ISSN 10274510, Journal of Surface Investigation. Xray, Synchrotron and Neutron Techniques, 2013, Vol. 7, No. 6, pp. 1270–1276. © Pleiades Publishing, Ltd., 2013. 1270 INTRODUCTION Cadmium sulfide with a band gap of 2.42 eV is employed as optical windows in creating heteroge neous thinfilm photocells based on CdTe and Cu(In, Ga)Se 2 [1]. In practice, when CdS nanoparti cles grow along the normal to a transparent substrate surface, it is possible to ensure the excellent properties of solar cells and luminescent diodes due to efficient charge transfer to electrodes. Solar cells with a set of ordered cadmium sulfide particles are characterized by a large area of the donor–acceptor interface and the minimum charge transfer length, which offer their advantage over bilayer structures [2]. Cadmium sulfide nanoparticle growth has been investigated compre hensively by means of different methods in [3–12]. In this work, the surface morphologies of cadmium sul fide films created via the electrochemical and chemi cal deposition methods are compared to reveal their features. EXPERIMENTAL Thin cadmium sulfide films were prepared by means of electrochemical or chemical deposition from different electrolytes onto glass coated with a conducting SnO 2 + In 2 O 3 film known as indiumtin oxide (ITO) film. This layer has a sufficiently low elec tric resistance (15 Ω/cm). After deposition, films were annealed in air at T = 400°C for 20 min. The film thickness was 500 ± 50 nm. Electrodeposition was per formed from aqueous electrolytic solutions with the help of the technique described in [7]. A chemical deposition process was implemented by means of the technique [9–11] having two variants: (i) Single chemical deposition from a solution on transparent conducting glass/ITO substrates [9, 10]. (ii) Successive deposition of several layers on pure glass by submersion into a chemical bath [11]. The surface morphology of CdS films was studied via atomicforce microscopy (AFM) in a JSPM5200 microscope under semicontact conditions with the use of an NSC 35/AIBS cantilever with a curvature radius of ≤10 nm. Scanning was carried out at atmospheric pressure and room temperature. Investigations were partially performed using an NT–MDT atomicforce microscope and a Quanta 3D 200 scanning electron microscope (with crosssec tion imaging). The film transmission spectra were measured at wavelengths 0.19–3.00 μm with the help of a Varian Cary500 Scan spectrophotometer (United States) and an UV1 Helios Alpha instrument. The film absorption edge was estimated from absorption spectra. For this purpose, the multiple layerbylayer growth of CdS films was carried out to select the resulting thickness of coatings at which their optical density D = αh (in the absorption edge region) was in the range of 0.1–0.8 (i.e., from 80 to 17% of transmis sion), being optimal for decreasing the relative error of the determination of the optical density and absorp tion coefficient. RESULTS AND DISCUSSION Surface Morphology Electrodeposited thin CdS films were synthesized using an electrolyte containing 0.30 M CdCl 2 and 0.03 M (Na) 2 S 2 O 3 on glass coated with a conducting ITO film [7]. The film thickness was 500 ± 50 nm. Electron Microscopic Study of Thin CdS Films M. B. Dergacheva a , K. A. Mit’ b , K. A. Urazov c , and V. F. Gremenok d a Sokolsky Institute of Organic Catalysis and Electrochemistry, Almaty, Kazakhstan b Physicotechnical Institute, Almaty, Kazakhstan c KazakhBritish Technical University, Almaty, Kazakhstan d Scientific and Practical Materials Research Center, National Academy of Sciences of Belarus, Minsk, Belarus Received April 17, 2013 Abstract—The results obtained by investigating the surface morphology and optical properties of thin CdS films formed on transparent glass and glass/indiumtin oxide (ITO) substrates via the chemical and electro chemical methods are presented. Thin cadmium sulfide films are employed as optical windows in thinfilm polycrystalline solar cells. Closely packed cadmium sulfide nanoparticles are observed on the conducting oxide (ITO) surface by means of atomicforce microscopy. Large particles (150–300 nm) comprise smaller particles with sizes of 20–30 nm. Thin CdS layers are characterized by a relatively high level of transmission (~60%) in the longwavelength spectral region (520–600 nm). DOI: 10.1134/S1027451013130053