Effects of high dose Pb+ implantation on Si: atomic force and transmission electron microscopy study

We investigated the influence of ion dose on the microstructure of Pb⁺ -implanted (100) monocrystalline Si at room temperature. Surface layer amorphization is observed by cross sectional transmission electron microscopy (XTEM) at dose 1×10¹⁵cm^-2. At doses ⟩1×10¹⁵ cm^-2 a competitive process of ion beam induced crystallisation (IBIC) in the amorphized (a)-layer is established. The evolution of surface roughness (estimated by atomic force microscopy (AFM)), as a function of implantation dose reflects the process of microcrystal formation in the surface a-layer. High resolution transmission electron microscopy (HRTEM), combined with Rutherford backscattering spectroscopy (RBS) and computer simulations have also been used. It has been established that the front of new phase crystallization (cubic Pb) starts at positions corresponding to the peaks in the Pb⁺ implant profiles. By computer processing of the HRTEM image of the nanocrystal so formed, the theoretical model for recrystallization by precipitation in liquid phase of elements with low melting temperature has been confirmed experimentally