New reconstruction-stoichiometry correlation for GaAs(001) surface treated by atomic hydrogen

The structure, stoichiometry and electronic properties of the GaAs(001)-(2 x 4)/c(2 x 8) surface treated by cycles of atomic hydrogen (AH) exposure and subsequent annealing in UHV were studied with the aim of preparing the Ga-rich surface at low temperatures. Low energy electron diffraction showed reproducible structural transformations in each cycle: AH adsorption at the (2 x 4)/c(2 x 8) surface led to the (1 x 4) structure at low AH exposure and to a (1 x 1) surface at higher AH exposure with subsequent restoration of the (2 x 4)/c(2 x 8) structure under annealing at 450 degrees C. The cycles of AH treatment preserved the atomic flatness of the GaAs(100) surface, keeping the mean roughness on to about 0.15 nm. The AH treatment cycles led to the oscillatory behavior of 3dAs/3dGa ratio with a gradual decrease to the value characteristic for the Ga-rich surface. Similar oscillatory variations were observed in the work function. The results are consistent with the loss of As from the surface as a result of the desorption of volatile compounds which are formed after reaction with H. The prepared Ga-rich GaAs(001) surface showed the stability of the (2 x 4)/c(2 x 8) structure up to the annealing temperature of 580 degrees C. (C) 2008 Elsevier B. V. All rights reserved.