The Crystalline-To-Amorphous Phase Transition In Irradiated Silicon

Abstract

The amorphous(a)-to-crystalline (c) phase transition has been studied in electron(e-) and/or ion irradiated silicon (Si). The irradiations were performed in i n the Argonne High Voltage Microscope-Tandem Facility The irradia ion of Si, at <10 K, with 1-MeV e- to a fluence of 14 dpa failed to induce the c-to-a transition. Whereas an irradiation, at <10 K, with 1.0 or 1.5-MeV Kr+ ions induced the c-to-a transition by a fluence of ≈0.37 dpa. Alternatively a dual irradiation, at 10 K, with 1.0-MeV e and 1.0 or 1.5-MeV Kr+ to a Kr+ fluence of 1.5 dpa -- where the ratio of the displacement rates for e- to ions was ≈0.5--resulted in the Si specimen retaining a degree of crystallinity. These results are discussed in terms of the degree of dispersion of point defects in the primary state of radiation damage and the mobilities of point defects.

The Effect of Simultaneous Electron and Kr+ Irradiation on Amorphization of CuTi

“…A Faraday cup located above the specimen position was used to measure total beam current (I T ) , and a movable Faraday cup located in the viewing chamber was used for beam profiling and for measuring the peak electron flux (I P ) . Typical beam profiles employed for this study can be described approximately by a Gaussian distribution, I(r) = I p -exp{-1/2(r/a) 2 } [1]• The parameter a is the standard deviation of the distribution, and was calculated from the measured electron fluxes using the relationship O-(I T /27tI P ) l / 2 . The beam parameters were chosen to obtain a peak electron flux of 2 x 10 19 electrons/cm 2 /s, corresponding to a calculated peak displacement rate of 1 x 10" 3 dpa/s.…”

“…A recent study [1] has shown that amorphization of Si during irradiation with 1-MeV Kr + icns at 10 K can be strongly retarded by simultaneously irradiating the sample with a 1-MeV electron beam. The retardation effect under simultaneous irradiation was found to occur only when the calculated electron displacement rate (dpa/s) exceeded that for the Kr + beam by a factor of about two.…”