Characterization of pulsed laser deposited chalcogenide thin layers T. Petkova a, *, C. Popov b , T. Hineva c , P. Petkov c , G. Socol d , E. Axente d , C.N. Mihailescu d , I.N. Mihailescu d , J.P. Reithmaier b a Institute of Electrochemistry and Energy Systems (IEES), Bulgarian Academy of Sciences, Sofia, Bulgaria b Institute of Nanostructure Technologies and Analytics (INA), University of Kassel, Germany c Laboratory of Thin Film Technology, Department of Physics, University of Chemical Technology and Metallurgy, Sofia, Bulgaria d National Institute for Lasers, Plasma, and Radiation Physics, Bucharest-Magurele, Romania 1. Introduction The chalcogenide glasses have recently focused significant scientific interest for the investigation of their basic properties and the possibility for applications in optics and optoelectronics, electrochemistry, sensor technique, etc. The main attention paid to these materials relies upon their large optical transmission range extending in the mid-infrared and covering usually the two atmospheric windows lying from 3 to 5 mm and from 8 to 12 mm. One can find in literature many reports on the implementation of thin chalcogenide layers in far infrared optics [1,2]. Chalcogenide glasses containing silver or silver salts are well known as super- ionic conducting glasses. Their conduction mechanism as well as their application in solid state electrochemical devices is currently subjects of extensive studies [3]. Till now only few papers have reported on chemical sensors based on chalcogenide glassy materials in the form of membranes [4] or thin films [5,6], but they revealed their potential for application in sensors. As major advantages of these amorphous inorganic materials we emphasize that they can be easily prepared in bulk or layered forms by various methods. They also possess high chemical stability and can easily change properties by small variations in composition due to their disordered amorphous structure. We mention that all these features are common requirements for materials applied in gas sensors. Among the deposition methods used for fabrication of chalco- genide thin films, the vacuum thermal evaporation, DC/RF magne- tron sputtering, and spin-coating technique stand presently for the most common choice [7,8]. However, the deposition of multi- component thin films with a desired degree of stoichiometry, acceptable homogeneity and good adhesion to the substrate still remains a difficult task. One of the most promising and prospective alternatives for preparation of such coatings is pulsed laser deposition (PLD). The proven advantages of PLD are among others: versatility, congruent transfer of target material to deposited films, ultimate purity of synthesised structures due to the use of light pulses for ablation, easy control of the entire process and possibility to deposit complex molecules and multistructures [9,10]. The main goals with the current work were the PLD synthesis of thin films from the system As–Se doped with AgI or Ag and the Applied Surface Science 255 (2009) 5318–5321 ARTICLE INFO Article history: Available online 9 August 2008 Keywords: Chalcogenide thin films Pulsed laser deposition Morphology Nanostructure ABSTRACT In this work we report on pulsed laser deposition (PLD) of chalcogenide thin films from the systems (AsSe) 100x AgI x and (AsSe) 100x Ag x for sensing applications. A KrF* excimer laser (l = 248 nm; t FWHM = 25 ns) was used to ablate the targets that had been prepared from the synthesised chalcogenide materials. The films were deposited in either vacuum (4  10 4 Pa) or argon (5 Pa) on silicon and glass substrates kept at room temperature. The basic properties of the films, including their morphology, topography, structure, and composition were characterised by complementary techniques. Investiga- tions by X-ray diffraction (XRD) confirmed the amorphous nature of the films, as no strong diffraction reflections were found. The film composition was studied by energy dispersive X-ray (EDX) spectroscopy. The morphology of the films investigated by scanning electron microscopy (SEM), revealed a particulate- covered homogeneous surface, typical of PLD. Topographical analyses by atomic force microscopy (AFM) showed that the particulate size was slightly larger in Ar than in vacuum. The uniform surface areas were rather smooth, with root mean square (rms) roughness increasing up to several nanometers with the AgI or Ag doping. Based upon the results from the comprehensive investigation of the basic properties of the chalcogenide films prepared by PLD and their dependence on the process parameters, samples with appropriate sorption properties can be selected for possible applications in cantilever gas sensors. ß 2008 Elsevier B.V. All rights reserved. * Corresponding author. E-mail address: tpetkova@bas.bg (T. Petkova). Contents lists available at ScienceDirect Applied Surface Science journal homepage: www.elsevier.com/locate/apsusc 0169-4332/$ – see front matter ß 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.apsusc.2008.07.194