Atomic-Scale Electronic Characterization of Defects in Silicon Carbide Nanowires by Electron Energy-Loss Spectroscopy

Luna, Lunet E.; Gardner, David P.; Radmilović, Velimir; Maboudian, Roya; Carraro, Carlo

doi:10.1021/acs.jpcc.8b01661

Cited by 6 publications

(4 citation statements)

References 40 publications

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“…Lately, more focus has been shifted to anion vacancies in high-temperature solid reactions. , Oxygen and/or halogen atom vacancies lead to a deviation from the stoichiometry to some degree. The defective center can be inferred through experimental measurements via, e.g., X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), positron annihilation spectroscopy (PAS), and electron energy loss spectroscopy (EELS) via atomic-level resolution of transmission electron microscopy (TEM), but how can we assign these charge transitions and ascertain the defect levels that are responsible for the emission? Inspired by recent studies in semiconductors, computational studies in combination with experimental efforts can yield insightful and quantitative details about the impact of point defects. ,,− The defect-induced electronic states and broad emission bands as a result of different chemical bonding environments in the ground and excited states can also be undertaken using this approach …”

Section: Introductionmentioning

confidence: 99%

Fine-Tunable Self-Activated Luminescence in Apatite-Type (Ba,Sr)₅(PO₄)₃Br and the Defect Process

Zhang¹,

Zhang

Qiu³

et al. 2018

Inorg. Chem.

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Intrinsic defect-related luminescence has recently been attracting more research interest for the modification of phosphors. However, the connection between defect formation and crystal structure has never been considered. In this work, we report that in the absence of an impurity activator, under a reducing atmosphere, apatite-type compound M(PO)X (M = Ca, Sr, or Ba; X = F, Cl, or Br) can emit tunable colors ranging from blue to orange depending on the content of M and X. To better understand the cause, BaSr (PO)Br (BSPOB; m = 0-5) solid solutions were analyzed in detail. The dependency of self-activated luminescence on atmospheric conditions and solid solution compositions was investigated by combining experimental characterizations and theoretical calculations using density functional theory. Crystal structures of these solid solutions were verified by X-ray diffraction patterns as well as Rietveld refinements. With the defect formation energy and electron paramagnetic resonance measurement, we propose that an oxygen vacancy (V) should be mainly responsible for the peculiar super wide band emission. Moreover, the enhanced distortion of solid solution crystal structures augments V concentrations and leads to luminescence intensities in solid solutions that are higher than that in end point compounds. Variations of the electronic structure of BSPOB matrices with gradual tuning of the Sr/Ba ratio were also investigated. As a result, the introduction of V defect levels within the band gap leads to the formation of donors and acceptors, allowing for a modulation of the photoluminescence throughout the visible part of the spectrum. As the first report in the literature to demonstrate fine-tunable emissions over a wide wavelength range as a consequence of native defective levels in a series of continuous apatite-type solid solutions, our results illustrate the feasibility of defect-meditated systems by carefully tailoring defect chemistry and nonstoichiometric chemical composition under controlled conditions to engineer phosphor properties.

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Section: Introductionmentioning

confidence: 99%

Fine-Tunable Self-Activated Luminescence in Apatite-Type (Ba,Sr)₅(PO₄)₃Br and the Defect Process

Zhang¹,

Zhang

Qiu³

et al. 2018

Inorg. Chem.

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“…In fact, a similar band gap has been recorded in defective 2H-SiC nanowires very recently. 28 Another remarkable feature is the relatively sharp tip of the CBM curve in 9R-SiC which indicates a smaller effective electron mass. 15R-SiC is already known to have a higher electron mobility than most SiC polytypes, 29 and therefore 9R-SiC is expected to be even more attractive for device applications.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…The resulting value (∼3.4 eV) is clearly higher than that of 2H-SiC and is similar to that of GaN, suggesting that 9R-SiC would be a good candidate for high-frequency applications. In fact, a similar band gap has been recorded in defective 2H-SiC nanowires very recently . Another remarkable feature is the relatively sharp tip of the CBM curve in 9R-SiC which indicates a smaller effective electron mass.…”

Section: Resultsmentioning

confidence: 99%

Predicting the Primitive Form of Rhombohedral Silicon Carbide (9R-SiC): A Pathway toward Polytypic Heterojunctions

Yaghoubi

Singh

Mélinon

2018

Crystal Growth & Design

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The simplest form of rhombohedral silicon carbide is unknown. Previous studies of the elusive 9R-SiC have failed to show whether this polytype is stable as a bulk material. Here, we demonstrate that when molecular bonds along the caxis of 2H-SiC are broken under tension, miniscule levels of stacking fault could give rise to the formation of 9R polytype and hence a Type II heterojunction. 9R-SiC has a very similar microscopic and crystallographic signature to that of 3C-SiC and 15R-SiC, respectively, which explains why it has evaded detection until now. Its vibrational footprint on the other hand is quite distinct thanks to its fewer active phonon modes. Surprisingly, the indirect band gap of this polytype is slightly wider than that of 2H-SiC, despite its lower hexagonality, and is equivalent to that of GaN. Due to its unique conduction band structure, 9R-SiC may also exhibit improved electron transport properties as compared to other SiC polytypes, and therefore could be suitable for highfrequency and high-voltage applications.

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“…It is shown that the adjacent stacking faults do not affect the bandgap of the wurtzite regions. For the zinc-blende parts, in contrast, the bandgap is influenced by the thickness of the segments [164].…”

Section: Physical Propertiesmentioning

confidence: 98%

Understanding semiconductor nanostructures via advanced electron microscopy and spectroscopy

Zamani

Arbiol

2019

Nanotechnology

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Transmission electron microscopy (TEM) offers an ample range of complementary techniques which are able to provide essential information about the physical, chemical and structural properties of the materials at the atomic scale, and make a vast impact on our understanding of materials science, especially in the field of semiconductor 1-dimensional (1D) nanostructures. Recent advancements in TEM instrumentation, in particular aberration correction and monochromation, have enabled pioneering experiments in complex nanostructure material systems. This Review aims to address these understandings through the applications of the methodology for semiconductor nanostructures. It points up various electron microscopy techniques, in particular scanning TEM (STEM) imaging and spectroscopy techniques, with their already-employed or potential applications on 1D nanostructured semiconductors. We keep the main focus of the paper on the electronic and optoelectronic properties of such semiconductors, and avoid expanding it further. In the first part of the paper, we give a brief introduction to each of the STEM-based techniques, without detailed elaboration, and mention the recent technological and conceptual developments which lead to novel characterization methodologies. For further reading, we refer the audience to a handful of papers in the literature. In the second part, we highlight the recent examples of application of the STEM methodology on the 1D nanostructure semiconductor materials, especially III-V, II-V, and group IV bare and heterostructure systems. The aim is to address the research questions on various physical properties and introduce solutions by choosing the appropriate technique that can answer the questions. Potential applications will also be discussed, the ones that have already been used for bulk and 2D materials, and have shown great potential and promise for 1D nanostructure semiconductors.

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Atomic-Scale Electronic Characterization of Defects in Silicon Carbide Nanowires by Electron Energy-Loss Spectroscopy

Cited by 6 publications

References 40 publications

Fine-Tunable Self-Activated Luminescence in Apatite-Type (Ba,Sr)₅(PO₄)₃Br and the Defect Process

Fine-Tunable Self-Activated Luminescence in Apatite-Type (Ba,Sr)₅(PO₄)₃Br and the Defect Process

Predicting the Primitive Form of Rhombohedral Silicon Carbide (9R-SiC): A Pathway toward Polytypic Heterojunctions

Understanding semiconductor nanostructures via advanced electron microscopy and spectroscopy

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Atomic-Scale Electronic Characterization of Defects in Silicon Carbide Nanowires by Electron Energy-Loss Spectroscopy

Cited by 6 publications

References 40 publications

Fine-Tunable Self-Activated Luminescence in Apatite-Type (Ba,Sr)5(PO4)3Br and the Defect Process

Fine-Tunable Self-Activated Luminescence in Apatite-Type (Ba,Sr)5(PO4)3Br and the Defect Process

Predicting the Primitive Form of Rhombohedral Silicon Carbide (9R-SiC): A Pathway toward Polytypic Heterojunctions

Understanding semiconductor nanostructures via advanced electron microscopy and spectroscopy

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Fine-Tunable Self-Activated Luminescence in Apatite-Type (Ba,Sr)₅(PO₄)₃Br and the Defect Process

Fine-Tunable Self-Activated Luminescence in Apatite-Type (Ba,Sr)₅(PO₄)₃Br and the Defect Process