Surface electron structure

The surface work fiincdon is fonnally defined as the minimum energy needed m order to remove an electron from a solid. It is often described as being the difference in energy between the Fenni level and the vacuum level of a solid. The work ftmction is a sensitive measure of the surface electronic structure, and can be measured in a number of ways, as described in section B 1.26.4. Many processes, such as catalytic surface reactions or resonant charge transfer between ions and surfaces, are critically dependent on the work ftmction. 

A DIET process involves tliree steps (1) an initial electronic excitation, (2) an electronic rearrangement to fonn a repulsive state and (3) emission of a particle from the surface. The first step can be a direct excitation to an antibondmg state, but more frequently it is simply the removal of a bound electron. In the second step, the surface electronic structure rearranges itself to fonn a repulsive state. This rearrangement could be, for example, the decay of a valence band electron to fill a hole created in step (1). The repulsive state must have a sufficiently long lifetime that the products can desorb from the surface before the state decays. Finally, during the emission step, the particle can interact with the surface in ways that perturb its trajectory. 

Flamers R J, Tromp R M and Demuth J M 1986 Surface electronic structure of Si(111)-7 7 resolved in real space Phys. Rev. Lett. 56 1972... 

Krasovskll E E and Schattke W 1997 Surface electronic structure with the linear methods of band theory Phys. Rev. B 56 12 874... 

Inglesfield J E and Benesh G A 1988 Surface electronic structure embedded self-consistent calculations Phys. Rev. 

Aers G C and Inglesfield J E 1989 Electric field and Ag(OOI) surface electronic structure Surf. Sc/. 217 367 Colbourn E A and Inglesfield J E 1991 Effective charges and surface stability of O on Cu(OOI) Phys. Rev. Lett. 66 2006... 

Single slab. A number of recent calculations of surface electronic structures have shown that the essential electronic and structural features of the bulk material are recovered only a few atomic layers beneath a metal surface. Thus, it is possible to model a surface by a single slab consisting of 5-15 atomic layers with two-dimensional translational symmetry parallel to the surface and vacuum above and below the slab. Using the two-dimensional periodicity of the slab (or thin film), a band-structure approach with two-dimensional periodic boundary conditions can be applied to the surface electronic structure. 

Ruhan A, Hammer B, Stoltze P, Skriver HE, Nprskov JK. 1997. Surface electronic structure and reactivity of transition and noble metals. J Mol Catal A Chem 115 421. 

Stamenkovic V, Mun BS, Mayrhofer KJJ, Ross PN, Markovic NM, Rossmeisl J, Greeley J, Nprskov JK. 2006. Changing the activity of electrocatalysts for oxygen reduction by tuning the surface electronic structure. Angew Chem Int Ed 45 2897. 

Recent studies using high resolution electron energy loss and photoelectron spectroscopy to investigate the effect of sulfur on the CO/Ni(100) system are consistent with an extended effect by the impurity on the adsorption and bonding of CO. Sulfur levels of a few percent of the surface nickel atom concentration were found sufficient to significantly alter the surface electronic structure as well as the CO bond strength. 

The combined use of the modem tools of surface science should allow one to understand many fundamental questions in catalysis, at least for metals. These tools afford the experimentalist with an abundance of information on surface structure, surface composition, surface electronic structure, reaction mechanism, and reaction rate parameters for elementary steps. In combination they yield direct information on the effects of surface structure and composition on heterogeneous reactivity or, more accurately, surface reactivity. Consequently, the origin of well-known effects in catalysis such as structure sensitivity, selective poisoning, ligand and ensemble effects in alloy catalysis, catalytic promotion, chemical specificity, volcano effects, to name just a few, should be subject to study via surface science. In addition, mechanistic and kinetic studies can yield information helpful in unraveling results obtained in flow reactors under greatly different operating conditions. 

Pi TW, Liu Ch, Hwang J (2006) Surface electronic structure of Ca-deposited tris (8-hydroxyquinolato) aluminum studied by synchrotron radiation photoemission. J Appl Phys 99 123712... 

The actual achievement of STM greatly exceeds this expectation. Details of surface electronic structures with a spatial resolution of 2 A are now routinely observed. Based on the obtained electronic structure, the atomic structures of surfaces and adsorbates of a large number of systems are revealed. Furthermore, the active role of the STM tip through the tip-sample interactions enables real-space manipulation and control of individual atoms. An era of experimenting and working on an atomic scale arises. 

The simplest model of a metal surface is the jellium model, which is a Sommerfeld metal with an abrupt boundary. In provides a useful semiquanti-tative description of the work function and the surface potential (Bardeen, 1936). It validates the independent-electron picture of surface electronic structure Essentially all the quantum mechanical many-body effects can be represented by the classical image force, which has been discussed briefly in Section... 

The jellium model for the surface electronic structure of free-electron metals was introduced by Bardeen (1936) for a treatment of the surface potential. In the jellium model, the lattice of positively charged cores is replaced by a uniform positive charge background, which drops abruptly to zero at the... 

If available, the LDOS at different energy levels, for the tip and the sample, is very useful information for predicting STM images. Several examples of surface electronic structures from first-principles calculations are reproduced as illustrations. 

On perfect crystalline surfaces, the unperturbed electronic structure is determined by the energy band structure of the surface Bloch waves. This is a consequence of the two-dimensional translational symmetry of the surface. The presence of the tip breaks the translational symmetry of the surface, and the surface electronic structure of the sample is perturbed. 

Inglefield, J. E. (1982). Surface electronic structure. Rep. Prog. Phys. 45, 223-284. 

See Scanning tunneling spectroscopy Superconductors 332—334 Surface Brillouin zone 92 hexagonal lattice 133 one-dimensional lattice 123, 128 square lattice 129 Surface chemistry 334—338 hydrogen on silicon 336 oxygen on silicon 334 Surface electronic structures 117 Surface energy 96 Surface potential 93 Surface resonance 91 Surface states 91, 98—107 concept 98... 

According to the presented model of oxides formation on Au, the outer surface of the thick oxide film exposed to the solution is either AU2O3 or Au(OH)3. The type of oxide determines the surface electronic structure and electrocatalytic properties. Electrocatalytic properties of gold oxide-covered electrodes have been discussed by Burke and Nugent [366, 368]. 

The wide range of different PL spectra obtained shows just how much the various films vary from each other and the sensitivity of the (mainly surface) electronic structure of the CdS to the deposition parameters. 

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