The well known 'crystal seed' theory is first applied in this work to prepare TiO 2 film: a high refractive index rutile TiO 2 film is grown by electron beam evaporation on the rutile seed formed by 1100uC annealing. The average n is larger than 2?4, by far the highest in all the authors' TiO 2 films. The films are characterised by optical properties, microstructure and surface morphologies. It is found that the refractive index shows positive relation with the crystal structure, grain size, and packing density and roughness of the film. The film has lower density of granularity and nodule defects on the surface than those of the film deposited by magnetron sputtering. The result shows attractive application in complex filter and laser coatings.

The thermal stability of electron beam deposited TiO 2 monolayers and TiO 2 /SiO 2 high reflectors (HR) during 300 to 1100uC annealing is studied. It is found that the optical loss of film increases with the increase in annealing temperature, due to the phase change, crystallisation and deoxidising of film. Scattering loss dominates the optical property degradation of film below 900uC, while the absorption is another factor at 1100uC. The increase in refractive index and decrease in physical thickness of TiO 2 layer shift the spectra of HR above 900uC. The possible crack mechanism on the surface of HR during annealing is discussed. Guidance for application on high temperature stable optical coatings is given.