Filters

2019 - 20202

More filters

2021 - 20222
Reset filters

Settings

Author: Gao, Guanhui × Subject: transmission electron microscopy ×

Search Results

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Axial GaAs/Ga(As, Bi) nanowire heterostructures
    (Bristol : IOP Publ., 2019) Oliva, Miriam; Gao, Guanhui; Luna, Esperanza; Geelhaar, Lutz; Lewis, Ryan B
    Bi-containing III-V semiconductors constitute an exciting class of metastable compounds with wide-ranging potential optoelectronic and electronic applications. However, the growth of III-V-Bi alloys requires group-III-rich growth conditions, which pose severe challenges for planar growth. In this work, we exploit the naturally-Ga-rich environment present inside the metallic droplet of a self-catalyzed GaAs nanowire (NW) to synthesize metastable GaAs/GaAs1-xBi x axial NW heterostructures with high Bi contents. The axial GaAs1-xBi x segments are realized with molecular beam epitaxy by first enriching only the vapor-liquid-solid (VLS) Ga droplets with Bi, followed by exposing the resulting Ga-Bi droplets to As2 at temperatures ranging from 270 °C to 380 °C to precipitate GaAs1-xBi x only under the NW droplets. Microstructural and elemental characterization reveals the presence of single crystal zincblende GaAs1-xBi x axial NW segments with Bi contents up to (10 ± 2)%. This work illustrates how the unique local growth environment present during the VLS NW growth can be exploited to synthesize heterostructures with metastable compounds. © 2019 IOP Publishing Ltd.
  • Thumbnail Image
    Item
    Engineering grain boundaries at the 2D limit for the hydrogen evolution reaction
    ([London] : Nature Publishing Group UK, 2020) He, Yongmin; Tang, Pengyi; Hu, Zhili; He, Qiyuan; Zhu, Chao; Wang, Luqing; Zeng, Qingsheng; Golani, Prafful; Gao, Guanhui; Fu, Wei; Huang, Zhiqi; Gao, Caitian; Xia, Juan; Wang, Xingli; Wang, Xuewen; Zhu, Chao; Ramasse, Quentin M.; Zhang, Ao; An, Boxing; Zhang, Yongzhe; Martí-Sánchez, Sara; Morante, Joan Ramon; Wang, Liang; Tay, Beng Kang; Yakobson, Boris I.; Trampert, Achim; Zhang, Hua; Wu, Minghong; Wang, Qi Jie; Arbiol, Jordi; Liu, Zheng
    Atom-thin transition metal dichalcogenides (TMDs) have emerged as fascinating materials and key structures for electrocatalysis. So far, their edges, dopant heteroatoms and defects have been intensively explored as active sites for the hydrogen evolution reaction (HER) to split water. However, grain boundaries (GBs), a key type of defects in TMDs, have been overlooked due to their low density and large structural variations. Here, we demonstrate the synthesis of wafer-size atom-thin TMD films with an ultra-high-density of GBs, up to ~1012 cm−2. We propose a climb and drive 0D/2D interaction to explain the underlying growth mechanism. The electrocatalytic activity of the nanograin film is comprehensively examined by micro-electrochemical measurements, showing an excellent hydrogen-evolution performance (onset potential: −25 mV and Tafel slope: 54 mV dec−1), thus indicating an intrinsically high activation of the TMD GBs.