In situ ellipsometric study of optical properties of ultrathin films.

A method has been developed for analysis of a series of ellipsometric data taken in situ during deposition. With this method the optical constants n and k and thickness d of growing ion-beam-sputtered films of C, Si, Ni, Nb, Mo, Ru, Rh, Pd, Ag, W, Re, and Au have been determined as a function of deposition time t. The minimum critical thickness d(i) needed for a film to become optically isotropic has been determined from the n, k, d-versus-t curves. Anomalous behavior of these curves appears in the region d less, similar d(c) resulting from a breakdown of the isotropic film model employed. This is shown, by transmission electron micrographs, to have a correlation with a transition region from island/anisotropic to continuous/isotropic.