The first atomic resolution scanning tunnelling microscopic images of the (100)-(2 x 4) surface were described. High-resolution images were obtained for both occupied and unoccupied states. The x 4 periodicity was attributed to missing rows, and the x 2 periodicity was attributed to the repetition of what appeared to be trimer units. It was demonstrated that the images were inconsistent with dimer-based models that had been proposed for related semiconductor surfaces such as GaAs.

C.D.MacPherson, R.A.Wolkow, C.E.J.Mitchell, A.B.McLean: Physical Review Letters, 1996, 77[4], 691-4