Optical, morphological and structural characterization of Er3+-Bi3+ co-doped PbS nanocrystals grown by chemical bath

PbS nanocrystals co-doped simultaneously in Er(3+)and Bi3+ solutions were grown and the modification of morphological, structural and some optical properties was investigated. The thicknesses of the undoped and doped PbS films were in the similar to 560-400 nm range. The morphological changes of the nanocrystals were analyzed using Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM) techniques. Fourier transform infrared spectroscopy ((FT-IR)) spectra showed a broad absorption band located at similar to 3500 cm(-1) attributed to stretching of the -OH groups and a sharp band at 1384 cm(-1) owing to stretching vibrations mode of CO32- ions. X-ray diffraction displayed a cubic phase in all films and grain size (GS) of the undoped and doped samples were similar to 33 and similar to 21-17 nm, respectively. The films showed stress, a typical behavior of doped nanocrystals displaying residual strain. The absorbance spectra of PbS film exhibited four absorption bands located at similar to 251 nm (similar to 4.9 eV), 610 nm (similar to 2.0 eV), similar to 668 nm (similar to 1.8 eV) and similar to 830 nm (similar to 1.4 eV) due to strong confinement effect and similar to 446 nm (similar to 2.7 eV), similar to 478 nm (similar to 2.5 eV) corresponding to F-4(7/2) -> I-4(5/2), F-4(3/2)-> I-4(15/2) (f -> f) transitions of Er3+ ions. Sharp bands were found at similar to 287 nm (similar to 43 eV) and 366 nm (similar to 3.38 eV), corresponding to transitions of Bi3+ ions. The band gap energy of films showed a shift in the similar to 0.9-1.2 eV range. Raman spectra showed two bands located at similar to 450 cm(-1) due to the first overtone of the longitudinal optical (LO) phonon (2LO) and a band observed at similar to 200 cm(-1) which was attributed to the LO (Gamma) phonon. A kinetic mechanism using the free energy changes Gibbs is proposed. (C) 2018 Elsevier GmbH. All rights reserved.