原子级层状材料的浸润性

发布时间：2018-05-25 13:43

  本文选题：浸润性 + 接触角　； 参考：《中国科学院大学(中国科学院物理研究所)》2017年硕士论文

【摘要】：二维(2D)范德华(vdW)层状材料与环境之间的相互作用已经受到了巨大的研究关注。研究该类层状材料浸润性所面临的一个关键挑战是如何在原子层面上获得良好定义并且完全清洁的表面,这是在宏观实验中难以实现的。基于先前的实验报道,范德华层状材料,诸如石墨烯、h-BN和MoS2的浸润性质都是存在着较大的争论。虽然已经发现范德华层状材料的浸润性能在很大程度上取决于其厚度、缺陷、衬底的作用、来自大气环境的污染和转移方法等。但是,关于范德华层状材料浸润性的清晰的物理图像仍然是缺乏的。另一方面,如何定量地表征范德华层状材料的表面形貌也是非常重要的。常规的方式是利用原子力显微镜的扫描来获得其表面的均方根粗糙度,这在实际的工业领域中是非常缓慢、不准确和不切实际的。但是,如果我们可以清楚地理解该类材料表面的浸润性原理,那么我们便可以使用浸润性作为指标,简单快速地表征vdW层状材料的表面形貌。在本论文中,我们利用分子束外延(MBE)合成具有清洁和明确定义表面的Bi_2Se_3薄膜,作为研究vdW层状材料浸润原理的具体实例。我们发现水浸润性与Bi_2Se_3薄膜相对表面粗糙度之间存在着线性关系,这也意味着这种广义的Wenzel模型能够适用于广泛的vdW层状材料。这种广义的Wenzel模型也第一次提供了vdW层状材料浸润性清晰和准确的物理图像。此外,根据上述线性关系外推获得的水接触角(CA约为98.4°)显示理想的Bi_2Se_3表面具有意想不到的高疏水性,但粗糙的Bi_2Se_3表面上梯田小岛的边缘却具有非常强的亲水性。根据第一性原理计算的结果,我们发现这种不寻常的疏水/亲水转变与其特定的原子和电子结构有直接联系。高质量Bi_2Se_3薄膜表面的疏水性质使得其很有可能成为无需封、低成本、自清洁的纳米电子学和自旋电子学器件。
[Abstract]:The interaction between layered materials and environment has attracted much attention. One of the key challenges in studying the wettability of this kind of layered materials is how to obtain a well-defined and completely clean surface at the atomic level, which is difficult to achieve in macroscopic experiments. Based on previous experimental reports, the wetting properties of Van der Waals layered materials, such as graphene h-BN and MoS2, are controversial. Although it has been found that the wettability of Van der Waals layered material depends to a great extent on its thickness, defects, the effect of substrate, pollution from atmospheric environment and transfer methods, etc. However, clear physical images of the wettability of Van der Waals laminated materials are still lacking. On the other hand, how to quantitatively characterize the surface morphology of Van der Waals layered materials is also very important. The conventional method is to obtain the root-mean-square roughness of the surface by scanning the atomic force microscope, which is very slow, inaccurate and impractical in the practical industrial field. However, if we can clearly understand the principle of surface wettability of this kind of materials, we can use wettability as an indicator to characterize the surface morphology of vdW layered materials simply and quickly. In this thesis, Bi_2Se_3 thin films with clean and clearly defined surfaces have been synthesized by molecular beam epitaxy (MBE) as an example to study the wetting principle of vdW layered materials. It is found that there is a linear relationship between the water wettability and the relative surface roughness of Bi_2Se_3 films, which means that the generalized Wenzel model can be applied to a wide range of vdW layered materials. This generalized Wenzel model also provides clear and accurate physical images of the wettability of vdW layered materials for the first time. In addition, the water contact angle (CA) obtained from the extrapolation of the above linear relation shows that the ideal Bi_2Se_3 surface has unexpected high hydrophobicity, but the edge of the terraced island on the rough Bi_2Se_3 surface is very hydrophilic. Based on the results of first-principles calculations, we find that this unusual hydrophobic / hydrophilic transition is directly related to its specific atomic and electronic structures. The hydrophobic properties of high quality Bi_2Se_3 films make it possible for them to become self-cleaning nano-electronics and spin electronics devices without sealing and low cost.
【学位授予单位】：中国科学院大学(中国科学院物理研究所)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB34
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本文编号：1933326