IsGISAXS: a program for grazing-incidence small-angle X-ray scattering analysis of supported islands

This paper describes a Fortran program, IsGISAXS, for the simulation and analysis of grazing-incidence small-angle X-ray scattering (GISAXS) of islands supported on a substrate. As is usual in small-angle scattering of particles, the scattering cross section is expressed in terms of an island form factor and interference function. However, the emphasis is placed on the specificity of the grazing-incidence geometry, in particular in the evaluation of the island form factor in the distorted-wave Born approximation. A library of simple geometrical shapes is available. A full account of size and possible shape distributions is given in the decoupling approximation, where sizes and positions are not correlated, and in the local monodisperse approximation. Two types of island repartitions on the substrate are considered: disordered systems characterized by their particle-particle pair correlation functions, and bidimensional crystalline or paracrystalline systems of particles.