The Transmission Electron Microscope (TEM) is a is a microscale, nanoscale, and atomic scale measurement and characterization tool that uses many different techniques on many different specimens. Unlike other techniques, it is capable of probing the atomic structure throughout the full thickness of the thin specimen (typically 10-50 nm) projected on the image plane, with a lateral resolution down to about 0.05 nm.
TEM generates and guides the electron beam that moves at relativistic speeds through a thin specimen. Due to this interaction with the specimen, the electrons are scattered and the signals generated by this interaction are detected. The ﬁnal image is the result of interference pattern of the incident and diﬀracted beams. TEM is widely used for local property analysis using different techniques such as diffraction contrast imaging in bright field (BF) and dark field (DF) conventional TEM, phase contrast imaging in high-resolution TEM (HRTEM), and using diffraction in selected area electron diffraction (SAED).
Another powerful technique is the aquisition of high-resolution images using high-angle annular dark-field (HAADF) and annular bright-field (ABF) detectors in scanning transmission electron microscopy (STEM) mode for detailed analysis of crystalline materials. In STEM, a converging electron beam is scanned in a small area and subsequently propagated through the sample. Due to the electron-matter interaction, the electron trajectory is scattered or diffracted. HAADF-STEM consists of high angle scattered electrons (>50 mrad) which are considered to be incoherent, which will be free of any diffraction contrast. Since the intensity of STEM images depends on the atomic number, it is possible to directly image almost all elements of the periodic table, even oxygen. STEM imaging is used to study atomic structure and chemical composition at the atomic scale.
Elemental imaging at the atomic scale using energy dispersive X-ray spectroscopy (EDS) in the scanning transmission electron microscope (STEM) is a valuable technique for characterizing the chemical composition of the sample.
The JEOL™ JEM-2010F Ultrahigh Resolution TEM/STEM is installed in a dedicated laboratory at the CNR-IOM Institute and made available for access as part of the NFFA-Trieste project. It is built by anchoring a concrete platform directly onto the karst rock with only weak links to the laboratory.
The TEM microscope has a Thermally Assisted Field Emission Gun (FEG) electron source with a ZrO/W  filament. The high-brightness source produces a highly coherent electron probe with a diameter of less than 0.13 nm and a resolution limit of 0.11 nm in phase contrast. The small size of the probe produces sub-nanometer resolution in analytical and spectroscopic measurements.
The instrument is currently equipped with an 80mm2 Oxford X-Max Silicon Drift Detector for or Energy-Dispersive x-ray Spectroscopy analysis (EDS) allowing detection of light elements (Z > 5).
The available Scanning Transmission Electron Microscopy (STEM) attachment coupled with EDS can be used to obtain chemical profiles with high spatial resolution.
In addition, the coupling between the STEM attachment and the High-Angle Annular Dark Field (HAADF) detector is used to obtain Z-contrast images.
Experimental TEM observations are supported by atomistic simulations thanks to the CNR-IOM Democritos computing cluster, in particular density functional theory (DFT) calculations to more accurately determine the structure of the specimen and evaluate the structure-property correlations.
The Quantum Espresso open-source DFT-package allows for the interpretation of data often dealing with different types of defects, formation of a new phase at the interface, and analysis of grain-boundaries mainly in transition metal-oxide heterostructures.
Precision Ion Polishing Systems (PIPS) enable high-quality TEM specimens to be obtained by gently milling at lower energies and at grazing incidence of solid-state materials.
All experiments are supported by image simulation and data analysis treatment of the results obtained both in imaging and diffraction mode.
The work is carried out in strong synergy with the growth and synchrotron-based electronic characterization NFFA-Trieste techniques: tipically, material systems are grown with PLD and MBE. Samples are first screened and investigated by SEM, then prepared in different geometries (plan-view and cross-section) by mechanical polishing and further explored at the atomic level by TEM/STEM to determine the relationships between structural, functional and electronic properties.