HRTEM

High-resolution transmission electron microscopy (HRTEM) is a mode of transmission electron microscopy that enables direct imaging of the arrangement of atoms in crystalline materials. In HRTEM, a beam of electrons with energies typically in the 200–300 keV range is transmitted through a thin specimen. The transmitted wave is modulated by the crystal potential and formed into an image by an objective lens. The resulting lattice fringes reveal atomic spacings and, with proper interpretation, the arrangement of individual atomic columns.

Interpretation relies on phase contrast and the contrast transfer function, rather than simple absorption. Modern HRTEM employs aberration-corrected optics to minimize lens distortions, enabling near-atomic or sub-angstrom resolution for suitable materials. Resolution depends on electron wavelength, lens aberrations, defocus, specimen thickness, and stability; images are often complemented by simulations to relate contrasts to crystal structure.

Samples must be electron-transparent, typically less than a few hundred nanometers thick, and are often crystalline or polycrystalline. Beam damage is a consideration for sensitive materials; dose, acceleration voltage, and exposure time are optimized to preserve structure. Cryo techniques are used for biological specimens to reduce radiation damage.

Applications span materials science and nanotechnology, including imaging crystal structures, defects such as dislocations and stacking faults, grain boundaries, interfaces in thin films, and characterization of nanoparticles, catalysts, and two-dimensional materials like graphene and transition metal dichalcogenides. HRTEM is frequently used with complementary methods such as electron diffraction, EELS, and EDS to provide chemical and structural information.