Red Luminescence of Color Centres in Sapphire

Abstract

Recently significant progress has been achieved in understanding the nature of ultraviolet and visible luminescence of color centres in sapphire (a-Al2O3) crystals (see e.g. /1 t o 6/). The luminescence centres (LC) emitting in the red and infrared spectral region have received considerably less attention /? t o 10/ although tunable laser generation has been achieved using one type of such centres / S / . The main published results on IR luminescence have been s u mmarized in Table 1.

High-dose neutron irradiation of MgAl2O4 spinel: effects of post-irradiation thermal annealing on EPR and optical absorption

“…6 shows the dose dependence of both processes for the optical absorption at 37 000 cm À1 and for the EPR band. The observed increase in optical absorption and EPR bands anneals out at temperatures below 650 K in a wide annealing step process that starts at room temperature and finishes around 650 K, similar to the annealing behaviour observed for V-centres [22]. Fig.…”

“…Taking into account that the UV bands are related to the oxygen vacancy defects (mainly F centres) it seems reasonable to relate the 19 500 cm À1 band to some oxygen vacancy defect, probably small clusters of two or three vacancies (giving rise to F 2 or F 3 defects). This proposal is further supported when taking into account that these type of defect also appears in the same energy region for Al 2 O 3 or MgO [22,24], and that they anneal out before the main F centre annealing step.…”

“…Both bands behave in a similar way, indicating that they are related. In many papers this optical band has been assigned to F + centres [18][19][20][21][22][23][24][25][26][27]. Taking this relationship into account, it can be clearly concluded, for the first time, that the measured EPR band must be assigned with F + centres.…”

Cathodoluminescence studies of defects in coated boron nitride

“…Carriers excited to these ST states can then be thermally excited into conducting states, thereby activating charge transport in the Al 2 O 3 layer. This absorption band is near a band observed at ~2.89 eV from radiation induced defects [35].…”

ИК-люминесценция alpha-Al-=SUB=-2-=/SUB=-O-=SUB=-3-delta-=/SUB=- при 4-300 K

“…Часто для интерпретации результатов исследований используют зонную схему α-Al 2 O 3 , располагая в запрещенной зоне энергетические уровни сложных ЦО в различных зарядовых состояниях с указанием энергий возбуждения, межуровневых переходов, сопровождаемых люминесценцией (см., например, [3]). Вместе с тем в имеющихся моделях [3] энергетических уровней сложных ЦО в α-Al 2 O 3 не отражена их способность излучать в ближней инфракрасной (ИК) области, наблюдавшаяся экспериментально в [8][9][10][11][12].…”