A study of the chemisorption of phenol and its derivatives on plasma-grown aluminium oxide by inelastic electron tunneling spectroscopy

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Abstract
Inelastic electron tunneling spectroscopy has been applied to study the adsorption of a series of phenols on plasma‐grown aluminium oxide. Vapor phase doping was used and spectra recorded for o‐, m‐, p‐chlorophenol, p‐fluorophenol, p‐bromophenol, o‐, m‐, p‐cresol, and phenol. The high resolution spectra obtained at 2 K allow most of the possible modes to be identifield. The relative strengths of these modes are compared in terms of the proposed molecular orientation of the absorbates in an effort to observe the predicted directional sensitivity of the tunneling process. No systematic line intensity variation is evident, and it is postulated that for large molecules this may be because of the complexity of the motions involved in the vibrational modes. It is also suggested that the contouring of the lead electrode round the adsorbate has the important effect of obscuring the directional sensitivity of the tunneling process. An attempt has also been made further to characterize the chemical nature of the oxide and its surface.