Phase size effect in thin Ge-Se polycrystalline films

The Raman spectra of thin (d = 60–170 nm) Ge-Se polycrystalline films obtained by vacuum thermal evaporation of Ge10Se90 glass are investigated in the spectral range 110–310 cm−1. The coexistence of the glasslike and crystalline phases α-Se, β-Se, and β-GeSe2 is established using the X-ray diffraction method. Analysis of diffraction patterns and the Raman spectra of polycrystalline samples of various thicknesses demonstrates a phase size effect in the transition of Se from the α-monoclinic to the β monoclinic modification (d ∼ 120 nm). It is found that the crystalline phase of Se is of the nanodisperse type with an average grain size of ∼30–50 nm. Crystallites of β-GeSe2 have an average size of ∼100–130 nm.