Reduction and removal of thin Al oxide film from Cu substrate by focused electron beam

The electron-stimulated reduction of alumina deposited on Cu was studied by Auger electron spectroscopy (AES) and electron-energy-loss-spectroscopy (EELS). The reduction behavior of alumina films with different thicknesses, 3, 6, 9, and 80 nm was observed under electron-beam irradiation in the energy range from 0.5 to 10 keV at various temperatures from 300 to 670 K. It was determined that the reduction rate was higher for thinner alumina film and at higher surface temperatures. Alumina was not completely reduced to metallic aluminum even after a long electron irradiation and reached a steady state in which Al3+ and Al-0 coexisted. Until this steady state was reached, the oxygen concentration decreased monotonically to about 55% of the initial value. This reduced value did not depend on the thickness of alumina film, beam energy or sample temperature below 535 K. At temperatures higher than 550 K, reduced Al disappeared from the surface, possibly by dissolving into the Cu bulk.