Study of gradual conversion of Al to insulator by oxygen implantation

Abstract

30 keV O₂ ⁺ ions are implanted in aluminium foil, at various doses ranging from 5 × 10¹⁶ to 5 × 10¹⁷ atoms cm⁻². The sheet resistance was measured for unimplanted and implanted specimens. Up to the dose of 3 × 10¹⁷ atoms the sheet resistance graduallg layer on the surface, above a dose of 3 × 10¹⁷ atoms cm⁻². X-ray photo-electron spectroscopy measurements indicated the formation of an Al₂O₃ layer with the absence of a signal due to unbonded aluminium for a dose of 5 × 10¹⁷ atoms cm⁻². Whereas a specimen implanted at 5 × 10¹⁶ atoms cm⁻² shows the presence of pure aluminium. Micrograph of the specimen implanted at the higher dose displayed the microtopography characteristic of alumina. Our results are in agreement with a recently published mechanism of Al₂O₃ formation. The Al₂O₃ precipitates increasing with dose and a layer of Al₂O₃ being formed at the doses higher than that required to form the stoichiometric Al₂O₃.