Ion beam-induced interfacial growth in Si and silicides

We review the mechanisms and consequences of ion beam-induced epitaxial crystallization (IBIEC) in the transition metal- or rare earth-implanted aSi/cSi systems, as determined from in situ transmission electron microscopy (TEM) during irradiation, combined with channeling, high resolution TEM and optical measurements. IBIEC experiments on nm-size crystals confirm previously measured low values of interface roughness in IBIEC. We have performed interfacial growth simulations which indicate that the IBIEC process is, in fact, interface roughness-limited. They also suggest that interfacial growth processes are similar in several respects to surface growth processes, and that they largely determine (i) the growth habit of silicide precipitation, which is dominated by the interfacial energy, (ii) the possibility of trapping a large fraction of the impurities in non-equilibrium sites, leading to significant supersaturation. A consequence of this effect is to allow incorporation of large (over 300-fold supersaturation) Er concentrations in the substitutional sites of the Si lattice, leading to room-temperature photoluminescence (without any oxygen co-implantation). Evidence of a new, thermally induced instability in interfacial growth is presented: it displays both intermittency and very high growth rates, and is strongly affected by ion irradiation.