The atomic structure of disordered ion tracks in magnesium aluminate spinel

Abstract

Atomic resolution transmission-electron microscopy (TEM) observations and analysis have been undertaken on magnesium aluminate spinel to understand the structure of ion tracks induced by swift heavy ions. A combination of TEM techniques, which includes high-resolution and bright-field (BF) imaging, and high angular resolution electron channeling spectroscopy (HARECXS) analysis, disclosed the atomic structure of ion tracks. Swift heavy ions induce cation disordering along the latent tracks for a widespread region of 10 nm in diameter, which is much larger than a strained region detected by BF diffraction contrast. A preferential migration of cations is induced from the tetrahedral to octahedral interstitial site at the core regions of ion tracks under a condition of higher electronic excitation of (dE/dx)e = 35 keV/nm.