Anisotropic water chain growth on Cu(110) observed with scanning tunneling microscopy.

We report a novel structure of water aggregate by means of scanning tunneling microscopy. Water molecules are self-assembled into one-dimensional chains on Cu(110) at 78 K. The chain exhibits a zigzag structure with a period of 7.2 A and grows to a length of approximately 1000 A. We propose that water hexamers are arranged alternately along the chain. Interchain repulsion due to dipole interaction facilitates the 1D chain growth. A two-dimensional overlayer develops only at high coverage.