Effect of Polymer-Substrate Interactions on the Surface Morphology of Polymer Blend Thin Films

Surface structures and compositions of poly(Styrene-block-Ethylene/Butylene-block-Styrene) (SEBS)/Poly(Methyl Methacrylate) (PMMA) blend films have been studied by Atomic Force Microscopy (AFM) and X-ray Photoelectron Spectroscopy (XPS). Substrates with different hydrophobicity and SEBS with and without Maleic Anhydride (MA) grafting were used to study the effect of polymer-substrate interactions. It is indicated that the surface energy of the substrate (substrate/air) plays a crucial role on the surface composition of the polymer component. For a fixed surface, the adsorption of polymer on the substrate is also important. The hydrophilic sites of SEBS-g-MA can prevent the dewetting of the SEBS-g-MA from the substrate. The dewetting of PMMA from the SEBS-g-MA will make the PMMA protrusions more pronounced, and the SEBS-g-MA phase domains are enlarged after annealing treatment. An adsorption scheme is suggested to explain the phase inversion and height difference observed in the various polymers used. In addition, SEBS triblock copolymers form wormlike and meshlike microphase separation morphologies on the hydrophilic and hydrophobic substrates, respectively.     

溅射过程中粒子能量对钛薄膜表面形貌影响

借助于原子力显微镜研究了离子束溅射沉积工艺中入射离子能量对制备的Ti薄膜表面形貌的影响。对薄膜表面高度数据进行相关运算，发现在此工艺条件下制备的薄膜具有典型的分形特征，利用分形表面高度—高度相关函数的唯象表达形式对不同能量下制备Ti薄膜表面的高度相关函数进行拟合。得到了薄膜表面的分形维数、水平相关长度、标准偏差粗糙度等参量。研究发现，入射Ar离子能量在300—700eV之间薄膜表面的粗糙度随着沉积粒子的能量增加而增大，分形维数随着入射离子能量的增加而减少。另外，在得到的分形维数基础上对不同溅射电压下Ti薄膜的生长机制进行了初步研究。     

磁性薄膜自旋重取向行为的Monte Carlo模拟

利用Monte Carlo方法模拟了二维简单立方结构磁性薄膜的自旋重取向行为,重点研究了各向异性和偶极相互作用对系统自旋取向的影响．通过计算,获得了系统的相图以及系统组态、磁分量、比热等随偶极相互作用和温度的变化规律．模拟结果表明,在一定的参数范围内,随着温度的升高,系统的自旋取向将由垂直向平行方向转变。     

Wetting and Phase Separation in Polymer Blend Films: Identification of Four Thickness Regimes with Distinct Morphological Pathways

Using forward recoil spectrometry and atomic force microscopy, the phase evolution of a critical blend thin film of deuterated poly(methyl methacrylate) (dPMMA) and poly(styrene-ran-acrylonitrile) (SAN) is found to depend on film thickness. Four regimes are identified as film thickness l ₀ decreases from semi-infinite to below the radius of gyration, R _g. In the semi-infinite limit or regime IV (l ₀ R _g), surface directed spinodal decomposition is observed and found to agree with cell dynamic simulations. In regime III (10 R _g < l ₀ < 150 R _g), three stages of evolution are observed. During the early stage, wetting dominates and produces a dPMMA-rich/SAN-rich/dPMMA-rich structure. During the intermediate stage, the surface phase flows back into the middle layer inducing lateral phase coarsening. During the late stage, capillary fluctuations rupture the middle layer by spinodal dewetting, resulting in a final morphology with SAN-rich droplets encapsulated by dPMMA-rich wetting layers. Although regime II (R _g < l ₀ < 10 R _g) films also exhibit a tri-layer early stage, correlated holes in the middle layer spontaneously grow suggesting that this layer is too thin to support fully developed capillary fluctuations. Three stages of roughening are observed with a final morphology similar to regime III. In regime I (l ₀ < R _g), films roughen almost immediately after annealing in contrast to the other regimes. Initially, the surface roughness increases logarithmically with time before reaching a constant value of 2 R _g. The final average droplet height, 29.5 nm, is in good agreement with a simple interfacial energy model. Whereas the final morphology for regimes I, II and III are identical, the pathways by which films roughen are distinct suggesting that erroneous conclusions can be made by simply analyzing the final morphology.     

表面预处理对氧化锌薄膜质量的影响

用MOCVD方法在c面蓝宝石衬底上生长ZnO薄膜。生长前衬底表面进行预处理,观察不同表面预处理对ZnO薄膜质量的影响。测量氧化锌的XRD谱,观察表面预处理后对氧化锌薄膜结晶质量的影响。室温下用325nm的He-cd激光器作为激发源测量ZnO薄膜的紫外发光谱,观察表面处理后对ZnO薄膜发光特性的影响。用HL5500 Hall System分别对ZnO薄膜的电学特性进行了测试。得到了ZnO薄膜的电阻率和霍尔迁移率,并得到氧气气氛处理后电阻率变小,霍尔迁移率变大;氮气气氛射频处理后电阻率变大,霍尔迁移率变小的结果。     

Polymer mixtures in confined geometries: Model systems to explore phase transitions

While binary (A,B) symmetric polymer mixtures ind = 3 dimensions have an unmixing critical point that belongs to the 3d Ising universality class and crosses over to mean field behavior for very long chains, the critical behavior of mixtures confined into thin film geometry falls in the 2d Ising class irrespective of chain length. The critical temperature always scales linearly with chain length, except for strictly two-dimensional chains confined to a plane, for whichT _c ∝N ^5/8 (this unusual exponent describes the fractal contact line between segregated chains in dense melts in two spatial dimensions,d = 2). When the walls of the thin film are not neutral, but preferentially attract one species, complex phase diagrams occur due to the interplay between capillary condensation and wetting phenomena. For ‘competing walls’ (one wall prefers A, the other prefers B) particularly interesting interface localization-delocalization transitions occur, while analogous phenomena in wedges are related to the ‘filling transition’.     

无序杂质区域对沉积在胶体基底表面的金原子凝聚体分形结构的影响

由于受基底表面无规分布杂质的影响,沉积在熔融玻璃基底表面的金原子凝聚形成了具有特殊结构的分形凝聚体.根据这一实验结果,建立了各向异性的团簇团簇凝聚模型,对此类胶体基底表面的金原子分枝状凝聚体的生长过程进行了计算机模拟,研究了无规分布的杂质区域对凝聚体各种参数的影响,其结果与实验相符合 关键词： 薄膜生长 MonteCarlo模拟 分形     

二元合金表面偏析的Monte Carlo方法模拟

详细介绍了二元合金表面偏析的Monte Carlo模拟方法,并应用改进的分析型嵌入原子模型结合Monte Carlo方法模拟研究了Pd-Au合金表面成分及其剖面成分分布,发现Au在表面偏析,并同已有实验结果进行了比较.     

Ag-BaO薄膜在垂直表面电场作用下的光吸收增强

Ag-BaO薄膜是金属纳米微粒埋藏于半导体介质中的功能复合薄膜,它具有超快的光电时间响应,可以检测超短激光脉冲,在Ag-BaO薄膜表面加入垂直电场,可以提高薄膜的光电发射效率,在垂直表面电场作用下近紫外波段光吸收有较明显增强现象,在波长λ=303nm处15V电压作用下光吸收增强6.5%,30V电压作用下增强18%。这种光吸收增强是由于在电场作用下,薄膜的能带结构发生倾斜,以及在强电场下能级分裂。光吸收涉及被激发电子在倾斜能带间隧穿几率的增加,和被激发电子在这些分裂能级间的跃迁。     

两种测试高温超导薄膜微波表面电阻方法的讨论

介绍两种工作在12GHz附近的高温超导薄膜微波表面电阻Rs测试系统,并分析各自的特点.同时简介电子科技大学在提高Rs测试精度上所作的一些改进.     

非均一相互作用能对超薄膜生长影响的Monte Carlo模拟研究

利用Monte Carlo (MC)模拟技术研究了非均一的吸附原子与基底相互作用能在一定的生长条件下对超薄膜生长过程的影响.非均一相互作用能是由基底表面原子在垂直和水平方向上实际位置与理想晶格原子位置的偏差所造成.本文用高斯分布来表示这种非均一相互作用能.模拟结果表明:非均一相互作用能对超薄膜的生长过程及薄膜的形貌有显著的影响.这种影响同时受到生长条件的限制,在中等温度时相互作用能的非均一性对岛的个数、平均大小的影响最显著;温度的增加在一定程度上可抵御相互作用能的非均一性对薄膜生长的影响. 关键词： 薄膜生长 Monte Carlo 模拟 相互作用能     

Thermally Induced Changes of Interphase Boundary Morphology in Coherent A/B Multilayers: A Monte Carlo Simulation

The evolution of the interphase boundary morphology during annealing of nanoscale metallic A/B multilayers is studied by means of Monte Carlo simulations based on a vacancy migration algorithm. The two components A and B are supposed to be largely immiscible. As initial condition for the simulations, it is assumed that a thermally induced destruction of polycrystalline multilayers starts at grain boundaries by breakthrough of one component through layers of the other one. Simulations of the subsequent development of the phase morphology within the multilayer grains reveal a recession of broken layers which leads to a localised fusion with adjacent layers of the same component. The evolving morphology depends sensitively on the rate of initial layer breakthrough at grain boundaries compared to the velocity of layer recession. Formation and subsequent growth of pinhole-like layer breakthroughs within multilayer grains are proposed as additional mechanisms of multilayer destruction, which should become important at higher temperatures for large lateral grain size and thin individual layers of a few monolayers thickness.     

无格点基底表面的杂质分布对分枝状凝聚体的影响

根据含杂质熔融玻璃表面金原子凝聚的实验规律，在原子团簇具有随机的线扩散步长和刚性转动角的特征条件下，建立了含杂质无格点基底表面上改进的杂质限制团簇-团簇(IRCCA)凝聚模型.对团簇的扩散、刚性转动以及凝聚全过程进行了计算机模拟，系统地研究了杂质区域分布情况对分枝状凝聚体诸多特性的影响.结果表明规则分布的杂质对凝聚体生长的影响比随机分布的杂质大，导致杂质规则分布的基底表面上的分枝状凝聚体的数密度更大，分枝状凝聚体的回旋半径，凝聚体平均大小及分形维数更小. 关键词： 薄膜生长 Monte Carlo模拟 分形 杂质     

Effect of Solvent Annealing on the Nano- and Micro-Structure of Block Copolymer Thin Film

The development of structure of symmetric polystyrene-b-poly(2 vinyl pyridine) (PS-PVP) thin film annealed under a neutral solvent vapor was investigated by atomic force microscopy and optical microscopy. Initially, spin cast film showed a micellar structure. With subsequent neutral solvent vapor treatment, a lamellar structure gradually developed. It was found that the structural evolution of the thin film was a strong function of the quantity of solvent diffused into the film. In addition, with an increase in swelling, the orientation of the lamellae changed from parallel to perpendicular. During solvent annealing, the solvent also induced dewetting via primary and secondary heterogeneous nucleation processes, depending on the quantity of solvent in the film. Secondary nucleation was independent of primary nucleation for lower solvent concentration. With higher amount of solvent, the solvent expedited secondary nucleation, and it occurred within the dewetted area caused by primary nucleation.     

非均匀基底上三维薄膜生长的模拟研究

考虑原子在基底表面的扩散、沿岛周界的扩散和不同层间的扩散以及非均匀基底上表面吸附能分布的各向异性，建立起非均匀基底表面上原子扩散和三维薄膜生长的动力学蒙特卡罗模型.模拟得到在不同生长条件下出现的层状生长、岛状生长和混合生长三种生长模式和相应的多层薄膜生长形貌图.通过统计三维薄膜中原子在各层的分布，计算薄膜的表面粗糙度，得到薄膜生长模式与生长条件之间的关系. 关键词： 薄膜生长 非均匀基底 动力学蒙特卡罗模拟     

Surface Segregation in Miscible Blends of Polystyrene and Poly(vinylmethyl ether): Comparison of Theory and Experiment

The effect of the interplay between bulk and surface free energy terms on surface segregation in miscible blends is probed by comparing angle-dependent x-ray photoelectron spectroscopy (ADXPS) measurements for polystyrene/polyvinylmethylether (PS/PVME) blends of with those for perdeuteropolystyrene/polyvinylmethylether (dPS/PVME) blends. The magnitudes of the bulk interaction parameters for the two systems differ markedly while the surface interactions are essentially identical. Experimental concentration depth profiles are almost identical for the two systems indicating that their surface properties are little affected by bulk interactions and dominated by surface energy effects.These data and previous data from our group are compared to the predictions of the square gradient theory developed by Schmidt and Binder in order to gain a more quantitative understanding of the factors that control surface segregation in miscible blends. While there is general qualitative agreement between theory and experiment, predicted surface compositions fall significantly below experimental values and predicted composition depth profiles decay more gradually than what is observed experimentally, especially for low PVME contents. The use of the more appropriate Sanchez-Lacombe-Balazs equation of state does not yield any significant improvement over the use of the Flory-Huggins lattice model for representing the bulk free energy terms. Careful analysis of the experimental behavior suggests that configurational effects associated with the flattening of surface adsorbed chains and differences in mer-mer interaction parameters in the bulk and near surface regions are possible origins for the discrepancies between theory and experiment.     

Monte Carlo Investigation of Adsorption Stage of O on Ru（0001）：a Study of a Lattice Model

The adsorption of O on Ru(0001) is studied by means of Monte Carlo simulation of lattice gas model on a triangular lattice. A recent STM study shows that at low coverage the p(2×2) structure grows via island formation but the p(2×1) structure is abruptly formed at a critical coverage. Moreover, it also shows that there is a coexistence of the p(2×2) and p(2×1) structures. The above results seem not to coincide with the former studies of the system by both the LEED and Monte Carlo simulation. We therefore carried out the Monte Carlo study for the system again in the present paper and found that our simulation almost agrees with the results of the STM.     

模体大小对MC程序计算速度与精度的影响研究

蒙特卡罗程序的计算速度与计算模型的体积大小有一定关联。 通过改变模体的厚度， 发现除在尾部有限范围内会出现差异外， 薄模体与厚模体的结果差别很小， 然而却可以获得模拟效率的指数性提升。 通过改变模体的宽度， 发现窄模体与宽模体相比， 只要宽度比照射野半影大， 对模拟效率的影响都很小； 而当宽度与照射野半影区重合时， 效率就有一定程度的提高， 同时对剂量结果影响很小。 将此研究结果用于临床头部实例， 获得了计算速度的显著提升。     

Model of phase separation and of morphology evolution in two-phase alloy

Elementary theory of mass-transfer in two-phase alloy under electromigration with account of two competing mechanisms of the fluxes equilibration is presented. These two competing mechanisms are Kirkendall effect and backstress. Various versions of Monte Carlo models for simultaneous simulation of structure evolution kinetics and of mass-transfer kinetics under high-density current are presented. Possibility of self-organization with minimization of Joule heating is demonstrated.