Novel Approaches for Three-Dimensional Characterization of Nanomaterials at the Atomic Level
by: Thais Milagres de Oliveira, EMAT
Nanomaterials have attracted enormous attention during the last decades due to their unique properties, which are inseparably connected to their three-dimensional (3D) atomic structure and surface morphology. In order to unravel this structure-to-properties connection, a detailed structural and morphological characterization at the atomic scale in 3D is required. Nowadays, aberration-corrected (scanning) transmission electron microscopy ((S)TEM) is capable to characterize the structure and composition of such materials at the atomic scale. However, one should never forget that (S)TEM images correspond to two-dimensional (2D) projections of a 3D object and therefore the information provided is limited. Electron tomography, in combination with the use of prior information about the investigated sample during the reconstruction, is able to achieve an atomic scale characterization in 3D. Nevertheless, the use of prior knowledge can be a limitation during the investigation of materials where structural defects are present. By using a novel approach where no prior knowledge is assumed, we were able to characterize 3D atomic structure of Au nanoparticles with structural defects. It is also the aim to investigate nanomaterials which are very beam sensitive towards the electron beam, where prolonged irradiation causes modifications to their atomic structure. Therefore, the use of a different approach based on Exit Wave Reconstruction is proposed for the 3D investigation of beam sensitive materials at the atomic scale, where gold nanorods are used as a proof of concept.