Cathodoluminescence induced in oxides by high-energy electrons: Effects of beam flux, electron energy, and temperature

Cathodoluminescence of cerium dioxide: Combined effects of the electron beam energy and sample temperature

“…It is generally admitted that the CL signal in semiconductors is proportional to the volume density of excess minority carriers [9,10,12]. Alternatively, excitation of CL spectra in oxides originate from the secondary electrons (and holes) generated by elastic and inelastic collisions induced by electron irradiation [15]. The CL signal is produced during trapping of these thermalized secondary electrons by electronic levels of defects and impurities in the band gap of the insulating oxide [4][5].…”

“…We assume in the following that the so-called "extrinsic" CL [8] results from electronic excitation and radiative decay of the defect and impurity levels populated by the thermalized secondary electrons, as discussed previously [15]. At 300 K, most shallow levels created by impurities and defects are fully ionized while deep levels created by charged point defects are partially filled.…”

“…The temperature dependence of the CL intensity was previously addressed by considering the opposite effects on σt and σr: σt increases with temperature, whereas σr decreases [15]. Either a maximum or a steady increase versus temperature was found depending on these respective effects.…”

“…Several spectra were recorded 5 times to check for the reproducibility of data. More experimental details can be found in previous papers [14][15]. Irradiation features such as the total inelastic stopping power ((−dE/dx)inel) and range of electrons computed with the ESTAR code in the continuous slowing down approximation (CSDA) [24] are displayed in Table I.…”

“…Results have been recently obtained in a HVEM on several oxide systems for which emission bands of F centers (oxygen vacancies) with different charge states were recorded for high electron energies inducing oxygen recoils above the threshold displacement energy [14][15]. These in-situ experiments allowed following the in-beam processes of defect formation and recombination in these ceramics, for various temperatures and electron energies, before any off-beam thermally-activated annealing or ageing processes could occur.…”