M. Nowicki

Directional Auger and directional elastic peak electron spectroscopies: experimental and theoretical approach

Abstract The incident electron beam effects for energies 0.5–2xa0keV, measured by Auger and elastically backscattered electrons, were investigated experimentally and theoretically for the (0xa00xa01), (1xa01xa01), and (1xa01xa00) Cu crystals. The Auger signal and the height of the elastic peak were measured as a function of the incident angle of the primary beam with the use of an retarding field analyser (RFA). Very well distinguished intensity maxima were found for incident angles corresponding to the closely packed rows of atoms. The experimental results correspond to the theoretical data where single scattering cluster (SSC) approximation was used. The damping of Auger and elastically backscattered electrons in the sample caused the inclination of the profiles towards the grazing angles. The best correspondence between theory and experiment was found for the primary beam energies in the range 1.0–1.3xa0keV.

Properties of ultrathin silver layers deposited on the Cu(001) face

Abstract This work is a continuation of investigations of the Ag Cu (111) and the Ag Cu (011) adsorption systems. The investigations of the Ag Cu (001) interface were performed with AES, LEED, Directional Auger Electron Spectroscopy (DAES) and Directional Elastic Peak Electron Spectroscopy (DEPES). During silver evaporation at the substrate temperature from 300 K up to 440 K the Ag MNN (360eV) and Cu M 2,3 VV (62eV) Auger peak kinetics indicate the Stranski-Krastanov growth mechanism. For T = 540 and 700 K the adsorption kinetics show that after 1 ML layer deposition Auger signals from silver h Ag and copper h Cu remain unchanged due to the silver dissolution in the Cu substrate. For T = 820 K a silver dissolution is so fast that coverage of 1 ML was not reached. During annealing of the 2.2 ML of Ag at T = 790 K and 820 K the equilibrium coverage of 1 ML layer is observed, which was predicted by theoretically calculated dissolution isotherms. DEPES profiles for the Cu(001) face clean and covered with 8 ML layers of Ag indicate that the silver layer is composed of (111) islands with three orientations: [112(111)Ag∥ [110](001)Cu, [112](111)Ag∥ [110](001)Cu, and [211](111)Ag ∥ [110](001)Cu.

The influence of substrate crystalline structure on DAES profiles of ultrathin silver layers on a Cu(001) face

Abstract The influence of the substrate crystalline structure on DAES profiles for ultrathin silver (111) layers deposited on a Cu(001) substrate was investigated. For Ag MNN Auger electrons and for primary electron energies E P ≥ 800 eV, the DEAS profiles characteristic of the substrate structure were observed for a 0.8 ML silver layer, while for E P = 600 eV such a profile was flat. On the other hand, DAES profiles characteristic of the silver layer structure were observed for thicker silver films, for E P ≥ 600 eV. This can be explained if one takes into account that the Auger electrons are excited in the silver layer by primary electrons and by electrons backscattered in the substrate. The flux of the Auger electrons is determined by the forward focusing and channelling of primary electrons in the substrate. For E P = 600 eV the backscattering factor is close to unity and only the primary electrons are responsible for the Auger electron emission from the overlayer. Thus, as low as possible energies E P should be used to eliminate the influence of the substrate crystalline structure on the DAES profiles of ultrathin adsorbed layers.

Porphyrin Layers at Cu/Au(111)–Electrolyte Interfaces: In Situ EC-STM Study

The coadsorption of porphyrin molecules (TMPyP: tetra(N-methyl-4-pyridyl)-porphyrin), sulfate anions and copper on a Au(111) electrode was investigated by the use of cyclic voltammetry (CV) and in situ electrochemical scanning tunneling microscopy. With decreasing electrode potential the following sequence of surface phases was found: (I) an ordered

Growth and crystalline structure of Co layers on Cu(0 0 1)

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Identification of the monolayer oxygen structure on Ru(101¯0) by means of directional elastic peak electron spectroscopy (DEPES)

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Crystalline structure of the Au(111) surface revealed by stereographic intensity DEPES maps

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