IOSR Journal of Electronics and Communication Engineering (IOSR-JECE) e-ISSN: 2278-2834,p- ISSN: 2278-8735.Volume 10, Issue 5, Ver. II (Sep - Oct .2015), PP 19-24 www.iosrjournals.org DOI: 10.9790/2834-10521924 www.iosrjournals.org 19 | Page Annealing Effects and Film Thickness Dependence of Cobalt Selenide Thin Films Grown By the Chemical Bath Deposition Method R.A. Chikwenze 1 , P.A. Nwofe 2 , P.E. Agbo 2 , D. A. Famuyibo 2 , A.E. Umahi 2 , S.O. Ngele 3 , S.P.I. Ogah 3 1 Department of Physics, Faculty of Science & Technology, Federal University, Ndufu-Alike, Ikwo , Nigeria 2 Department of Industrial Physics, Ebonyi State University, P.M.B 53, Abakaliki, Nigeria 3 Department of Industrial Chemistry, Ebonyi State University, P.M.B 53, Abakaliki, Nigeria Abstract : Thin films of CoSe (cobalt selenide) were prepared using the chemical bath deposition technique. The deposition variables such as the pH, bath temperature, and source to substrate distance were kept constant and the film thickness was varied by varying the concentrations. The films were then annealed at annealing temperatures ≤ 250 o C. The films were characterised using scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDAX), and X-ray Diffractometry (XRD) to investigate the morphological, compositional and structural properties of the as-deposited and annealed layers. The results show that the post- deposition annealing improved the properties of the layers. In particular, an increase in the grain size was recorded for annealing temperatures ≤ 200 o C. Keywords:– Annealing, Chemical bath deposition, Film thickness, Grain size, Thin films I. Introduction The use of different selenides in thin film form for applications in different electronic, optoelectronics and in nanotechnology industry has been widely reported in the literature. In recent times, interest in the chalcogenides of semiconductors, metals and transition metals have increased tremendously because of their tunable properties which makes them useful candidates in various electronics and optoelectronic devices including solar cells, sensor, laser materials, photoconductors, diodes and transistors [1-15]. It is generally understood that chemical techniques for the preparation of semiconducting chalcogenides thin films offer the advantages of economy, convenience and the capability of large-area deposition. Thin film deposition of chalcogenides of nickel, bismuth, antimony, cadmium, copper, zinc tin, and indium selenides have been reported by various research groups [16-25]. Most recently, cobalt selenides is reported to be used as high performance counter electrodes in dye sensitized solar cells [26-27], as catalysts [28], waste water treatments [29], photoelectrodes [30-32], and magnetic devices [33]. It has been established in the literature by different research groups that thin films of cobalt selenides can be grown using different low cost deposition techniques. These deposition methods include chemical bath deposition technique [34-35], electro-deposition [30-32, 36-38], solvothermal synthesis [29], and chemical synthesis [39-41]. Chemical bath deposition is a cost effective technique that yield high quality thin films and the basic principles is mostly by the controlled precipitation of the desired compound from a solution of its constituents. In the present investigation, the deposition of cobalt selenides thin films grown by chemical bath deposition at room temperature is reported, with emphasis on the influence of the different annealing temperatures on the morphological compositional and structural properties of the films. The effect of the deposition conditions and post deposition annealing on the film thickness is also presented. This report is a fundamental step in determining the optimised conditions needed for increased efficiency of cobalt selenides thin films especially when utilised in electronic devices such as solar cells, diodes, and transistors. II. Materials And Method The glass microslides used as substrates were initially soaked in dilute hydrochloric acid for 2 hours, removed and dipped into acetone for 1 hour after which they were removed, washed with foam- sponge in ethanol and finally rinsed in distilled water. They were then dried in oven at 30 o C above room temperature for 30 minutes. Before deposition of films on them, the substrates were brought out of the oven and their temperature allowed to drop to room temperature. Pre-cleaned glass substrates were then inserted vertically into the growth mixtures using synthetic foam. The loaded substrates were labelled for easy identification. The deposition time was fixed for 4 h at a constant temperature of 60 o C. The films were removed and rinsed with distilled water and then dried in air. The films were then annealed in an oven with the annealing temperatures kept between the range of 100 o C to 250 o C with the annealing time fixed for 1 hour.