Semiconductor to metal transition in PbS nanowires grown in mica channels

Abstract

It has been possible to grow PbS nanowires of diameter 1.2 nm within the crystal channels of Na-4 Mica. These nanowires exhibit a semiconductor to metal transition at ~300 K as the temperature is lowered. Generation of pressure around 3 GPa on these wires due to a thermal expansion mismatch of Na-4 Mica and PbS phases is believed to cause this transition. A nonlinear voltage current characteristics at different temperatures is ascribed to the formation of nanojunctions between the metallic phases and not transformed PbS regions. The semiconductor-metal transition at 300 K is accompanied by a transition from a low to a high dielectric constant. The large value of dielectric constant shown by the nanocomposites is explained as arising due to the Rice-Bernasconi mechanism of dielectric polarizability in broken one-dimensional conductors.