Visualizing patterned thin films by grazing-incidence small-angle X-ray scattering coupled with computed tomography

Images of the spatial distribution of nanostructures in thin films were successfully reconstructed by grazing-incidence small-angle X-ray scattering (GISAXS) coupled with computed tomography (CT) measurements. As a model sample of inhomogeneous thin films, a thin film was patterned with four characters (F, B, S and L) consisting of nanoparticles of gold (Au), platinum (Pt), Au/Pt and Pt/Au, respectively, on a silicon substrate. The characters each produced respective two-dimensional GISAXS images which reflect the nanoparticle structures and their correlations in the thin film. The application of the GISAXS-CT technique to the characteristic scattering GISAXS intensity of each component enables one to reconstruct the images of each character independently. Moreover, it was found that the patterned images could be reconstructed even from very weak scattered intensities at higher q positions and the diffuse intensities. These results indicate that the GISAXS-CT method is a powerful tool to obtain distinct reconstruction images detailing the particle size, shape and surface roughness.