稀土配合物分子组装及其性质研究

分子组装技术是一种在分子水平上进行的有序薄膜组装技术,包括Langmuir-Blodgett(LB)膜技术及自组装技术.该论文中,对稀土配合物及稀土杂多化合物的分子组装进行了系统的研究,取得了一些令人感兴趣的研究结果:合成了Na<,9>EuW<,10>O<,36>,Na<,9>DyW<,10>O<,36>,Na<,9>SmW<,10>O<,36>,K<,13>Eu(SiW<,11>O<,39>)<,2>,K<,13>Eu(GeW<,11>O<,39>)<,2>,K<,15>Eu(BW<,11>O<,39>)<,2>等稀土多金属氧酸盐,用LB膜技术将其组装入双十八烷基二甲基溴化铵(DODA)和十八胺(ODA)分子中,得到稀土杂多化合物LB膜.以稀土离子为亚相,制备了邻十六酰基苯甲酸-稀土(铽和铕)和对十六烷氧基苯甲酸铽LB膜.以1,2-二羟基苯-3,5-二磺酸铽(Tiron-Tb)为亚相,制备了DODA/Tiron-TbLB膜.以3-氨丙基三乙氧基硅烷为前驱体,制备了Na<,9>EuW<,10>O<,36>,Na<,9>DyW<,10>O<,36>的自组装膜.荧光光谱研究表明,在自组装膜中配体能将能量有效地传递给稀土离子.

CoMoK/γ-Al_2O_3类催化剂的研究

钴离子在γ-Al_2O_3上的吸附等温线符合Langmuir等温式，而钼的吸附等温线符合Freundlich等温式。在等孔体积法制备催化剂时，低PH下由于Al_2O_3吸附钼较多而对钴的吸附较少导致钴、钼在颗粒中分布不均；在高PH值下，由于钼的吸附量锐减，可用共浸法得到钴、钼分布均匀的催化剂。K_2CO_3在均匀型CoMo/Al_2O_3催化剂上的吸附等温线符合Langmuir等温式，虽然吸附量较大，但在浸渍液中今是足够时，等孔体积法也能得到均匀分布的结果。Co/Al_2O_3氧化态催化剂中存在和Al_2O_3表面作用的Co_3O_4及表面Co~(2+)离子；Co~(2+)/Al_2O_3中，K~+的存在减弱了Al_2O_3表面上的Co~(2+)和表面的作用，有是于Co~(2+)的还原和硫化。Mo/Al_2O_3催化剂中Mo以+6价的形式存在于Al_2O_3表面上，Al~(3+)对表面上Mo的极化作用Mo~(6+)在低温易于被部分还原，Mo-o-Al键作用较强，使Mo的完全还原又比MoO_3困难；K~+的存在减弱了MoK/Al_2O_3氧化态催化剂中的Mo-o-Al键强度，有助于Mo的深度还原和硫化。Co, Mo水溶液等孔体积共浸制备的氧化态CoMo/Al_2O_3催化剂中，存在CoMoO_4，并有利于Co, Mo硫化为Co_9S_8和MoS_2；CoMoK/Al_2O_3氧化态催化剂中，K~+的存在破坏了催化剂中CoMoO_4结构，被置换出的Co~(2+)和Al_2O_3表面发生一定作用使Co的硫化程度降低；当K_2CO_3在催化剂中含量小于15wt%时，Mo的硫化随K~+含量增加而增大，但当K_2CO_3在催化剂中含量高于15wt%，Mo的硫化程度随K~+含量增加而微有减少。CoMoK/Al_2O_3, CoMo/Al_2O_3, MoK/Al_2O_3, Mo/Al_2O_3, CoK/Al_2O_3, Co/Al_2O_3催化剂在H_2S/H_2的TPS过程中，H_2S 对活性组份起硫化和还原作用，H_2仅仅是还原了反应中生成的单质S。

蟾蜍皮肤活性蛋白与多肽的研究

近年来，我们致力于蟾蛛（Bufo andrewski）皮肤活性组份的研究，构建了缥蛛皮肤cDNA文库，检测了蟾蛛皮肤分泌液中多种生物活性，进一步纯化得到了四个新的生物活性蛋白：溶菌酶、抗爱滋病毒蛋白以及两个丝氨酸蛋粼酶抑制剂，并，简述如下；I、第三章报导了我们从蟾蛛皮肤分泌液中分离得到的一个谊薇酚犷杰女呱BA一娜"zym"）·BA一lvs"Zym"经5DS一PAGE检测为一条带，其分子量约为巧k珍。·它是一个高效的溶菌酶，每毫克蛋白的溶菌活性为2．7xl护俪ts，还能抑制革兰氏阳性菌（金黄色葡萄球菌Slaj，匆褚ococcusaureus）和革兰氏阴性菌（大肠杆菌Esch邵ichiacoli）生长，其最小抑菌浓度（MIC）分别为1．36拼M和84并M。使用PCR筛选法，我们从蟾蛛皮肤c溯A文库中克隆得到编码BA一lyso即me的cDNA序列。BA一lysozymeN末端测序和肤质量图谱确认了蛋白和基因的网一性。它的蛋白全序列与鸡溶菌酶的相似性为5氏5％。系统发育分析显示，与其最相似的是来源于海龟的溶菌酶。11、第四章介绍了我们从蟋蛛皮肤分泌液中分离得到的一个新的抗lllV蛋白，命名为BAS一AH。BAS一AH是一个分子量为63kD。的单链蛋白，每摩尔蛋白质含有0．89摩尔血红素辅基。BAS一AH对人T淋巴细胞系CS166细胞的毒性（CCS。）为9．5尽M。BAs一AH具有较强的抗HIV活性，它对HIV感染和复制具有剂量依赖抑制效应，其选择指数（CCso／Ecs。）分别为14．4和11．4·BAS一麟J也能抑制HIV的逆转录酶，其1C5（）为L32冬以。BAs一AH的N末端氨基酸为NA以KADvIGKIsILLGQDI』slvAAM，与己知的抗Hlv蛋白没有同源性·表明它可能是一个新的抗川v蛋自。BAs一AH没有检测到抗菌活性、蛋自酶水解活性、胰蛋自酶抑制剂活性、L一氨基酸氧化酶活性和过氧化氢酶活性。班、第五伞报导了我们通过离子交换、分子筛和反向层析，从蟾赊皮肤中分离得到的一个新的胰蛋白酶抑制剂，命名为BATI。BATI是一个单链糖蛋自·其分子量为22kD。。它是吵～个热稳定的竞争性的抑制剂，能有效抑制胰蛋自酶·其抑制常数凡为14nM。B灯I对凝血酶、弹性蛋白酶以及糜蛋白酶都没有抑制作用。BATI的N末端序列为El犯ITD，不同于其它物种来源的蛋白酶抑制剂。W、第六章介绍了蟾蛛皮肤分泌液中纯化得到的另外一个蛋白酶抑制剂（命名为baserpin）。与上述BATI不同的是，basel咖n不可逆地抑制多种蛋白酶。它是一个分子量约为60kDa的单链糖蛋白，除了能抑制胰蛋白酶，还能有效抑制糜蛋白酶和弹性蛋白酶。它抑制上述三种酶的二级反应常数（编）分别为4．6x1护M一，s一l、8．9》1护M一15一I以及6．8xl护M一ls一l。BaserPin是第一个来源于两栖类皮肤的不可逆抑制剂，其N末端氨基酸序列为HTQYPDILIAKPxDK，与其它物种来源的蛋白酶抑制剂不同。本论文综述了蟾蛛皮肤中的活性组份，报导了我们近年来研究蟾蛛皮肤活性蛋白与多肤的进展，分四章详细介绍了蟾蛛皮肤中纯化得到的四个活性蛋白。BA一lysozyme是两栖类动物中第一个得到蛋白质全序列的溶菌酶，能有效抑制革兰氏阳性菌和革兰氏阴性菌生长；BA象AH是一个含血红素辅基的抗HIV蛋白，其独特的理化性质和功能证明它是一个新的抗病毒蛋白。根据所鉴定的性质判断，BATI和bos仰in分别属于竞争性抑制剂和不可逆抑制剂。其中，base印in是第一个从两栖类皮肤中分离得到的不可逆抑制剂。

Polycrystalline silicon thin films and solar cells prepared by rapid thermal CVD

Polycrystalline silicon (poly-Si) films(similar to 10 mu m) were grown from dichlorosilane by a rapid thermal chemical vapor deposition (RTCVD) technique, with a growth rate up to 100 Angstrom/s at the substrate temperature (T-s) of 1030 degrees C. The average grain size and carrier mobility of the films were found to be dependent on the substrate temperature and material. By using the poly-Si films, the first model pn(+) junction solar cell without anti-reflecting (AR) coating has been prepared on an unpolished heavily phosphorus-doped Si wafer, with an energy conversion efficiency of 4.54% (AM 1.5, 100 mW/cm(2), 1 cm(2)).

Kinetics of dissociative water adsorption on stepped Si(001), on Si(115), Si(113), Si(5,5,12) and Si(112)

We present photoelectron spectroscopic and low energy electron diffraction measurements of water adsorption on flat Si samples of the orientations (001), (115), (113), (5,5,12) and (112) as well as on curved samples covering continuously the ranges (001)-(117) and (113)-(5,5,12)-(112). On all orientations, water adsorption is dissociative (OH and H) and non-destructive. On Si(001) the sticking coefficient S and the saturation coverage Theta(sat) are largest. On Si(001) and for small miscuts in the [110]-azimuth, S is constant nearly up to saturation which proves that the kinetics involves a weakly bound mobile precursor state. For (001)-vicinals with high miscut angles (9-13 degrees), the step structure breaks down, the precursor mobility is affected and the adsorption kinetics changed. On (115), (113), (5,5,12) and (112), the values of S and Theta(sat) are smaller which indicates that not all sites are able to dissociate and bind water. For (113) the shape of the adsorption curves Theta versus exposure shows the existence of two adsorption processes, one with mobile precursor kinetics and one with Langmuir-like kinetics. On (5,5,12), two processes with mobile precursor kinetics are observed which are ascribed to adsorption on different surface regions within the large surface unit cell. From the corresponding values of S and Theta(sat), data for structure models are deduced. (C) 1997 Elsevier Science B.V.

Effect of temperature on implant isolation characteristics of AlGaAs/GaAs multilayer heterojunction structure

Thermally stable high-resistivity regions have been formed using hydrogen ion implantation at three energies (50, 100, and 180 keV) with three corresponding doses (6 X 10(14) 1.2 X 10(15), and 3 X 10(15) cm(-2)), oxygen implantation at 280keV with 2 X 10(14) cm(-2) as well as subsequent annealing at about 600 degrees C for 10-20s, in AlGaAs/GaAs multiple epitaxial heterojunction structure. After anncaling at 600 degrees C, the sheet resistivity increases by six orders more of magnitude from the as-grown values. This creation of high resistivity is different from that of the conventional damage induced isolation by H or O single implantation which becomes ineffective when anneal is carried out at 400-600 degrees C and the mechanism there of is discussed.

X-ray diffraction study of GaAs/InAs/GaAs ultrathin single quantum well

Ultrathin single quantum well (about one monolayer) grown on GaAs(001) substrate with GaAs cap layer has been studied by high resolution x-ray diffractometer on a beamline of the Beijing Synchrotron Radiation Facility. The interference fringes on both sides of the GaAs(004) Bragg peak are asymmetric and a range of weak fringes in the higher angle side of the Bragg peak is observed. The simulated results by using the kinematical diffraction method shows that the weak fringe range appears in the higher angle side when the phase shift introduced by the single quantum well is very slightly smaller than m pi (m:integer), and vice versa. After introducing a reasonable model of single quantum well, the simulated pattern is in good agreement with the experiment. (C) 1996 American Institute of Physics.

Growth of GaAs on Si by using a thin Si film as buffer layer

We report a novel technique for growing high-quality GaAs on Si substrate. The process involves deposition of a thin amorphous Si film prior to the conventional two-step growth. The GaAs layers grown on Si by this technique using metalorganic chemical vapor deposition exhibit a better surface morphology and higher crystallinity as compared to the samples gown by conventional two-step method. The full width at half maximum (FWHM) of the x-ray (004) rocking curve for 2.2 mu m thick GaAs/Si epilayer grown by using this new method is 160arcsec. The FWHM of the photoluminescence spectrum main peak for this sample is 2.1 meV. These are among the best results reported so far. In addition, the mechanism of this new growth method was studied using high-resolution transmission electron microscopy.

Study of double barrier superlattice by synchrotron radiation and double-crystal x-ray diffraction

An (A1As/GaAs/A1As/A1GaAs)/GaAs(001) double-barrier superlattice grown by molecular beam epitaxy (MBE) is studied by combining synchrotron radiation and double-crystal x-ray diffraction (DCD). The intensity of satellite peaks is modulated by the wave function of each sublayer in one superlattice period. Simulated by the x-ray dynamical diffraction theory, it is discovered that the intensity of the satellite peaks situated near the modulating wave node point of each sublayer is very sensitive to the variation of the layer structural parameters, The accurate layer thickness of each sublayer is obtained with an error less than 1 Angstrom. Furthermore, x-ray kinematical diffraction theory is used to explain the modulation phenomenon. (C) 1996 American Institute of Physics.

INVESTIGATION OF C-60 SINGLE-CRYSTAL BY X-RAY-METHODS

C-60 Single crystals grown by a single-temperature-gradient technique were characterized by synchrotron radiation white beam x-ray topography and x-ray double crystal diffraction with Cu K-alpha 1 radiation on conventional x-ray source. The results show that the crystal is rather well crystallized, The x-ray topographies give an evidence of dendritic growth mechanism of C-60 Single crystal, and x-ray double crystal diffraction rocking curve shows that there are mosaic structural defects in the sample. A phase transition st 249+/-1.5% K from a simple cubic to a face centered cubic structure is confirmed by in situ observation of synchrotron radiation white beam x-ray topography with the temperature varing from 230 to 295 K.

PHOTOLUMINESCENCE SPECTRUM STUDY OF THE GAAS/SI EPILAYER GROWN BY USING A THIN AMORPHOUS SI FILM AS BUFFER LAYER

Recently, we reported successful growth of high-quality GaAs/Si epilayers by using a very thin amorphous Si film as buffer layer. In this paper, the impurity properties of this kind of GaAs/Si epilayers have been studied by using PL spectrum, SIMS and Hall measurement. Compared to a typical PL spectrum of the GaAs/Si epilayers grown by conventional two-step method, a new peak was observed in our PL spectrum at the energy of 1.462 eV, which is assigned to the band-to-silicon acceptor recombination. The SIMS analysis indicates that the silicon concentration in this kind of GaAs/Si epilayers is about 10(18) cm(-3). But its carrier concentration (about 4 x 10(17) cm(-3)) is lower than the silicon concentration. The lower carrier concentration in this kind of GaAs/Si epilayer can be interpreted both as the result of higher compensation and as the result of the formation of the donor-defect complex. We also found that the high-quality and low-Si-concentration GaAs/Si epilayers can be regrown by using this kind of GaAs/Si epilayer as substrate. The FWHM of the X-ray (004) rocking curve from this regrowth GaAs epilayer is 118 '', it is much less than that of the first growth GaAs epilayer (160 '') and other reports for the GaAs/Si epilayer grown by using conventional two-step method (similar to 200 '').

The growth and characterization of GaN grown on a gamma-Al2O3/(001) Si substrate by metalorganic vapor phase epitaxy

Wurtzite single crystal GaN films have been grown onto a gamma-Al2O3/Si(001) substrate in a horizontal-type low pressure MOVPE system. A thin gamma-Al2O3 layer is an intermediate layer for the growth of single crystal GaN on Si although it is only an oriented polycrystal film as shown by reflection high electron diffraction. Moreover, the oxide is not yet converted to a fully single crystal film, even at the stage of high temperature for the GaN layer as studied by transmission electron microscopy. Double crystal x-ray linewidth of (0002) peak of the 1.3 mu m sample is 54 arcmin and the films have heavy mosaic structures. A near band edge peaking at 3.4 eV at room temperature is observed by photoluminescence spectroscopy. Raman scattering does not detect any cubic phase coexistence.

Yellow luminescence mechanism and persistent photoconductivity in n-GaN single crystal films grown on alpha-Al2O3(0001) substrates by LP-MOCVD

Unintentionally doped and Si-doped single crystal n-GaN films have been grown on alpha-Al2O3 (0001) substrates by LP-MOCVD. Room temperature photoluminescence measurement showed that besides the bandedges, the spectrum of an undoped sample was a broad deep-level emission band peaking from 2.19 to 2.30eV, whereas the spectrum for a Si-doped sample was composed of a dominant peak of 2.19eV and a shoulder of 2.32eV. At different temperatures, photoconductance buildup and its decay were also observed for both samples.. The likely origins of persistent photoconductivity and yellow luminescence, which might be associated with deep defects inclusive of either Ga vacancy(V-Ga)/Ga vacancy complex induced by impurities or N antisite (N-Ga), will be proposed.

The influence of thickness on properties of GaN buffer layer and heavily Si-doped GaN grown by metalorganic vapor-phase epitaxy

The physical properties of low-temperature-deposited GaN buffer layers with different thicknesses grown by metal-organic vapor-phase epitaxy have been studied. A tentative model for the optimum thickness of buffer layer has been proposed. Heavily Si-doped GaN layers have been grown using silane as the dopant. The electron concentration of Si-doped GaN reached 1.7 x 10(20) cm(-3) with mobility 30 cm(2)/V s at room temperature. (C) 1998 Published by Elsevier Science B.V. All rights reserved.