LNNano - Brazilian Nanotechnology National Laboratory

TEM-FEG (JEM 2100F)

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Innovative scientific technologies used in today’s nanotechnology are making remarkable progress. In research on novel materials such as carbon nanotubes, semiconductors and ceramics, as nanometer-scale evaluation and analysis are essential. This microscope is equipped with a field emission electron gun (FEG) that produces high brightness (100 times greater than LaB6)  and is highly stable. This feature is essential for nano-scale ultrahigh resolution analysis. It incorporates multiple additional techniques such as:

High Resolution images in Transmission Electron Microscopy mode (HRTEM)

HRTEM is an imaging mode that allows the imaging of the crystallographic structure of a sample at an atomic scale. Because of its high resolution, it is an invaluable tool to study nanoscale properties of crystalline material such as semiconductors, ceramics, metals, etc. The microscope resolution is 1.9 angstron. HRTEM is the tool in interfaces imaging (semiconductor, core-shell nanoparticles, grain boundaries, etc), to see structure details of nanoitubes, nanowires, nanoparticles and so on.

Scanning Transmission Electron Microscopy (STEM) image mode

The microscope can be used in scanning mode, using a probe as small as 0.2 nm (resolution is 0.14 nm).  Bright Field (BF) and Annular Dark Field (ADF) and High Angular Annular Dark Field images can be collected. One of the main advantages of this mode of operation in HAADF is that electrons scattered through high angles are not strongly influenced by diffraction, and the strength of scattering is increases with mean atomic number Z.  High-angle ADF (HAADF) STEM gives atomic number contrast images which are easy to interpret (brighter contrast = higher Z). The images are a) catalysis sample in BF image and b) in ADF image. The horizontal size image 120 nm.

Energy Dispersive X-ray Spectroscopy (EDS)

This technique used for the elemental analysis or chemical characterization of a sample. Its characterization capabilities are due in large part to the fundamental principle that each element has a unique atomic structure allowing X-rays that are characteristic of an element’s atomic structure to be identified uniquely from one another.  It provides an elemental point and line scan analyze, elemental mapping and a spectrum imaging (resolution is 1 nm). The images are a EDS mapping of Al-Fe alloy.

Energy Electron Loss Spectroscopy (EELS)

When electron beam is incident into specimen, a part of the electrons is inelastically scattered and loses a part of the energy. Elemental elemental and bonding maps across interfaces and nanostructures can be determined by analyzing the energy with the spectroscope attached under the electron microscope (Electron Energy Loss Spectroscopy). One example: diamond, graphite and fullerene are the matters which consist of only carbon (see figure). From the fine structure of the absorption peak, the difference in bonding state and local electronic state can be detected.

Image Filtered Electron Energy Loss Spectroscopy (IFEELS)

Adjusting the slit to only allow electrons which have lost a specific amount of energy can be used to obtain elementally sensitive images. As the ionization signal is often significantly smaller than the background signal, it is normally necessary to obtain more than one image at varying energies to remove the background effect. The distribution of element in specimen is clarified by selecting and imaging the electrons with a specific energy loss. Improved elemental maps can be obtained by taking a series of images, allowing quantitative analysis and improved accuracy of mapping where more than one element is involved. By taking a series of images, it is also possible to extract the EELS profile from particular features. The image shows an RGB-profile of an Al-Si interface, which is oxidized. From the elemental map it can be seen that the oxide is Alumina and not Silica. The thickness of the oxide layer is only 3 nm.

Technical Specfications (TS)

The JEM 2100 FEG-TEM, a field-emission gun transmission electron microscope, is a state-of-the-art and fully equipped ultra-high resolution analytical TEM that is capable of providing high spatial resolution atomic imaging and nanostructure analysis of material samples. This is a deticated microsfope for nanoanalyses. MORE