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It is estimated that more than half of the human population, plus a
much greater number of domestic and wild animals, suffer from parasitic
infections. The magnitude of the problem can be illustrated by
estimates of more than 100 million cases and 1 million deaths each year
from malaria alone.
Volume 10 of Microscopy and Microanalysis marks this
journal's tenth year. The stated aim of the journal remains to
provide a forum for original research papers dealing with new
microscopy and microanalysis techniques and their applications. Papers
are indexed in several databases including MEDLINE(PubMed) and Chemical
Abstracts. Also provided are book reviews and a comprehensive calendar
of microscopy events. The journal title is owned by the Microscopy
Society of America, and the publisher is Cambridge University Press.
The journal now ranks among the top microscopy journals in the world.
This achievement is directly attributable to the efforts of its many
editors, editorial board members, authors, and reviewers. Particularly
notable is the work of my two predecessors, Jean-Paul Revel and Dale
Johnson. I thank you all.
This special issue of Microscopy and Microanalysis contains
17 articles from a topical conference on microbeam characterization of
nonconductive materials. The conference was held at the Department of
Mining, Metals, and Materials Engineering of McGill University in
Montreal on August 2–3, 2002, as the pre-meeting congress prior
to the Microscopy & Microanalysis 2002 meeting in Quebec City,
Canada.
This issue is dedicated to Regents' Professor John Maxwell
Cowley, FRS, in recognition of his lifelong contributions to electron
microscopy, diffraction, and crystallography. This collection of 22
peer-reviewed articles is based on presentations made at the
international workshop entitled “Recent Developments and
Applications of Atomic Resolution Electron Microscopy and
Spectroscopy—A Silver Jubilee.” The workshop was held in
the historic Old Main building on the campus of Arizona State
University in early January 2003 and was attended by about 150 people.
It celebrated the 25th anniversary of the Center for High Resolution
Electron Microscopy, which was founded by John Cowley, and also served
as an occasion to honor him on his 80th birthday. Keynote speakers
included Sumio Iijima, discoverer of the carbon nanotube; Mikail Roco,
senior advisor on nanotechnology for the National Science Foundation;
and John Cowley himself, whose lecture addressed innovative ideas for
achieving sub-Ångstrom resolution without requiring aberration
correction.
Improvements in STEM and TEM Instrumentation for Materials Science Applications
Extended abstract of a paper presented at the Pre-Meeting Congress: Materials Research in an Aberration-Free Environment, at Microscopy and Microanalysis 2004 in Savannah, Georgia, USA, July 31 and August 1, 2004.
A recent article in these pages compares STEM images with an image
obtained with the One-Ångstrom Microscope (OÅM) at Lawrence
Berkeley National Laboratory (LBNL). Although the experimental work is
of excellent quality, Diebold et al. (2003)
offer an incorrect explanation of the image formation process in the
high-resolution transmission electron microscope. It is important that
this misinterpretation be corrected before it comes to be accepted as
factual by other scientists who are not expert in the field of
high-resolution transmission electron microscopy.
While searching the internet for “nanotechnology,” I was
not surprised to find many definitions. Two of these are as follows:
(1) nanotechnology is the development and use of devices that have a
size of only a few nanometers; and (2) nanotechnology can best be
considered as a “catch-all” description of activities at
the level of atoms and molecules that have applications in the real
world. While nanotechnology is usually focused on the building
of structures at the atomic scale, the characterization of
such structures should also be considered as nanotechnology. At the
Microscopy and Microanalysis 2002 Meeting in Quebec City, together with
Tom Kelly and Mike Thompson, I organized a symposium entitled
“Advances in Nanoscale Technology.” The response to this
symposium was impressive, with 32 contributed and 7 invited
presentations. Some of these presentations concentrated on atom probe
field ion microscopy and form the basis for the invited contributions
in this special issue of Microscopy and Microanalysis.
The symposia for Microscopy and Microanalysis (M&M) 2004 have a
strong emphasis on scientific applications, in contrast to a focus during
the past few years on particular techniques. The Biological (B) and Physical
(P) Sciences symposia feature a variety of important target scientific areas.
The Advances in Instrumentation and Techniques (A) symposia tend to be aimed
at cross-cutting methods that bring representatives of different communities
together, for example, biological and physical scientists, X-ray and electron
scatterers, “real world” microscopists in different applications
fields, or practitioners of complementary microscopy and microanalysis methods
that address a common class of problems. The program focus on scientific
applications is balanced by a strong PreMeeting Congress, “Materials
Research in an Aberration-Free Environment,” which promises to present
the cutting edge of instrumentation and techniques, with an eye toward the
future. The current state-of-the-art of a number of microscopy techniques is
also covered in Tutorials during the meeting. Other programming venues include
a variety of Sunday Short Courses, the Presidential Happenings, the IMS Sorby
Award lecture, the Technologists' Forum, and “Ask the
Experts.” Publicly accessible programming include an art exhibit
featuring the works of David Scharf and admission to the Exhibit Hall; these
may be of interest to family members of meeting registrants. Similar to last
year, symposia will be highlighted with watermarks to provide “at a
glance” identification of broad categories of programming. This year,
practical problem solving (“RealWorld”) and nanotechnology
(“Nano”) are used typically to denote microscopy and microanalysis
studies that contribute understanding to translate technology into products
that promise to drive today's and tomorrow's economies,
respectively.
The main purpose of the article by A.C. Diebold and coworkers
(2003) is to propose a robust method for
determination of gate oxide thickness. O'Keefe objects to a statement
in this paper that “Lattice images do NOT depict the projected
atom columns; instead, they are interference patterns of the directly
transmitted beam with diffracted beams.”
This work reviews recent research on the design and control of
interfaces in engineering nanomaterials. Four case studies are
presented that demonstrate the power of a multimodal approach to the
characterization of different types of interfaces. We have used a
combination of conventional, high resolution, and analytical
transmission electron microscopy, microbeam electron diffraction, and
three-dimensional atom probe to study polymer–clay
nanocomposites, turbine rotor steels used for power generation,
multicomponent aluminum alloys, and nanocrystalline magnetic
materials.
Quantitative Transmission Electron Microscopy at Jülich,
Germany
A novel imaging mode for high-resolution transmission electron
microscopy is described. It is based on the adjustment of a negative
value of the spherical aberration CS of the
objective lens of a transmission electron microscope equipped with a
multipole aberration corrector system. Negative spherical aberration
applied together with an overfocus yields high-resolution images with
bright-atom contrast. Compared to all kinds of images taken in
conventional transmission electron microscopes, where the then
unavoidable positive spherical aberration is combined with an
underfocus, the contrast is dramatically increased. This effect can
only be understood on the basis of a full nonlinear imaging theory.
Calculations show that the nonlinear contrast contributions diminish
the image contrast relative to the linear image for a
positive-CS setting whereas they reinforce the image
contrast relative to the linear image for a negative-CS
setting. The application of the new mode to the imaging of oxygen in
SrTiO3 and YBa2Cu3O7
demonstrates the benefit to materials science investigations. It allows
us to image directly, without further image processing, strongly
scattering heavy-atom columns together with weakly scattering
light-atom columns.
The physical mechanisms involved in electron irradiation of
insulating specimens are investigated by combining some simple
considerations of solid-state physics (trapping mechanisms of electrons
and secondary electron emission) with basic equations of
electrostatics. To facilitate the understanding of the involved
mechanisms only widely irradiated samples having a uniform distribution
of trapping sites are considered. This starting hypothesis allows
development of simple models for the trapped charge distributions in
ground-coated specimens as investigated in electron probe microanalysis
(EPMA) as well as for the bare specimens investigated in scanning
electron microscopy (SEM) and environmental SEM (ESEM). Governed by
self-regulation processes, the evolution of the electric parameters
during the irradiation are also considered for the first time and
practical consequences in EPMA, SEM, and ESEM are deduced. In
particular, the widespread idea that the noncharging condition of SEM
is obtained at a critical energy E2 (where δ +
η = 1 with δ and η yields obtained in noncharging
experiments) is critically discussed.
Improvements in STEM and TEM Instrumentation for Materials Science Applications
Extended abstract of a paper presented at the Pre-Meeting Congress: Materials Research in an Aberration-Free Environment, at Microscopy and Microanalysis 2004 in Savannah, Georgia, USA, July 31 and August 1, 2004.
Giardia lamblia is a flagellated protozoan of great medical
and biological importance. It is the causative agent of giardiasis, one
of the most prevalent diarrheal disease both in developed and
third-world countries. Morphological studies have shown that G.
lamblia does not present structures such as peroxisomes,
mitochondria, and a well-elaborated Golgi complex. In this review,
special emphasis is given to the contribution made by various
microscopic techniques to a better knowledge of the biology of the
protozoan. The application of video microscopy, immunofluorescence
confocal laser scanning microscopy, and several techniques associated
with transmission electron microscopy (thin section, enzyme
cytochemistry, freeze-fracture, deep-etching, fracture-flip) to the
study of the cell surface, peripheral vesicles, endoplasmic
reticulum–Golgi complex system, and of the encystation vesicles
found in trophozoites and during the process of trophozoite-cyst
transformation are discussed.
A small probe centered on an atomic column excites the bound and
unbound states of the two-dimensional projected potential of the
column. It has been argued that, even when several states are excited,
only the 1s state is sufficiently localized to contribute a
signal to the high-angle detector. This article shows that
non-1s states do make a significant contribution for certain
incident probe profiles. The contribution of the 1s state to
the thermal diffuse scattering is calculated directly.
Sub-Ångstrom probes formed by Cs-corrected lenses
excite predominantly the 1s state and contributions from other
states are not very large. For probes of lower resolution when
non-1s states are important, the integrated electron intensity
at the column provides a better estimate of image intensity.
Extended abstract of a paper presented at the Pre-Meeting Congress: Materials Research in an Aberration-Free Environment, at Microscopy and Microanalysis 2004 in Savannah, Georgia, USA, July 31 and August 1, 2004.
Quantitative Transmission Electron Microscopy at Jülich,
Germany
With the availability of resolution boosting and delocalization
minimizing techniques, for example, spherical aberration correction and
exit-plane wave function reconstruction, high-resolution transmission
electron microscopy is drawing to a breakthrough with respect to the
atomic-scale imaging of common semiconductor materials. In the present
study, we apply a combination of these two state-of-the-art techniques
to investigate lattice defects in GaAs-based heterostructures at atomic
resolution. Focusing on the direct imaging of stacking faults as well
as the core structure of edge and partial dislocations, the practical
capabilities of both techniques are illustrated. For the first time, we
apply the technique of bright-atom contrast imaging at negative
spherical aberration together with an appropriate overfocus setting for
the investigation of lattice defects in a semiconductor material. For
these purposes, the elastic displacements associated with lattice
defects in GaAs viewed along the [110] zone axis
are measured from experimental images using reciprocal space strain map
algorithms. Moreover, we demonstrate the benefits of the retrieval of the
exit-plane wave function not only for the elimination of residual
imaging artefacts but also for the proper on-line alignment of
specimens during operation of the electron microscope—a basic
prerequisite to obtain a fair agreement between simulated images and
experimental micrographs.