ABSTRACT
The passivation influence by ligands coverage with trioctylphosphine oxide (TOPO) and TOPO including colloidal CdSe/ZnS quantum dots (QDs) on optical properties of the semiconductor heterostructure, namely an array of InP nanowires (NWs) with InAsP nanoinsertion grown by Au-assisted molecular beam epitaxy on Si (111) substrates, was investigated. A significant dependence of the photoluminescence (PL) dynamics of the InAsP insertions on the ligand type was shown, which was associated with the changes in the excitation translation channels in the heterostructure. This change was caused by a different interaction of the ligand shells with the surface of InP NWs, which led to the formation of different interfacial low-energy states at the NW-ligand boundary, such as surface-localized antibonding orbitals and hybridized states that were energetically close to the radiating state and participate in the transfer of excitation. It was shown that the quenching of excited states associated with the capture of excitation to interfacial low-energy traps was compensated by the increasing role of the "reverse transfer" mechanism. As a result, the effectiveness of TOPO-CdSe/ZnS QDs as a novel surface passivation coating was demonstrated.
ABSTRACT
The reduction of substrate temperature is important in view of the integration of III-V materials with a Si platform. Here, we show the way to significantly decrease substrate temperature by introducing a procedure to create nanoscale holes in the native-SiOx layer on Si(111) substrate via In-induced drilling. Using the fabricated template, we successfully grew self-catalyzed GaAs nanowires by molecular-beam epitaxy. Energy-dispersive X-ray analysis reveals no indium atoms inside the nanowires. This unambiguously manifests that the procedure proposed can be used for the growth of ultra-pure GaAs nanowires.
ABSTRACT
Quantum dots tuned to atomic resonances represent an emerging field of hybrid quantum systems where the advantages of quantum dots and natural atoms can be combined. Embedding quantum dots in nanowires boosts these systems with a set of powerful possibilities, such as precise positioning of the emitters, excellent photon extraction efficiency and direct electrical contacting of quantum dots. Notably, nanowire structures can be grown on silicon substrates, allowing for a straightforward integration with silicon-based photonic devices. In this work we show controlled growth of nanowire-quantum-dot structures on silicon, frequency tuned to atomic transitions. We grow GaAs quantum dots in AlGaAs nanowires with a nearly pure crystal structure and excellent optical properties. We precisely control the dimensions of quantum dots and their position inside nanowires and demonstrate that the emission wavelength can be engineered over the range of at least 30 nm around 765 nm. By applying an external magnetic field, we are able to fine-tune the emission frequency of our nanowire quantum dots to the D2 transition of 87Rb. We use the Rb transitions to precisely measure the actual spectral line width of the photons emitted from a nanowire quantum dot to be 9.4 ± 0.7 µeV, under nonresonant excitation. Our work brings highly desirable functionalities to quantum technologies, enabling, for instance, a realization of a quantum network, based on an arbitrary number of nanowire single-photon sources, all operating at the same frequency of an atomic transition.
ABSTRACT
We investigated the interaction of an intense laser radiation with colloidal solutions containing CdSe/ZnS core shell quantum dots (QDs; mean size 3.4 nm), fullerene C(60), and Perylene. These materials would give rise to the photoinduced electron transfer and charge separation on the QDs and thus the optical limiting effect. Results confirm the intended aim, obtained by means of intermediate metastable products of reversible photochemical reactions, i.e., ion radicals of hybrid systems containing semiconductor nanoparticles.
