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Extended Study on Crystal Growth and Viscosity in Ge-Sb-Se Bulk Glasses and Thin Films
Year: 2017
Type of publication: článek v odborném periodiku
Name of source: Journal of Physical Chemistry B
Publisher name: American Chemical Society
Place: Washington
Page from-to: 7978-7986
Titles:
Language Name Abstract Keywords
cze Rozšířená studie růstu krystalů a viskozity v objemových sklech a tenkých vrstvách Ge-Sb-Se Rychlost růstu v objemových vzorcích a tenkých filmech Ge18Sb(28)Se(54) byla měřena pomocí optického mikroskopu a SEM za izotermních podmínek. Kompaktní krystalová vrstva rostla u objemových vzorků z povrchu. Žádná nuklea nebyla nalezena uvnitř vzorku. Z naměřených dat byla vypočtena závislost rychlosti růstu krystalů na teplotě. krystalizační chování; sklotvornost; tepelná stabilita; Ge-Sb-Se skla; difuze; kinetika
eng Extended Study on Crystal Growth and Viscosity in Ge-Sb-Se Bulk Glasses and Thin Films Crystal growth rates in Ge18Sb(28)Se(54) bulk glass and thin film were measured using optical and scanning electron microscopy under isothermal conditions. The studied temperature region was 255-346 degrees C and 254-286 degrees C for bulk glass and thin film, respectively. The compact crystalline layer growing from the surface into the amorphous core was formed in bulk glasses and no bulk crystallization was observed. In the case of thin films, needle-shape crystals were formed. The crystalline layer and needle-shape crystals grew linearly with time that corresponds to a crystal growth controlled by the crystal-liquid interface kinetics. In the narrow temperature range, crystal growth rates exhibit simple exponential behavior, so the activation energies of crystal growth for the studied temperature regions were estimated (EG = 294 6 kJ/mol for bulk glass and EG = 224 +/- 12 kJ/mol for thin film). Viscosity of Ge18Sb28Se54 material was measured in the region of the undercooled melt and glass. The extrapolation of viscosity data into the immeasurable, but important, temperature range is discussed. The experimental growth data were combined with melting and viscosity data and the appropriate growth models were proposed to describe crystal growth in a wide temperature region. The standard crystal growth models are based on a simple proportionality of the crystal growth rate to the viscosity (u proportional to eta(-1)). This simple proportionality holds for the bulk material. Nevertheless, in the thin films the decoupling of the crystal growth rate from the inverse viscosity occurs, and the standard kinetic growth models need to be corrected. Such corrections provide better description of experimental data and more realistic value of the parameter describing the mean interatomic distance in the crystal-liquid interface layer, where the crystal growth takes place. crystallization behavior; forming liquids; thermal-stability; ge2sb2se5 glass; diffusion; kinetics

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