Atomic layer deposition of Al2O3 and TiO2 multilayers for applications as bandpass filters and antireflection coatings

Al2O3 and TiO2 thin films have been deposited on Si wafers, quartz, BK7 glass, and polycarbonate substrates by atomic layer deposition (ALD). The refractive indices and growth rates of the materials have been determined by spectroscopic ellipsometry and transmission electron microscopy. The influence of substrate temperature and precursor on the refractive indices has been investigated. The refractive index of TiO2 significantly increases with temperature, whereas the Al2O3 films are temperature insensitive. The films deposited using H2O2 as oxygen source show a slightly higher refractive index than the films prepared with H2O. Multilayer narrow-bandpass filters and broadband antireflective coatings have been designed and produced by ALD. (C) 2009 Optical Society of America