3D-TEM characterization of nanometric objects

The increasing level of research that is nowadays performed on the nanoscale requires specific powerful tools to characterize objects on that scale. We demonstrate in this work the usefulness of three-dimensional transmission electron microscopy (3D-TEM) used in a quantitative way to image and characterize nanomaterials with complex structures and morphologies. The tomographic recording process is a powerful tool to improve the signal-to-noise ratio when imaging nano-objects that cannot strongly extinguish electrons and to clear up the ambiguity of image interpretation due to superposition effects. The resulting ability to distinguish between the "inner" and the "outer" parts of an object as well as to determine its 3D characteristics can in turn yield quantitative information and constitutes the main focus of this paper. Complex morphologies and internal structures on the nanometer scale can thus be resolved in all spatial dimensions, and numerical densities of particles or porosities can be quantified. For porous materials, it is also possible to get the connectivity of the pores, their shapes and distribution. The 3D-TEM technique associates tomographic recording to a careful repositioning of the recorded 2D images, followed by a 3D reconstruction. It allows the recovery of a spatial resolution close to (1.5 nm)(3) that can be used to perform quantitative analysis relevant to almost all types of nanometric samples encountered when 3D information down to a few nanometers is required. (c) 2007 Elsevier Masson SAS. All rights reserved.