October 2007 Process Spotlight: Energy-Dispersive X-Ray Spectroscopy (EDS or EDX)

October 2007
Process Spotlight: Energy-Dispersive X-Ray Spectroscopy (EDS or EDX)
Energy dispersive x-ray spectroscopy is a technique used to measure elemental composition of a sample.
It requires a beam source, x-ray detector, pulse processor, and analyzer to interpret data and determine
EDX systems are most commonly found as an add-on attachment for a scanning electron microscope
(SEM). The SEM focuses a beam of electrons onto a sample surface, dislodging inner ring electrons on
individual atoms of the material (these ejected electrons are collected by the SEM to form the microscope
image). This inner ring electron vacancy if filled by an outer ring electron, and the difference in energy
levels between the two states leads to emission of an x-ray. The energy of this x-ray is particular to each
element (each element has its own spectrum), and the spectrum of x-ray energies generated by
bombardment can be analyzed to determine which elements are present in the sample (the pulse
processor, which “counts” x-ray events, and the spectrum analyzer are the heart of the EDX system).
Because of the beam energies involved in SEMs, EDX is not a true surface analysis technique. The beam
will penetrate into the sample to some degree—the minimum interaction volume is typically one cubic
micron or so. This means that if one is probing thin films (as in an LCD), it is highly likely that the bulk
of the signal will come from the base substrate material. Due to this, EDX is best suited for analyzing
composition of particle contamination, or thick films. It is still possible to look at thin films, provided the
signature of the elements in question can be seen over the “background” spectrum of the substrate (yes, it
is possible to see indium and tin in a spectrum from standard ITO coated glass). Glass is a complex
material that usually includes half a dozen or more different elements.
EDX systems can also be set up to do elemental mapping, utilizing the scanning capabilities of the SEM
to generate false color maps of individual elements. Most EDX systems can detect elements as light as
carbon or boron, but do best with heavier elements (although SEM beam accelerating voltages must be
high enough to cause materials to emit the relevant band of x-ray energies). Since lighter elements have
fewer electrons and thus smaller differences in energy between orbitals, generated x-rays are lower in
energy and harder to detect.
One important distinction regarding EDX is that it identifies elements present in a sample, but does not
identify how the elements are related by bonding—thus it can identify magnesium or fluorine, but does
not indicate whether these materials are present as MgF2, or separate compounds. Related techniques
such as x-ray photoelectron spectroscopy (XPS) are better suited to determine which compounds are
present on the surface.
The LCDRF has a Quartz X-One EDX system attached to its Hitachi S-2600N variable pressure SEM.
The spectrum analysis software makes it straightforward to identify elements in a sample, and indicates
quality of fit.
Some resources to learn more about EDX:
Energy Dispersive X-ray Analysis in the Electron Microscope (Microscopy Handbooks)
by DC Bell, 2003, Garland Science
http://microanalyst.mikroanalytik.de/index_e.phtml (website related to EDX)
http://www.edax.com/ (equipment manufacturer)
http://www.qrtz.com/xray.html (equipment manufacturer)
http://www.ou.edu/research/electron/element.html (further description)
Staffing Update
There are three new faces in the cleanroom this fall:
Nick Diorio is a first year graduate student in the Chemical Physics program who is doing a rotation in
the cleanroom for fall semester. As part of this rotation, Nick will be setting up the JA Woollam
spectroscopic ellipsometer in a more user-friendly fashion. He will use the VASEManager software to set
up some of the more routine measurements, such as film thickness and index for polyimides and barrier
coats. Nick will also be the test subject for our cleanroom training certificate program that we are
Kevin Ballard is a junior in the School of Technology, and is assisting with equipment issues and
substrate preparation. He has previous cleanroom experience from Swagelok. Kevin has already returned
our polyimide oven to proper operation, and will be helping to set up our blasting cabinet, which will be
used to clean shielding from our GenVac and MRC vacuum deposition machines.
Matthew Wayman is a sophomore Biology and English major, and will be assisting with cleaning and
inventory, as well as substrate preparation.
Equipment Update
Several tools in the LCDRF will be undergoing maintenance and upgrades, or have recently completed
Dr. Qihuo Wei’s Oxford 80+ reactive ion etcher (RIE) system, is being installed (finally!) the week of
October 8 by Oxford personnel. The system is set up for SF6 and CHF3 gases. More information on this
system and its capabilities will be included in next month’s newsletter.
The GenVac SC1 Coater will undergo repair and upgrade later this month. New shielding is being
designed to make system cleaning easier (in combination with the new blasting cabinet), and the ion gun
will be repaired. This should restore ITO deposition capabilities in the near future. Deposition of
aluminum, chrome, gold, and SiO2 are currently available.
The Technics PlanarEtch II plasma etcher is currently down. No work is planned on this machine in the
next month. If you have interest in using this machine, please contact Doug Bryant; if there is a need for
it, we can bump this up in priority.
Gas Chromatography
Our GCMS is now fully operational and we have a detailed process that we use if you have any needs for
this type of equipment. What follows is a description of GCMS, and a link to our process for using it.
Gas chromatography-mass spectrometry (GC/MS) is a method that combines the features of gas-liquid
chromatography and mass spectrometry to identify different substances within a test sample. Applications
of GC/MS include drug detection, fire investigation, environmental analysis, explosives investigation, and
identification of unknown samples. GC/MS can also be used in airport security to detect substances in
luggage or on human beings. Additionally, it can identify trace elements in materials that were previously
thought to have disintegrated beyond identification.
The GC-MS is composed of two major building blocks: the gas chromatograph and the mass
spectrometer. The gas chromatograph utilizes a capillary column and depending on the column's
dimensions (length, diameter, film thickness) as well as the phase properties (e.g. (5%
(phenyl)polysiloxane) the difference in the chemical properties between different molecules in a mixture
will separate the molecules as the sample travels the length of the column. The molecules take different
amounts of time (called the retention time) to come out of (elute from) the gas chromatograph, and this
allows the mass spectrometer downstream to capture, ionize, and detect the molecules separately. The
mass spectrometer does this by breaking each molecule into ionized fragments and detecting these
fragments using their mass to charge ratio.
These two components, used together, allow a much finer degree of substance identification than either
unit used separately. It is not possible to make an accurate identification of a particular molecule by gas
chromatography or mass spectrometry alone. The mass spectrometry process normally requires a very
pure sample while gas chromatography using a traditional detector (e.g. Flame Ionization Detector) detect
multiple molculears that happen to take the same amount of time to travel through the column (i.e. have
the same retention time) which results in two or more molecules to co-elute. Sometimes two different
molecules can also have a similar pattern of ionized fragments in a mass spectrometer (mass spectrum).
Combining the two processes makes it extremely unlikely that two different molecules will behave in the
same way in both a gas chromatograph and a mass spectrometer. Therefore when an identifying mass
spectrum appears at a characteristic retention time in a GC-MS analysis, it typically lends to increased
certainty that the analyte of interest is in the sample.
Samples are introduced to the column via an inlet, typically by injection through a septum. The inlet is a
heated chamber that volatilises (vapourises) the sample. In a split system a steady flow of carrier gas
moves through the inlet (known as total flow measured in ml/min). A portion of the total flow carries the
sample into the column (column flow). Another portion of the total flow is directed across the septum to
purge the inlet of any sample after injection (septum purge). Another portion of the total flow is directed
through the split vent (split flow) in a set ratio known as the split ratio. In a splitless system the split vent
is closed. The advantage of a splitless system is a greater amount of sample is introduced to the column.
A split system is prefered where the detector is sensitive to trace amounts of analyte and overloading of
the column may be of concern. The gas flows are regulated by an Electronic Pneumatics Controller (EPC)
by feedback mechanisms.
1. Gohlke, R. S., Time-of-flight mass spectrometry and gas-liquid partition chromatography. Anal.
Chem. 1959, 31, 535-41
2. Gohlke, R. S.; McLafferty, F. W., Early gas chromatography/mass spectrometry. J. Am. Soc. Mass
Spectrom. 1993, 4, (5), 367-371.
3. "Optimizing the Analysis of Volatile Organic Compounds - Technical Guide" Restek Corporation, Lit.
Cat. 59887A
4. The Development of the Viking GCMS
5. V. A. Krasnopolsky, V. A. Parshev (1981). "Chemical composition of the atmosphere of Venus".
Nature 292: 610 - 613. DOI:10.1038/292610a0.
6. H. B. Niemann, S. K. Atreya, S. J. Bauer, G. R. Carignan, J. E. Demick, R. L. Frost, D. Gautier, J. A.
Haberman, D. N. Harpold, D. M. Hunten, G. Israel, J. I. Lunine, W. T. Kasprzak, T. C. Owen, M.
Paulkovich, F. Raulin, E. Raaen, S. H. Way (2005). "The abundances of constituents of Titan’s
atmosphere from the GCMS instrument on the Huygens probe". Nature 438: 77-9-784.
7. Goesmann F, Rosenbauer H, Roll R, Bohnhardt H (2005). "COSAC onboard Rosetta: A bioastronomy
experiment for the short-period comet 67P/Churyumov-Gerasimenko". Astrobiology 5 (5): 622-631.
• Robert P., Dr Adams (2007). Identification of Essential Oil Components By Gas Chromatography/Mass
Spectrometry. Allured Pub Corp. ISBN 1-932633-21-9.
• Adlard, E. R.; Handley, Alan J. (2001). Gas chromatographic techniques and applications. London:
Sheffield Academic. ISBN 0-8493-0521-7.
• Eugene F. Barry; Grob, Robert Lee (2004). Modern practice of gas chromatography. New York:
Wiley-Interscience. ISBN 0-471-22983-0.
• Eiceman, G.A. (2000). Gas Chromatography. In R.A. Meyers (Ed.), Encyclopedia of Analytical
Chemistry: Applications, Theory, and Instrumentation, pp. 10627. Chichester: Wiley. ISBN 0-471-976709
• Giannelli, Paul C. and Imwinkelried, Edward J. (1999). Drug Identification: Gas Chromatography. In
Scientific Evidence 2, pp. 362. Charlottesville: Lexis Law Publishing. ISBN 0-327-04985-5.
• McEwen, Charles N.; Kitson, Fulton G.; Larsen, Barbara Seliger (1996). Gas chromatography and
mass spectrometry: a practical guide. Boston: Academic Press. ISBN 0-12-483385-3.
• McMaster, Christopher; McMaster, Marvin C. (1998). GC/MS: a practical user's guide. New York:
Wiley. ISBN 0-471-24826-6.
• Message, Gordon M. (1984). Practical aspects of gas chromatography/mass spectrometry. New York:
Wiley. ISBN 0-471-06277-4.
• Niessen, W. M. A. (2001). Current practice of gas chromatography--mass spectrometry. New York,
N.Y: Marcel Dekker. ISBN 0-8247-0473-8.
• Weber, Armin; Maurer, Hans W.; Pfleger, Karl. Mass Spectral and GC Data of Drugs, Poisons,
Pesticides, Pollutants and Their Metabolites. Weinheim: Wiley-VCH. ISBN 3-527-31538-1.
This information compiled from excerpt sources on the internet including Wikipedia.org
Process Link: http://www.lci.kent.edu/ipp/07/docs/GCMS_QS.doc
LCI News – October 2007
Lavrentovich, Kumar receive Distinguished Scholar Awards
Congratulations to Professors Oleg D. Lavrentovich and Satyendra Kumar for receiving a 2007 Kent
State University Distinguished Scholar Award. The awards were presented by the University Research
Council at yesterday's Distinguished Scholar Awards Luncheon Ceremony at the Kent State Student
Center Ballroom. The awards are given annually for outstanding research and/or creative activities by
tenured/tenured-track faculty members at Kent State University who are nominated by his/her peers.
Lavrentovich and Kumar were two of the six finalists for the award. Psychology professor, Nancy Marsh
Docherty was also named a 2007 Distinguished Scholar. Previous Distinguished Scholar Award winners
from the LCI include: Peter Palffy-Muhoray (1999) and Philip Bos (2006).
To find out more information about their research go to the following links:
Oleg D. Lavrentovich
Satyendra Kumar
Palffy-Muhoray writes feature article in Physics Today; cover photo taken by Lavrentovich
The September issue of Physics Today prominently features an article, “The diverse world of liquid
crystals”, by Peter Palffy-Muhoray, professor of chemical physics and associate director of the Liquid
Crystal Institute. The article provides a solid introduction to the field of liquid crystals, including its
discovery and development, current and historical research, and many applications from beam steering to
cosmetics. Specifically, the article highlights the following aspects of liquid crystals:
• Description and many useful features
• First observations, discovery, and identification of the mesomorphic states of matter,
optical applications, synthesis of mesogens (molecules that form liquid crystals)
• Fundamentals, including: liquid crystals classification based on order, description of
molecular structure, alignment, many mesophases, phase transitions and the chemical
structures of molecules that form liquid crystals
• Development of liquid-crystal displays
• Descriptions of a variety of liquid crystal materials
• Applications in cosmology, astrophysics, lasers, biological systems, cosmetics, spatial
light modulation, beam steering, optical imaging, biological sensors, photo actuation,
flexoelectricy, medicine, fashion, and eyewear.
• Current studies and possible explanations for current phenomenon
The article is not only accompanied by many helpful photos and visuals that describe the liquid crystals
and applications, but also the Physics Today magazine cover features a microscopic liquid crystal texture
photo taken by Oleg D. Lavrentovich.
The article can be found on the publication’s web site (for subscribers only) at
http://www.physicstoday.org/; its draft version can be found at the e-LC web site, http://www.elc.org/index.html.
LC Day set for October 12, 2007
On October 12, the LCI will host the third Liquid Crystal Day which is sure to bring excitement to the
liquid crystal field, showcasing the many achievements of local students and industrial partners. Invited
speakers include Dave Walba, University of Colorado; Jim Yuan, CoAdna Photonics; Rolfe Petschek,
Case Western Reserve University; and Mary Neubert, Emeritus Senior Research Fellow, LCI. The event
will be held from 9am – 5pm in the Liquid Crystal and Materials Sciences Building, Samsung
Auditorium. To find out more, please visit: www.lcd.kent.edu. If you would like to sponsor this event,
please contact Jim Maxwell at 330-672-7770, Maxwell@lci.kent.edu.
Yin Defends
On September 21, Ye Yin defended his dissertation titled: “Dielectric Relaxation and Electrooptical
Effects in Nematic Liquid Crystals”.
Valerie Henry says farewell to LCI after 15 years
Promoted to Grants Coordinator at University Comptroller’s Office
Valerie Henry recently accepted a position as an Accountant with Comptroller's Office in the Grants
Accounting Department. She will act as a financial liaison between the university and various private,
state, and federal awarding agencies for many departments.
Valerie came to LCI as Grants Assistant in 1992 after serving in the temporary pool. She was promoted
to Grants Coordinator in May 2001 when Alexis McKinney retired. We wish her well and thank her for
her many years at LCI!
LCI Says Farewell to Senior Chemist Julie Kim
On August 14, members of the Kent State Liquid Crystal Institute attended a farewell party for Senior
Chemist Julie Kim. She leaves Kent State, after 13 years of service at the Liquid Crystal Institute, to
become a high school chemistry teacher at Fairview High School, a suburban Cleveland school. We thank
her for her hard work and wish her best of luck with her new position.
Scholarship Winners
Samsung Scholarship
Congratulations to CPIP graduate students Shin-Ying Lu and Heung-Shik Park who have been selected
as the recipients of the Samsung Scholarship Fellowships. The students will be supported by the annual
stipend of $22,000 sponsored by Samsung Electronics Corporation.
SPIE Scholarships
Congratulations are in order to three CPIP students, Fenghua Li, Oleg Pishnyak and Bohdan Senyuk, who
have been awarded the prestigious scholarship awards from the International Society for Optical
Engineering (SPIE). To see the winners list, visit: http://spie.org/x13360.xml. SPIE is an international
society advancing an interdisciplinary approach to the science and application of light.
Fall 2007 Seminars
Oct. 10:Lorenzo Marrucci, The National Institute for Nuclear Physics, Naples
Title: "Spinning" and "twisting" a light beam and other wavefront-shaping tricks
performed by suitably patterned liquid crystals
Oct. 31: Ting Zhu, Department of Mechanical Engineering, Georgia Institute of
Title: Modeling Hyperelastic Crystals
Nov. 7: Randall D. Kamien, Department of Physics, Univ. Pennsylvania
Title: On the Stability of Large Angle Grain Boundaries
Nov. 14: Richard J. Spontak, Department of Chemical and Biomolecular Engineering,
North Carolina State University
Title: Molecular Design of Nanostructured Block Copolymers as a Route to HighPerformance Electroelastomers
Dec. 12: L. Jay Guo, Univ. Michigan
Title: Nanoimprint technology and its application in polymer based photonic devices
Monday LC Research Seminars
Liquid Crystal Research Seminars at the Liquid Crystal Institute were established as a means for local and
international faculty, senior research fellows, postdoctoral fellows, alumni, visitors, industrial partners
and students to share and discuss their research with colleagues.
We invite you to present a manuscript that is about to be submitted or has recently been submitted to a
peer-reviewed journal, discuss results from other groups, or present already published results.
To reserve a time slot, please email title, names of authors and, if possible abstract of your presentation, to
Brenda Decker, brenda@lci.kent.edu
LC Research Seminars held October 1
“Three-Dimensional Imaging of Chemical Bond Orientation in Liquid Crystals by Coherent Anti-Stokes
Raman Scattering Microscopy”, Brian G. Saar, Heung-Shik Park, X. Sunney Xie, and Oleg D.
Lavrentovich (presenting) (in collaboration with Department of Chemistry and Chemical Biology,
Harvard University, Cambridge, MA 02138)
“Levitation, Lift and Bidirectional Motion of Colloidal Particles in an Electrically-Driven Nematic LC”
O. P. Pishnyak (presenting), S. Tang, J. R. Kelly, S. V. Shiyanovskii, O. D. Lavrentovich
Please let us know if you would like more detailed information about any activities at the LCI.
Phil Bos