Science and Education a New Dimension: Natural and Technical Science. Vol. 8, 2013 PHYSICAL AND MATHEMATICAL SCIENCE Mitsa V. 1 , Borkach E. 2 , Lovas G. 1 , Holomb R. 1 , Rosola I. 1 , Rudyko G. 3 , Gule E. 3 , Fekeshgazi I. 3 The visible photoluminescence from aged and freshly fractured surfacees of chalcogenide glasess 1 Uzhhorod National University, Institute for Solid State Physics and Chemistry, Uzhhorod, Ukraine E-mail: v.mitsa@gmail.com 2 II. Rákóczi Ferenc Transcarpathian Hungarian Institute, Beregovo, Ukraine 3 Lashkarjov Institute Physics of Semiconductors, National Academy of Science, Kiev, Ukraine Abstract: The position of PL maximum at E 1 =2.43 in PL spectrum of freshly fractured g-As 2 S 3 is in good agreement with early found “hot luminescence” g-As 2 S 3 and illumination of elemental sulfur species on the surface of the ZnS nanobelts in this region. PL radiation from long term aged fractured surfaces of GeS 2 -based chalcogenide glasses was assigned to the surface contaminant effect from native oxidized layer, which might have formed in the air. When have been used for PL measuring the freshly fractured surface of g-GeS 2 (T 3 V 2 ) all PL peaks which was connected with GeO x species where disappeared in PL spectrum. Keywords: visible photoluminescence, chalcogenide glass, oxide phase, edge absorption, glassy GeS 2 Introduction Wide band chalcogenide glassy semiconductors (ChGS) have been studied as host materials for different types of ions due to potential applications as optical amplifiers for the telecommunications window and nonlinear optical media for high-speed all-optical signal processing [1-4]. Nowadays optical and electronic properties of nanostructured ChGS have attracted much attention because they exhibit useful phenomena and have potentials for becoming novel media for future photonic devices [5]. Earlier we have measured low temperature photoluminescence (PL) in nanostructured wide band ChGS by using a projector lamp as excitation light source [6]. The position of peak energies near 1.1-1.3 eV in measured PL spectra in this case were corresponding to so called “half-gap” rule [7-9]. During last decades for exiting PL and Raman spectra of ChGS a different laser lines were intensively used [2-4, 10-18] and some deviation from above mentioned rule in PL spectra of some ChGS was found [11, 12]. The low temperature PL spectrum of g-GeS 2 obtained with two different excitation energies at 2.7 and 2.81 eV each has two peaks with position of main peak energies at 2.20 and 2.28 eV correspondingly. The shape of this luminescence bands was dependent on the excitation wavelength [11]. The low temperature PL spectrum of nanostructured (GeS 2 ) 100-x (GeO 2 ) x glasses exited by 3.1 eV laser line is blue shifted from 1.3 to 2.1 eV when x increases from x=0 to x=80 [12]. Room temperature PL in the visible range of nanocrystalline (nc) nc-Ge was reported in literature and attributed to different origins [15-18]. From chemically etched Ge the 2.3-2.3 eV visible PL (exited photon energy, E ex =2.8 eV) was assigned to GeO x species [16]. The PL results presented in [17] shows that visible luminescence (E ex =3.81 eV) of the porous Ge thin films originated from the germanium oxide. A number of mentioned above results show that exact mechanism of luminescence in nc-Ge is still under discussion. Nanostructured ChGS are known to be susceptible to oxide impurities [19]. Presented here new results of experimental investigation of Ge-free binary g- As 2 S 3 , g-GeS 2 glass and ternary (GeS 2 ) x (As 2 S 3 ) 100-x glasses at high energy of PL excitation might add new information about the nature of luminescence in nanostructured materials. Materials and methods Glasses were prepared from the mixture of high- purity germanium (99.999 wt. %), elemental sulfur and arsenic refined by vacuum distillation. The mixture was synthesized in the evacuated (~10 -3 Pa) quartz ampoules by step-wise gradual heating up to 973 K for g-As 2 S 3 sample and 1223 K for Ge- containing samples in a rocking furnace. The g- GeS 2 samples for PL measuring were synthesized by melt quenching from different temperatures ranging from 1173 K (T 1 ) to 1473 K (T 4 ) and quenching rate from 100 K/s (V 1 ) and 150 K/s (V 2 ) (hereafter be denoted T i V j ). The long term aged (9 years) of samples fractured surfaces were excited by cw laser illumination of 3.03 eV. From comparison of PL spectra a fresh fractured surfaces was used. An exiting diode laser scattering was filtering by cut-off filter at E>2.75 eV. To study the light absorption of these glasses by convenient method, transmittance and reflectance spectra from polished samples have been used to extract the absorption coefficient (α). Results and discussion When the fresh fractured surface of bulk glass of g-As 2 S 3 with inclusion of realgar-type As 4 S 4 molecules was chosen[13] it gives in PL spectrum an intensive narrow symmetric PL signal which ma- ximum is centered at E 1 =2.43 eV with low energy side band at E 2 =1.7 eV (Figure 1). The excitation energy (3.03 eV) was higher than optical band-gap 61