TRANSMISSION ELECTRON MICROSCOPY (TEM)

Ramon Youhanna

Course Coordinator: Peter Majewski

Transmission electron microscopy (TEM) utilizes energetic electrons to provide morphologic, compositional and crystallographic information on samples.

What is TEM?

TEMs are capable of imaging at a significantly higher resolution than microscopes at a maximum potential magnification of 1 nanometre; It enables the user to examine fine detail, as small as an atom, which is tens of thousands times smaller than the smallest resolvable object under a light microscope.

Function of TEM

TEM is a microscopy technique in which a beam of electrons is transmitted through an ultra thin specimen, interacting with the specimen as it passes through. An image is then formed, magnified and focused onto an imaging device, such as a fluorescent screen. It is used to characterize the microstructure of materials with very high spatial resolution and is a commonly used technique for metallurgical analysis.

Work Principle of TEM

Cross-Section of TEM microscope

Consists of three essential systems:(1)An electron gun: Which produces

the electron beam, and the condenser system, which focuses the beam onto the object,

(2) Image-producing system: Which focus the electrons passing through the specimen to form a real, highly magnified image, and

(3) Image-recording system: Which converts the electron image into some form perceptible to the human eye (Computerized images stored as TIFF or JPEG file.)

Transmission Electron Microscope

Morphology of the starting zirconia powders as observed by transmission electron microscopy

TEM Images

Superparamagnetic iron oxide (SPIO) image observed by transmission electron microscopy

TEMs can be used in semiconductor analysis and production, and the manufacturing of computer and silicon chips.

Examples of TEM

Types of TEMSTEM: Scanning Transmission Electron Microscopy scans with an extremely narrow beam that is transmitted through the sample.

CTEM: Cryo Transmission Electron Microscopy used for imaging liquid crystal suspensions, protein molecules, hydrogels, viruses, nanoparticles etc.

Influenza Virus

An organic thin film mapping Pathways of Electrical Charge 

TEM versus Scanning TEM

TEM STEM

TEM uses a wide beam of electrons passing through a thin sliced specimen to form an image.

produces dark spots of stained areas all at one time.

STEM uses a focused beam of electrons scanning through a thin sliced specimen to form an image.

produces images as one spot at a time.

1. Siemens (introduced first TEM microscope)

2. Carl Zeiss (Libra 120 Plus Transmission Electron Microscopes)

3. Hitachi (HD-2300A Scanning Transmission Electron Microscope)

4. CSIRO (FEI Tecnai 12 Transmission Electron Microscope)

5. Jeol (JEOL 2010F Scanning Transmission Electron Microscope)

6. Philips

List of Manufacturers

1. Images are black and white2. Generally requires more time and

experience for sample preparation3. Potential artefacts from sample

preparation4. Need to use dead and fixed samples5. Sensitive to vibration and

electromagnetic fields6. Requires constant upkeep including

maintaining voltage, currents to the electromagnetic coils and cooling water.

Limitations of TEM

Areas of Interest applying TEM:1) Life Sciences, e.g. visualizing tiny nerves’

demages2) Biological & Medical, e.g. Viral detection or

visualizing in cells 3) Nanotechnology, e.g. production of micro-chips4) Material research & forensic analysis5) Gemology, e.g. to analyze structure and texture

of gems.6) Industry and metallurgy, e.g. to identify flaws,

fractures and damages to micro-sized objects7) Education, e.g. for research & observe nano-

sized objects

Application of TEM

References

http://www.microscopemaster.com/transmission-electron-microscope.html http://www.personal.usyd.edu.au/~cox/pdfs/butterfly.pdf

http://www.uiowa.edu/~cmrf/methodology/tem/tem_pg2.html

http://www.sci.sdsu.edu/emfacility/555class/class1.html

http://www.biolcell.org/boc/100/0491/1000491.pdf

http://tpm.amc.anl.gov/Lectures/Zaluzec-1-Instrumentation.ppt.pdf