Colloidal indium arsenide and indium phosphide quantum wires and rods: Synthesis, quantum-confinement effects, and electrical-transport properties

A primary goal of this work is the growth of diameter-controlled InAs and InP quantum wires, and diameter- and length-controlled InAs and InP quantum rods employing the solution-liquid-solid (SLS) mechanism. The fulfillment of this goal enables us to systematically study the quantum-confinement effects of these quantum nanostructures, and the electrical-transport property of InAs quantum wires.;Soluble, narrowly dispersed InAs and InP quantum wires and rods are grown from Bi nanoparticles in the presence of conventional quantum-dot surfactants by employing indium (III) myristate as the indium precursor. The diameters of the wires and rods are mainly determined by the diameters of Bi nanoparticles used, whereas the lengths of the rods are determined by the reaction time. The quality of the wires and rods is dramatically affected by the surfactants employed. The selection of appropriate surfactants is described, as is the synthesis of near-monodispersed Bi nanoparticles with a variety of diameters.;The band-gap energies of these quantum nanostructures are determined from the absorption and/or photoluminescence spectra, and compared to these for the best-quality quantum dots, and to the relevant theoretical predictions. We demonstrate experimentally that the quantum-confinement effect in 2D-confined wires is weakened to the expected extent, relative to the 3D-confined dots, by the loss of one confinement dimension, consistent with high-level theoretical calculations. Quantum rods constitute an intermediate case to dots and wires and we experimentally determine that the InP quantum rods become quantum wires at a length of ≈ 25 nm, about two times the exciton Bohr radius of bulk InP (∼ 11 nm).;As-prepared InAs quantum wires show room-temperature photoluminescence, whereas as-prepared InP quantum wires and rods do not. HF-photochemical etching of the InP rods produces photoluminescence that is further enhanced after the Bi tips are selectively removed. Photochemical etching of the InP wires elicits photoluminescence from the wire samples. However, the InP wires are photo-oxidized, affording amorphous indium phosphate wires with embedded dot- and rod-like domains of crystalline (residual) InP. The emission observed is produced by the embedded InP dots and rods.;The undoped InAs nanowires show only electron (n)-channel conduction with high electron mobility before surface-ligand passivation, but also weak hole (p)-channel conduction and improved electron mobility after the wires become ligands passivated. The Cd-doped InAs wires show more symmetrical ambipolar (both n- and p-channel conduction) characteristics, but only n-channel conduction after the surface ligands are removed by oxygen plasma. The carrier mobilities are low in these doped wires.