title: Controlled electrostatic assembly of quantum dots vis-à-vis their electronic coupling and transport gap.
abstract: We correlate the electronic coupling between quantum dots and the transport gap of nanoparticle-passivated Si substrates. We vary the length of the stabilizers of CdS nanoparticles, which in turn alters the particle-to-particle separation and hence the electronic coupling between them. We also control the electronic coupling using time-restricted electrostatic-assembly of quantum dots, using short periods of time so that an incomplete monolayer or a sub-monolayer of CdS forms. In such a sub-monolayer, the nanoparticles remain isolated from each other with a controllable particle-to-particle separation. From electronic absorption spectroscopy of multilayer films and atomic force microscopy of a monolayer, we evidenced sub-monolayer formation in the controlled electrostatic assembly process. We measure the current-voltage characteristics of nanoparticle-passivated substrates with a scanning tunnelling microscope; we show that the transport gap of nanoparticle-passivated substrates depends on the electronic coupling between CdS particles in the monolayer.
authors.affiliation: Indian Association for the Cultivation of Science, Department of Solid State Physics, Jadavpur, Kolkata 700032, India.
authors.forename: Batu
authors.initials: B
authors.lastname: Ghosh
authors.forename: Amlan J
authors.initials: AJ
authors.lastname: Pal