Amorphization in silicon by electron irradiation

We have found that amorphization is induced in crystalline silicon under Me V electron irradiation at low temperatures of about 25 K. The amorphization process has been observed at 25 K by means of in situ transmission electro n microscopy and diffraction. The dose of 2 MeV electrons needed for amorph ization is smaller than 7.5 x 10(22) cm(-2) at 25 K, which corresponds to 5 .0 displacements per atom. The threshold electron energy for amorphization at 25 K is about 1 MeV. We discuss the mechanism of amorphization in Si bas ed on the experimental finding.