Studies of the optical and structural properties of ion-assisted deposited Al2O3 thin films

Abstract

The optical and structural properties of Al 2 O 3 films produced by oxygen-ion assisted deposition (IAD) have been investigated as a function of ion energy (300–1000 eV), ion current density (50–220 μA cm −2), and substrate temperature (ambient-300°C). It is observed that films prepared by IAD with the substrates maintained at elevated temperatures show the best properties. The maximum refractive index obtained was 1.73 for films deposited at 1000 eV, 50 μA cm −2 and 300°C. Teh refractive index decreased with the increase in ion current density for ion energies exceeding 300 eV with absorption still being negligible. As-deposited films prepared, with or without ion bombardment, were amorphous. Films deposited without ions and annealed at 800°C in air for 12 h were σ- alumina, whereas those deposited at 1000 eV ion energy, 220 μA cm −2 ion current density and annealed at the same temperature for the same period were found to be α- alumina.