Raman study of ion irradiated GeSe films

Abstract Films of a-Ge 20 Se 80 prepared by vacuum evaporation, are exposed to visible light and irradiated with 1 MeV Krypton ions. The changes in bonding configurations are studied by Raman spectroscopy. Three bands are observed in the virgin films and are identified as corresponding to the stretching mode of GeSe 4/2 corner-sharing tetrahedra (201 cm −1 ) and to the vibrations of Se atoms in four member rings composed of two edge sharing tetrahedra (215 cm −1 ) and Se–Se chains (263 cm −1 ). Upon ion irradiation the band positions remain unchanged and no new band appears. In contrast, light soaking produces an additional band at 257 cm −1 . This bond has been identified as arising from the stretching vibrations of Se atoms in helical chain-like and ring-like arrangements. A study of the relative areas under the peaks shows that ion-irradiation causes the Se–Se bridges linked with GeSe 4/2 units to convert into Se–Se chains and the number of GeSe 4/2 bonds remain unchanged. Upon light soaking, the density of corner-sharing GeSe 4/2 bonds increases, no significant variation is observed in the Se bonds. In addition, the width of the peak at 201 cm −1 decreases after ion irradiation but increases upon light soaking. These data show that ion irradiation induces bond changes in Ge 20 Se 80 , which are different from those, created by light soaking.