Atomic structure of InP(001)-(2x4): A dimer reconstruction

The microscopic surface structure of InP(001) is investigated by combining first-principles total-energy calculations with soft-x-ray photoelectron spectroscopy and scanning tunneling microscopy. The 4X2 cation dimer model adapted from Ga-rich GaAs(001) surfaces as well as recently proposed, rather complex 2X4 trimer reconstruction models are found to be unstable. The energetically favored 2X4 reconstructions are stabilized by dimerized In and P atoms. Unlike the well-known GaAs surface, however, mixed In-P dimers are preferred for cation-rich surfaces due to the notable size difference between the material constituents.