Space-correlation analysis of formate ions adsorbed on TiO2(110)

The ability of the space-correlation analysis of scanning tunneling microsc ope (STM) image to deduct short-rang order is demonstrated on a dilute form ate ion (HCOO-) overlayer prepared on a TiO2(110) surface. A c(4 x 2) local older of formate ions is found at 22% of the saturation coverage, whereas the known (2 x 1) long-range order develops over the surface of the complet e saturation coverage. The c(4 x 2) order is interpreted as a structure whe re electrostatic repulsion between formate ions is minimized. The c(4 x 2) order does not develop on the surface when formate coverage is increased; p robably due to the formation of formate-hydroxyl-formate-chains on the surf ace.