Effects of annealing on structural and morphological properties of e-beam evaporated AgGaSe 2 thin films H. Karaagac, M. Parlak * Department of Physics, Middle East Technical University, 06531 Ankara, Turkey 1. Introduction I–III–VI 2 chalcopyrite compounds regarded as the ternary analogs of II–VI zinc-blende semiconductors have received considerable attention due to their interesting electrical, optical, and structural properties. Because of these properties such kind of materials have been used in many areas for specific applications like visible and infrared light emitting diodes, infrared detectors, optical parametric oscillators, up converters, and solar cells [1–3]. Specifically, due to their flexible optical properties and good stabilities, they are promising compounds for photovoltaic devices [1]. Particularly, on account of their suitability in field of solar cells and non-linear optics, AgGaSe 2 is an attractive material studied extensively by many researchers. It is found that AgGaSe 2 has high optical non-linear coefficient and wide transparency range between 0.7 and 17 mm [4]. In addition, studies on AgGaSe 2 showed that it is a good candidate for frequency-doubling the output of CO 2 laser [5]. Furthermore, it is convenient for radiation detector applications with its band gap value of 1.8 eV at room temperature [6]. So far; many techniques have been reported for the production of I–III–VI 2 chalcopyrite compounds in the form of both single crystal and thin film. For the single crystal, the Bridgman-Stockbarger is the most extensively preferred technique [7]. On the other hand, for the fabrication of these compounds in thin film form, various techniques are used like flash evaporation [8], thermal evaporation [9], electron-beam technique [10], pulsed laser deposition [11], and hot-press deposition [12]. In this study, our aim is to investigate the structural and morphological properties of AgGaSe 2 thin films deposited using the synthesized single crystal powder of AgGaSe 2 by electron-beam technique. For that, XRD, SEM, and XPS measurements were carried out to deduce the general behaviors of this ternary compound in thin film form. 2. Experimental details The AgGaSe 2 single crystals have been synthesized by preparing stoichiometric mixture of constituent elements of pure indium, gallium and selenium sealed into an evacuated quartz ampoule and sintered at 1050 8C for 48 h. Having synthesized the growth ampoule, a Crstalox MSD-4000 model three zone vertical Bridg- man-Stockbarger system was used for getting the single crystalline AgGaSe 2 compound. For that, a special temperature profile was used. The settings of each zone were 1050, 850, and 600 8C for top, middle and bottom zones, respectively. After 105 h of translation Applied Surface Science 255 (2009) 5999–6006 ARTICLE INFO Article history: Received 6 October 2008 Received in revised form 7 December 2008 Accepted 19 January 2009 Available online 11 February 2009 Keywords: Chalcopyrite compounds AgGaSe 2 X-ray diffraction Scanning electron microscopy X-ray photoelectron spectroscopy ABSTRACT Polycrystalline AgGaSe 2 thin films were deposited by using single crystalline powder of AgGaSe 2 grown by vertical Bridgman-Stockbarger technique. Post-annealing effect on the structural and morphological properties of the deposited films were studied by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDXA) measurements. XRD analysis showed that as-grown films were in amorphous structure, whereas annealing between 300 and 600 8C resulted in polycrystalline structure. At low annealing temperature, they were composed of Ag, Ga 2 Se 3 , GaSe, and AgGaSe 2 phases but with increasing annealing temperature AgGaSe 2 was becoming the dominant phase. In the as-grown form, the film surface had large agglomerations of Ag as determined by EDXA analysis and they disappeared because of the triggered segregation of constituent elements with increasing annealing temperature. Detail analyses of chemical composition and bonding nature of the films were carried out by XPS survey. The phases of AgO, Ag, Ag 2 Se, AgGaSe 2 , Ga, Ga 2 O 3 , Ga 2 Se 3 , Se and SeO 2 were identified at the surface (or near the surface) of AgGaSe 2 thin films depending on the annealing temperature, and considerable changes in the phases were observed. ß 2009 Elsevier B.V. All rights reserved. * Corresponding author. E-mail address: parlak@metu.edu.tr (M. Parlak). Contents lists available at ScienceDirect Applied Surface Science journal homepage: www.elsevier.com/locate/apsusc 0169-4332/$ – see front matter ß 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.apsusc.2009.01.054