The motion of energetic charged particles inside a monocrystalline solid can be strongly influenced by channeling and blocking effects. The present article reviews the theory, the experimental studies, and some of the applications of these effects. The coverage of the published literature extends through June 1973.

Channeling and related effects in the motion of charged particles through crystals

Sputtering by ion bombardment theoretical concepts

Spike effects may influence sputtering and disordering of ion‐bombarded solids in the case of a high density of energy deposition and long lifetime. We estimate both quantities and find very pronounced variations with the atomic numbers of the projectile ion and target and the bombarding energy. The predicted energy range where sputtering should be affected is consistent with observed anomalies in the measured yield.

Energy density and time constant of heavy‐ion‐induced elastic‐collision spikes in solids

Surface science aspects of etching reactions

Collisions of atoms and ions with surfaces under grazing incidence

The energy spectra of atoms sputtered from a gold target have been measured as a function of ion energy and species for target temperatures in the range 100 to 1200°K. Both single crystal and polycrystal targets have been used, with surface topography monitored by a scanning electron microscope. The effect of raising the target temperature towards 1200°K is always to produce a low energy peak in the energy spectrum near 0.1 eV. This is found to have behaviour consistent with a thermal spike model, and at high temperature accounts for a large fraction of the total sputtering yield. The time-of-flight spectra show two peaks, one at about 10 eV the other at about 500 eV. The former was always present and when a crystal target was used with ejection along a axis it took on a kinked shape consistent with a contribution from focused collisions. The effect of increasing the temperature was to reduce this effect, presumably by thermal scattering of focused collisions. The 500 eV peak was also affec...

The energy distribution of sputtered atoms from gold

The Rutherford backscattering technique with 2 MeV He+ ions has been used to measure the range and range straggling of ions implanted into polycrystalline aluminium and amorphous silicon with energies from 20 keV to 250 keV. In aluminium the following ions were used: Cs+, La+, Pr+, Eu+, Tb+, Dy+, Ho+, Er+, Lu+, Hf+, Pt+, Au+, TI+, Pb+, Bi+. In silicon the ions were Sm+, Eu+, Gd+, Tb+ and Dy+. The data was converted into reduced range, energy and straggling coordinates ρ p∊ and γΔR p/Ř p respectively and graphs plotted against ∊ In the case of silicon the reduced data fell close to common curves approximated by ρ p = 1.46 ∊0.65 and γΔŘ p/Ř p=0.41 for 0.02 < ∊ < 0.24. In the case of aluminium the best fit was approximated by ρ P = 1.95 ∊0.60 and γΔŘ p/Ř p = 0.5 for 0.06 < ∊ < 0.35. The data for Ho+−Al, Au+−Al, Pt+−Si, Au+−Si and Bi+−Si deviated from the common curves over a range of energies. Calculations following the methods of Winterbon using Thomas-Fermi and Lenz-Jensen potentials produced two ...

Heavy ion ranges in aluminium and silicon

Helium ions of 275 keV have been scattered at glancing angles from the flat {110} surface of a tungsten single crystal. The angular distribution of the scattered particles in the plane of incidence...

The low angle scattering of 275 keV He+ ions from a tungsten crystal surface

Experiments are reported in which a finely collimated beam of protons were incident on a flat tungsten crystal or an amorphous WO3 surface, The yields of W (M shell) or O (K shell) X-rays were measured as a function of proton energy (150–275 keV) and orientation; also detected were the scattered protons and their energy spectrum. The observations are discussed in terms of channelling theory and projected motion in the plane transverse to the atomic rows. By a combination of analytical theory and computer simulation it is shown that in this plane the kinetic energy ψ2 E 1 and the direction of incidence β in should be the determining factors of yield and scattering. The observations bear this out and special two-dimensional processes can be identified such as trajectory focusing, quasi-planar channelling and surface semi channelling. Oxygen in the crystal surface is detected and shown to lie on a different lattice from the tungsten, to have a surface stoichiometry close to WO3 and to extend some 10...

Scattering, energy loss and X-ray production of protons of 150–275 keV at grazing incidence on tungsten crystals

Ions of hydrogen and helium incident at 275 keV have been scattered from a flat surface composed of amorphous tungsten oxide prepared by anodisation. Measurements of the angular distribution and the energy spectrum have been conducted for various angles of incidence and angles of scattering up to 5°. The observations are compared with the predictions of a plural scattering theory and good agreement is found. In particular, the most probable energy loss of the scattered ions is proportional to the scattering angle, the angular distribution of ions scattered with any particular energy loss is roughly a gaussian function truncated by the surface plane whilst the energy spectrum has nearly the predicted form of a skewed peak.

M. W. Thompson

Papers

The energy distribution of sputtered atoms from gold

Heavy ion ranges in aluminium and silicon

The low angle scattering of 275 keV He+ ions from a tungsten crystal surface

Scattering, energy loss and X-ray production of protons of 150–275 keV at grazing incidence on tungsten crystals

The low-angle scattering of energetic ions from an amorphous surface