Decoration of graphene films with europium oxide through the R.F. sputtering technique

ABSTRACTThe present work is aimed to study a comparison among synthesized graphene films, deposited on copper substrates and commercial graphene films; both decorated with Eu2O3 particles, with the purpose of promoting photoluminescence. The decoration procedure was achieved using the radio frequency sputtering (R.F. Sputtering) technique for the deposition of Eu2O3 on synthesized or commercial graphene films. The SEM obtained images, show differences in morphology when commercial and synthesized graphene films are compared. Our results indicate that the type of surface is the main factor that accounts for the europium oxide spatial distribution that ultimately leads to luminescence enhancing. The x-ray photoelectron spectroscopy (XPS) analyses, showed the trivalent oxidation state of europium and the atomic content of Europium for both; the commercial graphene film and synthesized one, where the first one presented the higher europium concentration. Analysis by Raman spectroscopy reveals that graphene films become disordered after the decoration is achieved. The main Raman bands of the commercial graphene films undergo a remarkable red shift, as a consequence of the presence of europium oxide It was observed that the interaction of Eu2O3 with the sp2 levels of graphene, improves the red photoluminescence of the samples grown on both, commercial and prepared graphene films.

Спектральные и структурные характеристики молибдатов (Lu-=SUB=-1-x-=/SUB=-Eu-=SUB=-x-=/SUB=-)-=SUB=-2-=/SUB=-(MoO-=SUB=-4-=/SUB=-)-=SUB=-3-=/SUB=-

The structure, the photoluminescence, and IR absorption spectra of solid solutions (Lu_1 ‒ _ x Eu_ x )_2(MoO_4)_3 have been studied over a wide range of europium concentrations (0 ≤ x ≤ 1). It has been found that there is a correlation between the structure and the spectral characteristics of these compounds. Three types of crystal phases are sequentially changed as the europium concentration increases. The photoluminescence and IR absorption spectra of the monoclinic phase with space group P 2_1/ a have been studied for the first time. The glow maximum at a resonant excitation of Eu^3+ ions is shown to be observed in the samples with orthorhombic structure Pba 2 at x ~ 0.8. The samples existing in monoclinic P 2_1/ a phase at x ~ 0.2 demonstrate the maximum luminescence intensity upon excitation in the band with the charge transfer.