Three meetings of the Electron Microscopy Society of America (1968,
1975, and 1970)
The Electron Microscopy Society of America (now known as the Microscopy
Society of America) was founded in 1942, when it began holding annual
meetings for instrument makers and users to gather and discuss the technology
and its applications. The topics of papers given at these meetings present
a snapshot of the state of electron microscopy at the time. A brief look
at three of these meetings shows the evolution of the technology and its
applications over a 12-year period.
In the brief twelve-year span of 1968 to 1980, the physical sciences
overtook the biological sciences at EMSA meetings, judging solely on number
of papers presented. A large part of this development is probably due
to the emergence of the scanning electron microscope in 1965, which made
examination of the surface of bulk specimens possible for the first time.
Since physical scientists could now look at real samples instead of
replicas or thin films, activity in microscopy of materials increased
dramatically. With no similar dramatic development in biological microscopy,
the balance shifted.
The willingness and ability of scientists to modify these expensive,
complicated, instruments to meet their own needs is evident throughout
this 12-year span. Indeed, many of the improvements in commercial instruments
had their origins in the laboratories of the microscopists, not in the
manufacturer's labs. This type of feedback from users had to be one of
the major indicators to manufacturers as to what they should develop next.
The incorporation of a large number of these improvements in sample stages
and detectors led eventually to the commercial analytical and environmental
microscopes of today.
Most important for our discussion is the fact that materials science
as a discipline was recognized by electron microscopists after the emergence
of the SEM. While there was clearly a lag hereother histories place
the emergence of the materials science at an earlier datethis is to be
expected, because the microscopist could do very little with bulk materials
until the SEM became available. It might be said that the SEM helped
to establish and solidify materials science as a field of its own.
1968: The 26th Meeting of the Electron Microscopy Society of America
In 1968, the 26th Annual meeting of EMSA was held in New Orleans, Louisiana,
from September 16th through the 19th. 116 papers were presented dealing
with biological applications of the electron microscope. Of the 27 papers
devoted to topics that would fall under the heading of materials science
(but, notably, were not grouped or named as such), 16 discussed lattice
defects such as stacking faults or dislocations, 9 dealt with the effects
of irradiation on materials, 1 examined fatigue crack nucleation, and
1 described surface treatment of materials. These materials topics were
based almost exclusively on analysis of thin foils using the TEM. In addition,
5 papers discussed high voltage electron microscopy, 13 dealt with the
relatively new SEM, and 6 dealt with electron diffraction applications,
mainly selected area diffraction in the TEM.
A look at the titles of some of these papers is revealing:
- N.C. MacDonald of the University of California, Berkeley, presented
a paper entitled Computer-Controlled Scanning Electron Microscopy containing
the following explanation: A scanning electron microscope (SEM) has
been connected to an IBM 1800 computer system. The computer not only
processes the video information, but also generates the raster for the
SEM. So, at least as early as 1968 (if not before) computer's were
being used to control and collect information from electron microscopes.
- Field Emission Cathode Electron Gun made of Tungsten by A. N. Broers
of the Thomas J. Watson Research Center. The title reveals that the
field emission gun (FEG) that was to provide a brighter electron source
for instruments in the 1970s was already being developed.
- High Resolution SEM using Lanthanum Hexaboride Cathode Electron Gun.
Again, the LAB6 electron
source, which was to be an improvement over the original tungsten hairpin
cathode, was being developed.
- A New Hot Stage for the Philips EM 200 and Its Calibration, by J.W.
Sprys and P.C.J. Gallagher of the Ford Motor Company Scientific Laboratory.
The title demonstrates that microscopists were engaged in modifying
their commercial instruments to fit their own needs, in this case the
need to examine samples at elevated temperatures.
- A High Vacuum Electron Microscope, D. N. Braski, Oakridge National
Lab, Tennessee. Braski modified a Hitachi HU-11B electron microscope,
giving it three ion pumps and two titanium sublimation pumps, which
require no vacuum grease. Improvement in vacuum was a concern, and once
again the researcher modified his instrument to attain it.
- A combined SEM/Electron Microprobe Analyzer, V.G. Macres et al.,
Materials Analysis Company, Palo Alto, California. Materials Analysis
Company Model 400S. Designed to incorporate the most advanced features
of a high performance electron microprobe analyzer with those of a medium
resolution (1000 Ångstrom) SEM. Now that the SEM was established as
a valuable tool, manufacturers such as the Materials Analysis Company
were looking for ways to enhance its analytical power by adding existing
detectors, like the electron microprobe.
These few examples show that most of the major inventions that would
improve the electron microscope over the next 30 years brighter electron
sources, computer control, multi-detector systems, hot stages, and improved
vacuum - were already being developed in 1968. The spirit of innovation
that led researchers to modify complicated, expensive equipment for their
own needs is also evident. In many cases, these homemade innovations made
their way back to the manufacturer and eventually into commercial instruments.
1975: The 33rd Meeting of the Electron Microscopy Society of America.
Las Vegas, Nevada.
While papers on biological applications still represented the majority
of those presented at this meeting with a total of 210, the physical sciences
(mainly materials science) were catching up with a total of 141 papers.
Symposium titles included: applications of lattice imaging (5 papers);
high resolution image formation and processing (4); phase transformation
and identification (10); metals and alloys (10); ceramics, minerals, and
textiles(12); thin films (12); instrumentation (26); defects (10); image
and diffraction mechanisms (22); analytical techniques and processes (13)
; semiconductors (7); and precipitates and particulates (10). The concern
with developing new instrumentation, and with learning to understand the
mechanisms behind the images that came from these instruments, is evident
in the high number of papers devoted to those topics.
A brief survey of papers:
- Digital Image Processing in High-Resolution Electron Microscopy,
by J. Frank of the Cavendish Laboratory in Cambridge, England. An operation
that produces an output image with a higher resolution than the input
image may appear as witchcraft but is in fact feasible through clever
use of a priori information, such as the knowledge of the object and
noise statistics, Frank wrote. He noted that high-resolution images
generally contain a lot of noise from the substrate and the photographic
grain. Using mathematical techniques to separate the noise from the
signal results in higher resolution. Sometimes this requires additional
microscopy, such as taking a micrograph of the substrate by itself in
order to subtract out its noise contribution from the final substrate-plus-sample
- High Resolution Scanning MicroscopyWhat's Next? by A.V. Crewe of
the University of Chicago. Crewe maintained that there were two avenues
toward the improvement of scanning microscopy: increasing the voltage
of the instrument and correcting the spherical aberration of the electron
lens system. His group was busy on both these projects, constructing
a 1MeV scanning microscope with a theoretical resolution of less than
1 Ångstrom, and designing a spherical aberration corrector for a 100
kV instrument. Crewe also emphasized the need for improvement in the
display systems (CRTs) for scanning microscopes, stating that the currently
available 1,000 x 1,000 picture element resolution was well below the
amount of information which is available on the film in the conventional
microscope, and much improvement is needed.
- A 10,000 Lines/Field Scanning Electron Microscope System, by G.
Jones, H. Ahmed, and W. Nixon of the Engineering Department of Cambridge
University. This paper may have provided some hope to Crewe in his request
for a higher-resolution display.
- The Properties and Use of a Computer-Interfaced Video System for
High Resolution Microscopy, by W. Goldfarb and B. Siegel of Cornell
University. The authors state that A high resolution, low noise, slow
scan video system directly interfaced to a minicomputer with disk and
tape storage has been designed. This approach combined an improved
display system with computer control and data storage.
- Conversion of an EM-200 to a Dual-Gun Electron Microscope for TEM
and SEM, by A. Brewer, C. Gold, and P. Ong, details an attempt to make
a combined instrument by mounting a second electron gun for SEM purposes
below the viewing chamber.
- An alternative approach toward the same end was presented by K. Anderson,
K. Brookes, and J.M. Watson of AEI Scientific Apparatus Ltd. in An
SEM Attachment for the Corinth Electron Microscope. This attempt involved
a shared lens that acted as the final projector lens for the TEM as
well as the objective lens for the SEM.
Other papers dealt with improving SEM sample mounts, vacuum chambers,
specimen heating stages, and cryogenic specimen cooling stages.
1980: The 38th Meeting of the Electron Microscopy Society of America.
San Francisco, California.
At this meeting 178 papers were presented in the physical sciences versus
166 for the biological sciences. The appearance of the words materials
science appear in some of the titles of the papers given here; since
this was not the case at the 1975 meeting, somewhere in the five-year
span between these meetings it appears that materials science emerged
as a field of its own in the minds of microscopists. Symposium titles
- high voltage microscopy (10 papers)
- image processing (8)
- instrumentation (16)
- analytical electron microscopy (21)
- metals and alloys (12)
- high resolution imaging (11)
- micro-diffraction (4)
- ceramics and catalysts (14)
- detection systems (7)
- polymers (6)
- atmospheric pollutants (4)
- focusing of charged particles (6)
- microcharacterization of semiconductor materials (17)
- alloys and phase transformations (12)
- boundaries and interfaces (10)
- iron and steel (11)
- and thin films (9).
The 21 papers on analytical electron microscopy were given in three separate
symposia dedicated to:
- core loss electron spectroscopy; and
- low energy losses, imaging, and x-ray spectroscopy.
The attempts to produce a combined SEM/TEM instrument detailed at the
1975 meeting had clearly come to fruition with the emphasis on AEM in
1980. The 17 papers on semiconductors show the emergence of this industry
and the importance of electron microscopy in its development.
Papers of interest include:
- Applications of STEM to Problems in Materials Science, by J. Vander
Sande and A. Garret-Reed of the Massachusetts Institute of Technology.
The authors stressed the high spatial resolution chemical analysis available
using STEM, and the ability to obtain electron diffraction patterns
from small volumes of material using micro-diffraction. They were also
interested in image enhancement: The serial data collection of the
STEM permits easy interfacing to a computer for data storage and subsequent
enhancement, they wrote. This was especially useful for contrast enhancement
of polymer systems.
- Materials Science Applications of Analytical Electron Microscopy,
by W. Zaluzec. The author was able to differentiate between phases
of TiC and TiN precipitates in steels. The potential uses of AEM in
materials science is, at this time, seemingly endless, he wrote.
- Applications of Electron Energy Loss Spectroscopy in Materials Science,
by O. Krivanek of the department of Materials Science and Engineering
at the University of California, Berkeley. This paper detailed the chemical
analysis of small (400 Ångstrom) particles at a weld in an iron-nickel
- Microprobe and Nonoprobe Analysis in TEM, by M. Thompson of Philips
in Eindhoven, The Netherlands. This paper described a nanoprobe capable
of producing a beam as narrow as 4 nm in diameter for chemical analysis
of small volumes of material.
- A Temperature-Controlled High Resolution Stage, by M. Listvan, A.
Crewe, and W. Mankawich of the University of Chicago. The authors developed
a sample stage capable of maintaining temperatures in the range of +/-
100 degrees C for a 100 KeV STEM.
- Bringing the Real World Inside the High Voltage Microscope, by E.
Paul Butler of the Imperial College, London, describes dynamic, in-situ
characterization of microstructural changes during phase transformations.
This involved a controlled-temperature stage that could be adjusted
during observation to promote phase changes.
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