Tilting in the arsenic-induced<i>c</i>(4×4) reconstruction of the GaAs{001} surface

Abstract

The atomic geometry of the As-rich GaAs{001}-c(4\ifmmode\times\else\texttimes\fi{}4) surface prepared by molecular-beam epitaxy has been characterized in situ. The focus of the study is to determine how excess As affects the structure of the GaAs{001} surface. We report that the second- and third-interlayer spacings are (1.48\ifmmode\pm\else\textpm\fi{}0.10) and (1.47\ifmmode\pm\else\textpm\fi{}0.10) \AA{}, respectively, in comparison to the bulk spacing of 1.41 \AA{}. Arsenic atoms in the first layer are observed to be dimerized along the 〈110〉 azimuth with a bond length of (2.69\ifmmode\pm\else\textpm\fi{}0.10) \AA{}. Furthermore, evidence is presented that is consistent with a structure which contains both untilted and tilted dimers. The tilting is defined by a rotation about the center of the dimer bond by \ifmmode\pm\else\textpm\fi{}(4.3\ifmmode^\circ\else\textdegree\fi{}\ifmmode\pm\else\textpm\fi{}0.5\ifmmode^\circ\else\textdegree\fi{}). These results are based on desorbed ${\mathrm{Ga}}^{+}$ ion distributions obtained by shadow-cone-enhanced secondary-ion mass spectrometry.