Low temperature epitaxy of Ge-Sb-Te films on BaF2 (111) by pulsed laser deposition

摘要

Pulsed laser deposition was employed to deposit epitaxial GeSbTe-layers on the (111) plane of BaF single crystal substrates. X-ray diffraction measurements show a process temperature window for epitaxial growth between 85 °C and 295 °C. No crystalline growth is observed for lower temperatures, whereas higher temperatures lead to strong desorption of the film constituents. The films are of hexagonal structure with lattice parameters consistent with existing models. X-ray pole figure measurements reveal that the films grow with one single out-of-plane crystal orientation, but rotational twin domains are present. The out-of-plane epitaxial relationship is determined to be GeSbTe(0001) || BaF(111), whereas the in-plane relationship is characterized by two directions, i.e., GeSbTe [-12-10] || BaF[1-10] and GeSbTe[1-210] || BaF[1-10]. Aberration-corrected high-resolution scanning transmission electron microscopy was used to resolve the local atomic structure and confirm the hexagonal structure of the films.