Chemical states of Bi-doped GeTe (Bi: 6 at.%) thin film in structural phase transition investigated by synchrotron X-ray photoelectron spectroscopy

abstractThe chemical states of Bi (6 at.%)-doped GeTe thin film (GBT) in structural phase transition were investigated by high-resolution X-ray photoelectron spectroscopy (HRXPS). Clean amorphous GBT was phase changed to the NaCl-type crystalline structure by in-situ annealing under ultrahigh vacuum, during which transition, the binding energy and shape of the Te 4d core-level showed no changes, the Ge 3d core-level showed a spin-orbit split-enhanced feature with negligible chemical shift, and the Bi 4f core-level became narrower and shifted towards the higher binding energy side by 0.25 eV. We suggest that as the film phase changed to the meta-stable crystalline structure, the Ge and Bi atoms moved to more constrained sites in the electron configuration.