硼烯的分子束外延生长及扫描隧道显微镜研究

发布时间：2018-07-27 11:37

【摘要】：自2004年石墨烯被发现以来,二维材料的研究获得了突飞猛进的发展。与碳同主族的元素硅、锗、锡等的二维材料相继被制备出来。这些新型的二维材料与石墨烯一样具有蜂窝状的晶格结构,在能带中存在狄拉克锥电子结构,因此具有丰富的物理性质。但与石墨烯不同的是,这些新型二维材料都被预言具有一定大小的能隙。能隙的存在一方面使一些新奇的物理现象如量子自旋霍尔效应等得以在这些材料中实现,另一方面对扩展二维材料的应用领域也有帮助。因此,不断发现新的二维材料,丰富和补充二维材料的性质,是二维材料研究领域的重要课题。在本论文中,我们利用分子束外延技术成功地制备出了一种新型的单元素二维材料硼烯。结合扫描隧道显微镜及第一性原理计算,我们对硼烯的结构和性质进行了研究。本文的主要内容如下:1.利用分子束外延方法,在Ag(111)衬底上外延生长B制备出了硼烯。通过扫描隧道显微镜研究发现,B在Ag(111)表面主要有两种结构,S1和S2,其中S1为低温相,S2为高温相。结合第一性原理计算,我们给出了这两种结构的合理模型。通过扫描隧道谱和密度泛函理论计算表征了这两种结构的电子性质,它们都具有金属属性。利用氧化实验测验出了硼烯的抗氧化性。另外,还观察到了硼烯在Ag(111)表面的两种亚稳态结构,S3和S4。扫描隧道谱显示它们也具有金属属性。在S3中观察到了一种特殊的畴界,畴界附近有一个边界态。2.尝试了通过分子束外延在Au(111)表面生长硼烯。主要用了加温生长和室温沉积退火两种方式。加温生长时,硼在Au(111)表面难以铺展成膜,主要以团簇的形式存在,而且Au(111)有明显被B破坏的特征。室温沉积再退火时,表面能形成一些平整的膜,但这些膜结构具有与Au(111)衬底相近的晶格结构,加之衬底Au(111)也总是表现出被破坏的特征,因此难以判断这些膜是真正的硼烯还是B与Au形成的合金。3.通过分子束外延在Ag(110)表面制备出了硼烯纳米带。通过STM表征发现,B在Ag(110)表面具有四种结构。结合第一性原理计算,我们给出了这四种结构的合理模型。与Ag(111)表面的硼烯不同,这四种结构都是硼烯与Ag(110)衬底形成的超结构。我们还统计了硼烯纳米带的宽度,发现它们具有较好的均匀性。
[Abstract]:Since the discovery of graphene in 2004, the research of two-dimensional materials has been developed by leaps and bounds. The two-dimensional materials, such as silicon, germanium, tin and so on, have been prepared. These new two-dimensional materials have honeycomb lattice structure as graphene and Dirac conical electronic structure in the energy band, so they have rich physical properties. However, unlike graphene, these new two-dimensional materials have been predicted to have a certain size of energy gap. On the one hand, the existence of energy gap enables some novel physical phenomena such as quantum spin Hall effect to be realized in these materials, on the other hand, it is helpful to expand the application field of two-dimensional materials. Therefore, the discovery of new two-dimensional materials to enrich and supplement the properties of two-dimensional materials is an important subject in the field of two-dimensional materials research. In this thesis, we have successfully prepared a new kind of single element two dimensional boroene by molecular beam epitaxy (MBE). The structure and properties of boronene were studied by scanning tunneling microscope (SEM) and first principle calculation. The main contents of this paper are as follows: 1. Boroene was grown on Ag (111) substrate by molecular beam epitaxy (MBE). Scanning tunneling microscopy (SEM) results show that there are two main structures on Ag (111) surface, S _ 1 and S _ 2, among which S _ 1 is a low-temperature phase and S _ 2 is a high-temperature phase. Combining the first principle calculation, we give the reasonable models of these two structures. The electronic properties of these two structures are characterized by scanning tunneling spectrum and density functional theory. The oxidation resistance of boroene was tested by oxidation test. In addition, two metastable structures (S _ 3 and S _ 4) of boroene on Ag (111) surface were also observed. Scanning tunneling spectra show that they also have metal properties. A special domain boundary is observed in S3. There is a boundary state. 2 near the domain boundary. Boronene was grown on au (111) surface by molecular beam epitaxy (MBE). There are two main ways of temperature growth and room temperature deposition annealing. It is difficult for boron to form films on au (111) surface at elevated temperature, mainly in the form of clusters, and au (111) is obviously destroyed by B. During room temperature deposition and reannealing, some flat films can be formed on the surface, but these films have lattice structures similar to au (111) substrates, and au (111) substrates always exhibit the characteristics of destruction. Therefore, it is difficult to determine whether these films are true boron enes or alloys formed by B and au. Boron nanobelts were prepared on Ag (110) surface by molecular beam epitaxy (MBE). It was found by STM that there are four kinds of structures on Ag (110) surface. Based on the first principle calculation, we give a reasonable model of these four structures. Unlike boron on Ag (111), these four structures are superstructures formed by boron and Ag (110) substrates. We also calculated the width of boron nanobelts and found that they have good uniformity.
【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】：博士
【学位授予年份】：2017
【分类号】：O613.81

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