Rectangular nanovoids in helium-implanted and thermally annealed MgO(100)

Cleaved MgO(100) single crystals were implanted with 30 keV He-3 ions with doses varying from 1 x 10(19) to 1 x 10(20) m(-2) and subsequently thermall y annealed from 100 to 1100 degrees C. Transmission electron microscopy obs ervations revealed the existence of sharply rectangular nanosize voids at a depth slightly shallower than the helium-implantation range. Monitoring of the defect depth profile and the retained amount of helium was performed b y positron-beam analysis and neutron depth profiling, respectively. (C) 200 0 American Institute of Physics. [S0003-6951(00)01709-5].