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Hybrid nanostructures based on InGaN nanowires with decorated plasmonic silver nanoparticles are investigated in the present study. It is shown that plasmonic nanoparticles induce the redistribution of room temperature photoluminescence between short-wavelength and long-wavelength peaks of InGaN nanowires. It is defined that short-wavelength maxima decreased by 20%, whereas the long-wavelength maxima increased by 19%. We attribute this phenomenon to the energy transfer and enhancement between the coalesced part of the NWs with 10–13% In content and the tips above with an In content of about 20–23%. A proposed Fröhlich resonance model for silver NPs surrounded by a medium with refractive index of 2.45 and spread 0.1 explains the enhancement effect, whereas the decreasing of the short-wavelength peak is associated with the diffusion of charge carriers between the coalesced part of the NWs and the tips above. [ABSTRACT FROM AUTHOR]

GaN nanowires were grown using selective area plasma-assisted molecular beam epitaxy on SiOx/Si(111) substrates patterned with microsphere lithography. For the first time, the temperature–Ga/N2 flux ratio map was established for selective area epitaxy of GaN nanowires. It is shown that the growth selectivity for GaN nanowires without any parasitic growth on a silica mask can be obtained in a relatively narrow range of substrate temperatures and Ga/N2 flux ratios. A model was developed that explains the selective growth range, which appeared to be highly sensitive to the growth temperature and Ga flux, as well as to the radius and pitch of the patterned pinholes. High crystal quality in the GaN nanowires was confirmed through low-temperature photoluminescence measurements. [ABSTRACT FROM AUTHOR]

Experimental data on the rapid (≈4.4 nm s−1) axial growth rate of narrow (≈9 nm in radius) InAs nanowires (NWs) obtained by Au‐catalyzed molecular beam epitaxy on Si substrates at a low surface temperature of 270 °C are presented. These NWs exhibit pure wurtzite crystal structure and an unusually high ratio of the average NW length over the effective thickness of deposited InAs of about 60 despite the presence of parasitic InAs islands on the Si substrate. These trends are explained within a dedicated growth model. In the absence of In evaporation, In atoms either diffuse from the substrate to the NW tips or remain in the parasitic layer. This leads to a linear time dependence of the NW length and other unusual growth properties that are thought to have not previously been accessed. [ABSTRACT FROM AUTHOR]

The influence of shadow effect originating from the neighboring nanowires on the nanowire growth is theoretically investigated. The nanowire axial and radial growth rates and the nanowire shape are shown to be strongly dependent on the nanowire surface density and the direction of incident flux. Theoretical predictions are compared with the experimental shapes of InAs nanowires grown by the Au-catalyzed molecular beam epitaxy. In particular, the barrel-like shape observed in dense arrays of InAs nanowires is well described by the model. Very importantly, we show that the shadow effect helps to avoid otherwise enabled radial growth and to preserve the cylindrical nanowire shape. [ABSTRACT FROM AUTHOR]

We propose a new insight into the mechanism of low-temperature Au-assisted growth of InAs nanowires during molecular beam epitaxy (MBE). The nanowire MBE growth was achieved at a temperature of 270 °C on both Si(111) and SiC/Si(111) substrates. A special procedure of substrate preparation was used to obtain a high yield of nanowires grown perpendicularly to the substrate. The morphology of the InAs nanowire array was studied by scanning electron microscopy (SEM) revealing a significantly higher percentage of vertical InAs nanowires compared with previous works. The structural properties of nanowires and the catalyst composition were investigated by analytical methods of transmission electron microscopy (TEM). A theoretical assessment of the growth of InAs nanowires in the frame of the classical nucleation theory has shown the possibility of vapor–solid–solid growth at extremely low temperature, e.g., at 270 °C. It was found that the presence of elastic stresses due to the lattice mismatch between the solid catalyst particle and the nanowire material influences the nanowire growth rate. This important feature of nucleation in solid in the case of vapor–solid–solid growth of III–V nanowires was investigated for the first time. Also, we have shown that the material transport of arsenic towards the interface between the catalyst particle and the nanowire top limits the nanowire growth rate. Further development of the low-temperature growth methods facilitates the integration of III–V semiconductors with silicon electronics. [ABSTRACT FROM AUTHOR]

Control of directionality of emissions is an important task for the realization of novel nanophotonic devices based on nanowires. Most of the existing approaches providing high directionality of the light emitted from nanowires are based on the utilization of the tapered shape of nanowires, serving as nanoantenna coupling with the light waveguided in nanowire and the directional output beam. Here we report the beaming of the emitted light with wavelength near 800 nm by naturally formed core-shell AlGaAs NW with multiply GaAs quantum dots (QDs) diameter 30 nm and height 10 nm, while the diameter of NW 130 nm, what does not support efficient emission into waveguided modes, including the mode HE11. Experimental measurements show that intensity of emission for directions in the vicinity of the axis of NW is about two orders of magnitude higher than for perpendicular directions. The developed theoretical approach allowed us to calculate the probability of spontaneous emission for various directions and into waveguided modes and showed that highly directional radiation can be provided by the intrinsic emission properties of cylindrical NW. Our results suggest that for the small diameter of NW, directional emissions are associated with an TM0 leaky mode (when electric field oriented in axial direction) and therefore manifests in an existence of axial electric dipole transitions in quantum dots. [ABSTRACT FROM AUTHOR]

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 FROM AUTHOR]

Controlled growth of heterostructured nanowires and mechanisms of their formation have been actively studied during the last decades due to perspectives of their implementation. Here, we report on the self-catalyzed growth of axially heterostructured GaPN/GaP nanowires on Si(111) by plasma-assisted molecular beam epitaxy. Nanowire composition and structural properties were examined by means of Raman microspectroscopy and transmission electron microscopy. To study the optical properties of the synthesized nanoheterostructures, the nanowire array was embedded into the silicone rubber membrane and further released from the growth substrate. The reported approach allows us to study the nanowire optical properties avoiding the response from the parasitically grown island layer. Photoluminescence and Raman studies reveal different nitrogen content in nanowires and parasitic island layer. The effect is discussed in terms of the difference in vapor solid and vapor liquid solid growth mechanisms. Photoluminescence studies at low temperature (5K) demonstrate the transition to the quasi-direct gap in the nanowires typical for diluted nitrides with low N-content. The bright room temperature photoluminescent response demonstrates the potential application of nanowire/polymer matrix in flexible optoelectronic devices. [ABSTRACT FROM AUTHOR]