Atomic-scale Chemical Lithography

在这个项目中，STM（扫描隧道显微镜）被应用于观察发生在金属表面的纳米级化学反应。当Cu（100）暴露于O_2中时，在表面形成纳米尺寸的c (2*2) -O结构域，并随机排列。Cu（100）上的氧原子在室温下进行了表面迁移，但它们并没有合并成一个大的c (2*2) -O畴，而是在表面形成了一个锯齿状的相边界。吸附在Cu（100）上的N原子也形成了有限大小的c (2*2) -N畴。在N原子的情况下，N原子不会在表面上迁移，因此小c (2*2) -N畴的有序排列导致在表面上形成类似超级网格的图案。当Ni原子沉积在c (2*2) -O Cu（100）表面时，一个原子高度的Ni岛在表面随机生长，其中Cu（100）上的氧通过形成c (2*2) -O结构转移到Ni岛上，即氧作为表面活性剂对Ni岛的生长起作用。相反，沉积在c (2*2) -N Cu（100）表面上的Ni原子在c (2*2) -N的超网格状畴边界交叉处形成有限大小的点，其中N原子不作为表面活性剂，因为它们不会在表面上迁移。结果表明，我们通过超晶格的方式成功地制备了一个表面上有50个a ni点的Cu（100）表面。

In this project, STM (scanning tunneling microscopy) was applied to visualize the nano-scale chemical reactions taking place on metal surfaces. When a Cu (100) is exposed to O_2, nano-meter size c (2*2) -O domains are formed on the surface and are arranged in random. Oxygen atoms on Cu (100) undergo surface migration at room temperature but they do not coalesce into a large c (2*2) -O domain but the nano-sizu c (2*2) -O domains make a zig-zag phase boundaries over the surface. N atoms adsorbed on Cu (100) make also a limired size of c (2*2) -N domains. In the case of N atoms, N atoms do not migrate on the surface so that an ordered arrange of small c (2*2) -N domains results in making a super grid like pattern on the surface. When Ni atoms are deposited on a c (2*2) -O Cu (100) surface, one atomic height Ni islands are randomly grown on the surface, where the oxygen on Cu (100) are transferred on the Ni islands by making c (2*2) -O structure, that is, oxygen plays as a surfactant for the growth of Ni islands. In contrast, Ni atoms deposited on a c (2*2) -N Cu (100) surface make a limited size of dots at the crossing of the super-grid like domain boundaries of the c (2*2) -N,where the N atoms do not play as a surfactant because they do not migrate on the surface. As aresults, we succeeded in making a Cu (100) surface on which 50 A Ni-dots are arranged by making supper size super lattice.