Dual-donor (Zni and VO) mediated ferromagnetism in copper-doped ZnO micron-scale polycrystalline films: a thermally driven defect modulation process

Hu, Liang; Huang, Jian‐Wen; He, Haiping; Zhu, Lingjun; Liu, Shijiang; Jin, Yizheng; Sun, Luwei; Ye, Zhizhen

doi:10.1039/c3nr00136a

Cited by 47 publications

(47 citation statements)

References 84 publications

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“…This result can be explained by the thermal displacement of donors on Zn sites by Zn i or via the formation of ionized donor -zinc interstitial defect pairs (D + -Zn i + ). [ 30 ] A Lorentzian line shape was used to fi t the g = 1.96 EPR peaks shown in Figure 2 a to compare their full width half maximum (FWHM). Figure 2 b shows the fi tted EPR spectra, which shows the FWHM decreasing from 9.5 to ≈6.8 G after annealing.…”

Section: Introductionmentioning

confidence: 99%

Photophysics of Point Defects in ZnO Nanoparticles

Choi

Phillips

Aharonovich

et al. 2015

Advanced Optical Materials

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including oxygen vacancies ( V O ), [ 6 ] and zinc vacancies ( V Zn ), [ 7 ] interstitials (Zn i , O i ), [ 8 ] and antisite defects (Zn O , O Zn ) [ 9 ] as well as chemical impurities such as Cu. [ 10 ] The need to characterize point defects in ZnO is further amplifi ed with the recent applications of ZnO nanoparticles as hosts of single emitters for quantum information processing [11][12][13] and their use in random lasing [ 14 ] and other advanced sensing technologies. [ 15 ] These applications require precise control over the defect engineering in ZnO nanoparticles. Consequently, correlative characterization of point defects will be valuable to explore the luminescence properties and affi liate them with their chemical and paramagnetic spin features.In this work we perform comprehensive studies on the formation and photophysical properties of point defects in ZnO nanoparticles. In particular, we employ correlative characterization techniques to assign the optical emission peaks and electron paramagnetic resonance (EPR) lines to specifi c defects in ZnO nanoparticles. Our results provide new insight into optical luminescence properties of ZnO nanoparticles and promote them as potential candidate for nanophotonic technologies. [ 16 ] Results and DiscussionAfter being annealed in an Ar or Zn vapor environment at 700-900 °C the as-received ZnO nanoparticles (diameter ≈ 20 nm) coalescence [ 17,18 ] and display faceted morphologies ( Figure 1 ). The nanoparticles increase in average size up to about 120 nm after annealing in inert gas (Ar) or oxygen, and up to 150 nm for annealing in Zn vapor at 900 °C [see Figures S1 and S2, Supporting Information for nanoparticle sizes obtained from scanning electron microscopy (SEM) image and X-ray diffraction (XRD) analysis]. Since the Bohr radius of ZnO is 2.34 nm, [ 19 ] the nanoparticles are large enough to avoid quantum size effects but still possess a suffi ciently large surface area to allow defect engineering.To investigate the occurrence of defects in ZnO nanoparticles, EPR spectroscopy was performed. Figure 2 a shows EPR spectra of the as-received, O 2 annealed, Zn vapor annealed ZnO nanoparticles and a bare Si(100) substrate for comparison. The as-received ZnO nanoparticles exhibit a strong signal at g = 1.96, which has been previously assigned to zinc vacancies (V Zn − ), [ 20 ] oxygen interstitials (O i − ), [ 20 ] zinc interstitials (Zn i + ) [ 21 ] and to electrons in weakly bound or conduction band (CB) Zinc oxide (ZnO) nanoparticles have recently been identifi ed as a promising candidate for advanced nanophotonics applications and quantum technologies. This work reports the formation of luminescent point defects and describes their photophysical properties. In particular, it is shown using correlative photoluminescence, cathodoluminescence, electron paramagnetic resonance (EPR), and X-ray absorption near-edge spectroscopy that green luminescence at 2.48 eV and an EPR line at g = 2.00 belong to a surface oxygen vacancy (V o,s + ) center, while a second green emi...

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Section: Introductionmentioning

confidence: 99%

Photophysics of Point Defects in ZnO Nanoparticles

Choi

Phillips

Aharonovich

et al. 2015

Advanced Optical Materials

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“…BMP concentration might be low due to the lower concentration of doped ions. Also a charge transfer processes derived from dualdonor (Zn i and O V ) might contribute partly in the FM interaction via indirect double-exchange mechanisms as proposed by Liang et al [17]. Also defect related surface spins from large surface area might contribute partly for the observed FM in the Co doped ZnO NPs as both sharp and broad defect modes have been seen in the PL spectra [33].…”

Section: Possible Fm Interactionmentioning

confidence: 93%

“…[39] to realize possible origin of RT FM and talked about hole-mediated exchange interactions where a curie temperature above room temperature in p-type ZnO with 5% Mn ions as dopants and a carrier concentration of 3.5 Â 10 20 holes cm À3 have been predicted [1]. Also different groups have demonstrated that the FM state might be stabilized by additional electron or hole doping in case of TM doped ZnO [17,40]. The presence of intrinsic defects (O V, Zn i , Zn V etc.)…”

Section: Possible Fm Interactionmentioning

confidence: 99%

“…In addition, some startling reports on the RTFM in nonmagnetic doped [16,17] and undoped oxide (ZnO,TiO 2 , MgO, CeO 2 etc.) 18,19 systems indicate that in specific cases the magnetic properties may not be exclusively related to the presence of the magnetic ions but strongly mediated by the point defects, such as (O V , Zn V , O i , Zn i ) and their clusters.…”

Section: Introductionmentioning

confidence: 98%

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Growth of Co-doped ZnO nanoparticles by porous alumina assisted sol–gel route: Structural optical and magnetic properties

Karak

Pal

Sarkar

et al. 2015

Journal of Alloys and Compounds

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“…Since its Curie temperature (T c ) was theoretically predicted to be above room temperature [9], TMdoped ZnO has been extensively studied and room temperature ferromagnetism (RTFM) has been experimentally observed in Co-, Mn-, Cu-doped ZnO system [10]. Among them, Cu-doped ZnO nanostructures, easy to optically chase defect structure [11,12] and eliminated from secondary magnetic phase or clusters [13,14], have been most intensively investigated as a prototypical model to clary the origin of RTFM. If considering spin-orbit coupling, its moment can reach 3.55m B /atom [15], higher than that of Mn- [16], Co- [17] doped ZnO samples.…”

Section: Introductionmentioning

confidence: 99%