Far-infrared transmission and bonding arrangement in Ge 10 Se 90x Te x semiconducting glassy alloys Pankaj Sharma * , S.C. Katyal Department of Physics, Jaypee University of Information Technology, Waknaghat, Solan, HP 173 215, India article info Article history: Received 3 November 2007 Received in revised form 4 April 2008 Available online 26 June 2008 PACS: 63.50.Lm 33.20.Ea 77.84.Bw Keywords: Infrared glasses Chalcogenides FTIR measurements Structure abstract The far-infrared spectra of Ge 10 Se 90x Te x where x = 0, 10, 20, 30, 40, 50 glassy alloys were measured in the wavenumber region 50–650 cm 1 at room temperature. The results were explained in terms of the vibra- tions of the isolated molecular units. The addition of Te in Ge 10 Se 90 has shown the appearance of GeTe 2 and GeTe 4 molecular units and vibrations of Se–Te bond as Se 8x Te x mixed rings. The assignment of var- ious absorption bands has been made on the basis of absorption spectra of pure Se, binary Ge–Se, Ge–Te, Se–Te and ternary Ge–Se–Te glassy alloys. The far-infrared transmission spectrum has been found to shift a little towards lower wavenumber side with the addition of Te content to Ge 10 Se 90 . The addition of Te to Ge–Se system replacing Se has found to reduce the Se–Se bonds and Ge–Se bonds and leads to the for- mation of Se–Te, Ge–Te and Te–Te bonds. Ó 2008 Elsevier B.V. All rights reserved. 1. Introduction Chalcogenide glasses have attracted the attention of many investigators due to the fact that they are potential candidates for applications in infrared optics, photonics device, reversible optical recording, memory switching, inorganic photoresists and antireflection coatings [1–3]. The main applications of this kind of glasses are for transmission in infrared (IR) range for optical communications systems [2,3]. Chalcogenide glasses have advan- tages in comparison with oxide glasses and single crystals in that they possess the possibilities of wide refraction index variation depending on their chemical composition [4], as well as the ability to ‘tune’ other important physical and optical properties. The tai- loring of chalcogenide glasses for specific properties, i.e., optical, electrical etc., is possible but it requires enough knowledge about the glass systems according to compositions. The variation in opti- cal properties and electrical properties of chalcogenide glasses is mostly related to their structural behavior. It is the intent of pres- ent paper to develop a basic understanding of the structural behav- ior of selenide-telluride-germanium based glasses. An understanding of the structure of an amorphous material is essential to understand its physical properties. Determining the structure of glasses is difficult for two main reasons. First, unlike for the crystal, there is no direct probe such as X-ray diffraction that can determine the structure of a glass uniquely. This is due to the absence of long range order in the glasses. Second, the glass may be in one of many possible metastable states. These metasta- ble states consist of different atomic configurations which may dif- fer only slightly from one another and result in physical properties very similar to one another. The particular state in which a glass re- sides is dependent on its history of preparation. That is, the glass forming ability is influenced by the quenching rate, the amount of the sample prepared and the temperature from which the melt of sample is quenched. IR absorption of solids can provide useful information about the lattice vibrational density of solids and structure of solids. In order that the mode of vibration can absorb, a mechanism for coupling the vibration motion to electromagnetic radiation must exist. The basic mechanism is that the motion pro- duces an oscillatory dipole moment which can be driven by oscil- lating electric field of radiation. Raman scattering in solids is associated with the change of polarizability corresponding to the vibrational modes. The vibrations that contribute to IR absorption can be quantitatively separated into different types of modes char- acterized by three frequency regimes; low frequency acoustic modes, intermediate frequency bond bending modes and high fre- quency bond stretching modes. The bond stretching mode gener- ally yield the most direct structural information since their * Corresponding author. Tel.: +91 1792 239220; fax: +91 1792 245362. E-mail addresses: pankaj.sharma@juit.ac.in, pks_phy@yahoo.co.in (P. Sharma). Journal of Non-Crystalline Solids 354 (2008) 3836–3839 Journal of Non-Crystalline Solids doi:10.1016/j.jnoncrysol.2008.05.010