High-resolution Transmission Electron Microscopy

High-resolution transmission electron microscopy (HRTEM) is an imaging mode of the transmission electron microscope (TEM) that allows the imaging of the crystallographic structure of a sample at an atomic scale. Because of its high resolution, it is a valuable tool to study nanoscale properties of crystalline material such as semiconductors and metals. At present, the highest resolution realised is 0.47 ångströms (0.047 nm) with double aberration-corrected JEOL R005, Cold Field Emission Gun TEM, at Tokyo Institut of Technology. At these small scales, individual atoms and crystalline defects can be imaged. Since all crystal structures are 3-dimensional, it may be necessary to combine several views of the crystal, taken from different angles, into a 3D map. This technique is called electron crystallography.

One of the difficulties with HRTEM is that image formation relies on phase-contrast. In phase-contrast imaging, contrast is not necessarily intuitively interpretable as the image is influenced by strong aberrations of the imaging lenses in the microscope. One major aberration is caused by focus and astigmatism, which often can be estimated from the Fourier transform of the HRTEM image.