Figure 5.

Cathodoluminescence – beam current relationship for undoped and doped samples. RT CL peak intensity versus beam current, recorded at 366 nm from undoped Y₂O₃ and at 412 nm and 520 nm from the doped film at RT under electron beam irradiation at 3 keV. The fits are also reported as continuous lines. A schematic of the proposed excitation mechanisms is reported as inset, starting from the above-gap excitation through highly energetic electrons (1), creation of the STE (2–3), STE emission (4a) or ET in presence of Bi (4b) and finally Bi emission (5).