OPTIMAL ENERGIES FOR ION-ASSISTED GROWTH OF IVA THIN FILMS

Abstract

Based on a modified interaction potential and experimental results, an extensive study of ion-energy-correlative thin film growth is presented, As a result, an analytical model for ion energy dissipation into top surface layers is proposed. The proposed model extends previously published models and includes analytical expressions for lattice damage by atomic displacement in surface and subsurface layers. Theoretical calculation indicated that there were three distinctive ion energy regimes within which the different processes occur to the condensed adatoms. The medium energy region (in tens of eV) is a favorite "energy window" from which the pre-deposited atoms or atomic clusters on the substrate can be stimulated further to be rearranged by absorbing the effective energy from an energetic ion beam, leading to uniform film growth. However, over the energy region, the ion can penetrate deeply into the film, and more damage will be caused in the subsurface layer or bulk in this case, which results in the growth of poor-quality or amorphous films. When the ion energy is lower than the "energy window", there is no driving effect for adatoms in both surface and subsurface layers. The molecular dynamic simulations and experimental results have verified the validity of the proposed analytical model and optimal ion energy regimes.