I. Ošt’ádal

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)-

Pair Correlation Function of a 2D Molecular Gas Directly Visualized by Scanning Tunneling Microscopy

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Reconstruction-Determined Growth of Silver on Silicon(111)—(7×7)

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

Unconventional features of Ag epitaxy on the Si(111)7×7 surface

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Stability of In rows on Si(1 0 0) during STM observation

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.

Direct observation of Ag intercell hopping on the Si(111)-(7×7) surface

The state of matter in fluid phases, determined by the interactions between particles, can be characterized by a pair correlation function (PCF). At the nanoscale, the PCF has been so far obtained experimentally only by means of reciprocal-space techniques. We use scanning tunneling microscopy (STM) at room temperature in combination with lattice-gas kinetic Monte Carlo (KMC) simulations to study a two-dimensional gas of highly mobile molecules of fluorinated copper phthalocyanine on a Si(111)/Tl-(1×1) surface. A relatively slow mechanism of STM image acquisition results in time-averaging of molecular occurrence under the STM tip. We prove by the KMC simulations that in the proximity of fixed molecules STM images represent the PCF. We demonstrate that STM is capable of visualizing directly the pair correlation function in real space.

Ultrasharp tungsten tips—Characterization and nondestructive cleaning

The heteroepitaxial growth of Ag on Si(111)—(7×7) is strongly affected by the surface reconstruction, which introduces additional constraints into the motion of deposited atoms. To characterize the processes and parameters crucial for growth, we study Ag/Si(111)—(7×7) heteroepitaxy from nucleation up to coverages of a few monolayers. The experimental results obtained by scanning tunneling microscopy are interpreted using a coarse-grained kinetic Monte Carlo model. The attempt frequency and the barrier to hopping of a single Ag atom between half-unit cells (HUCs) are estimated. Erom our experiments and simulations we infer the existence of a non-thermal post-deposition mobility of Ag atoms and a stable configuration of 6 Ag atoms in a HUC. The morphology of the wetting layer and the three-dimensional island density during further Stranski-Krastanov growth at various temperatures are discussed.