Transmission Electron Microscopy

JEM-2100 Transmission Electron Microscope

The JEOL JEM-2100 (Japan) is a multipurpose, analytical transmission electron microscope (TEM) which is equipped with EDAX (AMETEK, USA) EDX spectroscopy, EELS (GATAN, USA), STEM BF/DF detectors for material characterization. During analysis the electron gun of the TEM generates an electron beam that passes through the sample and interacts between the electrons and the atoms of the sample. These interactions can be used to observe features such as the crystal structure and features, the chemical composition of the sample as well as morphologic information of the sample.

Principle

The beam of electrons from the electron gun is focused into a small, thin, coherent beam by the use of the condenser lens. This beam is restricted by the condenser aperture, which excludes high angle electrons. The beam then strikes the specimen and parts of it are transmitted depending upon the thickness and electron transparency of the specimen. By selectively converging and diverging these electrons with an electron lens, the enlarged images are formed on a fluorescent surface which is positioned below the beam and specimen, which is then transferred to the CCD camera. These images can then be viewed on the computer screen and used to capture digital images. The JEM-2100 uses a lanthanum hexaboride (LaB6) electron gun with an accelerating velocity of 200 kV to provide excellent performance and observations at the atomic resolution using the UHR configuration which allows an ultrahigh TEM resolution at 0.12 nm. The scanning image of a sample at nanometer resolution can be viewed using the Scanning Transmission Electron Microscope (STEM) function integrated into the PC control system. Elemental maps of the sample can be obtained by energy dispersive X-ray spectroscopy (EDS).

Strengths

• High resolution imaging
• Offers elemental mapping with high special resolution
• Small area crystallographic information
• Strong contrast between crystalline and amorphous materials
• STEM-BF, ADF modes, Diffraction pattern analysis, Chemical analysis through EELS (electron energy loss spectroscopy) and EDX (Energy dispersive X ray spectroscopy)

Limitations

• Small sampling volumes
• Only electron transparent samples can be used
• The sample’s ability to tolerate the vacuum chamber and the high energy electron beam while being small enough to fit in the chamber is a necessity
• A particle size of < 100 nm is required to obtain clear images (< 50 nm for high resolution images)

Applications

• High resolution imaging at 0.12 nm resolution
• Image morphology of sample and to analyse the composition and some bonding differences of the samples (electron energy loss spectroscopy)
• Construct a 3-dimensional image
• Generate characteristic X-rays from samples for microanalysis.
• View frozen material (in a TEM with a cryostage).
• Identification of nm-sized defects on integrated circuits, including embedded particles and via residues
• Determination of crystallographic phases at the nanometer scale
• Nanoparticle characterization such as the size, core/shell investigations, agglomeration, effects of annealing
• Nanometer scale elemental maps
• Crystal defect characterization (dislocations, grain boundaries, voids, stacking faults)

Technical Specifications

• Signals detected: Transmitted electrons, scattered electrons and X-rays
• Elements detected (for EDX): 5B to 92U
• Maximum resolution: 0.12 nm
• Max. magnification: 1,500,000x
• Point resolution 0.23 nm
• Lattice resolution 0.14 nm