Hydrogen implantation defects in MgO

Deuterium and hydrogen ions with an energy of 15 keV have been implanted in virgin MgO (100) single crystals and in single crystals containing helium implantation generated microcavities. Doses were varied from 2x10(15) to 2x 10(16) cm(-2). The samples were annealed from room temperature to 950 K. Th e defects produced by hydrogen and the trapping of hydrogen at the defects were monitored by photon absorption and positron beam analysis. With this n ovel technique a depth distribution of defects can be determined for implan tation depths from 0 to 2000 nm. The technique is very sensitive for vacanc y and vacancy clusters, i.e. sites with low electron density. After 950 K a nnealing microcavities were observed for the 2x10(16) cm(-2) dose but not f or the 10 times lower dose. During annealing up to 750 K point defects are mobile but the defect clusters remain small and filled with hydrogen. In sa mples which contain already microcavities, point defects and deuterium from the deuterium irradiation are accumulated by the microcavities. (C) 1999 E lsevier Science B.V. All rights reserved.