Cu薄膜生长过程的Monte Carlo模拟

用动力学晶格蒙特卡洛模型(Kinetic Lattice Monte Carlo,KLMC)模拟Cu薄膜的生长过程,讨论了基底温度、沉积原子数、单原子最大迁移步数和原子相互作用范围等参数对薄膜表面形貌的影响,并与实验结果进行了比较.结果表明:基底温度升高或沉积原子数增加时,沉积在基底上的原子逐步由众多各自独立的离散型分布向聚集状态过渡形成团簇,并且温度越低,团簇越趋于分散生长.当最大迁移步数减小或相互作用范围增大时,团簇亦趋于分散生长.     

铜、银及铂原子纳米团簇熔点随尺寸非单调变化的分子动力学模拟研究

采用分子动力学方法和原子嵌入法模型势模拟了铜原子、银原子及铂原子纳米团簇的熔化过程,研究了这些金属原子纳米团簇熔点与团簇尺寸的关系,发现各自在小于一定数目原子的金属纳米团簇的熔点不再随尺寸的变小而单调下降,通过对各种团簇溶化前后结构的比较研究,分析了导致这种现象的原因。     

中介尺度Au纳米团簇凝固过程的分子动力学模拟

采用分子动力学模拟技术,研究了原子个数N=1088的Au纳米团簇的凝固过程的微观结构、热力学和动力学参数的变化.模型采用的是Johnson的EAM作用势.模拟结果表明:液态团簇在两种不同的冷速下冷却得到两种不同的固态组织:晶体团簇和非晶团簇.当冷速为1.5625×1013K/s时,能量随温度的变化呈线性关系,且偶分布函数的第二峰发生劈裂,体系形成非晶态;当冷速为1.5625×1012K/s时,能量-温度曲线上出现拐点,且偶分布函数显示明显的晶体峰特征,说明体系形成了晶体.另外,计算了不同冷速下原子的平均平方位移随温度的变化,发现原子位置的重排对冷却速度非常敏感.当冷速较快时,原子只在很小的范围内运动;而结晶过程是原子不断扩散重新排列的过程.     

基底温度对c-Si(100)面生长a-Si∶H薄膜结构特性影响的分子动力学模拟研究

运用分子动力学方法模拟了不同基底温度下在硅(100)表面沉积生长氢化非晶硅薄膜的过程.Si-H体系的原子间相互作用采用Murty-Tersoff势计算.结果得到:随着基底温度的升高,a-Si∶H薄膜表面粗糙度降低,内部致密度提高,H原子、Si-H键和悬挂键密度均减少.进一步分析发现,粗糙度和致密度随基底温度变化的原因是基底温度升高增大了表面原子的扩散能力;而H原子和Si-H键等含量随基底温度升高而下降是因为高温下Si-H弱键更易断键导致.悬挂键密度随基底温度升高而降低则主要是由于内部原子的晶化率增大引起.     

四氧化三铁纳米团簇的表面修饰及生物毒性研究

采用微波辅助溶剂热法制备了四氧化三铁(Fe3O4)纳米团簇.为了改善团簇的稳定性,用改进的St(o)ber法,在Fe3O4团簇的表面包覆—层氧化硅(SiO2),成功制备出核-壳结构的Fe3O4@SiO2粒子.用透射电镜(TEM)、X射线衍射仪(XRD)、纳米粒度仪、Zeta电位、振动样品磁强计(VSM)、MTT比色法等测试手段,对样品的形貌、结构、粒径分布、胶体稳定性、磁学性质及生物毒性进行了研究,结果表明:所制备的Fe3O4纳米团簇平均尺寸约为60nm,尺寸均匀,在室温下表现出超顺磁性.包覆后的核-壳结构Fe3O4@SiO2粒子平均尺寸约为150 rn,具有良好的水分散性和胶体稳定性,包覆前后的样品均具有低的生物毒性.     

玻璃基片表面纳米结构氧化锆聚集体组装的SEM研究及其机理初探

以纳米粒子为基组装的有序结构体系,既具有纳米小颗粒本身的性质,同时通过纳米粒子之间、纳米粒子与基体界面的耦合,有望产生新的效应.本文利用含有双亲分子的反胶团微乳体系,人为处理基底提供活性点模拟生物矿化过程,构筑聚集体-基质复合材料,完成玻璃基片表面不同形貌氧化锆的组装,并对机理进行了初步的探讨.     

热退火诱导C+注入Si晶体的蓝光发射

在室温和注入能量为60 keV的条件下,在硅晶片中注入C+,使其剂量达到5.0×1016 cm2,随后即对样品进行高温退火处理.采用X射线衍射(XRD),拉曼和光致发光(PL)光谱技术对样品进行了表征.实验结果显示:C+注入后经高温退火的样品的XRD图谱中,在40°附近处出现了衍射峰,表明经退火后样品中形成了纳米尺寸的SiC团簇,并观察到了强烈的蓝光发射.PL光谱中的蓝光峰起源于量子限制效应.     

电气石表面TiO2微孔空心球簇的制备及光催化活性研究

用溶胶-凝胶技术在紫铜表面制备含电气石矿物粉末的TiO2复合薄膜,研究薄膜的制备方法、显微结构及其光催化活性.用SEM技术研究电气石-TiO2复合薄膜的微观结构和电气石表面TiO2的显微结构,测量了TiO2空心球直径、TiO2空心球簇大小,同时用电子探针对电气石-TiO2复合薄膜中的TiO2空心球簇表面及球簇周围TiO2膜进行了成分分析;并用电气石/TiO2复合薄膜光催化降解甲基橙水溶液,研究电气石对TiO2薄膜光催化活性的影响.结果发现,紫铜表面上电气石微粒均匀分布在TiO2薄膜中,且在电气石微粒表面可形成TiO2微孔空心球和微孔空心半球构成的微孔空心球簇,空心球和空心半球的平均粒径为2μm;经紫外线照射180min后,与不含电气石的TiO2薄膜相比,含电气石0.5;的TiO2复合薄膜对甲基橙的光催化降解率可提高31.9;,电气石可以明显提高TiO2薄膜的光催化活性.     

磁场直拉硅原理的微观解释

本文从电磁相互作用基本原理出发,研究锗熔体在垂直磁场中粘度的变化、液态汞在水平磁场中粘度的变化和粘度随磁场强度变化的机理,将研究结果拓展到磁场直拉硅的生产中,根据直拉硅和磁场直拉硅生产过程中,硅熔体中硅原子或原子团的带电状态和运动状态,提出了磁场直拉硅原理的微观解释,外加磁场改变了带电硅粒子(带电的硅原子或原子团)的热对流状态,抑制了熔体中的热起伏,稳定了结晶前沿处熔体的流动状态,为晶体生长提供了稳定的条件.     

MOVPE生长m面GaN薄膜的表面吸附研究

采用基于密度泛函理论的Materials Studio中的CASTEP模块,对金属有机物气相外延MOVPE生长m面GaN薄膜的表面反应前体的吸附过程进行研究.针对吸附粒子GaCH3和NH3在m面GaN表面不同的初始吸附位,优化计算了GaCH3和NH3在表面的吸附能、与近邻原子的距离、态密度、电荷密度分布、电子布居.计算结果表明,GaCH3在表面Ga brg2位优化之后的位置最稳定,吸附能最低,GaCH3中的Ga原子与表面邻近的N原子、Ga原子分别形成Ga-N、Ga-Ga共价键.NH3在表面N brg2位最稳定,吸附能最低,NH3中的N原子与表面邻近的Ga原子形成N-Ga共价键.通过对比在最佳吸附位的MMG中的Ga原子和NH3中的N原子与表面原子的电荷分布情况和布居数,证明上述吸附粒子与表面确实存在共价作用,形成共价键.     

He离子注入对Ge中缺陷行为的影响研究

本文采用以蒙特卡罗方法为基础的SRIM软件模拟He离子注入对Ge中缺陷行为的影响,为高质量GOI(绝缘体上Ge)材料的制备提供理论指导。本文主要模拟了He离子入射角度、能量以及注入剂量对Ge材料损伤程度和溅射产额等的影响。研究表明:入射角度较小时,拖尾效应不明显,有利于避免沟道效应,同时缺陷空位数(DPA)也处于较低水平;能量增大导致离子射程增大,溅射产额减小,离表面越近的Ge中DPA变少,可以实现低DPA GOI材料的制备;离子注入剂量增大导致损伤区域增大且集中,然而更多的He离子聚集在射程附近,能够很好地降低GOI材料的剥离温度。     

镁/钛离子注入对蓝宝石微结构和机械性能的影响

离子注入已被证明是改善蓝宝石光学和机械表面性能的一种可靠方法.本文选择不同能量和剂量的镁/钛离子注入蓝宝石.利用TRIM(Transport of Ion Matter)程序分析了镁/钛离子在蓝宝石晶体中的射程分布.利用拉曼光谱和掠入射X射线衍射分析了损伤层深度和微结构变化.离子注入结果显示,蓝宝石的纳米硬度、纳米划痕和红外性能等均呈现出可调节的特性.     

离子注入技术在山东蓝宝石优化处理中的应用

本文报道了用离子(Be~(2+)和Ti~(4+))注入技术优化处理山东蓝宝石的工作.对处理前后样品一系列测试和实验的结果表明:(1)样品经过离子注入处理后,表面光泽明显增强,表面光洁度保持良好;(2)山东蓝宝石注入Be~(2+)后,颜色较处理前更深,说明Be~(2+)虽然不是致色离子,但可对蓝宝石颜色产生明显的影响;(3)注入Ti~(4+)后,山东蓝宝石的颜色变浅变艳了.进一步证明了山东蓝宝石的颜色深是由于Fe~(2+)浓度高,同时Ti~(4+)浓度相对太低所致,对今后山东蓝宝石乃至其它宝石的优化处理提供了新的思路和方法.     

Aerosol particles from bubblers in metalorganic vapor phase epitaxy

We report on aerosol particles generated by bubblers in metalorganic vapour phase epitaxy (MOVPE). A triethylgallium bubbler was investigated in a MOVPE set-up regarding the generation of aerosol. Our measurements show that aerosol particles are produced, and the production depends on the carrier gas flow bubbling through. The distribution of the particle diameters was measured and was found to range from 10 to 600 nm, with the maximum at about 200 nm. While the number of particles is not negligible the precursor is almost only transported as gas molecules. However, particles could possibly reach the substrate and create defects on the surface.     

Annealing effect on electrical and photoconductive properties of Si implanted GaSe single crystal

GaSe single crystals grown by Bridgman method have been doped by ion implantation technique. The samples were bombarded in the direction parallel to c‐axis by Si ion beam of about 100 keV to doses of 1 × 10¹⁶ ions/cm² at room temperature. The effects of Si implantation with annealing at 500 and 600 °C on the electrical properties have been studied by measuring the temperature dependent conductivity and photoconductivity under different illumination intensities in the temperature range of 100–320 K. It is observed that Si implantation increases the room temperature conductivity 10⁻⁷ to 10⁻³ (Ω‐cm)⁻¹ depending on the post annealing temperature. The analysis of temperature dependent conductivity shows that at high temperature region above 200 K, the transport mechanism is dominated by thermal excitation in the doped and undoped GaSe samples. At lower temperatures, the conduction of carriers is dominated by variable range hopping mechanism in the implanted samples. Annealing of the samples at and above 600 °C weakens the temperature dependence of the conductivity and photoconductivity. This indicates that annealing of the implanted samples activates Si‐atoms and increases structural deformations and stacking faults. The same behavior was observed from photoconductivity measurements. Hence, photocurrent‐illumination intensity dependence in the implanted samples obeys the power low I_pc ∝ Φⁿ with n between 1 and 2 which is an indication of continuous distribution of localized states in the band gap. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

GaAs衬底温度对液滴外延法生长In液滴的影响

采用液滴外延法在GaAs(001)衬底上生长In液滴,利用原子力显微镜(AFM)对不同衬底温度下生长的样品进行表征,观察其表面形貌。研究表明In液滴的生长对衬底温度十分敏感,随着衬底温度的升高,液滴密度逐渐减小,液滴尺寸逐渐增大。分析了In液滴在不同衬底温度形成过程的物理机制,解释了该实验现象的原因。根据成核理论中最大团簇密度与衬底温度之间的关系,拟合计算出In液滴密度与衬底温度满足的函数关系为n_x=5.17 exp(0.69 eV/kT)。     

Influence of carbon contamination on etched GaSb substrate on the quality of MBE-GaSb film and electrical transport through the film and the substrate

Undoped MBE-GaSb films were grown on undoped GaSb (100) substrates and the influence of carbon contamination on the etched GaSb substrate on the grown film were investigated. It was found that carbon contamination of the etched GaSb substrate was dependent on the chemical treatment method and produced stacking faults in the subsequent MBE growth of the GaSb film. Carbon contamination on the etched GaSb substrate degraded the quality of the GaSb film and affected ohmic characteristics between the film and the substrate. Substrate surface free of carbon contamination and thereby exhibitting no influence on the electrical transport through the film and the substrate could be reproducibly obtained by performing an oxide etch-off chemical treatment on the GaSb substrate.     

Ion-beam deposition of tourmaline film on glass

Ion-beam deposition of tourmaline on glass substrate was investigated. X-ray fluorescence has been used to characterize surface composition of glass before and after deposition. The surface morphologies of glass were investigated by atomic force microscope. The crystallographic properties of the prepared films were evaluated by X-ray diffraction. Fourier infrared spectroscopy was used to determine infrared transmission. It is concluded that symmetrical island structure tourmaline film can be deposited on the glass substrate. The average size of the tourmaline grain is about 1 μm.     

Influence of ion implantation on structural and photoconductive properties of Bridgman grown GaSe single crystals

The structure and temperature dependent spectral photoconductivity of as‐grown and N‐and Si‐implanted GaSe single crystals have been studied. It was observed that post‐annealing results in a complete recovery of the crystalline nature that was moderately reduced upon implantation. The band edge is shifted in the implanted sample which is attributed to the structural modifications and continuous shallow levels introduced upon implantation and annealing. Our calculations showed that the trap density is increased upon implantation and annealing which confirms a possibility of explanation the phenomenon within a framework of continuous trap levels. Photocurrent measurements as a function of photo‐excitation intensity also support continuous distribution of localized states in the band gap. © 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim     

Effect of substrate temperature on the properties of reactively sputtered TiN/NbN multilayers

TiN/NbN multilayer coatings were deposited with various substrate temperatures by DC reactive magnetron sputtering method onto Si (111) and glass substrates. The effect of substrate temperature on the structural and optical properties of TiN/NbN multilayers was investigated by X‐ray diffraction, X‐ray photoelectron spectroscopy, Field emission scanning electron microscopy and Photoluminescence measurements. The composition was analyzed by X‐ray photoelectron spectroscopy. X‐ray diffraction results showed that the layers crystallized in cubic structure for TiN and hexagonal structure for NbN. It was found that grain size increased with increase in substrate temperature. The surface morphology of the TiN/NbN thin films showed a dense and smooth surface with substrate temperature upto 200 °C but after 300 °C, the grains became larger and coarse surface was observed. The TiN/NbN multilayer coatings exhibited the characteristic peaks centered at 180, 210 and 560 cm^‐1. Red band emission peaks were observed in the wavelength range of 700‐710 nm. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)