Ion-beam induced crystallization and amorphization at a crystalline/amorphous interface in silicon

Abstract

Previous investigations have shown that solid-phase epitaxial crystallization (SPEC) can be catalyzed by defects which are produced by ion bombardment [1–3]. This so-called ion-beam induced epitaxial crystallization (IBIEC) takes place at temperatures which are low compared to those required to induce equivalent thermal-only epitaxial crystallization. Using Rutherford backscattering/ion channeling, we have investigated the temperature dependence of the crystalline/amorphous (c/a) interface dynamics in self-amorphized silicon during irradiations with 1.5 MeV Xe ions. At temperatures above 260°C, the Xe-ion beam induced crystallization with an activation of ≈ 0.24 eV, as was previously reported for MeV Ne-ion irradiations [2]. However, at temperatures below a critical temperature of ≈ 220°C, the interface displacement is reversed and the amorphous phase grows at the expense of the crystalline phase. We choose to call this latter phenomenon ion-beam induced interface amorphization (IBIIA). At temperatures above and below ≈ 220°C, the c/a-interface displacement is linearly dependent on Xe-ion fluence. Transmission electron microscopy studies of these two regimes reveal that very similar interface structures are associated with both IBIEC and IBIIA, and these interfaces are remarkedly smoother than the c/a interfaces which are produced in the present studies either by preannealing self-amorphized silicon at 450°C for 15 min or by Xe ion end-of-range damage. The results of this work identify. IBIIA and IBIEC to be inverses of one another for the 1.5 MeV Xe-ion case and this reversibility is discussed in terms of a model which considers the relative contribution of defect complexes to the total free energy of the crystalline phase.