III-arsenide nanowires are often grown via the vapor-liquid-solid mechanism with foreign catalyst. Here we discuss the initial stage of nanowire growth with tin and lead catalyst - annealing of thin film. The influence of temperature and time of annealing was discussed.

Compressive sensing method is a widely used algorithm for shooting/capturing fast-moving objects as well as for low light photography. This paper looks into how the compressive sensing algorithm can be applied in a spatial phase light modulator. It demonstrates that a significant reduction in exposure time with no quality loss can be achieved.

A model of spontaneous formation of the core-shell structure in (In,Ga)As nanowire grown via molecular beam epitaxy without independent radial growth is proposed. Within the framework of the proposed model, the distribution of In across the axis of the nanowire was fitted. Keywords: core-shell nanowire, ternary nanowire, InGaAs nanowire, radial nanowire heterostructure.

The features of photoluminescence (PL) of hybrid nanostructures based on InP/InAsP/InP nanowires array with deposited colloidal CdSe/ZnS-trioctylphosphine oxide quantum dots at increasing pump power have been studied. Pumping was carried out by 10 ps laser pulses duration with 1 MHz repetition rate at 532 nm wavelength in the quasi-resonant region of QDs absorption. It has been established, that PL maximum of the nanostructure shifts hypsochromically with increasing of laser power, revealing a gradual dominance of the bands of its components. This PL manifestation is explained by the cascade filling of excited excitonic states, accompanied by the Auger recombination processes and light quenching. The role of free carriers absorption and energy exchange between excitonic states at high pump intensities is noted, as well as a sharp PL duration reduction associated with an increase of stimulated processes in absorption.

For n-type doping of A3B5 semiconductors silicon are commonly used. However, Si in A3B5 nanowire is p-type dopant. Species are incorporated into nanowire through the intermediate liquid phase. Solubility of metals in catalyst are usually much more than nitrogen family elements. Nitrogen family elements easily dissolve in metal carbon family elements such as lead and tin. Here we discuss the growth of GaAs nanowires with lead catalyst on Si substrate. Lead could easily dissolve nitrogen family elements as well as boron family elements, which allows to switch nanowire growth from metal-rich to pnictide-rich growth.

Experimental characterization, analytical growth models, and numerical simulations are combined to define strategies for tailoring doping inside planar GaAs nanowires.

We discuss the droplet contact angle as the key parameter influencing the morphology and the related crystal phase of vapor-liquid-solid III-V nanowires. In particular, we show that twinning superlattice Te-doped GaAs nanowires are formed only when the droplet contact angle is above 130°, and that pure wurtzite sections in self-catalyzed GaP nanowires are obtained in the stage of Ga droplet consumption when the contact angle is within the range from 95° to 105°.

A model of spontaneous formation of the radial heterostructure in arsenide nanowire in single process is proposed. Good agreement of theory and experiment was demonstrated for (In,As)As nanowires. This could be considered as an alternative approach to formation of core-shell heterostructure.

We compare the two approaches to the growth of ensembles of self-catalyzed GaP nanowires, which both allow independent control of the length and diameter

A precise model for calculating the dependence of the composition of self-catalyzed Ga(As,P) nanowires on the growth parameters without any fitting parameters is proposed. It is shown that the Ga(As, P)-nanowire composition does not depend on the growth rate at a fixed ratio of the total fluxes of Group-V- and Group-III atoms. The results of modeling are in good agreement with the experimentally observed dependence of the Ga(As,P) nanowire composition on the ratio of the fluxes of As and P atoms.

Growth theory of III-V nanowires fabricated by molecular beam epitaxy is developed to reveal the role of the substrate which can be either unpatterned or masked with an inert SiOx, layer. Axial and radial growths of nanowires are described in both cases, converging to the asymptotic stage which is independent of the substrate due to the shadowing effect. The nanowire lengths and radii are calculated as functions of time and the growth parameters. Good fits are obtained with the data on the growth kinetics of GaAs, GaP, InAs and InP nanowires.

A model of spontaneous formation of the core-shell structure in (In,Ga)As nanowire grown via molecular beam epitaxy without independent radial growth is proposed. Within the framework of the proposed model, the distribution of In across the axis of the nanowire was fitted.

We study theoretically the size distributions of nanoparticles (islands, droplets, nanowires) whose time evolution obeys the kinetic rate equations with size-dependent condensation and evaporation rates. Different effects are studied which contribute to the size distribution broadening, including kinetic fluctuations, evaporation, nucleation delay, and size-dependent growth rates. Under rather general assumptions, an analytic form of the size distribution is obtained in terms of the natural variable s which equals the number of monomers in the nanoparticle. Green's function of the continuum rate equation is shown to be Gaussian, with the size-dependent variance. We consider particular examples of the size distributions in either linear growth systems (at a constant supersaturation) or classical nucleation theory with pumping (at a time-dependent supersaturation) and compare the spectrum broadening in terms of s versus the invariant variable ρ for which the regular growth rate is size independent. For the growth rate scaling with s as s^{α} (with the growth index α between 0 and 1), the size distribution broadens for larger α in terms of s, while it narrows with α if presented in terms of ρ. We establish the conditions for obtaining a time-invariant size distribution over a given variable for different growth laws. This result applies for a wide range of systems and shows how the growth method can be optimized to narrow the size distribution over a required variable, for example, the volume, surface area, radius or length of a nanoparticle. An analysis of some concrete growth systems is presented from the viewpoint of the obtained results.

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.

Предложена модель для расчета состава самокаталитических нитевидных нанокристаллов, не содержащая подгоночных параметров. Показано, что состав нитевидных нанокристаллов Ga(As, P) не зависит от скорости роста при фиксированном отношении суммарных потоков атомов V и III групп. Результаты моделирования хорошо согласуются с экспериментально наблюдаемой зависимостью состава нитевидных нанокристаллов от соотношения потоков атомов As и P. Ключевые слова: нитевидные нанокристаллы Ga(As,P), молекулярно-пучковая эпитаксия, самокаталитический рост, количественный расчет состава.

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.

We report a new approach for monolithic integration of III-V materials into silicon, based on selective area growth and driven by a molten alloy in metal-organic vapor epitaxy. Our method includes elements of both selective area and droplet-mediated growths and combines the advantages of the two techniques. Using this approach, we obtain organized arrays of high crystalline quality InP insertions into (100) oriented Si substrates. Our detailed structural, morphological and optical studies reveal the conditions leading to defect formation. These conditions are then eliminated to optimize the process for obtaining dislocation-free InP nanostructures grown directly on Si and buried below the top surface. The PL signal from these structures exhibits a narrow peak at the InP bandgap energy. The fundamental aspects of the growth are studied by modeling the InP nucleation process. The model is fitted by our X-ray diffraction measurements and correlates well with the results of our transmission electron microscopy and optical investigations. Our method constitutes a new approach for the monolithic integration of active III-V materials into Si platforms and opens up new opportunities in active Si photonics.

We consider theoretically the length distributions of vapor-liquid-solid nanowires that grow by the material collection from the entire length of their sidewalls and with a delay of nucleation on the substrate. The obtained analytic length distribution is controlled by two parameters that describe the strength of surface diffusion and the nanowire nucleation rate. We discuss some implementations of this solution for analyzing the experimental data obtained for different III-V nanowires.

A bottom-reflectivity-enhanced ultra-thin nanowire array solar cell is proposed and studied by 3D optoelectronic simulations. By inserting a small-index MgF2 layer between the polymer and substrate, the absorption is significantly improved over a broad wavelength range due to the strong reabsorption of light reflected at the polymer/MgF2 interface. With a 5 nm-thick MgF2 layer, the GaAs nanowire array solar cell with a height of 0.4–1 μm yields a remarkable conversion efficiency ranging from 14% to 15.6%, significantly higher than conventional structures with a much larger height. Moreover, by inserting the MgF2 layer between the substrate and a part of the nanowire, in addition to between the substrate and polymer, the absorption of substrate right below the nanowire is further suppressed, leading to an optimal efficiency of 15.9%, 18%, and 5.4% for 1 μm-high GaAs, InP, and Si nanowire solar cells, respectively. This work provides a simple and universal way to achieve low-cost high-performance nanoscale solar cells.

We present a comparative study of GaAs nanowire growth on Si(111) substrates by molecular beam epitaxy with the assistance of Au and Ag colloidal nanoparticles. Our approach allows the synthesis of nanowires with different catalyst materials in separate sectors of the same substrate within the same epitaxial process. We match the experimental results to the modeling of chemical potentials and nanowire length distributions to analyze the impact of silicon incorporation into the catalyst droplets on the growth rates and size homogeneity in ensembles of Au- and Ag-catalyzed GaAs nanowires.