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)