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The growth mode of Ag atoms on the W(110) plane has been studied using LEED and Low Energy Ion Scattering Spectroscopy (ISS). We find that Ag atoms grow in SK mode after annealing at 700°C for the coverage ~ 3.0 ML. The grown three-dimensional Ag islands have the (111) plane surface. The direction of the Ag islands is rotated 4.4° from (001) direction of the W(110) surface. Using the ISS technique the surface structure of the two-dimensional Ag islands is investigated. The Ag adsorption height measured from the first layer of the W(110) surface is found to be 2.79 Å.

In this work we study the adsorption of Cs on S-covered Si(100)-(2 × 1) and Si(100)-(1 × 1) surfaces, as well as the adsorption of S on Cs-covered Si(100)-(2 × 1). The experiment was performed in an ultrahigh vacuum (UHV) chamber with low energy electron diffraction (LEED), Auger electron spectroscopy (AES) and work function (WF) measurements. Predeposited S increases the binding energy and the maximum amount of Cs that can be deposited on the surface. The presence of S inhibits the pattern of the characteristic WF curve of Cs on clean Si(100)-(2 × 1), i.e. an initial decrease to a minimum value, Φ_min, followed by an increase toward the value Φ_max of metallic Cs. The WF, instead, decreases to a value close to that of saturated Cs on clean Si(100)-(2 × 1), where it forms a plateau. This is characteristic of the covalent bonding of Cs with the semiconductor substrate. Independently of the sequence of Cs and S deposition, (a) the transition Si(100)-(2 × 1) → Si(100)-(1 × 1) occurs when Θ_S > 0.5 ML, and (b) the sites of Cs and S remain the same, with the Cs atoms residing between the S atoms. Heating of the S/Cs/Si composite surfaces to ~ 650 K causes a reorganization of the Cs and S adatoms in a tendency to form a Cs–S complex. The issue of site preference for Cs and S adatoms has been discussed in detail in the structural models provided.

In 6H- or 4H-SiC(0001) surface technology, a Si-rich 3 × 3 reconstruction is usually first prepared by heating at 800°C under Si flux, and two other most stable or reconstructions are obtained by further extensive annealing at higher temperatures ranging between 900 and 1250°C. The 3 × 3 Si excess is thus progressively depleted up to a graphitized C-rich surface. By crystallographic (LEED) and chemical surface characterizations (XPS and UPS), we show that all these reconstructions can be obtained at a unique, low formation temperature of 800°C if the Si richness is controlled before annealing. This control is achieved by exposing the 3 × 3 surface to atomic hydrogen at room temperature. This procedure allows one to etch or partially deplete the (3 × 3)-associated Si excess, and make it more comparable to the final Si coverages, required to form the less Si-rich or reconstructions. After annealing at 800°C, the latter reconstructions are no longer determined by the heating time or temperature but only by the initial Si coverage set by the H doses inducing the low temperature etching. The high temperature treatment, required to remove by sublimation a significant Si amount associated with the Si-rich 3 × 3 reconstruction, is thus avoided. Such a methodology could be applied to other binary systems in the formation of reconstructions that depends on surface richness.

The surface segregation, structure, and valence band density of states of Pt₃Ni(100), (110), and (111) single crystals are characterized with low energy ion scattering (LEIS), low energy electron diffraction (LEED), and ultraviolet photoemission spectroscopy (UPS). The results of LEIS clearly reveal the complete surface segregation of Pt to the top layer on all crystal alloys. LEED indicates the (5 × 1) surface reconstruction on the Pt₃Ni(100), while (110) and (111) surfaces show (2 × 1) and (1 × 1) patterns, respectively, identical to Pt single crystals. The valence bands density of states on Pt₃Ni alloys are compared to those of Pt single crystals via UPS measurements.