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American
Vacuum Society – New England Section
Session A Chair: Peter Somssich Speaker Contact Information Speaker Contact Information 9:00 - 9:30 Joel Therrien “Optical Handedness in Graphene” UMass Lowell Joel_Therrien@uml.edu 9:30 - 10:00 Mohan Ananth “An Introduction to the Helium Ion Microscope” Carl Zeiss SMT, Inc m.ananth@smt.zeiss.com 10:00-10:15 COFFEE BREAK 10:15 - 11:15 Bob Levin “Colors-Real and Imaginary” (KEYNOTE) Osram Sylvania, Inc Robert.Levin@sylvania.com 11:15 -1:00 LUNCH LUNCH Session B Chair: Jim Whitten Session C Chair:
Mars Hablanian 1:00 - 1:30 Masaru Tsuchiva “Novel Experimental Approaches to
Structural-Property Relationships in Nanoscale Zirconia…” Harvard University tsuchiya@fas.harvard.edu Bing Sun “RHEED-TRAXS for In-Situ, Real-Time Stoichiometry
Analysis” Northeastern Univ. sun.b@neu.edu 1:30 - 2:00 Jagdeep Singh “Thiol Induced
Modification and Encapsulation of ZnO Nanorods” UMass Lowell Jagdeep_Singh@ student.uml.edu Jim Litynski “Temperature and Vibration Influences on
Piezoelectric Flexure-Based Positioning Systems in Vacuum” PiezoSystem Jena Jim@piezojena.com 2:00 - 2:45 COFFEE/POSTER SESSION COFFEE/POSTER SESSION 2:45 – 3:15 Dana Filoti “Effect of Amorphous SiO2 Content
on the Fiber Texture of Au-SiO2 Composite Thin Films” Univ. New Hampshire dlk3@cisunix.unh.edu Luke Hinkle “Solar Photovoltaic
Implementation: A Review of Business Models and Technologies” My Generation Energy, Inc. Luke@complex2simple.com 3:15 – 3:45 Albert Schnieders “Defect Analysis in the Semiconductor
Industry by TOF-SIMS Tascon USA, Inc albert@tasconusa.com Qingzhous Cui “Hybrid Al/Ni Nanostructures to Construct
Nanoscale Heating Sources” UMass Lowell qingzhou_cui@uml.edu 3:45 – 4:15 D.-L. Liu “Optimal Surface Parameters for Minimal
Adhesion” Worcester Polytechnic deli@wpi.edu Poster
Presentations Photonis USA
POSTER New
Scintillators and Photomultiplier Modules for Sub-Nanosecond Optically Coupled Ion
Detectors Steve Ritzau, Paul Mitchell, Bill
Morris, Bruce Laprade Photonis USA POSTER Vapor Sensing
Properties of Thiol-Protected Gold Nanoparticle Films Jisun Im, S.K. Sengupta and James E.
Whitten* Department of Chemistry and
Center for High-Rate Nanomanufacturing The University of Massachusetts
Lowell, Lowell, MA 01854 KEYNOTE
SPEAKER Colors – Real
and Imaginary Dr. Robert Levin This presentation will be a brief introduction to
color as it applies to light, objects, and the interaction of light and
objects. It will address methods of quantitatively describing color as
well as some of the problems when visually evaluating color. Various
demonstrations will be made emphasizing subtle effects that often go unnoticed. Biographical
Sketch Dr. Robert Levin is Corporate Scientist at OSRAM
SYLVANIA. He took both his undergraduate and graduate degrees at Stanford
University. Prior to joining the former GTE Sylvania in the 1960s, he was
an associate professor at California State University in San Jose. He has
worked in many fields relating to light and non-ionizing radiation such as
optics, color and vision, radiation biohazards, human factors, and even
cinematography. Thiol-Induced
Modification and Encapsulation of Zinc Oxide Nanorods Jagdeep Singh1, Jisun Im1,
Jason W. Soares2, Diane M. Steeves2, James E. Whitten1 1Department of Chemistry,
University of Massachusetts Lowell, Lowell, MA
01854 2U.S. Army Natick Soldier
Center, Natick, MA 01760 Abstract The wide
bandgap and bimodal (UV and green) photoluminescence spectrum of zinc oxide
make it attractive for electronic and sensor applications. Toward the goal of
altering its electronic spectrum, the adsorption of a variety of thiols on zinc
oxide nanorods and nanoparticles has been studied using surface science
techniques, and comparison has been made to adsorption on macroscopic ZnO(0001)
single crystals. Covalent bonding of thiols to ZnO surfaces is confirmed by
X-ray and ultraviolet photoelectron spectroscopies (XPS and UPS) and by
monitoring photoemission signals as a function of surface temperature. XPS
studies of the O1s region demonstrate that thiol adsorption occurs via
replacement of surface hydroxyl groups. The effects of thiol adsorption on
photoluminescence and UPS spectra of zinc oxide are described. A novel
method of encapsulating ZnO nanorods is also described that consists of
stirring an ethanolic mixture of oven-dried zinc oxide and thiol while heating
at 75oC. In the case of 1-dodecanethiol, this process results in
complete encapsulation of the nanorods within a thick, organic matrix
consisting of a 1:2 Zn:thiol complex (i.e., R-S-Zn-S-R complex), as indicated
by electron microscopy, XPS, and Raman spectroscopy. The encapsulating layer
results from the partial dissolution of the metal oxide and reaction of
dissolved Zn with solution-phase thiols. In the case of 2-naphthalenethiol,
dissolution occurs to a greater extent, resulting in encapsulated spherical ZnO
particles surrounded by a fluorescent matrix. Possible applications of this
method are discussed. Biographical
Sketch Jagdeep
Singh is a PhD candidate in the Polymer Science Program of Dept. of Chemistry
at University of Massachusetts Lowell. He received his M.S. degree in Polymer
Science and Technology from the Indian Institute of Technology, Delhi, India in
2002. His research focuses on functionalization and characterization of
semiconducting materials using the self-assembled monolayers. He is also
conducting research related to force-distance measurements using atomic force
microscopy on functionalized surfaces for alignment and registration
applications in nanomanufacturing. An
Introduction to the Helium Ion Microscope Dr.
Mohan Ananth Carl
Zeiss SMT, Inc. One
Corporation Way, Peabody, MA 01960 Abstract The Helium Ion Microscope (HIM) has been described as an impact
technology offering new windows into nanoscale imaging. Combining a high
brightness Gas Field Ion Source (GFIS) with unique sample interaction dynamics,
the helium ion microscope provides images offering unique contrast and
complementary information to existing charged particle imaging instruments such
as the SEM and TEM. Formed by a single atom at the emitter tip, the helium
probe can be focused to below 0.25nm offering the highest recorded resolution
for secondary electron images. The small interaction volume between the helium
beam and the sample also results in images with stunning surface detail. Besides high resolution imaging, the helium beam can be used
for performing materials analysis. Using the properties of backscattered helium
– specifically their energy and scattering angle – the mass of the scattering
nuclei can be determined. The unique
combination of ion scattering spectroscopy and sub-nanometer resolution
microscopy opens the door to new and so far unexplored applications in
materials analysis and process control. The helium beam can also be used as a
nano-scalpel for performing precise and controlled milling of soft materials.
This can be further enhanced in the presence of appropriate chemical precursors
resulting in structures with high profile fidelity. This talk will introduce the helium ion microscope and explore
some of the unique information this technology provides. We have applied this
novel technology across a broad spectrum of multidisciplinary applications to
assess its utility and advantages over alternative techniques. We will share
our vision for this product and give an update on how this tool is being used
by researchers worldwide. Biographical
Sketch Dr.
Mohan Ananth is the Director, Product Management with Carl Zeiss SMT, Inc. for
the Orion Helium Ion Microscope. Before joining Carl Zeiss in 2007, Dr. Ananth
spent 10 years in the semiconductor industry in a variety of roles ranging from
applications engineering and product marketing to research and development. At
KLA-Tencor, a semiconductor equipment manufacturer, he managed an applications
team of 25 engineers worldwide responsible for product demonstrations and
customer engagements. At Micron Technology, a semiconductor manufacturer, he
worked in Metrology research and development and developed and managed vendor
relationships for providing leading edge metrology solutions. He has a B.E. in
Metallurgical Engineering from the Indian Institute of Technology, Roorkee,
India, M.S. and Ph.D. in Metallurgical Engineering from the University of
Tennessee, Knoxville, and an MBA from Cornell University. Defect Analysis in the
Semiconductor Industry by Time-of-Flight Secondary Ion Mass Spectrometry Albert Schnieders1, Thanas Budri2 1 Tascon USA, Inc, 100 Red
Schoolhouse Road, Bldg. A-8, Chestnut Ridge, NY 10977, e-mail: albert@tasconusa.com 2 National Semiconductor
Corporation: 5 Foden Road, South Portland, ME 04106 Abstract Secondary
Ion Mass Spectrometry (SIMS) has developed into an important for depth
profiling, implanter matching and dopant characterization as well as for
surface characterization (trace metal and organic contaminations) and failure
analysis. Time-of-Flight SIMS (ToF-SIMS) is especially well suited for the
latter tasks because of the parallel mass detection with no need to tune the
mass spectrometer to a few pre-selected ions before the analysis. Additional
advantages for failure analysis are the high lateral resolution and
3D-profiling capabilities. In this
presentation, we will present several examples for failure analysis in the
semiconductor industry, where ToF-SIMS analysis provided valuable information
for solving a specific problem. The applications range from the identification
of micrometer-sized particles buried under several 100 nm thick capping layers
to dopant analysis on features with lateral dimensions of some 100 nm. We will
also discuss technical aspects of the analysis such as navigation to defect
sites on full wafers or the selection of the best suited analysis conditions
with respect to the competing demands for lateral resolution, mass resolution
and sensitivity. Biographical Sketch Albert Schnieders is the General Manager
of Tascon USA, a contract laboratory specializing in chemical surface analysis.
He additionally holds a position as an application scientist at ION-TOF USA,
the US subsidiary of the leading ToF-SIMS manufacturer. Albert graduated in
Physics at the University in Muenster, Germany. He earned his PhD degree for
fundamental studies of sputtered particles using laser post-ionization in the
group of Prof. Alfred Benninghoven. He then worked as a postdoctoral researcher
with Prof. Beebe at the University of Utah and the University of Delaware
before joining ION-TOF USA and Tascon USA. Reflection
High Energy Electron Diffraction – Total Reflection Angle X-ray Spectroscopy
(RHEED-TRAXS) for In-Situ, Real Time Stoichiometry Analysis Bing Sun, Martina List,
Katherine Ziemer Northeastern University, Dept. of
Chemical Engineering, Boston, MA 02115 Abstract Multifunctional
heterostructures of functional oxides, such as ferroelectric barium titanate
and piezoelectric lead zirconate titanate, integrated on semiconductor
platforms are of interest to the development of next-generation smarter,
smaller and more energy efficient devices. These multi-element oxide materials
exhibit measurably different functional properties with structure changes or
stoichiometry changes of less than one percent. The goal of fabricating
multifunctional heterostructures by Molecular Beam Epitaxy (MBE), is to take
advantage of this sensitivity of functional properties by controlling the
stoichiometry and structure of each layer. Thus to grow films with desired
properties, an atomic level, real-time stoichiometry measurement technique is
required, and not yet available. Reflection
High Energy Electron Diffraction - Total Reflection Angle X-ray Spectroscopy
(RHEED-TRAXS) has the potential to achieve real-time stoichiometry control in
the ultra-high vacuum (UHV) environment of MBE by analyzing characteristic
x-rays emitted during standard RHEED operation.
RHEED-TRAXS probes the top 20 to 30 Å of material with < ¼ monolayer
sensitivity. RHEED-TRAX has been
demonstrated through qualitative analysis of growing films. However, no quantification
methodology of RHEED-TRAXS spectra has been developed. In this work, single
element films deposited on a SiC substrate are being used to develop an
effective RHEED-TRAXS quantification strategy.
Biographical
Sketch Bing Sun is 3rd year Ph.D. graduate student
in the Chemical Engineering Department at Northeastern University. She works in
the Interface Engineering Laboratory under the advisement of Dr. Katherine S.
Ziemer. Her research topic is development of Reflection High-Energy Electron
Diffraction–Total Reflection Angle X-ray Spectroscopy (RHEED-TRAXS) for
real-time, in-situ stoichiometry control
during Molecular Beam Epitaxy. Bing has
8 publications with one additional publication under review. Effect of
Amorphous SiO2 Content on the Fiber Texture of Au-SiO2 Composite
Thin Films Dana Filoti, A.M. Brown, D. Carlson,
J.M.E. Harper Dept. of Materials Science,
The DeMeritt Hall, Durham, NH
03824 Abstract Sputtered metal-insulator
composite thin films, such as Au-SiO2, develop attractive physical
properties that rely on their composition and microstructure characteristics.
These properties help in controlling and developing performance capabilities of
thin film based devices. We explored characterization of thin film
microstructure on Au-SiO2 composite thin films through x-ray
diffraction pole figures and transmission electron microscopy. The effective
non-invasive x-ray diffraction method shows that the Au-SiO2
composite microstructure experiences a more rapid loss of
fiber texture as a function of composition than can be explained only by the
decreasing Au volume fraction. Compositional changes were investigated
through transmission electron microscopy that shows the Au grain size in Au-SiO2
composite thin films to have different size characteristics when compared to
the grain size in Au
thin films of the same Au content. The
presence of small silica volume fractions (<5 at. %) suppresses the growth
of (111) oriented Au grains by acting as second phase particles pinning the
metal grain boundaries. The metal grain growth process becomes inhibited and
correlates with the loss of texture with increasing silica content. Biographical Sketch Dana
Filoti currently
is a Ph.D. student in the Materials Science Program at the University of New
Hampshire and she received a B.S. in Physics from University of Bucharest,
Romania. Her research activity and interests are in thin films materials
science. Her research work explores morphological and microstructural evolution
of magnetron sputtered phase segregated metal composite thin films, using novel
characterization methods for nanomaterials. Together with her lab mates, their
research work achievements and originality received the 2007 Award of
Excellence at the Undergraduate Research Conference, Interdisciplinary Science
and Engineering Symposium, at the University of New Hampshire. Optical
Handedness in Graphene Prof. Joel Therrien Department of Electrical and
Computer Engineering University of Massachusetts
Lowell, Lowell, MA 01854 Abstract Graphene
is one of the oldest materials ever produced; the first time anyone scraped
graphite against a surface, graphene was no doubt created. Yet until 2004, its
existence beyond theoretical physics was unknown. What has enabled the ensuing
explosion in research is the simple and highly effective method for finding it
on a substrate. One only needs a specific thickness of silicon dioxide and a
microscope to find it. Since then graphene has continued to yield surprise
after surprise. Here we show that graphene has the unexpected property of
optical chirality: The effect of rotating the polarization of incoming light.
This is surprising because the structure of graphene does not suggest that
chirality should be observed; there is no inherent handedness in the lattice
that typically brings the effect about. Furthermore, the fact that the effect
of the chirality is visible for even a single atomic layer indicates that the
chirality is very strong. The existence of this effect may have consequences
for a large number of experiments. In addition, this effect provides a method
for simple and rapid identification of graphene on a wide variety of surfaces,
thus freeing the use of graphene from the constraints on substrates that has
existed to date. Biographical Sketch Dr. Joel
Therrien received his Ph.D. in Physics from the University of Illinois at
Urbana-Champaign in 2002. He worked as a postdoctoral fellow at the NASA
Institute for Nanoelectronics and Computing at Purdue University, working on
UHV and RF Scanning Tunneling Microscopy techniques. He joined the department
of Electrical and Computer Engineering at the University of Massachusetts
Lowell as an assistant professor in the fall of 2005. His research interests
include: Nanomaterial based optical and mass sensors, High speed Atomic Force
Microscopy, and graphene synthesis. Optimal Surface
Parameters for Minimal Adhesion D.-L. Liu1, J.
Martin2, N.A. Burnham1 1Department of Physics, Worcester Polytechnic
Institute, Worcester MA 2J. Martin, Micromachined Products Division, Analog
Devices Incorporated, Cambridge MA Abstract Surface roughness has a
significant influence on adhesion. We used a single-asperity model to describe
a smooth tip in contact with a rough surface and predicted that an optimal size
of asperity will yield a minimum of adhesion. Experimentally, adhesive forces
on silicon wafers with varying roughness were measured using AFM cantilevers
with varying tip radii. It was found that minima do exist, and for all tip
radii, the adhesion falls significantly for roughness greater than 1-2 nm and
drops at higher roughness for larger tips.1 In addition to RMS roughness, the
roughness exponent is another important parameter for the characterization of
rough surfaces and its influence on adhesion was also investigated. We developed computer
programs to simulate a set of fractal rough surfaces with differing roughness
exponents. The adhesive forces between an AFM tip and the fractal surfaces were
calculated. The simulated adhesion as a function of RMS roughness was
consistent with the experimental results and the adhesion was seen to decrease
as the roughness exponent increases. Experimental work is underway to verify
the predictions about roughness exponent. This work should help minimize MEMS stiction and
progress the understanding of nanoscale contact mechanics. Biographical
Sketch Deli Liu graduated from Rensselaer
Polytechnic Institute in 2004 with a Ph.D. in Physics. She is currently a
Postdoctoral Fellow at Worcester Polytechnic Institute. Her research has been
focused on mechanical properties of nanostructures and thin films, adhesion,
properties of microsensor surfaces, and metrology for nanomechanics. Novel Experimental
Approaches to Study Structural-Properties Relationship in Nanoscale Zirconia
and Ceria Thin Films: The Use of Photon Irradiation, Molecular Beam Synthesis
and Ion Beam Analysis Masaru Tsuchiya* and Shriram Ramanathan School of
Engineering and Applied Sciences, Harvard University, MA 02138 * Presenter; 9 Oxford Street, Cambridge, MA, 02138, Abstract Sub-100nm ceria and zirconia films are of great interest
particularly in energy and electronics applications, including heterogeneous
catalysts and fuel cells. However, the complexity in these material properties
creates many intriguing technical challenges. In this presentation, we will
demonstrate our unique experimental approaches to advance the understanding on
structure-properties relationship in nanoscale ceria and zirconia. We
studied the oxygen concentration changes during ultraviolet (UV) irradiation by
using D+ nuclear reaction analysis and found that the oxygen
concentration can be increased by ~3% at room temperature. UV photon
illumination is an effective route to enhance oxygen kinetics due to the
proximity of photon energy to the bond energy of oxygen molecules. This can
lead to interesting changes in conductivity as well. Furthermore,
we studied the effect of microstructure on electrical conductivity relaxation
in ceria by using MBS (molecular beam synthesis) grown highly-textured film and
nanocrystalline e-beam grown ceria films. The relaxation time for MBS films was
found to be microstructure dependent and faster in the case of the
nanocrystalline films. The results highlight the importance of grain boundaries
in controlling kinetics of oxygen incorporation. We expect these results will
be of importance to broad vacuum and materials science community. Biographical Sketch M. Tsuchiya received the B.E. degree from
Keio University, Japan in 2005 and the M. S. degree from Harvard University in
2007, both in Applied Physics. He is currently a PhD candidate in Applied
Physics at Harvard School of Engineering and Applied Sciences under the
supervision of Professor Shriram Ramanathan. Hybrid Al/Ni Nanostructures to Construct Nanoscale
Heating Sources Qingzhou Cui 1, Julie Chen2,
and Zhiyong Gu1, 1Department of
Chemical Engineering and 2Department of Mechanical Engineering University of Massachusetts Lowell, One
University Ave, Lowell, MA 01854 Abstract Nanoscale heating sources (“nano-heaters”) based on exothermic
reaction between reactive materials of aluminum (Al) and nickel (Ni) have
received great attention in recent years. The advantages of using Al-Ni alloy
forming reaction as heating sources include rapid and intense heat release
(large reaction enthalpies: -37.85 to -71.65 kJ/mol), versatile ignition
methods (electrical, heat, IR, plasmonic induction, and microwave), and
reaction product of Al/Ni alloy being conductive. These advantages make the
hybrid Al/Ni nanostructure promising to be used in many applications such as
heating sources in soldering, adhesive droplet, lab on a chip, polymer memory
devices, and biomedical engineering such as hyperthermia in cancer treatment.
In this presentation we will show that Al-Ni hybrid metallic nanostructures are
fabricated by a combined method of electrodeposition and thermal evaporation,
and the hybrid nanostructures have been characterized by SEM, TEM, and EDAX.
Preliminary tests on the ignition of the Al-Ni nanostructures are performed in
the presence of inert gas such as argon or nitrogen. Biographical Sketch Qingzhou Cui received his Bachelor’s
degree in Applied Chemistry from Beijing University (China) in 1998 and his
Ph.D. in Electrochemistry from Ohio University in Nov. 2006. From Feb. 2007 to
March 2008, he was a postdoctoral fellow in the Department of Chemistry at the
University of Pittsburgh. He has been conducting postdoctoral research in Prof.
Zhiyong Gu’s group at Solar Photovoltaic Implementation: A Practical Review of
Business Models and Technologies Luke Hinkle My Generation Energy, Inc., Brewster, MA Abstract Why does solar energy (finally) make sense for general application
now? How does solar photovoltaic integrate with residential and commercial
electric systems? What are the economics for installing it on a house or
business? Will utility-scale solar become viable in the New England? What are
the infrastructure issues that limit widespread implementation of photovoltaic
sourced energy? What technology developments are required to enable broader
implementation in New England? Using compelling illustrations and practical
examples, our interactive discussion will answer these questions and possibly
raise a few others. Biographical Sketch Luke
Hinkle is the founder of My Generation Energy, Inc. a solar energy installation
and development company based in Temperature and Vibration Influences on Piezoelectric
Flexure-Based Positioning Systems in Vacuum Jim Litynski Piezosystem
Jena, Inc. 2 Rosenfeld Drive, Hopedale, MA 01747 Abstract Piezoelectric
flexure-based positioning systems are well suited to vacuum applications due to
their fricton and stiction free design consisting only of electrically wired
ceramic parts bonded into preloaded monolithic mechanical structures.
However, piezoelectric/metal structures have some unique properties
specifically with regard to temperature conditions in the environment. An
overview of cryogenic, room temperature and high temperature operation of these
devices will be presented. Since piezoelectric flexure-based positioning
systems are often called upon to preform nanometer scale positioning tasks,
vibrational influences limit the resolution of the system and may introduce
errors in closed loop operation. An overview of the effects of
vibrational influences from the environment and those induced by control
electronics when a closed loop system is placed under high load conditions will
also be discussed. Biographical Sketch Jim Litynski is
president of Piezosystem Jena, Inc. and has been involved in piezoelectric
nanopositioning devices and technology for 15 years. Prior to this he was
a product manager for piezo and laser systems at Linos Photonics and an
applications engineer for opto-mechanics at Spindler and Hoyer. He holds
a B.S. in Physics from Rensselaer Polytechnic Institute.
Poster
Presentations “Enabling High
Pressure Operation via a Novel Channel Electron Multiplier” Paula Holmes, Bruce Laprade, Steve
Ritzau Photonis USA Abstract The increasing
demand for portable mass spectrometers has resulted in the need for small ion
detectors capable of operating without sophisticated vacuum pump technology.
PHOTONIS USA has developed a miniaturized channel electron multiplier that can
deliver high performance at pressures up to 10-2 torr. The
MegaSpiraltron is a physically small and robust ion detector that can achieve
high gain while maintaining low noise. The six channel internal spiral
structure provides long life and facilitates operation at elevated pressure by significantly
reducing ion feedback generated by the presence of residual gas molecules in
the channels. Data
will be presented which illustrates the successful operation of the
MegaSpiraltron multiplier at elevated pressures. The ability to operate in poor
vacuum was determined by measuring the background noise or dark current as a
function of pressure at various gain levels. Electrical characterization data
will be presented in the form of gain vs voltage curves. The gain as a function
of pressure up to 10-2 torr was also determined. Finally, life tests
were performed by measuring the change in gain as a function of extracted
charge under high vacuum conditions. POSTER New
Scintillators and Photomultiplier Modules for Sub-Nanosecond Optically Coupled Ion
Detectors Steve Ritzau, Paul Mitchell, Bill
Morris, Bruce Laprade Photonis USA Abstract Optical
coupling of detectors in time of flight (TOF) mass spectrometers enables
bipolar post-acceleration and fast polarity switching without the problems and
risks associated with capacitive coupling. In these detectors, the
initial ion detection is achieved with a microchannel plate (MCP). This
signal is then passed to a scintillator, which converts the electron signal to
light, and then to a photomultiplier tube (PMT), which converts the optical
signal back to electrons, amplifies it, and outputs a ground-referenced output
pulse. While the MCP is extremely fast, the scintillator and PMT limit
the speed of the detector. We present data on new scintillators and PMT
modules constructed and tested to characterize gain and timing performance.
Fast PMT modules with FWHM pulse widths of <600 ps are demonstrated, along
with scintillators with decay times of <500 ps. These represent
substantial improvement over the fastest PMT (FWHM=1000-2000 ps) and
scintillators (decay time=700 ps) that are currently commercially available.
Overall detector pulse widths of <800 ps provide nearly double the
mass resolution at low mass when compared to data taken in the same instrument
with the prior state-of-the-art detector. POSTER Vapor Sensing
Properties of Thiol-Protected Gold Nanoparticle Films Jisun Im, S.K. Sengupta and James E.
Whitten* Department of Chemistry and
Center for High-Rate Nanomanufacturing The University of Massachusetts
Lowell, Lowell, MA 01854 Abstract Thiol-protected
gold nanoparticle films have been studied as chemiresistive vapor sensors.
These generally swell from sorption of analyte molecules, increasing their
electrical resistance due to increased interparticle separation and decreased
electron tunneling probability. The vapor sensing properties of films comprised
of gold nanoparticles protected by 16-mercaptohexadecanoic acid (MHDA), p-terphenylthiol
(TPT), and 1H,1H,2H,2H-perfluorodecanethiol (PFDT) have been studied.
Transmission electron microscopy, quartz crystal microbalance measurements, and
photoemission have been used to characterize the films. While MHDA and TPT
films exhibit responses consistent with a swelling mechanism, PFDT films show a
decrease in resistance for all vapors investigated. This anomalous behavior is
believed to be due to the relatively large interparticle separation and
insulating properties imparted by the PFDT ligands, and these cause the
relative permittivity of the film to dominate its resistance. The combination
of these sensors is being used to construct a portable, battery-operated vapor
sensor system. Biographical Sketch Jisun Im
is currently a Ph.D. candidate in Polymer Science Program of Department of
Chemistry at University of Massachusetts Lowell. She received her Bachelor of
Science and Master of Science degrees in Polymer Science and Engineering at
Pusan National University in South Korea for work on the organic-inorganic
hybrid nanocomposite. Her present research interests include surface chemistry
and chemiresistors based on thiol-modified gold nanoparticles. |
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