Atomic Structure of thec(4×2) Surface Reconstruction of Ge(001) as Determined by X-Ray Diffraction

The $c(4\times 2)$ 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 ${19}^{\circ }\mp 1^{\circ }$) 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 $0.340\mp 0.005$ Å.