Channeling Studies in Diamond-Type Lattices

The channeling characteristics of protons and helium ions in various diamond-type lattices (diamond, Si, Ge, GaP, GaAs, and GaSb) have been studied by means of Rutherford backscattering in the 0.5-2-MeV range. Critical angles (${\psi }_{\frac{1}{2}}$) and minimum yields (${\chi }_{min}$) have been measured and compared to theory. The values of ${\psi }_{\frac{1}{2}}$ for axial channeling have a functional dependence which agrees well with calculations based on the average potential along the row—both for uniform and for nonuniform spacing and (in the case of the compound semiconductors) for mixed atomic composition. However, the measured values are ≈ 25% lower in absolute magnitude. Planar critical angles show a faster attenuation with decreasing planar spacing than predicted, but in other aspects agree with theory. In the compound semiconductors, the orientation dependence of backscattering and of x-ray yields has been used to investigate simultaneously the interaction of the beam with both atomic species in the lattice. For those directions along which the different atomic species lie on separate rows (e.g., $〈110〉$), each row steers the incident particles in a manner described by the average potential of that row.