Improved Reflectivity Fitting Using SERF (Spreadsheet Environment Reflectivity Fitting)

K.A. Welp, C. Co
University of Delaware

Specular reflectivity experiments have been very successful in depth profiling of various materials. The inversion problem requires, in general, model fitting. Fitting programs for reflectivity are available at research institutions operating reflectometers, or commercially with the instruments themselves. The existing software for reflectivity fitting has proven to be very successful for layered model profiles, however, these programs can be cumbersome in their command structure. Additionally, they do not offer generic functions (e.g. parabolic profiles) to be used as model profile inputs. Here we attempt to overcome these difficulties by utilizing the advantages of a commonly available spreadsheet (Microsoft Excel(tm)) as the host environment for fitting. SERF (Spreadsheet Environment Reflectivity Fitting) is comprised of "add-in" functions capable of calculating realistic reflectivity profiles from model scattering length density profiles. The spreadsheet environment offers simultaneous display of numeric and graphical data, and automatic calculation and graph updates when a parameter is changed. These features offer efficiency improvements to the user. Additionally, and most significantly, this method allows flexibility in the profile shapes which can be inputted. The ability to input model profiles, with specific functional forms, simply may lead to better understanding of data obtained from reflectivity experiments. We will demonstrate these fitting tools, their ability to calculate reflectivity for both traditional layered profiles, as well as specific analytical function profile inputs.

(posted 10-Nov-97 jw)