ORCID Profile
0000-0001-9642-8674
Current Organisation
Argonne National Laboratory
Does something not look right? The information on this page has been harvested from data sources that may not be up to date. We continue to work with information providers to improve coverage and quality. To report an issue, use the Feedback Form.
Publisher: American Chemical Society (ACS)
Date: 25-06-2015
DOI: 10.1021/ACS.NANOLETT.5B01471
Abstract: Epitaxial strain provides a powerful approach to manipulate physical properties of materials through rigid compression or extension of their chemical bonds via lattice-mismatch. Although symmetry-mismatch can lead to new physics by stabilizing novel interfacial structures, challenges in obtaining atomic-level structural information as well as lack of a suitable approach to separate it from the parasitical lattice-mismatch have limited the development of this field. Here, we present unambiguous experimental evidence that the symmetry-mismatch can be strongly controlled by dimensionality and significantly impact the collective electronic and magnetic functionalities in ultrathin perovskite LaCoO3/SrTiO3 heterojunctions. State-of-art diffraction and microscopy reveal that symmetry breaking dramatically modifies the interfacial structure of CoO6 octahedral building-blocks, resulting in expanded octahedron volume, reduced covalent screening, and stronger electron correlations. Such phenomena fundamentally alter the electronic and magnetic behaviors of LaCoO3 thin-films. We conclude that for epitaxial systems, correlation strength can be tuned by changing orbital hybridization, thus affecting the Coulomb repulsion, U, instead of by changing the band structure as the common paradigm in bulks. These results clarify the origin of magnetic ordering for epitaxial LaCoO3 and provide a route to manipulate electron correlation and magnetic functionality by orbital engineering at oxide heterojunctions.
Publisher: Wiley
Date: 24-09-2020
Abstract: Ever‐increasing demand on electronic devices with ultrahigh‐density non‐volatile data storage has attracted great interest in novel ferroelectric memories based on conductive ferroelectric domain walls. Embedded in an insulating material, ferroelectric domain walls have the capability of being (re)created, displaced, erased, and altered in their spatial configurations and electronic characteristics. However, the domain wall conductivities are in most cases not yet sufficiently high to ensure the current density required to drive read‐out circuits operating at high speeds. In this work, a giant domain wall current ( µA) of a single charged domain wall is obtained through conductive atomic force microscopy with a bias field of 4 V. This is achieved in self‐assembled BiFeO 3 nanocrystals grown by sol‐gel method on Nb‐doped SrTiO 3 substrates. Local configurations of domains and domain wall types are studied using vector piezoresponse force microscopy and high‐resolution transmission electronic microscopy. The enhancement of the wall current is shown to be due to the formation of conducting pathways of charged defects accumulated along domain walls and traversing the nanocrystals. The erse domain walls can be manipulated by electric field in a perpendicular architecture. The perpendicular array structure of BiFeO 3 nanocrystals should have great potentials for developing perpendicular nanoelectronic prototypes.
Publisher: Springer Science and Business Media LLC
Date: 16-12-2019
Publisher: American Chemical Society (ACS)
Date: 13-10-2016
Abstract: Sn-doped In
Publisher: The Optical Society
Date: 20-10-2016
DOI: 10.1364/OL.41.004895
Publisher: American Chemical Society (ACS)
Date: 30-10-2012
DOI: 10.1021/NN303355B
Abstract: The nanoscale interactions of room temperature ionic liquids (RTILs) at uncharged (graphene) and charged (muscovite mica) solid surfaces were evaluated with high resolution X-ray interface scattering and fully atomistic molecular dynamics simulations. At uncharged graphene surfaces, the imidazolium-based RTIL ([bmim(+)][Tf(2)N(-)]) exhibits a mixed cation/anion layering with a strong interfacial densification of the first RTIL layer. The first layer density observed via experiment is larger than that predicted by simulation and the apparent discrepancy can be understood with the inclusion of, dominantly, image charge and π-stacking interactions between the RTIL and the graphene sheet. In contrast, the RTIL structure adjacent to the charged mica surface exhibits an alternating cation-anion layering extending 3.5 nm into the bulk fluid. The associated charge density profile demonstrates a pronounced charge overscreening (i.e., excess first-layer counterions with respect to the adjacent surface charge), highlighting the critical role of charge-induced nanoscale correlations of the RTIL. These observations confirm key aspects of a predicted electric double layer structure from an analytical Landau-Ginzburg-type continuum theory incorporating ion correlation effects, and provide a new baseline for understanding the fundamental nanoscale response of RTILs at charged interfaces.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 13-12-2019
Abstract: Two-dimensional polymers can be made as monolayer sheets through controlled synthesis at an interface. However, it is often difficult to create intact sheets over large areas that can be transferred onto substrates. Zhong et al. polymerized derivatized porphyrin molecules during laminar flow at a sharp pentane-water interface to form sheets that are 5 centimeters in diameter (see the Perspective by MacLean and Rosei). The authors used electron microscopy and spectroscopy to confirm that they had produced intact monolayers. These films were then transferred onto monolayer sheets of molybdenum disulfide to form superlattices for use as capacitors. Science , this issue p. 1379 see also p. 1308
Publisher: American Chemical Society (ACS)
Date: 24-04-2018
Abstract: Transparent flexible electrodes are in ever-growing demand for modern stretchable optoelectronic devices, such as display technologies, solar cells, and smart windows. Such sandwich-film-electrodes deposited on polymer substrates are unattainable because of the low quality of the films, inducing a relatively large optical loss and resistivity as well as a difficulty in elucidating the interference behavior of light. In this article, we report a high-quality AZO/Au/AZO sandwich film with excellent optoelectronic performance, e.g., an average transmittance of about 81.7% (including the substrate contribution) over the visible range, a sheet resistance of 5 Ω/sq, and a figure-of-merit (FoM) factor of ∼55.1. These values are well ahead of those previously reported for sandwich-film-electrodes. Additionally, the interference behaviors of light modulated by the coat and metal layers have been explored with the employment of transmittance spectra and numerical simulations. In particular, a heater device based on an AZO/Au/AZO sandwich film exhibits high performance such as short response time (∼5 s) and uniform temperature field. This work provides a deep insight into the improvement of the film quality of the sandwich electrodes and the design of high-performance transparent flexible devices by the application of a flexible substrate with an atomically smooth surface.
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/D0EE01968B
Abstract: Direct methanol fuel cells (DMFCs) are promising power sources for portable electronic devices. Atomically dispersed M–N–C cathode catalysts demonstrated a great potential in addressing the high-cost and methanol crossover issues in DMFCs.
Publisher: Springer Science and Business Media LLC
Date: 12-10-2020
Publisher: IOP Publishing
Date: 05-12-2015
Publisher: Springer Science and Business Media LLC
Date: 14-11-2017
DOI: 10.1038/S41467-017-01655-5
Abstract: Multi-layer structure of functional materials often involves the integration of different crystalline phases. The film growth orientation thus frequently exhibits a transformation, owing to multiple possibilities caused by incompatible in-plane structural symmetry. Nevertheless, the detailed mechanism of the transformation has not yet been fully explored. Here we thoroughly probe the heteroepitaxially grown hexagonal zinc oxide (ZnO) films on cubic (001)-magnesium oxide (MgO) substrates using advanced scanning transition electron microscopy, X-ray diffraction and first principles calculations, revealing two distinct interface models of (001) ZnO/(001) MgO and (100) ZnO/(001) MgO. We have found that the structure alternatives are controlled thermodynamically by the nucleation, while kinetically by the enhanced Zn adsorption and O diffusion upon the phase transformation. This work not only provides a guideline for the interface fabrication with distinct crystalline phases but also shows how polar and non-polar hexagonal ZnO films might be manipulated on the same cubic substrate.
Publisher: Springer Science and Business Media LLC
Date: 24-02-2021
Publisher: Elsevier BV
Date: 11-2020
Publisher: Elsevier BV
Date: 12-2020
Publisher: American Chemical Society (ACS)
Date: 19-12-2013
DOI: 10.1021/JP4111025
Publisher: MDPI AG
Date: 08-05-2017
DOI: 10.3390/CRYST7050130
Publisher: American Chemical Society (ACS)
Date: 02-11-2021
Publisher: American Chemical Society (ACS)
Date: 12-03-2021
Publisher: Elsevier BV
Date: 10-2017
No related grants have been discovered for Hua Zhou.