Nitrogen contribution to N-doped GeTe (N: 8.4 at.%) in the structural phase transition

Chemical states of N-doped GeTe (N: 8.4 at.%) thin film (NGT) in structural phase transition were investigated by near-edge x-ray absorption of fine structure and high-resolution x-ray photoelectron spectroscopy with synchrotron radiation. We found the NaCl-like structure in NGT by x-ray diffraction at around 300 °C. Preparatory to the analysis of chemical states, after mild Ne+ sputtering we obtained clean amorphous NGT, which showed the N2 vibration mode peak in the N K-edge absorption spectrum. After annealing, the N2 molecular peak disappeared completely and we assumed that nitrogen was contributed only to the Ge atom in structural phase transition by analyzing Ge 3d and Te 4d core-levels.

Research highlights
► We performed NEXAFS and HRXPS experiments on N-doped GeTe (N: 8.4 at.%).
► We found the N2 molecular vibration mode peak in the absorption spectra of the amorphous phase.
► The vibration mode peak completely disappeared after annealing.
► We confirmed the chemical states of Te–GeNx (x > 1), N–Ge and N–Ge–Te.
► The nitrogen contribution to the N-doped GeTe system, in the structural transition, was incorporated only with Ge.