Fullerene-Like (IF) Nb<i>_x</i>Mo₁_-<i>_x</i>S₂ Nanoparticles

Abstract

IF-Mo₁_-<i>_x</i>Nb<i>_x</i>S₂ nanoparticles have been synthesized by a vapor-phase reaction involving the\nrespective metal halides with H₂S. The IF-Mo₁_-<i>_x</i>Nb<i>_x</i>S₂ nanoparticles, containing up to 25% Nb, were\ncharacterized by a variety of experimental techniques. Analysis of the powder X-ray powder diffraction,\nX-ray photoelectron spectroscopy, and different electron microscopy techniques shows that the majority of\nthe Nb atoms are organized as nanosheets of NbS₂ within the MoS₂ host lattice. Most of the remaining Nb\natoms (3%) are interspersed individually and randomly in the MoS₂ host lattice. Very few Nb atoms, if any,\nare intercalated between the MoS₂ layers. A sub-nanometer film of niobium oxide seems to encoat the\nmajority of the nanoparticles. X-ray photoelectron spectroscopy in the chemically resolved electrical\nmeasurement mode (CREM) and scanning probe microscopy measurements of individual nanoparticles\nshow that the mixed IF nanoparticles are metallic independent of the substitution pattern of the Nb atoms\nin the lattice of MoS₂ (whereas unsubstituted IF-MoS₂ nanoparticles are semiconducting). Furthermore the\nIF-Mo₁_-<i>_x</i>Nb<i>_x</i>S₂ nanoparticles are found to exhibit interesting single electron tunneling effects at low\ntemperatures.