Maskless nano-implant of 20 keV Ga+ in bulk Si(1 0 0) substrates

Abstract

Multidirectional SPEG (Solid Phase Epitaxial Growth) of silicon has been investigated in micro and nanoamorphous structures generated on a crystalline substrate by a nano-sized ion beam, Gaussian shaped and with a standard deviation of about 5nm. The 20keVGa+ ions were implanted at a fluence of 5×1014ionscm−2 in a bulk Si(100) single crystal. Two structures were used for the implants: circular regions of 100nm and 1μm diameters respectively and straight lines 10nm in width and few microns in length along (100) or (110) directions. The lateral spread of ions has been taken into account in the damage estimation. Transmission Electron Microscopy indicates that the structures are made of an amorphous core surrounded by a defective and filamentary shell. The recovery of the damaged outer regions promptly occurs during the early stages of the thermal treatment at 500–600°C for all the structures. By prolonging annealing time, re-crystallization of the amorphous cores is achieved too by the movement of the underneath crystal–amorphous interface. The re-growth is almost defects free when the contribution of the crystalline seed below the structures is present, defective and twin mediated if it misses as in the thinnest regions of the specimen.