Amorphous and crystallized Ge–Sb–Te thin films deposited by pulsed laser: Local structure using Raman scattering spectroscopy

• DOI: 10.1016/j.matchemphys.2012.08.024
• Publication Date: 2012-08-31T20:48:12Z
• Authors: P. Němec; V. Nazabal; A. Moreac; J. Gutwirth; L. Beneš; M. Frumar
• Keywords: Thin films; Raman spectroscopy and scattering; Vacuum deposition; [CHIM.MATE]Chemical Sciences/Material chemistry; 02 engineering and technology; 0210 nano-technology; Chalcogenides

Abstract UV pulsed laser deposition was employed for the fabrication of amorphous (GeTe) x (Sb 2 Te 3 ) 1− x , ( x = 1, 0.66, 0.5, 0.33, and 0) thin films. The local structure of as-deposited (amorphous) as well as annealed (crystallized) layers was studied using Raman scattering spectroscopy. Raman spectra were recorded on bulk materials used for the deposition as well. The vibrational modes observed in amorphous Ge–Sb–Te films are attributed, apart from defective octahedral coordination, to GeTe 4− n Ge n ( n = 1, 2, eventually 0) corner- and/or edge-sharing tetrahedra and SbTe 3 pyramidal entities, the latter dominated Raman spectra of all the films containing Sb 2 Te 3 . The structure of crystallized GeTe and Sb 2 Te 3 resembled that of starting bulk materials which is evidenced by the presence of Γ 3 (E) and Γ 1 (A 1 ) modes of rhombohedrally deformed rocksalt GeTe and E g (2) and A 1g (2) modes of hexagonal Sb 2 Te 3 . We propose that in case of crystallized Ge 2 Sb 2 Te 5 , Ge 1 Sb 2 Te 4 , and Ge 1 Sb 4 Te 7 films, Raman active features might be attributed to defective octahedral local structure and/or softened A 1 mode of corner-sharing GeTe 4 tetrahedra, A 1 mode of corner-sharing GeTe 4− n Ge n ( n = 1, 2) tetrahedra, GeTe 4 F 2 mode, Sb–Te mode in SbTe 3 entities, eventually E g (2) and A 1g (2) modes of hexagonal Sb 2 Te 3 .