In situ study of effects of ion irradiation on solid-state crystallization of cobalt disilicide thin films

Abstract

Results of a continuing in situ study of the ion-irradiation-modified crystallization of amorphous CoSi 2 thin films are discussed. 1.5 MeV Kr ion irradiation is employed at 90 K to “mix” nominally amorphous, as deposited material for subsequent epitaxial regrowth at 450 K. The ion irradiation is also employed at 300 K to produce ion-assisted crystallization. The average degree of transformation per ion is approximately 4 x 10 -20 cm 3. The resultant number density of crystals, however, depends sensitively on prior treatment of the film. For example, 300 kV electron irradiation at 300 K prior to ion irradiation may result in a large number density of crystal nuclei. Low-dose Kr irradiation at 300 K may also cause a slight increase in the number density of crystals formed subsequently at 450 K, while larger Kr doses at 300 K ( > 3 X 10 14 cm -2) may double the subsequent thermal growth rate at 450 K. These results are discussed qualitatively in terms of nucleation and growth theory.