新型光泵浦垂直外腔面发射半导体激光器

用量子阱技术生长的半导体材料作激光增益介质,AlGaAs/GaAs对做布喇格反射镜,并以简单的平凹腔做谐振腔,半导体激光器作泵浦源,制作出了光泵垂直外腔面发射半导体激光器.在抽运功率1.5 W时,得到了中心波长1005 nm、最大输出功率40 mW的激光,光－光转换效率2.7%.     

Manipulation on human red blood cells with femtosecond optical tweezers

Different types of femtosecond optical tweezers have become a powerful tool in the modern biological field. However, how to control the irregular targets, including biological cells, using femtosecond optical tweezers remains to be explored. In this study, human red blood cells (hRBCs) are manipulated with femtosecond optical tweezers, and their states under different laser powers are investigated. The results indicate that optical potential traps only can capture the edge of hRBCs under the laser power from 1.4 to 2.8 mW, while it can make hRBCs turn over with the laser power more than 2.8 roW. It is suggested that femtosecond optical tweezers could not only manipulate biological cells, but also subtly control its states by adjusting the laser power.     

SERS光谱及电化学法研究硫脲在银电极上的吸附层结构

实验发现硫脲能在电极表面形成一吸附层并阻碍氢在电极表面的析出还原反应，此吸附层在电位约－０．６Ｖ时发生结构转变，进一步实验显示硫脲吸附层的结构在－０．９Ｖ时为疏松的，在－０．３Ｖ～－０．５Ｖ时为致密的，而在－０．８Ｖ～－０．６Ｖ时为两种结构的中间过渡态。     

MEH-PPV/ZnO纳米晶无机有机复合电致发光器件的研究

以Ⅱ一Ⅵ族无机半导体ZnO纳米颗粒为电子传输层,MEH-PPV为空穴传输层兼发光层,得到的电致发光器件比单层MEH-PPV器件的发光亮度和效率都明显提高。器件结构为ITO／MEH-PPV／ZnO／Al的电致发光光谱同单层PPV器件的光谱出现了不同,在620nm处出现了一个小的发光峰,应该是ZnO的发光。另外,双层结构器件的启亮电压由单层器件的9V降到了4V左右。由I-V曲线及发光光谱可判断出发光区域应在MEH-PPV／ZnO界面处,并且复合区域可能随着电压的变化而变化。     

BSO晶体及生长固/液边界层的拉曼光谱分析

测量了 BSO晶体在常温和高温下宏观拉曼光谱 ,据此分析晶体结构在高温下的变化规律 ,详细实时地测量了晶体在熔化和生长过程中 ,固 /液边界层以及边界层两侧的晶体和熔体的显微拉曼光谱 ,分析得出该晶体生长边界层内的结构特征 ,以及生长基元结构从熔体结构经边界层过渡到晶体结构的变化过程     

基于双尺度4分离层优化的石墨烯太赫兹宽带吸波结构

为实现对未来远程太赫兹雷达的高效对抗与隐身,针对典型太赫兹雷达工作频率设计了一种石墨烯太赫兹宽带吸波结构。宽带吸波结构以表层金属层/石墨烯层/介质层/底层金属层为基本吸波结构单元,利用遗传算法对双尺度基本吸波结构单元进行4分离层优化设计,确定宽带吸波结构的各层结构参数。仿真结果表明:宽带吸波结构在0.138 THz～2 THz频率范围内吸收效率优于80%,在0.157 THz～2 THz频率范围内吸收效率优于97.46%,典型太赫兹雷达工作频率处吸收效率均优于92.27%,满足太赫兹雷达对抗与隐身要求。     

互混型有机电致发光器件

通过共蒸镀空穴传输材料TPD和电子传输材料Alq₃,在普通双层器件的异质结界面引入了均匀互混层,并研究了互混层的厚度变化对器件光电性能的影响。互混层的引入在一定程度上改善了普通双层器件的异质结界面由于高浓度载流子积聚导致的高电场和界面缺陷对器件主要性能(效率和寿命)的负面影响。我们发现一定厚度的互混层使器件的性能有所提高。     

液态锡对低活化马氏体/铁素体钢CLF-1的腐蚀行为研究

采用背散射电子扫描显微镜、电子衍射能谱和X射线衍射等分析方法，研究了浸泡在300~700℃的液态锡(Sn)中24h后的低活化马氏体/铁素体钢CLF-1的腐蚀行为。研究结果表明，在所有测试温度下液态锡对CLF-1钢表面均有不同程度的腐蚀，主要腐蚀机制为化合溶解腐蚀。铬(Cr)以单质形式溶解沉淀，液态锡与铁在CLF-1钢表面反应生成由铁锡化合物构成的腐蚀层。当温度低于500℃时，腐蚀层厚度近似为一常量，约8μm，化学成分为FeSn₂。当温度高于500℃时，腐蚀层厚度随温度线性增加，腐蚀层呈双层结构，分别为CLF-1边界处的FeSn层和覆盖在其表面的FeSn₂层。     

Phase effects during parametric conversion in layer structures

Coupled-wave equations that describe the parametric amplification and generation of a sum frequency in a three-layer structure are studied theoretically in the constant-intensity approximation taking into account the inverse effect of the excited wave on the phase of the pumping wave. For this purpose, the approximation of constant intensity of the fundamental radiation is applied not to the layer structure as a whole but to each separately taken layer. In this case, the complex amplitudes of the interacting waves at the output of each layer are the input values of the corresponding complex amplitudes for the next layer. Analytical expressions obtained in the constant-intensity approximation for the efficiency of conversion to the sum frequency were analyzed numerically for different parameters of the problem. The efficiency of parametric amplification at a high frequency was found to depend on the intensity of the signal wave at a low frequency.     

Rate-ratio asymptotic analysis of non-premixed methane flames

The asymptotic structure of laminar, non-premixed methane flames is analysed using a reduced four-step chemical-kinetic mechanism. Chemical reactions are presumed to take place in two layers: the inner layer and the oxidation layer. In the inner layer the fuel reacts with radicals and the main compounds formed are the intermediate species CO and H₂. These intermediate species are oxidized in the oxidation layer. The structure of the oxidation layer is described by two second-order differential equations: one for CO and the other for H₂. Two limiting cases are considered. At one limit the global step CO+H₂?CO₂+H₂ is presumed to maintain partial equilibrium everywhere in the oxidation layer except in a thin layer adjacent to the inner layer. At the other limit the steady-state approximation is introduced for H₂ everywhere in the oxidation layer except in a thin layer adjacent to the inner layer. This limit, called ‘slow CO oxidation’, has not been analysed previously. The structure of the inner layer is described by two second-order differential equations: one for the fuel and the other for the H radicals. This is a significant improvement over previous models in which either a steady-state approximation is introduced for the H radicals in the inner layer, or the reaction between the fuel and radicals is presumed to be very fast. The chain-breaking elementary reaction CH₃+H+M→CH₄+M is found to have a significant influence on the structure of the inner layer and on the scalar dissipation rates at extinction. The influence of this reaction was either neglected in previous models or was included as a perturbation to the principal elementary reactions taking place to the leading order in the inner layer. Using the results of the asymptotic analysis the scalar dissipation rates at extinction are calculated at a pressure of 1 bar. They are found to agree well with those calculated numerically using a chemical-kinetic mechanism made up of elementary reactions.     

有机量子阱电致发光器件

制备了普通的有机量子阱结构,并对结构进行了表征.在此基础上,制备了量子阱结构的白光电致发光器件.在分析了制作工艺对有机量子阱结构特性可能产生的影响之后,为了减少垒、阱界面互扩散效应的影响,提出了有机掺杂量子阱的概念,即垒与阱的母体是相同材料,只是在生长垒层的过程中同时掺入少量发光剂.由于掺杂剂的浓度梯度只有百分之零点几,因此,界面互扩散的影响很小,实际上我们用这种办法制备的有机量子阱器件的亮度、效率均有明显提高.在研究了阱数对器件特性的影响之后,我们发现一般情况下,两个阱是最好的.进一步研究了阱母体材料对有机量子阱器件特性的影响,结果发现,用NPB作母体比Alq作母体更好,这时器件的效率(cd/A)在45～13V工作电压范围内变化不大.     

SrS:Ce3+薄膜蓝色交流电致发光及其特性的研究

本文采用了SnO2/Y2O3/ZnS/SrS:Ce3+/ZnS/Y2O3/Al这种多层结构制备了SrS:Ce3+薄膜器件,并得到了较亮的蓝色交流电致发光。在5KHz正弦交流电压的激发下,该器件的最大亮度为100cd/m2左右。讨论了衬底温度与薄膜结晶完整性的关系,认为衬底温度在300—400℃之间有利于获得良好的结晶状态。本文还对SrS:Ce3+薄膜的光谱特性进行了讨论,比较了CeF3和CeCl3分别掺杂时,SrS薄膜的发光特性发现CeCl3掺杂较CeF3掺杂好。同时还看到,SrS:Ce3+薄膜的ACEL亮度和效率较ZnS:Ce3+薄膜要高,认为可能的原因是SrS基质提供了一种适合Ce3+激发的环境。     

BSO晶体生长固/液边界层结构的实时观测研究

实时测量BSO晶体水平区熔法生长过程中,研究固/液边界层以及边界层两侧的晶体和熔体的显微拉曼光谱,晶体生长固/液边界层以及边界层两侧的熔体和晶体的结构特征, 生长基元结构从熔体结构经边界层过渡到晶体结构的变化过程。结果显示, BSO熔体中存在Bi₃O₄和[SiO₄]的键合结构; Bi₃O₄分子基团在固/液边界层聚合形成[BiO₇]八面体单体、多聚体,与[SiO₄]结构基团联结,在通过固／液边界层时进入格位。     

Structural characterization of titanium oxide layers prepared by plasma based ion implantation with oxygen on Ti6Al4V alloy

Ti6Al4V alloy was implanted with oxygen by using plasma based ion implantation (PBII) at pulsed voltage ranging from −10 to −50 kV with a frequency of 100 Hz. In order to maintain a lower implantation temperature, an oil cooling working table was employed. The structure of the modified layers was characterized by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The results show that the thickness of the titanium oxide layer increases significantly with the increase of implanted voltage. The structure of the modified layer changes along depth. It is found that the surface layer consists of TiO₂, and the subsurface layer is a mixing structure of TiO_2, Ti₂O₃ and TiO. There is crystalline rutile phase existing in the modified layer of sample implanted at high implanted voltage. In addition, in the outmost modified surface, aluminum present as oxidized state, and vanadium could not be detected.     

Characteristic difference between ITO/ZrCu and ITO/Ag bi-layer films as transparent electrodes deposited on PET substrate

The metallic-glass film of ZrCu layer deposited by co-sputtering was utilized as the metallic layer in the bi-layer structure transparent conductive electrode of ITO/ZrCu (IZC) deposited on the PET substrate using magnetron sputtering at room temperature. In addition, the pure Ag metal layer was applied in the same structure of transparent conductive film, ITO/Ag, in comparison with the IZC film. The ZrCu layer could form a continuous and smooth film in thickness lower than 6 nm, compared with the island structure of pure Ag layer of the same thickness. The 30 nm ITO/3 nm ZrCu films could show the optical transmittance of 73% at 550 nm wavelength. The 30 nm ITO/12 nm ZrCu films could show the better sheet resistance of 20 Ω/sq, but it was still worse than that of the ITO/Ag films. It was suggested that an alloy system with lower resistivity and negative mixing heat between atoms might be another way to form a continuous layer in thickness lower than 6 nm for metal film.     

Layered structure of epitaxial yttrium iron garnet films

The layered structure of yttrium iron garnet films, ranging in thickness from 0.7 to 4.1 μm, grown epitaxially on single-crystal gallium-gadolinium garnet substrates, was investigated by x-ray spectral microanalysis. The ferrite films were chemically etched layer by layer in a mixture of orthophosphoric and sulfuric acids at T=353–423 K. It was established that the chemical composition of the films varies over the thickness because of the nonuniform distribution of gadolinium, gallium, lead, and platinum ions; the film-substrate transitional layer and the surface layer of the film differ most greatly with respect to the composition and magnetic properties. It was shown that the thickness of the transitional layers and their negative effect on the magnetic characteristics of ferrite films decrease appreciably if at the time of immersion of the substrate and pulling of epitaxial structure out of the fluxed solution the substrate holder together with a special mixer rotate at a rate of 50 rpm and the pulling velocity is 20 cm/min. Zh. Tekh. Fiz. 69, 62–64 (December 1999)     

Temperature profile of the multilayer structure irradiated by pulsed laser

Two programs are developed to calculate the temperature profile, as well as the reflectance, transmittance and absorption of a given multilayer film structure, in order to better understand the laser energy distribution between the reflectance, transmittance and absorption in each film layer. An inorganic Blu-ray recordable disc (BD-R) structure is used as a practical demonstration of the multilayer structure. The reflectance and absorption of the BD-R structure exhibit opposite trends and oscillate repeatedly with varying lower or upper dielectric layer thickness while the rest of the film thickness remains unchanged. The energy absorption in an absorbed layer depends on the thickness of the dielectric layers, its relative position in the structure and the extinction coefficient of its optical constant. The total absorption ratio of its maximum to minimum can be over 3 when changing the lower dielectric layer thickness of the studied structure. The layer thickness acts as an energy valve to control the energy flow into the multilayer structure. The thermal profile of the multilayer film structure irradiated by a pulsed laser is calculated at different positions in the film layers with time. The calculated temperatures in the recording alloy layer exhibit linear relationship with the applied power level. The effect of the laser duration time on the temperature increase in the recording layer is significant in the first few nanoseconds and becomes saturated if the heat balance is established in the structure. The calculated temperature is consistent with the experimental recording result when the structure is recorded at 4-time BD-R recording speed.     

Adsorption and desorption of fullerene on graphene/SiC(0001)

Adsorption and desorption of fullerene on a single layer of graphene grown on SiC(0001) were investigated by photoemission spectroscopy (PES). No significant change in the band structure of graphene was observed after fullerene deposition on the graphene layer under vacuum conditions, and subsequent exposure to the air. After annealing the fullerene layer at 275 °C in a vacuum, complete desorption of fullerene was observed without any resulting damage to the graphene structure. The desorption temperature of fullerene was significantly higher than that of pentacene, indicating that fullerene layers show higher stability than pentacene as protection layers of graphene-based devices.     

Autocollimation reflection of light from the surface of corrugated waveguides with leaky modes

The diffraction of light at the corrugated surface of a layer structure was studied. We show that the excitation of the waveguide modes in a layer structure causes a significant change in the diffraction efficiency of the corrugated structure. It is found that the diffraction efficiency of a grating in the autocollimation regime may be as much as 100% with reasonable depths of the grating. The efficiency of a waveguide-grating mirror in dye lasers is experimentally demonstrated.     

对流边界层顶部光学湍流的室内模拟研究

对流边界层顶部夹卷层是边界层和自由大气之间的过渡带,夹卷层的湍流结构是其主要特征之一。由于夹卷层的位置较高,进行精细结构观测很难,对此认识较少。利用尺寸为150 cm×150 cm×60 cm室内对流水槽模拟了大气对流边界层的发生和发展。将准直光通过模拟对流边界层,根据光在湍流介质中的传输理论得到混合层顶部夹卷层的温度结构常数的特点,在夹卷层内,归一化的温度结构常数满足相同的规律;在高度0.8zi处,温度结构常数最小,随着高度增加,温度结构常数增大,zi处达最大,然后又随着高度减逐渐小,在高度1.2zi处湍流消失。在边界层顶部zi处,归一化的温度结构常数处于一定的变化范围,归一化温度结构常数处于0.08~0.3之间,这可能与夹卷层的大尺度结构有关。