I. P. Ivanenko

Features of the tunneling conductivity of two-dimensional ordered linear-chain carbon films

Two-dimensional ordered linear-chain carbon films with different thicknesses (50 and 500 nm) have been studied by the tunneling spectroscopy method. The oscillatory dependence of the differential conductivity of the studied structures has been found. The obtained results have been interpreted with the use of the model of the formation of the charge density waves on the regular bends of the structure of linear-chain carbon.

Formation of aluminum island films under electron irradiation of a sapphire surface

The present paper is devoted to experimental investigation of electron-stimulated desorption from a single-crystal sapphire surface. Using Auger electron spectroscopy metallization of the sapphire surface, the character of which is dependent on the electron beam parameters, is observed under low-energy electron bombardment,. Using atomic-force microscopy, images of metal island films with a diameter of 50–100 nm are obtained.

On the Energy Spectra of Secondary Ions Emitted from Silicon and Graphite Single Crystals

Secondary ion emission from silicon and graphite single crystals bombarded by argon ions with energies E0 varied from 1 to 10 keV at various angles of incidence α has been studied. The evolution of the energy spectra of C+ and Si+ secondary ions has been traced in which the positions of maxima (Emax) shift toward higher secondary-ion energies E1 with increasing polar emission angle θ (measured from the normal to the sample surface). The opposite trend has been observed for ions emitted from single crystals heated to several hundred degrees Centigrade; the Emax values initially remain unchanged and then shift toward lower energies E1 with increasing angle θ. It is established that the magnitude and position of a peak in the energy spectrum of secondary C+ ions is virtually independent of E0, angle α, and the surface relief of the sample (in the E0 and α intervals studied). Unusual oscillating energy distributions are discussed, which have been observed for secondary ions emitted from silicon (111) and layered graphite (0001) faces. Numerical simulations of secondary ion sputtering and charge exchange have been performed. A comparison of the measured and calculated data for graphite crystals has shown that C+ ions are formed as a result of charge exchange between secondary ions and bombarding Ar+ ions, which takes place both outside and inside the target. This substantially differs from the ion sputtering process in metals and must be taken into account when analyzing secondary ion emission mechanisms and in practical applications of secondary-ion mass spectrometry.

Electron-beam charging of dielectrics preirradiated with moderate-energy ions and electrons

The effects of charging of dielectric targets irradiated with moderate-energy electrons in a scanning electron microscope are examined. Considerable differences in the kinetics of charging of the reference samples and the samples preirradiated with ions and electrons are reported. These differences are attributed to the processes of radiation-induced defect formation in Al2O3 (sapphire) and SiO2 that are, however, dissimilar in nature. The contributions of surface structure modification and changes in the electrophysical parameters of the surface (specifically, the charge spreading effect) are revealed. Critical doses of irradiation with Ar+ ions and electrons inducing active defect formation in dielectric targets and critical values of internal charge fields producing a significant contribution to the temporal parameters of Al2O3 and SiO2 charging are determined.

Analysis of the Structure and Conductivity of Kinked Carbon Chains Obtained by Pulsed Plasma Deposition on Various Metal Substrates

Linear-chain carbon films with a thickness of order 100 nm were studied by tunneling spectroscopy. The oscillating dependence of the differential conductivity of the investigated structures is established. The results obtained are interpreted using a model of charge-density wave formation in regular structural kinks of carbon chains. The Raman spectra of the films are recorded. The simulated spectra of harmonic oscillations of polyines (–C≡C–)n and cumulenes (=C=)n of carbon films are theoretically compared.

Analysis of the Raman Spectrum of Kinked Carbon Chains Taking into Account the Model of Various End Groups

The Raman spectra of kinked carbon chains with a set of end groups composed of hydrogen, silver, and copper atoms are calculated. It is analyzed how end groups, as well as the positions of impurity atoms in the chain, affect shifts characterizing the main peaks of the harmonic vibrations of chemical bonds between carbon atoms in polyyne- and cumulene-like (respectively, (–C≡C–)n and (=C=)n) chains.

Structural features of carbon materials synthesized by different methods

This paper presents the results of investigations of three types of carbon structures synthesized by different methods, such as arc discharge plasma enhanced chemical vapor deposition of carbon in a magnetic field, chemical dehydrohalogenation of the poly(vinyl chloride)/poly(vinylidene chloride) precursor, and pulsed plasma ion assisted deposition. It has been found that the samples prepared by different methods have a common feature, i.e., the presence of three-dimensional clusters based on sp2- or sp3-bonds surrounded by quasi-one-dimensional carbon chains. It has been shown that the structure of carbon materials changes depending on the synthesis conditions.