Growth of Er3+-doped PbS nanocrystals by chemical bath

The growth of Er3+-doped PbS thin films and the changes of structural, morphological, electrical and some optical properties were examined. The thicknesses of these films were found in the ∼200-120 nm range. The morphological properties of the nanocrystals were analyzed using Atomic Force Microscopy (AFM). FTIR spectra showed strong sharp absorption located at ∼1447 cm−1 associated with the asymmetric stretching vibrations assigned to the bending out-plane vibrations of CO32− ions. X-ray diffraction displayed a cubic phase in all films and grain size (GS) was ∼6.5 nm for PbS, whereas for doped nanocrystals was ∼5.1 nm. Absorption bands located at ∼371 nm (∼3.3 eV), ∼385 nm (∼3.2 eV), 406 nm (∼3.0 eV), ∼608 nm (∼2.0 eV), ∼619 nm (∼2.03 eV), ∼640 nm (∼1.9 eV), and another intense band located at ∼682 nm (∼1.8 eV) were observed. An optical absorption band located at ∼371 nm (∼3.3 eV) was observed in doped films, corresponding to 4f → 4f transitions of Er3+ ions. The band gap energy of films showed a shift in the ∼1.49 eV for PbS and ∼2.25-2.58 eV for doped samples, respectively. The resistivity increased from ∼0.65 to 8.57 × 103 (Ω cm)−1, and the electrical conductivity decreases from ∼1.52 to 0.001 Ω m, mobility decreased from ∼29.6 to 0.13 cm2/Vs, and carrier increases from ∼1.9 × 1015 to 7.0 × 1015 cm−3, while increasing V[Er3+]. As expected, doped samples showed better photosensitivity.