<title>Optical properties of titania films prepared by ion-assisted deposition</title>

Abstract

Thin filiris of titaniwn dioxide have been deporited using ion assisted deposition with oxygen ions produced using (1) a Heitinann ion source (HIS) for ions of energy less than 100 eV and (2) a broad beam Kaufman ion source (KIS) for ions in the2 energy range 100 to 500 eV and current densities up to 100 pA,"cm . It.has been observed that. the refractive index of the fi1m increases up to 300 eV and the extinction coefficient only nominally up to 300 eV. The maximum refrac:4ve index obtained was 2.49 at energy of 300 eV and 50 NA/cm current. density. The refractive index of the filuis deposited using the HIS was lower than those deposited using the KIS. The refractive index of the HIS films increased with increasing substrate temperature with very little charge in the extinction coefficient. 1L INTRODUCTIOIL Titanium dioxide has found application in inanytechnologically important fields due to its high hardness, durability, refractive index and low absorption etc.Consequently there has been considerable interest in its properties in thin film form. It, however, has a number of sub oxide forms which makes it difficult to deposit stoichiometric films1.Inspite of such problems good and high quality titanzia films have been deposited using sputtering, RF and DC, reacie evaporation, Activated reactive evaporation, ion plating etc These techni'jues however, require the optimisation of numerous deposition parameters such as pressure, rate of deposition, substrate temperature , power , RF or DC etc . to obtain high quality films reproducibly, limiting the use of these techniques. loni assisted deposition(IAD) is one process which has transformed this situation by the flexibility of ion source parameters, making it possible to coat films wit.h bulk like properties. Vapour deposited films have been found to have a columnar12 1icrostructure resulting from a low adatom mobility ' . This causes a decrease in packing density arid concomitant problems I ike water vapour adsorption on exposure to 192 / SPIE Vol. 1624 Laser-Induced Damage in Optical Materials: 1991 0-81 94-0766-6192/$4.00 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/20/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx