A. I. Oreshkin

Stability of the quasicubic phase in the initial stage of the growth of bismuth films on Si(111)-7×7

We discuss the results of the scanning tunneling microscopy (STM) investigations and ab initio calculations of the structure and stability of the quasicubic Bi{012} film formed in the initial stage of the bismuth deposition on the Si(111)-7×7 surface at room temperature. Results of our STM experiments show that paired-layer Bi{012} film grows on top of the initially formed wetting layer, with the Si 7×7 lattice preserved underneath. The pairing of the layers in the {012} film leads to the substantial stabilization of the film when it consists of an even number of layers and only even-number layered Bi{012} islands are observed to be stable. The buckling of the atoms in the topmost paired layer induced by the relaxation of the film is evidenced by the high-resolution STM images.

Metallic glass electronic structure peculiarities revealed by UHV STM/STS

We present the results of ultrahigh vacuum scanning tunneling microscopy/spectroscopy investigation of metallic glass surface. The topography and electronic structure of Ni63.5Nb36.5 have been studied. A great number of clusters with size about 5–10 nm have been found on constant current scanning tunneling microscopy images. The tunneling spectra of normalized tunneling conductivity revealed the energy pseudogap in the vicinity of Fermi energy. For energy values above 0.1 eV the normalized tunneling conductivity changes linearly with increasing of tunneling bias. The obtained results can be understood within suggested theoretical model based on the interplay of elastic electron scattering on random defects and weak intra-cluster Coulomb interaction. The effects of the finite edges of electron spectrum of each cluster have to be taken into account to explain the experimental data. The tunneling conductivity behavior and peculiarities in current images of individual clusters can also be qualitatively analyzed in the framework of suggested model.

Effect of different impurity atoms on 1/fα tunneling current noise characteristics on InAs (110) surface

The results of UHV STM investigations of tunneling current noise spectra in the vicinity of individual impurity atoms on the InAs(110) surface are reported. It was found that the power law exponent of 1/fα noise depends on the presence of an impurity atom in the tunneling junction area. This is consistent with the proposed theoretical model considering tunneling current through a two-state impurity complex model system taking into account many-particle interaction.

Direct visualization of Ni-Nb bulk metallic glasses surface: From initial nucleation to full crystallization

This article is devoted to in situ investigation of the Ni-based bulk metallic glass structural evolution and crystallization behavior by scanning tunneling microscopy/spectroscopy. The possibility of different surface nanostructures formation is shown by annealing of an original bulk glassy alloy in ultra high vacuum. Atomic locations in these surface nanostructures are completely different from those formed according to Ni-Nb binary phase diagram in the bulk area of the sample. The validity of the results is also verified by transmission electron microscopy and nano-beam diffraction measurements.

Ag-induced atomic structures on the Si(110) surface

We report the results of STM investigation of the initial stage of Ag adsorption on an Si(110) surface. At 0.21 ML Ag coverage, the size and orientation of the unit cell correspond to the parameters of a 16 × 2 unit cell of clean Si(110) surface. With increasing of the Ag coverage up to 0.42 ML, the type of surface reconstruction changes to a 4 × 1-Si(110)-Ag structure.

Initial Stage of the Adsorption of Fluorofullerene Molecules on Si Surface

Spatially resolved images of an individual C60F18 fluorofullerene molecule on Si(100) − 2 × 1 surface have been obtained using scanning tunneling microscopy. Scanning tunneling microscopy results and ab initio calculations show that the fluorofullerene molecules interact with the Si(100) − 2 × 1 surface with F atoms pointing down towards the surface. The adsorption energy of a C60F18 molecule on Si(100) − 2 × 1 surface is ∼12.1 eV, which is much higher than the adsorption energy of the same molecule on Si(111) − 7 × 7 surface (6.65 eV). C60F18 molecules are located in the troughs in-between the dimer rows occupying the four-dimer site on Si(100) − 2 × 1 surface.

Scanning tunneling microscopy/spectroscopy study of adsorption of C60F36 molecules on the 7 × 7-Si(111) surface

Spatially resolved images of an individual C60F36 fluorofullerene molecules on Si(111)-7 × 7 surface have been obtained by means of scanning tunneling microscopy/spectroscopy (STM/STS). The presence of isomers with different symmetry (T, C3, C1) has been revealed in STM investigation of initial adsorption stage of C60F36 on silicon surface Si(111)-(7 × 7). The adsorbed fluorofullerene molecule can occupy any adsorption site of silicon surface (corner site, faulted half, unfaulted half) that indicates for strong molecule-substrate interaction. The HOMO-LUMO gap of the adsorbed C60F36 molecules have been estimated from current image tunneling spectroscopy (CITS) and z(V) with engaged feedback measurements. The value of HOMO-LUMO gap observed experimentally was 3 eV. The C60F36 molecules adsorption on Si(111)-(7 × 7) surface was stable and kept equilibrium configuration during several hours.

Epitaxial growth of C60 thin films on the Bi(0001)/Si(111) surface

The morphology and atomic structure of C60 fullerene films on the Bi(0001)/Si(111)−7 × 7 surface with different coverages have been studied by scanning tunneling microscopy and spectroscopy and low-energy electron microscopy in high vacuum. It is shown that the most favorable sites for nucleation of C60 islands are double steps and domain boundaries on the surface of epitaxial Bi film.

STM EVIDENCE OF DIMENSIONAL QUANTIZATION ON THE NANOMETER-SIZE SURFACE-DEFECTS

Abstract In the present work, STM/STS investigations of HOPG treated in remote Ar + and O 2 -plasma have been carried out. Nanopits with size range 10–300 A were observed. In the STS energy spectrum of HOPG with nanopits of size less than 100 A the appearance of a new energy spectrum connected with dimensional quantization was found. If two nanopits of this size are situated at the distance of 10–20 A, then the energy structures inside each pit are split into two new energy levels.

Ab initio electronic structure of the Ge(111)-(2 × 1) surface in the presence of surface vacancy. Application to STM data analysis

We present the results of ab initio modeling of Ge(111)-(2 × 1) surface in the presence of atomic vacancy in surface bilayer. We showed that simple crystal structure defect affects surface electronic structure to the extent comparable with the influence of doping atom. We demonstrated the strong difference of surface LDOS structure above surface defects of different kind. We have proved that spatial oscillations of LDOS exist around individual surface vacancy in the same tunneling bias range as in case of donor doping atom on Ge(111)-(2 × 1) surface.