Cathodoluminescence induced in oxides by high-energy electrons: Effects of beam flux, electron energy, and temperature
Résumé
The cathodoluminescence (CL) induced in four oxide single crystals (et61537;-Al2O3, ZrO2 Y or YSZ, MgAl2O4, and TiO2) by high-energy electrons from 400 keV to 1,250 keV was studied as a function of beam parameters (flux and energy). The main CL bands are assigned to F center (oxygen vacancy) formation by elastic collisions above the threshold displacement energy of oxygen atoms. The beam-intensity dependence is interpreted on the basis of a kinetic-rate model involving F-center production and annihilation. The temperature effect was also followed from about 110 K to 300 K. A broad maximum was found at about 200 K for sapphire, whereas a weak linear increase with temperature was observed for YSZ. The plots of CL intensity versus temperature are interpreted by the interplay between the thermal dependences of thermalized free carrier trapping rates and luminescence efficiency. Finally, the dependence of CL intensity on the primary electron energy for YSZ showing a maximum at about 600 keV is explained on the basis of secondary-electron energy spectra produced by elastic collisions, as computed with the PHITS code.