Spectrophotometry, ellipsometry and computer simulation in thin film developments.

Thin film deposition techniques are widely used in industry because of the variety of practical applications where they may be appropriate. The manufacture of thin film coatings normally requires high vacuum equipment, with additional attachments such as electron beam evaporators, ion guns, quartz oscillator microbalance, etc. Besides the technological problems involved in the deposition of the films, the optical characterization of the coatings obtained is a major issue. For example, for wideband antireflection coating of lenses a precise control of the refractive indices and thicknesses obtained is required, together with a good uniformity inside the whole vacuum chamber. Thus, techniques for the measurement of refractive indices and thicknesses of thin films have to be available in laboratories related to the deposition plants. Several characterization apparatus are quite standard in industry, because their wide range of applications and relative low cost (spectrophotometer is the typical example). Other apparatus are much more specific and much more expensive like ellipsometers, secondary ion mass spectrometers (SIMS), transmission electron microscopes (TEM)..., although monochromatic ellipsometers may sometimes be accessible because of its moderate cost. Finally, very powerful desk computers are really cheap nowadays, so computation facilities are always available at any laboratory. The aim of the present work is to illustrate the combined use of three basic laboratory techniques -spectrophotometry, monochromatic ellipsometry and computer simulation- in the development of thin film coatings and filters.