Observation of true c(8x2) symmetry in scanning tunnelling microscopy images of the clean InSb(001) surface

Filled and empty state scanning tunnelling microscopy images of the sputtered and annealed InSb(001) surface are presented. The sputter-anneal preparation generates a surface with two distinct phases. The dominant phase possesses a unit cell with true c(8 x 2) symmetry, whereas the other phase is attributed to an asymmetric 1 x 3 reconstruction. The presence of a c(8 x 2) unit cell in filled state images is in contrast to previous reports, which identified only a 4 x 1 unit cell. The true c(8 x 2) symmetry further indicates, if the available structural model is used as a guide, that the current interpretation of features in filled state images is incorrect. This result may necessitate a reevaluation of the structural model for the InSb(001)-c(8 x 2) surface.