Electrochemical formation and properties of thin polyaniline films on Au(111) and p-Si(111)

The specific aspects of phase formation phenomena involved in electrodeposition of conducting polymer layers are critically discussed. The mechanism of formation and the properties of electrodeposited thin polyaniline (PANI) films on Au(111) and p-Si(111) are investigated by means of transient measurements, cyclic voltammetry, electrochemical impedance spectroscopy and atomic force microscopy (AFM). Experimental results show that the initial stages of PANI electrodeposition on Au(111) can be described by a model including progressive appearance and preferential 2D growth of polymer islands. The electropolymerization process on p-Si(111) substrates is preceded by anodic formation of an inhomogeneous thin SiO₂ layer giving rise to a progressive appearance and growth of 3D PANI islands. The electrochemical redox properties of electrodeposited PANI films on p-Si(111) are influenced strongly by the electronic band structure of silicon. PACS 81.10.Aj; 82.45.Wx; 82.45.Vp     

The influence of substrate temperature on the structure and morphology of sexiphenyl thin films on Au(111)

The layer growth of ultra-thin films of sexiphenyl on Au(111) has been studied as a function of substrate temperature under well-defined ultra-high-vacuum conditions. In situ X-ray photoelectron spectroscopy in combination with thermal desorption spectroscopy was applied to reveal the kinetics of layer growth and recrystallisation. Ex situ atomic force microscopy and X-ray diffraction were used to determine the film morphology and film structure. A continuous small-grain film is obtained at 93 K. The crystalline structure of the grains has been confirmed by X-ray diffraction. However, the grains are not preferentially oriented with respect to the substrate. Around room temperature, recrystallisation takes place and the molecules within the crystallites orient parallel to the substrate surface. Further small substrate temperature changes during growth lead to further changes of the film morphology and to reorientation of the crystallites. However, the molecules in the crystallites stay aligned parallel to the surface. At temperatures greater than 350 K, terraced islands of standing molecules are observed, in addition to needle-like islands with flat-lying molecules. PACS 68.55.-a; 61.66.Hq; 81.10.Bk     

Ag(111)和Au(111)上铋的初始生长行为

半金属铋(Bi)的表面合金具有的Rashba效应,和其具体结构性质有重要关联.本文结合扫描隧道显微镜(STM)和密度泛函理论(DFT),系统地研究了Bi原子在Ag(111)和Au(111)上的不同初始生长行为.在室温Ag(111)上,连续的Ag2Bi合金薄膜会优先在Ag台阶边缘形成;在570 K Ag(111)上,随着...     

Growth and vibrational properties of MnOx thin films on Rh(111)

The growth, structures, and vibrational properties of ultrathin manganese oxide films on Rh(111) had been investigated using high-resolution electron energy loss spectroscopy (HREELS), X-ray photoelectron spectroscopy (XPS), low energy electron diffraction (LEED), low energy ion scattering spectroscopy (LEIS) and Auger electron spectroscopy (AES). MnO_x grew in a layer-by-layer fashion on the Rh(111) surface. HREELS phonon features and XPS binding energies showed that an OMnO like tri-layer formed initially. Which was stable on the Rh(111) surface with MnO_x coverage less than one monolayer. At above one monolayer, Mn₃O₄ was preferred as indicated from a four-phonon feature peaked at 13.3, 39, 68 and 83 meV in HREELS. Higher temperature oxidation and annealing were found to improve the long-range order of the MnO_x films.     

LEED study of the epitaxial growth of the thin film Au(111)/Ag(111) system

An analysis of LEED data from the Ag(111) surface at room temperature and 5° ? Θ ? 16°, φ = 12° has been carried out in order to test three different model potentials for the exchange and correlation part of the one-electron LEED potential. Clean Au(111) surfaces have been grown on Ag(111) at room temperature at a deposition rate of 0.15 Å s^?1. Similar method of calculation and potentials have been employed for the Au overlay er on Ag(111). After the deposition of ? 2.5 monolayers of Au/Ag(111) the growth of Au can proceed in two different ways. One of them matches satisfactorily with the theoretical calculation for the Au(111) overlayer on Ag(111) following the fcc sequence. The other seems to be concerned with the diffusion of Ag during the Au growth. Similar curves have been obtained during the diffusion of Ag through 350 Å of Au(111).     

Layer-by-layer epitaxial growth of polar FeO(111) thin films on MgO(111)

We report on the structural properties of epitaxial FeO layers grown by molecular beam epitaxy on MgO(111). The successful stabilization of polar FeO films as thick as 16 monolayers (ML), obtained by deposition and subsequent oxidation of single Fe layers, is presented. FeO/MgO(111) thin films were chemically and structurally characterized using low-energy electron diffraction, Auger electron spectroscopy and conversion electron Mössbauer spectroscopy (CEMS). Detailed in situ CEMS measurements as a function of the film thickness demonstrated a size-effect-induced evolution of the hyperfine parameters, with the thickest film exhibiting the bulk-wüstite hyperfine pattern. Ex situ CEMS investigation confirmed existence of magnetic ordering of the wüstite thin film phase at liquid nitrogen temperature.     

Growth and structure of epitaxial diamond films grown on Si(111) single crystals

Experiments on growing single-crystal diamond films on silicon crystals with (111) surface orientation have been performed. Results attesting to the possibility of obtaining thin heteroepitaxial films are presented. Pis’ma Zh. éksp. Teor. Fiz. 65, No. 5, 414–418 (10 March 1997)     

Growth mode and interface structure of Ag on the HF-treated Si(111):H surface

A growth mode and interface structure analysis has been performed for Ag deposited at a high temperature of 300°C on the HF-treated Si(111):H surface by means of medium-energy ion scattering and elastic recoil detection analysis of hydrogen. The measurements show that Ag grows in the Volmer-Weber mode and that the Ag islands on the surface are epitaxial with respect to the substrate. The preferential azimuthal orientation is A-type only when Ag is deposited slowly. The interface does not reconstruct to the √3 × √3-Ag structure, which is normally observed for Ag deposition above 200°C on the Si(111)7 × 7 surface, but retain bulk-like structure. The presence of hydrogen at the interface is demonstrated after deposition of thick (1100 Å) Ag films. However, the amount of hydrogen at the interface is not a full monolayer. This partial desorption of hydrogen from the interface explains why the Schottky barrier heights of Ag/Si(111):H diodes are close to those of Ag/Si(111)7 × 7 and Ag/Si(111)2 × 1.