Nanocomposites and nanomaterials

Crystallization processes and optical properties
of Ge-Ga-Se glasses
H. Klym1, O. Shpotyuk2, L. Calvez3, 
I. Karbovnyk4, M. Cestelli Guidi5, A.I. Popov6

1 Lviv Polytechnic National University, 12, Bandery Str., Lviv, 79013, Ukraine 
E-mail: halyna.i.klym@lpnu.ua; klymha@yahoo.com 
2 Vlokh Institute of Physical Optics, 23, Dragomanova Str., Lviv, 79005, Ukraine
3 Equipe Verres et et Céramiques, UMR-CNRS 6226, Institute des Sciences chimiques de Rennes, Université de Rennes 1, 35042 Rennes Cedex, France
4 Department of Electronics and Computer Technologies, Ivan Franko National University of Lviv, 107, Tarnavskogo Str., Lviv, 79000, Ukraine
5 INFN_Laboratori Nazionali di Frascati, Via E. Fermi 40, Frascati, 00044, Italy
6 Institute for Solid State Physics, University of Latvia, 
Kengaraga 8, Riga, 1063 Latvia

The Ge-Ga-Se chalcogenide glasses are known for their wide application in optoelectronic systems and IR photonics. The crystallization processes in such materials as glass can refine their thermal and exploitation properties. In this work, we analyze crystallization processes on the surface of 80GeSe2-20Ga2Se3 glasses and their optical properties.
It is shown that crystallites of GeSe2 phase are formed in the crystallized glasses on the surface. It is established that with prolongation of the thermal annealing of 80GeSe2-20Ga2Se3 glasses, additional crystallization of GeSe2 phase.
Studied crystallization processes in the 80GeSe2-20Ga2Se3 glasses influence on their optical transmission spectra. The base non-annealed samples show maximum of transmission on 65 %. Annealing at 380 °C is results in decreasing of the transmission and long-wave shift of optical transmission edge. With increasing heat treatment time to 80 and 100 h, the crystallization of GeSe2 on the glass surface provokes a decrease of the transmittance. The GeSe2 crystallites with a big size are precipitated on the surface of glasses crystallized for long time. The size of inner Ga2Se3 and GeGa4Se8 nanocrystallites is much smaller than crystals on the surface and no change with the elongation of heat-treatments, suggesting that the crystallization of inner crystal phase has been finished after about 50 h.