Vacuum-metal interface

That the intrinsic surface potential at the vacuum/metal interface... 

Model 2a.2 Vacuum-Metal Interface with Dipole Moment Correction... 

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

Ishii H, Seki K (1997) Energy level alignment at organic/metal interfaces studied by UV photoemission breakdown of traditional assumption of a common vacuum level at the interface. Trans Electron Devices 44 1295-1301... 

Modeling the Aqueous—Metal Interface in Ultrahigh Vacuum via Cryogenic Coadsorption... 

WAGNER AND MOYLAN Aqueous—Metal Interface in UUrahigh Vacuum... 

WAGNER AND MOYLAN Aqueous-Metal Interface in Ultrahigh Vacuum... 

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. 

It has now been demonstrated that many molecules adsorbed on appropriately prepared metal surfaces display Raman cross-sections several orders of magnitude greater than the corresponding quantity for an isolated molecule or from a solution. Together with other surface-sensitive techniques, SERS has catalyzed the study of condensed phases on surfaces. It has demonstrated promise as a vibrational probe of in situ gas-solid, liquid-solid, and solid-solid environments, as well as a high-resolution probe of vacuum-solid interfaces. 

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. 

This mcclianism is not so efrcctivc in polar semiconductors. The conversion of empty hybrids to doubly occupied hybrids on a GaAs surface would require the double occupation of a gallium hybrid, which is unfavorable because of the polar energy. Indeed, recent experiments (Chye, Babalola, Sukegawa, and Spicer, 1975) indicate that the I crmi level is not pinned on surfaces of GaP at the vacuum. Nonetheless, Schottky barriers can arise at GaP- metal interfaces. Metal-induced surface states" have been proposed as a mechanism (discussed in Section 18-1 ) but the barriers could well arise simply from incorporation of metal atoms in the semiconductor or vice versa. 

In the literatme, the work function of a metal, p (in eV), is often used to estimate the degree of charge transfer at semiconductor/metal junctions. The work function of a metal is defined as the minimum potential experienced by an electron as it is removed from the metal into a vacuum. The work function ip is often nsed in lieu of the electrochemical potential of a metal, because the electrochemical potential of a metal is difficult to determine experimentally, whereas tp is readily accessible from vacuum photoemission data. Additionally, the original model of semiconductor/metal contacts, advanced by Schottky, utilized differences in work functions, as opposed to differences in electrochemical potentials, to describe the electrical properties of semiconductor/metal interfaces. A more positive work function for a metal (or more rigorously, a more positive Fermi level for a metal) would therefore be expected to produce a greater amount of charge transfer for an n-type semiconductor/metal contact. Therefore, use of metals with a range of tp (or fip.m) values should, in principle, allow control over the electrical properties of semiconductor/metal contacts. 

The development of infrared reflection-absorption spectroscopy to study gas-phase/solid interface started as a necessary step to avoid the practical limitations imposed by the use of oxide-supported metals [20]. This improvement opened the possibility of studying adsorbed species on well-defined metal surfaces, from which a considerable knowledge of the vibrational properties at the gas-phase/metal interface has been gained [21]. This information from ultrahigh vacuum (UHV) systems provides the basis for the application of the infrared technique to studying the (more complex) electrochemical interface. 

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