Nanocomposites and nanomaterials

On the surface crystallization process 
in Ge-Ga-Se chalcogenide glasses
H. Klym1, I. Karbovnyk1,2, O. Shpotyuk3, L. Calvez4

1 Lviv Polytechnic National University, 12, Bandery Str., Lviv, 79013, Ukraine 
E-mail: halyna.i.klym@lpnu.ua; klymha@yahoo.com 
2 Department of Electronics and Computer Technologies, Ivan Franko National University of Lviv, 107, Tarnavskogo Str., Lviv, 79000, Ukraine
3 Vlokh Institute of Physical Optics, 23, Dragomanova Str., Lviv, 79005, Ukraine
4 Equipe Verres et et Céramiques, UMR-CNRS 6226, Institute des Sciences chimiques de Rennes, Université de Rennes 1, 35042 Rennes Cedex, France

The Ge-Ga-Se chalcogenide glasses (ChG) are known for their wide application in optoelectronic systems and IR photonics [1]. The crystallization processes in such materials as glass and glass-ceramics can refine their thermal and exploitation properties. In such cases transmission often decreases because the growth of crystals is not controlled, this makes the materials non-transparent.
In this work, we analyze crystallization processes on the surface of 80GeSe2-20Ga2Se3 ChG caused by thermal treatment for 25 and 80 h using atomic force microscopy (AFM) probes.
Investigated 80GeSe2-20Ga2Se3 ChG were obtained from Ge, Ga and Se high pure materials. The crystallization of the 80GeSe2-20Ga2Se3 glasses were performed at 380 oC (Tg + 10 oC) [2]. 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 occurs on the surface, contributing redistribution of their internal free volume. Optimal conditions for crystallization of ChG were selected.

1.	Adam J.L., Calvez L., Trolès J., Nazabal V. Chalcogenide glasses for infrared photonics // International Journal of Applied Glass Science, 2015,   6(3), 287-294. 
2.	Klym H., Ingram A., Shpotyuk O., Calvez L., Petracovschi E., Kulyk B., Serkiz R., Szatanik R. “'Cold' crystallization in nanostructurized 80GeSe2-20Ga2Se3 glass // Nanoscale research letters, 2015, 10(1), 1-8.