Hydrogen termination following Cu deposition on Si(001)

We describe the surface structures following submonolayer Cu deposition on Si(001) and subsequent hydrogen termination as characterized by scanning tunneling microscopy. Cu adsorption at 870 K results in a characteristic (2x8) island+vacancy structure, as previously reported. In addition, occasional structures are observed attributed to Cu in surface interstitial sites. After H termination, the dominant features of the island+vacancy structure remain, but the size and distribution of the structures are significantly altered. Based on the atomic-scale appearance of both the clean and H-terminated structures, we propose that within the (2x8) island+vacancy structure all surface atoms are Si, with all Cu subsurface, contrary to previous structural models.