Structure Investigation of Cadmium Sulfide and Cadmium Selenide Nanocrystals Deposited by Chemical Bath Deposition Technique

Cadmium compounds, including cadmium sulfide (CdS) and cadmium selenide (CdSe) are semiconductor materials and have been widely used in many fields due to their unusual optical and electronic properties. The quantum dots of these materials have received considerable attention because of their tunable band gaps, which can vary their optical response from the infrared to the ultraviolet ranges. The bandgaps of CdS and CdSe quantum dots can be tailored from 2.6 – 1.85 eV and 2.42 eV - 1.71 eV, respectively. We use the chemical bath deposition technique to deposit CdS and CdSe thin film on glass substrates. In order to deposit CdS thin films, we use cadmium sulfate (CdSO₄), ammonia water (NH₄OH) and thiourea (CS(NH₂)₂) as reaction agents. For CdSe thin films, we use cadmium acetate as cadmium ion source and sodium selenosulfate / thiourea as a selenium / sulfur ion sources. Aqueous ammonia is used as a complex reagent and also to adjust the pH of the final solution. The as-deposited thin films using this technique are optically transparent, adherent, homogeneous and yellowish for CdS and redish for CdSe without powdered precipitation.