Preparation and characterization of post-doped nano-structured Cul:l thin films

The undoped and iodine doped CuI thin films with diffirent doping concentration were synthesized by using mister atomizer technique. The CuI solutions were prepared using CuI powder with acetonitrile as a solvent. The quantity of iodine was varied with 10, 20, 30, 40 and 50 mg. The results are observed on the properties of surface morphology, electrical and optical. The surface morphology characterized by FESEM revealed that the microstructure of CuI films depended on the relative amount of doping iodine in the solution. The surface morphology in the presence of iodine was closely packed spherical CuI grains. The surface morphology of undoped CuI thin films was found in larger faceted grains with a uniform distribution meanwhile the grain sizes for doped CuI thin films was found to be decreased. The resistivity of about 10³ Ω cm¯¹ is observed in 40 and 50 mg CuI thin films. The optical transmittance was found to be in range 0.2% to 2.4% at various doping concentration. The result indicates that all CuI films exhibit low transmittance in the visible region than in the near infra- red region. The optical band gap was recorded between 2.14 eV to 2.96 eV at various doping concentration. The optical band gap for undoped CuI thin films was found to be at 2.92 eV which is less than the reported band gap by the literature which is 3.1 eV. However, at 40 mg of iodine gives the best value which is 2.14eV less than the undoped CuI thin films. The PL intensity peaks was observed at 420 nm, between 680 to 685 nm and between 835 to 840 nm. The nature of the photoluminescence is discussed and it may be due to the recombination that occurs from the excess of iodine.