Phase change memory thin films from Ge-Sb-Te system with large (GeTe):(Sb2Te3) ratio have been deposited via UV pulsed laser deposition technique. The studied compositions were Ge6Sb2Te9, Ge8Sb2Te11, Ge10Sb2Te13, and Ge12Sb2Te15. Physico-chemical properties of the Ge-Sb-Te thin films, based on the scanning electron microscopy with energydispersive X-ray analysis, X-ray diffraction and reflectometry, atomic force microscopy, optical reflectivity, sheet resistance temperature dependences, and variable angle spectroscopic ellipsometry measurements, were studied in order to assess the effect of chemical composition of the deposited layers. All the obtained data confirm the importance of GeTe content in (GeTe)1-x(Sb2Te3)x thin films.
The unique properties of amorphous chalcogenides such as wide transparency in the infrared region, low phonon energy, photosensitivity and high linear and nonlinear refractive index, make them prospective materials for photonics devices. The important question is whether the chalcogenides are stable enough or how the photosensitivity could be exacerbated for demanded applications. Of this view, the Ge-Sb-Se system is undoubtedly an interesting glassy system given the antinomic behavior of germanium and antimony with respect to photosensitivity. The amorphous Ge-Sb-Se thin films were fabricated by a rf-magnetron co-sputtering technique employing the following cathodes: GeSe2, Sb2Se3 and Ge28Sb12Se60. Radio-frequency sputtering is widely used for film fabrication due to its relative simplicity, easy control, and often stoichiometric material transfer from target to substrate. The advantage of this technique is the ability to explore a wide range of chalcogenide film composition by means of adjusting the contribution of each target. This makes the technique considerably effective for the exploration of properties mentioned above. In the present work, the influence of the composition determined by energy-dispersive X-ray spectroscopy on the optical properties was studied. Optical bandgap energy Egopt was determined using variable angle spectroscopic ellipsometry. The morphology and topography of the selenide sputtered films was studied by scanning electron microscopy and atomic force microscopy. The films structure was determined using Raman scattering spectroscopy.