Comment on “Damage evolution in LiNbO3 due to electronic energy deposition below the threshold for direct amorphous track formation” [J. Appl. Phys. 126, 125105 (2019)

Abstract

In their article, Wesch et al. deal with defect formation and amorphization in LiNbO3 after irradiation close to the threshold conditions. It is problematic that two thermal spike models are applied in the analysis, which are not compatible with each other. The key parameter of the authors' model—efficiency γ—is derived erroneously in the paper. Formal agreement with the experiments is achieved for point defect production using four parameters for reducing the deviations. It is assumed that amorphization proceeds with the growth of amorphous pockets. However, the conditions of the formation of these pockets are calculated using the inelastic thermal spike model beyond the range of its validity, and this model rejects the basic assumptions of the authors' exciton model. In pursuance of the above criticism, the paper of Wesch et al. is not well thought-out and the experimental results would require a more consequent and closely reasoned analysis.