The (001) surface of α-Ga single-crystal surfaces was investigated with the scanning tunneling microscope (STM) under ultra-high-vacuum conditions. The sputter-cleaned surface exhibits large, automatically flat terraces extending over distances of several 1000 Å. On the atomic scale, STM images reveal a 1×1 reconstruction of the surface lattice. The measured step height between the (001) terraces provides direct evidence for the existence of molecular ${\mathrm{Ga}}_2$ dimers, a long-standing assumption that previously lacked clear experimental confirmation.

• Received 9 June 1992

DOI:https://doi.org/10.1103/PhysRevB.46.7319