STUDY OF DAMAGE STRUCTURE IN MAGNESIUM-OXIDE SINGLE-CRYSTALS AFTER ARGON IMPLANTATION

Single crystals of magnesium oxide were implanted with 150 keV argon i ons at room temperature with fluences ranging between 5 x 10(14) and 1 0(16) Ar+ cm(-2) using a dose rate of approximately 10(13) Ar+ cm(-2) s(-1). After implantation samples were isochronally annealed in vacuum at temperatures up to 1000 degrees C. Before and after each annealing step defect depth profiles were determined by alpha-particle channeli ng using a backscattering geometry. Relative defect densities were obt ained by extracting the contributions of the magnesium sublattice from the normalized aligned spectra, which were then simultaneously fitted to equations describing the dechanneling rate and the backscattering yield as a function of depth. The defect density reached saturation at a fluence of 2 x 10(15) Ar+ cm(-2). Up to this dose the damage profil e is in agreement with TRIM predictions. At higher fluences the thickn ess of the damaged region increases due to defect saturation of the ta il region of the implantation profile. The experimental results confir m a mixed damage structure, which probably consists of randomly disord ered regions and extended defects. Annealing of the first defect compo nent occurs at approximately 700 degrees C.