Properties of lead-sulfide nanoparticles in a multicrystalline structure

The structural and electrical properties of PbS nanoparticles (40–70 nm), produced by a chemical reaction of sodium hydroxide with lead nitrate and electrophoretically deposited onto a conductive substrate, are investigated. The composition and structure of the nanoparticles are identified by X-ray analysis as pure PbS phase with a face-centered cubic lattice. Several minima, related to plasma-resonance absorption at 10–17 $\mu$m, are observed in the frustrated total internal reflection (FTIR) spectra. The layer morphology and the nanoparticle shape and sizes are determined by scanning electron and tunneling microscopy. The threedimensional topograms show that the surface fine structure is a set of faceted pyramidal spikes with a size of 5–10 nm and a density of $\sim$400 $\mu$m$^{-2}$. An analysis of the tunneling current–voltage characteristics of individual nanospikes shows the presence of low-field emission and makes it possible to determine the barrier heights (1.6–1.8 eV), which are explained within the quantum-dot (QD) model.