Light-assisted physical aging in chalcogenide glasses: Dependence on the wavelength of incident photons
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Roman Golovchak and Oleh Shpotyuk
Lviv Scientific Research Institute of Materials of SRC “Carat”, Lviv UA-79031, Ukraine; and Institute of Physics of Jan Dlugosz University, Czestochowa PL-42201, Poland
Stefan Szymura School of Higher Vocational Education in Nysa, Institute of Management, Nysa PL-48300, Poland
Allisson Saiter and Jean-Marc Saiter AMME International Laboratory, LECAP EA4528, Institut des Matériaux de Rouen, Université de Rouen, Faculté des Sciences, 76801 Saint Etienne du Rouvray, France (Received 7 April 2011; accepted 5 August 2011)
Physical aging induced by an exposure of As–Se, As–S, and Ge–Se glasses to the light of different discrete wavelengths is studied using differential scanning calorimetry technique. The value of this effect is compared to the physical aging caused by natural storage in the dark. It is shown that a choice of As or Ge atoms does not influence significantly the spectral dependence of light-assisted physical aging, whereas substitution of Se with S causes drastic changes in the magnitude of the effect. The mechanism of the observed light-induced phenomena is discussed in terms of transient and metastable displacements of network chalcogen atoms.
I. INTRODUCTION
Photosensitivity of chalcogenide glasses (ChG) is known almost from the earliest stages of the invention of their semiconducting properties in 1950s by B.T. Kolomiets and N.A. Goryunova.1 Since that time, different effects induced by bandgap, sub-bangap, and above-bandgap light are reported,2–12 and numerous models of photoinduced structural transformations are developed.2,13–17 Photoinduced darkening/bleaching effect,2,3 optomechanical effect,4,5 photoexpansion/ photocontraction,6,7 photofluidity,8,9 photomelting/ 10,11 photocrystallization, and photodiffusion12 are only a few examples of the achieved progress in the field. At the same time, little attention was paid to the photostructural transformations associated with light-assisted physical aging phenomenon in ChG. This effect, however, is very important for practical application of these materials, since exploitation characteristics of ChG-based devices (such as optical elements, fibers, etc.) can undergo an uncontrolled drift with time and/or under the light exposure, significantly decreasing durability and reliability of the devices.18–21 Recent investigations of light-assisted physical aging were focused mostly on the compositional trends in
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Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2011.264 2420
J. Mater. Res., Vol. 26, No. 18, Sep 28, 2011
http://journals.cambridge.org
Downloaded: 11 Mar 2015
Se-based ChG using sub-bandgap light (laser sources) with wavelengths from almost transparent region of ChG spectra for excitation.20–22 The magnitude of the observed photorelaxation phenomena was shown to be dependent upon the intensity of sub-bandgap light, as well as upon the thermal prehistory of the samples.20–23 A summative bond breaking mechanism discussed within a concept of strong/fragile glass-formers23
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