Surface X-ray Diffraction

Ian Robinson

Frederick Seitz Materials Research Laboratory

and Department of Physics

University of Illinois

I will start with a general introduction to X-ray diffraction methods for surface and interface analysis, often called SXRD. X-rays are usually considered to be highly penetrating, so I will first address the origin of surface sensitivity. This will be discussed by introducing the concept of crystal truncation rods (CTR), which allow a widely variable sensitivity, crossing all the way from the deepest bulk to a single monolayers.

Surface roughness is the simplest property that is measured by SXRD methods. I will discuss the distinctions between different models of roughness that apply to different circumstances. This will be illustrated with recent results from ion-erosion of silicon surfaces [1].

Finally the CTR method is used to analyze complex rearrangements of surfaces. If large three-dimensional datasets are available, detailed 3D structures will result. Surface-induced strains can be observed directly as deviations of bond lengths from the ideal bulk value. This will be illustrated with a recent study of the structure of atomic Au wires formed on the Si(557) surface [2].

[1] S. K. Ghose and I. K. Robinson to be published

[2] "Structure of Quantum Wires in Au/Si(557)" I. K. Robinson, P. A. Bennett and F. J. Himpsel, Physical Review Letters 88 096104-1 (2002)