Structural transitions in ballistic aggregation simulation of thin-film growth

Computer simulations of thin-film growth were performed by random ballistic aggregation of hard two-dimensional disks. A simple model incorporating sputtering, surface relaxation, and redeposition of sputtered atoms was used to simulate the effects of ion bombardment during growth. Without ion bombardment the deposits had a voided columnar structure typical of a zone 1 growth. With increasing bombardment flux, a densification of the deposit and an elimination of continuous voids were observed. These results reproduce the general features of a bombardment induced microstructural transition from zone 1 to zone T, and also demonstrate that redeposition of sputtered atoms is essential to this transition.