Extended View on the Vapor–Liquid–Solid Mechanism for Oxide Compound Nanowires: The Role of Oxygen, Solubility, and Carbothermal Reaction,The Journal of Physical Chemistry C

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Extended View on the Vapor–Liquid–Solid Mechanism for Oxide Compound Nanowires: The Role of Oxygen, Solubility, and Carbothermal Reaction
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2018-10-11 , DOI: 10.1021/acs.jpcc.8b07332
Jasmin-Clara Bürger ₁ , Sebastian Gutsch ₁ , Margit Zacharias ₁

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The Si nanowire growth can be well explained by the classical vapor–liquid–solid (VLS) process taking into account the respective Au–Si phase diagram. For oxide-based compound materials, no phase diagram with gold exists because of the insolubility of these materials into the Au catalyst material. Hence, it is not correct to claim a simple VLS mechanism for the respective growth. In this study, a more complex model for the growth of oxide nanowires (NWs) is proposed by analyzing the influence of oxygen concentration and timing of oxygen inflow into the furnace while growing SnO₂ NWs by a carbothermal chemical vapor deposition process. It is shown that a controlled amount of oxygen is mandatory to grow the SnO₂ NWs. However, either too low or too high oxygen concentration strongly suppresses the nanowire growth. On the basis of the here-presented experiments, we propose the formation of solid oxide flakes on the catalyst surface and their respective concurrence as guided by the Sn/O balance feeding the liquid catalyst surface. A new model is discussed, taking into account the effect of surface transport and the respective transport of SnO₂ solid flakes, the effect of the Sn gradient in the catalyst droplet, and a possible viscosity gradient at the droplet–solid nanowire interface.

中文翻译：

氧化物复合纳米线的汽-液-固机理的扩展视图：氧，溶解度和碳热反应的作用

考虑到各自的Au-Si相图，经典的汽-液-固（VLS）工艺可以很好地解释Si纳米线的生长。对于基于氧化物的复合材料，由于这些材料不溶于金催化剂材料，因此不存在金相图。因此，为各个增长要求简单的VLS机制是不正确的。在这项研究中，通过分析氧浓度和氧通过碳热化学气相沉积工艺生长SnO ₂ NW时进入炉内的时间，提出了一种更复杂的氧化物纳米线（NWs）生长模型。结果表明，控制量的氧气对于生长SnO ₂是必不可少的西北。然而，氧浓度太低或太高都会强烈抑制纳米线的生长。基于本文提出的实验，我们提出了在催化剂表面上形成固体氧化物薄片以及它们各自的共同作用，这是由送入液体催化剂表面的Sn / O平衡所指导的。讨论了一个新模型，其中考虑了表面传输和SnO ₂固体薄片各自传输的影响，催化剂液滴中Sn梯度的影响以及液滴与固体纳米线界面处可能的粘度梯度。

更新日期：2018-10-12

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