We have successfully controlled the surface structures of GaAs(001) by changing incident As-molecular species. Under ${\mathrm{As}}_4$ fluxes, the $c(4\times 4)$ reconstruction with Ga-As dimers [$c(4\times 4)\alpha$ structure] is obtained, but the formation of three As-As dimer structures [$c(4\times 4)\beta$ structure] is kinetically limited. On the other hand, the structure change from the $(2\times 4)$, through $c(4\times 4)\alpha$, to $c(4\times 4)\beta$ phases is observed under ${\mathrm{As}}_2$ fluxes. We found that the $c(4\times 4)\alpha$ structure is energetically metastable and provides a kinetic pathway for the structure change between the $(2\times 4)$ and $c(4\times 4)\beta$ phases under ${\mathrm{As}}_2$ fluxes.

• Received 3 March 2004

DOI:https://doi.org/10.1103/PhysRevLett.92.236105