Cluster-assembled materials open fascinating new routes for tuning physical and chemical properties by changing cluster size and often these materials behave completely differently than their bulk analogues. By depositing gas phase cluster cations on various surfaces, cluster model catalysts are fabricated, which exhibit remarkable catalytic activity. While inert as bulk material, gold cluster catalysts oxidize carbon monoxide with Au8 to be the smallest active size. In contrast to the high selectivity of Pd(111) surfaces for the cyclotrimerization of acetylene, small supported Pdn clusters reveal a strongly size-dependent selectivity for the polymerization of acetylene and catalyze the cyclotrimerization as well as the hydrogenation of the formed intermediate C4H4.

The model for describing kinetic properties of adatoms on an anisotropic substrate is proposed. The kinetic equation for 1D adatom localized structures is constructed in the frame of the Sine-Gordon model. The self-diffusion coefficient for adatoms is calculated and the process of their homogenization is discussed.

We propose a new kinetic model for surface segregation during vapor phase growth that takes into account multiple mechanisms for segregation, including mechanisms for inter-layer exchange and surface diffusion. The resulting behavior of the segregation length shows temperature and velocity dependence, both of which have been observed in experiments. We compare our analytic model to experimental measurements for segregation of Phosphorus in Si(001), and we find an excellent agreement using realistic energies and pre-exponential factors for kinetic rate constants.

TiO2 (rutile) single crystal plates with (001) and (110) orientation were immersed in an aqueous solution of Ba(OH)2 0.5 M at temperatures of 100 and 150 °C for 1 and 4 hours in order to grow BaTiO3on them. SEM micrographs of the samples fabricated on the (001) surface of rutile displayed isolated grains with an average height ranging from 200 nm at 100 °C to 700 nm at 150 °C. On the other hand, samples with the (001) orientation exhibited no growth at 100 °C and only a few grains along lines attributed to the polishing process of the substrate at 150 °C. The image of backscattered electrons indicated that barium is concentrated on the grains in all cases. Only the (001) samples exhibited reflections of cubic BaTiO3, as indicated by x-ray dif- fraction, as well as distinct Ba signals under x-ray photoelectron spectrometry. These results agree with the hypothesis of a dissolution-precipitation growth mechanism, in which dissolution is possible for the (001) face, but not for the (110) one, which is the most stable of the low-index faces of this material. Similar treatments were applied to ZrO2:Y2O3 crystals, leading to no film growth.

Monte Carlo simulation of deposition of nonstoichiometric amorphous SiOx nanolayers from vapor phase onto a polymer surface is reported. The model developed is based on the network properties of silica and takes into account dangling bonds arising during the real process of deposition. The model is validated via comparison of the radial- and bond angle distribution functions for the simulated Si and SiO2 structures with those obtained from experiment for bulk materials. Porosity of the simulated amorphous layer is characterized by the relative volume of pores and the ratio of the pore surfaces to the pore volume. We found that porosity strongly depends on nucleation sites density (NSD) on the polymer substrate. At NSD lower than 1 nm−2 the porosity may reach as much as 30% of the layer volume, while at NSD higher than 4 nm−2 it decreases down to 3-7%. Possible implications of the obtained results are discussed.

Recent experimental work has demonstrated that unique high porosity thin films may be ob- tained in physical deposition systems by combining glancing angle deposition with in situ sub-strate motion control [1-7]. The microstructure of these films consists of isolated columns engineered into shapes such as helices, posts, or chevrons. Due to the isolated nature of the columns, the films present a unique opportunity to study fundamental thin film growth behaviour and, in particular, the influence of the self shadowing mechanism in three dimensions. Apart from this academic motivation, there is the need to characterize the physical constraints imposed on the engineering of these films. In particular, this study will have implications for the realization of isolated, periodically arranged nanostructures envisioned for certain applications. Preliminary results from an ongoing study of growth dynamics, morphology, porosity, and scaling behaviour, and the dependence of these features on deposition parameters are presented below.

The organization of Ge ‘dome’ islands in Ge/Si multilayers has been investigated by cross-sectional transmission electron microscopy. Ge ‘domes’ are found to spontaneously arrange in oblique stacks, replicating at a well-defined angle from one bilayer to the next. The formation of oblique island stacks is governed by a complex interplay of surface strain - generated by the already buried islands - and surface curvature - caused by the inherent tendency of large ‘domes’ to carve out material from the surrounding planar substrate.

Dynamics of Ga clusters and GaAs epitaxial growth on a GaAs (001) surface were successfully observed by a system in which scanning tunneling microscopy (STM) and molecular beam epitaxy (MBE) were incorporated into one unit rather than in separate chambers. With the substrate temperature of 528°C, reflection high-energy diffraction (RHEED) patterns showed a (4×6) Ga-stabilized surface reconstruction and dynamics of steps and islands were clearly observed. The detaching and attaching of small Ga clusters might cause the change of steps and islands. It seems that the small Ga clusters migrated with the diameter of about 0.8 to 1.2 nm and around the steps and islands. These clusters could be observed only when they were detached from or attached to the steps and islands. Moreover, even under the substrate temperature of 440 oC and the As4 partial pressure of 2×10−6 torr, STM images were clearly observed. After 0.1 ML Ga was additionally supplied to the sample by migration enhanced epitaxy mode, step flow growth occurred, resulting in an additional GaAs layer grown on the B-step side. Moreover, the c(4×4) As-stabilized surface reconstruction was moderate. It seems that there is an equilibrium additional layer of As amorphous adatoms on the c(4x4) surface reconstructions.