Automated islands generalization techniques for nautical charts

Existing methods for automatically selecting islands for nautical charts utilize the Voronoi diagram. However, we will show that the Voronoi diagrams cannot accurately represent the density and distribution of islands in cartographic generalization, which makes it difficult to obtain selection results that meet requirements. We propose a novel method for selecting islands based on influence domains. First, the shortcomings of the Voronoi diagram representation of spatial data are analyzed using an island influence domain (IID) model. Second, the model is defined and constructed, and the importance of an island is weighed according to its attributes. Third, several islands are selected automatically by choosing those with the largest area of IID and deleting those whose IIDs overlapped more with pre-selected islands. Finally, several groups of islands with different types of sea areas are selected for experimentation, and the required selection parameters are determined and analyzed to derive an empirical formula for setting the parameters. The experimental results show that: (1) the proposed method improves the quality of island selection; (2) the empirical formula can be used in parameter setting to obtain acceptable results.

Ruthenium is an alternative liner material for copper metallization. We report on the nucleation and growth of copper on ruthenium in acidified copper sulfate solution and explore the influence of the PEG-Cl-SPS additive system. We show that the physical vapor deposition ruthenium has an oxide layer approximately thick. The additives and copper concentration have a relatively small influence on island density but a significant influence on the island morphology. Without additives, both randomly oriented hemispherical islands and disk-shaped islands with a (111) orientation are observed. The distribution of islands is dependent on potential. In the presence of additives, the islands are irregular in shape due to renucleation that becomes more pronounced at higher concentrations and lower overpotentials. Analysis of the island size distributions implies that nucleation is fast in comparison to growth. The island density is exponentially dependent on potential increasing from at low overpotentials to almost at larger overpotentials. The distribution of islands at the surface is shown to be consistent with complete spatial randomness.

ABSTRACTSi based nanostructures such as Ge or Si1-xGex dots embedded in Si receive a lot of attention. This interest is driven by the reduction of device sizes as well as by their possible use in opto-electronic applications, as a possible solution to improve the radiative light emission. In this paper we give a detailed overview of the growth kinetics as observed for Ge growth in a standard production oriented chemical vapor deposition system. The island morphology and density are controlled by varying the growth conditions or by applying a thermal anneal after the island growth. Island densities up to 2.3x1010 cm−2 have been obtained for depositions at 650°C. With increasing deposition time, the usual change-over from monomodal to bimodal island distribution is pointed out and this change-over depends on the critical island diameter, which decreases with decreasing growth temperature. Applying a thermal budget after the island growth initiates Ge surface diffusion and Si diffusion from the substrate through the islands. This results in an enhancement of the island diameter and height, and also in a reduction of island density. Furthermore, depending on the island distribution after Ge deposition, a transition from pyramid to dome or visa versa is observed after the in-situ anneal. Optical device structures require a Si cap layer. However, Si capping at 700°C, leads to a nearly total dissolution of small islands and a truncation of bigger dome-shaped islands. This can be prevented by reducing the deposition temperature and by changing the Si gas source. Clear island luminescence, is observed up to 200K and lies in the spectral range of 1.35-1.50μm, which is interesting from the point of view of applications. In particular, this shows the potential of this material system for opto-electronic device applications. In spite of the fact that the observed PL intensity is comparable to the best reported values, we could further enhance it by a thermal treatment in a H2 plasma.

Nucleation and growth during bulk electrodeposition is studied using kinetic Monte Carlo (KMC) simulations. Ion transport in solution is modeled using Brownian dynamics, and the kinetics of nucleation and growth are dependent on the probabilities of metal-on-substrate and metal-on-metal deposition. Using this approach, we make no assumptions about the nucleation rate, island density, or island distribution. The influence of the attachment probabilities and concentration on the time-dependent island density and current transients is reported. Various models have been assessed by recovering the nucleation rate and island density from the current-time transients.

Scanning tunneling microscopy (STM) in conjunction with molecular beam epitaxy has been used to investigate InAs islands and wetting layers on GaAs(001) substrates. STM results reveal that the size, density and shape of InAs islands strongly depend on the growth temperature of InAs. With increasing the growth temperature, the island density decreases, the size increases, and the shape becomes round rather than elliptical. In the photoluminescence (PL) results, a PL peak shift is observed with increasing InAs growth temperature. This shift agrees with the STM observation that larger islands are grown at higher growth temperatures. The change in the size and density of islands can be explained in terms of a critical nucleus in heterogeneous nucleation. These results indicate that controlling the growth temperature makes it possible to control the size, density and shape of InAs islands.

ABSTRACTFor Physical Vapor Deposition (PVD) processes the nucleation and growth of stable islands on monocrystalline and even polycrystalline substrates can be described by the rate equation theory in a mean field approximation. The observable quantity which can be derived from the rate equations is the global density of stable islands. Interisland correlations and island size distributions, on the other hand, cannot be obtained from this formalism. The array of stable islands, in turn, forms the template for the subsequent growth of a polycrystalline thin film. For the initial grain shape and grain size therefore both, the global island density as well as possible interisland correlations play a key role.This paper presents the results of simulations which take into account the effects of both, the global island density as well as island/island correlations on the growth of a thick polycrystalline film. The simulations consist of two steps: first a polycrystalline template is generated from an initial distribution of stable islands by employing an algorithm for the construction of Voronoi-zones. The Voronoi zone network mimics the state of the film just after island coalescence and just before the onset of grain growth. Then the well known q-state Potts model of grain growth is employed to study the further steps of microstructural evolution.A higher initial island density leads to a faster onset of grain growth while a very homogenous distribution of islands significantly retards grain growth. The reasons for these effects are briefly discussed.

The joint probability distribution (JPD) for island sizes, s, and capture zone areas, A, provides extensive information on the distribution of islands formed during submonolayer deposition. For irreversible island formation via homogeneous nucleation, this JPD is shown to display scaling of the type ${F(s/s}_{\mathrm{av}}{,A/A}_{\mathrm{av}}),$ where ``av'' denotes average values. The form of F reflects both a broad monomodal distribution of island sizes, and a significant spread of capture zone areas for each island size. A key ingredient determining this scaling behavior is the impact of each nucleation event on existing capture zone areas, which we quantify by kinetic Monte Carlo simulations. Combining this characterization of the spatial aspects of nucleation with a simplified but realistic factorization ansatz for the JPD, we provide a concise rate equation formulation for the variation of both the capture zone area and the island density with island size. This is achieved by analysis of the first two moments of the evolution equations for the JPD.

We study the energetics of island formation in Stranski-Krastanow growth of highly mismatched heteroepitaxy within a parameter-free approach. It is shown that the (frequently found) rather narrow size distribution of the self-assembled coherent islands can be understood as the result of the system being trapped in a constrained equilibrium state with a fixed island density. If allowing for variations of the island density, we find that larger islands combined with a lower island density are more stable; this implies that Ostwald ripening will take place on time scales sufficiently long for exchange of atoms between different islands to occur. Moreover, we show how to select the island size by controlling the growth conditions and the amount of deposited material. Our study also indicates that the island shape depends on the island size, i.e., an island with larger volume has a higher value of the height-to-base ratio.

Scanning tunneling miscroscopy study of InAs islands grown on GaAs(001) substrates

Many of the electronic chart position deviations that observed today come from past graphic collecting techniques of Nautical Chart.This study introduces an assessment of the challenges of hydrography and accuracy of the chart information based on requirements on nautical charts in Tanzania. The assessment of the challenges of hydrography and accuracy of the chart information is particularly important to strengthen data accuracy and meet the requirement of nautical charts in Tanzania. Primary data were collected through face-to-face interviews with the respondents and questionnaires as a tool. Secondary data obtained through, journals, articles, and report both published and unpublished. Quantitative data were analyzed by using SPSS whereas qualitative data analyzed by using content analysis. Data provided in this article will improve nautical navigational charts practices in Tanzania and reduce variation greatly in accuracy to help mariners make informed decisions based on the data in their on-board navigation systems. The article is relevant to the new IHO guide on how to assess the accuracy and reliability of depth and position information in nautical navigation charts. The recommendations have been arranged that nautical charts, which offer much considerable information for the safe navigation of ships, are able to work more efficiently. Key words: Hydrography, Chart Information, Nautical charts, Tanzania

We study the effect of hindered aggregation and/or nucleation on the island formation process in a two-step growth protocol. In the proposed model, the attachment of monomers to islands and/or other monomers is hindered by additional energy barriers which decrease the hopping rate of the monomers to the occupied sites of the lattice. For zero and weak barriers, the attachment is limited by diffusion while for strong barriers it is limited by reaction. We describe the time evolution of the system in terms of the monomer and island densities, N_{1} and N. We also calculate the gap length, the capture zone and the island distributions. For all the sets of barriers considered, the results given by the proposed analytical model are compared with those from kinetic Monte Carlo simulations. We found that the behavior of the system depends on the ratio of the nucleation barrier to the aggregation barrier. The two-step growth protocol allows more control and understanding on the island formation mechanism because it intrinsically separates the nucleation and aggregation processes in different time regimes.

We present an analysis both of the nucleation and growth of two-dimensional (2D) islands or clusters during deposition of Ag on Ag(100) at 295 K and of the subsequent postdeposition equilibration of such island distributions at coverages below about 0.25 monolayer. Island formation during deposition is shown to be effectively irreversible, and the island density and size and separation distributions are characterized using a combination of scanning tunneling microscopy (STM) and high-resolution low-energy electron diffraction. Postdeposition coarsening of the adlayer is monitored via STM and is shown to be dominated typically by diffusion and subsequent coalescence of large 2D clusters rather than by Ostwald ripening. Tailored studies of such coarsening elucidate both the kinetics and the underlying cluster diffusion process.

Surface reconstructions can drastically modify growth kinetics during initial stages of epitaxial growth as well as during the process of surface equilibration after termination of growth. We investigate the effect of activation barriers hindering attachment of material to existing islands on the density and size distribution of islands in a model of homoepitaxial growth on Si(111)7x7 reconstructed surface. An unusual distribution of island sizes peaked around "magic" sizes and a steep dependence of the island density on the growth rate are observed. "Magic" islands (of a different shape as compared to those obtained during growth) are observed also during surface equilibration.

The critical doses required to form a continuous buried stoichiometric oxide layer for 70 keV oxygen implantation either during implantation, , or after implantation and annealing, are and , respectively. The dislocation density in the silicon overlayer and the distribution and density of silicon islands in the buried layer of the annealed (70 keV) SIMOX (separated by implantation of oxygen) samples are strongly dependent on the oxygen dose (Φ) and the target temperature . Good quality thin‐film SIMOX layers with a low threading dislocation density in the silicon overlayer and low density of silicon islands in the buried layer have been produced by implantation of at 680°C.

Copper overlayers deposited on nearly stoichiometric SrTiO3(001) have been investigated with scanning tunneling microscopy (STM). Vapor deposition of Cu on a SrTiO3(001) surface at ambient temperature leads to the formation of three dimensional islands (clusters). The distribution of Cu islands appears to be inhomogeneous with two characteristic morphologies. In regions with a low density of Cu islands the Cu was always associated with step edges or defect sites. In regions with a high density of Cu islands the islands exhibit a random but nearly close packed morphology. The variation of Cu island density is indicative of diffusion of Cu clusters on the SrTiO3(001) surface. Diffusion was further confirmed by annealing the Cu/SrTiO3 at elevated temperatures yielding agglomeration of Cu clusters.