OPTICAL EXAMINATION AND MONITORING OF SURFACES

Surfaces are of considerable importance to a range of material based industries and in recent years many techniques have been developed for surface examination. The paper gives an introduction to the application of optical techniques for the examination and monitoring of surfaces. Ellipsometry has played a significant role in such applications to date and the major proportion of the article is devoted to the technique. The reflection of plane polarised light at film free surfaces subsequently covered by non-absorbing and absorbing films is considered. There is a brief description of the basic instrument and component alignment. The problems associated with the characterisation of clean surfaces prior to corrosion or adsorption studies are discussed. A number of applications are given including the growth of oxide and corrosion layers on surfaces in vacuo and other environments, the adsorption of gases on surfaces, the effects of roughness, ion bombardment, ion implantation and anisotropy on the optical constants of surface layers, and the increasing use of optical techniques in the life sciences. Attention is drawn to variations in surface properties produced by cleaning processes and surface treatments. Optical methods can also provide useful information when employed in conjuction with other techniques such as ESCA (XPS), LEED, FEM electron microscopy and Auger electron microscopy and many references are given to such works. References to more recent results obtained with optical reflectance spectroscopy to elucidate surface electronic structure are included. A variety of automatic instruments some of which can be used to monitor rapid film growth on surfaces have been reported in the literature and the paper contains a representative selection of references to different instrument types. In all there are over 200 references (many of which are in themselves review articles of specialised applications) to illustrate the range of applications of optical methods in the examinations of surfaces. © 1979.