The structural evolution of the ordered N-N' dibutyl-substituted quinacridone (QA4C) multilayers (3 MLs) has been monitored in situ and in real time at various substrate temperatures using low energy electron diffraction (LEED) during organic molecular beam epitaxy (MBE). Experimental results of LEED patterns clearly reveal that the structure of the multilayer strongly depends on the substrate temperature. Multilayer growth can be achieved at the substrate temperatures below 300 K, while at the higher temperatures we can only get one ordered monolayer of QA4C. Two kinds of structures, the commensurate and incommensurate one, often coexist in the QA4C multilayer. With a method of the two-step substrate temperatures, the incommensurate one can be suppressed, and the commensurate, on the other hand, more similar to the (001) plane of the QA4C bulk crystal, prevails with the layer of QA4C increasing to 3 MLs. The two structures in the multilayers are compressed slightly in comparison to the original ones in the first monolayer.

基于分布式内存数据库的HIRFL-CSR真空监控系统

This paper introduced a real-time vacuum monitor system based on multilayer Web architecture for HIRFL-CSR(Heavy Ion Research Facility of Lanzhou & Cooler Storage Ring) project in Lanzhou.It combined with COM/DCOM to develop the application layer,and developed the web layer with ActiveX and Ajax technology.It provided a facility and efficiency method for real-time control.The application shows that this system runs stably and accurately.中文文摘：简要介绍了国家"九五"重大科学工程——兰州重离子加速器冷却储存环(HIRFL-CSR)真空监控系统的总体结构,分析了在Web构架下,基于分布式内存数据库的多层真空监控系统的实现方法。采用分布式内存数据库,解决了基于Web构架的分布式实时应用环境下对系统和网络资源的消耗问题。在软件控制方面采用了统一调度,既简化了软件实现过程,又提高了系统的安全性、高效性和易维护性。该系统已成功运行。

Behavior of crystalline silicon under huge electronic excitations: A transient thermal spike description

Recent experimental works devoted to the phenomena of mixing observed at metallic multilayers Ni/Si irradiated by swift heavy ions irradiations make it necessary to revisit the insensibility of crystalline Si under huge electronic excitations. Knowing that Ni is an insensitive material, such observed mixing would exist only if Si is a sensitive material. In order to extend the study of swift heavy ion effects to semiconductor materials, the experimental results obtained in bulk silicon have been analyzed within the framework of the inelastic thermal spike model. Provided the quenching of a boiling ( or vapor) phase is taken as the criterion of amorphization, the calculations with an electron-phonon coupling constant g(300 K) = 1.8 x 10(12) W/cm(3)/K and an electronic diffusivity D-e(300 K) = 80 cm(2)/s nicely reproduce the size of observed amorphous tracks as well as the electronic energy loss threshold value for their creation, assuming that they result from the quenching of the appearance of a boiling phase along the ion path. Using these parameters for Si in the case of a Ni/Si multilayer, the mixing observed experimentally can be well simulated by the inelastic thermal spike model extended to multilayers, assuming that this occurs in the molten phase created at the Ni interface by energy transfer from Si. (C) 2009 Elsevier B. V. All rights reserved.

Melting of Au and Al in nanometer Fe/Au and Fe/Al multilayers under swift heavy ions: A thermal spike study

Knowing that Fe is sensitive to swift heavy ion irradiations whereas Au and Al are not, the behavior of nanometric metallic multilayer systems, like [Fe(3 nm)/Au(x)](y) and [Fe(3 nm)/Al(x)](y) with x ranging between 1 and 10 mn, were studied within the inelastic thermal spike model. In addition to the usual cylindrical geometry of energy dissipation perpendicular to the ion projectile direction, the heat transport along the ion path was implemented in the electronic and atomic sub-systems. The simulations were performed using three different values of linear energy transfer corresponding to 3 MeV/u of Pb-208, Xe-132 and Kr-84 ions. For the Fe/Au system, evidence of appearance of a molten phase was found in the entire Au layer, provided the Au thickness is less than 7 nm and 3 nm for Pb and Xe ions, respectively. For the Fe/Al(x) system irradiated with Pb ions, the Al layers with a thickness less than 4 nm melt along the entire ion track. Surprisingly, the Fe layer does not melt if the Al thickness is larger than 2 nm, although the deposited energy surpasses the electronic stopping power threshold of track formation in Fe. For Kr ions melting does not occur in any of the multilayer systems.

Photo- and Thermo-Chromic Study of the Ethylenediamine Trimolybdate

The ethylenediamine trimolybdate (ENTMo) can show unusually photochromic and thermochromic properties and there exists in the difference of chromic mechanisms, which has been proved in our previous work [I]. In this paper, X-ray powder diffraction (XRD), Fourier transform infrared (FTIR) and laser Raman spectroscopy (LRS) of the colored samples are characterized and analyzed in detail. The crystal structure, the inorganic skeleton and the microenvironment of center ions of the colored samples do not substantively change except distortion. The color difference of the photochromic and the thermochromic samples is discussed and that the difference of reduction sites result in their different chromic mechanisms is suggested.