Study of the optical properties of anthracene thin films by ellipsometry

By employing the least-squares technique to fit the experimental ellipsometric data and an alogorithm to yield values of refractive index and film thickness, we have determined the optical constants of biaxially anisotropic anthracene thin films deposited on glass substrates as functions of film thickness in the visible-frequency region. The results show that the optical constants are markedly dependent on film thickness for ratios of film thickness to wavelength smaller than 10. We attribute this to the effect of surface states on excitons, which is more serious for thin films than for thick films.