Atomic-scale Chemical Lithography

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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.