Structural and spectroscopic investigation of the in-terminated InAs(100) (4 × 2)/c(8 × 2) reconstruction

We investigate the In-rich (4 × 2)/c(8 × 2) reconstruction of InAs(100) via low-energy electron diffraction (LEED) and scanning tunneling microscopy (STM). LEED shows a highly ordered surface with a mixture of (4 × 2) and c(8 × 2) phases. Atomic-resolution STM images are consistent with a previously proposed model for the (4 × 2) surface where the unit cell contains one In dimer in the first layer and two In dimers in the third layer. A defect identified at the transition between (4 × 2) and c(8 × 2) phases appears as two bright spots located in the middle of the top In-dimer rows in filled-state images. The spots are absent in empty-state images but are replaced by intensity due to empty In dangling bonds. We discuss possible origins of this defect based on either the presence of excess In or a sulfur dopant atom.