Optically Stimulated Luminescence

Time-resolved optically stimulated luminescence and spectral emission features of α-Al2O3:C

“…(1) giving a lifetime of value ms. This is consistent with the main lifetime in α-Al 2 O 3 :C (~35 ms), attributed to the 3 P→ 1 S transition at an excited F-centre [4,5].…”

“…The incorporation of carbon in -Al 2 O 3 during its synthesis to produce-Al 2 O 3 :C reduces -Al 2 O 3 and facilitates the formation of F and F + centres [4][5]. These electron centres act as luminescence sites for electrons thermally or optically stimulated from electron trapping point-defects.…”

“…These electron centres act as luminescence sites for electrons thermally or optically stimulated from electron trapping point-defects. Although -Al 2 O 3 shows emission bands at 1.25, 1.49, 3.0, 3.27 and 3.8 eV, that is, near 990, 830, 410, 380 and 330 nm respectively [2][3], the most prominent ones in -Al 2 O 3 :C are near 3.0 eV (410 nm) and 3.8 eV (330 nm) respectively [4][5].…”

“…Thermoluminescence (TL) emitted near 410 nm (or variously reported as 420 nm) is attributed to intra-centre-transitions at an F centre following electron capture at an F + defect, whereas hole capture at an F centre or, equivalently, electron capture at an  centre accounts for the emission at 3.8 eV (330 nm) [4][5][6]. Whereas the features of the most prominent absorption and emission bands are well established, many other models, for example those involving hole transfer via the valence band or concentration quenching discussed elsewhere e.g.…”

“…Time-resolved optical stimulation should not be confused with time-resolved photoluminescence (TR-PL) where excitation is performed using UV light which directly ionizes F-centres [5,25]. Akselrod et al [25] used this mode to study thermal quenching of luminescence detected at 420 nm.…”