The optical systems surfaces share some features such as lateral uniformity, smoothness and well determined layers suitable for using of Rutherford backscattering method (RBS). RBS is nondestructive and its principle is very simple: the energy of scattered particles from originally monoenergetic beam depends on target atoms mass and their position under the surface. A modern PC procedure for RBS data evaluation GISA3.99 has been used accounting many theoretical details. The evaluated parameters are composition stoichiometry, layers thickness, impurity contents and/or depth profiles. Examples of measured systems are those with varying refractive index, modified surfaces, implanted systems, photoinduced Ag diffusion, ferroelectric ceramics, magneto-optic recording media, hard and protection coatings, luminescent silicium, laser mirrors systems and medieval glass weathering. An example of evaluation procedure of unknown six layer system is shown. The investigated systems are prepared by various methods: conventional and reactive evaporation, rf and dc magnetron sputtering, laser ablation, ion beam assisted deposition, plasma jet and sol-gel technique. There are some limitations of RBS method with surface roughness and with precise knowledge of cross-section and stopping powers. In spectra of complex structures, there may also be interference of signals from various elements and from various layers. Nevertheless, the RBS technique has a number of unique features and it is in many cases irreplaceable.
Developments in Optical Component Coatings
- Pub Date:
- August 1996