Spectroscopy IETS

In contrast to the minimal activity in infrared reflection studies the technique of inelastic electron tunneling spectroscopy (IETS) recently has contributed a large amount of information on monolayer adsorption of organic molecules on smooth metal oxide surfaces,Q),aluminum oxide layers on evaporated aluminum. These results indicate that a variety of organic molecules with acidic hydrogens, such as carboxylic acids and phenols chemisorb on aluminum Oxide overlayers by proton dissociation - 1 — and that monolayer coverage can be attained quite repro-ducibly by solution doping techniques. - The IETS technique is sensitive to both infrared and Raman modes. — However, almost no examples exist in which Raman il and or infrared spectra have been taken for an adsorbate/substrate system for which IETS spectra have been observed. 

In other studies Allara (27) used FTIR reflection to study the interaction of the oxide film of aluminum with acetic acid in which th aluminum acetate carbonyl stretch peak was found at 1590 cm- > in excellent agreement with the 1589 cm-1 peak determined by inelastic electron tunnelling spectroscopy (IETS), another modern technique for vibrational spectra at metal interfaces. The spectra of acetic acid adsorbed on copper oxide or indium,oxide were about the same. 

In parallel, the related activity was in the field of single-electron shuttles and quantum shuttles [143-153]. Finally, based on the Bardeen s tunneling Hamiltonian method [154-158] and Tersoff-Hamann approach [159,160], the theory of inelastic electron tunneling spectroscopy (IETS) was developed [113-116,161-163],... 

One technique recently applied to UE [129,130] is inelastic electron tunneling spectroscopy (IETS) (Section 11.11). The IETS spectrum (dIz/dVz) measured at 4.2 K for a monolayer of fullerene-fczs-[12a.ethylthio-tetrakis(3,4-dibutyl-2-thiophene-5-ethenyl)-5-bromo-3,4-dibu-tyl-2-thiophene] malo-nate, 47, between Al and Pb electrodes [130] exhibited (i) the usual IETS spectrum of intramolecular vibrations and (ii) an elastic component, measured at slightly higher bias V, due to "orbital-mediated tunneling," that is, an... 

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