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GaP as well as GaAs has face-centered cubic crystal phase at standard conditions. Despite it, GaP and GaAs nanowires frequently grow in a metastable hexagonal crystal phase called wurtzite. In this work, stable growth of GaP nanowire in the metastable phase is explained by accounting the elastic strain in the nucleus of a new layer. Crystal phase switch in heterostructured Ga(As,P) nanowire caused by heterointerface was studied theoretically and experimentally. Length of wurtzite segment after the switch of crystal phase linearly increases with nanowire diameter. Such dependence can not be explained by only kinetically driven effects. We consider such dependence as an evidence of elastic strain stabilization of the metastable phase in nanowires.

Strain engineering is a powerful tool that allows tuning of the optical and electronic properties of the nanostructures, opening new pathways for the nanowire (NW)-based practical applications. We ...

III–V/Si integration is one of the bottlenecks of modern semiconductor technology. Dilute nitride phosphides (III–P–N) are among the promising materials providing lattice matching with Si. In this work, we study the effect of growth conditions on the chemical composition and properties of GaP1−xNx/GaP/Si planar heterostructures synthesized by plasma assisted molecular beam epitaxy. A series of samples with a maximum fraction of incorporated nitrogen as high as 5.05% is synthesized. The morphological, structural and optical properties of the heterostructures are studied. The tendency towards 3D growth and microtwinning in dilute nitride layers are demonstrated with the increase of nitrogen content. The most intense room temperature (RT) red photoluminescence (PL) emission is obtained with the sample containing 3.07% N. The PL intensity is found to be dependent on the N growth flux while its content only slightly changes with the flux. A low temperature PL study demonstrates efficient donor–acceptor recombination in the synthesized samples. Despite low structural perfection, the sample with the highest nitrogen content demonstrates PL response at RT centered at 1.76 eV.

Rubber materials are the key components of flexible optoelectronic devices, especially for the light-emitting diodes based on arrays of inorganic nanowires (NWs). This paper reports on polydimethylsiloxane-graft-polystyrene (PDMS-St) as a new flexible substrate of GaP NW array structures. The NWs were encapsulated by the newly introduced G-coating method to substitute the inefficient mainstream spin-coating. To further exploit the flexibility and the stretchability of the NW/PDMS-St structures, the ferrocenyl-containing polymethylhydrosiloxane was synthesized and successfully used as an electrode for the NWs. In order to make an alternative highly efficient transparent electrode, a new application of conductive single-walled carbon nanotubes was demonstrated. The novel materials and methods demonstrated unsurpassed mechanical stability of the fabricated flexible electronic devices.

The integration of direct bandgap III–V materials on Si is one of the main bottlenecks on the way to cheap and highly efficient optoelectronic devices. The goal of this work is to study the formati...

III–V planar semiconductor heterostructures based on GaPN alloy with a nitrogen concentration up to 2.12% were grown on Si(001) by plasma assisted molecular beam epitaxy. Dependence of nitrogen incorporation on the growth conditions and its effect on the crystal structure were investigated via analysis of X-ray diffraction, transmission electron microscopy, and Raman spectroscopy data. Continuous redshift and a substantial increase in intensity of the photoluminescence emission spectra were observed upon increase of nitrogen content. The effect of antiphase disorder in GaP buffer on the GaPN epilayer properties was studied. It was found that antiphase boundaries, protruding from the GaP/Si to the GaPN/GaP heterointerface, change their orientation and self-annihilate in the dilute nitride layer even with a low (0.5%) nitrogen content.

In this paper, we study light emission from a tunnel contact between the Au film on a glass substrate and the Au-coated tungsten probe of the scanning tunneling microscope at ambient conditions. We...

We found that enhanced vapor condensation in nanopores and nanochannels on hydrophilic surfaces affects contrast and spatial resolution of the atomic force microscopy (AFM) imaging. It was demonstrated, that at ambient conditions the use of conventional Si probes may provide contrast inversion of the topography image of the hydrophilic samples with nano-sized surface features whereas use of the probes modified with hydrophilic Pt/C nanowires ensures adequate AFM imaging. The phenomenon of the AFM contrast inversion and the spatial resolution improvement effect obtained with the probes modified with the nanowires are discussed. The explanation of the phenomenon considering the shape of liquid meniscus in hydrophilic nanopores and nanochannels is proposed.

Use of inorganic oxides as transport layer material is a promising way to increase the efficiency of perovskite solar cells. Results of the studies of the influence of the gas mix composition in the plasma discharge used during magnetron sputtering on the optical, electrical, and structural parameters of deposited thin nickel oxide films are reported. Addition of oxygen or nitrogen to pure argon atmosphere (up to 30 vol %) was shown to change the growth rate (1.2–2.3 nm/min), resistivity of the samples (8.5–208 Ω cm), material band gap (2.85–3.43 eV), and the spectral dependence of the extinction coefficient, while the structural and morphological parameters of synthesized thin films were not affected. The lowest extinction coefficients were found in films deposited in pure argon atmosphere, which determines the capabilities of their usage in photovoltaic converters based on perovskite compounds.

In this paper we study the solar cell based on GaN nanowires array grown on Si substrate with buffer SiC layer via molecular beam epitaxy. Crystal quality of SiC layer and GaN nanowires was studied by means of Raman scattering technique and low temperature photoluminescence measurements. Spectral and volt-ampere characteristics of the n-GaN/SiC/p-Si heterostructures with different thickness of diffusive buffer SiC-3С layers were studied. It was shown that increase of the buffer layer thickness over 100 nm leads to rise of the open circuit voltage and to increase of the efficiency of solar cell in comparison with n-GaN/p-Si heterostructure without buffer layer. Experimental data shows the presence of the defect states at the heterointerface.

A post-growth technique aimed at spatial modification of facet reflectance of edge-emitting diode lasers has been proposed. It is based on the deposition of an anti-reflection coating and subsequent precise etching with a focused ion beam. The technique allowed suppressing of high-order lateral modes in 10 μm stripe lasers based on ten layers of InAs/InGaAs quantum dots.

Tailorable synthesis of III-V semiconductor heterostructures in nanowires (NWs) enables new approaches with respect to designing photonic and electronic devices at the nanoscale. We present a comprehensive study of highly controllable self-catalyzed growth of gallium phosphide (GaP) NWs on template-free silicon (111) substrates by molecular beam epitaxy. We report the approach to form the silicon oxide layer, which reproducibly provides a high yield of vertical GaP NWs and control over the NW surface density without a pre-patterned growth mask. Above that, we present the strategy for controlling both GaP NW length and diameter independently in single- or two-staged self-catalyzed growth. The proposed approach can be extended to other III-V NWs.

Funding Information: The authors J.E., C.D. and A.K. would like to thank Jean Dussaud for his work on the MOVPE setup. V.N. would like to thank Maria Baeva for her assistance with the stretchable LED transparency measurements.J.E., C.D. and A.K. thank French National Labex GaNeX (ANR-11-LABX-0014) for MW synthesis and CL measurements. V.N. thanks the Russian Foundation for Basic Research (RFBR project no. 19-32-60040) for PDMS/MW membrane fabrication and optical measurements. I.S.M., V.N., F.M.K. thank the support from the Russian Science Foundation (grant 20-19-00256) for PDMS synthesis and electrical measurements. D.K. and A.G.N. thank Russian Foundation of Basic Research project no. 20-03-00804 for the synthesis of carbon nanotubes. F.E.K. thanks the support from the Russian Science Foundation (grant 19-79-00313) for the LED array encapsulation and membrane transfer. I.S.M., F.M.K., V.N., V.A.M., S.M., A.A.V., A.V.U., and D.A.M. thank the Ministry of Science and Higher Education of the Russian Federation (FSRM-2020-0005) for the general support. N.A. and M.T. acknowledge the financial support from the ITN Marie Curie project INDEED (grant no. 722176), by the Indo-French Centre for the Promotion of Advanced Research (IFCPAR/CEFIPRA project no. 6008-1) for MW/PDMS membrane processing and characterization. Funding Information: Funding: J.E., C.D. and A.K. thank French National Labex GaNeX (ANR-11-LABX-0014) for MW synthesis and CL measurements. V.N. thanks the Russian Foundation for Basic Research (RFBR project no. 19-32-60040) for PDMS/MW membrane fabrication and optical measurements. I.S.M., V.N., F.M.K. thank the support from the Russian Science Foundation (grant 20-19-00256) for PDMS synthesis and electrical measurements. D.K. and A.G.N. thank Russian Foundation of Basic Research project no. 20-03-00804 for the synthesis of carbon nanotubes. F.E.K. thanks the support from the Russian Science Foundation (grant 19-79-00313) for the LED array encapsulation and membrane transfer. I.S.M., F.M.K., V.N., V.A.M., S.M., A.A.V., A.V.U., and D.A.M. thank the Ministry of Science and Higher Education of the Russian Federation (FSRM-2020-0005) for the general support. N.A. and M.T. acknowledge the financial support from the ITN Marie Curie project INDEED (grant no. 722176), by the Indo-French Centre for the Promotion of Advanced Research (IFCPAR/CEFIPRA project no. 6008-1) for MW/PDMS membrane processing and characterization. Publisher Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. We propose and demonstrate both flexible and stretchable blue light-emitting diodes based on core/shell InGaN/GaN quantum well microwires embedded in polydimethylsiloxane membranes with strain-insensitive transparent electrodes involving single-walled carbon nanotubes. InGaN/GaN core-shell microwires were grown by metal-organic vapor phase epitaxy, encapsulated into a polydimethylsiloxane film, and then released from the growth substrate. The fabricated free-standing membrane of light-emitting diodes with contacts of single-walled carbon nanotube films can stand up to 20% stretching while maintaining efficient operation. Membrane-based LEDs show less than 15% degradation of electroluminescence intensity after 20 cycles of stretching thus opening an avenue for highly deformable inorganic devices.

Nowadays nanofluidic devices have a great potential in biosensing and DNA sequencing applications. This work is aimed at development of the technique for fabrication of arrays of nanochannels in silicon-glass chips by focused ion beam milling. The use of lithography with charged particles (electrons and ions) paves the way for the fabrication of micro- and nanochannels and pores as well as functional nanostructures of a more complex shape in nanofluidic devices. In this study, a technique for fabrication of microfluidic chips with a system of nanochannels connecting two independent volumes (2 half cells) was developed. It was shown experimentally that the focused ion beam etching time has an influence on both the width of the created nanochannels and their depth. We suggested using anodic bonding of a silicon wafer with the net of micro- and nanochannels with a glass plate for encapsulation of such devices that provide their long lifetime of microfluidic devices. To determine the functionality of the produced devices we studied the ionic conductivity of the produced nanochannels experimentally and using a theoretical approach. Analyzing the results, we determined the effective diameter of the nanochannels and the surface charge density inside the channel which were 20 nm and 1.5 mC/m $${}^2$$ , respectively. The proposed technique allows to create ensembles of channels with a predefined width and depth. Such systems can find wide application in studies of the transport phenomena of both ions and various molecules in nanofluidic devices.

Control and analysis of the crystal phase in semiconductor nanowires are of high importance due to the new possibilities for strain and band gap engineering for advanced nanoelectronic and nanophotonic devices. In this letter, we report the growth of the self-catalyzed GaP nanowires with a high concentration of wurtzite phase by molecular beam epitaxy on Si (111) and investigate their crystallinity. Varying the growth temperature and V/III flux ratio, we obtained wurtzite polytype segments with thicknesses in the range from several tens to 500 nm, which demonstrates the high potential of the phase bandgap engineering with highly crystalline self-catalyzed phosphide nanowires. The formation of rotational twins and wurtzite polymorph in vertical nanowires was observed through complex approach based on transmission electron microscopy, powder X-ray diffraction, and reciprocal space mapping. The phase composition, volume fraction of the crystalline phases, and wurtzite GaP lattice parameters were analyzed for the nanowires detached from the substrate. It is shown that the wurtzite phase formation occurs only in the vertically-oriented nanowires during vapor-liquid-solid growth, while the wurtzite phase is absent in GaP islands parasitically grown via the vapor-solid mechanism. The proposed approach can be used for the quantitative evaluation of the mean volume fraction of polytypic phase segments in heterostructured nanowires that are highly desirable for the optimization of growth technologies.

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.

Flexible optoelectronic structures are required in a wide range of applications. Large scale modified silicone-embedded n-GaP nanowire arrays of a record 6 µm thin membranes were studied. A homogeneous silicone encapsulation was enabled by G-coating using a heavy-load centrifuge. The synthesized graft-copolymers of polydimethylsiloxane (PDMS) and polystyrene demonstrated two times lower adhesion to Si compared to standard PDMS, allowing 3 square inch area high quality silicone/nanowire membrane mechanical release, preserving the growth Si substrate for a further re-use after chemical cleaning. The 90% transparent single-walled carbon nanotubes electrical contacts to the embedded n-GaP nanowires demonstrated mechanical and electrical stability. The presented methods can be used for the fabrication of large scale flexible inorganic optoelectronic devices.

In this article, we present the pick-and-place technique for the manipulation of single nanoparticles on non-conductive substrates using a tungsten tip irradiated by a focused electron beam from a scanning electron microscope. The developed technique allowed us to perform the precise transfer of single BaTiO3 nanoparticles from one substrate to another in order to carry out measurements of elastic light scattering as well as second harmonic generation. Also, we demonstrate a fabricated structure made by finely tuning the position of a BaTiO3 nanoparticle on top of a dielectric nanowaveguide deposited on a glass substrate. The presented technique is based on the electrostatic interaction between the sharp tungsten tip charged by the electron beam and the nanoscale object. A mechanism for nanoparticle transfer to a non-conductive substrate is proposed and the forces involved in the manipulation process are evaluated. The presented technique can be widely utilized for the fabrication of nanoscale structures on optically transparent non-conductive substrates, which presents a wide range of applications for nanophotonics.

Reduction of the wavelength in on-chip light circuitry is critically important not only for the sake of keeping up with Moore's law for photonics but also for reaching toward the spectral ranges of operation of emerging materials, such as atomically thin semiconductors, vacancy-based single-photon emitters, and quantum dots. This requires efficient and tunable light sources as well as compatible waveguide networks. For the first challenge, halide perovskites are prospective materials that enable cost-efficient fabrication of micro- and nanolasers. On the other hand, III-V semiconductor nanowires are optimal for guiding of visible light as they exhibit a high refractive index as well as excellent shape and crystalline quality beneficial for strong light confinement and long-range waveguiding. Here, we develop an integrated platform for visible light that comprises gallium phosphide (GaP) nanowires directly embedded into compact CsPbBr

Publisher's version (útgefin grein), Optical bound states in the continuum (BICs) provide a way to engineer very narrow resonances in photonic crystals. The extended interaction time in these systems is particularly promising for the enhancement of nonlinear optical processes and the development of the next generation of active optical devices. However, the achievable interaction strength is limited by the purely photonic character of optical BICs. Here, we mix the optical BIC in a photonic crystal slab with excitons in the atomically thin semiconductor MoSe2 to form nonlinear exciton-polaritons with a Rabi splitting of 27 meV, exhibiting large interaction-induced spectral blueshifts. The asymptotic BIC-like suppression of polariton radiation into the far field toward the BIC wavevector, in combination with effective reduction of the excitonic disorder through motional narrowing, results in small polariton linewidths below 3 meV. Together with a strongly wavevector-dependent Q-factor, this provides for the enhancement and control of polariton–polariton interactions and the resulting nonlinear optical effects, paving the way toward tuneable BIC-based polaritonic devices for sensing, lasing, and nonlinear optics., The authors acknowledge funding from the Ministry of Education and Science of the Russian Federation through Megagrant No. 14.Y26.31.0015. A.I.T. and D.N.K. acknowledge the UK EPSRC grant EP/P026850/1. I.A.S. acknowledges the project “Hybrid polaritonics” of Icelandic Science Foundation. Numerical calculations of the angle-resolved reflectivity maps were funded by RFBR according to the research project № 18-32-00527. Sample fabrication was funded by RFBR, project No 19-32-90269. Time-resolved measurements were partly funded by the Russian Science Foundation (Grant No. 19-72-30003). V.K. acknowledges support from the Government of the Russian Federation through the ITMO Fellowship and Professorship Program. This work was in part carried out using equipment of the SPbU Resource Centers “Nanophotonics” and “Nanotechnology”. We thank M. Zhukov, A. Bukatin, and A. Chezhegov for their assistance with the sample characterization and A. Bogdanov for the helpful discussion.

The influence of hydrogen plasma treatment on electrical and optical properties of the vertical GaN nanowires (NWs)/Si heterostructures synthesized via plasma assisted molecular beam epitaxy is studied. The effect of the treatment is thoroughly studied via variation of the passivation duration. Photoluminescence (PL) investigation demonstrates that the passivation affects the doping of the GaN NWs. The samples were processed as photodiodes with top transparent electrode to obtain detailed information about the n-GaN NWs/p-Si heterointerface under illumination. Electron beam induced current (EBIC) measurements demonstrated the absence of the potential barriers between active parts of the diode and the contacts, indicating ohmic behavior of the latter. I-V characteristics obtained in the dark and under illumination show that hydrogen can effectively passivate the recombination centers at the GaN NWs/Si heterointerface. The optimum passivation duration providing improved electrical properties is found to be 10 minutes within taken passivation regimes. It is demonstrated that the longer treatment causes degradation of the electrical properties. The discovered phenomenon is discussed in details.

In this paper we demonstrate the results on selective area growth of GaP nanowires via self-catalyzed growth method using molecular beam epitaxy (MBE) technique on patterned Si(111) substrates. The pattern fabrication method on a base of the photolithography process over an array of microspherical lenses has been studied theoretically and then optimized in order to obtain the nanostructures with controlled morphology. It was found that the positive resist thickness corresponding to the best achievable resolution in the subwavelength region is 250 nm in case of 1.5 μm silica spheres and excitation with 365 nm LED. The silica growth mask for selective epitaxy was fabricated. The ordered array of GaP nanowires was synthesized with MBE. Large scale ordering and selectivity of the growth technique is demonstrated.

Nowadays modern science and technology require development of efficient electromagnetic emitters covering far GHz and THz ranges. Semiconductor elements with negative differential resistance (NDR) such as Gunn diodes based on GaAs and InP are well-established powerful microwave emitters. In this work the Gunn diode structure based on single GaN nanowire with the potential of THz device development was proposed and investigated both theoretically and experimentally. According to the results of the numerical modeling, the Gunn generation can be obtained in the proposed geometry. Dependence of the doping concentration on the NW length necessary for the electrons domain formation was obtained. The nanostructures were grown via molecular beam epitaxy technique. Contacts to single nanowires were fabricated with the combination of e-beam lithography and thermal evaporation. It was shown experimentally that the volt-ampere characteristics of the GaN nanowire structure possess current saturation region. Experimental results correspond well to proposed numerical model.

Self-catalyzed GaP nanowire and GaP/GaPAs nanowire heterostructures have been grown on Si(111) by solid-source molecular beam epitaxy. Formation of wurtzite polytype segments with thicknesses varying from the several tens up to the 500 nm depending on the growth condition has been observed. Effect of the V/III flux ratio on the growth mechanism, nanowire structure and morphology was studied by means of scanning electron microscopy and high resolution transmission electron microscopy.

The emission characteristics of a source of single photons based on an epitaxial heterostructure with CdSe/ZnSe quantum dots and a cylindrical waveguide with a varying cross section formed in a resist layer by electron-beam lithography are investigated. It is shown that a flux of single photons at a wavelength of 530 nm with an average rate of about 1 MHz and the value g(2)(0) = 0.15 ± 0.03 of the second-order correlation function at zero delay can be generated under optical pumping at 80 K.

The results of investigation of the radiative characteristics of heterostructures with InAs/AlGaAs quantum dots (QDs) grown by molecular beam epitaxy have been presented. The properties of single QDs were determined by spectroscopy of micro-photoluminescence in cylindrical mesa-structures with a diameter of 200–1000 nm or columnar microresonators with distributed Bragg mirrors. The single-photon nature of the radiation is confirmed by measurements and analysis of the second-order correlation function g2(τ) in a wide spectral range from 630 to 730 nm.

In this work we have studied volt-ampere characteristics of single core-shell GaN/InGaN/GaN nanowire. It was experimentally shown that negative differential resistance effect can be obtained in the studied heterostructure. On the base of numerical calculation results the model describing negative differential resistance phenomenon was proposed. We assume this effect to be related with strong localization of current flow inside the nanowire and emergence of Gunn effect in this area.

In this paper we study growth of quasi-one-dimensional GaN nanowires (NWs) and nanotube (NT)-like nanostructures on Si(111) substrates covered with a thin AlN layer grown by means of plasma-assisted molecular beam epitaxy. In the first part of our study we investigate the influence of the growth parameters on the geometrical properties of the GaN NW arrays. First, we find that the annealing procedure carried out prior to deposition of the AlN buffer affects the elongation rate and the surface density of the wires. It has been experimentally demonstrated that the NW elongation rate and the surface density drastically depend on the substrate growth temperature, where 800 °C corresponds to the maximum elongation rate of the NWs. In the second part of the study, we introduce a new dopant-stimulated method for GaN nanotube-like nanostructure synthesis using a high-intensity Si flux. Transmission electron microscopy was used to investigate the morphological features of the GaN nanostructures. The synthesized structures have a hexagonal cross-section and possess high crystal quality. We propose a theoretical model of the novel nanostructure formation which includes the role of the dopant Si. Some of the Si-doped samples were studied with the photoluminescence (PL) technique. The analysis of the PL spectra shows that the highest value of donor concentration in the nanostructures exceeds 5∙1019 cm−3.

In this report, we demonstrate that the use of a GaN seeding layer prepared by droplet epitaxy prior to the growth of epitaxial GaN on Si (111) can lead to the formation of oriented arrays of Y-shaped nanoislands (nanotripods) and nanowires and affects the surface density of the nanostructures. From the transmission electron microscopy studies, it is shown that at least some of the seeding islands have a cubic zinc-blende (ZB) GaN structure, and their {111} facets act as the nucleation centers for further growth of GaN nanorods with a wurtzite (WZ) structure. It is also demonstrated that even if the Ga droplets are deposited on the silicon surface prior to the nitridation, a silicon nitride interlayer between silicon and GaN will be inevitably formed in the further growth process. The density and the position of the seeding centers can be controlled with growth parameter variation during the droplet epitaxy; thus the technique proposed and studied in this report can be used for the preparation of site- and density-controlled arrays of nanostructures.

In this work we investigate effects of the crystal phase, twinning defects and shell formation on the work function distribution over the surface of axially heterostructured GaP/GaPAs/GaP nanowires via frequency-modulated Kelvin probe force microscopy. Analysis of experimental data is supported by theoretical model based on density functional theory and Schrodinger–Poisson calculations. The study revealed that the work function of pure (110) ZB and ( 11 2 ¯ 0 ) WZ GaP is 4.34 eV and 4.20 eV respectively. The work function is found to be sensitive to the lattice twinning period which can additionally shift it between the value of WZ and ZB. Formation of a sub-monolayer thick GaPAs shell results in drastic increase of the work function (up to 4.75 eV). Thus, in this work we introduce several techniques for manipulating GaP nanowire work function. The ability to distinguish different crystal phases of the same material by means of Kelvin probe microscopy is shown for the first time.

We report on pseudomorphic MBE growth of CdTe/Zn(Mg)(Se)Te quantum dot (QD) structures on InAs(100) substrates and studies of their structural and optical properties. The QDs were fabricated by using a thermal activation technique comprising deposition of a strained CdTe 2D layer, covering it with amorphous Te, followed by fast thermal desorption of the Te layer, which results in a 2D-3D RHEED pattern transition. The QDs exhibit the surface density as low as ~1010 cm−2. The influence of MBE growth parameters and the structure design on photoluminescence properties of the QDs are discussed. Single QD photoluminescence was observed at T=8 K from the 200-nm-wide mesa-structures made of the CdTe QD structures, and the antibunching effect with g(2)(0)=0.16±0.04 was demonstrated. The peculiarities of MBE growth of ZnTe/MgTe/MgSe short-period superlattices nearly lattice-matched to InAs, which could serve as wide gap barriers for efficient electron and hole confinement in the CdTe/Zn(Mg)(Se)Te QDs, are also described.

Recent trends to employ high-index dielectric particles in nanophotonics are motivated by their reduced dissipative losses and large resonant enhancement of nonlinear effects at the nanoscale. Because silicon is a centrosymmetric material, the studies of nonlinear optical properties of silicon nanoparticles have been targeting primarily the third-harmonic generation effects. Here we demonstrate, both experimentally and theoretically, that resonantly excited nanocrystalline silicon nanoparticles fabricated by an optimized laser printing technique can exhibit strong second-harmonic generation (SHG) effects. We attribute an unexpectedly high yield of the nonlinear conversion to a nanocrystalline structure of nanoparticles supporting the Mie resonances. The demonstrated efficient SHG at green light from a single silicon nanoparticle is 2 orders of magnitude higher than that from unstructured silicon films. This efficiency is significantly higher than that of many plasmonic nanostructures and small silicon nanoparticles in the visible range, and it can be useful for a design of nonlinear nanoantennas and silicon-based integrated light sources.

Various clusters of metallic or dielectric nanoparticles can exhibit sharp Fano resonances originating from at least two modes interference of different spectral width. However, for practical applications such as biosensing or nonlinear nanophotonics, the fine-tuning of the Fano resonances is generally required. Here, we propose and demonstrate a novel type of hybrid oligomers consisting of asymmetric metal-dielectric (Au/Si) nanoparticles with a sharp Fano resonance in the visible range, which has a predominantly magnetic origin. We demonstrate both numerically and experimentally that such hybrid nanoparticle oligomers allow fine-tuning of the Fano resonance via fs-laser-induced melting of Au nanoparticles at the nanometer scale. We show that the Fano resonance wavelength can be changed by fs-laser reshaping very precisely (within 15 nm) being accompanied by a reconfiguration of its profile.

Microdisk lasers demonstrate high performance and low threshold characteristics due to supporting of whispering gallery modes with a high quality factor. One of the challenging problems impeding some practical applications of whispering gallery mode lasers is that they have isotropic emission predominantly lying in the plane of the cavity. In this work, we present a novel method that provides both enhancement of the laser emission and modifies its directivity, making the vertical direction favorable. Electromagnetic energy outcouples from the cavity through the platinum–carbon plasmonic wire nanoantenna grown by electron-beam assisted deposition right up the side wall of the cavity. Evanescent field of whispering gallery mode excites surface plasmon polariton which propagates along the nanoantenna and scatters at its tip. We demonstrate 20× enhancement of the dominant mode intensity with 24 dB of side mode suppression increment without essential worsening of the Q-factor which remains over 3 × 104. The pr...

It has been demonstrated experimentally that the local irradiation of a thin gold film on glass with electrons with an energy of 5 keV led to an increase in the thickness of the irradiated area. When the film was subjected to local irradiation with electrons with an energy of 25 keV, the irradiated region became thinner and a gold ring was formed along the perimeter of this region. At high densities of the electron current, thickened regions of the film assumed the shape of fractal nanostructures. The observed effects were induced by the formation of a negative charge region on the surface of glass (or in the bulk of it) and the migration of positive gold ions into this region.

8mJ pulse energy is achieved in the thin-rod Yb:YAG laser amplifier at 1.5kHz repetition rate that is more than 3 times surpasses the previous record. Using thin tapered rods for further energy scaling is proposed.

Engineering of nonlinear optical response in nanostructures is one of the key topics in nanophotonics, as it allows for broad frequency conversion at the nanoscale. Nevertheless, the application of the developed designs is limited by either high cost of their manufacturing or low conversion efficiencies. This paper reports on the efficient second-harmonic generation in a free-standing GaP nanowire array encapsulated in a polymer membrane. Light coupling with optical resonances and field confinement in the nanowires together with high nonlinearity of GaP material yield a strong second-harmonic signal and efficient near-infrared (800-1200 nm) to visible upconversion. The fabricated nanowire-based membranes demonstrate high flexibility and semitransparency for the incident infrared radiation, allowing utilizing them for infrared imaging, which can be easily integrated into different optical schemes without disturbing the visualized beam., ACS Nano, 14 (8), ISSN:1936-0851, ISSN:1936-086X

We report on single-photon emission of InAs/AlGaAs self-assembled quantum dots (QDs) grown by molecular beam epitaxy. By varying the growth conditions the QDs luminescence could be tuned over a wide wavelength range from 0.64 to 1 μm, including red part of the visible spectrum. Emission properties of individual QDs are investigated by micro-photoluminescence (μ-PL) spectroscopy using 500-nm-size etched mesa structures. Autocorrelation functions of photons from single QDs, measured in the wide spectral range demonstrate antibunching effect at zero delay time with a value of g(2)(0) ~ 0.17 that is a clear evidence of non-classical light.

The role of Si (111) substrate surface preparation and buffer layer composition in the growth, electronic and optical properties of the GaN nanowires (NWs) synthesized via plasma-assisted molecular beam epitaxy is studied. A comparison study of GaN NWs growth on the bare Si (111) substrate, silicon nitride interlayer, predeposited AlN and GaO x buffer layers, monolayer thick Ga wetting layer and GaN seeding layer prepared by the droplet epitaxy is performed. It is demonstrated that the homogeneity and the morphology of the NW arrays drastically depend on the chosen buffer layer and surface preparation technique. An effect of the buffer and seeding layers on the nucleation and desorption is also discussed. The lowest NWs surface density of 14 μm-2 is obtained on AlN buffer layer and the highest density exceeding the latter value by more than an order of magnitude corresponds to the growth on the 0.3 ML thick Ga wetting layer. It is shown, that the highest NWs mean elongation rate is obtained with AlN buffer layer, while the lowest elongation rate corresponds to the bare Si (111) surface and it is twice as lower as the first case. It is found, that use of AlN buffer layer corresponds to the most homogeneous NWs array with the smallest length dispersion while the least homogeneous array corresponds to the bare Si substrate. Vertically aligned GaN NWs array on the wide bandgap GaO x semiconductor buffer layer grown by plasma-enhanced chemical vapor deposition demonstrates its potential for electronic applications. Photoluminescence (PL) study of the synthesized samples is characterized by an intense optical response related to the excitons bound to neutral donors. The highest PL intensity is obtained in the sample with AlN buffer layer.

Efficient second harmonic generation (SHG) in nanophotonic designs based on all-dielectric nanostructures demands materials with large values of the quadratic nonlinear susceptibility, low dissipative losses, and high refractive index. One of the best materials meeting all these parameters is gallium phosphide (GaP). However, second-order nonlinearity requires high crystallinity and morphology quality of the GaP layer grown for further lithographic processing. Here we develop a method to fabricate high-quality crystalline GaP metasurfaces, which demonstrate pronounced linear and nonlinear optical properties. Direct growth of a GaP layer on a sapphire substrate tackles the previous problem of wafer bonding, because of high optical contrast between fabricated resonant nanoparticles and the substrate. As a result, the fabricated GaP metasurface supports bound state in continuum mode with an experimental quality factor around 100 yielding a strong enhancement of SHG in narrow spectral range. We believe that the developed approach will become a versatile platform for nonlinear all-dielectric nanophotonics.

Fabrication of hybrid micro- and nanostructures with a strong nonlinear response is challenging and represents a great interest due to a wide range of photonic applications. Usually, such structures are produced by quite complicated and time-consuming techniques. This work demonstrates laser-induced hybrid metal-dielectric structures with strong nonlinear properties obtained by a single-step fabrication process. We determine the influence of several incident femtosecond pulses on the Au/Si bi-layer film on produced structure morphology. The created hybrid systems represent isolated nanoparticles with a height of 250–500 nm exceeding the total thickness of the Au-Si bi-layer. It is shown that fabricated hybrid nanostructures demonstrate enhancement of the SHG signal (up to two orders of magnitude) compared to the initial planar sample and a broadband photoluminescence signal (more than 200 nm in width) in the visible spectral region. We establish the correlation between nonlinear signal and phase composition provided by Raman scattering measurements. Such laser-induced structures have significant potential in optical sensing applications and can be used as components for different nanophotonic devices.

The never-ending struggle against counterfeit demands the constant development of security labels and their fabrication methods. This study demonstrates a novel type of security label based on downconversion photoluminescence from erbium-doped silicon. For fabrication of these labels, a femtosecond laser is applied to selectively irradiate a double-layered Er/Si thin film, which is accomplished by Er incorporation into a silicon matrix and silicon-layer crystallization. The study of laser-induced heating demonstrates that it creates optically active erbium centers in silicon, providing stable and enhanced photoluminescence at 1530 nm. Such a technique is utilized to create two types of anti-counterfeiting labels. The first type is realized by the single-step direct laser writing of luminescent areas and detected by optical microscopy as holes in the film forming the desired image. The second type, with a higher degree of security, is realized by adding other fabrication steps, including the chemical etching of the Er layer and laser writing of additional non-luminescent holes over an initially recorded image. During laser excitation at 525 nm of luminescent holes of the labels, a photoluminescent picture repeating desired data can be seen. The proposed labels are easily scalable and perspective for labeling of goods, securities, and luxury items.

We report on the molecular beam epitaxy (MBE) of heterostructures with CdTe/ZnTe quantum dots (QDs) with relatively low surface density, which could be used as single-photon emitters. The QDs were formed on the surface of a 3.1- to 4.5-monolayer-thick two-dimensional strained CdTe layer by depositing amorphous Te layer and its fast thermal desorption. Subsequent thermal annealing of the surface with QDs in the absence of external Te flux led to strong broadening and short-wavelength shift of the QD photoluminescence (PL) peak. Measurement of the micro-PL spectra of individual CdTe/ZnTe quantum dots in fabricated mesastructures with a diameter of 200—1000 nm allowed estimation of the QD surface density as ~1010 cm–2.

Using methods of numerical simulation, the modes of operation are considered and structures are determined for solar cells of combined dimension based on a planar GaPNAs/Si heterostructure and an array of GaN nanowires. It is shown that the array of GaN nanowires features antireflective properties at a level no lower than 2.5% under illumination with the AM1.5D solar spectrum. The efficiency of solar cells is affected to the greatest extent by the lifetimes of minority charge carriers and the thickness of photoactive layers. It is demonstrated that the efficiency of two-junction solar cells composed of GaPNAs alloy layers and an array of GaN nanowires on a Si substrate can be as high as 32% for AM1.5D.

Technologies and methods of prototyping microfluidic devices are widely used in solving many biological problems and testing of operability of new microanalytic systems. This study is devoted to analyzing the features of the formation of microstructures in SU-8 photoresist and the preparation of replicas in polydimethyl siloxane by the soft lithography method. It has been shown that the aspect ratio of the resultant microstructures is determined by their shape, size, and the force of resist adhesion to the silicon substrate and the efficiency of the circulation of the developer around microstructures. In the replication of complex microstructures, an aspect ratio of ~25 is attained. The technology considered here is used to prepare microfluidic chips with mechanical traps for fixation and the in vitro analysis of living cells.

The authors at ANU were supported by the Australian Research Council. The authors at DSI were supported by DSI core funds and A*STAR SERC Pharos program, Grant 152 73 00025 (Singapore).

Nanomechanical oscillators based on amorphous carbon whiskers, localized on the top of tungsten tip were fabricated and investigated. The whiskers were grown in the scanning electron microscope chamber using focused electron beam technique. Oscillation trajectories and amplitude-frequency characteristic of the oscillator were visualized at low and ambient pressure using a scanning electron microscope and a confocal laser-scanning microscope, respectively. We experimentally show that at ambient pressure, the resonant frequency decreases significantly but the Q-factor of the oscillator unexpectedly increases with respect to experimental data acquired at low pressure. The explanation was provided taking into account the role of thin water layer absorbed on the whisker from atmosphere. The model of the coupled oscillators is considered.

Meta-optics based on optically-resonant dielectric nanostructures is a rapidly developing research field with many potential applications. Halide perovskite metasurfaces emerged recently as a novel platform for meta-optics, and they offer unique opportunities for control of light in optoelectronic devices. Here we employ the generalized Kerker conditions to overlap electric and magnetic Mie resonances in each meta-atom of MAPbBr3 perovskite metasurface and demonstrate broadband suppression of reflection down to 4%. We reveal also that metasurface nanostructuring is also beneficial for the enhancement of photoluminescence. Our results may be useful for applications of nanostructured halide perovskites in photovoltaics and semi-transparent multifunctional metadevices where reflection reduction is important for their high efficiency.