HIGH-DOSE PHENOMENA IN ZINC-IMPLANTED SILICON-CRYSTALS

The structure of (100) silicon implanted with Zn+ ions at an energy of 50 keV was studied. The ion doses were varied from 1X10(15) to 1X10(1 7) cm(-2) and the beam current density was 10 mu A cm(-2). The analyti cal techniques employed for sample characterization included cross-sec tional transmission electron microscopy and x-ray energy dispersion an alysis. The energy deposition of the ion beam was calculated by using computer simulation codes. For the two lower doses of 1X10(15) and 1X1 0(16) a crystalline-to-amorphous transformation was observed in the im planted layer and this was correlated with the thermal history of the implants and the attendant changes in morphology. In contrast, an amor phous-to-crystalline transition was found to occur at higher doses, na mely 5X10(16) and 1X10(17), where the formation of a complex, structur ed layer consisting of an amorphous phase mixed with crystalline grain s of Zn and partly recrystallized Si was identified together with othe r specific structural features. Detailed characterization of the resul ting microstructures was carried out taking into account the effects o f sample heating, ion-beam-induced amorphization, crystallization, and sputtering. (C) 1996 American Institute of Physics.