Localized annealing: a step toward post-growth, site-controlled quantum dots in III-V semiconductor nanowires

The project involves the investigation of filamentary crystals, in particular III-V semiconductor nanowires, and the change in bandgap energy induced by hydrogenation and localized annealing, with the purpose of producing localized quantum dots along the wires. This can be achieved by exposing a wire to ionized hydrogen irradiation, which increase the energy bandgap, and by exploiting the plasmonic properties of suitably shaped metallic nanoparticles, which we can move on the desired spot along the wires. Indeed, the strong enhancement of the electromagnetic field of a laser induced by the metal nanoparticle will locally anneal the wire, lowering the energy bandgap of the semiconductor by hydrogen remotion, providing therefore the possibility to design position-controlled quantum dots. This technique also provides the possibility to amplify the Raman and photoluminescence spectra, which we perform to characterize the crystal structure and strain condition of the system, and the energy gap, respectively, in the nanoscale. Similar results can be achieved by employing Tip-Enhanced Raman Scattering (TERS) and Scanning Near-field Optical Spectroscopy (SNOM) approaches, providing inelastic and elastic scattering information on the sample.