arXiv subjects

A. N. Chaika

Publications and source records attributed to A. N. Chaika.

6 recordsLinked to original sources

arXiv2026

Period-dependent suppression of Fourier peaks for topography images: Analysis of periodicity of triple-step arrays on vicinal Si(h h m) surfaces

Reliable determination of the periodicity of multiatomic steps on high-Miller-index vicinal surfaces is often complicated by (i) the presence of relatively narrow terraces tilted at large angles relative to the scanning plane, and (ii) unavoidable distortions in the lateral direction resulting from creep and improper calibration of a piezo scanner. We argue that the period of the triple-step arrays on vicinal Si(5\,5\,6) and Si(5 5 7) single-crystal wafers can be determined from raw scanning tunneling microscopy data, without preliminary corrections, with precision approaching the interatomic distance. We demonstrate that the intensity of the Fourier peaks of the differential maps, derived from raw topography images by the difference-of-Gaussians approach, strongly depends on the period of the ordered triple-step arrays. This suppression of the ninth Fourier peak indicates that the regular array of triple steps has a period of $18b=5.99$ nm in projection onto the Si(1 1 1) terrace plane, where $b=0.333$ nm is the distance between atomic rows of the $1\times 1$ lattice in the $[\bar{1}\,\bar{1}\,2]$ direction. This means that the nominally (5\,5\,7)-oriented Si wafers may correspond locally to the Si(8 8 11) orientation. The method can be applied to the precise analysis of other vicinal surfaces with narrow and wide terraces containing an integer number of Si(1 1 1)$7\times 7$ unit cells.

cond-mat.mtrl-sci↗

arXiv2026

Atomically precise triple-step staircase on a vicinal silicon surface: Is it Si(5 5 7), Si(7 7 10) or Si(8 8 11)?

Scanning tunneling microscopy studies of periodic arrays of triple steps fabricated on single-crystalline Si(5 5 7) wafers demonstrate several possible atomic structures of consecutive steps and Si(1 1 1) terraces maintaining the same periodicity on micrometer-sized surface areas. Detailed analysis of the atomically resolved data reveals the formation of Si(8 8 11) triple-step staircase with a period of 18b=5.99 nm in projection onto the terrace plane, where b=0.333 nm is the distance between atomic rows for the Si(1 1 1)1x1 surface. Schematic models for several possible configurations of either 7x7 or 5x5-reconstructed terraces and triple steps are proposed.

cond-mat.mtrl-sci↗

arXiv2024

Effective removal of global tilt from topography images of vicinal surfaces with narrow terraces

The main feature of vicinal surfaces of crystals characterized by the Miller indices (hhm) is rather small width (less than 10 nm) and substantially large length (more than 200 nm) of atomically-flat terraces on sample surface. This makes difficult to apply standard methods of image processing and correct visualization of crystalline lattices at the terraces and multiatomic steps. Here we consider two procedures allowing us to minimize effects of both small-scale noise and global tilt of sample: (i) analysis of the difference of two Gaussian blurred images, and (ii) subtraction of the plane, whose parameters are determined by optimization of the histogram of the visible heights, from raw topography image. It is shown that both methods provide nondistorted images demonstrating atomic structures on vicinal Si(556) and Si(557) surfaces.

cond-mat.mtrl-sci↗

arXiv2024

Visualization of Atomic Structures on Faceted and Nonflat Surfaces by the Difference-of-Gaussians Approach

Detailed analysis of scanning probe microscopy (SPM) data acquired for faceted and non-flat surfaces is usually complicated due to the presence of a large number of surface areas tilted by large/variable angles relative to the scanning plane. As a consequence, standard methods of elimination of global or local slopes by either a plane subtraction or numerical differentiation seem to be ineffective. We demonstrate that a simple difference-of-Gaussians procedure provides output data corresponding to projection of a considered surface onto the scanning plane without undesirable contrast modifications. This method allows us to suppress small-scale noise, minimize effects of finite slopes in the SPM images along both fast and slow scanning directions and removes surface ripples without active participation of the operator. This method can be applied for fast on-the-fly visualization of experimental data, and for more detailed analysis, including high-precision determination of lattice parameters and angles between translation vectors for surface reconstruction of different terraces or surface domains. In order to estimate geometrical distortions introduced by our procedure, we compare the results obtained by the difference-of-Gaussians approach for the tilted surfaces with direct image rotation in 3D space.

cond-mat.mtrl-sci↗

arXiv2018

Anomalous behavior of the electronic structure of (Bi$_{1-x}$In$_x$)$_2$Se$_3$ across the quantum-phase transition from topological to trivial insulator

Using spin- and angle-resolved spectroscopy and relativistic many-body calculations, we investigate the evolution of the electronic structure of (Bi$_{1-x}$In$_x$)$_2$Se$_3$ bulk single crystals around the critical point of the trivial to topological insulator quantum-phase transition. By increasing $x$, we observe how a surface gap opens at the Dirac point of the initially gapless topological surface state of Bi$_2$Se$_3$, leading to the existence of massive fermions. The surface gap monotonically increases for a wide range of $x$ values across the topological and trivial sides of the quantum-phase transition. By means of photon-energy dependent measurements, we demonstrate that the gapped surface state survives the inversion of the bulk bands which occurs at a critical point near $x=0.055$. The surface state exhibits a non-zero in-plane spin polarization which decays exponentially with increasing $x$, and that persists on both the topological and trivial insulator phases. Its out-of-plane spin polarization remains zero demonstrating the absence of a hedgehog spin texture expected from broken time-reversal symmetry. Our calculations reveal qualitative agreement with the experimental results all across the quantum-phase transition upon the systematic variation of the spin-orbit coupling strength. A non-time reversal symmetry breaking mechanism of bulk-mediated scattering processes that increase with decreasing spin-orbit coupling strength is proposed as explanation.

cond-mat.mes-hall↗

arXiv2001

Superconductivity in the Re-B system

Superconductivity was found for a rhenium boride Re3B at Tc=4.7 K and for ReB2 with Tc in the range from 4.5 to 6.3 K depending on the boron concentrations. Both compounds have the structure different from that of the simple layered diborides, in particular from MgB2.

cond-mat.supr-con↗