High-concentration hydrogen in unintentionally doped GaN

We use nuclear reaction analysis to study hydrogen in unintentionally doped GaN, and high-concentration hydrogen, nearly 10(21) cm(-3), is detected. Accordingly, a broad but intense infrared absorption zone with a peak at 2962 cm(-1) is reported, which is tentatively assigned to the stretch mode of NH: Ga complex. The complex is assumed to be one candidate answering for background electrons in unintentionally doped GaN. (C) 1998 Elsevier Science B.V. All rights reserved.

Hydrogen-decorated lattice defects in proton implanted GaN

Several vibrational bands were observed near 3100 cm(-1) in GaN that had been implanted with hydrogen at room temperature and subsequently annealed, Our results indicate that these bands are due to nitrogen-dangling-bond defects created by the implantation that an decorated by hydrogen, The frequencies are close to those predicted recently for V-Ga-H-n complexes, leading us to tentatively assign the new lines to V-Ga defects decorated with different numbers of H atoms. (C) 1998 American Institute of Physics. [S0003-6951(98)03614-6].

纳米半导体技术

本书介绍了纳米半导体材料的定义、性质及其在未来信息技术中的地位的同时，主要介绍了纳米半导体材料制备的方法和共性关键技术，几种常用的纳米半导体材料的评价技术和应变自组装半导体量子点(线)的尺寸、密度分布、形貌、组分及结构特性的实验研究，纳米半导体材料的电子结构、光学和电学性质，基于子带跃迁的量子级联激光器的工作原理、特性和它的发展现状及其应用前景分析，最后重点介绍了纳米半导体器件及应用。本书适合于从事或对纳米半导体科学技术有兴趣的科研工作者、教师、研究生、本科生和工程技术人员阅读，有些章节可作为科普读物。

The influence of substrate nucleation on HVPE-grown GaN thick films - art. no. 684105

Thick GaN films were grown on sapphire in a home-made vertical HVPE reactor. Effect of nucleation treatments on the properties of GaN films was investigated, including the nitridation of sapphire, low temperature GaN buffer and MOCVD-template. Various material characterization techniques, including AFM, SEM, XRD, CL and PL have been used to assess these GaN epitaxial films. It was found that the surface of sapphire after high temperature nitridation was flat and showed high density nucleation centers. In addition, smooth Ga-polarity surface of epitaxial layer can be obtained on the nitridation sapphire placed in air for several days due to polarity inversion. This may be caused by the atoms re-arrangement because of oxidation. The roughness of N-polarity film was caused by the huge inverted taper domains, which can penetrate up to the surface. The low temperature GaN buffer gown at 650 degrees C is favorable for subsequent epitaxial film, which had narrow FWHM of 307 arcsec. The epitaxial growth on MOCVD-template directly came into quasi-2D growth mode due to enough nucleation centers, and high quality GaN films were acquired with the values of the FWHM of 141 arcsec for (002) reflections. After etching in boiled KOH, that the total etch-pit density was only 5 x 106 cm(-2) illustrated high quality of the thick film on template. The photoluminescence spectrum of GaN film on the MOCVD-template showed the narrowest line-width of the band edge emission in comparison with other two growth modes.

Growth of GaSb and GaInAsSb layers for thermophotovolatic cells by liquid phase epitaxy - art. no. 68411E

GaSb based cells as receivers in thermophotovoltaic system have attracted great interest and been extensively studied in the recent 15 years. Although nowadays the manufacturing technologies have made a great progress, there are still some details need to make a further study. In this paper, undoped and doped GaSb layers were grown on n-GaSb (100) substrates from both Ga-rich and Sb-rich solutions using liquid phase epitaxy (LPE) technique. The nominal segregation coefficients k of intentional doped Zn were 1.4 and 8.8 determined from the two kinds of GaSb epitaxial layers. Additionally, compared with growing from Ga-rich solutions, the growing processes from Sb-rich solutions were much easier to control and the surface morphologies of epitaxial layers were smoother. Further-more, in order to broaden the absorbing edge, Ga1-xInxAsySb1-y quaternary alloys were grown on both GaSb and InAs substrates from In-rich solutions, under different temperature respectively.

Self-assembled GaAs quantum rings by MBE droplet epitaxy

Fabrication of semiconductor nanostructures such as quantum dots (QDs), quantum rings (QRs) has been considered as the important step for realization of solid state quantum information devices, including QDs single photon emission source, QRs single electron memory unit, etc. To fabricate GaAs quantum rings, we use Molecular Beam Epitaxy (MBE) droplet technique in this report. In this droplet technique, Gallium (Ga) molecular beams are supplied initially without Arsenic (As) ambience, forming droplet-like nano-clusters of Ga atoms on the substrate, then the Arsenic beams are supplied to crystallize the Ga droplets into GaAs crystals. Because the morphologies and dimensions of the GaAs crystal are governed by the interplay between the surface migration of Ga and As adatoms and their crystallization, the shape of the GaAs crystals can be modified into rings, and the size and density can be controlled by varying the growth temperatures and As/Ga flux beam equivalent pressures(BEPs). It has been shown by Atomic force microscope (AFM) measurements that GaAs single rings, concentric double rings and coupled double rings are grown successfully at typical growth temperatures of 200 C to 300 C under As flux (BEP) of about 1.0 x 10(-6) Torr. The diameter of GaAs rings is about 30-50 nm and thickness several nm.

Corrugated surfaces formed on GaAs (331)a substrates: The template for laterally ordered InGaAs nanowires

Morphology evolution of high-index (331)A surfaces during molecular beam epitaxy (MBE) growth have been investigated in order to uncover their unique physic properties and fabricate spatially ordered low dimensional nanostructures. Atomic Force Microscope (AFM) measurements have shown that the step height and terrace width of GaAs layers increase monotonically with increasing substrate temperature in conventional MBE. However, this situation is reversed in atomic hydrogen-assisted MBE, indicating that step bunching is partly suppressed. We attribute this to the reduced surface migration length of Ga adatoms with atomic hydrogen. By using the step arrays formed on GaAs (331)A surfaces as the templates, we fabricated laterally ordered InGaAs self-aligned nanowires.

Study on surface morphology of GaN growth by MOCVD on GaN/Si(111) template

The surface morphology of GaN grown by MOCVD on GaN/Si template was studied. Rough morphology and deep pinhole defects on some surface areas of the samples were observed and studied. The formation of rough morphology is possibly related to Ga-Si alloy produced due to poor thermal stability of template at high temperature. The deep pinhole defects generated are deep down to the surface of MBE-grown GaN/Si template. The stress originated from the large thermal expansion coefficient difference between GaN and Si may be related to the formation of the pinhole defects. The surface morphology of the GaN can be improved by optimizing the GaN/Si template and decreasing the growth temperature.

Influence of band bending and polarization on the valence band offset measured by x-ray photoelectron spectroscopy

The influence of band bending and polarization on the valence band offset measured by x-ray photoelectron spectroscopy (XPS) is discussed, and a modification method based on a modified self-consistent calculation is proposed to eliminate the influence and thus increasing the precision of XPS. Considering the spontaneous polarization at the surfaces and interfaces and the different positions of Fermi levels at the surfaces, we compare the energy band structures of Al/Ga-polar AlN/GaN and N-polar GaN/AlN heterojunctions, and give corrections to the XPS-measured valence band offsets. Other AlN/GaN heterojunctions and the piezoelectric polarization are also introduced and discussed in this paper.

新型靶向性磁共振成像造影剂的合成及性质研究

磁共振成像(magnetic resonance imaging, MRI)以其分辨率高、对人体无电离辐射损伤、多参数成像等优点而得到迅速发展和广泛应用。目前，MRI已从单一形态学向分子影像学的深度发展，对医学临床和医学研究产生了巨大影响。为了提高病变部位与正常组织间信号的对比度，约30%~40%的诊断需要使用磁共振成像造影剂。它是一类能缩短成像时间、提高成像对比度和清晰度、显示组织器官功能状态的诊断用药。下一代磁共振成像造影剂的设计目标将集中在对特定组织或器官具有选择性或靶向性、高弛豫性能和减少用药剂量等方面。本论文在此领域的研究内容可归纳如下： (1) 以多糖为载体的MRI造影剂 设计合成了阿拉伯半乳聚糖修饰的Gd-DTPA配合物(Gd-DTPA-CMAG-An)和葡聚糖修饰的Gd-DTPA配合物(Gd-DTPA-CMDn-Cyst)。通过体外弛豫时间测试和体内磁共振成像实验研究了Gd-DTPA-CMAG-An弛豫性能、器官选择性、体内滞留时间和代谢情况，结合体外稳定性综合评价了其应用于临床的可能性。研究结果表明，Gd-DTPA-CMAG-An配合物在水溶液中弛豫性能为Gd-DTPA的1.4倍左右，Gd-DTPA-CMAG-A2对肝脏信号的增强效果是Gd-DTPA的2.0倍左右，并且能在较长时间内产生良好稳定的增强效果。这与肝脏表面的去唾液酸糖蛋白受体的专一性识别有关。Gd-DTPA-CMAG-A2良好的肝脏选择性和肾脏代谢能力，有望成为有前景的肝脏选择性造影剂。通过小鼠MRI实验初步评价了Gd-DTPA-CMDn-Cyst配合物造影剂对血管信号的增强作用。Gd-DTPA-CMD4-Cyst对血管产生了良好的增强效果，并且能在较长时间内对血管产生良好稳定的增强，从而有充分的时间优化成像窗口获得理想的成像效果。但造影剂在体内的分布和代谢是一个非常复杂的过程，Gd-DTPA-CMD4-Cyst在血液中的滞留情况及能否用于血管造影仍需进一步的实验证实。 (2) MnNaY 型分子筛作为胃肠道MRI造影剂 离子交换法制备了Mn2+交换的NaY分子筛MnNaY，从对造影剂的一般要求出发，对其酸性水溶液中的稳定性和离子交换选择性、体外弛豫性能和体内成像等方面进行研究，并对器官的选择性及体内滞留时间和代谢情况进行了分析，从而对其应用于临床的可能性进行了探讨。研究结果表明，MnNaY悬浮液能长时间在较低的酸性条件下保持良好的稳定性，其弛豫效率高于目前临床所用造影剂Gd-DTPA，随Mn2+的含量在NaY分子筛中的增加(3.2%~5.2%)，弛豫效率反而降低。MnNaY (3.2% Mn)对胃部具有良好的增强效果，并且能在较长时间内产生良好稳定的增强效果，有利于获得理想的成像效果。它是一种比较好的潜在口服胃肠道造影剂。 (3) 甘草酸为载体的MRI造影剂 合成了甘草酸为载体的配合物GL-(A-Gd-DTPA)3，对其体外弛豫性能和体内成像等方面进行了研究，结果表明，其在水中的弛豫效率约为目前临床所用造影剂Gd-DTPA的1.4倍，体内成像表明它能在较长时间内对大鼠肝脏产生良好稳定的增强效果，这是由于肝(实质)细胞膜表面存在GL和GA受体，Gd-DTPA 以GL为载体后具有良好的趋肝性与肝细胞靶向性。 (4) 中性的Gd-DTPA双酰胺衍生物 合成了两种中性的Gd-DTPA双酰胺衍生物Gd-DTPA-BBA和Gd-DTPA-BtBA，其弛豫效率与Gd-DTPA相近，对肝脏和肾脏具有较好的增强效果，由于这两种配合物均为电中性化合物，这样配合物溶液的渗透压值与血液的渗透压值较接近，可能更易为生物体所接受。

宽能隙半导体氮化镓的合成、相变与性质的研究

GaN是最有前途的宽能隙半导体材料之一。它具有优异的光电子特性及稳定的物理性能，因此引起了各国科研工作者的广泛兴趣，各国争相研制GaN基蓝紫光和紫外波段的光电器件，并取得了令人瞩目的结果。关于GaN的研究每年有大量的文献报道，GaN基发光二极管已经产业化。通过文献调研发现，在GaN的研究中存在一些重要的基础工作有待完成。如，GaN陶瓷体的制备，结构相变研究，材料的室温合成方法等。当前 GaN器件的研究的关键问题之一是获得高质量的GaN薄膜，而影响膜质量的关键因素是选择合适的与GaN晶格匹配和热膨胀匹配的衬底材料。GaN晶体是公认的最佳材料，但是GaN晶体制备困难，迄今为止，尚未得到足够尺寸的大单晶材料。GaN陶瓷体的制备有可能替代单晶体作为理想的衬底材料。由于GaN热稳定性差，烧结时易挥发，到目前为止，尚无合成GaN陶瓷体的报道。闪锌矿结构立方GaN具有比纤锌矿结构的GaN更容易进行P型掺杂、发光效率高的特点，因而成为该材料研究的热点问题之一。虽然己有一些立方相GaN粉末合成和膜制备的报道，但是六方纤锌矿GaN向立方闪锌矿的相变研究尚属空白。研究六方相到立方相的相变规律，有助于相变的认识及立方GaN的合成。降低GaN的合成温度对该材料的制备有重要的意义。低温合成GaN的工作已有一些报道，但室温下的合成研究尚待探索。本文通过建立高氨压合成新技术，首次实现了GaN陶瓷体的合成。利用机械合金化产生的机械力化学效应，实现了h－GaN向c－GaN的相变。利用机械力化学反应方法完成了非晶纳米GaN粉末的室温反应合成。此外，还对GaN的衬底材料LiGaO_2晶体的气相合成进行了研究。GaN粉末是在常压下，通过Ga_2O_3和NH_3反应制备的。在实验中发现，反应温度直接影响产物的颜色、结晶状态和纯度。实验中得到的制备GaN粉末的最佳条件是温度为950 ℃左右、反应时间为4小时。以GaN粉末为原料，通过建立高氨压合成新方法，在高压佩刃成功的实现GaN陶瓷体的烧结。通过在组装中添加适量的LiNH_2使之在高温高压下分解，从而形成高氨压的烧结环境。所得到的GaN的烧结体的结晶状态明显提高，在空气中的 稳定性也明显增强。随着温度的变化，所制得的GaN烧结体分别呈现为棕褐色（<900 ℃）、墟拍色（900-1100 ℃)及淡黄色（>1100 ℃）。通过对不同条件下制备的烧结体进行密度测试及破碎表面的SEM分析发现，4GPa、1000 ℃为GaN陶瓷体的最佳制备条件。通过对GaN烧结体的光谱性质进行研究发现GaN陶瓷体的荧光发射峰及红外光谱的吸收峰位置均发生了位移。实验采用机械合金化装置，在机械力化学效应的诱导下实现了GaN由纤锌矿的六方结构向闪锌矿立方结构的相转变。六方结构的GaN的XRD的图谱的明显特征是三个最高衍射强度所对应的峰的位置依次为36.7°, 32.3°和34. 5°（2θ）。经过机械球磨后的XRD的图谱在34.5°、57.8°和69.1°（2θ）位置的衍射峰为三个最强峰，而且在40.4°(2θ位置出现了一个较弱的衍射峰（该衍射峰为立方氮化嫁的特征峰）。以上结果表明，在机械球磨的作用下，六方GaN发生了向立方GaN结构的相转变。通过Raman散射光谱对比测试，六方GaN的光谱图中535, 557和567cm~(-1)的散射峰分别对应与A_1(TO), E_1(TO)和E_2声子模的振动频率，其中Ez为六方相的特有的声子模。经过球磨后的粉末的尺aman散射光谱图中551、716cm~(-1)分别对应于立方相的To和LO声子模的振动频率。光谱中六方结构的特征峰El的消失及立方相特征峰LO的出现进一步证实了在机械合金化的作用下，GaN发生了由六方相向立方相的转变。根据机械球磨可发生机械力化学反应的原理，实验中通过选择合适的嫁源和氮源，在机械合金化装置中实现了纳米非晶态GaN的室温合成。以化学计量比为1；1：1的Ga, NaN_3和NH_4Cl为原料，通过机械球磨进行合成反应。分析产物的XRD图谱发现，所有结晶相的衍射峰与NaCl的标准卡片吻合，在32-38°（2θ）区间出现一非晶相的宽峰（与GaN主峰位置对应）。证实了经过机械球磨发生了合成反应（Ga+NaN_3+NH_4Clx→GaN+NaCl+N_2+NH_3+H_2），得到了纳米非晶态GaN。通过对所得的粉末进行TEM表征，其产物颗粒为5nm左右。根据Li_2o和Ga_2o易挥发的特点，采用LiCO_3、Ga和Ca_2O_3为原料通过气相法制备了LiGaO_2晶体。

取代环戊二烯基稀土有机氯化物的合成及其反应

本文通过无水LnCl_3(Ln = Pr.Nd.Gd)与两倍摩尔的叔丁基环戊二烯基碱金属盐在THF中60－80℃反应，分离到一类新的二（叔丁基环戊二烯基）稀土氯化物（T-DuCp）_2 2net.nTHF (Ln = Pr,Nd,n = 2 Ln = Gd,n = 1)，对它们进行了元素分析。红外光谱及水鲜色质谱的表征。对于配合物（t-BuCp）_2PrCl·2THF的单晶，测定了它的晶体结构，晶体层单斜晶系P21/C空间群，晶胞参数为：a = 15.080 b = 8.855 c = 21.196A, β = 110.34°V = 2653.9A~3 δ = 4，结构分析表明此配合物是一中性的单分子配合物。最后的R = Rw = 0.058平均Pr-C.2.81 Pr-Cent 2.53A, Pr-Cl及Rr-O键长分别为2.72与2.62A。本文通过Lnel_3(Ln = Nd.Pr.Ga)与等摩尔的叔丁基环戊二烯基碱金属盐在THF中60－80℃反应，分离到一类中性的单(叔丁基环戊二烯基)稀土二氯化物，并对它们进行了元素分析，红外光谱及水鲜色质谱的表征。本文通过轻稀土元素La,Pr的三氯化物与带基钠以1:2摩尔比在THF中70－80℃反应，分离到了二带基轻稀土氯化物（CaH_7）_2LaCl.2THF及[(CqH_7)_2PrCl.THF]_2。并且对此二配合物进行了元素分析。红外光谱及水鲜色质谱的表征。对于[(CuH_7)_2PrCl.TH]_2配合物，测定了它的晶体结构，这是第一个得到结构表征的茚基稀土氯化物，晶体层于单斜晶系，P_(21)/C空间群，晶胞参数为a = 7.808 b = 17.796 c = 14.070A β = 93.97°v = 1950.31A. E = 2最后的R = 0.045. Rw = 0.039结构分析表明此配合物以中性的二聚体形式存在。平均的Pr-C.2.81 Pr-Cent 2.53. Pr-Cl.2.84H Pr-O钻长2.54A。为了进一步研究不同配体对配合物结构的影响，我们还研究了Gael_3与Nae_5Mes以1:1摩尔比在THF中的反应，分离到了两种配合物[(NaTHF)(C_5MesGd.THF)_2Cl_5]_2.6THF(I)及L_5Me_5GdCl2.3THF(II)并且对配合物（I），测定了它的晶体结构，晶体层于三斜晶系。Pi空间群。晶胞参数a = 12.183 b = 13.638 c = 17.883A, α = 110.38 β = 94.04 γ = 99.44°, V = 2721.20A, E = 1。结构分析表明，此配合物是一种以两个Na原子通过THF中的O原子而桥联的金层有机配合物，在结构上有十分新颖的特点。在此配合物分子中含有四个Gd原子及二个Na原子，Na及Gd间以Cl桥键相联结，Gd-Gd_2 = 4.033 Gdll-Na = 2.818A。最后的R = 0.04M Rw = 0.042。本文还对（t-BuCp）_2P_2Cl.2THF与NaH及LiAlH4的反应进行了初步的研究，分离到（t-Bucp）_2PrH.2THF及(t-Bucp)_2P_2RIH_4.3THF两种新的氢化物，并且对它们进行了元素分析，红外光谱的表征，对于它们水鲜产物的气相分中的H_2，用气相色谱法进行了定性表征。

Immune Responses to Six Synthetic Peptides of Capsid Protein Immune Responses to Six Synthetic Peptides of Capsid Protein

Many B cell epitopes within p24 of human immunodeficiency virus type 1 (HIV-1) were identified, while most of them were determined by using murine monoclonal antibodies reacting with overlapping peptides of p24. Therefore these epitopes may not represent the actual epitopes recognized by the HIV-1 infected individuals. In the present study, immune responses of 67 HIV-1 positive sera from Yunnan Province, China to five peptides on p24 of HIV-1 and one of HIV-2 were analyzed. All of 67 sera did not recognize peptide GA-12 on HIV-1 and peptide AG-23 on HIV-2, which indicated that GA-12 was not human B cell epitope and AG-23 did not cross-react with HIV-1 positive serum. Except 13 sera (19.4%), all remaining sera did not recognize peptides NI-15, DR-16, DC-22 and PS-18, which indicated that these four peptides represented B cell linear epitopes of HIV-1 p24 in some HIV-1 infected individuals but not the immuno-dominant epitopes in most individuals. Cellular & Molecular Immunology. 2005;2(4):289-293.

QUANTITATIVE-ANALYSIS OF INXGA1-XAS BY AUGER-ELECTRON SPECTROSCOPY

Quantitative Auger electron spectroscopy analysis for the ternary system InGa1-xAs grown by molecular-beam epitaxy has been studied. The relative sensitivity factors are determined by with an internal reference element. The matrix correction factor for In relative to Ga was shown to be 1.08. No preferential sputtering of As for the ternary compounds was found, and the sputter correction factor, K(s)InGa is 0.75. The results are compared with that measured by the x-ray double-crystal diffraction analysis, electron probe microanalysis, and Auger analysis without matrix and sputter corrections.