Defect‐Induced Optical and Magnetic Properties of Colloidal Transparent Conducting Oxide Nanocrystals

Radovanovic, Pavle V.

doi:10.1002/9783527654864.ch5

Cited by 9 publications

(11 citation statements)

References 95 publications

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“…Doping methods for colloidal nanocrystals, however, are much less developed. Excellent recent reviews on the subject can be found in the literature. − Not surprisingly, because of the high energy required to substitute dopant atoms within the host framework of a nanocrystal, dopants are often excluded from the surface, form new clusters or secondary phases, or are not incorporated into the crystal at all . Because of the inherently small number of atoms in a nanocrystal, small changes in the number of dopant atoms can result in the drastic alteration of properties.…”

Section: Leveraging Living Methods To Achieve Advanced Structural Con...mentioning

confidence: 99%

Living Nanocrystals

2017

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The important properties of polymers and nanocrystals both depend upon the precise control of three-dimensional structure. Living polymerization has transformed polymer chemistryproviding absolute control over molecular weights, yielding monodisperse chains, and enabling the production of copolymers with specifically tailored properties. Despite the apparent analogies between polymerization of organic monomers and nanocrystal growth from inorganic monomers, living growth approaches to nanocrystals have been slower to develop. Living nanocrystal growth methods promise to provide exquisite control over core size, size dispersion, doped composition, and core/shell structure. As a result, they have the potential to advance the development of predictive structure/property relationships and afford a finer level of structural control during nanomaterial synthesis. In this perspective, we outline the essential attributes of living nanocrystal syntheses and discuss prerequisites required to discover and develop reactions with these types of mechanisms. Examples from the literature are reviewed that share some attributes of living growth methods (e.g., seeded growth methods) in an attempt to identify existing approaches that might meet the living growth prerequisites. We describe recent findings from our laboratory on metal oxide nanocrystal synthesis that exhibit all the key attributes of living growth. We demonstrate the potential of this method for enhanced structural and compositional control in nanocrystal growth through examples involving efficient dopant incorporation into a metal oxide framework, precise control of the radial distribution of dopant atoms, and the production of core/shell metal oxide nanocrystals. Finally, we outline exciting future prospects for discovery and development of living growth systems and point out important research avenues critical for development of the field.

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Section: Leveraging Living Methods To Achieve Advanced Structural Con...mentioning

confidence: 99%

Living Nanocrystals

2017

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“…24−27 The questions about the origin of the localized magnetic moment and their potential role in carrier polarization in undoped transparent metal oxide host lattices remain at the forefront of this area of research. 28 For instance, the charge-transfer ferromagnetism model, 18 Stoner-type band splitting in undoped metal oxides and some DMSOs, assumes that paramagnetic species, either defects or dopants, have no essential role as carriers of the magnetic moment. One of the challenges in addressing these questions is the lack of selective and specific experimental design and methodology.…”

Section: ■ Introductionmentioning

confidence: 99%

“…What makes some of the transparent semiconductor metal oxides, including ZnO, SnO 2 , HfO 2 , Al 2 O 3 , and MgO, even more unique is the observation of room temperature ferromagnetism in the absence of magnetic dopants. − Early reports of such “d 0 ferromagnetism” have been considered quite controversial, and the room temperature ferromagnetism has often been attributed to spurious effects such as unintentional magnetic impurities introduced in the sample preparation, processing, or measurements . However, a significant number of experimental and theoretical studies have since reported the same phenomenon. − The questions about the origin of the localized magnetic moment and their potential role in carrier polarization in undoped transparent metal oxide host lattices remain at the forefront of this area of research . For instance, the charge-transfer ferromagnetism model, which has been implicated in Stoner-type band splitting in undoped metal oxides and some DMSOs, assumes that paramagnetic species, either defects or dopants, have no essential role as carriers of the magnetic moment.…”

Section: Introductionmentioning

confidence: 99%

On the Origin of d⁰ Magnetism in Transparent Metal Oxide Nanocrystals

Zhang

Yin

et al. 2021

J. Phys. Chem. C

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Controlling magnetic and magneto-optical properties of transparent metal oxide semiconductors has a significant potential for spintronics and photonics. Although ferromagnetism has been reported for several nanostructured transparent metal oxides in the absence of magnetic dopants, its origin and the nature of the exchange interactions remain controversial. Here, we report a variable-temperature−variable-field magnetic circular dichroism study of ZnO and SnO 2 nanocrystals prepared under oxidizing and reducing conditions. We observe the band splitting in ZnO and SnO 2 nanocrystals induced by localized doublet (S = 1/2) and triplet (S = 1) ground states, respectively. Photoluminescence measurements suggest that these states are associated with oxygen vacancies, either as isolated paramagnetic sites in ZnO or as local vacancy-based complexes in SnO 2 nanocrystals. The results of this work demonstrate the ability to tune carrier polarization in metal oxide nanocrystals by in situ control of the native defect formation and attest to the anomalous Zeeman splitting of the band states, which may play an important role in generating ferromagnetism in this class of materials.

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“…[1][2][3] This richness of properties arises from their complex crystal and electronic structures, [4][5][6][7][8] which can be further modulated by controlling native defect formation or incorporation of impurities (e.g., doping or alloying). 9 One of the striking characteristics of most transparent metal oxides is their robust n-type conductivity. 3 Although these materials possess wide band gaps and should be considered insulators, the presence of suitable native or impurity defects allows for the formation of shallow electron donor states.…”

Section: Introductionmentioning

confidence: 99%

“…These advances have led to the discovery of new phenomena and further expansion of the properties and potential applications of transparent metal oxides. 9 Examples include the generation of localized surface plasmon resonance in TCO nanocrystals (NCs), [15][16][17] room-temperature ferromagnetism in diluted D r a f t magnetic semiconductor oxide (DMSO) NCs, 6,[18][19][20][21][22] size-and composition-tunable light emission, [23][24][25] and selective and efficient photocatalysts. [26][27][28][29][30] Among transparent metal oxides, Ga 2 O 3 is considered the widest band gap semiconductor.…”

Section: Introductionmentioning

confidence: 99%

Defects and impurities in colloidal Ga₂O₃ nanocrystals: new opportunities for photonics and lighting

Nguyen

Radovanovic

2022

Can. J. Chem.

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Defects, both native and extrinsic, critically determine functional properties of metal oxides. Gallium oxide has recently gained significant attention for its promise in microelectronics, owing to the unique combination of conductivity and high breakdown voltage, and solid-state lighting, owing to the strong photoluminescence in the visible spectral region. These properties are associated with the presence of native defects that can form both donor and acceptor states in Ga2O3. Recently, Ga2O3 nanocrystal synthesis in solution and optical glasses has been developed, allowing for a range of new applications in photonics, lighting, and photocatalysis. This review focuses on the structure and properties of Ga2O3 nanocrystals with a particular emphasis on the electronic structure and interaction of defects in reduced dimensions and their role in the observed photoluminescence properties. In addition to native defects, the effect of selected external impurities, including lanthanide and aliovalent dopants, and alloying on the emission properties of Ga2O3 nanocrystals are also discussed.

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Defect‐Induced Optical and Magnetic Properties of Colloidal Transparent Conducting Oxide Nanocrystals

Cited by 9 publications

References 95 publications

Living Nanocrystals

Living Nanocrystals

On the Origin of d⁰ Magnetism in Transparent Metal Oxide Nanocrystals

Defects and impurities in colloidal Ga₂O₃ nanocrystals: new opportunities for photonics and lighting

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Defect‐Induced Optical and Magnetic Properties of Colloidal Transparent Conducting Oxide Nanocrystals

Cited by 9 publications

References 95 publications

Living Nanocrystals

Living Nanocrystals

On the Origin of d0 Magnetism in Transparent Metal Oxide Nanocrystals

Defects and impurities in colloidal Ga2O3 nanocrystals: new opportunities for photonics and lighting

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On the Origin of d⁰ Magnetism in Transparent Metal Oxide Nanocrystals

Defects and impurities in colloidal Ga₂O₃ nanocrystals: new opportunities for photonics and lighting