Using scanning tunneling microscopy, we have observed changes of the dimer configurations at the well-defined, atomically ordered P-rich GaP(100) and InP(100) surfaces, prepared by metal organic vapor phase epitaxy. Our measurements reflect the $p$(2 × 2)/$c$(4 × 2) surface reconstructions, where the surfaces are terminated by alternating buckled phosphorus dimers stabilized by one hydrogen atom per dimer. Comparison of successive images reveals flipping of the P dimers in several locations, which requires shifting of the H termination between the P atoms in the respective dimers.

• Received 18 May 2010

DOI:https://doi.org/10.1103/PhysRevB.83.155316