Journal of Alloys and Compounds 456 (2008) 425–428 Dielectric properties in aged amorphous silicon oxide thin film F. Tarrach, A. Ch’hayder, H. Guermazi, S. Guermazi ∗ Unit´ e de Recherche, Physique des Mat´ eriaux Isolants et Semi-isolants, Institut Pr´ eparatoire aux Etudes d’Ing´ enieurs de Sfax, BP 805, 3018 Sfax, Tunisia Received 20 November 2006; received in revised form 9 February 2007; accepted 12 February 2007 Available online 16 February 2007 Abstract In this paper, we report structural and electrical characterization of amorphous silicon oxide films. We have investigated the effect of thermal accelerated ageing on the physico-chemical properties of a-SiO x by means of Infrared spectroscopy and fluorescence X. IR spectroscopy reveals the presence of Sn–O and Sn–H features in the studied samples. The transversal vibration ν(Si–O), which appeared at 1020 cm -1 , is observed to disappear with the thermal ageing. The dielectric constant (ε) and dielectric loss (ε ′′ ) have been measured for the frequency range between 20 Hz and 1 MHz. Results show an increase of the electric loss and a decrease in the electric conductivity with the ageing time thus aged samples tend to be insulator in character. These effects are related to the increase of structural defects. A Cole–Cole model is used to analyse the relaxation parameters and the distribution of relaxation time. A very good overlap of data was obtained. © 2007 Published by Elsevier B.V. Keywords: a-SiO x IR spectroscopy; Dielectric dispersion; Cole–Cole analysis 1. Introduction Silicon oxides SiO x with 0 < x < 2 have attracted a great interest in fiber technology and opto electronic research. This attention is due to the low cost of silicon and its specific phys- ical properties [1–3]. Different allotropic forms of SiO x were reported in order to investigate their structural and optical quality [4–7]. Refractive indexes and dielectric constants of thin amor- phous SiO x films have been extensively investigated [8–13]. Hogarth and Wright [14] found an improvement in the dielectric properties of composite SiO x /B 2 O 3 with increase in the B 2 O 3 content compared with the sample SiO x . Rahman et al. [15] stud- ied the SiO/SnO 2 thin films and suggested that the films tend to be dielectric in character, even though SnO 2 is a fairly good conductor. This paper focuses on the effect of thermal accelerated age- ing on amorphous structure properties of silicon oxide thin films. Dielectric dispersion properties are reported for the frequency range from 20 Hz to 1 MHz and analysed by the Cole–Cole ∗ Corresponding author. Tel. +216 74 241 403; fax: +216 74 246 347. E-mail address: samir.guermazi@ipeis.rnu.tn (S. Guermazi). model to determine the relaxation parameters and distribution of relaxation time. 2. Experimental results The samples studied in this work are a commercial silicon oxide films SiO x delivered by the Glassware Marienfeld laboratory. They have dimension of 20 mm × 20 mm × 0.16 mm. They were submitted to thermal constraints in a Memmert ULE 500 steam room at different times. Thermal ageing consists in applying several heat-cooling cycles. The cycle is composed of four stages: (1) heating from 23 to 85 ◦ C during 2 h, (2) keeping at 85 ◦ C during 1 h, (3) cooling to 23 ◦ C during 4 h, (4) keeping at 23 ◦ C during 1 h. Thus, a whole cycle lasts 8 h. 2.1. Physico-chemical characterization In order to determine the chemical elements present in the studied sample, Fluorescence X analysis were carried out. The X-ray reflectometer used in this study has been designed and constructed at the “Laboratoire de Physique du Cnam” [16,17]. The Fluorescence X detector is a KETEK AXAS-SDD (Silicon Drift Detector). The spectrum was represented in Fig. 1. It indicates the presence of the X-rays of Si, Sn and Ti elements. In order to identify whether Sn and Ti are interstitial impurities or structural bonded elements, IR spectroscopy was used. The measurements were performed using Bruker IFS66V/S IR spectrometer with a resolution of 2 cm -1 . Fig. 2a displays the IR spectrum of the virgin sam- 0925-8388/$ – see front matter © 2007 Published by Elsevier B.V. doi:10.1016/j.jallcom.2007.02.051