Influences of anionic and cationic dopants on the morphology and optical properties of PbS nanostructures

Selenium and zinc are used as anionic and cationic dopant elements to dope PbS nanostructures. The undoped and doped PbS nanostructures are grown using a thermal evaporation method. Scanning electron microscopy (SEM) results show similar morphologies for the undoped and doped PbS nanostructures. X-ray diffraction (XRD) patterns of three sets of the nanostructures indicate that these nanostructures each have a PbS structure with a cubic phase. Evidence of dopant incorporation is demonstrated by X-ray photoelectron spectroscopy (XPS). Raman spectra of the synthesized samples confirm the XRD results and indicate five Raman active modes, which relate to the PbS cubic phase for all the nanostructures. Room temperature photoluminescence (PL) and UV-Vis spectrometers are used to study optical properties of the undoped and doped PbS nanostructures. Optical characterization shows that emission and absorption peaks are in the infrared (IR) region of the electromagnetic spectrum for all PbS nanostructures. In addition, the optical studies of the doped PbS nanostructures reveal that the band gap of the Se-doped PbS is smaller, and the band gap of the Zn-doped PbS is bigger than the band gap of the undoped PbS nanostructures.