Logarithmic islanding in submonolayer epitaxial growth

We investigate submonolayer epitaxial growth with a fixed monomer flux and irreversible aggregation of adatom islands due to an effective island diffusion, with a diffusivity for an mass k island proportional to . For , there is a steady state, while for , continuously evolving logarithmic islanding occurs in which the island density grows extremely slowly, as . In the latter regime, the island size distribution exhibits complex, but universal, multiple-scale mass dependence which we account for theoretically. Received: 3 June 1998 / Accepted: 13 July 1998     

大尺寸KBr晶体生长及光透过性能的研究

采用提拉法生长工艺,对影响晶体透过率和吸收性能的因素进行了详细的分析,设计了合理的工艺参数,生长出了大尺寸(Φ150mm×150mm)、高透过率的溴化钾晶体(分子式:KBr)。透射谱结果表明其透过波段位于0.3-34μm,透过率高达80%左右。分析了散射颗粒形成的原因。     

Oriented growth of oxygen-free C60 crystallites on silicon substrates

This is the first report of preparation of C₆₀ fullerite films on silicon substrates coated by a layer of natural oxide. The crystallites are about 1 μm in size. The films were found to have an enhanced stability to atmospheric oxygen. The films were obtained by a modified method of discrete evaporation in a quasi-closed volume. The principal features of the method are the quasi-equilibrium condensation conditions, a high substrate temperature (up to 300 °C), and alternation of deposition with recrystallization in a single technological cycle. The method is characterized by high film condensation rates (up to 2000 ?/min) and an economical expenditure of the starting material. A study has been made of the surface structure and morphology, and of the depth profile of the film optical constants and elemental composition. Fiz. Tverd. Tela (St. Petersburg) 41, 354–359 (February 1999)     

Island growth in submonolayer deposition with aggregation and fragmentation

Island growth is studied in the case of island aggregation and break-up during submonolayer deposition. It is demonstrated that the island size distributions are of the scaling form and the mean island size has a power-law behaviour corresponding to hyperthermal deposition conditions. The corresponding scaling exponents are analytically derived and compared with the simulations by the revised particle coalescence method developed here. The scaling exponents are found to depend only on the homogeneity exponents of aggregation and fragmentation kernels.Received: 4 September 2003, Published online: 30 January 2004PACS: 68.55.-a Thin film structure and morphology - 68.35.Fx Diffusion; interface formation - 36.40.Sx Diffusion and dynamics of clustersPresent addressM. Rusanen: Institut Français du Pétrole, Groupe de Modélisation Moléculaire, BP 311, 92852 Rueil-Malmaison, France;Present address J. Asikainen: HRS F27, ETH Zentrum, 8092 Zürich, Switzerland     

Nucleation and growth on a superhydrophobic grooved surface

The growth dynamics of water drops condensed on a superhydrophobic geometrically patterned surface were studied. Drop size evolution at early and intermediate times is self-similar. Drop growth laws do not differ for a flat surface because of a reduction of both drop and substrate dimensionality. A striking observation is the instantaneous drying of the top surface of grooves at a point in time due to coalescence of the drops with a completely filled channel. At late times, only a few large drops grow connected to the channels, in a mixed Wenzel-penetration regime.     

Nucleation and growth of aluminium films on carbon layers

New experimental data are presented about the nucleation and growth of aluminium on carbon layers, both evaporated onto rocksalt at temperatures between 170 and 315°C in ultra high vacuum at pressures below 10^?10 mbar. From micrographs taken from the stripped layers, nucleation rates and saturation densities of the Al particles are determined. By comparison of the data with a theoretical model for the kinetics of nucleation and growth of thin films, information is obtained about the critical nucleus, the adsorption energy, and the activation energy for surface diffusion. The results show that the kinetics are distinctly different for at least two distinguishable sets of deposition conditions, depending on the temperature of the carbon layers.     

Nucleation and growth of calcium-phosphate on Ca-implanted titanium surface

Calcium phosphate formation on Ca-implanted titanium surfaces is studied. Experimental results show that octacalcium phosphate (OCP) is the more energetically favorable phase to precipitate on the positively charged Ca-implanted titanium surfaces compared to hydroxylapatite (HA), especially with the existence of a large amount of ions. A solution-based cluster theory is employed to explain the process of the formation of calcium phosphate on the Ca-implanted titanium surfaces. Thermodynamic and kinetic calculations show that OCP is the kinetically favored phase to precipitate in the SBF solution than HA. The nucleation rate is much higher than that of HA, but HA is more stable thermodynamically.     

Self-assembled growth of C60 nanowhiskers on anodic porous alumina membranes

Unique structured claw-like C₆₀ nanowhiskers were fabricated on an anodic porous alumina membrane. Tips of the C₆₀ nanowhiskers are shaped like cusps, which directly extend into the nanopores of the alumina membrane. It is revealed that the surface stress of the alumina membrane with a highly ordered nanopore arrangement due to thermal treatment is responsible for self-assembled growth of the observed C₆₀ nanowhiskers. The ordering of the nanopore arrangement in the anodic porous alumina membrane helps to form the C₆₀ nanowhiskers along the nanopore channels. The shape and structure of the C₆₀ nanowhiskers are promising characteristics for applications in nanodevices such as field-emission tips and nanoprobes. PACS 61.46.+w; 61.48.+c; 33.20.Fb     

C60、C60F60及C60H60“分子滚珠”的压缩特性与电子结构

采用量子分子动力学技术,模拟了C60、C60F60与C60H60分子的压缩过程,计算了这些"分子滚珠"受压变形后的电子结构.根据计算结果,对比、分析了三种分子的压缩力学特性以及压缩变形对其电子结构的影响.研究表明,1)三种分子的抗压缩载荷与能量吸收能力有C60F60＞C60H60＞C60的排序,但抗变形能力相当;2)随着压缩变形的增大,三种分子的化学活性增加,但相同应变下,C60F60和C60H60分子有着比C60更好的化学稳定性.     

Scaling of island densities in submonolayer growth of binary alloys

We study the nucleation kinetics of binary alloys formed by codeposition of A and B atoms onto a planar substrate with fluxes F(alpha) (alpha=A, B). Based on a generalization of mean-field rate equations, we derive scaling relations for the dependence of the number density of stable islands on the ratios D(alpha)/F(alpha), where D(alpha) are the diffusion coefficients of two types of adatoms. Novel scaling laws are predicted for different situations of cluster stabilities with respect to their size and composition. The predictions are validated by kinetic Monte Carlo simulations and can be tested in experiments.