Growth and characterization of bimetallic (Ni,Co) sulfide thin films deposited by spray pyrolysis

In this work, the bimetallic (Ni,Co) sulfide film of 852.213 nm thickness was successfully deposited using the spray pyrolysis technique at 300 °C. The compound was prepared with a mixture of nickel acetate (C4H6O4Ni. 4H2O), cobalt chloride (CoCl2. 6H2O), and thiourea (CS(NH2)2) as precursors for Ni, Co, and S, respectively. The temperature and sedimentation time were 300 °C and 10 min, respectively; the film was then, characterized without any thermal post-treatment. The structural, morphological, optical and electrical analysis were carried out to investigate the different properties of the material. The X-ray diffraction analysis confirmed the presence of NiCo2S4 according to the JCPDS Card # 98- 004-0019, with an average crystallite size of 34.45 nm. The optical analysis revealed the metallic behavior of the film with an average transmittance of 3.41% in the visible region and a direct optical band gap of 2.15 eV, as well as a high absorption coefficient of α ≈ 104 - 105 cm-1 ). The elementary composition analysis (EDS) confirmed the presence of Ni, Co and S elements in the film. Morphological analysis revealed a homogeneous, compact, crack-free appearance and a granular surface in all studied areas. On the other hand, the film shows a high electrical conductivity of about 1.42×105 S/cm at room temperature. The obtained results show that the bimetallic (Ni, Co) sulfide prepared in this study exhibits a good crystallinity, dense morphology, good stoichiometric ratio and high conductivity. Therefore, it is a potential candidate for application in supercapacitors as electrode material.