In Situ Transmission Electron Microscopy Measurements of Ge Nanowire Synthesis with Liquid Metal Nanodroplets in Water
In Situ Transmission Electron Microscopy Measurements of Ge Nanowire Synthesis with Liquid Metal Nanodroplets in Water
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DOI：
10.1021/acsnano.9b06468
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发表时间：
2020-03-24
期刊：
影响因子：
17.1
通讯作者：
Maldonado, Stephen
中科院分区：
文献类型：
--
作者：
Cheek, Quintin;Fahrenkrug, Eli;Maldonado, Stephen
Ge纳米线的生长在水内的液体透射电子显微镜（TEM）保持器已被证明在室温下。每个纳米线生长事件由入射电子束刺激，否则不支持的液体Ga或液体In纳米液滴。各种条件进行了探索，包括液态金属纳米液滴的表面条件，液态金属纳米液滴的尺寸和密度，溶解的GeO 2的形式浓度，和电子束强度。在生长事件期间记录的一系列视频的累积观察结果表明了以下几点。首先，在液体TEM室中在未接触的液体金属纳米滴处引发纳米线生长所需的条件表明，该过程受由液体金属纳米滴散射的二次电子产生的溶剂化电子控制。所获得的电流密度与在TEM外部的常规电化学液-液-固（ec-LLS）生长中所获得的电流密度相当。第二，液态金属纳米液滴的表面状态对纳米线的生长有很大的影响，并且Ge吸附原子的表面扩散对晶化速率有贡献。第三，Ge纳米线的生长速率受到Ge到晶体生长前沿的进料速率的限制，而不是在液体金属/固体Ge界面处的结晶速率。用于还原溶解的GeO 2的电化学电流的估计在名义上与用于在TEM外部通过ec-LLS生长Ge纳米线的电流一致。第四，Ge纳米线在液体TEM室中的生长远离热力学平衡发生，在成核之前具有10（4）的过饱和值。这些共同点提供了关于如何通过ec-LLS方法进一步控制和改善Ge纳米线形态和晶体质量的见解。
The growth of Ge nanowires in water inside a liquid transmission electron microscope (TEM) holder has been demonstrated at room temperature. Each nanowire growth event was stimulated by the incident electron beam on otherwise unsupported liquid Ga or liquid In nanodroplets. A variety of conditions were explored, including liquid metal nanodroplet surface condition, liquid metal nanodroplet size and density, formal concentration of dissolved GeO2, and electron beam intensity. The cumulative observations from a series of videos recorded during growth events suggested the following points. First, the conditions necessary for initiating nanowire growth at uncontacted liquid metal nanodroplets in a liquid TEM cell indicate the process was governed by solvated electrons generated from secondary electrons scattered by the liquid metal nanodroplets. The attained current densities were comparable to those achieved in conventional electrochemical liquid-liquid-solid (ec-LLS) growths outside of a TEM. Second, the surface condition of the liquid metal nanodroplets was quite influential on whether nanowire growth occurred and surface diffusion of Ge adatoms contributed to the rate of crystallization. Third, the Ge nanowire growth rates were limited by the feed rate of Ge to the crystal growth front rather than the rate of crystallization at the liquid metal/solid Ge interface. Estimates of an electrochemical current for the reduction of dissolved GeO2 were nominally in line with currents used for Ge nanowire growth by ec-LLS outside of the TEM. Fourth, the Ge nanowire growths in the liquid TEM cell occurred far from thermodynamic equilibrium, with supersaturation values of 10(4) prior to nucleation. These collective points provide insight on how to further control and improve Ge nanowire morphology and crystallographic quality by the ec-LLS method.