2004 MRS Fall Meeting

The most important thing is to get the material - then you can develop the device. Without the material, you can't make any progress! You get nowhere.
- Nick Holonyak

Gawd! This thing has gain!
- Walter Brattain, December 16, 1947, observing "transistor action" for the first time

The major event of the day was the awards ceremony in the evening. MRS President Howard Katz first recognized the officers of the Society. He invited everyone to visit the von Hippel Website (vonhippel.mrs.org), a memorial Website for Prof. Arthur von Hippel after whom the Society's highest honor, the Von Hippel award, is named. Next, secretary Alan Hurd read out the names of the Graduate Student Award winners as they came and accepted their award from President Katz. MRS vice-president Dave Eaglesham then read out the citations for the MRS Medal award winners as President Katz presented the awards. The first MRS Medal was awarded to Jacob N. Israelachvili (Univ. California, Santa Barbara) and the second Medal was awarded jointly to Toh-Ming Lu (Rensselaer Polytechnic Inst.) and Sunil Sinha (Univ. Cal. San Diego). Then, the David Turnbull Lectureship was presented to Frank Bates (Univ. Minnesota).

Finally, President Katz presented the the Von Hippel award to Prof. Nick Holonyak Jr. (Univ. Illinois, Urbana-Champaign). Due to health reasons, Prof. Holonyak was not able to attend the ceremony, so his former student Prof. Russell Dupuis, currently an Endowed Chair Professor at Georgia Tech. accepted the Von Hippel award on his behalf.

Prof. Russell Dupuis then gave Holonyak's Von Hippel presentation on "From Transistor to Laser and Light-Emitting Diode". [Holonyak Website] He started by showing a brief video of Holonyak giving a presentation and talking about his mentor, John Bardeen (the only two-time Nobel prize winner in Physics). Holonyak was Bardeen's first graduate student. With the discovery of the transistor (Bardeen and Brattain, 16 December, 1947), and as a consequence carrier injection and collection, the hole has indeed became equal to the electron. The semiconductor took on new importance, as well as the study of electron-hole recombination, first in the transistor materials Ge and Si, and then in III-V crystals (GaAs, GaP, etc.). Beyond Si and its indirect-gap and heterojunction limitations, the direct-gap III-V materials, particularly III-V alloys, made possible lasers and light emitting diodes (LEDs), and thus optoelectronics. The first practical visible-spectrum LED, not to mention the first III-V alloy device, a first laser, began (1960-62) with the direct-gap III-V alloy GaAs1 xPx, which is also the beginning of III-V epitaxy. Of special importance, GaAs1 xPx established the viability of III-V alloys and, with its energy-gap and wavelength "tunability," set the basis, the direction for construction of heterojunctions. The progression over four decades from the direct-gap alloy GaAs1 xPx, the prototype, to later AlxGa1 xAs and next In1 xGaxP, to then the shorter wavelength direct-gap alloy In(AlxGa1 x)P, and to more recently In(AlxGa1 x)N, has led to heterojunction LEDs that cover all of the visible spectrum.

In addition, various III-V alloys, with increasingly sophisticated crystal growth and processing technology, have led to high performance quantum well lasers, as well as quantum well LEDs, over a broad range of wavelength and power. The direct-gap III-V alloy LED after four decades exceeds the incandescent lamp (as well as other forms of lamps) in performance in much of the visible range. Beyond growing display applications, it has put conventional lighting under long range threat with a semiconductor lamp - an ultimate lamp that promises unusual performance and energy saving. In principle the LED or laser, basically a p-n junction, is an ultimate lamp that cannot be exceeded, that is, in theory every electron can be converted into a photon. Dupuis presented example of current LEDs in use including some new cars with LED headlights that will be available soon. He concluded by mentioning some intriguing new work by Holoyak and co-workers on a transistor that is also a laser diode.

Jacob N. Israelachvili (Univ. California, Santa Barbara) received the MRS Medal "for work on adhesion and friction, which has revolutionized the understanding of molecular mechanisms responsible for these technologically vital phenomena." His talk reviewed some recent experimental results, including theoretical modeling and computer simulations, on the effects of surface texture, surface energy, and the bulk properties of materials on their adhesion and friction and, in turn, on some of the fundamental differences between Mode I and Mode II failure of materials. Examples and comparisons included surfaces that are rough or smooth, hard or soft (e.g., viscoelastic), adhesive or non-adhesive, dry (unlubricated) or lubricated.

Adhesion and friction determine Mode I and Mode II fracture (failure) mechanisms as well as many other mechanical properties of materials, both hard and soft. With the miniaturization of components, such as MEMS, having ever-smoother surfaces, and the growing use of nanoparticle arrays, effects that may be unimportant at the macroscale now become crucially important at the nanoscale. Thus, as sizes shrink, there is an increasing importance of the area of (exposed) surfaces relative to the (unexposed or interior) volume of the bulk material, which render adhesion and friction phenomena more important. Smaller particles also have shorter relaxation times or equilibration times for various processes, for example, sintering, grain boundary growth and processes that depend on surface diffusion, due to the much smaller areas and amounts of material involved. Thus, many processes that involve adhesion, friction and non-equilibrium rate effects become highly interrelated. Recent studies are clarifying the molecular and atomic basis of many well-established adhesion and tribological laws and empirical observations, and revealing new insights and relationships between nanoscale (molecular) and macroscale processes. The talk also focused on the sometimes crucial importance of the effects that occur at the sub-nanoscale, i.e., in the sub- ångstrom or pico-scale regime. Israelachvili argued that the ultra-fine pico-scale details of a surface lattice or its roughness can be the most important factor in determining its friction and Mode II fracture, whereas such effects are quantitatively less important for adhesion and Mode I fracture processes.

Toh-Ming Lu (Rensselaer Polytechnic Inst.) and Sunil Sinha (Univ. Cal. San Diego) gave their MRS Medal presentations in the afternoon. Lu's talk was on "Mechanisms on the Morphology of Thin Film Growth". It is well known that during either deposition or etching of a film the surface morphology very often tends to become rough under a variety of processing conditions at sufficiently low substrate temperature and far from equilibrium. Surface morphology controls many physical properties of a film such as wetting, friction, magnetization, and electrical conductivity. With recent development of modern characterization tools including real space imaging and diffraction techniques, the growth front roughness evolution can be studied quantitatively.

On the theoretical side, conventional statistical mechanics treatment cannot be used to describe this complex phenomenon. Two decades ago, a dynamic scaling concept was introduced to describe this phenomenon. By employing the dynamic scaling concept combined with analytical modeling including the use of stochastic differential equations and simulations, considerable progress has been made in the basic treatment of the phenomenon. In the dynamic scaling description, the root-mean-square roughness of the surface, or the interface width, grows as power law in time, w ~ t b. The b is called the growth exponent. A small b implies a smooth surface and a large b implies a rough surface. One outstanding outcome of dynamic scaling is the existence of “universality” in which only a small number of restricted values of b can exist and the values depend only on the symmetry of the system but not on the materials and detailed interactions. The symmetry of the system is dictated by surface processes such as noise, surface diffusion, and shadowing. The classification of the universality classes of the roughness evolution of growth front has become one of the main focuses of many experimentalists and theorists.

Lu showed that in many growth processes such as sputter deposition and chemical vapor deposition, the experimentally measured growth exponent give a wide range of values that cannot be explained by existing classes of universality models. The wide range of growth exponent values means the existence of diverse roughness possibilities. It is believed that these rich possibilities are due to the competition between the shadowing effect and re-emission effect. The shadowing often occurs during growth of most common deposition processes such as sputter deposition and chemical vapor deposition. The re-emission mechanism is a result of a non-unity sticking coefficient when the atom or molecule strikes the surface during growth. The atom actually re-emits and bounces around before it settles on a surface site. It is well known from the literature that the sticking coefficient in many surface growth processes is not unity. We argue that shadowing and re-emission compete during growth and give rise to a growth exponent depending on the value of the sticking coefficient. Shadowing tends to roughen the surface and re-emission tends to smoothen it. A dynamical equation can be constructed to include both shadowing and re-emission effects. Since the sticking coefficient is materials and incident flux energy dependent, the growth exponent b can have any value and therefore is “non-universal”.

In the case of etching such as plasma etching, the situation reverses. The shadowing tends to smoothen the surface while the re-emission tends to roughen it. Nevertheless, they still compete and may generate a diverse etch front morphologies. A similar dynamical equation can be written to describe this case. In the case of small sticking coefficient, b value can be close to 1 and the surface is very rough.

Sunil Sinha’s presentation took a somewhat different angle, focusing on x-ray and neutron scattering to reveal the nature of surfaces. He described using specular reflectivity in which laterally average density profiles normal to the surface are measured to understand surface roughness. In addition to structural roughness, he examined magnetic roughness, essentially the orientation of magnetic domains. These two properties do not necessarily map to each other, so both interfaces need to be considered, and separate structural and magnetic roughness terms can be introduced. He covered recent work related to exchange bias phenomenon (in which the hysteresis curve is shifted from zero). Interfacial spin structure is a key to understanding this exchange bias. Sinha described how measuring reflectivity using resonance x-ray scattering can be used as a sensitive technique to determine quantitatively the depth dependent magnetic density. In the case of the Co/FeF 2 system it was found that the interface coupling is antiferromagnetic. While pinned and rotating moments exist for Fe, the interface mostly contains rotating moments while the bulk contains pinned moments (found by neutron scattering). The exchange bias is due to exchange interaction between pinned Fe and rotating moments.

D6.18
A New Crystalline to Crystalline Phase Change Memory Cell Using (Ge₁Sb₂Te₄)_0.8(Sn₁Bi₂Te₄)_0.2 alloy. Dong-ho Ahn¹, D.H. Kang², H.S. Kwon¹, M.H. Kwon¹, H.M. Kim¹, T.Y. Lee¹, T.G. Kim², K.S. Lee², T.S. Lee², I.H. Kim², W.M. Kim², B. Cheong² and K.B. Kim¹; ¹Materials and Science Engeneering, Seoul National University, Seoul, South Korea; ²Thin Film Materials Research Center, Korea Institute of Science and Technology, Seoul, South Korea.

O10.13
Mapping of Local Electronic Properties and Spatially Resolved Magnetoresistance of Nanostructured CMR Thin Films by Scanning Tunneling Microscope. Sohini Kar¹, Barnali Ghosh^1,2, Loveleen K. Brar¹, Mandar A. Paranjape³ and A. K. Raychaudhuri^1,2; ¹Department of Physics, Indian Institute of Science, Bangalore, Karnataka, India; ²S. N. Bose National Centre for Basic Sciences, Kolkata, West Bengal, India; ³Department of Physics, Boston College, Boston, Massachusetts.

R9.9
Experimental and Numerical Analysis of the Interaction between Surface Roughness, Capillarity and Adhesion in MEMS. Frank W. DelRio^1,2, Maarten P. de Boer¹ and Martin L. Dunn²; ¹Reliability Physics Department, Sandia National Laboratories, Albuquerque, New Mexico; ²Department of Mechanical Engineering, University of Colorado, Boulder, Colorado.

GG10.20
Actively Controlled Self-Assembly of Colloidal Crystals by Electrocapillary Effect. Chun-Wen Kuo, Jau-Ye Shiu and Peilin Chen; Research Center for Applied Sciences, Academia Sinica, Taipei, Taiwan.

Jim Daughton (NVE Corp.) presented the first symposium X talk on magnetic spin devices. Giant magnetoresistance (GMR) was discovered in 1988 and this began a period of intense research into the dependence of electron conduction on their spins in numerous materials and device configurations. Daughton described several of these new devices. Various magnetic sensors, including read heads for hard drives, have applied GMR materials in products by using GMR "spin valves" and GMR multilayers. New terms, such as synthetic antiferromagnet (SAF), nano-oxide layer (NOL), and CPP (current perpendicular to the plane) devices, were coined to describe discoveries that improved device operations. Initially, magnetic nonvolatile memory using GMR materials were conceived, but memory developments in the past several years have concentrated on magnetic tunnel junctions (MTJs) because of higher signal levels. Magnetoresistive random access memory (MRAM) is very close to becoming available commercially. MRAM has the potential advantages of high density, high speed, nonvolatility, and write cycle durability. Current MRAM research is focused on achieving very high density with reasonably low write currents in order to be competitive with other solid state technologies. Daughton concluded by mentioning several very recent advances including very high tunneling magnetoresistance and spin momentum transfer. He also mentioned that the Spins in Semiconductors (SPINS) program has just ended but its full impact has not been felt yet with possible advances in ferromagnetic semiconductors, light-induced spin, LED sensing and ferromagnetic injection.

The second symposium X talk was given by Omar Knio for Timothy Weihs (both from Johns

Hopkins Univ. and Reactive Nanotechnologies), who could not be present. Knio gave a brief introduction to reactive foil technology. Multilayer foils that react exothermically are a new class of nanostructured materials that can be used to solder or braze components together. The multilayer foils (NanoFoils^TM) range in thickness from 20 to 200 micrometers, and they contain hundreds of nanoscale layers that alternate between materials with large heats of mixing, such as Al and Ni. By inserting a free-standing foil between two solder (or brazed) layers and two components, heat generated by the reaction of the foil melts the solder and consequently bonds the components. The joining process can be completed in less than one second, in air or in vacuum. The use of reactive foils as a local heat source eliminates the need for torches, furnaces, or lasers, speeds soldering and brazing processes, and dramatically reduces the total heat that is needed. Thus, temperature-sensitive components, and metals and ceramics can be joined without thermal damage.The development of reactive foils from concept to commercialization was described, and examples of nanoengineering the temperatures, velocities, heats and ignition of the reactions were presented. The development process included significant modeling and computations. Knio described some initial applications of the process including bonding heat sinks on chips, mounting of connectors on PCBs and armor mounting for defense applications. The presentation concluded with a description of some of the challenges academic researchers face in transitioning new materials to the marketplace.

Symposium B
Sandwiched between the domains of electronics and photonics, the terahertz (THz) regime of the electromagnetic spectrum has traditionally lacked mature technologies for generation, mixing, and detection. Yet THz has important applications, from the detection of chemical and biological agents to imaging and telecommunication uses. Addressing this gap, John Reno (Sandia National Labs) presented results from his group in developing THz quantum cascade lasers (QCLs) in symposium B. Using a resonant tunneling LO-phonon scattering technique for lower-level depopulation and a novel double-sided metal-metal waveguide for transverse confinement, Reno’s QCLs have achieved lasing at milliwatt powers as low as 2.1 THz (141 mm) at a pulsed operating temperature of 137K. His group is currently working to reduce the lasing threshold currents and increase the operating range toward room temperature.

Bloch oscillations and Zener tunneling are well-characterized phenomena for electrons in solid-state systems with an electric bias field. Also in symposium B, Lorenzo Pavesi (Univ. Trento, Italy) reported the first observations of these effects in photonic systems. Using a porous silicon optical superlattice consisting of 10 coupled microcavities, Dr. Pavesi’s group imposed an effective “bias field” for photons in the superlattice by introducing an index of refraction gradient along the cavities, and hence an optical thickness gradient. Optical pulses traveling through these biased superlattices were observed to break into pulse trains whose period depended on the strength of the “bias field” (index of refraction gradient) – the optical analog of Bloch oscillations. For a narrow range of “bias fields” the group also observed Zener tunneling of photons between adjacent momentum bands, as evidenced by strongly enhanced transmission in optical superlattice samples with the correct gradient. The discoveries may lead to new applications in photonic engineering, including devices for photonic circuits.

Symposium Y
In symposium Y, Mark Greene presented recent results of interdisciplinary studies of characterization of DNA properties using a clever combination of atomic force microscopy, picture analysis, and theoretical worm-like chain modeling. The scientists are interested in investigating the behavior of bare DNA molecules which are normally surrounded by histone proteins in the cell nucleus. The analysis method is based on utilizing AFM to generate a series of trajectory snapshots of the configuration of the DNA molecules. Picture analysis methods used to perform contour tracking of the molecules are used to extract information about the trajectories. Greene and his colleagues are particularly interested in determining the contour length as well as how the molecules bend and deform. This data can be used to extract parameters that allow the description the molecules such as elastic rods near equilibrium modeled as worm-like chains. Parameters for such model chains are obtained using parameter fitting to experimental results analyzed by the picture analysis methods. Based on these methods, the persistence length of the DNA molecule is found to be about 62 nm, which is in reasonable agreement with previous research results for molecules of the length investigated. The properties of the bare DNA stand in significant contrast to the structure and properties of DNA bound to histones, underscoring the influence of proteins to deform DNA by electrostatic means. The new analysis procedure described in Greene’s talk is an interesting and promising example of a multi-scale hierarchical modeling scheme that allows to couple experimental data with theoretical modeling. The group is currently working on correlating the data with biological function. This could lead to potentially very important contributions in understanding the relationship of the mechanical properties of DNA and its biological function.

Also in symposium Y, an interesting talk discussing mechanical properties of biological adhesion systems was presented by Nicholas Glassmaker from Lehigh University. He discussed how Geckos (e.g. gekko gecko) manage to adhere to different types of surfaces, and pointed out that Geckos have very fine hair-like structures that play an important role in their amazing properties. Glassmaker pointed out that fibrillar structures as observed in the feet of Geckos are common to a large variety of different biological adhesive structures. Whereas some animals use suction type adhesion systems, previous researchers have shown that Geckos do not require suction mechanisms, nor covalent bonding, nor electrostatic force or any capillary effects. The attachment of Geckos to surfaces is possible solely through van der Waals forces. Despite these very weak interaction forces, Geckos are among the best adherent animals. The eventual goal of the researchers is designing new “fibrillar adhesive structures” similar to those used by Geckos which should have similar superior properties. Such structures, in addition of maximizing adhesive interfacial compliance, should maximize interfacial toughness and interfacial strength. “Additional important issues are to avoid collapse or condensation of adjacent fibrils, and avoid fibrillar buckling”, says Glassmaker. Finally, he showed results about how the conclusions derived from analyzing the attachment systems of Geckos may be used in creating new materials. This talk represented an interesting example of how biological concepts can be used to develop new materials. The entire presentation is available online at http://www.lehigh.edu/~njg204/mrs_dec_2004.htm

Symposium Z
In symposium Z, a contributed talk by Sherman from New York University focused on DNA-based “biped” molecular motors that allow forward and backward motion to solve materials transport problems. The biped robot is completely made out of DNA, with flexible linker molecules connecting its “feet”. Monitoring is achieved by attaching psoralen molecules. These are small molecules that can intercalate between bases. Under UV irradiation they covalently bond thymines in their neighborhood, and this allows detection of which feet are set in place (in contact) or not (no bonding). He showed a schematic representation of how progression is achieved via a completely different mechanism than kinesin. The motion of the “bipeds” is much slower than that of kinesin, however, and this system only took one step per hour, though it could likely go several orders of magnitude faster. Different features of how these systems are synthesized and how they can be utilized were discussed. For instance, branch junctions can be built by sequence programming that specify 3, 4 or more armed junctions. Possible applications of these techniques include computational systems, building nano-assembly-lines, as well as molecular weaving, braiding and threading. They provide an interesting alternative to kinesin-type molecular motors.

Henry Hess from the University of Washington in Seattle gave an invited talk in symposium Z that covered recent progress in utilizing biomolecular motors as engines for nanoscale transport and assembly. Specific focus was on kinesin proteins that are used as molecular motors and transport agents. This particular molecular motor hydrolyses ATP leading to a conformational change that pushes the whole molecule forward, a maneuver which is repeated up to about 100 times per second. The main question of Hess’s research was to find out what are good strategies for transporting matter at various scales? Whereas diffusion is very efficient over short distances, fluid pressure driven fluid flow is effective over macroscopic distances. In contrast, the speaker made a point that active transport by motor molecules such as kinesin is highly effective in the mesoscopic regime between these two extremes. The research objective of Hess’s group over the last few years focused on finding solutions to build nanoscale “shuttle” systems that may transport nanoscale materials and molecules over such intermediate distances. This may solve critical transport needs in nanoscale bio-inspired technologies. One aspect of his research was to develop methods that allow guiding of these motors based on photolithography, representing a smart combination of surface chemistry and surface topology. This method allows creating particular patterns and complex track networks in which surface-bound kinesin molecules propel shuttles consisting of functionalized microtubules. A highly interesting point he made that biomolecular motors could be used to surface imaging: This technique is based on the fact that the shuttles do not (or hardly) climb up surface extrusions larger than 200 nanometers. Measuring the distribution of microtubule shuttles over long time scales allows drawing conclusions on the surface morphology. Hess emphasized that this could be potentially extended to measure other surface properties, such as pH distributions, as well.

Another application is the integration of active transport into biosensors based on geometrically focused target-receptor concentration or aggregation at a specific point for more straightforward sensing. Motor molecules could also be used to study the strength of receptor-ligand bonds and represents an appealing implementation of a piconewton force meter. In the last part of his talk, he outlined several links to materials science. For instance, molecular motors on microtubules could be used to investigate their mechanical properties, such as fracture and elasticity, as well as self assembly driven by biomolecular motors. He also mentioned some recent studies on the lifetime of bio-nanodevices. In summary, these impressive results and exciting novel techniques could help building lab-on-a-chip nano-bio technologies and help to characterize small-scale materials.

Symposium FF
Symposium FF featured an invited talk by Younan Xia from the University of Washington at Seattle, who noted that while much research in nanoscale science focuses on the size of nanoparticles, the shape of nanoparticles can also significantly impact their properties. Using gold as an example, he pointed out that due to a splitting in the surface plasmon resonance peak on changing the shape of gold nanoparticles, the colors of different shapes of gold nanoparticles can vary significantly. Research in Xia’s laboratories has focused on the shape controlled synthesis of metal nanostructures. Xia outlined different strategies for gaining shape control. The use of capping agents which bind selectively to specific facets of growing nanostructures allows the growth of silver nanowires. Xia further demonstrated that controlling the growth kinetics in the polyol reduction of a platinum precursor led to the growth of platinum rods and wires. Recent research in Xia’s group has focused on the galvanic replacement of gold by silver resulting in the formation of interesting structures such as Ag/Au multi-walled nanotubes and nanorattles.

Symposium GG
Symposium GG has focused on strategies for the assembly of nanoscale building blocks into higher order architectures. In an invited talk at the symposium, Orlin D. Velev (North Carolina State Univ.) outlined strategies for assembling microparticles, nanoparticles, and living cells in one or two dimensions using alternating current (AC) dielectrophoresis. Particle chaining forces and positive dielectrophoresis led to the assembly of latex particles in a single crystalline domain, with only six first-order spots in its laser diffraction pattern. Metallic nanoparticles placed in the AC field were driven by the electric field gradient to form microwires. Velev and his coworkers are able to vary experimental conditions such as frequency and solvent viscosity to control branching in these structures. Velev further demonstrated the use of AC fields to direct the assembly of live yeast cells in composites with latex particles. 1D and 2D assemblies can be made by use of the induced dipoles generated in the cells when placed in an AC field. These cell-particle assemblies are expected to be useful as biosensors, bioelectronic circuits, as biocompatible coatings, and in microsurgery.

Symposium HH
As silicon based microelectronics nears inevitable scaling roadblocks, there has been much interest in the use of carbon nanotubes as transistors and interconnects. Delivering an invited talk at Symposium HH, Georg Duesberg from Infineon Technologies, Germany outlined a few schemes for the integration of carbon nanotubes into microelectronics. Duesberg discussed the lithographically defined vertical growth of MWNTs, which are able to carry current densities of up to 5×108 A/cm2 and can potentially be used as interconnects. Further work at Infineon has been directed at shrinking the lateral dimensions of nanotube devices. Duesberg reported the fabrication of ‘the world’s smallest nanotube field effect transistor (FET)’ with a channel length smaller than 20 nm. These devices have an on/off ratio up to 106 and are able to switch ultrahigh currents >15 μA/tube. To overcome the various challenges in nanotube electronics such as reliability and reproducibility, Infineon as well as others are working on the vertical carbon nanotube concept, where vertically grown parallel arrays of nanotubes can be grown controllably between desired heights of the source and drain. Infineon has recently developed a nanotube based power transistor capable of operating with macroscopic loads.

The long wait for commercial carbon nanotube based electronic devices is almost over according to Jean-Christophe Gabriel from Nanomix Inc., a California based start up that expects to be marketing single-walled carbon nanotube (SWNT)-based hydrogen sensors by early 2005. Delivering an invited talk at Symposium HH, Gabriel discussed the tremendous versatility of sensors based on carbon nanotube field effect transistors, which he compared to nerve cells capable of sensing different stimuli. While single nanotube transistors are too fragile to be useful over long periods of time, networks and arrays of nanotubes make robust sensors, while also giving high signal to noise ratios with low power consumption therefore enabling wireless application. The tremendous sensitivity of the transport properties of SWNT devices to small environmental changes is ideal for sensing applications but also requires that nanotubes be functionalized to be selective and specific for certain analytes. Metal functionalized nanotubes make for excellent hydrogen sensors capable of detecting levels of hydrogen with great sensitivity. Other applications being explored at Nanomix include a polymer functionalized SWNT sensor for CO2 and biofunctionalized nanotube sensors for biomolecule detection in liquid environments.

Symposium MM
Rare-earth-doped optical fiber lasers can provide very high CW powers and have also become attractive as optical pulse amplifiers. However, the high powers and small fiber core diameters in these systems can lead to severe nonlinear distortions. One solution, explored by A. Liem’s (Univ. Jena) group and reported in symposium MM, is to use micro-structured optical fibers. Parameter tuning of the microstructure geometry allows single-mode operation while greatly reducing the nonlinear complications. Using such a system, Liem has demonstrated a 260W CW laser with a 4-meter fiber with a single transverse mode. The group is pursuing a strategy of replacing all optical elements for pulse generation and control with fiber-based systems that are compact and can be easily integrated.

Early Wednesday morning, materials scientists gathered for a panel discussion on Workforce Issues Facing Women in Academia: Developing a Career and a Lifestyle. This was featured in the Women is MS&E Breakfast sponsored by the MRS Public Outreach committee, Aldrich Chemical Co., and Veeco Instruments. In a question/answer set-up, the panelists, Gillian Bond (New Mexico Tech), Lorna Gibson (MIT), Ingrid St. Omer (Univ. of Kentucky), and Linda Vanasupa (CalPoly) described their experiences handling career issues with the personal backdrop of dual-career households, households with children, and as minorities in a department or research program. Panelist Larry Pope (Sandia National Laboratories) provided some insight from a hiring point-of-view and the moderator, Sandy Yulke (Yale) offered career options in academia other than teaching and research. Through the various experiences described among the panelists and the attendees, the main criteria for success seem to rely on mutual support for everyone's career within the family, a geographical location in which the region offers many resources for career advancement, and flexibility in career decisions so as to match the career needs with the right "boss." Above all, when individuals perform well, they will find institutions that want them.