Yu. V. Bulgakov

Transparency oscillations of a silicon single crystal in passing from axial to planar channelling

Abstract The transparency coefficient, T, of thin (2.5μ) Si single crystals relative to a well collimated 8.16 MeV He ion beam has been measured as a function of angle or between the beam direction and the [110] axis of crystals rotated in the (110) plane. Curve T(α) has been found to display minima at α = 0.15°, 0.34° and 0.5°. Computer simulation of experimental conditions has shown that the first minimum is a result of competition of two processes: increase of the radius of ring-shaped angular distribution with increasing a and ion capture in the (110) planar channel. The remaining two minima are due to particle dechannelling from channel (110) resulting from resonance enhancement of transverse particle oscillations in the channel. Similar calculations have been carried out for the transition from axial [110] to planar (001) channelling. It has been shown that in this case the difference in the conditions resonance result in spatial separation of the ion beams that have passed through channels (001) wi...

The experimental determination of the impact parameter dependence of inelastic energy loss of channeled ions

Abstract Using the channeling technique, the impact parameter dependence of inelastic energy loss of fast He and N ions in Si has been measured.

The nature and distribution of radiation-induced defects in silicon along the range of protons and alpha particles

Abstract The variation in the resistivity of the n-type silicon along the range of protons and α-particles with an energy of 6.3 MeV/nucleon has been studied experimentally over a wide interval of irradiation doses. The initial rate of removal of majority carriers as a function of the distance from the surface of a sample has been determined. The spatial distribution of radiation-induced defects, resulting from elastic collisions between the incident particles and the silicon atoms and the subsequent cascade multiplication, has been calculated by a computer simulation technique. The nature of radiation-induced defects in silicon, which are stable at room temperature, has been examined on the basis of the data obtained, in various segments of the range of heavy charged particles. Both the point defects, containing impurity atoms of oxygen or phosphorus, and the defects proper, which contain no impurity atoms, have been shown to form in the cases under consideration. The relation of electrically active defe...

Resonance dechanneling of fast protons in axis-to-plane transitions in silicon

Abstract The transparency of a thin silicon single crystal to a beam of well-collimated protons with energies of 0.56 and 1.17 MeV has been measured for various axial-to-planar channeling transitions. For the [110]-(110) transition, resonance minima of transparency have been observed. From the position of these minima the average ionic charges in the crystal have been estimated.

The resonant dechanneling determination of the natural oscillation period for ions in planar channels

Abstract From the position of resonance minima on the transparency curve, the periods of natural oscillations of He ions trapped into the (110) planar channels in Si have been determined. The results of measurements indicate the interplanar potential anharmonicity and agree well with calculations based on the Moliere-Erginsoy potential.

Application of the impact parameter method to the channeled ion energy distribution calculation

Abstract Based upon an empirical dependence relating inelastic energy losses to the impact parameter of ion-atom collisions, a calculation of the energy distribution of He ions channeled in Si has been made.

Dechanneling of fast light ions

Abstract The dechanneling function has been obtained experimentally for helium ions with E = 7.15 MeV in axial 〈110〉 channel in Si. The experimental data on multiple scattering of channeled ions are compared to the theoretical calculations based on the Fokker-Planck kinetic equation. The main factors responsible for the escape of ions from planar channel have been found.