Eur. Phys. J. Appl. Phys. 36, 11–15 (2006) DOI: 10.1051/epjap:2006097 T HE EUROPEAN P HYSICAL JOURNAL APPLIED PHYSICS Growth and optimization by post-annealing of chalcopyrite CuAlS 2 compound R. Brini 1, a , G. Schmerber 2 , M. Kanzari 1 , B. Rezig 1 , and J. Werckmann 2 1 Laboratoire de Photovolta¨ ıque et Mat´ eriaux Semiconducteurs (LPMS), ´ Ecole Nationale d’Ing´ enieurs de Tunis (ENIT), BP 37, le Belv´ ed` ere, 1002 Tunis, Tunisia 2 Institut de Physique et Chimie des Mat´ eriaux Strasbourg (IPCMS), 23 rue du Loess, BP 43 CP, 67034 Strasbourg, France Received: 13 April 2006 / Received in final form: 18 May 2006 / Accepted: 15 June 2006 Published online: 5 September 2006 – c  EDP Sciences Abstract. The chalcopyrite CuAlS2 compound was grown from stoichiometric melt by horizontal Bridgman method. The obtained ingots were crushed finely and annealed at different temperatures from 800 ◦ C to 1100 ◦ C under a gas mixture of 5% N2/H2 atmosphere. X-ray diffraction and Raman spectroscopy were used to investigate the layer microstructures, as well as their lattice vibration spectra. The layers were characterized by scanning electron microscopy (SEM) and the compositional analyses were done by energy dispersive X-ray microanalysis (EDX). Raman measurements of the as made powder indicated seven prominent peaks at 205, 250, 290, 340, 369, 418 and 457 cm -1 with large intensity at 457 cm -1 . The peaks at 205, 250, 340 and 457 cm -1 were ascribed to B2 modes while the peaks 369 and 418 cm -1 were ascribed to E modes. The peak at 290 cm -1 may be assigned to the A1 mode. After annealing, the Raman features become better and phonon mode at 290 cm -1 looks more distinct. The stoichiometric CuAlS2 compound was obtained when the sample was annealed at 900 ◦ C. PACS. 81.05.Hd Other semiconductors – 61.10.Nz X-ray diffraction – 78.30.Hv Other nonmetallic inor- ganics – 68.37.Hk Scanning electron microscopy (SEM) (including EBIC) 1 Introduction Recently, a great deal of interest has been focused on the growth of the ternary I–III–VI 2 and II-IV-VI 2 semicon- ductor compounds which crystallize in the chalcopyrite type structure [1–4]. Within this family there are many ternary compounds which have a band gap of in the range of 3.5–1.0 eV [5]. Covering the wide spectral region from ultraviolet to near infrared and having different attractive linear and nonlinear optical properties. One of the promis- ing chalcopyrite-type semiconductors for nonlinear optical applications is copper aluminium disulfide CuAlS 2 , which has a direct gap of 3.49 eV [6,7] at room temperature, the widest value among other chalcopyrite compounds. It has been studied intensively as one of the potential candidates for absorber materials in polycrystalline thin film solar cells, due mainly to its high absorption coefficient. Recent progress in the growth of CuAlS 2 layers on Si(100), Si(111) and GaAs substrates by thermal evaporation makes them even more technologically promising. In fact, the nature and origin of the high nonlinear optical susceptibility and Raman scattering efficiency are closely interrelated. In- gots of the ternary compound CuAlS 2 can now be readily grown by the Bridgman method, which are free of mi- a e-mail: mounir.kanzari@ipeit.rnu.tn crocracks and voids [8]. They were prepared due to their possible technological applications as photovoltaic optical detectors, solar cells, light emitting diodes or in nonlin- ear optics, the I.III.VI 2 chalcopyrite semiconductors have recently attracted the attention of the physicists [9,10]. In the present work, we have investigated a series of ingots of CuAlS 2 grown using an horizontal Bridgman method from stoichiometric melts. The study focused on the relationship between the effects of post-annealing of the powder of CuAlS 2 content on compositions and lattice constants were studied in details. We report the synthesis of CuAlS 2 using the closed-tube transport technique and the post-thermal treatment. The outcome of this study is expected to contribute to a better understanding of the properties of the absorber materials and their impact on the quality of the grown thin films in order to obtain high- quality crystals that are suitable for optical and electrical in order to improve the efficiency of the solar cells. All samples were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). Further more the Raman reflectivity measurements in backscattering configuration were performed at room temperature at the same wave number range from 100 to 600 cm -1 . Article published by EDP Sciences and available at http://www.edpsciences.org/epjap or http://dx.doi.org/10.1051/epjap:2006097