Metallic conduction in NiS₂ nanocrystalline structures

Abstract

Thermolysis of Ni butanethiolate in a sulfur atmosphere has been carried out at 300 and 600 °C to produce NiS₂ nanocrystalline films with mean crystallite sizes of 16 and 192 nm and resistivity values of ∼451 and 3540 μΩ·m, respectively; the resistivity values are ∼2 orders of magnitude less compared to the bulk value (12000 μΩ·m). This is a significant observation since NiS₂ is an insulator in the bulk. Combining electrostatic force microscopy, transport, and surface degradation experiments, we establish conclusively that the surface layer of NiS₂ is metallic. The density of the surface conduction states computed through the variable range hopping model is found to be comparable to the bulk density of states of good metals. The precursor is also amenable for patterning by electron beam and molding.