Event
MSE Seminar - Dr. Yoosuf N. Picard, Naval Research Laboratory
Friday, February 1, 2008
1:00 p.m.
Rm. 2108, Chemical and Nuclear Engineering Bldg.
Annette Mateus
301 405 5207
amateus@umd.edu
"Electron Channeling Contrast Imaging (ECCI): Dislocation Imaging and Analysis in a Commercial SEM"
Yoosuf N. Picard, Ph.D.
NRC Research Associate
Electronics Science & Technology Division
Naval Research Laboratory
Washington, DC 20375
In the realm of crystalline solids, dislocations continue to have a major impact on a wide variety of materials properties. Methods to image and analyze dislocations have historically relied on diffraction based techniques, the most comprehensive and well-established of these being transmission electron microscopy (TEM). However, a significant drawback of TEM is destructive sample preparation in order to obtain electron transparent specimens. In this talk, a non-destructive alternative for comprehensive dislocation analysis is described using a commercial scanning electron microscope. Employing electron channeling, a phenomenon discovered over forty years ago, fluctuations in backscattered/forescattered electron yield can be detected and associated with specific dislocations. This imaging technique, termed electron channeling contrast imaging (ECCI), has been implemented at the Naval Research Lab for investigating SiC substrates and GaN films/devices. Details on the interplay between surface penetrating dislocations and atomic step morphologies is described, as well as dislocation influence on ultraviolet luminescence output in GaN devices. Combined experimental and theoretical results show the potential for Burgers vector determination via ECCI.
For more information, contact Annette Mateus at (301)405-5207 or amateus@umd.edu.
