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During the self-catalyzed GaAs nanowire growth formation of parasitic GaAs crystallites is observed. The reasons for crystallite formation are explained on the base of Monte Carlo simulation results. During simultaneous deposition of gallium and arsenic on the GaAs(111)B substrate coated by a silicon oxide film, liquid gallium droplets nucleate on the oxide surface. After nucleation, droplets enlarge in size with time and etch the oxide layer. Formation of GaAs crystal structures becomes possible only after the Ga droplet contacts underlying crystal substrate. It is shown that excessively high arsenic and gallium deposition rates lead to the crystallite formation at the initial growth stage. The GaAs crystallites collect part of the deposited gallium and arsenic decreasing their surface concentration, thereby, adjusting the growth conditions for the nanowire growth. Therefore, during the self-catalyzed GaAs nanowire growth the self-regulation of growth conditions takes place.

Using Monte Carlo simulations, we studied the effect of readsorption on the growth rate and morphology of AIIIBVnanowires. It is demonstrated that readsorption of arsenic leads to an increase in the growth rate and premature consumption of a seed drop. The reabsorption of metal atoms leads to a slowdown in the axial growth but prolongs the growth, since it prevents the droplet from disappearing after the length of the nanowire reaches the diffusion length of the metal atoms along the side walls of the wire. It is demonstrated that it is possible to increase the diffusion length of group III elements along the side walls of the nanowire using the pulsed growth mode.

The results of the simulation of the GaAs nanowire self-catalyzed growth via vapor-liquid-solid mechanism using various pulse modes are presented in this work.

The main features of self-catalyzed III–V nanowire growth according to the vapor-liquid-solid mechanism were analyzed using Monte Carlo simulation. The nanowire growth kinetics, flux ratio influence on the nanowire morphology and growth rate were considered. For some growth conditions, the self-equalization effect of metal drop sizes during the self-catalyzed III–V nanowire growth was demonstrated. It is revealed that, only under the adsorption growth mode, all drop sizes reach a single stationary value.

The model for the explanation of GaAs crystallite formation during the self-catalyzed nanowires growth was proposed using Monte Carlo simulation.

Monte Carlo simulation of GaAs nanowires MBE pulse growth was carried out. The arsenic flux pulse durations and the pauses between pulses were analyzed for optimizing growth conditions. To increase the axial wire growth rate at the initial stage the regime of additional arsenic flux modulation was considered. Growth in a high arsenic flux was proposed to start and stepwise reduce it during the growth process. This approach made it possible to increase the lifetime of a seed droplet at the nanowire top at a high crystal growth rate at the initial stage of growth.

A kinetic lattice Monte Carlo model is used to study the Ga droplets self-propelled motion along GaAs(111)A and (111)B surfaces during the initial stage of high-temperature annealing. An estimation of the droplet velocity, running along (111)A and (111)B surfaces, in a wide temperature range, is carried out. The mechanism of small Ga drops movement during high-temperature annealing is suggested. Different directions of droplets motion and the morphology of drop-crystal interface on (111)A and (111)B substrates are determined by a difference in the etching rate of (111)A and (111)B facets by liquid gallium. It is shown that metal droplets can cause step bunching.

The dependences of congruent evaporation temperature Tc and the desorption activation energies of GaAs components on the substrate surface orientation are analyzed using Monte Carlo simulation. On the vicinal surfaces with the (111)A orientation at temperatures exceeding Tc, the metal droplets start to grow at step edges, and, with the (111)B orientation, the droplets nucleate randomly on the terraces. The droplet concentration on the (111)B surface is higher than that on the (111)A surface. The droplet-crystal interface roughness is different for (111)A and (111)B orientations. The Tc of (111)B surfaces is lower than that of (111)A surfaces. For both surface orientations, Tc decreases when the vicinal surface terrace width is shorter than the double gallium diffusion length. The gallium and arsenic desorption activation energies dependence on the vicinal surface misorientation is demonstrated. A sharp increase in the arsenic desorption rate is observed with an increase of the (111)A surface coating with liquid gallium.

The nanostructures formation process using the droplet epitaxy technique was investigated by Monte Carlo simulation. The simulation was fulfilled for two-dimensional and three-dimensional geometry substrates. The nanostructures morphology dependence on the growth temperature was presented. Crystal clusters, single and double rings were observed. The nanostructures shape was shown to be determined by the gallium diffusion length. The conditions of double rings formation during the droplet epitaxy were considered using analytical and numerical approaches. The factors that determine the rings location and shape were analyzed. The growth morphology was demonstrated to be dependent on the initial distance L between the droplets. The double ring formation was possible at a low droplet density only, when the As-stabilized region could be created between the droplets.

The details of crystallization process during the self-catalyzed AIIIBV nanowires growth was analyzed using Monte Carlo simulation. It was found that a new bilayer nucleation occurs earlier than the arsenic concentration reaches its maximum, and the complete bilayer formation does not synchronize with the concentration minimum. Such time shift is explained by the dependence of crystallization intensity on the step length of the growing island of a new layer at the drop-crystal interface: during the facet growth of a limited size the growing island perimeter changes in time nonmonotonically.

A Monte Carlo lattice model is proposed to describe the formation of semiconductor nanostructures by the vapor–liquid–solid growth mechanism. This model is used to simulate the growth of GaAs nanostructures by the droplet epitaxy technique in the temperature range from 500 to 600 K in As2 fluxes with intensity of 0.005–0.04 ML/s. The morphology of the formed structures is demonstrated to depend on the growth parameters. Etching of the GaAs substrate by a gallium droplet is studied. The ranges of temperature and As flux rates necessary for the formation of GaAs nanorings are determined. The conditions of the formation of single and double concentric rings are analyzed.

Using Monte Carlo simulation and analytical description we studied the variation of catalyst drop composition during III-V nanowire formation via the vapor-liquid-solid growth mechanism. During a layer-by-layer growth mode, a cyclic dependence of arsenic concentration on the growth time in a metal drop was observed. The time shifts between the nucleation of a new layer at the liquid-solid interface and the arsenic concentration maximum in C As(t) and the time shifts between the complete monolayer formation and the arsenic concentration minimum were demonstrated. The reason of these time shifts is the nonmonotonic time dependence of the growing 2D island perimeter.

The simulation of GaAs substrates annealing was carried out using the kinetic Monte Carlo lattice model. The desorption rate temperature dependence for gallium and arsenic and the estimation of congruent temperature were obtained for different surface orientations. The dependence of the effective activation energy of gallium desorption on the surface misorientation was analyzed. Different etching rates of GaAs(111)A and GaAs(111)B surfaces with liquid gallium were demonstrated. The dependence of GaAs evaporation rate on the annealing time in a incongruent temperature range was obtained and examined.

The kinetic lattice Monte Carlo model of GaAs nanowire growth by the vapor-liquid-crystal mechanism is suggested. The catalytic and self-catalyzed growth of nanowires on the GaAs (111)B surface is simulated. The dependence of the morphology of the growing nanowires on the growth parameters is demonstrated. Upon self-catalyzed growth with gallium drops serving as the growth catalyst, the growth rate of the nanowires linearly depends on the arsenic flow in a wide range of arsenic flow rates. The decreasing dependence of the self-catalyzed growth rate of the nanowires on the initial gallium drop diameter is less steep, and the optimal growth temperature is higher than that for catalytic growth. It is shown that self-catalyzed growth is more sensitive to the ratio between the gallium and arsenic flow rates than catalytic growth.

Simulation of InAs substrate annealing was carried out using a kinetic lattice Monte Carlo model. Congruent temperature of Langmuir evaporation was estimated for different substrate orientations. Dependence of congruent temperature on substrate morphology was analyzed. Congruent temperature value was demonstrated to be dependent on substrate orientation, step density of vicinal surfaces and surface defect concentration.

The process of axial and radial Si–Ge heterostructure formation during nanowire growth by vapor–liquid–solid (VLS) mechanism was studied using Monte Carlo (MC) simulation. It was demonstrated that radial growth can be stimulated by adding chemical species that decrease the activation energy of precursor dissociation or the solubility of semiconductor material in catalyst drop. Reducing the Si adatom diffusion length also leads to Si shell formation around the Ge core. The influence of growth conditions on the composition and abruptness of axial Ge–Si heterostructures was analyzed. The composition of the Ge x Si1–x axial heterojunction (HJ) was found to be dependent on the flux ratio, the duration of Si and Ge deposition, and the catalyst drop diameter. Maximal Ge concentration in the HJ is dependent on Ge deposition time owing to gradual changing of catalyst drop composition after switching Ge and Si fluxes. The dependence of junction abruptness on the nanowire diameter was revealed: in the adsorption-induced growth mode, the abruptness decreased with diameter, and in the diffusion-induced mode it increased. This implies that abrupt Ge–Si HJ in nanowires with small diameter can be obtained only in the chemical vapor deposition (CVD) process with negligible diffusion component of growth.

The process of formation of Si-Ge heterostructures based on nanowhiskers (NWs) grown according to the vapor-liquid-solid mechanism is studied using the Monte Carlo simulation. It is found that, during growth of axial heterojunctions (HJs), it is impossible to obtain an atomically flat Si-Ge HJ, which is related to a gradual change in the catalyst-drop composition during the switch between fluxes. The dependence of the composition of the GexSi1 − x transition layer on the ratio of fluxes and on the Ge and Si deposition time is studied. It is found that the width of the axial Si-Ge HJs depends on the NW diameter. It depends linearly on the diameter under the adsorption-induced growth conditions and decreases with increasing diameter under the diffusion-induced growth conditions. This means that, as the NW thickness decreases, abrupt HJs in the Ge-Si system can be obtained only in the case of chemical-vapor-deposition growth in which the diffusion-induced growth component is insignificant.

The kinetic Monte Carlo (MC) model of nanowhisker (NW) growth is suggested. Two variants of growth are possible in the model—molecular beam epitaxy (MBE) and chemical vapor deposition (CVD). The effect of deposition conditions and growth regimes on the whisker morphology was examined within the framework of the vapor–liquid–solid (VLS) mechanism. A range of model growth conditions corresponding to NW and nanotube formation was determined. The suggested MC model was used for analyses of the morphology of the catalyst–whisker interface and for examination of Si–Ge whisker growth.

The growth of silicon nanowhiskers on the Si (111) surface activated with Au is studied by Monte Carlo simulation. The dependences of the rate of growth of whiskers on the temperature, deposition rate, and catalyst droplet diameter are obtained, and the morphological properties of the growing wirelike nanocrystal are studied. In addition to the growth of nanowhiskers, a number of experimentally observed effects, such as migration of the droplet from the whisker top, faceting of the whisker sidewalls, and branching are established for the model system. It is shown that, under certain conditions of wetting of the whisker material with the catalyst, formation of hollow nanowhiskers is possible.

The process of nanowhisker formation on the substrates activated by catalyst drops was investigated by Monte Carlo simulation. Influence of deposition conditions on whisker morphology was considered. Straight whiskers with uniform diameter could be grown using catalyst possessing large contact angle with whisker material. It was demonstrated that variation of growth conditions in such physicochemical system may result in nanotube formation. Atomic mechanism of hollow whisker formation was suggested. The range of model growth conditions for nanowhisker and nanotube formation were identified.

Nanowhisker formation on substrates activated by catalyst drops is studied by Monte Carlo simulation. Dependences of the whisker growth rate on diameter are investigated for various growth modes. The influence of deposition conditions on whisker morphology is examined. It is shown that straight thin whiskers of uniform thickness can be obtained only using a catalyst having a large contact angle with the whisker material. In such a physicochemical system, variation of growth conditions can result in nanotube formation. An atomic mechanism for the formation of a hollow whisker is proposed. Ranges of model growth conditions suitable for the growth of nanowhiskers and nanotubes are determined.

A kinetic Monte-Carlo model of the Langmuir evaporation of GaAs (111) surfaces was realized. Transition from congruent evaporation to incongruent one was observed at congruent evaporation temperature Tc. The reason of such transition is liquid Ga droplet formation at temperatures above Tc. The value of model congruent evaporation temperature is in accordance with experiment.

GaAs nanowhisker growth according to vapor-liquid-solid mechanism was realized on the basis of the lattice Monte Carlo model. Different solubility of Ga and As atoms in Au drop was taken into account in the model. Nanowhisker growth on GaAs(111)B surface activated by golden drops was demonstrated.

The process of Si-Ge heterostructures formation in nanowhiskers (NWs) grown by the vapor-liquid-solid mechanism was investigated using Monte Carlo simulation. It was demonstrated that it is impossible to grow atomically abrupt axial heterojunctions via classical vapor-liquid-solid mechanism due to gradual change of catalyst drop composition when switching the fluxes. Dependences of Ge x Si 1–x composition in transition region on the ratio of germanium and silicon fluxes and deposition duration were investigated. The width of Si-Ge axial heterojunction was found to be dependent on NW diameter d. In adsorption-induced growth mode the width has linear dependence on d and in diffusion-induced growth mode it is either constant (when growth rate ∼1/d) or proportional to 1/d (when growth rate ∼1/d2).

Silicon nanowhisker (NW) growth was investigated by Monte Carlo simulation. Dependence of NW growth rate on radius R was obtained. Growth rate was found to be proportional to 1/R2 for diffusion growth mode and radius independent for adsorption mode.

The dependence of nanowhisker morphology on growth conditions was studied by Monte Carlo simulation. Areas of growth conditions of filled and hollow nanowhiskers (nanotubes) were found. The area of inside dimension of nanotubes was shown to rise with increasing of flux.