Sergey Filimonov

• PhD
• Dean at National Research Tomsk State University

Transient precursor states are often experimentally observed for molecules adsorbing on surfaces. However, such precursor states are typically rather short-lived, quickly yielding to more stable adsorption configurations. Here we employ first-principles calculations to systematically explore the interaction mechanism for benzene derivatives on meta...

Mechanisms of the step permeability are studied theoretically with the use of a simple terrace-edge-kink model of atomic events at the step edge. The model takes into account the essential details of the potential relief for adatoms at the step including possible asymmetry of the relief arising from the Ehrlich–Schwoebel barrier or/and the differen...

The absolute surface energies of three major low index surfaces of cubic silicon carbide (3C-SiC) are determined by first-principles density functional theory calculations. Calculations show that among clean 3C-SiC surfaces the Si-terminated 3C-SiC(001)-(3x2) surface has the lowest energy. The second and third lowest energy surfaces are the Si-term...

Nucleation of two-dimensional (2D) islands on reconstructed surfaces might involve formation of metastable nonepitaxial clusters as precursors for 2D islands. Being a thermally activated process the transformation of nonepitaxial clusters to epitaxial 2D islands might become a rate limiting step of the nucleation process at low deposition temperatu...

Models of adatom surface diffusion and incorporation at the sidewalls of nanowires and 3D islands are proposed. The models account for the presence of an atomic step on the sidewall facet and for the adatom transport from the substrate to the sidewall. Peculiarities of the potential relief for migrating adatoms as well as the effect of step permeab...

At the nanoscale, molecular electronics have the potential to far outperform traditional silicon-based devices. However, despite extensive studies, incorporating single molecules into the design of integrated circuits remains a great challenge. A central difficulty is poor control of the contact state between molecule and metal electrode, which may...

A kinetic model of the formation of pyramid-like bulges (pedestals) at the bases of vertical nanowires is proposed. The formation of the pedestals at the early stage of the nanowire growth is assumed to be induced by a higher nucleation rate of two-dimensional islands under the catalyst droplet, as compared to the nucleation rate at the non-activat...

The design of novel elementary surface processes is important for applications in catalysis, single-molecule junctions, molecular sensors, switches and surface mounted molecular machines. Here we demonstrate by van der Waals inclusive density functional theory calculations that a small and relatively simple heteroaromatic compound s-triazine (C$_3$...

A model of radial growth of vertically aligned nanowires (NW) via formation and propagation of monoatomic steps at nanowire sidewalls is developed. The model allows to describe self-consistently the step dynamics and the axial growth of the NW. It is shown that formation of NWs with an abrupt change of wire diameter and a non-tapered section at the...

A model is proposed for desorption of molecules via a precursor state in the presence of two distinct chemisorption states on the surface. Analytical expressions describing the temporal evolution of the concentration of molecules in chemisorbed states are obtained. It is shown that redistribution of molecules between the chemisorbed states can lead...

We present results of computer Monte Carlo simulations of the formation of adsorption layers composed of noninteracting molecules of benzene, anthracene, and pentacene on the Ag(111) surface. The dependences of the chemical potential of the molecules on the density of the molecular layer (surface coverage) are obtained. By means of the thermodynami...

Formation of epitaxial graphene (EG) on 3C–SiC films heteroepitaxially grown on Si substrates, otherwise known as graphene-on-silicon (GOS) technology, has a high potential in future nanocarbon-based electronics. The EG's quality in GOS however remains mediocre due mostly to the high density of crystal defects in the 3C–SiC/Si films caused by the l...

Detailed analysis on the planar defects in rotated 3C-SiC() films grown on Si(110) substrates have been conducted by using X-ray diffraction and cross-sectional transmission electron microscopy. While the film mostly consists of a rotated region, a portion was found in its nonrotated (3C-SiC(110)) configuration, forming domain boundaries in between...

Low-temperature (~1073 K) formation of graphene was performed on Si substrates by using an ultrathin (2 nm) Ni layer deposited on a 3C-SiC thin film heteroepitaxially grown on a Si substrate. Angle-resolved, synchrotron-radiation X-ray photoemission spectroscopy (SR-XPS) results show that the stacking order is, from the surface to the bulk, Ni carb...

Radial growth of vertically aligned nanowires involves formation and propagation of monoatomic steps at atomically smooth nanowire sidewalls. Here we study the step dynamics with a step flow model taking into account the presence of a strong sink for adatoms at top of the nanowire and adatom exchange between the nanowire sidewall and surrounding su...

Results of investigations of the SiC/Si growth from monomethylsilane are reported. Growth conditions favoring the rotated epitaxy of 3C-SiC(111) films on Si(110) are determined experimentally. Surface energies of clean and hydrogen covered 3C-SiC(110) and 3C-SiC(111) surfaces are calculated with the density functional theory approach. It is shown t...

We have focused on stress measurements during Bi termination of Si (111) and Ge growth on this Bi-mediated Si (111). In order to obtain information on both the surface stress and the surface structure simultaneously, we have combined the surface-curvature and the reflection-high-electron-energy-diffraction instrumentations in an identical ultrahigh...

The understanding of electronic properties of complex organic/metal interfaces requires a reliable method for the prediction of their structure and stability. The bonding at complex interfaces arises from delicate balance between covalent bonds, van der Waals (vdW) forces, charge transfer, and Pauli repulsion. We developed a method based on density...

3C-SiC is the only polytype that grows heteroepitaxially on Si substrates and, therefore, it is of high interest for various potential applications. However, the large (~20 %) lattice mismatch of SiC with the Si substrate causes a serious problem. In this respect, rotated epitaxy of 3C-SiC(111) on the Si(110) substrate is highly promising because i...

In the formation of epitaxial graphene on Si substrates, the growth of high-quality 3C-SiC thin films on Si substrates is a key to success. As a solution to the large mismatch between the Si substrate and the 3C-SiC film, rotated epitaxy in which 3C-SiC(111) films are grown on Si(110) substrates is quite attractive. In some applications, on the oth...

Selective adsorption of C60 on nanoscale Ge areas can be achieved, while neighboring Si(111) areas remain uncovered, if the whole surface is initially terminated by Bi. Fullerene chemisorption is found at Bi vacancies which form due to partial thermal desorption of the Bi surfactant. The growth rate and temperature dependence of the C60 adsorption...

In the context of the simple growth model of two level pyramids consisting of 2D islands, we examine the incipient transition from 2D to 3D growth. It is shown that the characteristic time of transition to 3D growth can depend nonmonotonically on temperature. Under high temperatures, the formation of 3D islands is caused by atoms detaching from the...

Kinetics of the step flow growth on the (16×2) reconstructed Si(110) surface has been studied experimentally and with computer simulations. It is shown that during Si growth under DC heating vicinal steps on the (16×2) reconstructed Si(110) surfaces undergo a kinetic step bunching and develop extended segments preferentially oriented along the (16×...

Temperature dependence of the growth rate of 3C-SiC films on Si(001) during ultralow-pressure chemical vapor deposition (ULP-CVD) using monomethylsilane is reported. At low temperatures the growth rate is high and thermally activated, but a drastic drop of the growth rate occurs at a critical temperature T-c. Another characteristic temperature T-ce...

This chapter recalls some basic concepts required for understanding crystal growth. Thermodynamics and kinetics of the crystallization process are considered and an atomistic picture of the fundamental surface processes is given. Basic mechanisms of kinetic growth instabilities in epitaxial growth are described. Finally, an overview of the strain r...

Temperature dependence of the growth rate of 3C-SiC(001) films on Si(001) substrates during ultralow-pressure (ULP: ~10-1 Pa) CVD using monomethylsilane has been investigated in detail by using pyrometric interferometry. A novel behavior, i.e. a sharp division of the growth mode into two regimes depending on the growth temperature, has been found t...

The nucleation and growth of compact two-dimensional islands having a regular shape and edges consisting of atomically straight kink-free segments is studied analytically and with kinetic Monte Carlo (KMC) simulations. In the analytical model the islands grow by a cyclic process of deposition of single atomic rows along the island edges. Two ends o...

Nucleation of 2D islands in Si/Si(111)-7×7 molecular beam epitaxy is studied using scanning tunneling microscopy (STM). A detailed analysis of the population of small amorphous clusters coexisting on the surface with epitaxial 2D islands has been performed. It is shown that small clusters tend to form pairs. The pairs serve as precursors for 2D isl...

The submonolayer density of two-dimensional (2D) islands in Si∕Si(111)-7×7 molecular beam epitaxy is measured using scanning tunneling microscopy. At a relatively low deposition temperature of 673 K, the density of 2D islands is a power function of the deposition flux N2D∝Fχ with the exponent χ=0.24 being smaller than that predicted by the standard...

The chemical contrast between Si and Ge obtained by scanning tunneling microscopy on Bi-covered Si(111) surfaces is used as a tool to identify two vertical Ge/Si intermixing processes. During annealing of an initially pure Ge monolayer on Si, the intermixing is confined to the first two layers approaching a 50% Ge concentration in each layer. Durin...

Adatom incorporation into the ``faceted'' steps bordering the 2D nanoislands is analyzed. The step permeability and incorporation coefficients are derived for some typical growth situations. It is shown that the step consisting of equivalent straight segments can be permeable even in the case of fast egde migration if there exist factors delaying c...

Surface undulations induced by interfacial misfit dislocations in the Ge/Si(1 1 1) films grown by conventional molecular beam epitaxy and by surfactant-mediated epitaxy with Bi as a surfactant have been analyzed using scanning tunnelling microscopy and elasticity theory. A comparison of the experimentally measured undulation patterns with patterns...

A simple analytical model of the mass-transport during the initial stage of Ge wetting layer formation on Si(111) is developed. The model considers growth of the multilevel Ge islands observed in recent STM studies as evolution of pyramids with two bilayer thickness. The pyramid steps flow together and, as a result, the multilevel island forms if t...

We study submonolayer island size distributions in the epitaxy of Si and Ge on the Si(111) surface with Bi as a surfactant. We show that sizes of Si islands at different growth temperatures scale to a standard scaling function that peaks at the mean island size. Size distribution of Ge islands demonstrates qualitatively different behavior: With the...

Steps on Si(0 0 1) surfaces which are initially not aligned along the high symmetry directions of the dimer reconstruction are observed, by scanning tunneling microscopy, to “rotate” toward [1 1 0] directions during Si growth. This step “rotation” occurs due to a faceting of the step edges. A theoretical analysis of adatom incorporation into the st...

The kinetic processes responsible for the step permeability in growth of coherently strained 2D islands are analyzed theoretically. The expressions for incorporation and step permeability coefficients are derived in the framework of the terrace-edgekink model. These expressions are used to obtain the upper and lower bounds for permeability of the s...

Statistics of second layer nucleation in heteroepitaxial growth is analysed theoretically. It is assumed that strain can influence the step permeability and atom detachment from two-dimensional (2D) islands. Both effects promote the island-on-island nucleation, however with increasing growth temperature the step permeability decreases, whereas deta...

Rearrangement of two-dimensional Ge and Si islands after coarsening on a laterally strain modulated Ge surface covered with a monolayer of Bi is studied by scanning tunneling microscopy. Spatial ordering of the islands with respect to the modulations of the strain field shows that the binding energy of Si atoms at strained Si islands is, unexpected...

Within the framework of the cell method, the statistics of nucleation on the vertex of a 2D island is analyzed considering the influence of elastic stresses on the bond energy of an atom in a disruption. It is shown that elastic stresses at high temperatures may decrease the nucleation time as the temperature increases and the growth rate decreases...

The effects of a small pre-coverage of the surface with surfactants are studied in the framework of the mean-field kinetic model. Blocking of kinks at the steps (the 2D island edges) is adopted as the main mechanism of the surfactant action. The concurrent consequences of blocking --- increased saturation nucleus density and increased concentration...

A combined simulation-analytical model is developed to describe the surface morphology evolution during molecular beam epitaxy. The effect of island number density on transition from one level growth to nultilevel growth has been studied. It is shown that decrease in the island number density (increase in the area per island) can involve such a tra...

A computer simulation model is developed to study the dopant incorporation and surface segregation during 2D islands growth in MBE. The model is based on the conservation equations, which account for elementary surface processes of doping, and the computer simulation of the islands growth. The simulation showed that the dopant climbing over the ste...

The kinetic model is developed to describe surface processes of delta�-doping during MBE growth occurring via the step-flow mode. The dopant surface coverage is assumed to be small. The analytical expressions are obtained for the delta�-doping pro�file broadening, the peak of the dopant bulk concentration Xd(t�) and the time t� at which the concent...

A kinetic model is developed to describe surface processes of delta-doping during MBE growth occurring via the step-flow mode. The dopant surface coverage is assumed to be small. Analytical expressions are obtained for the delta-doping profile broadening, the peak of the dopant bulk concentration X-d(t*) and the time t* at which the concentration X...

An imitation model of layered crystal growth from a molecular beam is presented which takes account of the random character of the formation of nuclei and the dependence of their growth rate on their mutual positions. The dependence of the form of the oscillations in the intensity of specular reflection of a fast electron beam on the nucleation rat...