Meeting Days 4 and 5: Wednesday, August 17, and Thursday, August 18

   Blog | Facebook| Twitter

Scientists are not known for their partying, but the dancing that took place until at least 3:00 in the morning after Wednesday"s Gala Dinner at the XX IMRC told a different story. Things really took off once the salsa music kicked in, as dancers filled the dance floor to overflowing, and demonstrated their best moves. Hats and balloons added bursts of color to the spectacle.

Of course, this was just an example of people blowing off steam after a long day of hard work. Wednesday featured a funny and moving Plenary Lecture by Dan Shechtman about the trials that science can bring when you make a discovery that most of your colleagues don't believe, and the eventual triumph of seeing your ideas prevail. Graduate students were recognized for excellence in their poster presentations during the Gala celebration. And several new symposia started up on Wednesday and Thursday, including the much-anticipated second Meeting of the Brazil-Mexico Nanotechnology Center (CBMNano), and Symposium 12 on Strategies for Academy-Industry Relationships. Other symposia, sadly, came to a conclusion. But all in all, it was two days of scientific communication on many levels, with a little fun thrown in.

Credit for the great success of this IMRC is due to the Congress Chairs (L-R)
David Cahen (Weizmann Institue of Science), Armando Salinas (CINVESTAV-Saltillo),
Andrea Hodge (University of Southern California), and Sergio Mejía, President of
SMM and General Chairman of the Congress (Universidad Autónoma de Nuevo León)

Dancing deep into the night after the Gala Dinner

Fourth Plenary Lecture: Dan Shechtman
Quasi-periodic Materials—Crystal Redefined

In a fascinating, funny, and heartfelt exploration of the nature of scientific discovery and the complications that come from being right when most of your colleagues think you are wrong, Dan Shechtman of Technion (Israel) and Iowa State University (United States) told the story surrounding his discovery of quasi-periodic crystals in 1982. Along the way he outlined the history of crystallography and provided a great brush-up tutorial on the subject for those of us who studied it a long time ago.

Shechtman showed the page of his TEM logbook from April 8, 1982, when he performed a selected area diffraction on a pitch black grain of an Al-25%Mg sample and saw a diffraction pattern that indicated 10-fold symmetry, a forbidden crystallographic symmetry state.  He wrote “(10-fold???)” in the logbook and went out into the hall looking for someone to show his discovery, but no one was there. When he started telling colleagues about it, no one believed him, beginning what he called the “the years of rejection,” which lasted from 1982 to 1987. Linus Pauling, a two-time Nobel Laureate, was his biggest opponent. Pauling insisted that Shechtman was observing the effects of twinning, not a diffraction pattern from a single crystal.  But he persevered in his investigations of this forbidden symmetry, using smaller and smaller electron spot sizes, until it became evident that if there was twinning, the twinned particles would have to be smaller than the 400-angstrom electron spot size he was using. He was eventually vindicated when x-ray diffraction data—the de facto standard in deciding crystallographic arguments at the time—showed 5-fold rotational symmetry in 1987.

These crystals were not strictly periodic, so they defied the definition of crystallinity that had been accepted for 70 years. Shechtman had discovered quasi-periodic crystalline materials. Instead of a constant distance between each atom in the lattice, the ratio of distances varied in accordance with the Fibonnaci series, hence the term “quasi-periodic.” This paradigm shift led to a formal redefinition of the word crystal: “By crystal we mean any solid having an essentially discrete diffraction diagram, and by aperiodic crystal we mean any crystal in which three-dimensional lattice periodicity can be considered to be absent.” Shechtman noted the “soft” wording of this definition, and said “suddenly the society of crystallographers became modest. And a good scientist is a modest scientist.”

The pattern of Shectman's "Technion Tie"
that he wore during his plenary talk. A
label inside the tie reads: "An illustration
of an electron diffraction pattern of the
first quasi-periodic crystal discovered by
Distinguished Professor Dan Shechtman."

Poster Award Winners

(L-R) Jim De Yoreo (MRS President), Meeting Chair Andrea Hodge, and Sergio Mejia (SMM President), announcing the Poster Award Winners at the Gala Dinner

Hundreds of posters detailing their research activities were presented on Monday, Tuesday, and Wednesday evenings by graduate students who were eager to let their colleagues know about their scientific work. Of these, three were chosen each night for first, second, and third place awards. The names of these distinguished student researchers were announced at the Gala Dinner on Wednesday night. As part of the SMM-MRS Poster Award Exchange program, the three first place winners will travel to San Francisco for the 2012 MRS Spring Meeting, where their winning posters will be on display. Congratulations to the awardees listed here, and to all researchers who participated in this year's Poster Presentation sessions!

Monday's Poster Session
1st place - S6 P15, Benjamin Portales Martinez 
Synthesis and Characterization of Ni-Mo-W Carbides Produced by Catalytic Via
New Catalytic Materials Symposium

2nd place - S1 P22, Jose Ordoñez Miranda
A Model for the Thermal Conductivity of Nanocomposites with High Volume Fractions of Particles
Advances in Computational Materials Science Symposium

3rd  Place - S6 P02, Laura Ivette Peña Hernández
Effect of EDTA and Citric Acid on Behavior of CoMo/CBA-15 Catalysts in Hydrodesulfurization of DBT
Structural and Chemical Characterization of Metals, Alloys, and Compounds Symposium

Tuesday's Poster Session
1st place - S11 P30, Alvar Paredes-Puerto 
Biocompatibility of Polyurethane Urea Elastomers for Cardiac Tissue Engineering
Biomaterials for Medical Applications Symposium

2nd place - S2 P27,  Jose Flores Livas
Improving the Electron-Phonon Interaction in Layer Disilicides
Advances in Computational Materials Science Symposium

3rd  Place - S5 P49, Jesus Alfonso Caraveo Frescas
Nanoscale Gadolinium Oxide Capping Layers on Compositionally Variant Gate Dielectrics
Structural and Chemical Characterization of Metals, Alloys, and Compounds Symposium

Wednesday's Poster Session
1st place - S9 P39, Carlos Andrés Ortiz Cardona
Optical Properties of Zinc Sulfide Thin Films Doped with Rare Earths for Photovoltaic Applications
Photovoltaics, Solar Energy Materials & Technologies Symposium

2nd place - S9 P55, Alejandro Trejo Baños
Infrared and Raman Responses of Germanium Nanostructures from Ab-Initio Calculations
Photovoltaics, Solar Energy Materials & Technologies Symposium

3rd place - S5 P080, Venkatesan Rajalingam
Effect of Milling Time on BiVO₄ Nanoparticles Synthesized by Mechanochemical Process
Advances in Semiconducting Materials Symposium

Cancun sunset

Technical Talks

Alan Hurd of Los Alamos National Laboratory speaks
about energy critical elements


Symposium 10: Renewable Energy and Sustainable Development

Energy Critical Elements for Sustainability
Alan Hurd, Director of the Lujan Neutron Scattering Center at LANSCE (Los Alamos National Laboratory), was a panelist on a recent joint study by the American Physical Society and the Materials Research Society. In Symposium 10, he presented findings and recommendations from a report released by the panel in February 2011. The report has had a major impact on science policy in the short time since its release. A copy of the full report can be found at www.mrs.org under the Advocacy tab.

ECEs are elements needed for the emergent clean energy infrastructure—typically renewable sources—whose supply is in doubt. Elements used in mature sectors—such as U for nuclear power—have well established policy, regulation, and markets, and therefore were not included in the list of ECEs.

Hurd illustrated the concept of “Energy Critical Elements” and the problems recently encountered in their supply chain with examples involving rare earth magnets. Rare earth elements are used exclusively to make magnets requiring both high field and wide operating temperature range, such as the famous NdFe-B composition widely used since the 1980s. Windmills generate electricity with static—as opposed to induced—magnetic field generators for efficiency reasons. Production scaling, especially for off-shore applications, favors larger windmills. However the shafts of large direct-drive wind turbines necessarily turn slower for the same linear blade tip velocity, a fundamental limitation. Slower rotation requires larger magnetic fields for equal electromotive force. Eddy currents heat up the magnets of large dynamos. Thus, magnetic materials with high energy product, low conductivity, and high Curie temperature are needed for large wind turbines.

Currently only rare-earth-based magnets satisfy the design criteria for wind energy and clean transportation. A 3 MW turbine requires on the order of 700 kg of Nd, and a hybrid car requires 3 kg. The problem is that Nd prices have skyrocketed 750% from 2010 to 2011 after China announced reduced export quotas. China produces 97% of rare earths.  

The ECE report’s main recommendation is to fund research in ECE substitutes, alternatives, and re-use. For the NdFe-B case, Karl Gschneider of Ames Lab invented a Nd-DyFe-B magnet that reduces the Nd requirement by dilution with Dy while also improving thermal characteristics; unfortunately Dy is an acutely critical rare earth itself. Researchers have therefore turned to MnAl, MnBi, and Fe-N systems to reach the requisite performance density.

In response mainly to the APS-MRS report, several bills have circulated in the U.S. Congress to remedy the situation. The first research program was announced by the Department of Energy’s ARPA-E office after the release of the report. A $30M, three-year program calls for rare earth alternatives in high strength magnets, and further programs are expected to follow.

Intense discussions at the Poster Session

Symposium 1: Nanostructured Materials and Nanotechnology

Computer Simulations of Hydrogen Storage in Nanoporous Carbons
Hydrogen is a firm candidate to replace gasoline in cars. A principle advantage in using hydrogen is that it is abundant and non-contaminating. Only 5-6 Kg of hydrogen is needed to run a car for 500 km. However, because hydrogen is a gas, storage problems limit its use as a fuel. Currently, hydrogen can be stored in three different ways: by compressing it, by storing it as a liquid (which requires very low temperatures), and by storing it in metal hydrides. The main problem with storage in metal hydrides is that this system is very heavy. The binding of hydrogen with the metal ions in this system is very strong, making it necessary to invest large amounts of energy to release the hydrogen.

A hydrogen storage alternative may be accomplished through use of porous materials. Due to their large specific surface areas and light weights, these materials could fulfill the practical requirements for easy cyclic adsorption and desorption of hydrogen near room temperature. Julio A. Alonso of the Universidad de Valladolid, Spain, explored the properties of porous carbide-derived carbon materials with molecular dynamics simulations. Nanoporous materials were created by removing metallic atoms in metal carbides, after which the system was allowed to relax. Following the relaxation, the formation of interconnected pores in the compound was observed. One of the main results of this study is that pore size seems to be correlated with hydrogen storage. Another strategy explored the possibility of storing hydrogen by doping carbide-derived materials with metals. In particular, Alonso examined the interaction of hydrogen molecules with Pd-doped nanoporous carbon materials. It was concluded that the dispersed Pd atoms in the porous material can improve hydrogen storage.

  
Exhibitors from Oxford Instruments (left) and Marktek S.A. DE C.V.

Symposium 2: Advances in Computational Materials Science

Towards Atomically Precise Silicon Qubit Devices in All Three Dimensions
Michelle Simmons of the University of New South Wales, Sydney, Australia, is concerned with the fabrication of atomically precise devices for quantum computing applications. During her talk, she presented strategies developed in her group aimed at building atomically engineered silicon qubit devices. These strategies combine Scanning Tunneling Microscope (STM) and Molecular Beam Epitaxy (MBE) techniques. This strategy allows the systematic fabrication and investigation of atomically precise devices. One of the main challenges her group overcame was the manipulation of phosphorous atoms on silicon surfaces with atomic precision. This accomplishment laid a basis for building atomically precise architectures for silicon-based quantum computers.

After discussing the fabrication process on H-passivated silicon surfaces, Simmons displayed some of the devices fabricated in her group and explained their characteristics. For instance, arrangements of double and triple coupled quantum dots were fabricated to enable studies of coherent charge transfer between these dots. A net result of Simmons’ study is the possibility of exploring the fabrication of atomically precise 3D architectures.

Dave Ginley (left), Immediate Past President of MRS, speaking with David Cahen of the
Weizmann Institute of Science, one of the Congress Chairmen

Symposium 5: Advances in Semiconducting Materials

Comparative Study of Silicon-rich Oxide and Silicon-rich Nitride Films
A. Morales Sánchez of Benemérita Universidad Autónoma de Puebla, Mexico, and his co-workers investigated the properties of silicon-rich oxides (SROs) and silicon-rich nitrides (SRNs) for possible use as dielectric materials in LEDs. SROs have been investigated before, but an Si-rich dielectric matrix with a lower bandgap is needed for this application; SRN might provide that property. The researchers prepared samples of SROs and SRNs using low pressure chemical vapor deposition (LPCVD), reacting NH₃with SiH₄ to produce the SRN, and N₂O with SiH₄ to make the SRO. Ellipsometry measurements showed that the SRN films deposited at a faster rate and so formed thicker films than the SROs (a range of 360-380 nm for SRNs vs. 65-100 nm for SROs). FTIR revealed that both samples became hydrogenated at low temperatures, but that the N-H and H-SiO₃ bands disappeared at high temperatures. As predicted, the SRN sample had a lower bandgap than the SRO. The SRN showed photoluminescence in the blue wavelengths, while the SRO displayed red photoluminescence. These two materials were combined to get a white light LED source, according to the researchers.

Congress Chairman Armando Salinas
introducing a plenary speaker

Symposium 12: Strategies for Academy-Industry Relationships

Research, Human Resource Information and Technology Outreach in an Academic Institution in Mexico: The Institute of Engineering-UNAM
The Institute of Engineering of the Universidad Nacional Autónoma de México (UNAM) is widely recognized for great engineering works throughout the country. The mission of the institute is to contribute to Mexican development and societal welfare through engineering research, human resource formation, and social partnership. The institute follows three main strategic principles: (1) contribution to the knowledge and practice of engineering; (2) formation of highly specialized human resources; and (3) technology transfer for social purposes.

The institute specializes in multiple areas of research, including hydraulic and environmental structures, geotechnics engineering, and electro-mechanics. Study in these areas is offered in undergraduate, graduate, and post-doctoral programs.  In these programs, students are required to solve applied or industry-related problems. “This seems to be the main reason why the students who graduate in the engineering department find jobs easily,” stated Francisco Jose Sánchez-Sesma of UNAM. One program that receives less attention from the academic and industrial community is petroleum engineering. Oil companies have not demonstrated significant interest in forming partnerships with academia, according to Sánchez-Sesma.  Another point he highlighted is the lack of a consistent intellectual property practice for registering innovations created in the academic engineering community. Sánchez-Sesma called for greater collaboration among academic institutions and industry.

  
Meeting attendees relaxing during a break


Symposium 13: Advances in Ion-Beam Techniques and Applications

PIXE environmental Applications
PIXE is the acronym for Particle Induced X-ray Emission. This is typically an ion beam-based analytical method which allows the identification of ions based on  X-rays, explained Claudiu I. Muntele of Alabama A& M University in the United States. The method gives highly accurate qualitative analysis and relatively accurate quantitative analysis of elements. The detection sensitivity of elements goes down to ppm for Z>11. This sensitivity is reduced in the case of elements with Z<9 due to instrumental limitations. PIXE is typically used for identification of elements in fields such as art and archaeology, environmental work, medicine, and food.
 
Muntele showed two case studies of environmental applications in which PIXE was used for the identification of elements. The first one concerned a study of pollution performed across Europe. Samples of dirt and vegetation were collected from Romania to Portugal. The dirt data represents a snapshot of regional pollutant distribution. Here, Pb and Zn were among the common elements found. The samples collected in France showed the largest Pb concentrations in vegetation. Pb concentration was highest in large cities, while Zn correlated with automobile traffic. In the second case study, approximately one billion gallons of coal ash were spilled from a TVA power plant in the state of Tennessee in 2008. PIXE was used to identify the elements of this ash.  

Fabrication of Electrodes with Nanometer-sized Gap Tunable by Ion Irradiation
Moore’s law states that the number of transistors that can be placed on an integrated circuit doubles every two years. However, this exponential improvement in electronics is limited by size effects. “Hence, in order to follow Moore’s law, the development of nanoscale electronic devices will require the engineering and modification of new materials on the atomic and molecular scale,” said Juan Carlos Cheang Wong of the Universidad Nacional Autónoma de México. He explores these issues by fabricating H-shaped electrodes with a nanometer-sized gap. These electrodes are 100-nm thick and are created through deposition of Al or Au onto 500-nm thick SiO₂ films on silicon wafers. Subsequently, the samples are irradiated with oxygen ions. Cheang Wong and his colleagues found that these films undergo extreme deformation under exposure to a 4.6 MeV oxygen beam due to the electronic loss of the incoming ions. The deformation is anisotropic and grows as a function of irradiation fluence. In this way, the researchers succeeded in decreasing the micrometer-sized gaps in these samples to the nanometer scale.

  
Another successful poster session!

Symposium 14: Fundamentals and Applications of Functional Oxide Materials in Energy, Information, and Sensing

Atomistic Mechanisms of Thermal Conduction in Layered Oxides
Masato Yoshida and his colleagues at Osaka University, Japan, are interested in revealing the mechanisms behind thermal conduction in the layered oxides Na_xCoO₂  and Ca_xCoO₂. Both compounds consist of planes of CoO₂ separated by layers of Na(Ca). The amount of doping with Na(Ca) ions determines the charge in the CoO₂ planes. Yoshida examines the thermal conductivity of these compounds using ab initio methods. Specifically, he considers the role of each element of the oxide, the influence of Na(Ca) vacancies, and the different valences of Co atoms.

Yoshida demonstrated that the presence of Na vacancies causes significant reduction in the thermal conductivity k. In contrast, the presence of mixed valence ions Co³⁺/Co⁴⁺ does not significantly influence conductivity. A comparison was then performed of the properties of Na_xCoO₂ and Ca_xCoO₂, where different values of doping were considered. Yoshida found that the absolute value of k is smaller in Ca_xCoO₂ than Na_xCoO₂. This result is associated with stronger Ca-CoO₂ bonding, providing evidence that interlayer distance also plays a role in the thermal conduction of these oxides. Comparative analysis of the influence of interlayer interaction, the role of vacancies, and interface distortion on layered thermoelectric oxides can lead to an enhanced ability to tailor the thermal conduction of these systems.

Enjoying the Gala Dinner

Symposium 16: Smart Materials, Devices, and Related Technology

Assessment of Bi-Stable Materials for Morphing Wings
Unmanned aerial vehicles (UAVs), such as the drones used in military operations, could benefit from the ability to change wing shapes in mid-flight to optimize flying in different conditions. I.E. Carranco of the Universidad Autónoma de Nuevo León, México, and his colleagues are investigating materials that will permit this morphing to happen. These materials could be used to instantaneously modify the winglets that bend upwards at the end of a wing; to change the sweep angle of a wing; or to adjust the curvature of the wing flaps. 

The researchers are currently investigating shape-memory polymers and piezoelectric composites for this purpose, and will soon add thermally induced composites to the list. Shape-memory polymers are light, and can be activated over the range of 30 to 260°C. They can be elongated up to 800% and resist oxygen and ozone damage, but are sensitive to hot, wet conditions. Piezoelectric microfiber composites could be used for expansion, bending, and torsion in a wing flap. They can morph very quickly or slowly depending on the applied voltage, but can have trouble with moisture in the environment. Of the two materials studied so far, Carranco said the shape-memory polymer looks like the better choice for now, but they still have many materials to investigate.

Electromagnetism as a Means for Intrinsic Structural Health Monitoring Capabilities in Structural Materials
In an invited talk, Christian Boller of Saarland University, Germany, spoke of the work he and his co-workers are doing to use electromagnetism to detect defects in bulk structural materials. As a tutorial, he reminded the audience that magnets have domains separated by Bloch walls. Under an applied field, the Bloch walls will move. In moving, they will interact with the micro-defects that occur at the initial onset of structural damage. For instance, Bloch walls become pinned at imperfections in the structure. Boller proposed that researchers could learn a lot about what is happening in the early stages of damage processes by listening to the Barkhausen noise that is generated when the Bloch walls move. There is a correlation between the applied stress and the Barkhausen noise, he said. If you measure the amplitude of this noise in two orthogonal directions in a material, you can determine something about the structures with which the Bloch walls are interacting.

Boller gave several examples of how he and his colleagues have used this technique. They have looked at fatigued steel specimens and found that there is a correlation between the surface roughness of the fatigued metal and the measured Barkhausen noise. In residual life assessments of coal drag lines, the traditional procedure is to use the Vickers hardness test, which is destructive. Boller achieved the same results non-destructively by monitoring the Barkhausen noise. In analyzing a copper-steel steam pipe that fractured in a coal power plant, the researchers found that Bloch wall movements induced by mechanical load or by magnetism are analogous. This makes it possible to monitor the Barkhausen noise in a pipe and replace it before it bursts. Boller concluded that Barkhausen noise can be used as a means for effective stress and damage monitoring in structural metals.



Meeting venue--the JW Marriott Hotel

Symposium 17: Diamond Devices—Detectors, Sensors, and Photonics

CVD Diamonds as TL/OSL Detectors for Dosimetry of Ionizing Radiation
Radiation therapy is an important tool for cancer treatment, but there is a high risk for accidental over exposure to x-rays, according to Marcellino Barboza-Flores of the Universidad de Sonora, Mexico. He cited one report of a hospital in which 77 brain cancer patients received 150% of the prescribed radiation dose because the linear accelerator had been incorrectly programmed for a year. An adequate in vivo dosimeter would prevent accidental exposures. Barboza-Flores discussed research that he and his colleagues had performed to find adequate materials that would use thermoluminescence (TL) or optically stimulated luminescence (OSL) to measure radiation doses inside a patient. Both techniques involve charge carriers (electrons and holes) trapped in defects that recombine and emit photons. The number of photons emitted is proportional to the radiation dose. In TL, heat is applied to the detection device to produce thermoluminescence, while in OSL, light initiates the recombination process.

The researchers fabricated diamond films with thicknesses of 3, 6, 12, 180, and 500 microns using microwave plasma chemical vapor deposition from an atmosphere of methane, carbon monoxide, and hydrogen. These thin films, when exposed to non-ionizing UV radiation and optically stimulated with light, proved to be excellent UV dosimeter devices, with a linear response to UV dosing. These diamond thin-film luminescence devices could be implanted inside a patient to provide in vivo, real-time monitoring of radiation doses. Further work is being done to determine how the devices respond to ionizing radiation.

Diamond Nanophotonics and Quantum Optics
“Because nanophotonics exploits the quantum nature of light, it provides a faster alternative to electronics for communication systems,” said Jennifer Choy of Harvard University, United States, at the start of her talk on diamond nanophotonics and quantum optics. After showing the basic ingredients of quantum photonics, she discussed how to develop photonic technologies that make use of diamonds. Why diamonds? Because they posses exceptional physical and chemical properties, are transparent from UV to the far infrared, and have a high refractive index of 2.4. All these characteristics make diamonds useful in the implementation of devices for quantum information, explained Choy.

Novel methods were developed by Choy and her group to generate diamond-based device platforms aimed at confining and emitting light efficiently. Included among these device platforms are planar single crystal diamonds, diamond nanoposts, single crystal diamond rings, and vertical oriented diamond nanowires which act as single-photon antennas.

And the band played on at the Gala celebration

Symposium 23: II Meeting of the Brazil-Mexico Nanotechnology Center (CBMNano)

First Principles Simulations of Dual-Gate Bilayer Graphene Field Effect Nano-Transistor
Limited MOSFET scaling has initiated a pursuit for new materials to replace silicon. Graphene is the strongest candidate due to its 2D character and high charge carrier mobility. However, graphene is gapless. Hence research has been directed towards opening a bandgap. Strategies include introduction of defects, doping, hydrogenation, production of graphene nanoribbons, and application of electric fields to bilayer graphene.

The goal of Ricardo Adazzio of the Instituto de Fisica, USP, Brazil, is to link graphene in electronic devices. In particular, he and his colleagues study the transport properties of a dual gate bilayer graphene device. The device consists of AB-stacked bilayer graphene with a drain voltage applied across the system, which defines the current direction. Electric fields were applied to this system. Adazzio discussed the behavior of the current versus the drain voltage for different values of channel length and back (V_bg)/top(V_tg) gate voltages. Linear behavior of the current with the drain voltage was obtained in all cases. The value of the current increases for increasing values of channel length and (V_bg)/(V_tg) gates. Another observation was that zero current was never observed, even for high electric fields, in accord with experimental work conducted in this area.


Raman Study of Nanotube-substrate Interaction Using Single Wall Carbon Nanotubes Grown on Crystalline Quartz
“We have to remind everyone that nanomaterials in general are subject to interference by the environment,” said Ado Jorio of the Universidade Federal de Minas Gerais, Brazil, at the start of his talk. To prove this statement, he showed the results of Raman spectroscopy studies of carbon nanotubes (CNTs) laid down on quartz in serpentine patterns. Using a quartz plate with a stepped surface morphology, Jorio and his group showed how the nature of CNTs could change from semiconducting to metallic based on their orientation to the quartz steps. When a CNT was positioned parallel to a step, it showed Raman peaks associated with a metallic material; this was due to the close proximity of the CNT to the quartz. Conversely, when the serpentine CNT pattern crossed perpendicularly across several steps, its Raman spectrum was semiconducting. Next, the researchers used a nanomanipulator to push down on the CNT at various points along the serpentine pattern. Again, the enhanced closeness of the CNT to the quartz surface showed a more metallic nature in the CNTs at points under pressure. Jorio concluded that this clearly demonstrated how CNTs are affected by their environment.

 Scanning the Meeting

ABOUT THE MEETING SCENE

The Meeting Scene e-newsletter of the Materials Research Society (MRS) presents news from MRS and other conferences directly from the conference venue.

This work was partially supported by the IMI Program of the National Science Foundation under Award No. DMR 08-43934. Specifically, the work of Apprentice Science Reporter Andrea Salguero was funded under this NSF award, which is managed by the International Center for Materials Research, University of California, Santa Barbara, USA.

• The Meeting Scene is edited by Tim Palucka, Science News Editor, with contributions from Andrea Salguero and Betsy Fleischer.
• You have received this as a subscriber to the Meeting Scene.
• You can unsubscribe from this service by e-mailing us.
• View all free MRS e-newsletters and alerts and subscribe.

© Materials Research Society, 2011