The site-specific chemistry of carbon tetrachloride decomposition on GaAs(001) (2×4) and (4×2) surfaces was studied by scanning tunneling microscopy and multiple internal reflection infrared spectroscopy of adsorbed hydrogen. By monitoring the changes in the vibrational spectra of the As and Ga hydrides upon the coadsorption of CCl4, it was discovered that this molecule dissociatively adsorbs onto Ga dimers and second-layer Ga atoms at 473 K. Upon heating to 673 K, the chlorine desorbs from these sites as GaCl, thereby reducing the Ga coverage. Scanning tunneling micrographs reveal that GaCl desorption produces a highly disordered (2×4)surface, and transforms the (4×2) into a new (3×2) reconstruction. The (3×2) surface appears to be stabilized by carbon incorporation.
Applied Physics A: Materials Science & Processing
- Pub Date:
- PACS: 82.15.Gh;