The atomic geometry of the As-rich GaAs{001}-c(4 x 4) surface prepared by molecular-beam epitaxy was characterized in situ. The focus of the study was to determine how excess As affects the structure of the GaAs{001} surface. It was reported that the second- and third-interlayer spacings were 1.48 and 1.47Å, respectively, in comparison with the bulk spacing of 1.41Å. The arsenic atoms in the first layer were observed to be dimerized along the <110> azimuth, with a bond length of 2.69Å. Furthermore, evidence was presented that was consistent with a structure which contains both untilted and tilted dimers. The tilting was defined by a rotation about the center of the dimer bond by ±4.3°. These results were based on desorbed Ga+ ion distributions obtained by shadow-cone-enhanced secondary-ion mass spectrometry.

Tilting in the Arsenic-Induced c(4 x 4) Reconstruction of the GaAs{001} Surface. C.Xu, J.S.Burnham, R.M.Braun, S.H.Goss, N.Winograd: Physical Review B, 1995, 52, 5172-8