Characterisation of Alq-implanted LiF by a monoenergetic positron beam

We have studied the radiation damage created by the implantation of 100 keV Alq ions into LiF crystals using a monoenergetic positron beam whose energy can be varied. The fluence range investigated was 1013 to 1016 ions cmy2. Pronounced effects of radiation damage are seen in the line shape of the positron spectrum. The measured S-parameter is used to characterise the radiation damage as a function of depth. A four-layer model is used to fit the data using the computer program VEPFIT. The Positron Annihilation Spectroscopy PAS.results are correlated with optical absorption measurements on the crystals. The use of positrons to profile the radiation damage as a function of depth below the ion implantation surface is shown to be feasible for lithium fluoride crystals. q1999 Elsevier Science B.V. All rights reserved