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 (E ELS). The reduction behavior of alumina films with different thicknesses, 3 , 6, 9, and 80 nm was observed under electron-beam irradiation in the energ y range from 0.5 to 10 keV at various temperatures from 300 to 670 K. It wa s determined that the reduction rate was higher for thinner alumina film an d at higher surface temperatures. Alumina was not completely reduced to met allic 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 init ial value. This reduced value did not depend on the thickness of alumina fi lm, beam energy or sample temperature below 535 K. At temperatures higher t han 550 K, reduced Al disappeared from the surface, possibly by dissolving into the Cu bulk.