Theoretical modeling of swift-ion-beam amorphization: Application to LiNbO3

A general theoretical framework to describe crystal damage and amorphization under swift-ion-beam irradiation is discussed. Main physical channels accounting for electron energy losses are considered: (a) phonon generation (heating) and (b) exciton localization and de-excitation. Two alternative schemes are analyzed. In one of them, intrinsic defects are generated through a direct thermal process, i.e. through channel (a). Above a certain threshold rate of electronic energy deposition the temperature reaches the melting point and the crystal becomes amorphous. In the other scheme, defects are generated through non-radiative de-excitation of excitons, formed during the final stage of electron slowing down. This may require to overcome a certain potential energy barrier. In this case the necessary thermal energy is provided by coupling to channel (a). The two schemes are discussed in the light of available experimental information.