Rare earths (Ce, Eu) molar concentration-dependent of thestructural and optical properties of CBD-CDs nanofilms

摘要

It presents the characterization of rare earths (Eu,Ce)-doped CdS nanofilms that were synthesised by the growth technique chemical bath de-position (CBD) at the reservoir temperature of70±2?C. The doping of CdS with rare earths is performed by varying the synthesis time from60 to 135 min. The rare earths molar concentration was range from0.0≤x≤3.5, which was determined by energy dispersive X-ray spec-troscopy. X-ray diffraction (XRD) analysis and Raman scattering reveal that CdS nanofilms showed the zinc blende (ZB) crystalline phase.The CdS average nanocrystal size was ranged from 1.84 to 2.67 nm that was determined by the Debye-Scherrer equation from ZB (111)direction, which was confirmed by transmission electron microscopy. Raman scattering shows that the lattice dynamics is characteristic ofbimodal behaviour and the multipeaks adjust of the first optical longitudinal mode for the (Eu,Ce)-doped CdS, which denotes the Raman shiftof the characteristic peak about 305 cm?1of the CdS nanocrystals. The CdS nanofilms exhibit a direct bandgap that slightly decreases withincreasing doping, from 2.50 to 2.42 eV, which was obtained by room temperature transmittance. The room-temperature photoluminescenceof CdS shows the band-to-band transition at 2.88 eV, which is associated to quantum confinement and a dominant radiative band at 2.37 eVthat is called the optical signature of interstitial oxygen. The Eu3+-doped CdS photoluminescence shows the dominant radiative band at2.15 eV, which is associated to the intra-4f radiative transition of Eu3+ions that corresponds to the magnetic dipole transition, (5D0→7F1).For the Ce3+-doped CdS the dominant radiative transition, at 2.06 eV, is clearly redshifted, although the passivation of the CdS nanofilms byCe was approximately by a factor about 21 for the best results.