Browsing by Author "Birile, Mesfin (PhD)"

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    Effects of Ga Doping on the Structural Optical and Electronic Properties of Pbs Experimental and Computational Study
    (Addis Ababa University, 2021-10-20) Teshome, Kelemu; Gashaw, Fekadu (PhD); Birile, Mesfin (PhD)
    Experimental and computational methods were employed to study the effects of Ga doping on the structural electronic and optical properties of Pbs. Chemical bath deposition method was used to prepare pure and Ga doped PbS thin films at a bath temperature of 800𝐶 and a pH of 11. The XRD results confirmed that the prepared Ga doped and undoped PbS had a face center crystal structure with a preferential orientation along the (111) plane. The experimental results further revealed that Ga doping had considerable effect on the structural parameters and optical band gap of PbS. In addition, the photoluminescence study verified the material luminescence intensity is dependent on the crystalline size. Density functional theory (DFT) calculations were also performed to study the effect of Ga doping based on General Gradient Approximation. The performance of Perdew-Burke- Ernzerhof (PBE) and bulk solids (PBEsol) exchange-correlation functionals were tested. The lattice constant of pure PbS calculated by PBE and PBEsol functionals were found to be 6.0 Å and 5.913 Å, respectively, while its calculated energy band gap was found to be 0.498 eV for PBE and 0.392 eV for PBEsol. Band structure calculations with PBEsol revealed that PbS is direct band gap semiconductor with its Fermi level lying exactly in between 8.214 eV and 7.822 eV. The incorporations of Ga impurity on PbS molecule were studied systematically with the concentration percentage of 12.5 %, 25 %, 37.5 % and 50 %. We found that the lattice parameters of Ga doped PbS decreased from 5.913 Å to 5.795 Å while, the band gap increased from 0.0354 eV to 0.2579 eV and 0.0411eV to 0.2603 eV calculated by PBEsol and PBE respectively. All the experimental and computational studies verified that Ga doping had a significant effect on the structural and electronic properties of PbS.