ELECTRIC FIELD DEPENDENCE OF NET ACTIVATION ENERGY FOR MIGRATION OF IONIC SPECIES ACROSS AN ACTIVATION BARRIER

The question of the functional form of the net activation energy, W(E), for the field assisted migration of ionic defects across an activation barrier is examined particularly with regard to the representation of W(E) as a power series in the field strength, E. The contribution to the coefficient of E2 in such a series made by each of four different effects, was estimated and the estimates compared with empirical values obtained from an analysis of L. Young's data for the anodic oxidation of Ta and Nb. All four effects examined could conceivably make a significant contribution to the empirical coefficient, although the dominant effect is probably that arising from a shift of the positions of maximum and minimum energy for the mobile defect brought about by the field. The influence of the choice of the form of W(E) on the empirical values for the zero field activation energy and activation dipole is also examined. © 1969.