Evidence for the formation of Al-H bonds in tunneling junctions

Abstract

This paper is devoted to the study of aluminum-oxide-metal tunneling junctions where the oxide has been grown on aluminum by glow discharge in water vapor. The inelastic electron tunneling spectra obtained from these samples have been investigated and new assignments of the observed bands are proposed. In particular, evidence for the presence of $\mathrm{A}1{\mathrm{H}}_{x}$ species in the junction is presented. The bands observed at 605, 726, and 1855 ${\mathrm{cm}}^{\ensuremath{-}1}$ are ascribed to two bending modes and a stretching mode of the Al-H bond. Moreover, the behavior of the band intensities with respect to the bias polarity applied during the tracing of the spectra clearly shows that these species are located near the aluminum-oxide interface of the junctions. Mechanisms for the formation of the $\mathrm{A}1{\mathrm{H}}_{x}$ species are discussed. Finally, the consequences of these results which could be useful for inelastic electron tunneling spectroscopy are emphasized.