Epitaxial NiO nanocrystals: a dimensional analysis

Cheung, J. T.; Okatan, M. Baris; Sullaphen, Jivika; Cheng, Xuan; Valanoor, Nagarajan; Chen, Yong Lun; Chu, Ying Hao

doi:10.1557/mrc.2013.16

Cited by 3 publications

(5 citation statements)

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“…To get the precise result, it is necessary to obtain a full histogram profile of height and width, followed by numerical analysis to reach a statistic value of the ratio of height and width. This has been shown in our previous paper ref , which gave a mean value for the nonstoichiometric NiO crystal with a height and width of 30 and 50 nm, respectively, and a ratio of 0.6. This ratio is approximately the ratio (0.62) measured from the crystal in Figure A.…”

Section: Experimental Results and Discussion: Tem Observation Of Nio ...supporting

confidence: 80%

“…To test the theory developed in Section , we investigated NiO nanostructures, 10–100 nm wide and up to 30 nm in height, epitaxially grown on (001) STO substrates. The statistical size analysis and related details can be found elsewhere. , Briefly, although over 100 nanocrystals were analyzed, the NiO nanocrystal morphology reveals a strong binary distribution of shape either “near-spherical crown” or a quadrangular pyramid. These two cases of NiO morphology can be considered as the extreme cases of different interface conditions, that is, one is dominated fully by the elastic misfit energy at the interface (crown), while the other is dominated by dislocation energy at the interface (pyramid).…”

Section: Experimental Results and Discussion: Tem Observation Of Nio ...mentioning

confidence: 99%

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Predicting Epitaxial Nanocrystal Morphology Governed by Interfacial Strain—The Case for NiO on SrTiO₃

2021

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The shape dependence for the technologically important nickel oxide (NiO) nanocrystals on (001) strontium titanate substrates is investigated under the generalized Wulff-Kaichew (GWK) theorem framework. It is found that the shape of the NiO nanocrystals is primarily governed by the existence (or absence) of interfacial strain. Nanocrystals that have a fully pseudomorphic interface with the substrate (i.e. the epitaxial strain is not relaxed) form an embedded smooth ball-crown morphology with {001}, {011}, {111} and high-index {113} exposed facets with a negative Wulff point. On the other hand, when the interfacial strain is relaxed by misfit dislocations, the nanocrystals take on a truncated pyramidal shape, bounded by {111} faces and a {001} flat top, with a positive Wulff point. Our quantitative model is able to predict both experimentally observed shapes and sizes with good accuracy. Given the increasing demand for hetero-epitaxial nanocrystals in various physio-chemical and electro-chemical functional devices, these results lay the important groundwork in exploiting the GWK theorem as a general analytical approach to explain hetero-epitaxial nanocrystal growth on oxide substrates governed by interface strain.

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Section: Experimental Results and Discussion: Tem Observation Of Nio ...supporting

confidence: 80%

Section: Experimental Results and Discussion: Tem Observation Of Nio ...mentioning

confidence: 99%

Predicting Epitaxial Nanocrystal Morphology Governed by Interfacial Strain—The Case for NiO on SrTiO₃

2021

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“…The origin of this shape dependence can be found in Ref. 30. The TEM image in Figure 1(c) reveals distinct facets that bound the nanocrystal.…”

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Role of interface structure and chemistry in resistive switching of NiO nanocrystals on SrTiO3

et al. 2014

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Nickel oxide (NiO) nanocrystals epitaxially grown on (001) strontium titanate (SrTiO3) single crystal substrates were characterized to investigate interface morphology and chemistry. Aberration corrected high angle annular dark field scanning transmission electron microscopy reveals the interface between the NiO nanocrystals and the underlying SrTiO3 substrate to be rough, irregular, and have a lower average atomic number than the substrate or the nanocrystal. Energy dispersive x-ray spectroscopy and electron energy loss spectroscopy confirm both chemical disorder and a shift of the energy of the Ti L2,3 peaks. Analysis of the O K edge profiles in conjunction with this shift, implies the presence of oxygen vacancies at the interface. This sheds light into the origin of the previously postulated minority carriers’ model to explain resistive switching in NiO [J. Sullaphen, K. Bogle, X. Cheng, J. M. Gregg, and N. Valanoor, Appl. Phys. Lett. 100, 203115 (2012)].

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“…The fabrication, functional properties, and other crystallographic features of the STO-supported NiO nanoislands have been reported elsewhere. , Before annealing, the NiO nanoislands have heights as small as 9 nm and average lateral sizes of 15 nm. After annealing, their average heights and lateral sizes are 30 and 60 nm, respectively . The typical height of STO caldera surrounding NiO nanoislands is about 3–4 STO unit cells for as-grown (unannealed) samples, but it can reach up to 15 STO unit cells after annealing.…”

Section: Resultsmentioning

confidence: 99%

“…After annealing, their average heights and lateral sizes are 30 and 60 nm, respectively. 31 The typical height of STO caldera surrounding NiO nanoislands is about 3−4 STO unit cells for as-grown (unannealed) samples, but it can reach up to 15 STO unit cells after annealing. This indicates that annealing activates the further growth of both the NiO islands and their associated "calderas".…”

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Encapsulation of Metal Oxide Nanoparticles by Oxide Supports during Epitaxial Growth

Cheng

Cheang-Wong

Weyland

et al. 2019

ACS Appl. Electron. Mater.

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The traditional view of complex oxide heteroepitaxy is that the substrate is merely a passive bystander. Here we show that this is not always the case, in particular for a metal oxide/metal oxide interface during the synthesis of epitaxial nickel oxide (NiO) nanoislands on (001) strontium titanate (SrTiO 3 −STO) single crystal substrates. We find that the substrate atoms are driven to encapsulate the metal oxide nanocrystal islandsa phenomenon more commonly reported for metal/metal oxide heterogeneous catalysis where the migration of atoms from the support onto the functional nanoparticle system is driven by strong metal− support interactions (SMSI). High-resolution transmission electron microscopy (HRTEM), high angle angular dark field (HAADF) scanning transmission electron microscopy (STEM), and electron tomography (ET) are used to reveal a clear physical displacement of the interface; the atoms from the STO substrate climb and cover the bottom facets of NiO nanoparticles during the synthesis process during which a unique caldera-shaped structure is formed. It is postulated that this phenomenon occurs to lower the work function and surface energy of the system. These results indicate that the SMSI could be important in the metal oxide/metal oxide systems. In this way changes to the substrate−film interface could be exploited by controlling and modifying the properties of nanoscaled functional oxides.

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Epitaxial NiO nanocrystals: a dimensional analysis

Abstract: Abstract

Cited by 3 publications

References 20 publications

Predicting Epitaxial Nanocrystal Morphology Governed by Interfacial Strain—The Case for NiO on SrTiO₃

Predicting Epitaxial Nanocrystal Morphology Governed by Interfacial Strain—The Case for NiO on SrTiO₃

Role of interface structure and chemistry in resistive switching of NiO nanocrystals on SrTiO3

Encapsulation of Metal Oxide Nanoparticles by Oxide Supports during Epitaxial Growth

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Epitaxial NiO nanocrystals: a dimensional analysis

Abstract: Abstract

Cited by 3 publications

References 20 publications

Predicting Epitaxial Nanocrystal Morphology Governed by Interfacial Strain—The Case for NiO on SrTiO3

Predicting Epitaxial Nanocrystal Morphology Governed by Interfacial Strain—The Case for NiO on SrTiO3

Role of interface structure and chemistry in resistive switching of NiO nanocrystals on SrTiO3

Encapsulation of Metal Oxide Nanoparticles by Oxide Supports during Epitaxial Growth

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Predicting Epitaxial Nanocrystal Morphology Governed by Interfacial Strain—The Case for NiO on SrTiO₃

Predicting Epitaxial Nanocrystal Morphology Governed by Interfacial Strain—The Case for NiO on SrTiO₃