Optical properties of small In particles in thin-film form

Reflectance studies in the 1.0- to 0.2-{μ}m region have been made on thin In films which exhibit a discontinuous islandlike structure. Phase-shift measurements demonstrate that the optical properties of these films are dominated by interference effects. Two features are of particular interest. Firstly, when the films are placed above a highly reflecting substrate, strong coloration indicative of a reflective interference filter is observed. Secondly, it is found that In films are very sensitive indicators of thin transparent layers. In fact, layers as thin as 50 {} are easily observed when applied as overcoats on In films. Both of these aspects are discussed in terms of the optical response of the small particles composing the film.