Transition‐Metal Doped Zinc Oxide Nanowires

Yuhas, Benjamin D.; Zitoun, David; Pauzauskie, Peter J.; He, Rongrui; Yang, Peidong

doi:10.1002/anie.200503172

Cited by 209 publications

(156 citation statements)

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“…This preedge feature has been attributed to the presence of an inversion center; 17 we thus see that the TM coordination in the nanowire is not octahedral, unlike in the precursor. A tetrahedral coordination is readily confirmed by electronic absorption or photoluminescence spectroscopy, 13,[18][19][20] as well as the EXAFS measurements discussed below. Finally, we observe identical NEXAFS transmission spectra whether we collect from the trunk region of the nanowire bundles or the individual nanowires themselves, regardless of the concentration or identity of the dopant.…”

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confidence: 76%

“…13 Zinc acetate and the desired TM(II) acetate were dissolved in trioctylamine at 310°C and reacted for 3 h. The nanowires had uniform diameters of 35 ( 5 nm, and lengths ranging from 2 to 6 µm, depending on the type and amount of TM dopant. Average dopant concentrations were determined by energy-dispersive X-ray spectroscopy (EDX) in a Philips CM200 transmission electron microscope.…”

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confidence: 99%

“…tration gradient by EDX in any of the nanowire samples. 13 The nanowire magnetic properties were measured in powder form using a SQUID magnetometer (Quantum Design MPMS XL); the results are displayed in Figure 1. Both the Co and Mn-doped wires can be described as weak ferromagnets with an additional paramagnetic component.…”

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confidence: 99%

“…In all cases, we observed a uniform X-ray absorption signal, both across several nanowire bundles as well as within a single bundle, implying that the dopant is very evenly distributed throughout the nanowire sample, which is consistent with our previous EDX observations. 13 Differences in intensity can be attributed to the varying thickness of the nanowire sample; this is a consequence of the growth mechanism, which features several nanowires growing in a pan-pipe geometry from a common, thicker hexagonal base. 13 Figure 2D shows the cobalt NEXAFS spectra obtained from various regions in the nanowire samples ( Figure 2C), along with that of the cobalt precursor, cobalt(II) acetate.…”

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confidence: 99%

“…13 Differences in intensity can be attributed to the varying thickness of the nanowire sample; this is a consequence of the growth mechanism, which features several nanowires growing in a pan-pipe geometry from a common, thicker hexagonal base. 13 Figure 2D shows the cobalt NEXAFS spectra obtained from various regions in the nanowire samples ( Figure 2C), along with that of the cobalt precursor, cobalt(II) acetate.…”

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Probing the Local Coordination Environment for Transition Metal Dopants in Zinc Oxide Nanowires

et al. 2007

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It is hypothesized that a highly ordered, relatively defect-free dilute magnetic semiconductor system should act as a weak ferromagnet. Transition-metal-doped ZnO nanowires, being single crystalline, single domain, and single phase, are used here as a model system for probing the local dopant coordination environments using X-ray absorption spectroscopy and diffraction. Our X-ray spectroscopic data clearly show that the dopant resides in a uniform environment, and that the doping does not induce a large degree of disorder in the nanowires. This homogeneous nature of the doping inside the oxide matrix correlates well with observed weakly ferromagnetic behavior of the nanowires.Dilute magnetic semiconductors are of great current research interest owing to their novel magnetic properties. These materials are envisioned to have potential use in so-called "spintronic" devices, in which one seeks to control both the charge and spin degrees of freedom of the electron; a few such prototypical devices are already in existence. 1,2 Despite improvements in device fabrication, the fundamental questions regarding the origins of the magnetic behavior in dilute magnetic semiconducting (DMS) systems remain unsatisfactorily answered. It is known that much of the controversy has stemmed from the fact that clustering or phase separation of the magnetic dopant ions can result in magnetic data that is misleading or unreliable. [3][4][5] Even in systems that appear to be quite pure, reported magnetic behavior can vary widely, ranging from room-temperature ferromagnetism 6 to no magnetic ordering at all. 7,8 This variance in magnetism is attributed to the multitude of synthetic methods used for the production of DMS materials, which can result in differences in dopant environment, structural disorder, or carrier concentration. Therefore, to extract the most accurate information from any magnetic data on a DMS material, it is vital to perform a rigorous structural characterization.A combination of X-ray spectro-microscopy and X-ray diffraction (XRD) techniques can provide excellent insight into the structure of a DMS system, down to the local environment of the magnetic cation. Although these types of experiments have been conducted previously on bulk and thin film systems of DMS materials, 9-12 very few studies on one-dimensional nanostructures of transition-metal (TM)-doped semiconductors have been reported. In this Letter, we report results of a detailed structural analysis on TM-doped (Co and Mn) ZnO nanowires grown by a novel solutionbased synthesis, and we correlate these findings with the magnetic properties of the nanowires. These transition-metaldoped ZnO nanowires, being single crystalline, single domain, and single phase, serVe as an excellent model system for probing the local dopant coordination enVironments and their correlation with magnetic properties. XRD, microextended X-ray absorption fine structure spectroscopy (µ-EXAFS), as well as high-resolution imaging combined with near-edge X-ray absorption fine struct...

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Probing the Local Coordination Environment for Transition Metal Dopants in Zinc Oxide Nanowires

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Colloidal Semiconductor Nanowires

Sun

et al. 2012

One‐Dimensional Nanostructures

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Solvent Dependent Shape and Magnetic Properties of Doped ZnO Nanostructures

Clavel

Willinger

Zitoun

et al. 2007

Adv Funct Materials

117

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This study reports on a new solution phase synthesis leading to cobalt and manganese doped ZnO which have been theoretically predicted ferromagnetic at room temperature. The solvothermal synthesis involving the reaction of zinc and cobalt acetate or manganese oleate with benzyl alcohol leads to pure inorganic nanoparticles that are diluted magnetic semiconductors. The addition of an inert solvent, that is used in order to control the amount of benzyl alcohol, drastically influences the particles morphology and strongly affects the magnetic behaviors. Cobalt doped particles are paramagnetic or ferromagnetic depending on the synthesis conditions. In order to exclude the formation of secondary phases and/or metal clusters and to understand the role of the solvent on the magnetic properties, the local structure of Co 2+ and Mn 2+ in the wurtzite ZnO matrix were characterized by XRD, UV-Visible diffuse reflectance and electron paramagnetic resonance.

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Transition‐Metal Doped Zinc Oxide Nanowires

Cited by 209 publications

References 29 publications

Probing the Local Coordination Environment for Transition Metal Dopants in Zinc Oxide Nanowires

Probing the Local Coordination Environment for Transition Metal Dopants in Zinc Oxide Nanowires

Colloidal Semiconductor Nanowires

Solvent Dependent Shape and Magnetic Properties of Doped ZnO Nanostructures

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