Real-time high-temperature scanning tunnelling microscopy was used to examine the evolution of the surface atomic structure of Si(100) during homo-epitaxy by chemical vapour deposition at 625C. At the initial stage, a (2 x n) structure was gradually formed, and the growth mode was pure step flow, followed by double step flow after a single-domain surface was obtained due to faster step advance of SB than SA. As growth proceeds, areas with c(4 x 4) symmetry appeared, grew, and eventually covered the entire surface. Scanning Tunnelling Microscopy Observation of Surface Reconstruction of Si(100) during Chemical Vapor Deposition from Si2H6. D.S.Lin: Surface Science, 1998, 402-404, 831-5