Complex refractive indices of GeSbTe-alloy thin films: Effect of nitrogen doping and wavelength dependence

The effects of nitrogen doping on the complex refractive indices of Ge2Sb2Te5 phase-change optical recording materials and their wavelength dependence were examined. With an increase in nitrogen concentration, the extinction coefficients decreased monotonically. The calculated reflectance spectra at normal incidence showed a good quantitative agreement with the measured values. The observed optical properties were correlated with the characteristic features of the microstructure, including grain size refinement, internal residual stresses, and changes in the bonding state.