Dynamic photoinduced low-temperature oxidation of GaAs(110)

Studies of ${\mathrm{O}}_2$ interaction with GaAs(110) at 20 K show dynamic conversion of multilayers of physisorbed ${\mathrm{O}}_2$ into ${\mathrm{As}}_2$ ${\mathrm{O}}_3$-like oxides due to the synchrotron radiation beam used to acquire photoemission data (hυ=90 eV, photon flux ∼2×${10}^{13}$ ${\mathrm{cm}}^{\mathrm{-}2}$ ${\sec }^{\mathrm{-}1}$). A lower coordination of As and O is observed and is the precursor to ${\mathrm{As}}_2$ ${\mathrm{O}}_3$ at the GaAs surface. ${\mathrm{As}}_2$ ${\mathrm{O}}_5$-like bonding configurations are also produced when the amount of condensed ${\mathrm{O}}_2$ is increased but this ${\mathrm{As}}_2$ ${\mathrm{O}}_5$ is metastable with respect to high-energy photon irradiation. These low-temperature results show the interplay between photoinduced surface chemistry and kinetic constraints on oxygen diffusion over very short distances.