The atomic structures of the {111}A,B-(2 x 2) surfaces were studied by using reflection high-energy electron diffraction, scanning tunnelling microscopy and first-principles total energy calculations. Scanning tunnelling microscopic observations revealed that the (111)A-(2 x 2) surface exhibited large ordered regions having the Ga-vacancy buckled structure, while the (111)B-(2 x 2) surface consisted of small domains where As trimers were adsorbed on the outermost As layer. The atomic coordinates for both surface structures were determined via a rocking-curve analysis, using reflection high-energy electron diffraction. The obtained structural parameters were in good agreement with those deduced from first-principles calculations.

Surface Structures of GaAs{111}A,B-(2 x 2). A.Ohtake, J.Nakamura, T.Komura, T.Hanada, T.Yao, H.Kuramochi, M.Ozeki: Physical Review B, 2001, 64[4], 045318 (8pp)