We report a dynamic formation process of Bi line structures (BLS) and their reaction dynamics with foreign atoms on Si(1 0 0) surfaces by scanning tunneling microscopy (STM). BLSs consisting of Bi dinners are formed on the Si(1 0 0) surface after bismuth deposition at 400-500 degrees C. From consecutive STM images taken after Bi deposition on the surface, we found that BLSs are easily formed when the terraces at the front of the BLS growth contains surface defects. When Ag atoms were deposited on the Si(1 0 0) surface containing the BLSs, we found that Ag atoms are preferentially adsorbed on the Si terraces rather than on BLSs. (c) 2004 Elsevier B.V. All rights reserved.