Microscopy101
Early Use of Reflection Electron
Diffraction in the TEM
Donald L. Gibbon
MATCO Services, 4640 Campbells Run Rd., Pittsburgh, PA 15205
donald.gibbon@
matcoinc.com
My TEM experience started nearly fifty years ago. Microscopy (1953) was my only crutch. It took me three
I began in 1961 as a total novice when, as a fledgling years of spare-time fiddling, but I finally got fairly adept
graduate student in geology at Rice University, I inherited at using this rather crude instrument. As an illustration of
responsibility for a Shimadzu transmission electron that crudeness, filaments were handmade from a 1000-foot
microscope, perhaps the only Shimadzu TEM to come coil of fine tungsten wire. A length of wire was bent into
into this country. A previous student showed me the on-off a V-shape by pressing it down over a single-edged razor
switch and a few other basics and then dropped it and its blade. You can imagine that centering the beam from this
filament was a tedious job. But, amazingly, it worked.
Impinging
Eventually, I graduated to a more advanced instrument,
electron a Hitachi HU 11A, at Pennsylvania State’s Mineral
beam
Constitution Lab. Sample preparation was via carbon
replicas or powder dispersions. Replicas were made in
a vacuum evaporator by vapor-casting a few hundred
Forward-and-back
Angstroms of carbon onto the sample surface, then
translation and
Sample
shadowing the surface with platinum from a point source.
rotation axes
Lateral
Platinum-shadowed carbon replicas looked remarkably
translation
“life-like” in the TEM (for that time), and they could be
and rotation
faithful in resolution to about 25,000x.
axes Frequently some of the components of the sample
would remain with the replica. For example, grain
boundary precipitates could remain in place on replicas
of metal samples. But if they didn’t, it was also possible to
Screen and
make intentional “extraction replicas.” It was these surface
diffraction constituents that often provided suitable specimen material
pattern
for electron diffraction, powder, or single crystal. These
Figure 1: General diagram of reflection electron diffraction set-up.
techniques allowed identification of very thin layers or
small amounts of deposits without energy-dispersive x-ray
pseudo-English instruction manual into my lap to figure out spectroscopy, which had not yet been developed. Powder
on my own. From that inauspicious beginning, microscopy patterns were much the simplest, of course, being sets of
became my life’s work. Cecil Hall’s Introduction to Electron concentric circles, the diameters of which were inversely
A B
Figures 2: Reflection electron diffraction patterns from Cu
2
O (A) and CuO (B), cubic and triclinic crystalline corrosion products on copper coupons.
56 doi: 10.1017/S155192950900039X
www.microscopy-today.com • 2009 September
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76