Optical properties and phase change transition in Ge2Sb2Te5 flash evaporated thin films studied by temperature dependent spectroscopic ellipsometry

摘要: We studied the optical properties of as-prepared (amorphous) and thermally crystallized (fcc) flash evaporated Ge2Sb2Te5 thin films using variable angle spectroscopic ellipsometry in photon energy range 0.54–4.13 eV. employed Tauc–Lorentz (TL) model Cody–Lorentz (CL) for amorphous phase TL with one additional Gaussian oscillator fcc data analysis. The has bandgap Egopt=0.65 eV or 0.63 eV slightly dependent on used model. Urbach edge film was found to be ∼70 meV. Both models behave very similarly accurately fit experimental at energies above 1 CL is more accurate describing dielectric function absorption onset region. thickness decreases ∼7% toward phase. significantly lower than phase, Egopt=0.53 eV. temperature revealed crystallization 130–150 °C. amorph...