Electrical properties and stability of an epitaxial alumina film formed on Cu-9 at. % Al(111)

Abstract

An ultrathin epitaxial alumina film formed in ultrahigh vacuum on a Cu-9 at. %Al(111) single crystal was characterized by in situ low energy electron diffraction and reflection high energy electron diffraction methods and by ex situ x-ray diffraction and conducting atomic force microscopy (AFM) techniques. Ex situ measurement results on the crystal structure and surface morphology were compared with the in situ results. It was confirmed that the 1.6 nm-thick epitaxial film maintained its crystal structure and atomically flat terrace surface morphology after several months of air exposure. Current–voltage (I–V) measurements on the alumina film were performed using conducting AFM. No electrical breakdown occurred even when an electric field as strong as 2.5 × 109 V/m was applied. The band gap of the alumina film and the band alignment between the film and the substrate were determined from I–V curves.