Abstract
We have fabricated small PbS nanocrystals (cubes: 21 nm; octahedra: 57 nm) in aqueous solution using an one-step approach. We gain knowledge in manipulating their shape and size by clear exploration of the relation between nucleation and crystal growth. This enables us to scale up the production using a more intuitive method. Also, the refined seeding growth method allows us to enlarge the size of PbS polyhedra, fulfilling single particle electrical conductivity measurements. Facet-dependent electrical conductivity of Cu2O crystals has been previously revealed. In this study, we have again successfully demonstrated the facet-dependent electrical property of PbS using face-raised cubes, edge-and corner-truncated cubes, edge- and corner-truncated octahedra and pristine octahedra with the size of several hundreds of nanometers. Two tungsten probes are manipulated to contact the opposite faces of a single particle. The {110} facets showed the highest electrical conductivity, followed by the {100} facets and the {111} facets were observed to be the least conductive. The {111} facets are 500 times less conductive than the {110} faces at an applied voltage of 5 V. This study suggests that facet-dependent electrical conductivity should be regarded as an intrinsic property for semiconductors.