Pixel mapping analysis to characterize long-range order interactions in crystals under ion irradiation

Abstract

High-dose irradiation can cause agglomeration of projectile particles if the impurity concentration exceeds a certain level. In previous classical molecular-dynamics calculations we have investigated the importance of ionimpacts for agglomeration. This has also shown that some long-range network forces exist in a crystal, which may relate phase transition and ion bombardment. In order to investigate the long-range order interactions, we propose a method to describe the lattice interactions macroscopically. We call it pixel mapping (PM). With the help of PM, we can clearly describe details of the intermediate processes and estimate the degree of crystallinity during ion irradiation. B implantation into a B doped Si crystal at different bombarding energies was analyzed by PM. Sudden changes from a crystalline to an amorphous state after a certain number of ion impacts were observed and analyzed by PM. PM described clearly these change as cooperative lattice reactions and revealed the long-range order interactions between target atoms in a crystal. Therefore, we can conclude that impurity agglomeration is cooperatively triggered by long-range interactions of atoms in a mesoscopic regime, and PM is a powerful method to elicit the long-range interactions of atoms in a crystal.