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RISS 인기검색어
- 검색키워드
- 저자 : Zexiang Deng (검색결과 3 건)
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Ballistic electronic and thermal conductance of monolayer and bilayer black phosphorus
Zexiang Deng,Huanjun Chen,Zhibing Li,Weiliang Wang 한국물리학회 2017 Current Applied Physics Vol.17 No.2
We performed first principle calculations based on density functional theory and GW approximation with Landauer approach to study ballistic electronic conductance and ballistic thermal conductance of black phosphorus (BP) whose dimensions are smaller than the mean free path of carriers. Ballistic electronic conductance of monolayer BP and bilayer BP with four different stacking styles, and ballistic thermal conductance of monolayer BP were investigated. The electronic transmission value along armchair direction is found to be a little higher than that along zigzag direction near the band gap energy range. Our calculations showed that, the G point hole effective mass along zigzag direction is stackingstyle sensitive, while other G point effective mass is independent of stacking style. We also reported the anisotropic ballistic thermal conductance of monolayer BP: the anisotropic ballistic thermal conductance ratio of zigzag-to-armchair approaches a constant (about 2.0) when the temperature is beyond 200 K. The reasons for these properties were discussed.
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Zhang, Zhuo,Choi, Mingi,Baek, Minki,Deng, Zexiang,Yong, Kijung Elsevier 2016 Nano energy Vol.21 No.-
<P><B>Abstract</B></P> <P>Here, we demonstrate that the photoactivity of gold (Au)-decorated two-story hetero-nanostructures for photoelectrochemical (PEC) efficiency can be effectively enhanced by the plasmonic effect between Au and semiconductors in the visible region and by the passivation effect in the UV region. An Au-decorated two-story hetero-nanostructure was prepared as follows. The upper story is a novel hetero-nanofilm consisting of a reduced graphene oxide (RGO) nanofilm covered by a large area of crystalline CdSe nanolayer with a (111) plane outside and a thickness less than 8nm; the bottom story consists of CdSe-coated ZnO hetero-nanorods. In the visible region, the plasmonic effects between Au and other materials, such as ZnO, CdSe and RGO, were analyzed separately by reassembling the component ZnO nanorods, the CdSe layer and the RGO nanofilm. The photoconversion of the two-story hetero-nanostructure can be improved via the plasmonic effects between Au and n-type semiconductors, such as ZnO and CdSe, due to the stronger Schottky rectifier effects and hot-electron injection. In the UV light region, the photoconversion can be dramatically enhanced via the passivation of surface trap states. Moreover, the electron lifetime of the two-story hetero-nanostructure can also be improved by the suppression of electron–hole recombination by the Au nanoparticles and RGO nanofilms. Overall, CdSe-covered RGO hetero-nanofilms can increase the PEC efficiency 22.42 times over that of bare ZnO, while combination of the plasmonic and passivation effects can further improve this value by 20.7%, illustrating the potential of the two-story hetero-nanostructure in future photoelectrodes.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The upper story is a hetero-nanofilm consisting of RGO covered by CdSe nanolayer less than 8 nm. </LI> <LI> The bottom story consists of CdSe-coated ZnO hetero-nanorods. </LI> <LI> In the visible region, photoconversion can be improved via plasmonic effects and Schottky contact. </LI> <LI> In the UV region, photoconversion can be enhanced via the passivation of surface trap states. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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Zhang, Zhuo,Choi, Mingi,Baek, Minki,Deng, Zexiang,Yong, Kijung American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.4
<P>Modem nanotechnology generates more stringent requirements for the design and synthetic strategy of nanostructural materials. In this work, we demonstrate a novel strategy for the synthesis of 'corn silk'-like ZnO hierarchical nanostructures, simplified as ZnO corn silk: silk-like ZnO nanotubes (NTs) with a large length-to-diameter ratio are grown on the top tip of corn-shaped ZnO nanorods (NRs). The synthetic method is unique in that when the ZnO NRs are dipped into the aqueous solution of NaBH4, the release of Zn2+ and OH- caused by the corrosion of ZnO NRs, as well as the subsequent growth of, ZnO NTs, could allow the process to run step-by-step in self-assembly mode. This process is directed and driven by the change in concentrations of hydrogen anion H(s)(-) induced by NaBH4, as well as hydroxyl ions (OH-) induced by the H- formation and hydrolysis of dissociative Zn atoms. The prepared ZnO corn silks exhibit highly enhanced photoelectrochemical (PEC) efficiency after decoration with Au nanoparticles (NPs). ZnO silks act as pathways to facilitate efficient charge transfer, and the Au NP decoration induces the plasmonic effect, causing the hot electrons to inject into ZnO under visible illumination. At the same time, the formation of a Schottky barrier at the Au/ZnO interface can retard the electron-hole recombination. Overall, Au-decorated ZnO corn silk with an increased PEC efficiency represents a promising photoanode material, and the synthesis route developed in the current study is applicable to building hierarchical nanostructures of other materials.</P>
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