REAL-TIME STM INVESTIGATION OF THE INITIAL-STAGES OF OXYGEN INTERACTION WITH SI(100)2 X-1

Using a fast STM we have recorded constant-current topographies during oxygen adsorption on Si(100)2 X 1 at room temperature. At an oxygen pressure of 2 x 10(-8) mbar the development of the surface was followed up to an exposure of a few tens of langmuirs. Numerous atomic processes were identified. For example, bridges are formed between rows of dimers leading to an antiphase buckling in both rows over a length of 100 angstrom, complete dimers disappeared, protruding features on the scale of a 2 x 1 unit cell appeared atop and between dimers. During adsorption a clustering of the deep positions was obvious. The hitherto unknown complexity of adsorption processes is discussed in terms of the local atomic and electronic structure and of current atomic models of O/Si(100)2 x 1.