Selective photobleaching of (-Ag-O-) strings on the Ag(110) surface

A p(2 x 3)-N Ag(110) surface obtained by N⁺ and/or N₂⁺ ion bombardment gave a desorption peak of N₂ at 530 K. When this p(2 x 3)-N Ag(110) surface was exposed to O₂ at room temperature, the LEED pattern showed a combined structure of [p(2x 3)-N + p(2 x 1)-O]. The STM image proved the growth of the (-Ag-O-) and (Ag₂N) strings in the [001] and [110] directions, respectively. The TPD spectrum of the combined surface gave the desorption of N₂ at 530 K, NO at 490-520 K, and O₂ at 600 K. When this [p(2 x 3)-N + p(2 x 1)-O] Ag(110) surface was illuminated with a UV light at room temperature, the (-Ag-O-) strings in the STM image were selectively erased although the (Ag₂N) underwent little influence, and the LEED pattern changed to the p(2 x 3)-N structure. The TPD spectrum of the surface after the illumination gave only N₂. These results indicate that surface migration of N atoms triggers the reaction between N and N yielding N₂ as well as N and O yielding NO on the surface. Selective photobleaching for the combined structure may suggest a feasibility of atomic scale lithography of the surface by using photochemical reactions.