F + and F centers in α-Al2O3 by electron-induced x-ray emission spectroscopy and cathodoluminescence

Abstract

Study of an α-Al2O3 single crystal by electron-induced x-ray emission spectroscopy and cathodoluminescence is reported. The relative intensities of optical emissions due to F+ and F centers have been determined as a function of the parameters of the electron beam and the annealing of the sample. It is shown that the F+ centers, i.e., the oxygen vacancies with one trapped electron, are predominant when the density of the incident electron beam increases. Similar variation is observed when the electron energy varies from 1 to 4 keV. From the comparison between x-ray and optical spectra, the F+ centers are determined to be stable defects in the bulk of the sample.

Photoluminescence studies of 100MeV Ni8+ ion irradiated Al2O3 single crystals

“…Pure sapphire is colorless and does not show any luminescence at all, but impurities even at concentrations of a few parts per million can cause a remarkable luminescence giving rise to color centers. These color centers or defects can be induced by ion bombardment [3]. Defects induced in sapphire may be various kinds; single vacancy centers (F and F + ) and dimmers (F 2 , F 2+ and F 2 2+ centers) [4].…”

Electron-beam irradiation effects on luminescence properties in subsurface regions of single-crystalline sapphires treated with and without hydrogen plasma exposures

“…Among these particle beams, the electron beam is the most convenient one. However, it is known that electron beam irradiations to sapphire can change oxygen vacancies to F + and F centers, which are common luminescence centers in various oxide materials composed of oxygen vacancies with one trapped electron and two captured electrons, respectively [10,11]. In previous studies, we have found that such electron-irradiation-induced behaviors substantially depend on the type of the sapphire and crystalline quality [12,13].…”

Development of Novel Optical Fiber System for Cathodoluminescence Detection in High Voltage Transmission Electron Microscope

“…For comparison, a CL spectrum of ¡-Al 2 O 3 reported by P. Jonnard et al 5) was shown in the inset of the figure in which the solid and dashed lines were induced by 4 keV electron beam irradiation with electron fluxes of 9.4 © 10 19 and 9.4 © 10 18 electrons/m 2 ·s, respectively. The present CL spectrum is composed of intense line emission at 690 nm (1.8 eV) accompanying a few satellite peaks and a broad band emission peaked at 330 nm (3.8 eV).…”

“…In the observed spectra, no emission of F center (oxygen vacancy trapping two electrons) at around 410 nm (3.0 eV) appeared. 5) In general, CL spectra for Al 2 O 3 show double band emissions attributed to F and F + centers. Such double band emissions, in particular, the intensity ratio of F + /F emission changed with the flux and the fluence as shown in the inset of Fig.…”