Dechanneling by stacking faults and dislocations

Abstract

Abstract The general features of dechanneling by lattice defects are briefly described. The dechanneling cross section of a defect A and the opacity of a crystal ω Rare defined. Stacking faults and dislocations are more specifically studied in the case of planar channeling. At a stacking fault, the potential valleys are shifted. The dechanneling cross section is shown to depend linearly on the distance of minimal approach da between channelons and planes. A measurement of A in the case of α-particles and stacking faults in Au then gives the following values for da and for x the dechanneling probability of channelons hitting a fault: Near dislocations the dechanneling is attributed to the distortion of the lattice. In a simple model where the channelon is supposed initially not to oscillate (E ⊥=0), the cross section A is found to have a E 1/2 b 1/2 NP −1/2 dependence; E is the energy of the channelon, b the Burgers vector of the dislocation and NP the atomic density of the channeling planes. An experimental determination of A with α-particles in A1 yields A = 140 Å/u.l. of dislocation to be compared with the theoretical value A = 175 Å/u.l.