Seminars Archive

Fri 8 Mar, at 15:00 - Seminar Room T2

Self-organization and induced processes in chalcogenide nanolayers: experimental and theoretical studies

O. Kondrat
Uzhhorod National University, Uzhhorod, Ukraine

The structure of amorphous thin As2S3 and As2Se3 nanolayers were investigated by means of photoelectron and Raman spectroscopy including high surface sensitive methods, SRPES and SERS. Results show that the surface of amorphous As2Se3 nanolayers is a network with mainly AsSe3 pyramidal ring and/or chain morphology. Only the small amount of S-S (bridges) and As-As (As4S3) was detected. On the contrary, the deeper amorphous As2S3 layers contain significant amount of As-As bonds characteristics of realgar-like As4S4 molecules. Near bandgap laser irradiation of As2Se3 film lead to drastic changes in the structure of both surface and deeper layers and to As-O bonds (oxidation to As2O3) formation. There is no sign detected of intensive pararealgar formation at the surface. The relative contribution of the As, Se, C and O atoms in different chemical states to the whole As 3d, Se 3d, C 1s and O 1s signals, its structural origins as well as their relation to the As40Se60 surface and subsurface nanolayers structure before and after laser irradiation is analyzed and discussed in detail. An atomic model of induced structural changes on the surface of As40Se60 nanolayers under ambient conditions and after laser irradiation in air is proposed. The local and medium range structures, electronic and optical properties of binary Ge-S and Ge-Se non-crystalline systems were also investigated by means of photon energy dependent Raman spectroscopy and ab initio DFT calculations.

(Referer: K. Prince)
Last Updated on Tuesday, 24 April 2012 15:21