Aging process of photosensitive chalcogenide films deposited by electron beam deposition

International audienceChalcogenide films attract broad interest due to their use as optical components like narrow band-pass filters, omnidirectional reflectors cladding, all-optical signal processing devices or optochemical sensors. Ge15Sb20S65 and As30Se50Te20 chalcogenide amorphous films were deposited by electron beam deposition (EBD) using their corresponding bulk glasses as targets. The structure of both bulk and thin film has been studied by far-IR and Raman spectroscopy. This study investigated an ordinary aging behavior of the chalcogenide films by exposing them to natural light under atmospheric conditions for a period of six months. Both films were found to be photosensitive as manifested by the shift of their optical band-gap to shorter or longer wavelength depending on chemical composition. Aging was found to induce also morphological changes, most notably the likely growth of arsenic trioxide micro-crystals on the surface of As30Se50Te20 films. Such effects were discussed in terms of photo-oxidation and photo-hydrolysis phenomena, the extent of which was found to be relatively limited for Ge25Sb10S65 films. The larger stability of the latter films against crystal growth at the surface was associated with the ability of germanium to bond to diffusing oxygen atoms in germanium-oxysulfide tetrahedral arrangements

Structural characterizations of As-Se-Te glasses

International audienceThe atomic structure of chalcogenide glasses As3Se7−xTex (0 ≤ x ≤ 3) and As2Se3−xTex (0 ≤ x ≤ 2.5) has been investigated by different methods. Short-range order has been studied by Wide-Angle X-ray Scattering (WAXS). 77Se NMR as well as Raman and infrared measurements were also performed on the different compositions. We show that the progressive introduction of tellurium in As3Se7−xTex or As2Se3−xTex induces breaking of Se-Se bonds and the formation of AsSe3−xTex pyramidal units. Experimental data also reveal the absence of Te-Te bonds even in the tellurium richest composition which let suppose a homogeneous repartition of tellurium atoms in the glassy network

Er3+-Al2O3 nanoparticles doping of borosilicate glass

Novel borosilicate glasses were developed by adding in the glass batch Er3+–Al2O3 nanoparticles synthetized by using a soft chemical method. A similar nanoparticle doping with modified chemical vapour deposition (MCVD) process was developed to increase the efficiency of the amplifying silica fibre in comparison to using MCVD and solution doping. It was shown that with the melt quench technique, a Er3+–Al2O3 nanoparticle doping neither leads to an increase in the Er3+ luminescence properties nor allows one to control the rare-earth chemical environment in a borosilicate glass. The site of Er3+ in the Er3+–Al2O3 nanoparticle containing glass seems to be similar as in glasses with the same composition prepared using standard raw materials. We suspect the Er3+ ions to diffuse from the nanoparticles into the glass matrix. There was no clear evidence of the presence of Al2O3 nanoparticles in the glasses after melting

Mixed alkali/alkaline earth-silicate glasses : Physical properties and structure by vibrational spectroscopy

In this article, we investigate the correlation of selected physical properties with structural changes in quaternary mixed modifier alkali/alkaline earth oxide silicate glass  systems,  focusing  either  on  the  mixed  alkali  effect  [(20−x)Na2O–xK2O– 10CaO–70SiO2 (x = 0, 5, 10, 15, 20)] or on the mixed alkaline earth effect [20Na2O– (10−y)CaO–yBaO–70SiO2 (y = 0, 5, 10)]. A maximum microhardness and packing density, as well as a minimum glass transition temperature were observed for mixed alkali glasses. The mixed alkaline earth glasses do not exhibit any clear extrema in any  of  the  properties  studied.  The  hardness  and  glass  transition  temperature  de-creases, while the density and molar volume increases with increasing BaO content. Raman spectroscopy showed an increase in the Q3 group compared to the Q2 and Q4 groups as the high field strength ions Na+ or Ca2+ are substituted by their low field strength analogs K+  or Ba2+. In the mixed alkali series, the high field strength ion Na+, seems to push the low field strength ion K+ into lower energy sites when present simultaneously, while such an effect is not apparent for the mixed alkaline earth glasses, where the far IR spectra of mixed glasses are equivalent to the weighted averages of the pure glasses