Determination of optical constants: Disordered germanium

The transition from the amorphous to the crystalline state has been studied by ellipsometric determination of the room‐temperature optical constants on evaporated germanium films and single crystals in the spectral range from 2.0 to 4.0 eV. For evaporated samples the substrate temperature varied over the range 20 °C ≦ T s ≦ 400 °C. For T s ≦ 200 °C no any fine structure but an increase of ϵ 2 (ω) with decreasing disorder has been found. For T s > 200 °C characteristic structures occurred at energies comparable with critical points of the crystalline state. The absolute value and the line shape of ϵ(ω) however are different for single crystals and films.