Hydrothermal synthesis of Co-doped ZnO flakes with room temperature ferromagnetism

Xu, Xiaojing; Cao, Chuanbao

doi:10.1016/j.jallcom.2010.04.086

Cited by 63 publications

(35 citation statements)

References 35 publications

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“…3. The fluctuation of c on Co concentration can be seen, which was also observed by Xu [16], and might be caused by the small discrepancy between the radius of Co 2+ and Zn 2+ ions [14,15].…”

Section: Resultssupporting

confidence: 68%

Room-Temperature Ferromagnetism in Co-doped ZnO Prepared by Microemulsion

Zhang

Shen

et al. 2012

J Supercond Nov Magn

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Zn 1−x Co x O (x = 0, 0.005, 0.01, 0.02, 0.03, 0.06, 0.12) powders have been synthesized by the microemulsion method. XRD patterns confirm the pure wurtzite structure without any impurity phase. TEM images illustrate that Zn 1−x Co x O particles are formed by aggregation of small crystallites. The magnetization measurements show clear room-temperature ferromagnetism in Zn 1−x Co x O (x = 0, 0.005, 0.01), and the saturated ferromagnetic magnetization increased with increasing Co concentration to 0.01. However, the ferromagnetic magnetization decreased drastically with further increasing Co concentration (x > 0.01). PL spectra clearly show an increasing concentration of oxygen vacancies with increasing Co concentration to 0.01, and strong suppression of oxygen vacancies with further increasing Co concentration in Zn 1−x Co x O. We conclude that the high concentration of oxygen vacancies is the key origin for the observed ferromagnetism in Co-doped ZnO.

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Section: Resultssupporting

confidence: 68%

Room-Temperature Ferromagnetism in Co-doped ZnO Prepared by Microemulsion

Zhang

Shen

et al. 2012

J Supercond Nov Magn

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“…On the other side, a similar trend of decrease of band edge in Zn 1-x Co x O films is reported by many workers [5,17,19]. This low energy shift of the E g as a function of the Co content can be explained due to the s,p-d exchange interactions between the band electrons and the localized d electrons of the Co 2+ ions substituting for Zn 2+ ions [20,21]. The s-p and p-d exchange interactions give rise to a negative and a positive correction to the conduction and valence-band edges, leading to narrowing of the band gap [22].…”

Section: Transmittancesupporting

confidence: 82%

Structural and optical properties of Co and Ni doped ZnO thin films prepared by RF magnetron sputtering

Stolyarchuk

Kleto

Dziedzic

2017

PCSS

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We have reported the effect of Co and Ni doping on structural and optical properties of ZnO thin films prepared by RF reactive sputtering technique. The composite targets were formed by mixing and pressing of ZnO, Mn 3 O 4 , CoO and NiO powders. The thin films were deposited on sapphire, quartz and glass substrates. The structure study confirms the formation of the hexagonal wurtzite ZnO without any secondary phase in transition metal (Co, Ni) -doped samples. Cross-sectional TEM images of all studied samples show a denseand uniformly textured structure composed of column-like structure along the growth direction. The surface morphology of the thin films was studied using atomic force microscopy (AFM). Different surface morphology (AFM) images were obtained depending on the film composition and growth conditions. Optical absorption spectra suggest of substitution Zn 2+ ions in ZnO lattice by transition metal atoms. The shift of the absorption edge due to decrease the energy band gap with increasing cobalt content and complex dependence of the energy band gap on content of nickel was observed in optical absorption spectra of the studied films. The room temperature photoluminescence peaks are attributed to near band gap emission and vacancy or defect states.

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“…This low-energy shift of E g as a function of the Co content can be explained by two reasons: (i) it might result from destabilization of O 2-(2p 6 orbitals at O 2-ions adjacent to Co 2+ ), which extends the valence band edge by 0.5 eV [17] or point defects such as nanoclusters of Co, CoO can also lead to this shift [18] (however, these defects have not been observed in the present films); (ii) as mainly due to the s-d and p-d spin-exchange interactions between band electrons and localized d-electrons of Co 2+ ions substituting Zn 2+ ions [7,19]. The exchange interaction between transition metal ions and band electrons gives rise to negative and positive corrections to the conduction and valence-band edges, leading to narrowing the band gap [20].…”

Section: Resultsmentioning

confidence: 67%

“…The magnetic property of ZnCoO thin films has been the focus of numerous investigations. Several groups [7,8] have observed ferromagnetism in ZnO:Co systems, while in other groups [9,10] this magnetic behavior is not observed in similar samples. These controversial results indicated that the magnetic properties are very sensitive to the shape of the samples and to the preparation conditions.…”

Section: Introductionmentioning

confidence: 98%

Structural and optical properties of Zn1-xCoxO thin films prepared by RF reactive sputtering technique

Савчук¹

2014

Semicond. Phys. Quantum Electron. Optoelectron.

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Abstract.We have reported the effect of Co doping on structural and optical properties of ZnO thin films prepared by the RF reactive sputtering technique. The composite targets were formed by mixing and pressing ZnO and CoO powders. The thin films were deposited on silica and glass substrates. The structures of samples have been studied by using X-ray diffraction (XRD) and atomic force microscopy (AFM). With the sensitivity of the XRD instruments, the structural analyses of Co-doped ZnO films reveal formation of predominant (002) reflection corresponding to the hexagonal wurtzite structure without any secondary phase. The AFM study showed that surface morphology of the O Co Znfilms is composed of closely packed nanocrystallites with nanorod shape. The optical properties of the samples were studied using UV-vis absorption and PL spectra. The optical absorption spectra show a red shift of the band edge, which indicates that Co 2+ ions substitute Zn 2+ ions in ZnO lattice. In the room-temperature photoluminescence spectra, four main peaks were revealed in all the samples, which are attributed to ultraviolet, violet-blue, blue and green emission.

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Hydrothermal synthesis of Co-doped ZnO flakes with room temperature ferromagnetism

Cited by 63 publications

References 35 publications

Room-Temperature Ferromagnetism in Co-doped ZnO Prepared by Microemulsion

Room-Temperature Ferromagnetism in Co-doped ZnO Prepared by Microemulsion

Structural and optical properties of Co and Ni doped ZnO thin films prepared by RF magnetron sputtering

Structural and optical properties of Zn1-xCoxO thin films prepared by RF reactive sputtering technique

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