Effect of swift heavy ion irradiation on the optical properties of sapphire

Abstract

Single crystals of sapphire (Al₂O₃; Fe, Ti, Cr) were irradiated with 100 MeV Ti and 100 MeV Ni swift heavy ions (SHI) at fluence 110¹², 510¹² and 110¹³ ions/cm². Photoluminescence (PL) spectra of pristine and irradiated sapphires were recorded at room temperature under 2.8 eV blue excitation. A broad band consisting of two emission bands centered at 2.48 and 2.30 eV corresponding to F₂ and F₂²⁺ defect centers, respectively, were observed. The concentration of these centers increases monotonically with the Ti ions fluence. While in Ni irradiated sapphires, it increases up to 510¹² ions/cm² and then showed a decreasing trend at fluence 1х10¹³ ions/cm². The changes in concentration of these defect centers are explained in term of creation of new defect centers (oxygen vacancies), cluster formation and quenching of these defect centers and are correlated with the nature of ions.