Aberration-corrected scanning transmission electron microscopy offers users the ability to perform 3-D imaging similar to confocal microscopy, a group at Oak Ridge National Laboratory in Tennessee has reported. The technique can probe sample volumes that are 500 million times smaller than those interrogated using the optical technique, and further improvements in resolution are expected with the release of fifth-order aberration correctors in 2007.
Stephen J. Pennycook, leader of Oak Ridge’s electron microscopy group, said that confocal microscopy revolutionized the biological sciences by enabling depth sections to be reconstructed into 3-D images of cells and other biological structures. Unless techniques such as near-field imaging or multiphoton excitation are employed, however, its resolution is limited to approximately 150 nm laterally and 400 nm in depth. In contrast, third-order aberration-corrected scanning transmission electron microscopy offers a lateral resolution of less than 0.1 nm and a depth resolution on the order of 6 nm.
Pennycook said that the next-generation, fifth-order correctors are expected to be available next year. The lab will acquire models from Nion and from Corrected Electron Optical Systems GmbH of Heidelberg, Germany, for use on new microscopes from Nion and from FEI Co. of Hillsboro, Ore. The systems could im-prove the lateral resolution by a factor of two and depth resolution by a factor of four.