Photoluminescence properties of Co-doped ZnO nanorods synthesized by hydrothermal method

Abstract

Cobalt doped zinc oxide nanorods Zn1−xCoxO (x = 0.01, 0.10) have been synthesized by a hydrothermal process with Zn(NO3)2, Co(NO3)2, NH4OH, CO(NH2)2 and C2H5OH at 150 °C for 1 h. X-ray diffraction and scanning electron microscopy were used to characterize the crystalline structure, size and morphology of the samples. The photoluminescence (PL) and the PL excitation spectra of the nanorods were measured in the range of temperature from 15 K to room temperature. The PL spectra at low temperatures exhibit a group of ultraviolet narrow lines in the near-band-edge region of 3.0–3.4 eV and a very broad band peaked at 3.20 eV. The origin of the near-band-edge PL is interpreted as an emission from free excitons, neutral donor-bound excitons, radiative transitions from a donor to the valence band and donor–acceptor pairs. In particular, a group of emission lines in the red region of 1.8–1.9 eV have been revealed. These emission lines were assigned to the radiative transitions within the tetrahedral Co2+ ions in the ZnO host crystal.

Synthesis and characterization of ferromagnetic Zn1−Co O films

“…The broadened peak near 3.2 eV represents the donor-acceptor pair transitions of the Co-O and Zn-O pairs. The PL results agree well with previous studies of polished ZnO films [35], Co-added ZnO nanorods [36], and nitrogen-implanted ZnO nanorods [37].…”

Low-symmetry Td-distorted Co2+ centres in ceramic ZnO:Co

“…This band appears 0.13 eV red shifted with respect to the reported NIR bands mentioned above and with a slightly larger bandwidth. A similar broadband emission was observed by Müller et al [14] and Loan et al [15] in ZnO:Co nanowires and nanorods. Their results revealed the band shape is strongly dependent on the cobalt concentration and do not show any trace of narrow peak structure, i.e., zero-phonon line for cobalt concentrations higher than 4%, even at 19 K. The authors have attributed this broadband to phonon side-band of the 2 E(G) ?…”

Red luminescence of Zn /ZnO core–shell nanorods in a mixture of LTZA/Zinc acetate matrix: Study of the effects of Nitrogen bubbling, Cobalt doping and thioglycolic acid

“…S3 with x ¼0.1% has a broad peak with the center at the wavelength of about 478 nm. S4 with x ¼0.3% has the same feature which has been superposed with the fundamental absorption edge that has also been confirmed by Loan et al [45]. It can be deduced that cobalt insertion enhances ZnO crystal growth as well as structural defects.…”