Search

Surfaces with special wettability properties, such as omniphobicity or omniphilicity, are essential for functional devices that use both aqueous and organic media. Micropatterning of omniphobic and omniphilic properties can provide a wide range of applications, including miniaturized experiments using both aqueous and organic media. Herein, an approach for creating omniphobic-omniphilic micropatterns based on selective photoacid polymerization of octa(3-glycidyloxypropyl) polyhedral oligomeric silsesquioxane modified with mono-aminopropyl-terminated polydimethylsiloxane is reported. The composition of the polymeric coatings using infrared spectroscopy; patterning accuracy using atomic force microscopy and scanning electron microscopy; wettability characteristics of the omniphobic, and omniphilic surfaces using contact angle measurements are studied. The proposed approach allows for single-step micropatterning (sub-10 µm) or macropatterning (3 mm). Liquids with surface tensions >22.8 mN m−1 can be confined to the omniphilic areas by the omniphobic borders. C2C12 cells are successfully cultivated in omniphilic areas, demonstrating their cell compatibility. The cells adhere to and grow on the entire surface of the pattern, without any signs of cytotoxicity. However, the strongest adhesion is observed in the omniphilic areas, making it possible to create cell micropatterns in a single step. The proposed method for the fabrication of omniphobic-omniphilic transparent, mechanically robust, biocompatible patterns can find applications in microfluidics, biotechnology or miniaturized biological screening experiments.

The architecture of transparent contacts is of utmost importance for creation of efficient flexible light-emitting devices (LEDs) and other deformable electronic devices. We successfully combined the newly synthesized transparent and durable silicone rubbers and the semiconductor materials with original fabrication methods to design LEDs and demonstrate their significant flexibility. We developed electrodes based on a composite GaP nanowire-phenylethyl-functionalized silicone rubber membrane, improved with single-walled carbon nanotube films for a hybrid poly(ethylene oxide)-metal-halide perovskite (CsPbBr3) flexible green LED. The proposed approach provides a novel platform for fabrication of flexible hybrid optoelectronic devices.

Polysiloxanes and materials based on them (silicone materials) are of great interest in optoelectronics due to their high flexibility, good film-forming ability, and optical transparency. According to the literature, polysiloxanes are suggested to be very promising in the field of optoelectronics and could be employed in the composition of liquid crystal devices, computer memory drives organic light emitting diodes (OLED), and organic photovoltaic devices, including dye synthesized solar cells (DSSC). Polysiloxanes are also a promising material for novel optoectronic devices, such as LEDs based on arrays of III–V nanowires (NWs). In this review, we analyze the currently existing types of silicone materials and their main properties, which are used in optoelectronic device development.

The films of single-walled carbon nanotubes (SWCNTs) are a promising material for flexible transparent electrodes, which performance depends not only on the properties of individual nanotubes but also, foremost, on bundling of individual nanotubes. This work investigates the impact of densification on optical and electronic properties of SWCNT bundles and fabricated films. Our ab initio analysis shows that the optimally densified bundles, consisting of a mixture of quasi-metallic and semiconducting SWCNTs, demonstrate quasi-metallic behavior and can be considered as an effective conducting medium. Our density functional theory calculations indicate the band curving and bandgap narrowing with the reduction of the distance between nanotubes inside bundles. Simulation results are consistent with the observed conductivity improvement and shift of the absorption peaks in SWCNT films densified in isopropyl alcohol. Therefore, not only individual nanotubes but also the bundles should be considered as building blocks for high-performance transparent conductive SWCNT-based films.

Electrically driven plasmonic nanoantennas can be integrated as a local source of the optical signal of advanced photonic schemes for on-chip data processing. The inelastic electron tunneling provides the photon generation or launch of surface plasmon waves. This process can be enhanced by the local density of optical states of nanoantennas. In this paper, we used scanning tunnel microscopy-induced light emission to probe the local optoelectronic properties of single gold nanodiscs. The electromagnetic field distribution in the vicinity of plasmonic structures was investigated with high spatial resolution. The obtained photon maps reveal the nonuniform distribution of electromagnetic near-fields, which is consistent with nanoantenna optical modes. Also, the analysis of derived I(V) curves showed a direct correlation between the nanoantenna optical states and the appearance of features on current-voltage characteristics.

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.

The results of experiments aimed at fabricating and studying the properties of photodetector structures based on single-layer graphene produced by chemical vapor deposition are presented. The configuration of a Ta2O5 vertical microcavity with a resonance wavelength of about 850 nm and a lower dielectric SiO2/Ta2O5 distributed Bragg reflector is taken as the base structure. The conditions for the transfer and fabrication of mesas in the graphene layer on the microcavity surface are optimized. The diagnostics by Raman spectroscopy of the structural quality of graphene after fabrication of the mesas in the graphene layer and contact pads are indicative of the single-layer structure of graphene with a low intensity of features in its spectrum, responsible for imperfection of the structure. The photocurrent is measured under local optical pumping.

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 ...

Attempts to improve solar cells efficiency touch all its constituents and are directly related to their fabrication protocols. While the most promising material platform for high efficiency photovoltaic devices is still III-V semiconductors, introduction of novel materials like single-walled carbon nanotubes (SWCNTs), which are characterized by unique combination of conductivity and transparency, might greatly yield the device performance. Here, for the first time, we present the results of the fabrication and characterization of a thin-film GaAs solar cell with a SWCNT top contact. We examine the contact between the SWCNT film and the semiconductor structure by means of the optical and electron beam-induced current techniques. The fabricated device demonstrates better performance, that is, increased power conversion efficiency from 10.6% to 11.5% when compared to the cell with the traditional metal contact grid, stemming from the enhanced photocurrent collection efficiency and low parasitic light absorption in the emitter layer. We envision future prospects to exploit the multifunctionality of the SWCNTs in fabrication of highly efficient photovoltaic devices including flexible solar cells.

A compact optical layout of a pulse shaper for strongly chirped laser pulses of nanosecond time scale exploiting a tilted chirped volume Bragg grating and a programmable spatial light modulator is proposed. The setup has a non-zero frequency dispersion; thus it may be used for stretching or compressing the pulse and controlling its shape simultaneously. The feasibility of spectral shaping with a resolution of 0.16 nm, corresponding to a time resolution of 150 ps, and a contrast ratio of 102 is demonstrated experimentally.

The development of nanophotonics systems for the manipulation of luminescent properties of single quantum emitters is essential for quantum communication and computing. Dielectric nanosystems enable various opportunities for light control through inherent electric and magnetic resonances; however, their full potential has not yet been discovered. Here, emission properties of nitrogen-vacancy (NV) centers in nanodiamonds placed in the near-field zone of silicon nanoresonators are investigated. It is demonstrated experimentally that the spontaneous emission rate of single NV centers in 50 nm nanodiamonds can be modified by their coupling to spherical nanoantennas, reducing the mode of the lifetime distribution by [Formula: see text] times from 16 to 9 ns. It is also shown that the collected intensity of photoluminescence emission from multiple NV centers in a 150 nm nanodiamond coupled to a cylindrical nanoantenna is increased by more than 50% compared to the intensity from the same nanodiamond on a bare substrate.

We propose an original method of suppressing thermally induced beam distortions in composite active elements of disk geometry. The main idea of the method is to use a heatsink of special geometry to provide heat removal from the active element only in the pump area. In this way, the heat flows and temperature gradients in the thick active element, and, as a consequence, thermally induced distortions are reduced. The wavefront distortions, temperature, and gain in the composite element mounted in a profiled heatsink have been simulated numerically and measured in experiment. A 2.5-fold reduction of thermally induced lensing compared to a flat heatsink was demonstrated in the experiment at the same small signal gain.

Semiconductor nanowires exhibit numerous capabilities to advance the development of future optoelectronic devices. Among the III-V material family, gallium phosphide (GaP) is an attractive platform with low optical absorption and high nonlinear susceptibility, making it especially promising for nanophotonic applications. However, investigation of single nanostructures and their waveguiding properties remains challenging owing to typically planar experimental arrangements. Here we study the linear and nonlinear waveguiding optical properties of a single GaP nanowire in a special experimental layout, where an optically trapped structure is aligned along its major axis. We demonstrate efficient second harmonic generation in individual nanowires and unravel phase matching conditions, linking between linear guiding properties of the structure and its nonlinear tensorial susceptibility. The capability to pick up single nanowires, sort them with the aid of optomechanical manipulation and accurately position pre-tested structures opens a new avenue for the generation of optoelectronic origami-type devices.

We present an original approach to realistic modeling of light focusing by microsphere systems to form the photonic jets for nano-patterning of the substrates with high refractive index. In simulations we analyze the photonic jets produced by a single sphere and close-packed array of microspheres on the photoresist layer and Si substrate. We show how the lithographic profiles can be controlled by varying the exposure dose and system geometry in wide ranges of photoresist layer thicknesses and microsphere sizes. The modeling covers the entire lithographic system and accounts for the interference of focused light transmitted through the microlenses and reflected from the Si substrate. We use our approach to optimize the size of the lithographic pattern and confirm the simulation results experimentally. The suggested set of methods is rather universal and may be applied to other microlens and resist materials to minimize lithography lateral resolution.

It is shown for the first time that the vacuum poling of soda-lime silicate glass and the subsequent processing of the glass in a melt containing silver ions results in the formation of silver nanoparticles buried in the subanodic region of the glass at a depth of 800–1700 nm. We associate the formation of nanoparticles with the transfer of electrons from negatively charged non-bridging oxygen atoms to silver ions, their reduction as well as their clustering. The nanoparticles do not form in the ion-depleted area just beneath the glass surface, which indicates the absence of a spatial charge (negatively charged oxygen atoms) in this region of the vacuum-poled glass. In consequence, the neutralization of the glass via switching of non-bridging oxygen bonds to bridging ones, which leads to the release of oxygen, should occur in parallel with the shift of calcium, magnesium, and sodium ions into the depth of the glass.

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.

Semiconductor nanowires (NW) have received much attention for their unique properties providing exceptional flexibility in device engineering. In particular, gallium phosphide NWs demonstrate effective wave-guiding properties and broadband nonlinear frequency conversion, and find applications in green to amber optical range optoelectronics and photocatalytic devices. They also exhibit one of the broadest transparency range, high values of the nonlinear refractive index and good thermal conductivity that make them perspective for nanophotonics.

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.

We design and demonstrate dramatic suppression of reflection from MAPbBr3 halide-perovskite metasurfaces. We employ the Kerker effect and engineer both electric and magnetic Mie resonances in each dielectric meta-atom to achieve a broadband performance.

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.

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

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.

Since Complementary metal–oxide–semiconductor technology is the conventional technology for micro- and optoelectronics, integration of emerging materials, such as halide perovskites, into the process is an important branch of perovskite technologies development. In this regard ITO free device research becomes increasingly important. The Perovskite Light-Emitting electrochemical cells are a promising alternative to conventional Perovskite Light Emitting Diodes. In this work we demonstrate green (λEL = 523 nm) CsPbBr3 Perovskite Light-Emitting electrochemical cells with luminescence intensity of 50 kd/m2 integrated with Si++(111) substrate.