V. M. Grabov

Atomic-force microscopy of bismuth films

The surface structure of bismuth films is investigated using atomic-force microscopy. The films are prepared through vacuum thermal evaporation on mica substrates, followed by annealing. It is established that the films have a block structure with the preferred orientation of the C3 axis perpendicular to the substrate plane. The C2 axes of the neighboring blocks predominantly have mutually opposite orientations. Upon annealing, the sizes of blocks with the C3 axis perpendicular to the substrate plane increase at the expense of a virtually complete disappearance of blocks with random orientations of the C3 axis and the coalescence of blocks with the same orientation. The size and configuration of the blocks are most clearly revealed upon preliminary treatment of the films in a diluted solution of the etchant. The results obtained are of interest for the interpretation of the data on the transport phenomena occurring in bismuth films.

Optimization of the Conditions for Vacuum Thermal Deposition of Bismuth Films with Control of Their Imperfection by Atomic Force Microscopy

The structure and defects of bismuth films prepared through vacuum thermal deposition on mica substrates under different conditions (deposition rates, substrate temperatures, temperatures and times of annealing) have been investigated using atomic force microscopy. The conditions are determined under which recrystallization occurs with increasing crystallite size during annealing, which provides a decrease in the degree of imperfection of the films and an increase in the mobility of charge carriers.

Galvanomagnetic properties of thin films of bismuth and bismuth–antimony alloys on substrates with different thermal expansions

Temperature dependences of the galvanomagnetic properties of films of bismuth and Bi100 – xSbx (x ≤ 12) on substrates with different temperature expansion coefficients were studied in the temperature range of 77–300 K. The block films were prepared through thermal deposition, and single-crystal Bi100 – xSbx were grown by zone recrystallization under a coating. It was found that the temperature expansion coefficient of a substrate substantially influenced the galvanomagnetic properties of Bi and Bi100 – xSbx films. Using the experimental data, the change in the charge-carrier concentration in the Bi and Bi100 – xSbx films on different substrates at 77 K was estimated.

Atomic-force microscopy of bismuth film defects decorated by oxidation

A method has been developed for revealing intercrystalline boundaries and mutual orientation of crystallites in bismuth films with the use of natural oxidation in combination with atomic-force microscopy. For bismuth films prepared through vacuum thermal evaporation on mica substrates, the block boundaries have been revealed, the sizes of blocks have been determined, and their mutual crystallographic orientation has been established. The results obtained have been used to determine thermal evaporation conditions that ensure a higher perfection of the film structure.

Mobility restriction of charge carriers in bismuth films due to film block structure

Electric properties of bismuth thin films on mica substrates depending on their structure and concentration of defects have been studied by atomic force microscopy. The obtained results allow optimization of the production of bismuth films with a structure close to single-crystal by thermal evaporation in vacuum.

Size effect in galvanomagnetic phenomena in bismuth films doped with tellurium

The results of experimental investigation of galvanomagnetic phenomena in single-crystalline and block films of tellurium-doped bismuth in the temperature range of 77–300 K and in the film-thickness range of 0.1–1 μm are presented. It is shown that the charge-carrier concentration in the investigated films is independent of thickness, the charge carriers are scattered at phonons, the film surface, structural defects, and crystallite boundaries. The values and ratio of the listed contributions to the restriction of charge-carrier mobility depend on the tellurium content, film thickness, and also their single-crystalline or block state.

Structure of bismuth films obtained using an array of identically oriented single-crystal bismuth islands preliminarily grown on a substrate

An array of identically oriented single-crystal bismuth islands formed on mica plates is used as a substrate to improve the structure of bismuth thin films grown by vacuum thermal evaporation. The array of islands is formed by the chemical etching of a single-crystal bismuth film 1 μm thick grown by floating-zone recrystallization under a coating. The structure of the obtained films is studied by X-ray diffraction, atomicforce microscopy, and electron backscatter diffraction scanning electron microscopy.

Electron-plasmon interaction in acceptor-doped bismuth crystals

By doping the semimetal bismuth, it is possible to equate a plasma-oscillation energy with a band gap at the L point of the Brillouin zone. In this case, modifications in the reflection spectra are observed. The analysis of experimental data shows that the plasmon excitation is an efficient mechanism of electron-hole recombination provided that ℏωp=EG.

Reflection Spectra of Doped Bismuth-Antimony Crystals in the Far-Infrared Region of the Spectrum

The plasma reflection spectra of the doped bismuth and bismuth-antimony alloyed crystals were studied experimentally at liquid-nitrogen temperature within a range of 30–600 cm−1. Specificities in the optical functions of the samples are revealed within the infrared range that lies on the low-frequency side of the plasma edge and coincides with the optical-phonon frequencies in bismuth. When the plasma frequency is approached, the character of the interaction of radiation with anisotropic electron-hole plasma changes considerably.

Magneto-optical study of bismuth at 80–280 K

Infrared transmission (λ=10.6 µm) of samples consisting of two symmetric plane-parallel halves of a Bi single crystal separated by a gap were studied in a pulsed magnetic field. Oscillations associated with interband optical transitions involving Landau levels were observed at 80–280 K. The temperature dependences of the energy gap, effective masses, and relaxation time of carriers were determined.