Photoluminescence study of swift heavy ion (SHI) induced defect centers in sapphire

Single crystals of sapphire (Al2O3: Fe, Ti, Cr) were irradiated at room temperature with different fluence of 100 MeV Ni ions. Photoluminescence (PL) spectra of pristine and irradiated sapphires were recorded at room temperature under 2.8 eV blue excitation. A broad emission band consists of two bands centered at 516 nm corresponding to F2 defect center and 546 nm corresponding to F 2 2 + defect center was observed. The intensity of these defect centers was found to vary with the fluence. F 2 2 + defect center develops at low fluence reaching maximum at 5 × 1016 ions/m2 and finally decreasing at higher fluence. The behavior is interpreted in terms of creation of defect centers, their clustering and annihilation.