Atomic Structure of the c(4 x 2) Surface Reconstruction of Ge(001) as Determined by X-Ray Diffraction.

The $c(4\ifmmode\times\else\texttimes\fi{}2)$ reconstruction of Ge(001) has been studied by x-ray diffraction of 150 K by measuring in-plane reflections and out-of-plane intensities of fractional order rods. The structure consists of an alternate arrangement of buckled dimers (tilt angle ${19}^{\ensuremath{\circ}}\ensuremath{\mp}{1}^{\ensuremath{\circ}}$) along the [110] and [ $1\overline{1}0$] surface directions. The dimer rows are not straight along the [110] direction but show a slight zigzag with an amplitude of $0.340\ensuremath{\mp}0.005$ \AA{}.