Ultrahigh-resolution x-ray tomography

Ultrahigh-resolution three-dimensional images of a microscopic test object were made with soft x-rays collected with a scanning transmission x-ray microscope. The test object consisted of two different patterns of gold bars on silicon nitride windows that were separated by ~ 5 micrometers. Depth resolution comparable to the transverse resolution was achieved by recording nine two-dimensional images of the object at angles between -50 and +55 degrees with respect to the beam axis. The projections were then combined tomographically to form a three-dimensional image by means of an algorithm using an algebraic reconstruction technique. A transverse resolution of ~ 1000 angstroms was observed. Artifacts in the reconstruction limited the overall depth resolution to ~ 6000 angstroms; however, some features were clearly reconstructed with a depth resolution of ~ 1000 angstroms.