Structural and optical properties of undoped and Sb-doped lead oxide thin films synthesized via the chemical bath deposition method

Abstract

Undoped PbO thin films and various concentrations of Sb ranging from 1 to 9 at% were prepared on borosilicate glass substrates by a chemical bath deposition method. The structural characteristics detected were amorphous, owing to the trend of glass formability based on a small amount of Sb in the PbO thin film. The mixed phases of tetragonal (α-PbO) and orthorhombic (β-PbO) were clearly observed at the 3, 5, 7, and 9 at% Sb concentrations. A significantly higher value in average root-mean-square (RMS) roughness was revealed for various Sb-treated PbO thin films. The highest average RMS roughness for the 7 at% Sb-doped PbO thin film was obtained due to the largest nucleation and coalescence process of the nanoparticles. The average Eg can be estimated to be 2.49, 2.58, 2.34, 2.46, 2.46, and 2.19 eV for 0, 1, 3, 5, 7, and 9 at% Sb-doped PbO thin films, respectively. This change or fluctuation in average Eg can be explained from the disorder in the thin films and is correlated with the growth of PbO nanostructures. The optical constants, dielectric constants, and dielectric loss functions were derived from the extinction coefficient (k), and refractive index (n). The highest linear susceptibility (χ(1)), nonlinear susceptibility (χ(3)), and nonlinear refractive index (n2) values in the low wavelength region (300–700 nm) and the high wavelength region (700–1100 nm) were respectively obtained for the undoped PbO and the 7 at% Sb-doped PbO thin film. These have important and promising implications for optical devices in the wavelength range from UV to NIR. Finally, the calculated Egs, with the Perdew-Burke-Ernzerhof (PBE) function, are 1.79 eV and 2.44 eV for the undoped α and β phases, while the Egs of the Sb-doped α and β phases are reduced to 1.61 eV and 2.10 eV, respectively.