Hydrogen adsorption on GaAs(110) studied by temperature-programmed desorption

Abstract

GaAs(110) was cleaved in ultrahigh vacuum and exposed to atomic and to molecular hydrogen. After exposure at 250 K to molecular hydrogen neither H nor ${\mathrm{H}}_{2}$ is found desorbing up to 670 K. Upon adsorption of atomic hydrogen, use of the temperature-programmed-desorption technique reveals a second-order process for the desorption of molecular hydrogen (${E}_{d}=13.8$ kcal/mole, ${T}_{max}$ near 450 K), with no desorption of atomic hydrogen. Desorption of As${\mathrm{H}}_{3}$ (${T}_{max}=340$ K) precedes the desorption of ${\mathrm{H}}_{2}$. Further H chemisorption induces an additional amount of Ga atoms to desorb above 700 K. Preadsorption of hydrogen decreases the ${\mathrm{As}}_{2}$ evaporation rate. An energy scheme with the equilibrium and an excited adsorbate state is derived from the combination of the temperature-programmed-desorption data and the high-resolution electron-energy-loss spectroscopy data of L\"uth and Math [Phys. Rev. Lett. 46, 1652 (1981)].