Abnormal distribution of defects introduced into MgO single crystals by MeV ion implantation

Abstract

The distribution of defects introduced into MgO single crystals formed by MeV ion implantation was studied and then compared to the distribution calculated by using TRIM code. First, MgO single crystals were implanted with 3.1 MeV Au ions at a dose of 2 × 10 16 cm −2. Cross-sections of the crystals examined by using transmission electron microscopy revealed an abnormal distribution of the defects, namely, that the peak defect density occurred at a deeper depth (1.7–1.9 μm) than implanted-Au distribution (0.5–1.6 μm), although the peak defect density normally occurs at a shallower depth than the peak implanted-Au concentration. The ion implanted MgO crystals were irradiated with 20 keV X-ray to examine the effect of electronic excitation on the defect distribution. The X-ray irradiation considerably reduced the defect density in the implanted layer, indicating that the abnormal defect distribution is due to the effect of electronic excitation around the energetic ion tracks.