Surface-State-Mediated Interactions

Surface-State Mediated Interactions Between Adatoms. 23... 

Fig. 2. (a) For Cu/Cu(lll) the surface state mediated long-range interactions favor... 

In another interesting development, Gumhalter and Brenig (1995a,b) proposed that, in H-Ni(llO) and H-Cu(llO) systems, adatom-induced reconstruction of the surface gives rise to quasi-one-dimensional surface states, which mediate the indirect interaction. The greatly reduced dimensionality... 

The 2D electron gas of the Shockley-type surface states plays also an important role in the substrate mediated interaction between adsorbed atoms. 

The example of Ce/Ag demonstrates that the surface state electron mediated adsorbate-adsorbate interactions may well be employed for the creation of ordered atomic and possibly also molecular superlattices. In principle the lattice constant can be adjusted by the surface state band structure. 

In this section, we first consider a general model of the faradaic processes occurring at the semiconductor-electrolyte interface due to Gerischer [11]. From Gerischer s model, using the potential distribution at the interface, we may derive a Tafel-type description of the variation of electron transfer with potential and we will then consider the transport limitations discussed above. We then turn to the case of intermediate interactions, in which the electron transfer process is mediated by surface states on the semiconductor and, finally, we consider situations in which the simple Gerischer model breaks down. 

Outer-sphere redox mediators (see Fig. 3.23 for examples) are termed surface insensitive such that kf is not influenced by the surface oxygen-carbon ratio, surface state/cleanliness in terms of a surface coating of a monolayer film of uncharged adsorbates, or specific adsorption to surface groups/sites [1]. There is no chemical interaction or catalytic mechanism involving interaction (i.e. an adsorption step)... 

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