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

Energy loss, range, path length, time-of-flight, straggling, multiple scattering, and nuclear interaction probability: In two parts. Part 1. For 63 compounds Part 2. For elements 1 ⩽ Z ⩽ 92

A model is presented which allows planar-channeling data to be used to deduce the parameters of the interaction potential between the channeled ions and the atoms of the solid and which relates the stopping power of channeled ions to that of randomly directed ones. The analysis is based on the experimental observation of the proportionality between the stopping power and the transverse oscillation frequency of ions traversing the planar channels of thin crystal targets. It is applied to data on He, O, and I ions transmitted through the {111} and {100} channels of Au crystals and on H ions transmitted through the {111} and {110} channels of Si crystals. For both targets, the screening constants of the interaction potentials are in excellent agreement with recent Hartree calculations. The same potentials allow the calculation of random stopping powers from the channeling data which are in good agreement with observation, especially when account is taken of thermal vibrations of the lattice atoms.

Deduction of Interaction Potentials from Planar-Channeling Experiments

Cu, Pt, Ag, and Au were deposited on (100)-oriented ceramic substrates (SrTiO3, LaAlO3, and MgO). Over a wide range of temperatures (room temperature to 600 °C), Cu films were (100)-oriented and exhibited cube-on-cube epitaxy. Epitaxial Pt(100) films were obtained only at high temperature; oriented Pt(111) films were obtained at lower temperatures. Ag and Au were never obtained as purely (100)-oriented samples, although the amount of (100)-film increased with increasing temperature. Three-dimensional islands formed for all metals at higher temperatures, while flatter film surfaces developed at lower temperatures. At any given temperature, the surface roughness of films on SrTiO3(100) increased in the order Pt < Cu < Au < Ag. The variations in film structural characteristics are described well by considering the metals’ (i) surface/interfacial energies, (ii) surface energy anisotropies, and (iii) surface diffusion coefficients. Flat, epitaxial growth is promoted by low-energy interfaces, low surface energy anisotropies, and slow surface diffusion.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/6ABE76D5727A8C8E01D4BD7DC5C17561/S088429140009230Xa.pdf/div-class-title-crystal-orientation-and-surface-morphology-of-face-centered-cubic-metal-thin-films-deposited-upon-single-crystal-ceramic-substrates-using-pulsed-laser-deposition-div.pdf

Crystal orientation and surface morphology of face-centered-cubic metal thin films deposited upon single-crystal ceramic substrates using pulsed laser deposition

Charged particle energy loss has been calculated as a function of an impact parameter in a crystal. The quantum dielectric formalism is used when calculating the energy loss in the outer valence shell. Calculations have been carried out particularly for silicon including the zonal energy structure. Energy loss on inner electrons has been calculated in the semi-classical approximation and in the classical dipole approximation. The scope of applicability of the two approximations has been determined. The hyperchanneled particle energy loss to the loss in amorphous medium ratio has been calculated. This ratio is shown to display a peak a t particle velocities close to atomic velocities. Relation between energy loss and local electron density has been studied. Comparison with experiment is presented.

Energy loss of charged particles in crystals

The energy loss of protons channelled along the [001] direction in 500 A thick gold is analysed as a function of emergence angle. For a given emergence angle, the energy loss can be related to a particular path along the channel and, by applying Poisson's equation to the interatomic potential, to the local electron density. The small thickness of the samples used in the present investigation, compared to prior investigations, allows a relatively simpler and more unequivocal interpretation of the experimental data than previously possible. The relative variation in the stopping power due to channelling turns out to be much smaller than the variation in the local electron density, in satisfactory agreement with recent theoretical expectations (Bonsignori and Desalvo 1969). Also, our measurements distinguish between not too different approximations to the interatomic potential : Lindhard's potential yields agreement with experiment and Nielsen's does not.

Energy loss of protons channelling through very thin gold

A systematic analysis of the effect of some vacuum deposition conditions on the structure of (111) silver and gold epitaxial films has been carried out. For silver films deposited on mica continuity can be attained at a thickness of ∼ 1500 A, with a substratum temperature of 275 °C and a deposition rate of 40 A/s. Continuous gold films ∼ 250 A thick can be deposited on these silver films: the D.P. boundary density is minimized with a substratum temperature of ∼ 300 °C and a deposition rate lower than 1 A/s. These results show a substantial agreement with the current theories on the nucleation and growth of epitaxial films.

S. Petralia

Papers

Energy loss of protons channelling through very thin gold

Effects of vacuum deposition conditions on the structure of (111) epitaxial gold films

[111] Proton channeling in very thin gold crystals