P. Sobotík

Heterogeneous nucleation and adatom detachment at one-dimensional growth of In on Si(100)-2 X 1

Growth of atomic indium chains - 1D islands - on the Si(100)-2x1 surface was observed by scanning tunneling microscopy (STM) at room temperature and simulated by means of a kinetic Monte Carlo method. Density of indium islands and island size distribution were obtained for various deposition rates and coverage. STM observation of growth during deposition of indium provided information on growth kinetics and relaxation of grown layers. Important role of C-type defects at adsorption of metal atoms was observed. Measured growth characteristics were simulated using a microscopic model with anisotropic surface diffusion and forbidden zones along the metal chains. An analysis of experimental and simulation data shows that detachment of indium adatoms from the chains substantially influences a growth scenario and results in monotonously decreasing chain length distribution function at low coverage. Diffusion barriers determined from the simulations correspond to almost isotropic diffusion of indium adatoms on the surface. The results are discussed with respect to data reported in earlier papers for other metals.

Chemical identification of single atoms in heterogeneous III-IV chains on Si(100) surface by means of nc-AFM and DFT calculations.

Chemical identification of individual atoms in mixed In-Sn chains grown on a Si(100)-(2 × 1) surface was investigated by means of room temperature dynamic noncontact AFM measurements and DFT calculations. We demonstrate that the chemical nature of each atom in the chain can be identified by means of measurements of the short-range forces acting between an AFM tip and the atom. On the basis of this method, we revealed incorporation of silicon atoms from the substrate into the metal chains. Analysis of the measured and calculated short-range forces indicates that even different chemical states of a single atom can be distinguished.

Self-organized growth of Ag islands on Si(1 1 1)-(7 × 7)-optimization of an STM experiment by means of KMC simulations

A growth model and parameters obtained in our previous experimental (scanning tunneling microscopy, KMC) and theoretical (kinetic Monte Carlo simulations, KMC) studies of Ag/Si(111)-(7x7) heteroepitaxy were used to optimise growth conditions (temperature and deposition rate) for the most ordered self-organized growth of Ag island arrays on the (7x7) reconstructed surface. The conditions were estimated by means of KMC simulations using the preference in occupation of half unit cells (HUCs) of F-type as a criterion of island ordering. Morphology of experimentally prepared island structures was studied by STM. High degree of experimentally obtained island ordering is compared with the simulated data and results are discussed with respect to the model and parameters used at the KMC simulations.

Continuous and correlated nucleation during nonstandard island growth at Ag/si(111)-7×7 heteroepitaxy

We present a combined experimental and theoretical study of submonolayer heteroepitaxial growth of Ag on Si(111)-

STM study of nucleation of Ag on Si(111)−(7 × 7) surface

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Early Stages of Submonolayer Growth of Ag on Si(111) 7×7 Observed by Scanning Tunneling Microscopy In Vivo

at temperatures from 420 K to 550 K when Ag atoms can easily diffuse on the surface and the reconstruction

Electric-field-controlled phase transition in a 2D molecular layer

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Ag/Si(111)-(7X7) Heteroepitaxy—STM Experiment and KMC Simulations

remains stable. Scanning tunneling microscopy measurements for coverages from 0.05 ML to 0.6 ML (ML---monolayer) show that there is an excess of smallest islands (each of them fills up just one half unit cell---HUC) in all stages of growth. Formation of a two-dimensional (2D) wetting layer proceeds by continuous nucleation of the smallest islands in the proximity of larger 2D islands (extended over several HUCs) and following coalescence with them. Such a growth scenario is verified by kinetic Monte Carlo simulation which uses a coarse-grained model based on a limited capacity of HUC and a mechanism which increases nucleation probability in a neighborhood of already saturated HUCs (correlated nucleation). The model provides a good fit for experimental dependences of the relative number of Ag-occupied HUCs and the preference in occupation of faulted HUCs on temperature and amount of deposited Ag. Parameters obtained for the hopping of Ag adatoms between HUCs agree with those reported earlier for initial stages of growth. The model provides two parameters---maximum number of Ag atoms inside HUC, and on HUC boundary.

Reconstruction-Determined Diffusion of Ag Adatoms on the Si(111)-(7X7) Surface

Initial stages of Ag on Si(111)−(7 × 7) surface nucleation were studied at submonolayer coverage. Samples were prepared by thermal evaporation of Ag from tungsten wire under UHV conditions (p<2.5 × 10−8 Pa). Various deposition rates (0.002–0.1 ML s−1) were used to prepare Ag island films with coverages (0.002–2) ML (1 ML ≈ 7.58 × 1014 atoms cm−2) at room temperature. We observed preferential growth on faulted half unit cells (F cells). At constant coverage both the island density and ratio of occupied F and U (unfaulted) cells are independent of the deposition rate, which is an evidence for dominant influence of substrate structure. The preference of nucleation in the F cells against U cells decreases with the coverage until the ratio is 1:1 for 1 ML Ag film. We have observed that presence of an Ag island in any type of the half unit cell (F or U) considerably reduces nucleation probability in neighbouring cells. This results in forming of structural patterns observed among randomly grown Ag-islands which is a new feature found for Ag/Si(111)−(7 × 7) system.

Aggregation of gold condensate on HOPG substrate

Scanning tunneling microscopy (STM) was used for directly imaging the early stages of heteroepitaxial growth of Ag on a Si(111) 7×7 surface during deposition by vacuum evaporation. Image sequences showed the behavior of single Ag adatoms after arriving on the surface and the formation of Ag clusters. STM measurements were performed at room temperature and 330 K. New data showed an attractive interaction between a cluster containing at least two Ag atoms and a monomer occupying an adjacent half-unit cell of surface reconstruction. The interaction modified the Ag adatom mobility on the surface and controled the growth scenario from the moment when the relative number of occupied half-unit cells is ≈0.5. The observation of the individual Ag adatom history on the surface enabled the interpretation of STM imaging of the smallest Ag objects, i.e., monomers, dimers, and trimers. The previously reported models of metal growth on the Si(111) 7×7 surface derived from in situ STM measurements are discussed with respect to the new data.