CORE ABSORPTION-SPECTRA OF CRYSTALLINE AND AMORPHOUS GETE THIN-FILMS

Core absorption spectra of crystalline (c-) and amorphous (a-) GeTe thin films have been measured in the 26-70 eV region. Photoemission spectra have also been measured to determine the binding energies of Ge 3d and Te 4d core levels. In the c-phase Ge 3d absorption shows excitonic peaks which can be explained in atomic picture, while Te 4d absorption shows broad structures which reflect DOS of the conduction band. A small peak was found below the broad structures of Te 4d absorption, the origin of which is the excitonic transition or the transition to the hole states generated by Ge vacancies located near the top of the valence band. In the a-phase Ge 3d absorption shows a broad structure while Te 4d absorption somewhat sharp doublet. The difference in the spectral features in both phases suggests that the bonding character is more covalent in a-GeTe than in c-GeTe. © 1990, THE PHYSICAL SOCIETY OF JAPAN. All rights reserved.