【作者】 李媛；

【导师】 朱永哲；

【作者基本信息】 延边大学 ， 光学， 2011， 硕士

【摘要】 利用超高真空扫描隧道显微镜(UHV-STM)研究在Si表面上生长原子级的纳米结构和研究制作纳米器件一直以来都是热点.Si(5512)表面具有一维对称结构和垂直于一维线的相对较长周期(5.35nm).但是根据si(5512)样品准备的条件不同,样品表面有各种起伏使得局域面方向会偏离平均方向.在大面积Si(5512)表面上,不仅有平整的(5512)表面存在,也有台阶的存在,即(113)和(6917)面.在Si(5512)表面上异质外延生长以后,有时会出现小面化现象.而传统的方法不能确定局域面的方向,因此利用扫描隧道显微镜(STM)测量技术和几何学方法来定量的计算局域面和小琢面方向以及研究其产生的物理机制是很有必要的.因此,研究定量的测量局域面方向和小琢面方向对制作纳米器件来说是必要的.(1)利用STM测量技术能准确的测量出STM形貌图像上X方向上的倾斜角αx和Y方向上的倾斜角αy,并且能在形貌图像中判断出原子线的方向[110].根据晶体几何学原理算出局域面的方向偏离[5512]的极角α：tanα=(?)以及相对于[110]的方位角β：tanβ=tanαx/tanαy.(2)利用超高真空扫描隧道显微镜(UHV-STM)观察到In吸附在Si(5512)表面上的情况.当基底温度保持在400℃和450℃,In元素的蒸度量为0.02A时,在In/si(5512)表面上观察到台阶上的(6917)小琢面发生了小面化现象,但是(5512)平台和与(6917)小琢面相连接的(113)面没有发生小面化现象.通过利用我们熟知的Si(5512),Si(113)和si(111)面的晶体结构参数,运用几何学方法得到了(6917)小琢面吸附In之后转变成为(124)面和(111)面的组合.由于电致迁移影响,根据加热电流方向,在微观的尺寸下能形成各种高低起伏的结构,而在原子尺寸下是不明显的.因此使表面的局域面方向偏离平均面方向.高指数的Si表面很容易出现各种小琢面.由于In吸附在Si(5512)表面上,基底温度保持在400℃和450℃,In元素的蒸度量为0.02A时,在γ-plot里(6917)小琢面的尖端的最低点消失,而(124)小琢面则出现了尖端.因此(6917)小琢面的表面自由能状态发生改变而转变成(124)和(111)小琢面的组合,而(5512)和(113)平台并没有发生改变.由于低能电子衍射(LEED)和X射线(X-ray)等传统的方法无法测量局域面和小琢面的方向,因此定量的方法精确的测量出局域面和小琢面方向是很用必要的.更多还原

【Abstract】 It is attracted many attentions for the studies of the fabrication of the atomic scale nanostructures on the Si surfaces by ultra high vacuum scanning tunneling microscopy (UHV-STM) system. Si (5512) surface has one-dimensional (1-D) sym-metry and relative longer period (5.35 nm) perpendicular to the 1-D wire. Various hill and valley structures can be observed on the macroscopic surface of Si (5 5 12) sample surface due to the different preparation conditions which make the local ori-entations differ from the average one on the microscopic surface. Not only (5 5 12) terrace but also (113) and (6917) facets exist on the Si (5512) surface. Faceting usually occurs on the Si (5512) surface when heteroepitaxy. Therefore, it is nec-essary to study precise measurement of the local orientation and the facet direction for the study of the fabrication of nanodevice using Si (5 5 12) as a template.(1) In the topography STM image, along X-and Y-axis, the local inclined angles,αx andαy, can be measured accurately through line profile processing, and the [110] direction can be determined before taking STM images according to the sample cutting, mounting on the sample hold, and the STM tip scanning direction. Using metrological method, the polar angle, a, relative to the [5 5 12] direction and the azimuth angle,Φ, relative to [110] direction can be measured precisely through the relationships:tanα=(?), and tanβ= tanαx/ tanαy.(2) When the substrate temperature is kept at 400℃and 450℃,0.02Aof In is deposited on the Si (5512) surface, the (6917) facet is faceted, but the (5512) terrace and (113) facet next to the (6917) facet no faceting occurred. Aceording to the well known parameters of crystal structural of (5512), (113) and (111), using metrological method, it is revealed that (6917) facet is converted to (124) and (111) facets.Due to the electron migration effect, in several ten micro size images, several kinds of hill-and-valley structures can be formed on the surface according to the heating current direction, even though it is not appear obviously in the atomic scale images. Therefore, local orientations usually are misorientated slightly from the average direction. On the other hand, when 0.02Aof In is deposited on the Si (5 512) surface at 400-450℃, faceted steps, composed of (124) facet and (111) facet, turned out to be energetically favorable rather than (6917) facet due to cusped minimum of the surface free energies of (124) and (111) inγ-plot are lower than (6917) facet significantly. However, due to the limit in LEED and x-ray crystallographie orientation of high-index surfaces without distinct diffraction spots, the local orientation and the facet direction cannot be measured using these tradition techniques. Therefore, metrological method turned out to be a useful technique for precise measurement of the local area orientation and the facet direction.更多还原