The galvanostatic electrodeposition of two-dimensional (2D) gold films along the surface of aqueous hydrogen tetrachloroaurate solutions coated by a positively charged dimethyldioctadecylammonium (DODA) monolayer is reported. When a constant current is applied to the working electrode, a transition between two-dimensional (2D) growth and three-dimensional (3D) thickening of the deposits is observed. This event occurs when the current density is sufficiently small to allow the 3D process to consume all the injected electrical charges. The application of a current ramp with a rate such as the current density remains during the whole growth close to the limiting value separating the two growth regimes induces the appearance of spontaneous oscillations between the regimes of 2D and 3D growth. Deposits with a well-defined terraced structure are then obtained.

The initial periods of deposition process of metal clusters in the soft-landing regime are investigated by the molecular-dynamics simulation. The embedded-atom method potential is adopted for calculation of the interaction between metallic atoms. The predictor-corrector method for second-order differential equations is employed for integration of the equations of motion. A simulation begins with equilibration of clusters and a substrate at a specified temperature. The lowest atomic layer in the substrate is fixed and the next few atomic layers are set to be velocity-scaling layers during the deposition process. The periodic boundary conditions are imposed in the horizontal directions. A single cluster with no velocity is deposited on the substrate. The simulations are performed at different temperatures of the clusters and substrate and for different sizes of clusters. How the morphological transition of the deposited nanostructures is affected by these parameters is discussed.

We propose a new kinetic model for surface segregation during vapor phase growth that accounts for multiple segregation mechanisms, including mechanisms for terrace mediated exchange and step edge mediated exchange. The major result of the model is an analytic expression for the experimentally measured segregation length and profile broadening that can be readily calculated without the need for numerical simulations. We compare the model to experimental measurements for the temperature dependence of segregation of Sb in Si(001). The model is able to accurately describe both the anomalous segregation at low temperature and the transition between equilibrium and kinetically limited segregation at high temperature. An excellent agreement is obtained using realistic energies and pre-exponential factors for the kinetic rate constants. The model can be applied to other segregating systems in planar geometries, including metallic and III-V semiconducting thin films.

A powder composite AlCuFe target was used to produce 10 micron films of a quasicrystalline precursor phase by RF sputtering onto polycrystalline alumina substrates. X-ray studies have determined this precursor to be a nano-quasicrystalline phase, despite previous reports of an amorphous structure. Anneals for various times at temperatures between 450°C and 550°C showed the evolution and grain growth of the quasicrystalline approximant structure as a function of both variables. Synchrotron diffraction studies showed a bimodal grain size distribution of the quasicrystalline approximant structure for anneals at 450 °C for 1 hour, below a previously reported transition temperature of 475 °C. Composition analysis of annealed films by XPS depth profiling showed the surface composition to be nearly stoichiometric Al2O3 and extensive oxygen penetration to 160 nm. X-ray diffraction studies have been correlated with cross section microscopy to characterize the development of quasicrystalline films from their precursors. Anneals for longer times and at higher temperatures showed no evidence of a bimodal distribution or remaining nanoquasicrystalline phases.

We synthesized diamond via gaseous phase of vaporized acetone. Molecular acetone decomposes to two methyl radicals with thermal activation. We propose here a new method for diamond synthesis with these methyl radicals from molecular acetone. With this method, we successfully synthesized diamond particles on Si substrates with shorter experimental time and lower energy consumption than conventional methods. With liquid carbon sources, such as acetone, impurity elements will be easily substituted in synthesized diamond thin film, which has wide applications for the future electronic devices. Nickel, Boron and Phosphorus doping results will be presented.

Stress and energy distributions for crystallization of a thin amorphous film are calculated by means of 3D finite element method. The changes in energy are caused by elastic strain induced by different thermal expansion of the film and the substrate and by different mass densities of the crystal and the surrounding amorphous matrix. The calculations were performed for cubic crystal structure and for disc shaped crystals. Three crystal orientations (001), (011) and (111) were considered. Based on strain energy considerations the (001) orientation of crystals with respect to the film plane is energetically more favorable than (011) and (111) orientations. Interfacial and surface energies are certain to play a part in these effects as well.

The initial stages of iron silicide growth on Si(111) were investigated using LEED, AES and STM experiments together with DFT calculations. In 1:1 stoichiometry, a cubic FeSi develops showing a (1×1) surface periodicity which is stable up to 300°C. The epitaxial strain energy stabilizes this bulk-unstable B2 (CsCl-type) phase for up to 250 Å thickness. The surface is Si terminated, the interface coordination of the so-called B8 type. After annealing at ≈ 600°C, a (2×2)-FeSi2 phase of higher Si content is observed which possesses cubic crystal structure. It is stable below 10 monolayers (ML) initial Fe coverage and grows in an island-like morphology. In the initial growth stage, however, a c(8×4) phase forms that completely covers the surface at 1.5 ML Fe content and appears as potential template for further growth of homogeneous films. The interpretation of atomically resolved STM images suggests that the film contains three Si and two Fe layers in B2 structure with vacancies on Fe positions. The vacancy arrangement seems to be responsible for the c(8×4) periodicity displayed by the Si adatoms in T4-position.

An isothermal Molecular Dynamics simulation method has been applied to the study of motions of steps on Si(100). The steps have a monolayer height and their temperature is below the roughening transition (i.e. T≤ 1000K). The calculations predict spontaneous motions even in this low temperature range and describe the functional dependence of the displacements of step-edge atoms on the step geometry, size and temperature and on the nature of the interatomic forces. Owing to the use of the Fourier analysis, these results can be applied to structures of realistic size by a proper scaling of the wavevectors.

We have studied the first phases of post-growth evolution of InAs quantum dots (QDs) using in-situ Auger electron spectroscopy in conjunction with Reflection High Energy Electron Diffraction (RHEED). Direct evidence for InAs intermixing with about 6ML (monolayers) of the matrix material is found from Auger signal behavior during MBE overgrowth of InAs nanostructures. Re-establishment of 2D growth mode by overgrowth with GaAs or AlAs was monitored in single-layer and multi-layer QD structures using RHEED. Decay process of InAs QDs on the surface is found to have activation energy of about 1.1 eV that corresponds to In intermixing with the matrix rather than evaporation from the surface.

The kinetics of intermediate phase formation in the Cu/Mg multilayer system is analyzed using Differential Scanning Calorimetry. Three main exothermic processes are found during the continuous DSC treatments. The first two, significantly overlapped, are related to the same process, nucleation and growth of the Mg2Cu along the interface. We interpret differences between the Mg/Cu and Cu/Mg interfaces are at the origin of this unexpected behavior. The third exothermic reaction is due to the growth of the Mg2Cu phase perpendicular to the original interface. A kinetic model is developed which yields calorimetric traces in good agreement with the experimental data.

In order to further investigate the origin of growth instabilities in aluminium rich Ti/Al-alloy films, formed by simultaneous deposition of the two alloy components, from separate evaporation sources, we have investigated the growth stress of multilayer-films under UHV-conditions, formed by a variable number of double layers of Ti and Al, by in situ internal stress measurements. The thickness of the respective Ti/Al-double layer was varied between 6.25 nm and 25 nm and the thickness of the respective titanium and aluminium layer was chosen to achieve an overall composition of Ti25Al75 in a 150 nm thick film. The multilayer films were deposited on 10 nm thick alumina substrate films at substrate temperatures of 350°C and 450°C. Microstructure and phase formation was investigated by TEM/TED-experiments.

In summary, these experiments show diffusion of aluminium (compressive stress) into the underlying film during deposition of the first monolayers and then formation (stress free or small tensile stress) of aluminium precipitates on the surface of the multilayer film during each aluminium deposition. During the subsequent titanium deposition the aluminium surface precipitates spread in a circular region under alloy formation (tensile stress) (see also accompanying paper). The respective stress contributions are strongly dependent on the double-layer thickness and substrate temperature. The increasing magnitude of the different stress contributions in the early growth stage are interpreted to indicate that the various processes are limited to specific surface regions, which get larger as the number of double-layers increases. The average film stress built up in the respective multilayer film by superposition of the stress contributions mentioned above, is also strongly dependent on double layer thickness and substrate temperature.

Scanning tunneling microscopy experiments show that the unstable growth morphology observed during molecular beam homoepitaxy on slightly vicinal Si(001) surfaces consists of straight step bunches. The instability occurs under step-flow growth conditions and vanishes both during low-temperature island growth and at high temperatures. An instability with the same characteristics is observed in a 2D Kinetic Monte Carlo model of growth with incorporated Si(001)-like diffusion anisotropy. This provides strong evidence that the diffusion anisotropy destabilizes growth on Si(001) and similar surfaces towards step bunching. This new instability mechanism is operational without any additional step edge barriers.

Differences in the homoepitaxy of Ge(001) are explored using a dual MBE/PLD deposition system. With identical substrate preparation, temperature calibration, background pressure and analysis, the system provides a unique comparison of the processes arising only from kinetic differences in the flux and at the surface. All films show mounded growth. At substrate temperatures below 200°C, PLD films are smoother than MBE films, whereas they are similar at higher temperatures.

Etching water soluble Ge-oxides was used to investigate Si interdiffusion into epitaxial Ge / Si(100) samples. The Ge coverage, θGe, was measured using Rutherford backscattering spectrometry (RBS) before and after water etching of samples grown at substrate temperatures between 400 °C and 650 °C. θGe was correlated with sample morphology determined using atomic force microscopy (AFM). The local Ge concentration was qualitatively assessed using energy dispersive x-ray (EDX) analysis. For samples grown at T=400 °C, water completely dissolves the islands and no Ge is detected by RBS. For samples grown at T=600 and 650 °C, AFM detects no change in the surface morphology and RBS indicates that θGe decreases by about 3 monolayers (ML). These results suggest that for growth at T=400 °C, both the islands and wetting layer are relatively pure Ge while for growth at T≥600 °C, the wetting layer is Ge rich compare to the SiGe alloy islands. EDX confirms this conclusion detecting no Ge signal between islands for etched samples grown at T≥600 °C. Our results suggest that for growth at T≥600 °C, Si interdiffusion into islands is through the region underneath the islands instead of from the wetting layer.

A preliminary TEM investigation of porous films fabricated by glancing angle deposition has shown the importance of surface diffusion and crystal structure in determining the final microstructure of the film. Although the process variables are extremely important in defining the morphology of the film, their effects are limited in terms of final microstructure.

Self-organized nanostructures are increasingly important for novel optoelectronic devices, as high densities of quantum dots can be deposited directly during heteroepitaxial growth. Due to the elastic relaxation in 3D nanostructures, properties differing from 2D systems can be achieved, e.g., higher Ge contents in SiGe islands than in planar layers with the same total amount of Ge can be realized, enhancing the design freedom for, e.g., detectors or high frequency transistors. However, when such nanostructures are overgrown, which is inevitable for any application, they often undergo significant changes, partly eliminating their distinct advantages. We present an investigation of SiGe islands formed by deposition of pure Ge on Si (001). X-ray scattering and diffraction is employed to obtain the shape, strain and Ge distribution in uncapped as well as Si-capped islands. For the analysis, model calculations of the strain fields are required. The finite element method is used for uncapped islands, for buried nanostructures a novel analytical approach has been developed. For Tgrowth ∼ 650°C, optimized for island formation, the Ge content in the top part of uncapped islands reaches 100%, at an elastic relaxation of about 50%. During capping, the maximum Ge content considerably decreases to about 50%. At the same time, the islands become very flat, with a decrease in height from 13 to 6nm accompanied by an increase in base diameter from about 100 nm to 180 nm. The elastic relaxation decreases to about 2.5%, so that the buried islands have properties not very much different from 2D layers. Lowering the growth temperature for the Si cap, this effect can be avoided, for Tgrowth as low as 460°C, the structure of the uncapped islands can indeed be preserved.

First-principles calculations are used to calculate the strain dependencies of the binding and diffusion-activation energies for Ge adatoms on both Si(001) and Ge(001) c(4×2) reconstructed surfaces. Our calculations reveal that over the range of strains typically sampled during quantum dot self-assembly (0 to 1% compressive strain) the binding and activation energies on a strained Ge(001) surface increase and decrease, respectively, by 0.21 eV and 0.12 eV. For a growth temperature of 600 °C, these strain-dependencies give rise to a 16-fold increase in adatom density and a 5-fold decrease in adatom diffusivity in the region of compressive strain surrounding a Ge island with a characteristic size of 10 nm lying on top of a Si substrate covered by a Ge wetting layer.

Many vapor-deposited metal-on-insulator films exhibit a morphological progression with increasing thickness consisting of several distinct stages: (1) nucleation of 3-dimensional na-nocrystalline islands; (2) elongation of the islands; (3) film percolation. Here we report a study of this progression during Pulsed Laser Deposition (PLD), a technique for film deposition that differs from thermal deposition in that the depositing species arrive in short energetic bursts, leading to instantaneous deposition fluxes orders of magnitude higher than can be achieved in thermal growth. Atomic Force Microscopy reveals that advancement through this same morphological progression occurs at lower thickness in PLD films relative to films grown under comparable conditions by thermal deposition, with PLD films having lower RMS roughness at a given thickness. We also observe that for a constant amount deposited per pulse, films deposited at higher laser pulse frequency are further advanced in morphological state. Kinetic Monte Carlo simulations reveal that PLD nucleation behavior differs from that of thermally deposited films, and this can account for the observed differences. Simulations also reveal a scaling of the percolation thickness with pulse frequency that is consistent with experiment.

The results are presented of a study on grain growth in magnetron sputter deposited Cu films. Similarly to the well-known case of electroplated Cu, we observed significant changes in the microstructure of sputter deposited films during storage at room temperature, as evidenced by a decrease in sheet resistance (up to 40% decrease in less than 6 hours). Direct evidence for grain growth was observed by FIB and SEM and by a strong decrease in the XRD peak width. Moreover, a decrease in the total defect content of the film was observed as a function of storage time from positron annihilation experiments, probably reflecting the decreasing number of grain boundaries in the film. It is well known that the microstructure of an as-deposited film is strongly dependent on the deposition parameters. This relationship is summarized in the Thornton structure-growth zone diagram [7]. We have studied the kinetics of room temperature grain growth as a function of Ar pressure and substrate temperature for Cu films with a thickness between 50 nm and 1 micrometer. It is found that spontaneous grain growth during storage at room temperature occurs mainly for a zone T microstructure (at low Ar pressure and a substrate temperature below 40°C), while it does not occur for zone I (high Ar pressure, low substrate temperature) or zone II (substrate temperature > 100°C) microstructures.

Surface processing is generally kinetics limited. Migration barriers, both on flat surfaces and near steps, therefore are of crucial importance. In this paper, we describe a kinetic barrier that separates two neighboring facets on surfaces. The contrast of this concept relative to the conventional Ehrlich-Schwoebel barrier is shown through molecular dynamics/statics calculations on copper and aluminum. The effects of this new kinetic barrier are demonstrated through lattice Monte Carlo simulations. The predicted effects are in direct correspondence with validation experiments on copper and silver thin films.