AMORPHIZATION AND CRYSTALLIZATION IN HIGH-DOSE ZN-IMPLANTED SILICON()

The nature of amorphization and crystallization of Si brought about by 50 keV Zn ion implantation within the dose range 2X10(17)-1X10(18) cm (-2) is studied. The structures are evaluated in the as-implanted stat e by transmission electron microscopy, transmission electron diffracti on, reflection high-energy electron diffraction, selected-area electro n diffraction, x-ray energy-dispersive analysis, and Rutherford backsc attering spectrometry. It is found that, contrary to the theoretical p redictions, the Zn concentration profile does not reach saturation eve n at a dose as high as 1X10(18) cm(-2). A common feature of the micros tructure of these high-dose implants is the formation of a continuous amorphous layer and concurrent crystallization of Zn and Si in small c rystalline clusters. Microscopic beam-heating effects are also believe d to play an appreciable role in the development of the specific morph ologies observed. The results are interpreted in terms of two recent m odels proposed in the literature and the concept of critical dose rang es. (C) 1997 American Institute of Physics.