Imaging Supported Metal Particles in the TEM

The diffraction pattern, where the electrons are effectively sorted into the directions in which they are traveling upon emerging from 

F re 3.2 Schematic ray diagrams illustrating the (a) BF-TEM, (h) DF-TEM, and (c) HREM image modes used in a transmission electron microscope. The inset images show example micrographs of each type of Pt particles supported on amorphous carbon. 

The three commonly encountered contrast mechanisms in TEM imaging are (i) mass-thickness contrast which occurs due to greater absorption or scattering of incident electrons from denser or thicker parts of the specimen (ii) diffraction contrast where crystalline regions of different orientation exhibit different contrast due to the orientational dependence of Bragg diffraction and (iii) phase contrast where phase-shifted waves from the undiffracted and diffracted beams are allowed to interfere and generate lattice fringes. 

AuPd/TiOj (c) phase contrast image of AuPd/activated carbon and (d) phase contrast image of AuPd/TiOj. (Courtesy of R. Tiruvalam, Lehigh University, USA). 

On crystalline supports, the most useful phase contrast information can usually be extracted from metal particles which are 

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