X-ray study of step morphology on a W(110) surface in air

Using a surface sensitive X-ray scattering technique, we demonstrate that an atomic-scale surface step structure can be investigated with a sample in air. This is made clear by the observation of distinct step peaks precisely at the positions expected from the surface step geometry using a vicinal Mo(031) surface. The technique was then adopted to probe step structures on a W(110) surface. It is found that the fine structure of a crystal truncation rod (CTR), where the vertical component of the momentum transfer varies, reveals distinct step peaks. These step features are interpreted in terms of a simple 1D model of a step structure, which shows that the surface contains steps with step heights of 1.4, 2, 4, and 7 atomic layers along the [001] direction. Results of a lineshape analysis of the in-plane and out-of-plane scans are discussed in terms of the height-height correlation lengths.