Electron trapping in a SiO2 layer during e-beam deposition of 30–40 nm thick 1% EuF3-doped CaF2 nanofilms on a Si/SiO2 substrate was studied by the photoelectron emission (PE) method. The Si/SiO2 substrate consists of 1 µm thick amorphous SiO2 layer thermally grown on a Si wafer. After the e-beam deposition of CaF2:EuF3 nanofilms, PE current from these nanofilms was measured. PE was excited by UV photons with an energy of 4–6 eV, and it was found that the registered photoelectrons were emitted both from the nanofilms and the substrate. The recorded PE spectra had several distinct PE peaks that were associated not with CaF2:EuF3 but with electrons trapped in the defect centres of the SiO2 layer. These defect centres presumably existed in the as-fabricated SiO2 layer and could capture electrons during the e-beam deposition process of CaF2:EuF3 nanofilms. The same PE peaks were observed in the PE spectra of a bare Si/SiO2 substrate when this substrate was irradiated with weak electrons with energies up to 1.5 keV emitted by a thermocathode source. To confirm that the PE maxima were created only after exposure to accelerated electrons, bare Si/SiO2 substrates were irradiated with 8 keV X-rays and 6 MeV gamma rays, and their PE spectra were measured after irradiation. No PE maxima were observed in the Si/SiO2 spectra after irradiation with photons. The results obtained indicate that the e-beam deposition process of CaF2:EuF3 nanofilms creates charge centres in the Si/SiO2 substrate by trapping electrons in the SiO2 layer.