APS March Meeting, Baltimore, MD, 3/13 - 3/17/06

Highly-spatial-resolved Surface Structure and Composition by LEEM Image Intensity Analysis

Jiebing Sun (UNH), James B. Hannon (IBM Research Div.), Gary Kellogg (Sandia Nat. Labs), Karsten Pohl (UNH)

Controlling the local structure and composition of a surface alloy is of great importance in thin film technologies. However, measuring the alloy’s heterogeneity is very difficult, because existing experimental techniques either assume lateral homogeneity or have limited subsurface or chemical sensitivity. In this work we have analyzed the electron diffraction intensity vs. incident energy curves of the (00) beam acquired from low-energy electron microscopy (LEEM) images. In contrast to conventional LEED-IV we are able to extract structural and local composition in the surface region with a lateral resolution of 8 nm.

Two challenges in applying multiple electron scattering calculations to the analysis of LEEM data are the low and limited electron energy range (10 to 100 eV), which we address by a careful choice of the energy-dependent real and imaginary part of the optical potential. Our analysis of the LEEM IV curves for the clean Cu(001) and Pd/Cu(001) surfaces gives excellent agreement between experimental and best-fit data a nd good agreement with previous structural investigations. Our new analysis technique is capable of determining surface structure and composition with high accuracy.