Effects of different deposition conditions on the properties of Cu₂S thin films

Abstract

Cu₂S thin films deposited on glass substrate by chemical bath deposition were studied at different deposition temperatures and times. The results of X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray analysis (EDX), the Hall Effect measurement system and UV-Vis absorption spectroscopy indicate that both deposition temperature and time are important to obtain polycrystalline thin films. XRD showed that the polycrystalline Cu₂S thin films have monoclinic structure. Meanwhile, the structural variations were analyzed using SEM. EDX analysis results of the thin film showed that the atomic ratio of Cu/S was close to 2:1. It was found from the Hall Effect measurement that the resistivity varied from 4.59 × 10⁻³ to 13.8 × 10⁻³ (Ω cm). The mobility values of the Cu₂S thin films having p-type conductivity varied from 15.16 to 134.6 cm²/V.s. The dark electrical resistivity measurements were studied at temperatures in the range 303–423 K. The electrical activation energies of Cu₂S thin films were calculated by using Arrhenius plots, from which two different activation energy values are estimated for each thin film. Using UV-Vis absorption spectroscopy (Ultraviolet/visible), the direct and indirect allowed optical band gap values were determined to lie between 2.16 and 2.37 eV and 1.79 and 1.99 eV, respectively. In addition, the values of the refractive index (n) and the extinction coefficient (k) were determined.

Keywords:

• Cu₂S
• thin film
• deposition conditions
• chemical bath deposition

PACS:

• 68.37.-d
• 61.05.cp
• 73.61.-r
• 78.20.-e