The switching of GaAs(001) termination by action of molecular iodine

This paper presents experimental results of an ultrahigh vacuum study of 4${\times}$2/c(8${\times}$2)${\longrightarrow}$2${\times}$4/c(2${\times}$8) structural transition on GaAs(001) caused by the thermal removal of the saturated iodine monolayer formed at GaAs(001)-4${\times}$2/c(8${\times}$2). It has been found out that the original c(8${\times}$2) low energy electron diffraction pattern transforms into 4${\times}$1 at 0.6 ML of iodine coverage and then keeps up to its saturation at 1.0 ML. We have determined that GaI is the only chemical product of the iodine action, its double peak was observed in the thermal desorption spectra at $T = 150{\div}370\,^{\circ}$C. The explanation of surface processes underlying 4${\times}$2/c(8${\times}$2)${\longrightarrow}$2${\times}$4/c(2${\times}$8) phase transition is presented below.