Study of damage structure in magnesium oxide single crystals after argon implantation

Single crystals of magnesium oxide were implanted with 150 keV argon ions at room temperature with fluences ranging between 5 x 10(14) and 10(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 channeling using a backscattering geometry. Relative defect densities were obtained 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 profile is in agreement with TRIM predictions. At higher fluences the thickness of the damaged region increases due to defect saturation of the tail region of the implantation profile. The experimental results confirm a mixed damage structure, which probably consists of randomly disordered regions and extended defects. Annealing of the first defect component occurs at approximately 700 degrees C.