Effects of high-energy ion implantation into metals

The laws and features of the formation of phase-structural states and defect formation during high-energy (E 100 MeV) ion implantation are reviewed. We consider the salient feature of such action in solids, namely, strong electron excitations in the solids and, therefore, the dominant value of electron stopping of ions; formation of buried tracks; and abrupt increase in the role of electron excitations in the generation of structural defects. High-energy and multiple-energy implantation is shown to be effective in modifying the physicomechanical properties of solids because of the formation of deep-lying doped layers and the considerable thickness of the ion-modified surface layer of the target.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 23–40, May, 1994.     

Charge accumulation by insulators irradiated with electrons

A model, more general than the existing ones, is proposed for the accumulation of charge by plane-parallel insulators irradiated with accelerated electrons. The model takes into account the spatial distribution of the charge injected by the irradiation and the coordinate and time dependence of the bulk electrical conductivity; it is valid for different boundary conditions imposed on the solution of the Poisson equation. The charge density distribution obtained by the light probe method in a sample of a lithium fluoride single crystal irradiated with 2-MeV electrons and current density 5·10^–4 A/m² is described qualitatively by the model.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 49–57, February, 1981.     

Release of a diamond-like film on a nickel surface irradiated simultaneously with carbon ions and electrons

Nickel samples at temperatures of 300–1000°C have been irradiated simultaneously with 10-to 30-keV C⁺ ions and 1-to 5-keV electrons. The release of implanted carbon atoms on the surface of a sample with the formation of a transparent carbon film with the prevailing sp ³ hybridization has been observed. The thickness of the film is several tens of nanometers. The formation of films is attributed to the acceleration of the formation of carbon structures in samples irradiated by accelerated electrons.     

High dose iron implantation into silicon and metals

High dose implantations of Fe into metals and semiconductors have been performed with beam energies up to 1 MeV at the UNILAC-injector at GSI. Unusual high concentrations of 70 atomic % for Si and 20 atomic % for Cu have been obtained, with doses of 10¹⁸ Fe/cm² in the case of Si and several 10¹⁷ Fe/cm² in the case of Cu. For Si the thickness of the layers were determined by Rutherford backscattering to be 4500 Å. These results are consistent with calculations, which show that these high concentrations are due to the reduction of the sputter yield at the relative high particle energies. Samples have been characterized using several complementary methods (Mössbauer Spectroscopy (MS), Rutherford Backscattering Spectroscopy (RBS), Auger electron Spectroscopy (AES). Scanning Electron Microscopy (SEM), X-ray diffraction (XRD)).     

Ion implantation

Some developments in applications of Mössbauer spectroscopy to investigate ion-implanted radioactive source isotopes in solids are presented. Emphasis is layed on impurity and defect studies in metals and semiconductors. The particular role of Mössbauer spectroscopy in comparison to and in combination with other analytical techniques is illustrated. Recently developed on-line implantation techniques are described, their merits and prospects are discussed.     

Ion implantation

The extreme sensitivity of Mössbauer Spectroscopy to the local atomic and electronic configuration around ion implanted Mössbauer probes is demonstrated in a number of recent defect configuration studies in semiconductors and metals. A surge of interest is observed towards Mössbauer studies on high dose implantations connected with materials research: recent studies are reviewed dealing with ion beam synthesis, ion beam modification and ion beam mixing of materials.     

Ion implantation into fused quartz for integrated optical circuits

Results obtained in the fabrication of slab and strip waveguides by ion implantation into fused quartz are discussed. Using a step-index waveguide model the increase in refractive index is calculated. The optical loss is smaller than 1 dB/cm at λ = 568 nm without annealing. The properties of strip waveguides fabricated by ion implantation through photoresist masks of thicknesses from 0.4 μm to 0.8 μm are described. A bright fluorescence is observed with emission at 530 nm and 640 nm and its dependence on ion fluence and ion energy is measured.     

Relaxation processes on A ZnO surface irradiated by electrons

The dependence of effective charge carrier lifetime and the surface conductivity relaxation constant of polycrystalline zinc oxide as functions of electron irradiation dosage at constant residual gas pressure, partial oxygen pressure at constant irradiation dosage, and partial water vapor pressure at constant irradiation dosage are studied. Surface state types and the charge carrier relaxation mechanism are determined.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 81–85, June, 1985.     

Third harmonic generation by hot electrons in metals

The weak nonlinear response of a metal to the action of low-intensity laser radiation was studied under the normal skin-effect conditions. We have shown that temperature variations with a double frequency emerging during the electron heating lead to the generation of the third harmonic of the fundamental wave. The density of the radiation flux at the tripled frequency was calculated. By measuring this flux one can determine the frequency of the electron-electron collisions with the umklapp of the quasimomentum. Talk presented at the oral issue of J. Russ. Laser Res. dedicated to the memory of Professor Vladimir A. Isakov, Professor Alexander S. Shumovsky, and Professor Andrei V. Vinogradov held in Moscow February 21–22, 2008.     

Electrophysical properties of InSb irradiated by electrons at 300 K

Results of a comparative investigation of InSb crystals irradiated by electrons (1 MeV, 300 K), doped metallurgically (Te, Zn) and by nuclear transformation (Sn), are presented. It is found that as a result of irradiation the Fermi level shifts to a position near (E_c - 0.03) eV (at 77 K), independently of the material type. Subsequent annealing of the irradiated crystals revealed an n-p-n-p conductivity-type conversion in weakly doped n-InSb and an n-p conversion in strongly doped n-InSb.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 99–103, July, 1991.     

Inelastic light scattering by electrons and plasmons in metals

The cross section of the inelastic light scattering by electron-hole plasma in metals is studied. The Coulomb interaction of electron excitations is taken into account self-consistently. The system of the Boltzmann equation for electronic fluctuations and Maxwell’s equations for the interaction field is solved. The Raman spectra consist of the electron-hole background, diffuson and plasmon resonances. The widths of this background and resonance are determined by the electron collision rate as well as by the decay of the incident and scattered radiation in the metal. The line shape depends on the screening of the electron-light interaction, i.e., on the incident radiation frequency. Zh. éksp. Teor. Fiz. 112, 679–689 (August 1997) Published in English in the original Russian journal. Reproduced here with stylistic changes by the Translation Editor.     

The anisotropic scattering of electrons by dislocations in metals

The kinetic equation for the case of anisotropic scattering of electrons by dislocations is written in the form of coupled algebraic equations for the expansion coefficients of the distribution function in spherical harmonics. The electrokinetic coefficient tensor is obtained for the case of arbitrarily oriented external fields. Departures from Matthiesen's rule due to anisotropy of the scattering process are obtained.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 80–85, March, 1977.     

Ion implantation of sulphur into GaAs,GaP and ge monocrystals

The possibility of using ion implantation to form high concentration junctions in semiconductors has been explored for the specific case of sulphur in GaAs, GaP and Ge. The effects of ion dose, ion energy, crystal orientation and target temperature have been investigated by means of radiotracers and sectioning techniques.

It is shown that high concentration junctions can be formed using an incident ion having high electronic stopping cross-section and implanted along the <110< channeling directions of the crystals. A large increase in junction concentration may be obtained when the GaAs and GaP crystals are maintained at 150 °C during the implantation process, but this is not the case with Ge. Rutherford back-scattering of 1 MeV He⁺ ions has been used to measure the ion-bombardment induced damage in the crystals and to show how this damage can be annealed by heating the crystal during the implantation. The annealing, at temperatures up to 150 °C, is most effective in GaAs and least effective in Ge.     

Conductivity compensation and deep traps in epitaxial n-GaAs irradiated by electrons

A study has been made of electrophysical properties and deep traps in epitaxial n-GaAs grown by the chloride method and irradiated by electrons in the temperature range (20–500)°C. It is shown that the natural conductivity of GaAs is attained at irradiation temperatures of 20°C due to the introduction of E traps, and for 300°CT_irr500°C of high-temperature P traps, presumably defect clusters.V. D. Kuznetsov Siberian Physicotechnical Institute at the State University, Tomsk. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 57–60, October, 1992.     

Structural and composition changes in superconducting ceramics locally irradiated by electrons

The structural changes and the cation and anion compositions of the surface of superconducting YBa₂Cu₃O_7−x and Tl₂Ba₂CuO_6+x ceramics after local irradiation for several seconds by an electron probe with an accelerating voltage of 25 kV and a current exceeding 10⁻⁷ A are investigated by secondary-electron emission and by cathodoluminescence and x-ray microanalysis in a scanning electron microscope. Morphologically altered regions are detected in the irradiation epicenter, where the structure, chemical composition, and phase composition of the original compound are completely lost. In the intermediate zone between the epicenter and the periphery a distribution of the secondary emission yield is observed with a complex character that differs for the yttrium and thallium ceramics, and anomalies appear in the cathodoluminescence spectra. The experimental data are interpreted on the basis of ideas of oxygen losses under the direct influence of the electron probe and related electronic processes in superconductors. Fiz. Tverd. Tela (St. Petersburg) 39, 452–456 (March 1997)     

Confinement of electrons in layered metals

We analyze the out of plane hopping in models of layered systems where the in-plane properties deviate from Landau's theory of a Fermi liquid. We show that the hopping term acquires a nontrivial energy dependence, due to the coupling to in-plane excitations, and the resulting state, at low temperatures, can be either conducting or insulating in the third direction. The latter is always the case if the Fermi level lies close to a saddle point in the dispersion relation.     

Energy of electrons emitted by the laser-heated surface of metals

A method is proposed for determining the energy of emitted electrons by the time of electrons flight between electrodes. This method is based on measuring the duration of the current pulse induced by electrons in the measuring circuit. The measured value of the electron energy ≈0.25 eV is the evidence of the thermal character of emission.     

Excitation of acoustic waves in metals by electrons and protons

A study of the excitation of acoustic oscillations in metals by electrons and protons is described. For thin metal plates, the amplitude of the electric signal is independant of the energy of the electrons and is proportional to the ionization losses of the charged particles. The dependence of the amplitude of the acoustic signal on the energy of the incident electrons and protons is considered and a comparison between the Cherenkov radiation, thermoelastic, and dynamic models is made.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 72–76, October, 1973.The authors thank I. A. Grishaev, I. I. Zalyubovskii, V. V. Petrenko, M. F. Lomanov, L. L. Gol'din, and Ya. L. Kleinbok for constant help in carrying out this work and to V. T. Lazurik-Él'tsufin for useful discussions.