Apparatus for studying the structure and evolution of atomically-ordered domain boundaries, kinks and vertexes

在许多类型的电子材料中，如多晶硅或高k电介质，太阳电池效率或击穿电场等性能取决于晶体颗粒的尺寸和空间排列以及界面(微结构)的分布。材料经常进行退火热处理，通过再结晶和晶粒长大启动微观结构转变。尽管有大量关于颗粒长大和颗粒粗化的文献，但理论模型通常假定界面能是各向同性的，而不是关于界面和界面能的详细结晶学信息。为了更进一步，有必要根据界面的微观结构对界面进行分类，这可能导致对工艺、结构和材料性能之间的关系有一个定量的了解。因此，我们感到兴奋的是，我们发现了一种三维电子材料的二维模拟，它具有高度各向异性的界面(磁区边界)分布，可以在原子水平上进行详细研究。具体地说，我们开发了一种在原子平坦的硅表面上生长Ge薄膜的方法，使其包含由原子有序边界分隔的晶区。利用这个模型系统，可以研究：区域的分布、边界的分布、边界的原子结构以及边界、扭结和顶点的时间演化。为了充分利用这一系统，我们需要电子设备，使我们能够同时执行隧道和力显微镜。这将使我们能够准确地确定原子在边界区域的位置，并在许多情况下区分Si和Ge原子。这些研究将提供关于物理因素的原子水平信息，这些物理因素决定了边界的各向异性分布和结构域在特征良好的模型系统中的生长。该设备还将为每年6名高素质人员提供新的培训机会。

In many classes of electronic materials, such as polycrystalline Si or high-k dielectrics, properties such as solar cell efficiency or breakdown field depend on the size and spatial arrangement of crystalline grains and the distribution of interfaces (microstructure). Materials are frequently annealed to initiate micro-structural transformation via re-crystallization and grain growth. Although, there is a large literature on grain grown and grain coarsening, in lieu of detailed crystallographic information about interfaces and interface energies, theoretical models normally assume that interface energies are isotropic. To go beyond this, it is necessary to classify interfaces according to their microstructure and this could lead to a quantitative understanding of the relationship between processing, structure and material properties. Consequently, we are excited by the fact that we have discovered a two-dimensional analog of a three-dimensional electronic material that has a highly anisotropic distribution of interfaces (domain boundaries) that is amenable to detailed investigation at the atomic level. Specifically, we have developed a way of growing a Ge film on an atomically flat Si surface so that it contains crystalline domains separated by atomically ordered boundaries. Using this model system it is possible to study: the distribution of domains, the distribution of boundaries, the atomic structure of boundaries and the temporal evolution of boundaries, kinks and vertexes. To take full advantage of this system we require electronics that will allow us to perform tunneling and force microscopy simultaneously. This will allow us accurately determine the position of atoms in the boundary region and also discriminate between Si and Ge atoms in many cases. These studies will provide atomic-level information about the physical factors that determine the anisotropic distribution of boundaries and the growth of domains in well-characterized model system. This apparatus will also provide novel training opportunities for six highly qualified personnel/year.