True Vapor-Liquid-Solid Process Suppresses Unintentional Carrier Doping of Single Crystalline Metal Oxide Nanowires
True Vapor-Liquid-Solid Process Suppresses Unintentional Carrier Doping of Single Crystalline Metal Oxide Nanowires
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DOI：
10.1021/acs.nanolett.7b01362
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发表时间：
2017-08-01
期刊：
影响因子：
10.8
通讯作者：
Yanagida, Takeshi
中科院分区：
文献类型：
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作者：
Anzai, Hiroshi;Suzuki, Masaru;Yanagida, Takeshi
由通过气-液-固（VLS）工艺形成的半导体金属氧化物组成的单晶纳米线即使在没有有意的载流子掺杂的情况下也表现出导电性，尽管这些化学计量的金属氧化物理想地是绝缘体。抑制这种无意的掺杂效应不仅对于金属氧化物纳米线而且对于各种纳米结构的金属氧化物朝向其半导体应用一直是具有挑战性的问题。在这里，我们证明了一个纯VLS晶体生长，这只发生在液-固（LS）界面，基本上抑制了无意掺杂的单晶SnO 2纳米线。通过对VLS过程中晶体生长界面的严格剪裁，我们发现仅在LS界面处形成的纳米线与在LS和VS界面处形成的纳米线之间的电导率存在巨大差异（高达7个数量级）。基于空间分辨单纳米线电学测量、平面电子能量损失谱和分子动力学模拟的研究，我们发现，由于LS界面处的退火效应高于VS界面处的退火效应，仅在LS界面处生长的晶体对无意载流子掺杂有巨大的抑制作用。这些影响将是设计各种纳米结构金属氧化物半导体性能的基础。
Single crystalline nanowires composed of semiconducting metal oxides formed via a vapor-liquid-solid (VLS) process exhibit an electrical conductivity even without an intentional carrier doping, although these stoichiometric metal oxides are ideally insulators. Suppressing this unintentional doping effect has been a challenging issue not only for metal oxide nanowires but also for various nanostructured metal oxides toward their semiconductor applications. Here we demonstrate that a pure VLS crystal growth, which occurs only at liquid-solid (LS) interface, substantially suppresses an unintentional doping of single crystalline SnO2 nanowires. By strictly tailoring the crystal growth interface of VLS process, we found the gigantic difference of electrical conduction (up to 7 orders of magnitude) between nanowires formed only at LS interface and those formed at both LS and vapor-solid (VS) interfaces. On the basis of investigations with spatially resolved single nanowire electrical measurements, plane-view electron energy-loss spectroscopy, and molecular dynamics simulations, we reveal the gigantic suppression of unintentional carrier doping only for the crystal grown at LS interface due to the higher annealing effect at LS interface compared with that grown at VS interface. These implications will be a foundation to design the semiconducting properties of various nanostructured metal oxides.