Effect of nitrogen doping on structural and optical properties of Ge_2Sb_2Te_5 recording layer

摘要

Ge_2Sb_2Te_5 is a promising candidate for a recording material of phase change optical disk and nitrogen is doped into this film to increase overwrite characteristics. In this study, the effect of nitrogen doping in Ge_2Sb_2Te_5-(N) recording layer is quantitatively examined by Rutherford Backscattering measurement. It was found that most suitable nitrogen concentration is 3.15 at. %. We proposed a model to explain the nitrogen atom function in the recording layer. Nitrogen atom produced nitrides and distributed along the grain boundaries of Ge_2Sb_2Te_5 micro crystals for small nitrogen doping ( < 3.15 at. %). A further significant increase in the nitrogen concentration caused some of the nitrogen atoms to enter into the grains. It reduced the interfacial energy and led to merging of grains. XRD results verified the variation in grain size with increased nitrogen concentration. The optical properties of pure and doped Ge_2Sb_2Te_5 films were also investigated.