Materials Science and Engineering B 134 (2006) 63–67 Optical manipulation of temperature formation of CuInSe 2 thin films A. Ashour a,∗ , A.A.S. Akl a , A.A. Ramadan b , N.A. El-Kadry a , K. Abd El-Hady a a Faculty of Science, Physics Department, Minia University, Minia, Egypt b Faculty of Science, Physics Department, Helwan University, Helwan, Egypt Received 22 April 2006; received in revised form 26 June 2006; accepted 23 July 2006 Abstract Polycrystalline thin films of CuInSe 2 were grown onto glass substrates using the stacked elemental layer (SEL) technique involving the annealing at different temperatures in air atmosphere for different times. The variation in the structure and optical properties of the CuInSe 2 thin films on the annealing temperature and time was investigated using X-ray diffraction (XRD) and optical measurements, respectively. The different structural properties were clearly reflected in X-ray diffraction studies. It was concluded that CuInSe 2 phase is dominated at annealing temperature of 300 ◦ C for a time ≥1 h. Ternary phase of CuInSe 2 was characterized by highly both transmission and absorption, optimization of the optical constants and band gap. Optical absorption studies indicate a direct band gap range around 1.0 eV. The data on structural and optical properties covering this technique will be presented. © 2006 Elsevier B.V. All rights reserved. Keywords: Stacked elemental layer (SEL); CuInSe 2 ; XRD; Optical properties 1. Introduction Copper indium diselenide with a direct band gap of 1.1 eV and high absorption coefficient has been extensively studied for photovoltaic and photoelectrochemical solar cells applications [1–4]. It can be grown with p- as well as n-type doping and, therefore, both homojunction and heterojunction thin film solar cells have already demonstrated terrestrial active area conversion efficiencies of over 18% [5]. Techniques such as flash evapora- tion, RF and ion beam sputtering, molecular beam epitaxy, spray pyrolysis, electrodeposition, and co-evaporation have all been employed in the production of thin film solar cells [6–9]. Preparation of CuInSe 2 (CIS) thin films for photovoltaic application by stacked elemental layers (SEL), and followed by thermal annealing seems more attractive on the economic considerations [10]. In this study, the structural and optical properties of polycrys- talline CIS absorbers, which have been grown by SEL technique, were mainly characterized by X-ray diffraction, reflection and transmission measurements. The variation of the parameters on them is discussed. ∗ Corresponding author. Tel.: +2 086 2369149; fax: +2 086 2363011. E-mail address: aashour 2000@Yahoo.com (A. Ashour). 2. Experimental details The preparation of CuInSe 2 thin films is described in detail in Ref. [7]. Briefly, the CuInSe 2 films were produced by thermal air annealing of stacked elemental layers. Alternate layers of In, Se and Cu were vacuum deposited onto glass substrates by ther- mal evaporation. A quartz thickness monitor (Edwards Model FTM3) was used to control both film thickness and deposition rate inside the vacuum chamber. The thickness of the deposited CuInSe 2 films were measured accurately after deposition by utilizing multiple-beam Fizeau fringes at reflection. The indi- vidual layer thicknesses were generally chosen to be in the ratios 1.0:2.2:4.6 to achieve a 1:1:2 stoichiometric ratios for copper, indium and selenium, respectively. The total thickness of each sandwich was approximately 150 nm, as shown in Fig. 1. The annealing in air was performed at 200, 250, 300 and 400 ◦ C for different times (from 1 to 4 h), to study the effect of annealing on the structure and phases. After annealing, the temperature was decreased gradually to room temperature with 35 ◦ C/min. The XRD analysis was carried out for phase identification of the deposits. This was made by JEOL diffractometer (model JSDX-60PA) with Zr-filter Mo K radiation. Continuous scan- ning was applied with a slow scanning speed and a small time constant. A range of 2θ (from 5 ◦ to 36 ◦ ) was scanned, so that the required diffraction peaks for phase. A comparison with JCPDS file cards was done for the establishing the observed peaks. 0921-5107/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.mseb.2006.07.028