Electronic structure of ZnO nanorods studied by angle-dependent x-ray absorption spectroscopy and scanning photoelectron microscopy

Chiou, J. W.; Jan, J. C.; Tsai, Hsiu-Min; Bao, C. W.; Pong, W. F.; Tsai, M.‐H.; Hong, I.-H.; Klauser, Ruth; Lee, J. F.; Wu, Jih‐Jen; Liu, S. C.

doi:10.1063/1.1737075

Cited by 106 publications

(72 citation statements)

References 19 publications

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“…These spectra exhibit three peaks labeled A 1 , B 1 , and C 1 at 1022.7, 1024.3, and 1028.9 eV, respectively, which mainly refl ect the electron transitions from Zn 2 p 3/2 → 4 s , 5 s and Zn 2 p 3/2 → 3 d derived states in the CB. [ 32 ] The Zn L 3 -edge spectra are virtually identical in all three samples, indicating that the atomic confi gurations of Zn atoms are unaffected following the coalescence of nanoparticles. This result confi rms that no additional Zn-related defects such as Zn interstitials are introduced during Zn vapor annealing presumably because of the high mobility of Zn i .…”

Section: Full Paper Full Paper Full Papermentioning

confidence: 86%

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: Full Paper Full Paper Full Papermentioning

confidence: 86%

Photophysics of Point Defects in ZnO Nanoparticles

Choi

Phillips

Aharonovich

et al. 2015

Advanced Optical Materials

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“…6 represents Zn L 3,2 -edge NEXAFS spectra of pure and Co doped ZnO nanoparticles. The spectral features in the energy region between 1020 and 1035 eV are associated with the transition of Zn 2p electron to Zn 4s and anti-bonding 3d states [33]. The bottom inset reveals the intensities of features around 1028 eV and 1032 eV that decreases and shifts toward higher energies with increase of 'Co' concentration, where as the features around 1022 eV are less sensitive to the 'Co' doping.…”

Section: Resultsmentioning

confidence: 99%

Spectroscopic investigation of an intrinsic room temperature ferromagnetism in Co doped ZnO nanoparticles

Srinatha

Angadi

Nair

et al. 2014

Journal of Electron Spectroscopy and Related Phenomena

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a b s t r a c tPure and Co substituted ZnO nano crystalline particles were prepared by solution combustion technique using l-Valine as a fuel. As synthesized powder samples were characterized by X-ray diffractometer and SQUID magnetometer to confirm the formation of single phase wurtzite structure and to study the bulk magnetic response of the sample, respectively. Magnetic studies show that Co doped ZnO nanoparticles exhibit ferromagnetism (FM) at room temperature (RT). Furthermore, the electronic structure and element specific magnetic properties were investigated by near-edge X-ray absorption fine structure (NEXAFS) and X-ray magnetic circular dichroism (XMCD) measurements, respectively. The effect of Co substitution on the spectral features of Co-ZnO at O K-edge, Co L 3,2 edge, Zn L 3,2 edge have been investigated. The spectral features of NEXAFS at Co L 3,2 edge is entirely different from the spectral features of metallic clusters and other impurity phases, which rules out the presence of impurity phases. The valence state of 'Co' ion is found to be in +2 state. The FM nature of the sample was confirmed through XMCD spectra, which is due to the incorporation of divalent 'Co' ions. Hence the presented results confirm the substitution of 'Co' ions at 'Zn' site in the host lattice, which is responsible for the RTFM.

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“…With angle-dependence XAS studies, it has been well documented that the feature B 3 originated from the O 1s to O 2p π orbital transition, which lies along the c axis of the QDs. 49,50 The decrease of the particle size made the particle much closer to the sphere and no favorable orbital orientation existed. As a consequence, the poor alignment between the O 2p π orbital and electric field was obtained, inducing the lower intensity of peaks B 3 .…”

Section: Studies Of Pristine 3d Tmos: Size Effects On the Tio 2 Fe mentioning

confidence: 99%

X-ray spectroscopies studies of the 3d transition metal oxides and applications of photocatalysis

Kapilashrami

Chuang

et al. 2017

MRS Communications

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Abstract:Recent advances in synchrotron based X-ray spectroscopy enable materials scientists to emanate finger prints on important materials properties e.g. electronic, optical, structural and magnetic properties, in real time and under nearly real-world conditions. This characterization in combination with optimized materials synthesis routes and tailored morphological properties could contribute greatly to the advances in solid-state electronics and renewable energy technologies. In connection to this, such perspective reflects the current materials research in the space of emerging energy technologies, namely photocatalysis, with a focus on transition metal oxides (TMOs), mainly on the Fe 2 O 3 and TiO 2 based materials.

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Electronic structure of ZnO nanorods studied by angle-dependent x-ray absorption spectroscopy and scanning photoelectron microscopy

Cited by 106 publications

References 19 publications

Photophysics of Point Defects in ZnO Nanoparticles

Photophysics of Point Defects in ZnO Nanoparticles

Spectroscopic investigation of an intrinsic room temperature ferromagnetism in Co doped ZnO nanoparticles

X-ray spectroscopies studies of the 3d transition metal oxides and applications of photocatalysis

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