The investigation of the annealing temperature for CdS cauliflower-like thin films grown by using CBD Gamze Comert Ozcan 1 • Hulya Metin Gubur 1,2 • Soner Alpdogan 2 • Birsen Kesik Zeyrek 3,4 Received: 5 April 2016 / Accepted: 12 July 2016 Ó Springer Science+Business Media New York 2016 Abstract The Cadmium Sulfide (CdS) cauliflower-like thin films were prepared on glass substrates by using chemical bath deposition at 80 °C. The films were annealed at dif- ferent temperatures (373, 473, 573, 673 and 773 K) for 1 h at ambient air. The XRD results showed that these films were both in cubic and hexagonal structure and there was no structural alteration among films at different annealing temperatures. The SEM images depicted that the as-de- posited film and the film annealed at 373 K had a conifer-like structure; at higher annealing temperatures, the conifer-like structures combined and formed cauliflower-like structures. Also, it was found that the optical band gap decreased from 2.42 to 2.39 eV, with the increase of annealing temperature. The electrical measurements (resistivity, carrier concentra- tion and mobility) of the CdS films were carried out by means of Hall Effect at room temperatures. 1 Introduction Solar energy, as a renewable energy, has gained a lot of attention due to the decrease of the conventional energy resources. In this context, researchers have concentrated their efforts on improving the efficiency of the solar cells [1–10]. The most important of solar cells, thin-film CdS/ CdTe solar cells are greatly studied by many researchers owing to the fact that they are low cost, energy efficient, suitable for mass production because of flexible cells and modules. Besides, the CdS, CdTe semiconductor thin films (the group of II–VI compounds), because of their control- lable sizes, shapes and crystallization, have been used in electronic, optical, catalysis, biology and magnetism devices [11–14]. In recent years, the nanoscaled semicon- ductors are produced with various structures, such as the nanowires, nanorods, nanotubes, flower-like nanorings and cauliflower-like microspheres. CdS semiconductor, one of the most important group of II–VI compounds, has a direct band gap of 2.42 eV and, have been fabricated by several methods such as vacuum evaporation [15], chemical vapour deposition [16], molecular beam epitaxy [17], successive ionic layer adsorption and reaction method (SILAR) [18], sputtering [19], electrodeposition [20] and chemical bath deposition [21–27]. Among these techniques, CBD has been exces- sively used by many researchers for the CdS semiconductor because it is simple and inexpensive to control the growth rate, is uniform and adherent for crystal structures. Dif- ferent morphologies of CdS semiconductor have been prepared to nanorods [28], flower-like nanorings [12], conifer-like [29], cauliflower-like microspheres [30], nanowires [31], flakes [32], and flowers [33]. CdS semi- conductor is used in a common junction partner layer material for CdS/CdTe solar cell structures, and also in electronic, optic and biological devices [34–42]. In this work, the change of the structural, morphologic, optical and electrical properties with annealing at different temperatures will be presented. We will discuss these changes as much as possible. & Hulya Metin Gubur hulmetin@gmail.com 1 Advanced Technology Research and Application Center, Mersin University, 33343 Yenisehir, Mersin, Turkey 2 Department of Physics, Mersin University, 33343 Yenisehir, Mersin, Turkey 3 Department of Physics, Cukurova University, Balcali, 01330 Saricam, Adana, Turkey 4 Program of Opticianry, Vocational School, Toros University, Bahcelievler Campus, 33140 Yenisehir, Mersin, Turkey 123 J Mater Sci: Mater Electron DOI 10.1007/s10854-016-5368-6