REMRSEC Research Highlightsremrsec.mines.edu/documents/highlights2011/remrsec...solar energy, hence...

REMRSEC Research Highlights

The Renewable Energy Materials Research Science and Engineering Center (REMRSEC) has made substantial progress in its research mission of identifying, launching and advancing innovative research directions in materials for renewable energy, and in its human resource mission of educating the next generation of renewable energy professionals, reaching out to students and the general community, and promoting diversity among faculty, research associates, staff, students, and future students. The Center has exploited the vibrant energy vision of the Colorado School of Mines (CSM), the extensive energy resources of the nearby National Renewable Energy Laboratory (NREL), and the growing wave of interest in energy as a national challenge to advance the global energy agenda. The Center has integrated forefront basic research with education and outreach, a powerful, timely and complementary mix. It has identified two promising and rich research directions, silicon nanostructures for next generation photovoltaics, and next generation ionic conducting membranes for battery, fuel cell and other applications. These themes effectively combine theory and experiment to drive new research frontiers. The Center’s seed program has been especially successful in exploring high-risk, high-payoff innovative research that can be integrated within the Center’s Interdisciplinary Research Groups (IRGs) or translated to independent funding. Four of the Center’s IRG or seed projects have leveraged additional funding, reflecting the vibrancy and fullness of its research agenda. The Facilities program has undergone a dramatic increase in breadth and depth, with significant advances in its Characterization Laboratory, Semiconductor Processing Laboratory, Synthesis Laboratory, Clean Room, and associated Atom Probe Development Laboratory. The new capabilities provided by these laboratories are a major boost to Center programs. The level of the technical staff of the Center, CSM and NREL has been raised with two Center hires that are joint with NREL, establishing a paradigm for leveraging cooperation and diversity. In three short years, the Center converted a vision for renewable energy into a vibrant and successful organization that engages NREL, CSM, the student body and the public in addressing a national priority, developing new materials for sustainable energy for the future.

Below are highlights from the research groups.

Revised August 22, 2012

2 REMRSEC Research Highlights

Next Generation Photovoltaics Research

Silane Passivation of Si Quantum DotsI. E. Anderson, R. A. Shircliff, C. Macauley, D. K. Smith, B. G. Lee, S. Agarwal, P. Stradins, and R. T. Collins

Exposing unprotected (or H passivated) Si quantum dots to air results in oxidization of the dots. This creates surface states which act as recombination centers and creates an insulating shell that can limit charge transport. It also changes the optical properties of the dot as the silicon core shrinks and emission energy increases. In turn, there are changes in quantum efficiency. For these reasons, considerable research has been directed at finding effective ways to passivate the surfaces of silicon dots (the same can actually be said about most semiconducting quantum dot systems). Passivation through surface functionalization with organic ligands is of particular interest since such approaches have been shown to limit oxidation of the dots while allowing the dots to enter colloidal suspension, enabling subsequent solution processing. For dots synthesized through colloidal processes, attachment of a surface ligand often happens naturally during synthesis. For dots prepared in other ways, such as gas phase synthesis, organic passivation is more complex and often requires breaking up agglomerated collection of dots before chemical processing to result in a stable colloidal solution. In this study we have demonstrated a novel silanization approach to passivation of plasma synthesized silicon quantum dots. Prior studies have shown silanization is an effective passivation scheme for silicon surfaces. These studies, however, typically used silanes with multiple reactive sites at the end of the molecule that attaches to the silicon (e.g. trichlorosilanes). While this results in a robust attachment and stable surface, it allows a cross-linked network of silanes to form, creating thick organic multilayers on the surface that are not desirable for subsequent use of the dots in, for example, device applications where transport of charge or energy through the passivating layer is important. We chose a silane with only a single point of attachment, dodecyldimethylchlorosilane (DDDMCS) which is a 12 chain alkyl group terminated by a silicon atom with two inactive methyl groups and a single active Cl attachment point. The left figure shows a schematic of a silicon dot with DDDMCS attachment.

We find the dots remain in stable, colloidal solutions for over two months in air, even with only a single molecular layer of silane ligand protecting the dot. In addition, the emission energy does not change in the same time period, indicating the dots are not oxidizing, since oxidation would shrink the dot core and increase emission energy. Unpassivated dots show substantial changes in emission energy over much shorter time periods. Silanized dots also exhibit no observable surface defects in ESR measurements. As part of the silanization process, the dots are etched in a nitric acid solution to create an OH terminated surface. By controlling the length of the etching process before silianization, dot size, and hence emission energy, can be tuned. The net result is stable, passivated, colliodal solutions of Si quantum dots with long term stability and tunable emission from the IR to the green as shown in the graph on the right of the figure.

3REMRSEC Research Highlights

Hot Carrier Transport in Nanocrystalline SiliconK. G. Kiriluk, J. E. Fields, B. J. Simonds, Y. P. Pai, P. L. Miller, T. Su, B. Yan, J. Yang, S. Guha, A. Madan, S. E. Shaheen, P. C. Taylor, and R. T. Collins

When above band gap light is absorbed by a semiconducting material, carriers typically relax to the band edges by giving off the excess energy in the form heat through phonon emission. This is a major source of loss in the conversion of solar energy to electricity. Hot carrier collection is a third generation PV concept in which carriers transfer from the absorber to electrode materials before losing this energy to heat. While hot carrier collection has been widely discussed, there are few reports of the actual transfer of hot carriers from an absorber to a collector and these are controversial.Scientists within REMRSEC led by Craig Taylor and Reuben Collins in collaboration with with industrial collaborators at United Solar Ovonic and MVSystems have observed definitive evidence of hot carrier transfer in an unlikely place, from amorphous to crystalline regions in hydrogenated nanocrystalline silicon (nc-Si:H). Nc-Si:H is a blend of silicon nanocrystals in an amorphous matrix, and is one of the few nanostructured materials to actually succeed as a PV technology. Using a combination of photoluminescence quenching and light assisted electron spin resonance techniques they demonstrated that above about 40% crystalline fraction, carriers created in amorphous regions rapidly transfer to the nanocrystals before they can relax to the mobility edge of the amorphous matrix. Transient photoconductivity experiments carried out by a REMRSEC graduate student using facilities in Matt Beard’s lab (NREL REMRSEC participant) directly observed this transfer. The results together provide unambiguous evidence of hot carrier transfer, explain the increased photostability of nanocrystalline silicon relative to amorphous silicon (a long standing open question), and demonstrate that nc-Si:H functions as a “bulk heterojunction style” blend. More importantly, this result establishes the possibility of using a wide range of nanostructured amorphous matrices to dramatically increase the efficiencies of solar cells. Amorphous materials had not previously been considered because of low mobilities hence this opens up the possibility of a new paradigm for hot carrier devices. Conventional nc-Si:H, where nanocrystals form spontaneously and films are optimized empirically, is not the optimal system to use in harnessing hot carrier effects. Using the basic science results from this study, REMRSEC members Collins, Lusk, Stradins, and Taylor successfully competed for a DOE SunShot Transformational PV grant to develop engineered nanocrystalline silicon by integrating the plasma-based silicon quantum dot process developed by the center with amorphous Si film formation. This will allow films that incorporate quantum confined Si nanocrystals with engineered surface, size, and distribution to be fabricated, and is an example of basic science from the Center transitioning to device and application oriented directions.

Size Dependence of Multi-Exciton GenerationZ. Lin, A. Franceschetti, M.T. Lusk

Multi-Exciton Generation or MEG is an inverse Auger process in which an electron-hole pair with an energy more than twice the band gap relaxes to the exciton’s ground state by creating a second electron-hole pair rather than dissipating the excess energy as heat. It is a carrier multiplication process which can harness energy in solar cells normally lost to heat. It raises the theoretical efficiency limit of a solar cell operating under standard conditions by roughly a half from 31% to 45%. If such a factional change could be realized in real cells, it would have a major impact on the cost of solar energy, hence this third generation PV process is under active fundamental investigation.A major controversy has, however, arisen around the efficiency of MEG. MEG actually occurs in bulk


materials but with low efficiency. Here it is called impact ionization. MEG was, however, predicted to increase substantially in efficiency in quantum confined nanostructures because of effects such as a phonon bottleneck (lower thermal relaxation rate) and increased spatial confinement of the exciton (enhanced Auger matrix elements). This set of a flurry of research directed at characterizing MEG in quantum dots, frequently using II-VI and IV-VI materials like CdSe and PbSe. Initial studies at LANL and NREL detected MEG in quantum dots, but subsequent studies by other groups suggested the efficiency of the process is comparable to or less than the efficiency in the bulk. This was a “hot” topic at technical meetings.

We have explored the efficiency of MEG generation in CdSe quantum dots using an atomistic pseudopotential approach and first-order perturbation theory. We showed that this controversy revolves around how you scale the results relative to the band gap. The multiplication rate of a photogenerated electron-hole pair decreases with dot size for a given absolute photon energy. However, if the photon energy is rescaled by the volume-dependent optical gap, which is also changing with dot size, then smaller dots exhibit an enhancement in carrier multiplication rate for a given relative photon energy. Scaling to the gap is the appropriate approach since MEG efficiency is proportional to the slope of the quantum yield versus the relative photon energy (above the MEG threshold). REMRSEC experts at NREL, and particularly Matt Beard, provided considerable advice throughout this project, and Matt Beard’s team has subsequently demonstrated working quantum dot solar cells with MEG enhanced quantum efficiencies exceeding 100% (Science, 334, 2011).Because of the controversy surrounding MEG, our modeling work received considerable attention. The work led to an interview of Mark Lusk by Colorado Public Radio and was highlighted in an NSF press release entitled, “Size matters: Smaller Particles Could Make Solar Panels More Efficient” as well as within a CSM press release. The press releases went viral with coverage by several hundred websites around the world.

Initial Oxidation of SiliconHuashan Li, Zhigang Wu, and Mark T. Lusk

Most quantum dot systems exhibit unwanted changes in properties when exposed to air, often a result of oxidation. This leads to devices built and tested in glove boxes and considerable work directed at understanding passivation. With Si-based dots, oxidation is a serious issue creating surface barriers, defects, and changes in optoelectronic properties that become increasingly significant as the size of the Si core decreases. Given the importance of controlling oxidation, we are applying first principles computational techniques to gain new insights into what is, in fact, an old problem.

It is well known that the oxidation rate on the H-terminated Si surface is much lower than on the bare surface, however, the corresponding mechanism and detailed dissociation processes remain controversial. We have carried out transition state analyses within a density functional theory setting to explain and quantify the distinctly different ways in which hydrogen and methyl terminations serve to protect silicon surfaces from the earliest onset of oxidation.

In particular, the measured effective activation energies for the initial stage oxidation of H-passivated Si surfaces are around 1.6-1.7 eV, but our first-principles calculations demonstrate the existence of barrierless oxidation dissociation paths on these surfaces for the initial oxidation event. However, the measured effective oxidation barrier is not just the activation energy for the very beginning of O2 dissociation and inclusion in the lattice, which we find to be near zero. Instead, it includes lateral O


hopping and a rapidly increasing O2 dissociation barrier as the O coverage increases. We find that the dissociation barrier of O2 molecules, in the presence of nearby O atoms that previously were incorporated, can be as high as 1.24 eV and is expected to be even higher as O coverage increases. In addition, the calculated lateral O hopping barrier is more than 2 eV, e.g., 2.48 eV for O atoms on H-Si(111). Therefore, it is the combination of the initial barrierless dissociation, a high lateral hopping barrier, and a rising dissociation barrier with O coverage that prevents rapid oxidation on the H-terminated surface. This is a new understanding of the oxidation of H terminated silicon surfaces.

On the other hand, methyl termination offers an additional level of protection because oxygen cannot directly oxidize the Si surface. It must first oxidize the methyl group and then hop from this group to the Si. This is a three-step process with significant energy barriers, approaching 3 eV. The first step is adsorption of O2 into C-H bonds to form a C-O-O-H intermediate followed by decomposition of C-O-O-H into C-O-H and C=O intermediates; and, finally, hopping of oxygen atoms from ligands to Si-Si bonds underneath.

Spectral Microscopy Characterization of Individual Quantum DotsEric Chandler, Chip Durfee, Jeff Squier

Spectroscopy plays a key role in multiphoton microscopy, augmenting the spatial information obtained via imaging with information about local chemical environments. Quantum dots, which are of increasing interest as laser sources, biological markers to replace dyes, and components of high efficiency solar cells, exhibit changes in their fluorescence spectrum when a second carrier, known as a biexciton, is promoted to the excited state . These shifts and additional peaks are on the order of several nanometers and are very weak, requiring high spectral resolution, high sensitivity, and narrow emission bandwidth to observe. These characteristics must be measured on single quantum dots, so as to not average out the spectral and temporal properties of the fluorescence. More easily observed are the spectral shifts due to different degrees of quantum confinement in quantum dots. As confinement increases with a decrease in dot size, the bandgap of the dot will increase from that of the bulk.

We have implemented a simple prism-based spectrometer fabricated with “off the shelf” optics specifically for multiphoton microscopes that has no slit, requires no filtering of the output, and yields a spectral resolution that varies between 0.3 nm and 2.2 nm across the detector. Unlike traditional grating-based spectrometers, high spectral resolution is not dictated by a slit, but rather by the dispersion of the prism and the beam size. Thus, our spectrometer employs the full acceptance of a high-numerical aperture objective without the loss associated with focusing through a slit.

We characterize the performance of this spectrometer by examining single CdSe quantum dots. Detecting emissions from single emitters tests the sensitivity limit – a function of detector gain and system throughput. The emission exhibits amplitude modulation known as “blinking”, which is thought to be associated with dot charging associated with the excitation and relaxation cycle. The spectrum in the slide was acquired with below band gap light. Excitation involves a non linear two-photon process. The spectrum shows a strong dependence on the polarization direction of the incident exciting light. This implies the existence of anisotropy in the shape, surface defect structure, or capping groups, which leads to differences in the character of the excited state under the two conditions.


Now that the system is functional and has been tested on prototypical CdSe quantum dots, work is focused on silicon nanostructures. These have been passivated with different capping ligands and the goal of the study is to gain insights into the effect of ligand on defect state and carrier dynamics.

Metal Free Silicon NanowiresSomilkumar Rathi, Joe Beach, Paul Stradins, Craig Taylor, and Reuben Collins

Semiconductor nanowires are of great current interest as photovoltaic materials. They offer the potential for size tunable properties and quantum mechanically modified carrier dynamics through two dimensional confinement, while simultaneously providing a route for carrier transport and collection in the third direction. Even when wire diameters are too large to exhibit confinement, the wire topology enables novel device architectures to be considered. For example, there has been much recent attention to device designs in which nanowire arrays are optically thick and “trap light” while charge separation of photoexcited carriers can occur over a short radial distance perpendicular to the direction of the incident light. It has been suggested that this can mitigate the effects of impurities in wires. In general, however, nanowire devices do not exhibit high efficiencies and it is often the open circuit voltage which suffers, suggesting defect recombination as a likely culprit.

The most common synthesis techniques for Si nanowires use metal catalysts. Vapor-liquid-solid (VLS) growth, for example, involves chemical vapor deposition using a metal seeded process, and Au has been the metal catalyst of choice. Carrier lifetime studies by our team, however, show that metal contamination arising from the seed can have a dramatic effect on carrier lifetime. Even with radial collection of carriers, these substantially reduced lifetimes can limit nanowire solar cell performance. Developing alternative catalysts is essential. Reports of wire growth using lower Si solubility metals such as Cu and Pt and using metals like Al and In which are more likely to dope the wires than create deep defects have been reported. In this project we have taken a different approach using the column IV element Sn. Sn is isovalent with Si and should have less effect on minority carrier lifetime than gold while not doping the Si. In addition, Sn solubility in Si is extremely low. Sn also has a low melting point allowing VLS growth to occur at lower temperatures.

We have demonstrated plasma enhanced chemical vapor deposition (PECVD) growth of silicon nanowires at 400°C using Sn seeds as shown in the SEM images. A significant finding was that axial growth of the wires slowed and finally terminated. X-ray energy dispersive spectrometry studies performed in a TEM showed that while Sn seeds were present at the ends of the wire early in the growth cycle, by the time growth terminated the Sn was no longer present. We were able to show that the Sn seed is being “etched” and removed by the hydrogen plasma, creating self terminating wires which are metal free (cartoon schematic). This opens the possibility of creating high quality, metal free wire arrays by beginning growth using Sn seeds with a CVD process, followed at the desired growth time by an in-situ hydrogen plasma etch to remove the seeds. The project was a collaboration with Joan Redwing who is a member of Penn State’s MRSEC. A paper in the Journal of Physical Chemistry C describing the work in now available on-line.


Exciton Transport Between Quantum DotsZhibin Lin, Alberto Franceschetti, and Mark T. Lusk

Solar energy can be collected by silicon atoms (small tan spheres) assembled into quantum dots (large spheres) that are then functionalized with ligands to shield them from oxidation and/or change their electronic properties. The dots shown are comprised of thousands of silicon atoms and have diameters on the order of four nanometers. A given absorbed photon from the sun generates an exciton, a coupled electron-hole pair depicted as diffuse, adjacent green and orange regions. This quasi-particle is initially confined to a single quantum dot but can subsequently tunnel to neighboring dots until it reaches a collection center. There the electron and hole are separated, resulting in an electrical current. In the current study, we focus on very small dots (Si35) so that we can use a Bethe-Salpeter analysis to account for interactions between electrons and holes. Five different functionalizing ligands are considered.

The efficiency is calculated as k_ET/(k_ET + k_PL), where k_ET and k_PL are the exciton transfer rate and PL radiative rate, respectively. The PL radiative rate is the inverse of the PL lifetime which is calculated using Fermi’s golden rule with the oscillator strength obtained from GW/BSE calculations. Both k_ET and k_PL are thermally averaged over all excitonic states using a Boltzmann distribution at 300K. The results do not follow a simple trend associated with ligand electronegativity. Rather, the overlap between HOMO and LUMO orbitals, in the form of the oscillator strength, dictates which ligands give the highest transport rate.

Carrier Multiplication in Quantum DotsZhibin Lin, Alberto Franceschetti, and Mark T. Lusk Renewable Energy MRSEC

It has been proposed that quantum mechanical effects might be used to enhance the generation of more than one electron-hole pair from a single photon in semiconductor quantum dots. This would result in significant efficiency increases in next generation solar cells. While this kind of multi-exciton generation has been observed experimentally, there is considerable controversy over the efficiency of the effect in dots relative to bulk material. Using a semi-empirical approach to study CdSe dots, we have shown that the rate of multiple carrier generation increases as dot size decreases for photons of the same relative energy.

Silicon Nanowires Silicon Nanopartices for Solar ApplicationsSumit Agarwal, Bhavin Jariwala, Paul Stradins, Bejamin Lee, Joe Beach and Reuben CollinsRenewable Energy MRSEC

Silicon nanoparticles are promising new materials for photovoltaic applications that combine materials property tunability on the nanoscale with silicon’s established performance in photovoltaics. We have succeeded in synthesizing crystalline silicon nanoparticles in a continuous flow plasma reactor and established control over particle size. By carefully tuning the plasma parameters, we have synthesized particles with radial precision of a couple atomic layers and characterized them structurally and optically. Such tight size control is the first step toward assembly of nanoparticles into a device layer to produce silicon-based PV devices with tunable bandgaps.


Tin Seeded, PECVD Grown Silicon NanowiresSomilkumar Rathi, Joe Beach, Paul Stradins, Craig Taylor, and Reuben CollinsRenewable Energy MRSEC

Silicon nanowires are potentially transformative photovoltaic materials. Nanowire arrays are commonly synthesized using gold seeded vapor-liquid-solid (VLS) growth. Gold, however, can damage silicon’s electronic properties and growth temperatures are too high for low cost substrates. Here silicon nanowires were grown from benign tin seeds at much lower temperatures using plasma enhanced chemical vapor deposition (PECVD). Control of wire radial and transverse growth rates was demonstrated.

Multiphoton Characteristics Of Quantum DotsJeff Squier, Jeff Field, Eric Chandler, Chip DurfeeRenewable Energy MRSEC

Nonlinear femtosecond microscopy is being used to study the carrier dynamics of quantum dots - important future constituents in high-efficiency photovoltaics. The temporal fluorescence characteristics of CdSe/ZnS core/shell dots are quite unusual - they initially brighten with exposure to femtosecond laser light and this behavior is influenced by laser pulse shape. While traditional fluorophore emission intensity initially decays, optimizing the pulse shape significantly improves intensity as shown in the far right figure. Understanding the origin of these effects is important for applications extending from photovoltaics to bioimaging with fluorophores. The results of this work have been submitted for publication to Nature Methods.

A Hot-Carrier Relaxation Process - New Possibility For Improving Efficiencies Of Silicon-Based Solar Cells Craig Taylor, Reuben Collins And Arun Madan Renewable Energy MRSEC

A hot-carrier relaxation process has been discovered that may eventually be used to increase the electrical output voltage from a solar cell based primarily on nano-composite films of silicon. Using a technique called electron spin resonance, Center members Taylor and Collins of the Colorado School of Mines and Madan from MVSystems, Inc. have found that electrons and holes generated in amorphous silicon regions can transfer to the nanocrystalline regions before losing their excess energy to heat.

Morphology of Epitaxial Core-Shell Nanowires Hailong Wang, Moneesh Upmanyu, and Cristian V. CiobanuRenewable Energy MRSEC

Epitaxial core-shell nanowires are of great interest because they exhibit an impressive array of novel, tunable optoelectronic properties. When a lattice mismatched shell is grown on a


cylindrical core the wires do not always remain cylindrical (a), but can develop nanoscale surface modulations (b) that self- organize into epitaxial quantum dots (c). In a recent Nano Letters article, Wang, Upmanyu, and Ciobanu used an isotropic continuum model to demonstrate that geometric parameters such as core radius and shell thickness play a crucial role in determining whether or not the nanowires remain cylindrical (d). Additional support provided by the DOE Computational Materials Science Network and the NSF Nanoscale Science and Engineering Center at Northeastern University.

Advanced Membrane Research

Novel Ceramic/Organic IonomersGreg Schlichting, Andrew Herring

We have produced a novel zirconium vinyl phosphonate/vinyl phosphonic acid copolymer (VZP co-VPA) that exceeds the proton conductivity of all other phosphonic acid based polymers. In order to understand how the ions move on a molecular level, NMR was used to determine structure of the polymer and PFGSE NMR to elucidate the proto motion in the material. The ionomeric structure is illustrated in the first part of the figure below. The rearrangement of the Zr-O bonding allows for a structure to develop in the ionomer that encourages proton movement through the membrane via the proposed mechanism shown in above. Since this is structural diffusion of the protons, little to no water is needed in the system to allow for fairly high proton conductivity, c.a. 50 mS cm-1 at 50%RH. It has been found that at relative humidity <60%RH, l≤1 strongly suggesting a pure Grotthuss-like structural hopping mechanism.

Dynamic Measurements of Polymer ElectrolytesYuan Liu, Andrew Herring

The most popular PEMFC electrolytes are perfluorosulfonic acid (PFSA) based polymers, with Nafion™ serving as the benchmark. PFSAs contain Teflon-like backbones, which provide mechanical strength, and sulfonic acid side groups to provide charge sites for proton transport. The detailed morphology of PFSA membranes at the nanoscale is still in dispute, in part because of their sensitivity to environmental conditions. Herring and Liu have built unique instrumentation based on small angle X-ray scattering (SAXS) that is providing the first dynamic measurements of morphology evolution for PFSA membranes. These measurements are obtained using a custom built environmental chamber coupled to the high intensity synchrotron photon source at the Advanced Photon Source. The Figure provides an example displaying the evolution of morphology in response to changes in the relative humidity (RH). Through numerical fitting, we have obtained both qualitative and quantitative morphological information such as particle size, shape, separation distances and distribution, for both the hydrophilic ionic clusters and the hydrophobic polymer chain. In this example we see that the ionomer peak grows in intensity and shifts to low q with increasing RH, showing the plasticizing effect of water to facilitate the formation of the crystalline region. We have also investigated a series of novel ionomers to understand how side chain functionality impacts the ability of these materials to phase separate and assemble into proton conducting materials.


Novel Transport Mechanisms in Conducting CeramicsMichael Sanders, Robert Kee, Ryan O’Hayre

First, our team has discovered an unusual multi-species defect-transport coupling process occurring in ceramic materials when employed in gas permeation applications. We exploited this effect to enable first-of-a-kind demonstrations of counter-current and uphill transport in BZY-1%NiO due to the simultaneous mixed conduction of protons (OHO•), oxygen vacancies (V••), and electronic defects (electrons or holes) at elevated temperatures (~600˚C). Depending upon gas-phase partial pressures across the membrane, intrinsic coupling between defects enables the separation of oxygen, hydrogen or steam and, remarkably, can even force any one of these species to be transported against its concentration gradient (uphill diffusion). The first figure illustrates the crystal defect structure in the context of transporting oxygen and steam in opposite directions (counter-current) across the ceramic membrane, while the second figure envisions a potential application of this unique transport phenomenon for enhanced chemical reforming of methane to ethylene in a ceramic membrane reactor.

Advanced Synthesis of Proton Conducting CeramicsStefan Nikodemiski, Dan Clark, Jianhua Tong, Ryan O’Hayre

Yittria–doped barium zirconate (BZY) and barium cerate (BCY) are the perovskites that have been the focus of this work. The former exhibits high conductivity, while the latter offers high stability. Our team has explored the benefits of oxide-based additives to promote grain growth during synthesis. A comprehensive screening of 15 different oxide additives by our team has revealed that oxides with a +2 transition metal cation (e.g. NiO, ZnO, CuO, and CoO) dramatically enhance the sinterability of BZY and BCY based proton conducting perovskites. This strategy has produced electrolytes with increased density and reduced defects. This work has culminated in the scientific understanding and commercial development of a new synthesis methodology, solid-state reactive sintering (SSRS), which enables a 90% decrease in protonic-ceramic fabrication cost and complexity by harnessing the beneficial effects of these oxide additives. SSRS brings the commercialization of these materials closer to reality: Tong and O’Hayre have delineated the mechanisms associated with the NiO-based SSRS process, and our industrial partner (CoorsTek) is now adopting the NiO-based SSRS strategy for the production of YSZ, BZY, and BCY ceramics for fuel cell and ionic membrane applications.

Simulation of Proton Transport in PEM Fuel CellsSteve Tse, Andrew Herring

The complexity of polymer electrolytes has constrained theoretical attempts to model these systems. Classical molecular dynamics (MD) simulations cannot study proton transfer, while ab initio techniques are too expensive. We are using multistate empirical valence bond theory (MS-EVB) as a novel approach to study proton transfer within PFSA membranes. With MS-EVB, accurate calculation of the potential energy surface of proton transfer is enabled at time and length scales that cannot be achieved by any other methods. We are able to extract macroscopic transport properties such as diffusion constants and conductivity that may be tested by experimental measurements.

Examples of this effort are shown in the Figure, which shows an atomistic snapshot of the 3M PFSA membrane displaying phase segregation. The model is able to accurately estimate the density of the


membrane at different hydration levels, temperature, and pressure. The graphic shows about 4000 atoms in the simulation box. The most obvious observation is the phase separation between water (red and white balls) and the carbon backbone (the green atoms). Another observation is that the waters are also close to at least one sulfonate group (Yellow).

Poisson-Boltzmann Model of Nanoionic Composites Jason Fish, Chi-Ping Li, Joseph Fehribach, Colin Wolden, Ryan O’Hayre, Annette Bunge, and Christopher Goodyer

Ionic conductivity in nanocomposite electrolytes is examined through the use of numerical models. A rigorous description of the space charge layer and its impact on conductivity are developed for a composite system consisting of insulating spheres dispersed within an ion conducting material. Model simulations are performed to understand how the effective conductivity, which can exceed the conductivity of the bulk material, depends on the volume fraction, size, configuration, and particle size distribution of the nanoparticles in the bulk material. Several deliberately chosen regular particle configurations are used to establish the lower and upper bounds for conductivity enhancement. A simple cubic array of particles is demonstrated to provide a reasonable estimate for the behavior expected from a random distribution of particles. Finally, conductivity modulation is shown to be significant when the particle radius is comparable to or smaller than the thickness of the space charge layer.

Mesoporous, Nanoparticle-based Electrochromic Films Chi-ping Li, Robert Tenent, Anne Dillon, Colin Wolden

WO3 nanoparticles (NPs) in the size range 15 – 35 nm were fabricated using hot-wire chemical vapor deposition (HWCVD). The size and shape could be controlled by the oxidizing nature of HWCVD environment. These NPs were subsequently suspended in green solvents (water, alcohol), and used to produce mesoporous electrochromic films by ultrasonic spray deposition (USD). USD is a scalable fabrication technique that is conducted at atmospheric pressure. The resulting films have a mesoporous structure, retaining the primary NP. The high specific surface area facilitates ion insertion. Cyclic voltammetry performed in concert with optical transmission measurements showed that these films displayed record coloration efficiency for Li ions and fast switching kinetics.

Polymer/Nanoparticle FilmsMelissa Kern, Nathan Bade, Matt Liberatore and Steve Boyes

The most successful organic photovoltaic devices (OPVs) use a bulk heterojunction design. This is a nanostructured blend of a light absorbing organic (often a polymer) electron donor and an electron acceptor (often a fullerene). The blend is necessary because of the short diffusion length of optically excited excitons in the organic and the requirement that an exciton must reach an interface before de-exciting if it is to decompose into an electron and hole which can be collected. The morphology of the donor/acceptor blend is critical to charge generation and to carrier collection.

In designing materials for hybrid photovoltaic devices, the two most important factors to consider are then, efficient dissociation of generated excitons which requires intimate contact between the


donor polymer and the electron accepting inorganic nanoparticle, and a interconnected network of both donor and acceptor components to allow efficient harvesting of the separated charges from the active layer. PV devices based on spontaneous phase segregation in a blend structure do not provide a clear pathway for charge transport through the active layer, limiting efficiency due to charge recombination. An ordered heterojunction active layer is the goal of many research efforts and would require structural control of the polymer film on the nanoscale in order to maximize both charge separation and charge transport. The goal of this seed project has been to modify inorganic nanoparticle surfaces with well-defined conducting polymers, which ensures an intimate donor/acceptor interface and allows for better control of film nano-morphology.

We have developed a new synthetic method using the reversible addition-fragmentation chain transfer (RAFT) process to produce regioregular poly(3-hexylthiophene) (rr-P3HT) with low polydispersity, end group control, and the ability to prepare block copolymers with almost unlimited functionality. We have also demonstrated the covalent attachment of the rr-P3HT to the surface of solution synthesized gold nanoparticles using an efficient multistep process. Particles prepared in this way are shown in the top TEM image where the polymer coating is visible. In the middle SEM image, improved dispersion of the polymer modified gold rods, compared to unmodified nanorods, in a P3HT film is visible. Gold is not likely to be an ideal electron acceptor, but instead provided a prototypical nanoparticle surface to use in developing the surface attachment chemistry. CdSe nanorods, have been demonstrated to be a better acceptor for hybrid solar cells. To demonstrate the versatility of the surface modification technique, we have also surface modified CdSe nanorods with the rr-P3HT (bottom TEM). P3HT films consisting of either polymer modified CdSe nanorods or unmodified CdSe nanorods have been cast and are currently being evaluated. Seven students – 1 graduate student and 6 undergraduate students – including 5 women and 1 minority student were involved in this project. Two papers have been submitted, one discussing the new polymer synthesis to Macromolecules (submitted December 2010) and one discussing film formation and nanoparticle dispersion to Langmuir (submitted February 2011). Two more papers will be submitted in the near future, one paper discussing the PV properties of the hybrid films and one paper discussing adaptation of the developed surface modification technique to modify the surface of silicon nanostructures with rr-P3HT.

Proton Transport in Ionic Space Charge Regions A. Deml, R. O’Hayre, A. Bunge, W. Medlin, N. Sammes, R. Kee Renewable Energy MRSEC

The devices in computers that are used to switch electrical current on and off are field effect transistors. In these devices electric fields are used to switch the current. Researchers in the Renewable Energy MRSEC at the Colorado School of Mines have made the first “field effect transistor” that switches currents of charged atoms, called ionic currents. In this prototype device the atoms are positively charged hydrogen (protons) and the transport medium is a material called Nafion. Potential applications of this novel device include electrochemical switches and ionic logic components. Instead of nano-electronics one can now think about “nano-ionics”.


Proton Transport in Inorganic/Polymer Membranes A. Herring, D. Knauss, A. Dillon, J. Turner Renewable Energy MRSEC

Researchers at the Colorado School of Mines and their colleagues are synthesizing new polymers which bring together super acidic metal oxides with organic monomers. The result is a new material hybrid which can transport protons at high temperatures without using much water. These materials will allow fuel cells to be designed for use in hotter and drier environments.

Proton Transport in Metal/Ceramic Membranes R. O’Hayre, N. Sammes, M. Lusk, W. Medlin, A. Bunge Renewable Energy MRSEC

Researchers at the Colorado School of Mines and their colleagues are developing a composite material to vastly increase the rate of proton conduction through ceramics. Nanosized metal particles, embedded within a ceramic, generate an electronic space charge layer at metal/ceramic interfaces. Based on the theory that protons move quickly through such regions, composite materials have been designed in which the space charge layers are interconnected. This results in an entirely new form of proton conductor which could be a boon to fuel cell technology.

Seed Grants

High Throughput, High Resolution Characterization of Membrane DurabilityCorinne PackardThe mechanical properties of polymeric membranes are HIGHLY dependent on both the temperature and the relative hunmidity., which dramatically impacts the reliability of these membranes. SA new instrument developed by Professor Corinne Packard, who holds a joint appointment at the Colorado School of Mines and the National Renewable Energy Laboratory, enables in-situ testing of polymer membranes at varying temperatures and humidities. Testing of a standard membrane (Nafion) reveals a dramatic softening at elevated humidity.

H2 Extraction from Ammonia Borane MaterialsS. Sachdeva, C.A. Koh, A.M. Herring, A.K. Sum

Ammonia borane has a high hydrogen content of 19.6 wt.%, which far exceeds the current hydrogen storage targets. A number of different methods have been attempted to dehydrogenate ammonia borane, including thermal decomposition, catalysis, and using mesoporous scaffolds. There have been significant disadvantages with these other dehydrogenation methods, including the requirement of high temperature conditions and/or the production of side products, in addition to the desired hydrogen product.


Our recent work has shown for the first time that ammonia borane can be dehydrogenated using heteropolyacids at ambient temperature and pressure conditions, with minimal side products. Furthermore, within a few minutes, the hydrogen can be released from the ammonia borane material. The right hand plot shows the effect of increasing the silicotungstic acid addition from 9 to 18 mole% on the amount of hydrogen released from ammonia borane.

The implications of this work are that ammonia borane could be used with heteropolyacids as the anode catalyst, thereby generating hydrogen for use in proton exchange membrane fuel cells which are a state of the art technology. We are currently preparing a manuscript on this work that will be submitted to an academic refereed journal. The results are also being presented at the ACS annual meeting in 2011.

Storing Hydrogen in Novel Clathrate Materials T. Sugahara, S. Sachdeva, D. Baker, J. Haag, M. Braniff, J. Difulvio, D. Rainey, C. A. Koh, A. M. Herring, A. K. Sum, P. C. Taylor, A. Dillon, K. O’Neill

The initial seed project has been focused on the development of novel clathrate materials for storing hydrogen and fundamental understanding on hydrate formation which is key to developing these potential energy storage materials. The project has involved 5 REU summer students, with three of these REU students being co-authors on publications. In order to obtain higher hydrogen storage capacities in clathrate hydrates, the large cages must be occupied. We have shown for the first time that these large cages can be occupied with hydrogen and occupancy is sensitive to the formation pressure (published in J. Phys. Chem. B).

Discovery of new clathrate frameworks for hydrogen storage has also been accomplished in this initial seed project. The use of hydroquinone clathrate materials for direct fuel cell operation has been demonstrated and optimized. Most recently, we have shown for the first time that hydrogen can be stored within silicon clathrate materials at ambient temperature and pressure conditions. The experiments are closely coupled with theory, and the results suggest a dependence on the hydrogen enclathration extent and metal dopant concentration. This work is currently being prepared for publication in a refereed journal.

How Ice GrowsCarolyn Koh, Amadeu Sum, Dendy Sloan - Renewable Energy MRSEC, NSF DMR-0820518

Scientists at the Renewable Energy MRSEC at the Colorado School of Mines have for the first time modeled the formation (nucleation) and growth of a special form of ice that is very effective in storing hydrogen as a fuel. In the pictures above, growth begins in the upper left hand corner. This model simulates how the water molecules come together to form the structure. Understanding the mechanism for this nucleation is critical to controlling the formation of this form of ice to be used in many energy applications, especially storage.


Hydrogen Storage in IceCarolyn Koh, Amadeu Sum, Dendy SloanRenewable Energy MRSEC

If hydrogen is ever going to be used as a fuel, then it must be stored efficiently and safely. A special form of ice grown only at high pressure, as shown in the picture (bottom right), can store hydrogen to be used as a fuel. Professors at the Colorado School of Mines Renewable Energy MRSEC have developed a new method for dramatically improving hydrogen storage in this form of ice. This new method enables hydrogen to be stored in both the small and large cages shown at the tails of the green arrow in the picture. Previously only small cages could store hydrogen. This new synthesis method is critical to improving storage capacities.

Hydrogen Storage in New Clathrate Compounds Carolyn Koh and Dendy SloanRenewable Energy MRSEC

Professors Carolyn Koh and Dendy Sloan of the Colorado School of Mines Renewable energy MRSEC and their colleagues have discovered a new material for storage of hydrogen, which may be an important fuel in the future. This material is a special form of ice, known as a clathrate, which has a very open structure. Enough hydrogen can be stored in this structure so that it will burn in air with water as the only by product.

Facilities Highlights

PECVD UpgradeJ. Beach and J. Johnson

The Renewable Energy Materials Research Science and Engineering Center manages a state-of-art Plasma Enhanced Chemical Vapor Deposition cluster tool and gas phase synthesis laboratory. The tool has three process chambers, expandable to seven, and a robotic transfer module allowing samples to be moved between chambers to fabricate very complicated nanostructures. The system is essential to the group IV nanostructure research within the Center with nanowire and quantum dot synthesis activities in IRG1 preformed within the lab. This shared use facility is unique within Colorado and CSM is one of only a few campuses in the US to have similar systems. A major upgrade of the tool is underway to add new capabilities and additional safety features essential to the Center’s work on group IV nanostructures. As part of this upgrade, the laboratory is also being upgraded to the most recent International Fire Code for silane. The upgrade includes a new gas manifold which has arrived and in now being installed. This will allow all chambers to access all process gases at the same time with room for expansion. A monitoring system for silane, which is a pyrophoric gas, will be expanded to inlcude toxic gases and monitoring will be extended to the gas manifold enclosure improving safety. After this upgrade


the lab will be approved for both toxic and pyrophoric gas use. This will allow us to work with germane which can be used to make Ge and alloy Ge1-xSix nanostructures as well as Ge/Si core shell structures. The addition of phosphine, diborane, and arsine will allow doping. The inclusion of dopants in nanostructures, where they are located and resulting differences in how they add carriers and scatter carriers relative to doping in the bulk is a critical question in semiconductor nanostructure research.

Chemical Synthesis LaboratoryJ. Beach, I. Anderson, T. Lane, A. M. Herring, P. C. Taylor, and R. T. Collins

A year long, from planning to end, laboratory renovation to create a state-of-the-art shared-use chemical synthesis laboratory is now complete and the lab is open for business. The laboratory is managed by the Renewable Energy Materials Research Science and Engineering Center (REMRSEC) and the renovation was funded by the Colorado School of Mines as part of its financial commitment to the Center. The lab includes a broad range of modern capabilities. In addition to those listed on the slide, it has a gowning room, plumbed in DI water and process gases with these services plumbed into each hood. A region of the lab containing two ultra-hepa filtered nanoparticle hoods can be partitioned from the lab to create a contained environment for work with nano materials. The two glove box system includes refrigerated in-box, chemical storage, integral spin coater, in box chemical balance, solvent purifiers with both internal to the glove box and external access to the solvents. The boxes also contain a host of electric and optical feedthroughs to enable controlled environment characterization. Attention has been paid to proper storage of chemicals, exhaust snorkels for bench top experiments, and proper training in advance of laboratory access with written standard operating procedures for lab and lab equipment use. Key card entry and logging are used to control and monitor lab access and the lab is handicap accessible.

New Synthesis LaboratoryJoe Beach, Paul Stradins, Reuben Collins, Andrew HerringRenewable Energy MRSEC

New facilities are available with eight general purpose hoods and two glove boxes. Two on the hoods are designed to be safe for nano-particle synthesis and handling. Safe handling of nano-particles is becoming more and more important as we learn more about possible health hazards.


Multifunctional Microscope for the Characterization of Renewable Energy Materials Renewable Energy MRSEC

Researchers at the Colorado School of Mines are harnessing a new microscope system which enables a non-destructive, sample-independent means of assessing the structural and chemical properties of a variety of different renewable energy materials, including catalysts and electrolytes for fuel cells, semiconducting thin films for solar cells, and clathrate-based solids for hydrogen storage. A new variable temperature stage is being developed for the microscope, which will provide a unique capability to investigate materials in-situ under a range of extreme conditions.

Education and Outreach Highlights

Research Experiences for Undergraduates in Renewable EnergyCharles A. Stone, IV

The 2012 Renewable Energy REU at the Colorado School of Mines (CSM) hosted 21 students from 13 different institutions (11 national, 2 international) in a 10-week summer program that strived for gender balance (6 females, 15 males) and diversity (6 underrepresented minorities, 2 non-traditional students), as well as a balance between participants from research institutions and from institutions where research opportunities for students are limited.

These 21 students participated in research discussions, laboratory tours, social activities, and an end-of-summer joint poster session with other nearby REU students in the Advanced Metallurgical Design for Transportation, Infrastructure, and Energy REU at CSM; the Advancing Polymer Materials by Integrating Chemistry and Chemical Engineering REU at CSM; the National Nanotechnology Infrastructure Network (NNIN) REU at the University of Colorado, Boulder; and the Science Undergraduate Laboratory Internship (SULI) program at the National Renewable Energy Laboratory,

Rachel Kurchin from Yale University earned the Best Technical Achievement award for her research on “Raman Spectroscopy of Silicon Quantum Dots”.

Charlotte Evans from University of Wisconsin, River Falls earned the Best Presentation award for best communicating the nature, impact, and results of her research on “Catalyst-Free ‘Click Chemistry’ of Zinc Oxide Surfaces”.

Research Experiences for Undergraduates in Renewable EnergyCharles A. Stone, IV

An interdisciplinary team of approximately 30 faculty from the Colorado School of Mines and scientists from the National Renewable Energy Laboratory, mentored students in projects addressing the performance of next-generation photovoltaic devices; microstructural design of composite membranes; hydrogen storage


in clathrate hydrates; social and ethical implications of climate change, renewable energy, sustainability & education; hybrid energy systems for oil shale production; and optimizing computational tools for energy science. Student “Snapshots” Sessions allowed students to informally share their research results in an open learning environment.

The 2011 Renewable Energy REU at the Colorado School of Mines hosted 20 students from 14 different institutions (12 national, 2 international) in a 10-week summer program that strived for gender balance (11 females, 9 males) and diversity (3 underrepresented minorities, 1 non-traditional student), as well as a balance between participants from research institutions and from institutions where research opportunities for students are limited. These 20 students participated in research discussions, laboratory tours, social activities, and an end-of-summer joint poster session with other nearby REU students in the National Nanotechnology Infrastructure Network (NNIN) program at the University of Colorado, Boulder and the Science Undergraduate Laboratory Internship (SULI) program at the National Renewable Energy Laboratory.

Joseph Carloni from Binghamton University earned the Best Technical Achievement award for his research on “The Effect of Environmental Aging on the Mechanical Properties of PMMA Material Used in Concentrating Photovoltaics”.

Emily Tansey from Mount Holyoke College earned the Best Presentation award for best communicating the nature, impact, and results of her research on “Synthesis & Characterization of Br – and Cl – Anion Exchange Membranes for use in Alkaline Polymer Electrolyte Fuel Cells”.

International Student ExchangeBrian Simonds, Yong-Heng So, Ivan Perez-Würfl, Richard Ahrenkiel, Craig Taylor

Through an NSF fellowship, graduate student Brian Simonds spent summer 2011 with collaborators at the University of New South Wales learning to synthesize novel silicon quantum dot arrays.

The University of New South Wales (UNSW) is an international strategic partner of REMRSEC as they too are pursuing a silicon quantum dot solar cell. This partnership was strengthened this year when graduate student Brian Simonds was awarded an NSF East Asia and Pacific Summer Institute fellowship to UNSW for summer 2011 to carry out research using UNSW facilities and unique capabilities.

UNSW use a significantly different approach to create Si quantum dots than is presently used in REMRSEC. Their dots are nucleated in a silicon rich oxide layer. These layers are stacked on top of one another with separating stochiometric oxide layers. When the films are annealed, dots form in the silicon rich layer creating a superlattice geometry (TEM image on the slide). This technique creates a film of silicon quantum dots separated by insulating silicon dioxide where the size and spacing of the dots can be reasonably well controlled. This capability is ideal for performing systematic studies on basic silicon quantum dot properties where these parameters are important. It was for this reason that Brian spent the summer at UNSW preparing samples for characterization studies using REMRSEC facilities.

During the fellowship, materials were prepared for two separate experiments. The first was to study the effect that dot size and separation have on photoconductivity. In addition to needing a series of samples with well controlled parameters, a very sensitive non-contact technique of measuring photoconductivity is needed. REMRSEC’s partnership with The National Renewable Energy Laboratory allows access to one


such technique called time-resolved terahertz spectroscopy. These experiments are currently underway. The second experiment was designed to investigate the role of hydrogen and phosphorous incorporation during deposition. This was done with REMRSEC’s electron spin resonance facility. Through these studies it was determined that hydrogen’s role is sharply dependent on dot size while confirming the difficulty of phosphorous doping silicon dot materials. Results of this work are being presented at E-MRS in May 2012 as well as the International Conference for Young Researchers of Advanced Materials.

K-12 OutreachJennifer Strong, Linda Lung and Barbara Moskal

Partnership teachers and CSM graduate students attend a ten day, six hour per day summer workshop. For the teachers, this workshop addresses the applications of mathematics and science to energy and renewable energy. CSM graduate students receive instruction on K-12 education, literacy in mathematics and science classrooms, cultural differences and effective strategies for working with diverse populations. Joint sessions are held among graduate students and teachers, allowing for collaboration and brainstorming on lesson plans that are implemented during the academic year. The bond between the graduate students and the teachers begins to develop during the summer and is strengthened throughout the academic year. These workshops are taught in collaboration with expert district teachers, CSM faculty, and, since 2009, engineers and scientists from the National Renewable Energy Laboratory (NREL). Each workshop further offers the option of continuing education credits which are necessary for participating teachers to maintain state teaching certification. Pre and post content exams indicate that both the participating teachers and graduate students display statistically significant gain with respect to the content covered. The middle school component of this program was recently recognized in 2010 by the American Society for Engineering Education as a best practice in K-12 partnerships.

K-12 Summer Teacher WorkshopCharles Stone, Linda Lung - Renewable Energy MRSEC

The Renewable Energy MRSEC at the Colorado School of Mines in collaboration with the outreach division at the National Renewable Energy Laboratory held a two week workshop for math and science teachers from public school catering to under-represented minorities. The teachers were given hands-on experiences for projects in renewable energy to incorporate into their lesson plans.

Energy Minor at Colorado School of MinesJames McNeil - Renewable Energy MRSECThe Renewable Energy MRSEC at the Colorado School of Mines was instrumental in establishing a renewable energy undergraduate minor that is unique because it features both a renewable energy track and a traditional energy track. This approach is important because both types of energy will be important for the foreseeable future.


Research Experiences for Undergraduates (REU)Charles Stone, Linda LungRenewable Energy MRSEC

The Renewable Energy MRSEC at the Colorado School of Mines in collaboration with the outreach division at the National Renewable Energy Laboratory held a ten week Research Experiences for Undergraduates program on renewable energy in which over half of the 20 students were women.

Creation of an Energy Minor Renewable Energy MRSEC

A central educational goal of the Renewable Energy MRSEC has been the creation of an undergraduate energy minor with a renewable track. A campus wide committee was created in Fall 2008 to develop this minor. The proposal the committee developed consists of tracks in renewable energy, fossil energy, and a general track spanning fossil, renewable, and nuclear energy. The minor will be accessible to any CSM student. Preliminary interest surveys suggest it will attract a disproportionate number of students from underrepresented groups. It is on track to be implemented beginning in the fall of 2009. Campus response has been overwhelmingly positive.

Renewable Energy Research Experiences for UndergraduatesChuck Stone and Barbara OldsRenewable Energy MRSEC

Professor Chuck Stone, REMRSEC REU Coordinator and Professor Barbara Olds, REMRSEC Education and Human Resources Director, held an open house to advertise the first Research Experiences for Undergraduates program of the Renewable Energy MRSEC. It will be held 1 June through 5 August 2009. Over 65 interested students from departments across campus attended and many followed up with applications. The Renewable Energy MRSEC is clearly striking a chord with students from all disciplines.It will be held 1 June through 5 August 2009. Over 65 interested students from departments across campus attended and many followed up with applications. The Renewable Energy MRSEC is clearly striking a chord with students from all disciplines.


For more information:http://remrsec.mines.edu/remrsechighlights.htm

or contact:

REMRSEC Offi ce1500 Illinois Street

Colorado School of MinesGolden, CO 80401

[email protected](303) 273-3756

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