In situ X-ray scattering studies of growth at liquid metal - liquid electrolyte interfaces

在液-液界面处的生长对于材料合成是当前感兴趣的。这些流体界面提供了一种柔软、无缺陷的基底，并允许制备各种不同的纳米材料。在这些接口的相形成过程的详细了解是阻碍了缺乏数据的原子尺度的界面结构和底层的微观生长机制。在这个项目中，我们的目标是从根本上澄清那些在液体金属（汞，镓）和电解质水溶液之间的界面使用原位X射线散射的电化学控制生长的具体情况。第一个原子尺度的数据，在我们以前的工作中获得的PbBrF在汞电极，这种生长过程中，揭示了一个复杂的行为，涉及形成良好定义的结晶前体层之间的两种液体。这些用作随后的3D晶体形成的模板，导致准外延生长。在拟议的项目中，我们将系统地调查这些现象在沉积过程中的作用，在液体金属-电解质界面，以及研究的存款形态的时间演变的功能，所采用的电位。首先，将研究离子化合物的生长，采用卤化铅作为模型系统。特别是，我们将专注于前体层的结构作为卤化物物种和液态金属基板的功能，其在引导晶体生长的作用。其次，我们将研究通过电化学液-液-固沉积在这些界面处生长半导体锗，这是一种新颖的技术上有趣的过程。这里特别重要的是澄清的界面结构，生长的初始阶段，和三维存款的随时间变化的形态。作为这些研究的一部分，我们将确定Ga -电解质界面的原子尺度结构，特别是在液体金属中的电位和温度依赖的表面分层，这本身就是一个重要的课题。此外，这些实验将有助于进一步发展X射线散射方法作为一种工具，在液-液界面的生长过程的operando研究。

Growth at liquid-liquid interfaces is of substantial current interest for material synthesis. These fluid interfaces provide a soft, defect-free substrate and allow preparation of a wide range of different nanomaterials. Detailed understanding of phase formation processes at these interfaces is hampered by the lack of data on the atomic-scale interface structure and the underlying microscopic growth mechanisms. In this project we aim at fundamentally clarifying those for the specific case of electrochemically controlled growth at the interface between liquid metals (mercury, gallium) and aqueous electrolyte solutions using in situ X-ray scattering. First atomic scale data on such growth processes, obtained in our previous work for PbBrF at Hg electrodes, revealed a complex behavior, involving the formation of well-defined ultrathin crystalline precursor layers in between the two liquids. These serve as a template for the subsequent 3D crystal formation, leading to a quasi-epitaxial growth. In the proposed project we will systematically investigate the role of these phenomena in deposition processes at liquid metal - electrolyte interfaces as well as study the temporal evolution of the deposit morphology as a function of the employed potential. First, the growth of ionic compounds will be studied, employing lead halides as a model system. In particular, we will focus on the structure of the precursor layer as a function of halide species and liquid metal substrate and its role in steering the crystal growth. Secondly, we will investigate the growth of the semiconductor germanium at these interfaces by electrochemical liquid-liquid-solid deposition, a novel, technologically interesting process. Of particular importance here is clarification of the interface structure, the initial stages of growth, and the time-dependent morphology of the 3D deposit. As a part of these studies we will determine the atomic-scale structure of the Ga - electrolyte interface, specifically the potential- and temperature-dependent surface layering in the liquid metal, which in itself is an important topic. In addition, these experiments will help in further developing X-ray scattering methods as a tool for operando studies of growth processes at liquid-liquid interfaces.