铂纳米团簇在修饰的HOPG表面的生长及性能表征

用扫描隧道显微术研究了经过不同方法处理的高定向裂解石墨（HOPG）表面的性质以及铂在其上的成核和生长。通过控制氩刻及氧化时间，在HOPG表面制备出分布和大小均匀的坑。这些纳米坑具有较强的活性，在后面的金属铂沉积过程中成为铂团簇的成核中心。通过控制坑的密度和分布，可以很好地控制沉积的铂团簇的分布及大小。用X射线光电子能谱（XPS）对其电子性质进行了研究，并用高分辨电子能量损失谱（HREELS）研究了甲醇在该体系的吸附行为。     

利用低温生长法制备水纳米团簇和二维冰

利用低温扫描隧道显微镜(LT?STM)研究了水分子在高定向裂解石墨(HOPG)表面的低温吸附和薄膜生长.在低覆盖度下,水分子在HOPG表面会形成二聚体,三聚体,甚至更大的自组装纳米团簇.在高覆盖度下,水分子形成单分子层厚的二维水膜,其面内结构是非共边的六边形蜂窝状结构,类似于体材料的Ice?Ⅱ相.通过傅里叶变换和莫尔条纹分析,本文发现水膜和HOPG衬底之间存在不同的夹角,表明分子-衬底之间的相互作用很弱.     

电子显微学报第二十四卷(2005年)总目次

第一期(pp.1~84)学术论文银纳米团簇在HOPG表面上的控制生长…………………………………………王立莉,马旭村,齐云,姜鹏,焦健,包信和,贾金锋,薛其坤(1)激光对吸附在Si(111)7×7和Si(100)2×1表面上的C60的不同作用……………………………………………………赵风周,崔雪峰,王兵(6)电子束致沉积手控生长碳纳米线…………………………………………………………………………………王鸣生,王晶云,陈清,彭练矛(11)InGaN/GaN量子阱结构的应变状态与微结构、物理性能关系的研究………………………………………………………李超荣,吕威,张泽(17)…     

全同周期排列的纳米团簇阵列的自发生长

我们提出了利用分子束外延的自组织生长过程大面积制备二维周期性纳米金属团簇阵列的一种方法.该方法的普适性通过研究 Si(111)-7×7衬底上生长的Ⅲ族元素、贵金属、磁性金属以及它们的合金团簇得到证实.通过对In团族点阵的原位扫描隧道显微镜分析和第一性原理总能量计算,我们确定了这些团簇独特的原子结构,阐明了这些结构的形成机理.我们发现团簇和表面之间的强相互作用是获得团簇的特定尺寸和其有序排列的关键所在.     

二硫化钼纳米片基纳米团簇的制备及其在近红外激光的热转换性能

探讨了γ-聚谷氨酸(γ-PGA)介导合成γ-PGA/二硫化钼(MoS_2)纳米团簇的可行性,分析了γ-PGA/MoS_2纳米团簇在近红外激光的热转换性能。将γ-PGA和合成MoS_2纳米片的前驱体四硫代钼酸铵同时溶解于蒸馏水中,通过水热法自下而上一步合成出了γ-PGA修饰的MoS_2纳米团簇,MoS_2纳米团簇的直径为(197.3±26.6)nm。团簇结构的形成可能与Mo~(4+)离子和γ-PGA链中羧基上氧原子的配位作用有关。在水热反应过程中,由于这种配位作用的存在,生成的MoS_2纳米片可能进一步以γ-PGA分子链中氧原子为中心形成团簇。该纳米团簇具有优异的胶体稳定性、光热转换性能(质量消光系数为11.23L·g~(-1)·cm~(-1))和细胞相容性,有望在肿瘤的光热治疗等领域得到应用。     

激光诱导生成锗纳米晶体量子点

采用氧化和析出的方法在氧化硅中凝聚生成锗纳米晶体量子点结构.其形成的锗晶体团簇没有突出的棱角和支晶结构,锗晶体团簇的轮廓较圆混,故可以用球形量子点模型来模拟实际的锗晶体团簇.对比了在高温(800℃～1000℃)条件下和在低温(200℃～500℃)用激光照射条件下所生成的锗纳米晶体结构的PL光谱和对应的锗纳米晶体团簇的尺寸分布.低温用激光照射条件下所生成的锗纳米晶体较小,其PL光谱出现蓝移.用量子点受限模型计算了锗纳米晶体团簇的能隙结构,用Monte Carlo方法模拟了PL光谱和对应的锗纳米晶体团簇的尺寸分布,分别与实验结果吻合较好.     

飞秒强激光脉冲与氢团簇相互作用产生的最大质子能量与团簇尺寸的相关性

报道了飞秒强激光脉冲(60 fs,790 nm,2×1016W/cm2)与纳米尺寸的氢团簇(半径rc约为1~3 nm)相互作用,产生的最大质子能量Emax对于团簇半径rc相关性的实验研究结果。从激光-氢团簇相互作用产生的质子的飞行时间谱测量以及团簇尺寸的瑞利散射诊断结果,得到Emax与r2c成线性正比关系,比例系数为0.75,与报道的理论模拟结果一致,表明氢团簇发生纯库仑爆炸。实验结果同时提示,进一步的理论模拟应考虑气体喷流中团簇的尺寸分布。     

Au/SiO_2复合纳米颗粒膜的制备及退火行为研究

室温下用磁控溅射法在Si(111)衬底上生成Au/SiO2复合纳米颗粒膜。用扫描电子显微镜(SEM)和X射线衍射方法(XRD)对不同温度退火后的Au/SiO2复合薄膜的表面形貌、微观结构进行了表征。SEM结果表明,随着退火温度升高,Au纳米颗粒先形成大的聚集后出现分布均匀的超微颗粒。XRD结果显示700℃时Au的衍射峰最强,随后峰强有所减弱,这与SEM检测结果相吻合。另外实验结果证实在1000℃退火时自组装生成空间分布均匀(直径约为70nm)的Au纳米点,可以用来作为生长一维纳米材料的模板。     

两步法生长ZnO纳米棒的结构及其发光特性

应用两步法在玻璃衬底上制备了高度取向的ZnO纳米棒,并研究了衬底和反应时间等参数对其结构及发光特性的影响。从样品的扫描电镜(SEM)图中发现,利用脉冲激光沉积(PLD)方法在玻璃衬底上生长一层ZnO薄膜作为修饰层,可以明显提高水热法生长的ZnO纳米棒的结晶质量。样品的SEM和光致发光(PL)谱表明,在有ZnO修饰层的玻璃衬底上生长的ZnO纳米棒分布均匀,排列致密,取向性好;缺陷发光的发光强度约是激子发光峰的2倍,且随着反应时间增长,样品的缺陷发光增强而激子发光减弱。     

CdSe纳米团簇的透射电镜研究

在沸石分子筛中组装ＣｄＳｅ而形成半导体纳米团簇材料，并将组装ＣｄＳｅ后的沸石微粉制成完整的透射电镜薄膜，结合能谱测试，在透射电镜下观察所制得的材料的微观结构和形貌．结果表明在沸石中形成了尺寸单一、分布均匀的团簇材料     

连续运转Ar~+激光器的最佳气压分析

本文从 Tonks-Langmuir 低气压放电正柱理论出发,推导氩离子激光器输出功率和充气压力的关系,由此求得最佳气压,讨论了最佳气压的影响因素,并与实验结果相比较。     

Effect of highly dispersed sputtered silver nanoparticles on structural properties of multiwalled carbon nanotubes

A simple method to decorate mutliwalled carbon nanotubes (MWCNTs) with silver nanoparticles (Ag NPs) to enhance the structural properties is reported in the present study. The Ag NPs of average size 9 nm were deposited uniformly on MWCNTs network by RF sputtering technique. X-ray diffraction (XRD), Raman spectroscopy and Scanning electron microscopy (SEM) are used to compare the structural properties of Ag NPs sputtered nanotubes with those containing functionalized tubes. In addition, effect of these Ag NPs on the surface of nanotubes and optimization of the experimental parameter for uniform deposition of Ag NPs are also discussed.     

Synthesis of uniform amplitude unequally spaced antenna arrays using the differential evolution algorithm

A computationally efficient global optimization method, the differential evolution algorithm (DEA), is proposed for the synthesis of uniform amplitude arrays of two classes, i.e., unequally spaced arrays with equal phases and unequal phases. Phase-only synthesis and the synthesis of uniformly exited unequally spaced arrays (position only synthesis) are compared and it is seen that, by using the unequal spacing, the number of array elements can be significantly reduced for attaining reduced sidelobe levels. From the DEA-based synthesis of unequally spaced arrays with uniform amplitudes and unequal phases, it is found that a tradeoff exists between the size of the unequally spaced arrays and the range of phases for the same radiation characteristics. The proposed synthesis technique using uniform amplitudes, unequal spacing, and unequal phases (position-phase synthesis) not only decreases the size of the array for the same sidelobe level compared to both the phase-only synthesis and position-only synthesis but also retains their advantages.     

Determine optimum number of compact overlapped clusters using FRLVQ technique

A method, named XHJ-method, is proposed in this letter to determine the number of clusters of a data set, which incorporates with the Fuzzy Reinforced Learning Vector Quantization （FRLVQ） technique. The simulation results show that this new method works well for the traditional iris data and an artificial data set, which contains un-equally sized and spaced clusters.     

Ar~+激光治疗鲜红斑痣

利用Ar~+激光对77例鲜红斑痣进行治疗,收到了较为满意的效果,表明Ar~+激光是目前治疗鲜红斑痣比较好的一种方法。     

Model-based synthesis of shaped-beam patterns with the minimum number of elements: a state-space method

Conventional antenna array synthesis methods can give good performance for uniform spaced antenna arrays within desired performance bounds. However, due to the restriction of uniform antenna element spacing, a lot of elements are required. Because of the above-mentioned drawback, in this paper, a new approach is presented to synthesise uniform spaced antenna array using the minimum number of elements. This approach introduces the state-space model to represent the desired discrete array pattern that is sampled uniformly from ?1 to 1 corresponding to 0–180°, then uses the desired sampled array pattern directly to construct the forward–backward data matrix that is introduced to estimate the model parameters, from which the locations and excitations of the new antenna elements can be extracted. The appropriate roots that are located on the unit circle are selected to obtain new radiation pattern. Simulation results show the viability for both shaped-beam and pencil-beam designs.     

Influence of ENIG defects on shear strength of pressureless Ag nanoparticle sintered joint under isothermal aging

An Ag nanoparticle sintering is a promising die attach method for use in high-temperature electronics and could potentially be substituted for conventional high Pb-containing solders. An electroless Ni/immersion Au (ENIG) is a common surface finish for solder, wire bonding, and Ag nanoparticle sintering. However, there is no report on the influence of ENIG defects on the shear strength and bonding quality of Ag nanoparticle sintered joint. In this study, the relationship between the presence of ENIG defects and shear strength of Ag nanoparticle sintered joint after bonding and isothermal aging test using two types of ENIG surface finished Cu substrates (with ENIG defects and without defects) was investigated. The initial shear strength of Ag sintered joint showed similar values of approximately 36 MPa despite the presence of ENIG defects. However, the ENIG defects could affect the shear strength degradation of Ag sintered joint after thermal aging at 250 °C. This degradation came from the Ni oxidation by the presence of ENIG defects and subsequent brittle fracture of joint alone the Ni oxidation layer.     

Interfacial microstructure and shear strength of Ag nano particle doped Sn-9Zn solder in ball grid array packages

Sn-9Zn solder joints containing Ag nano particles were prepared by mechanically mixing Ag nano particles (0.3, 0.5 and 1 wt%) with Sn-9Zn solder paste. In the monolithic Sn-Zn solder joints, scallop-shaped AuZn₃ intermetallic compound layers were found at their interfaces. However, after the addition of Ag nano particles, an additional uniform AgZn₃ intermetallic compound layer well adhered to the top surface of the AuZn₃ intermetallic compound layer was found. In addition, in the solder ball region, fine spherical-shaped AgZn₃ intermetallic compound particles were observed as well as Zn-rich and β-Sn phases. With the addition of Ag nano particles, the shear strengths consistently increased with an increase in the Ag nano particle content due to the uniform distribution of fine AgZn₃ intermetallic compound particles. The shear strength of monolithic Sn-Zn and 1 wt% Ag nano particle content Sn-Zn solder joints after one reflow cycle were about 42.1 MPa and 48.9 MPa, respectively, while their shear strengths after eight reflow cycles were about 39.0 MPa and 48.4 MPa, respectively. The AgZn₃ IMCs were found to be uniformly distributed in the β-Sn phase for Ag particle doped Sn-9Zn composite solder joints, which result in an increase in the tensile strength, due to a second phase dispersion strengthening mechanism. The fracture surface of monolithic Sn-Zn solder exhibited a brittle fracture mode with a smooth surface while Sn-Zn solder joints containing Ag nano particles showed a typical ductile failure with very rough dimpled surfaces.     

溅射原子的初始位置分布和表面出口位置分布

用物理溅射的Monte Carlo模拟程序TCISIS,研究了在O~+离子与Ar~+离子轰击下Al靶与Si靶的溅射原子的初始位置分布和表面出口位置分布.讨论了离子束溅射横向可达分辨率的物理限制.所计算的溅射原子的初始位置分布和表面出口位置分布的宽度,对于离子束溅射刻蚀的微细加工和SLMS设计是有参考价值的.计算的溅射原子的逃逸深度分布表明,溅射原子的大多数来自于表面前2个原子层.