ORCID Profile
0000-0002-4902-5589
Current Organisation
Hong Kong University of Science and Technology
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Publisher: AIP Publishing
Date: 15-10-2003
DOI: 10.1063/1.1621459
Abstract: Ultrathin Fe nanowire (about 5 nm in diameter) arrays have been fabricated by electrodeposition using anodic porous alumina templates. These ultrathin nanowires exhibited uniaxial anisotropy and a quite large coercivity (4190 Oe) at 5 K. In addition, the field needed to saturate the magnetization, when the field was applied perpendicularly to the easy axis, was much larger than the shape anisotropy field (2πMS). This saturation field increased with decreasing temperature. We believed that this enhanced saturation field was mainly due to the contribution of the surface spins.
Publisher: Springer Science and Business Media LLC
Date: 27-07-2018
DOI: 10.1038/S41467-018-04903-4
Abstract: Creating oxide interfaces with precise chemical specificity at the atomic layer level is desired for the engineering of quantum phases and electronic applications, but highly challenging, owing partially to the lack of in situ tools to monitor the chemical composition and completeness of the surface layer during growth. Here we report the in situ observation of atomic layer-by-layer inner potential variations by analysing the Kikuchi lines during epitaxial growth of strontium titanate, providing a powerful real-time technique to monitor and control the chemical composition during growth. A model combining the effects of mean inner potential and step edge density (roughness) reveals the underlying mechanism of the complex and previously not well-understood reflection high-energy electron diffraction oscillations observed in the shuttered growth of oxide films. General rules are proposed to guide the synthesis of atomically and chemically sharp oxide interfaces, opening up vast opportunities for the exploration of intriguing quantum phenomena at oxide interfaces.
Publisher: American Chemical Society (ACS)
Date: 30-10-2019
Publisher: AIP Publishing
Date: 24-08-2020
DOI: 10.1063/5.0020597
Abstract: Single-crystalline vanadium dioxide nanowires (VO2 NWs) have attracted significant interest due to their unique characteristics, which originate from the single-domain metal–insulator phase transition (MIT) property. However, the lack of facile technologies to produce vertical nanowire arrays (NAs) in a large area has limited the mass fabrication of VO2-based devices. Here, an antimony-assisted hydrothermal method is developed for the low-temperature production of wafer-scale vertical VO2 NAs on arbitrary substrates of glass, quartz, and silicon. Sb2O3 plays a key role in the controlled growth of pure VO2 (M1) by modulating the size, density, alignment, and MIT properties of VO2 NAs. Furthermore, the growth mechanism of vertical VO2 NAs is explained. In contrast to conventional fabrication technologies, the weak interaction between NA films and substrates enables a much easier transfer of VO2 NAs for various potential applications.
Publisher: American Chemical Society (ACS)
Date: 20-12-2017
Abstract: Morphology management for tailoring the properties of monolayer transition-metal dichalcogenides (TMDCs), that is, molybdenum disulfide (MoS
Publisher: American Chemical Society (ACS)
Date: 05-04-2021
Publisher: American Chemical Society (ACS)
Date: 20-12-2016
Abstract: Monolayer MoS
Publisher: Springer Science and Business Media LLC
Date: 05-01-2016
DOI: 10.1038/SREP18886
Abstract: Ordered nanoarchitectures have attracted an intense research interest recently because of their promising device applications. They are always fabricated by self-assembling building blocks such as nanowires, nanodots. This kind of bottom up approaches is limited in poor control over height, lateral resolution, aspect ratio and patterning. Here, we break these limits and realize 3D sculpturing of vertical ZnO nanowire arrays (NAs) based on the conventional photolithography approach. These are achieved by immersing nanowire NAs in thick photoresist (PR) layers, which enable the cutting and patterning of ZnO NAs as well as the tailoring of NAs. Our strategy of 3D sculpturing of NAs promisingly paves the way for designing novel NAs-based nanoarchitectures.
Publisher: Springer Science and Business Media LLC
Date: 09-07-2021
DOI: 10.1038/S41467-021-24527-5
Abstract: A systematic study of various metal-insulator transition (MIT) associated phases of VO 2 , including metallic R phase and insulating phases (T, M1, M2), is required to uncover the physics of MIT and trigger their promising applications. Here, through an oxide inhibitor-assisted stoichiometry engineering, we show that all the insulating phases can be selectively stabilized in single-crystalline VO 2 beams at room temperature. The stoichiometry engineering strategy also provides precise spatial control of the phase configurations in as-grown VO 2 beams at the submicron-scale, introducing a fresh concept of phase transition route devices. For instance, the combination of different phase transition routes at the two sides of VO 2 beams gives birth to a family of single-crystalline VO 2 actuators with highly improved performance and functional ersity. This work provides a substantial understanding of the stoichiometry-temperature phase diagram and a stoichiometry engineering strategy for the effective phase management of VO 2 .
Publisher: American Chemical Society (ACS)
Date: 20-09-2019
Publisher: Springer Science and Business Media LLC
Date: 28-09-2016
DOI: 10.1038/SREP33597
Abstract: The superior performance of metal oxide nanocomposites has introduced them as excellent candidates for emerging energy sources and attracted significant attention in recent years. The drawback of these materials is their inherent structural pulverization which adversely impacts their performance and makes the rational design of stable nanocomposites a great challenge. In this work, functional V 2 O 5 -C-SnO 2 hybrid nanobelts (VCSNs) with a stable structure are introduced where the ultradispersed SnO 2 nanocrystals are tightly linked with glucose on the V 2 O 5 surface. The nanostructured V 2 O 5 acts as a supporting matrix as well as an active electrode component. Compared with existing carbon-V 2 O 5 hybrid nanobelts, these hybrid nanobelts exhibit a much higher reversible capacity and architectural stability when used as anode materials for lithium-ion batteries. The superior cyclic performance of VCSNs can be attributed to the synergistic effects of SnO 2 and V 2 O 5 . However, limited data are available for V 2 O 5 -based anodes in lithium-ion battery design.
Publisher: American Chemical Society (ACS)
Date: 03-06-2020
Publisher: Springer Science and Business Media LLC
Date: 25-02-2014
DOI: 10.1038/SREP04181
Abstract: We studied the photocatalytic properties of rational designed TiO 2 -ZnO hybrid nanostructures, which were fabricated by the site-specific deposition of amorphous TiO 2 on the tips of ZnO nanorods. Compared with the pure components of ZnO nanorods and amorphous TiO 2 nanoparticles, these TiO 2 -ZnO hybrid nanostructures demonstrated a higher catalytic activity. The strong green emission quenching observed from photoluminescence of TiO 2 -ZnO hybrid nanostructures implied an enhanced charge transfer/separation process resulting from the novel type II heterostructures with fine interfaces. The catalytic performance of annealing products with different TiO 2 phase varied with the annealing temperatures. This is attributed to the combinational changes in E g of the TiO 2 phase, the specific surface area and the quantity of surface hydroxyl groups.
Publisher: American Chemical Society (ACS)
Date: 25-02-2020
Publisher: Springer Science and Business Media LLC
Date: 04-02-2015
DOI: 10.1038/SREP08226
Abstract: Hierarchical ZnO nanostructures with a large yield were fabricated by a simple thermal evaporation method. For the first time, novel ZnO flowers were observed blooming at certain sites of a variety of spines, identified as Zn-terminated polar (0001) planes or tips. The spines for as-synthesized hierarchical structures can be nanowires, nanobelts, nanodendrites, nanobrushes, etc. This growth phenomenon determines the key role of polar sites in the fabrication of hierarchical structures. The spiral feature of ZnO flowers indicates an unusual screw dislocation driven growth mechanism, which is attributed to a high concentration of Zn vapor.
Publisher: AIP Publishing
Date: 03-2019
DOI: 10.1063/1.5087864
Abstract: Vanadium dioxide (VO2), with the first-order metal-insulator phase transition at near room temperature, has attracted increasing attention in the past few decades. With rapid electrical switching, the phase transition in VO2 also triggers the colossal property changes in various aspects, such as optical properties, magnetic properties, and strain, and, thus, enables a wide range of modern applications. In this review, we present a complete picture of the latest advances of VO2, including the fabrication strategies, property modulation, and advanced applications. This review summarizes several typical fabrication methods of VO2 crystals as well as some common problems and their possible solutions. The strategies for the fabrication of single-crystalline VO2 arrays are also discussed to meet the requirements of the high-performance devices at the macro-scale. This review concerns the typical approaches for the modulation of (metal-insulator transition) MIT and emphasizes on the domain study of VO2 single crystals at the nanoscale. We aim at a clear explanation of the effect of various inhomogeneities on the MIT behavior of VO2 and the importance of the accurate control of MIT at the domain level. After summarizing the preparation and modification of VO2, we focus on the applications of this amazing smart material in various aspects, including strain engineering, optical modulation, electrical switching, and multi-responsive sensing.
Publisher: American Chemical Society (ACS)
Date: 03-07-2019
No related grants have been discovered for Ning Wang.