金硅共晶液滴表面二维材料的研究

The gold-silicon liquid eutectic alloy is a fascinating materials system with many unique properties. Eutectic alloys play an important role in nanotechnology, as nanoscale alloy droplets catalyze nanowire growth through the vapor-liquid-solid process. Recent in-situ x-ray studies at synchrotron light sources have revealed unprecedented ordering phenomena taking place at both the eutectic liquid-vacuum and liquid-solid interfaces. Other studies have confirmed these striking ordering phenomena, but all were based on spatially averaged measurements on ~mm length scales. This project has two main themes: investigation of the unique properties of the AuSi system, and fundamental investigations of the surface science of liquids and wetting phenomena. We propose to investigate phase transitions in the AuSi system in real space with scanning tunneling microscopy (STM), scanning electron microscopy, and nanometer-resolution electron spectroscopy, both Auger and reflection electron energy loss spectroscopy. These studies will be enabled by nanoscale AuSi dewetting phenomena, leading to the formation of “femto-beakers” of um size containing femtolitre of AuSi eutectic. By suppressing capillary waves, these structures will enable STM studies of crystalline 2D AuSi islands floating on AuSi eutectic. This physical system gives us an ideal laboratory for studying nanoscale wetting phenomena and ordering at the eutectic liquid-vacuum interface. The work will be carried out thorough the collaboration with the Lawrence Berkeley National Laboratory (USA). Both the research program and the project organization are designed to take advantage of the unique expertise, world-class instrumentation and interdisciplinary capabilities of the institutions.

金硅液态共晶合金是一个有着独特性能的材料体系，在纳米科技中起着非常重要的作用，例如纳米尺度的合金液滴催化纳米线通过气-液-固过程的生长。近来，在同步辐射光源上通过原位x射线研究揭示了共晶液态-真空界面和液态-固态界面上新的有序现象，但是这些工作都是基于毫米尺度的空间平均测量。伯克利实验室最近发现了纳米尺度AuSi反湿润现象，形成微米尺度的“飞升烧杯”，其中充满AuSi共晶合金，抑制了毛细波，从而使得用扫描隧道显微镜（STM）研究AuSi共晶合金表面上悬浮的晶化二维AuSi纳米岛成为可能。该物理体系给我们提供了一个理想的实验室以研究纳米尺度的侵润现象和共晶液体-真空界面上的有序现象，本项目将与美国劳伦斯伯克利国家实验室科学家合作，联合STM、扫描电子显微镜、纳米分辨的电子能谱等技术手段在实空间对其进行高分辨率的研究。

该项目原计划利用扫描隧道显微镜研究金硅共晶体表面的二维相，由于课题组定制设备到位较晚，因此将研究计划进行调整，聚焦与二维材料的制备与表征。结合云南省稀贵金属资源丰富的特点，我们研究了PtS2和PdS2二维及少层材料，作为TMDs家族的重要成员，这两种材料目前研究的比较少。这两种材料具有较宽且可调带隙、光-物质相互作用强和稳定性好等特点，是半导体器件的潜在候选者。特别是近年来伴随着电子元器件尺寸的进一步缩小和集成程度提高，半导体产业的瓶颈愈加凸显，TMDs的出现给现代电子技术领域带来了新的发展机遇。然而当今二维材料共同面对的比如材料面积不大、不易转移等问题对半导体产业的发展形成了一定的影响。我们通过将物理气相沉积和化学气相沉积结合的方法，实现了PtS2和PdS2两种材料的均匀、大面积制备，并对其物理性能进行了表征。