Heterovalent substitution in anionic and cationic positions of PbS thin-films grown by SILAR method vis-a-vis Fermi energy measured through scanning tunneling spectroscopy

We report the growth and characterization of doped-PbS thin-films deposited by a successive ionic layer adsorption and reaction (SILAR) method. Altervalent cation and aliovalent anion substitution by ions of mono-and trivalent elements as dopants have been achieved in the compound semiconductor. The heterovalent elements introduced free carriers into the semiconductors, the nature of which depended on its valency and the ions it substituted into the compound. The effect of such dopants on the Fermi energy of PbS has been followed by scanning tunneling spectroscopy (STS), and was found to have correspondence to the density of states (DOS) of a semiconductor. By locating the conduction and valence band-edges of the pristine and different doped-semiconductors, the STS studies provided a direct evidence of a shift in Fermi energy upon heterovalent cationic and anionic substitution in compound semiconductors.