Conicity of latent tracks in the near surface region as a factor affecting the correct evaluation of track size

Abstract

AbstractThe difference in track parameters recorded in some oxides at the same energy loss and different ion velocity, the so called “velocity effect”, have been corroborated by various experimental methods. Most of the corresponding data on damage cross section and then on the track radii were found by means of indirect techniques such as Rutherford backscattering spectroscopy in channelling geometry. The contribution of transmission electron microscopy results in the whole data array remains very limited. In this report we present an analysis of existing TEM results related to the “velocity effect” and consider how the conical shape of latent tracks observed in the subsurface region of swift heavy ion irradiated oxides may affect the correct determination of the track size as well as the critical electronic energy loss for track formation. The discussion is based on our cross sectional TEM studies of high energy Bi and Xe ion induced latent tracks in TiO2 and Al2O3 single crystals. To our knowledge there have been no reported cross sectional TEM analyses on Y3Fe5O12, Bi4Ge3O12 and YBa2Cu3O7‐δ in order to verify the cylindrical track assumption. If similar conicity exists in the near surface regions of these materials it may cast some doubt on the validity of the velocity effect. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)