Ion tracks formation through synergistic energy processes in strontium titanate under swift heavy ion irradiation: Experimental and theoretical approaches

Abstract

The primary motivation for studying ion-solid interactions and the responses of various materials to energetic irradiation is the fundamental necessity and importance to get a deeper understanding of how irradiation changes the lattice structures and physico-chemical properties of solid materials. Under the action of extreme electronic energy deposition induced by swift Kr17+, Ar12+ and Ni19+ irradiation, the formation mechanism of latent tracks with different damage morphologies in pristine and predamaged SrTiO3 crystals are analyzed utilizing experimental characterizations of the lattice damage and numerical calculations from the inelastic thermal spike model. In contrast to Ar12+ and Ni19+ irradiation, Kr17+ irradiation, with an ion energy of 2.35 MeV/u and electronic energy loss of 16.7 keV/nm, increased the lattice temperature of the pristine crystal to 3500 K, and via a subsequent rapid quenching process, discontinuous tracks including individual spherical defects and discontinuous cylindrical damaged zones were formed. The related damage morphology demonstrates the threshold value of the lattice-temperature change induced by irradiation for track production in pristine SrTiO3, which is fundamental and essential for comparing irradiating-ion velocities and electronic energy losses. Owing to the decrease in thermal conductivities and increase in electron-phonon coupling in Au+-irradiation-damaged SrTiO3, subsequent Si3+, Ar12+ and Kr17+ irradiation significantly increased the lattice temperature of predamaged crystals to greater than 3500 K, leading to discontinuous and continuous track production in the predamaged crystals. Thus, the pre-existing damage produced by nuclear energy loss interacted synergistically with the electronic energy loss and effectively enhanced the lattice-temperature increase and promoted track formation.