Formation mechanism of luminescence spectra of carbon nitride films doped by europium chloride CNx: EuCl3

Luminescence and absorption spectra of nanostructured carbon nitride (CNx)-films doped by EuCl3 were studied. It was found that the films with europium concentration equal to 4.5 at% and 10 at% placed on the glass substrate exhibit a luminescence spectrum specific to the EuCl3 compound but with a frequency shift depending on the rare-earth dopant primary concentration. Comparison of the luminescence spectra with theoretical calculations showed a considerable part of the coordination complexes [EuCl9]6- entering into chemical bonding with the carbon nitride film matrix that directly impacts the covalency degree of the《Eu3+-Сl1-》bond. It was found that some of the complexes have vacancy-type defects but the number of the vacancies is small and could be well identified only in films with a higher europium concentration.