2013 Volume 54 Issue 6 Pages 1025-1028
Anti-reflection coating, which exhibits higher transmittance than that of glass substrate itself, has been obtained by hydrothermal treatment of Al film in ultrapure water and hydrothermally-treated Al film was consisted of transparent boehmite (aluminum oxyhydroxide) (J. Appl. Phys. 106 (2009) 023524). However the stability of the hydrothermally-treated film is not enough, as boehmite contains water in its crystal structure. In this study, we examined the heat-treatment of such boehmite film. According to transmission electron microscopy and transmission Fourier-transform infrared spectroscopy, dehydration was observed at above 673 K for 1 h and boehmite transformed to a stable phase of γ-alumina. Though the structural change took place, the optical property of high transmittance remained and/or even improved.