On the dose-rate threshold of beam damage in TEM

Electron beam damage in a CaF2–Al2O3–SiO2 glass is investigated using time-dependent Ca L23 and O K-edge electron energy-loss spectroscopy. It appears that there is a threshold dose rate, below which the damage involving the formation of O defects may not be detected, at any total dose. This suggests that the threshold phenomenon of dose rate may result from the competition of damage and recovery processes. The accumulation of damage can only occur when the damage rate is higher than the recovery rate. For surface sputtering process in TEM, the recovery rate is negligible. Therefore, there is no threshold dose rate for surface sputtering.