Rzhanov Semiconductor Physics

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.

Si nanowhiskers (NW) morphology was studied by Monte Carlo simulation. It was found out that different substrate-seed wetting conditions can lead to growth of straight, curved or tube-like NWs. Initial substrate-seed interface orientation and orientation of growing NW sidewall facets determine growth directions of model NWs.

A new lattice Monte Carlo model of A III B V nanowire growth according to the vaporliquid-solid mechanism is suggested. The peculiarities of this model and the procedure of energy parameters estimation for the InAs system are described. The characteristics of InAs and GaAs self-catalyzed nanowire growth are obtained using the suggested model. A comparison of InAs and GaAs self-catalyzed nanowire growth characteristics using the suggested Monte Carlo model is performed.

High-temperature annealing of GaAs(111)A and GaAs(111)B substrates under Langmuir evaporation conditions was studied using Monte Carlo simulation. The maximal value of the congruent evaporation temperature was estimated. The congruent evaporation temperature was demonstrated to be dependent on the surface orientation and concentration of surface defects.

: Formation of quantum dots (QD's) during heteroepitaxial growth was investigated by Monte Carlo simulation. Shwoebel barriers for explanation of QD's growth kinetic were suggested. Two different barriers for hops to the upper and lower layers were introduced in our model. Ranges of these barriers for QD's formation were estimated.

Monte Carlo simulations of atomic processes on the surface of silicon nanochannel membranes during molecular-beam epitaxy and subsequent thermal oxidation are performed. It is demonstrated that silicon deposition on Si(001) wafers with 1–100 nm cylindrical pores results in constriction of channel inlets. The rates of reduction of the nanochannel diameter are estimated as functions of the wafer temperature, silicon deposition rate, and initial nanochannel diameter. Optimal conditions of silicon deposition on nanochannel membranes are determined: the wafer temperature of 250–450◦C and silicon flux intensity of 10−2 to 10 monolayers (ML) per second. Under these conditions, the rate of reduction of the nanochannel inlet diameter is 0.13–0.15 nm/ML, which allows membrane channel modifications over a wide range down to several nanometers. Simulations of nanochannel membrane oxidation in an oxygen flux shows that precise reduction of nanochannel inlet diameters down to complete sealing of ...

A kinetic Monte Carlo model of amorphous SiO x layers has been developed on the basis of a partially filled diamond-like lattice with allowance for different valences of silicon and oxygen. In the starting model layers of stoichiometric composition SiO 2 , about 50% of lattice sites are randomly occupied by silicon and oxygen atoms, which tend to form chains of vertex-sharing tetrahedra SiO 4 upon long-term model annealing. The amount of perfectly coordinated atoms reaches ~65% after short-term annealing and slowly increases with time, indicating the formation of a metastable state. In the most ordered final state, more than 90% of atoms are perfectly coordinated. The presence of excess silicon in SiO x layers increases the fraction of perfectly coordinated oxygen atoms up to 95%. As the SiO 2 matrix tends to the final ordered state, excess silicon atoms assemble to form nanoclusters.

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 GexSi1–xaxial 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: i...

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.

A c c e p t e d M a n u s c r i p t  Kinetics of GaAs(001) surface smoothing in equilibrium conditions is simulated.  The stages of step-terraced morphology formation are elucidated.  Monatomic step length and mean island size kinetics are compared with experiment.  The role of atom migration through the gas phase to smoothing is considered.  Diffusion activation, lateral bond and adatom desorption energies are estimated.

The process of metal droplet formation and motion during a high-temperature annealing under the Langmuir evaporation conditions is studied by Monte Carlo simulation. The nanosized droplet motion mechanism during a high-temperature annealing is suggested. The reason for the droplet motion is the lateral drop-crystal interface dissolution in a liquid metal. The movement direction is determined by the difference in the (111)A and (111)B crystal facet dissolution rates. The step movement deceleration near the droplet can be a cause of step bunching.

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.

High-temperature annealing of GaAs(111)A and GaAs(111)B substrates under Langmuir evaporation conditions was studied using Monte Carlo simulation. The maximal value of the congruent evaporation temperature was estimated. The congruent evaporation temperature was demonstrated to be dependent on the surface orientation and concentration of surface defects.

A kinetic Monte Carlo model of silicon nanocluster (Si-nc) formation during high temperature annealing of Si suboxide layers was suggested. The model takes into account, along with silicon and oxygen atom diffusion, the processes of silicon monoxide creation and dissociation. It was demonstrated that the presence of SiO in the system results in an increase of Si-nc critical nuclear size and can accelerate nanocluster growth. It was found that Si-ncs were formed only in the SiO x layer with x < 1.8. Three stages of Si-nc aggregation were revealed: silicon cluster nucleation, coalescence of neighbor Si-ncs, and slow enlargement of separately located clusters. Annealing of the SiO 2 film containing nonstoichiometric SiO x layers resulted in Si-nc or cavity formation depending on temperature. The type of the process was determined by ratio between SiO dissociation and evaporation rates.

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.