Energy distributions of atoms sputtered from alkali halides by 540 eV electrons

The emission of halogen and alkali atoms, occurring under bombardment of alkali halides with electrons has been investigated. The electron energy was 540 eV and the temperature of the target was varied between room temperature and 400°C. We measured the energy distribution of the emitted neutral particles with a time of flight method. It was found that either diffusing interstitial halogen atoms or moving holes dominate the sputtering process above 200°C. Below 150°C alkali halides with lattice parameter s/d ≥ 0.33 show emission of non-thermal halogen atoms. s is the interionic space between two halogen ions in a <110> direction and d is the diameter of a halogen atom. In general the energy distribution of the alkali and halogen atoms is thermal above 200°C, but not Maxwellian.