K. N. Eltsov

Atomic scale observation of iodine layer compression on Cu(1 1 1)

The atomic structure of the iodine covered Cu(1 1 1) surface was studied by STM in combination with LEED, AES and TDS techniques. It was established that iodine adsorption on Cu(1 1 1) leads to the uniaxial compression of chemisorbed iodine layer. The structure of the saturated iodine coverage on Cu(1 1 1) was described in terms of formation of the striped super heavy domain walls, with the interatomic distances in the wall being smaller than van der Waals diameter of iodine.

Atomic structure of saturated chlorine monolayer on Ag(111) surface

Abstract STM and LEED techniques were applied to study the structure of saturated chlorine monolayer formed on Ag(111) as a result of Cl 2 adsorption at room temperature. We present for the first time atomic resolution STM images of chlorinated Ag(111) surface obtained in ultra-high vacuum conditions. The structure of chlorine layer was identified by means of a Fourier analysis of the STM images as Ag(111)–(17 × 17)-Cl. The structure of saturated chlorine monolayer remains unchanged for Cl 2 exposures up to 100 000 L and coexists with AgCl islands on Ag(111) surface.

Atomic structure of silver chloride formed on Ag(111) surface upon low temperature chlorination

The structure of AgCl formed in the course of chlorine adsorption on Ag(111) surface was studied by STM. For the first time atomic resolution STM images of silver chloride were obtained. The silver chloride was detected as small (30-60 A in diameter) islands located on the atomic terraces. The upper plane of the islands was found to be AgCl(111) with interatomic distance close to the bulk value. The chloride surface lattice was not rotated with respect to the substrate. A possible mechanism of AgCl growth on Ag(111) is discussed.

Chloride formation and photoreduction on the Cu(100) surface. A study by X-ray photoelectron spectroscopy and low energy ion scattering

Abstract Multi-atomic chloride layers are prepared on the clean Cu(100) surface by exposure to Cl 2 at 160 K at pressures of the order of 10 −3 Pa. The layer stoichiometry determined by XPS measurements corresponds to CuCl. Bringing the sample to room temperature, the layer undergoes a structural transformation where thicker islands are formed, while a fraction of the substrate surface becomes free. Exposure to radiation in the soft X-rays domain causes the photoreduction of the chloride layer and the formation of metallic copper. This metallic copper is located near or over the surface of the chloride.

Epitaxy and structure of the chloride phase formed by reaction of chlorine with Cu(100). A study by X-ray photoelectron diffraction

Abstract Chloride layers of thickness of several atomic layers were prepared by low temperature reaction of Cl 2 with a clean Cu(001) surface. The structure of the chloride layer was examined by X-ray photoelectron diffraction (XPD). The results of the comparison of experimental XPD data and calculations carried out using the single scattering cluster-spherical wave (SSC-SW) model show that the chloride grows as epitaxial fcc, zincblende CuCl, with the (111) plane parallel to the substrate surface. The results also indicate that the (111) “chlorine” termination is the actual termination of the chloride phase, out of the two possible terminations of the polar zincblende structure.

Adsorption of O 2 on Ag(111): Evidence of Local Oxide Formation

The atomic structure of the disordered phase formed by oxygen on Ag(111) at low coverage is determined by a combination of low-temperature scanning tunneling microscopy and density functional theory. We demonstrate that the previous assignment of the dark objects in STM to chemisorbed oxygen atoms is incorrect and incompatible with trefoil-like structures observed in atomic-resolution images in current work. In our model, each object is an oxidelike ring formed by six oxygen atoms around the vacancy in Ag(111).

Local structure of thin AgCl films on silver surface

The new structural results revising commonly accepted point of view on role of products of silver chlorination in catalytic reaction of ethylene epoxidation are presented. It was established that AgCl nucleation on Ag(111) mainly occurs on step edges but low temperature reaction could also start on atomic terraces. On atomically resolved images of AgCl nuclei surface obtained with scanning tunneling microscope, the specific features of atomic size were observed and attributed to silver atoms and atomic clusters. We predict that such silver cluster formation could explain a very high activity of chlorinated surface in ethylene epoxidation. Interatomic distances measured in thin AgCl films were found to be equal to corresponding bulk parameters. The photoelectron diffraction patterns observed upon Ag(100) chlorination were explained by the formation of AgCl(111) domains rotated on 90° with respect to each other.

Epitaxial growth of semiconductor thin films on metals in the halogenation process. Atomic structure of copper iodide on the Cu(110) surface

The atomic structure of thin (7–20 Å) copper iodide layers formed on the Cu(110) surface during a chemical reaction with molecular iodine in ultrahigh vacuum has been studied with scanning tunneling microscopy. A double stripe superstructure with an average period of 90–100 Å was found on the surface of CuI. The structural model is proposed for the copper iodide surface taking into account the contraction of the CuI lattice and the formation of striped domain walls.

Local structure determination for surface chlorination with EELFS

Abstract In this paper the results of an investigation of the local structure of a layer of molecular chlorine condensed on Si(1 0 0) at T = 110 K and an unbroken AgCl film evaporated on Ag(1 1 1) at T = 160 K are presented. It was found that the nearest neighbor ClAg distance in the AgCl film of 2.75 ± 0.05 A is in good agreement with bulk values (2.77 A). The ClCl distance of 2.00 ± 0.05 A in a chlorine film condensed on Si(1 0 0) is also close to the bulk value (1.98 A).

Structural transformations on an oxidized Ag(111) surface

The structure of the Ag(111) surface after the adsorption of molecular oxygen at a temperature of 300 K is studied by low-temperature scanning tunneling microscopy. It is established that local surface oxide is formed at the first stage of adsorption. The subsequent adsorption of O results in the appearance of new objects with a size of 3–8 Å and a height of 1.0–1.5 Å on the Ag(111) surface, which form quasi-ordered structures with increasing degree of coating. The heating of the system obtained up to 500 K leads to a structural transition resulting in the formation of single islands of the p (4×4) phase on the surface. Surface structures are identified by a simulation based on the density functional theory.