Vacuum-metal interface field

Model 2a.3 Vacuum-Metal Interface with Applied Electric Field... 

The real parts of k-z and kkz tell us how far the electric and magnetic fields penetrate into the metal (a) and vacuum (b), respectively. Figure 5 shows the distance in which these fields fall to 1/e of their value at the surface for a vacuum-copper interface. The fields extend a much greater distance into the vacuum than they do into the metal. 

Chapter 3, by Rolando Guidelli, deals with another aspect of major fundamental interest, the process of electrosorption at electrodes, a topic central to electrochemical surface science Electrosorption Valency and Partial Charge Transfer. Thermodynamic examination of electrochemical adsorption of anions and atomic species, e.g. as in underpotential deposition of H and metal adatoms at noble metals, enables details of the state of polarity of electrosorbed species at metal interfaces to be deduced. The bases and results of studies in this field are treated in depth in this chapter and important relations to surface -potential changes at metals, studied in the gas-phase under high-vacuum conditions, will be recognized. Results obtained in this field of research have significant relevance to behavior of species involved in electrocatalysis, e.g. in fuel-cells, as treated in chapter 4, and in electrodeposition of metals. 

Epitaxial growth under clean conditions in ultra high vacuum is increasingly used in the field of metal physics as a way of preparing new materials in form of thin films or superlattices. Because of interdiffusion at the metal-metal interface, the control of the structural properties is at least as difficult as in the case of semiconductor-metal interfaces. Some initial, but very interesting steps have, however, recently been reported, also with epitaxial lanthanides. Faldt and Myers (1985) have prepared and... 

In electrochemical media the metal electrode is not in contact with the vacuum, as shown above, but with an electrolyte that could drastically modify the potential field near the interface. 

One of the important variables in the electrochemical system is the electrode potential. By controlling the electrode potential, very high electric fields, up to the order of 107 V/cm, can be applied to an adsorbed molecule or ion, which is not as easily accomplished for metal-vacuum or metal-gas interfaces. The first observation of field dependent shift of the vibrational band was reported in 1981 by SERS... 

Surface electromagnetic waves (SEW) on a metal-vacuum interface (often called surface plasmons) are discussed to demonstrate the essential features of SEW. SEW are surface waves in the sense that the electric and magnetic fields decay exponentially as one moves away from the surface, either into the metal or into the vacuum. Figure 1 shows the coordinate system we shall use. The metal-vacuum interface is the z = 0 plane, and the metal occupies the z < 0 half-space. The direction of propagation is the positive x-directi on. The metal has a... 

One simple explanation for these results was as follows The electric field at a metal vacuum interface can be >10 times larger than in free space when the conditions required for a surface plasma resonance are met (47). Since the Raman cross-section is proportional to the square of the field, surface plasmons could produce enhancements of >10. This enhancement is probably not large enough to explain the tunneling junction results by itself, but an enhancement in signal of a factor of 100 by the excitation of surface plasmons would increase the Raman intensity from near the limits of detectibility. 

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