Synthesis of Cds with large band gap values by a simple route at room temperature

We report the synthesis of CdS polycrystalline thin films deposited with 0%, 0.88%, 1.78%, 2.58%, and 3.40% (volume fraction, φ) O₂ in sputtering Ar gas using a radio frequency magnetron sputtering method. The obtained CdS samples were characterized by X-ray diffraction, scanning electron microscope, Raman spectroscopy, ultraviolet-visible (UV-Vis) absorption spectroscopy, and X-ray photoelectron spectroscopy. O incorporation led to the formation of compact and small CdS grains. The band gap values of the CdS thin films deposited with 0.88%and 1.78% O₂ were 2.60 and 2.65 eV, respectively, and were larger than that of CdS (2.48 eV) deposited without O₂ gas in sputtering Ar gas. In contrast, the band gap values of the CdS thin films deposited with 2.58% and 3.40% O₂ (2.50 and 2.49 eV, respectively) were consistent with that of CdS (2.48 eV) deposited without O₂ gas in sputtering Ar+O₂ gas. The CdS thin film deposited with 0.88% O₂ displayed the highest crystalline quality. Subsequently, CdTe thin films were deposited by radio frequency magnetron sputtering method on the surface of the CdS thin films. The CdTe thin films were characterized before and after high-temperature anneal treatment in a CdCl₂ atmosphere. The results showed that O incorporation into CdS led to the formation of considerably more closely packed and larger CdTe grains. The synthesis of CdS with large band gap values at room temperature is facile and effective using the current method. Therefore, the method presented herein is very promising for large-scale industrial production.