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Book Magnetooptical properties of dilute nitride nanowires

Download or read book Magnetooptical properties of dilute nitride nanowires written by Mattias Jansson and published by Linköping University Electronic Press. This book was released on 2020-06-18 with total page 77 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanostructured III-V semiconductors have emerged as one of the most promising materials systems for future optoelectronic applications. While planar III-V compounds are already at the center of the ongoing lighting revolution, where older light sources are replaced by modern white light LEDs, fabricating such materials in novel architectures, such as nanowires and quantum dots, creates new possibilities for optoelectronic applications. Not only do nanoscale structures allow the optically active III-V materials to be integrated with silicon microelectronics, but they also give rise to new fascinating properties inherent to the nanoscale. One of the key parameters considered when selecting materials for applications in light-emitting and photovoltaic devices is the band gap energy. While alloying of conventional III-V materials provides a certain degree of band gap tunability, a significantly enhanced possibility of band gap engineering is offered by so-called dilute nitrides, where incorporation of a small percentage of nitrogen into III-V compounds causes a dramatic down-shift of the conduction band edge. In addition, nitrogen-induced splitting of the conduction band in dilute nitrides can be utilized in intermediate band solar cells, belonging to the next generation of photovoltaic devices. For any material to be viable for optoelectronic applications, detailed knowledge of the electronic structure of the material, as well as a good understanding of carrier recombination processes is vital. For example, alloying may not only cause changes in the electronic structure but can also induce disorder. Disorder-induced potential fluctuations may alter charge carrier and exciton dynamics, and may even induce quantum confinement. Moreover, various defects in the material may introduce detrimental non-radiative (NR) states in the band gap deteriorating radiative efficiency. It is evident that, due to their different growth mechanisms, such properties could be markedly different in nanowires as compared to their planar counterparts. In this thesis, I aim to describe the electronic structure of dilute nitride nanowires, and its effects on the optical properties. Firstly, we investigate the electronic structure, and the structural and optical properties of novel GaNAsP nanowires, with a particular focus on the dominant recombination channels in the material. Secondly, we show how short-range fluctuations in the nitrogen content lead to the formation of quantum dots in dilute nitride nanowires, and investigate their electronic structure. Finally, we investigate the combined charge carrier and exciton dynamics of the quantum dots and effects of defects in their surroundings. Before considering individual sources of NR recombination, it is instructive to investigate the overall effects of nitrogen incorporation on the structural properties of the nanowires. In Paper I, we show that nitrogen incorporation up to 0.16% in Ga(N)AsP nanowires does not affect the overall structural quality of the material, nor does nitrogen degrade the good compositional uniformity of the nanowires. It is evident from our studies, however, that nitrogen incorporation has a strong and complex effect on recombination processes. We first show that nitrogen incorporation in GaNAsP nanowires reduces the NR recombination at room temperature as compared to the nitrogen-free nanowires (Paper I). This is in stark contrast to dilute nitride epilayers, where nitrogen incorporation enhances NR recombination. The reason for this difference is that in nanowires the surface recombination, rather than recombination via point defects, is the dominant NR recombination mechanism. We suggest that the nitrogen-induced suppression of the NR surface recombination in the nanowires is due to nitridation of the nanowire surface. Another NR recombination channel common in III-V nanowires is caused by the presence of structural defects, such as rotational twin planes and stacking faults. Interestingly, while nitrogen incorporation does not appear to affect the density of such structural defects, increasing nitrogen incorporation reduces the NR recombination via the structural defects (Paper II). This is explained by competing trapping of excited carriers/excitons to the localized states characteristic to dilute nitrides, and at nitrogen-induced NR defects. This effect is, however, only present at cryogenic temperatures, while at room temperature the NR recombination via the structural defects is not the dominant recombination channel. Importance of point defects in carrier recombination is highlighted in Paper III. Using the optically detected magnetic resonance technique, we show that gallium vacancies (VGa) that are formed within the nanowire volume act as efficient NR recombination centers, degrading optical efficiency of the Ga(N)AsP-based nanowires. Interestingly, while the defect formation is promoted by nitrogen incorporation, it is also readily present in ternary GaAsP nanowires. This contrasts with previous studies on planar structures, where VGa was not formed in the absence of nitrogen, unless subjected to irradiation by high-energy particles or heavy n-type doping. This, again, highlights how the defect formation is strikingly different in nanowires as compared to planar structures, likely due to the different growth processes. Potential fluctuations in the conduction band, caused by non-uniformity of the nitrogen incorporation, is characteristic to dilute nitrides and is known to cause exciton/carrier localization. We find that in dilute nitride nanowires, such fluctuations at the short range cause three-dimensional quantum confinement of excitons, resulting in optically active quantum dots with spectrally ultranarrow and highly polarized emission lines (Paper IV). A careful investigation of such quantum dots reveals that their properties are strongly dependent on the host material (Papers V, VI). While the principal quantization axis of the quantum dots formed in the ternary GaNAs nanowires is preferably oriented along the nanowire axis (Paper V), it switches to the direction perpendicular to the nanowire axis in the quaternary GaNAsP nanowires (Paper VI). Another aspect illustrating the influence of the host material on the quantum-dot properties is the electronic character of the captured hole. In both alloys, we show coexistence of quantum dots where the captured holes are of either a pure heavy-hole character or a mixed light-hole and heavy-hole character. In the GaNAs quantum dots, the main cause of the light- and heavy-hole splitting is uniaxial tensile strain induced by a combination of lattice mismatch with the nanowire core and local alloy fluctuations (Paper V). In the GaNAsP quantum dots, however, we suggest that the main mechanism for the light- and heavy-hole splitting is local fluctuations in the P/As ratio (Paper VI). Using time correlation single-photon counting, we show that the quantum dots in these dilute nitride nanowires behave as single photon emitters (Paper VI), confirming the three-dimensional quantum confinement of the emitters. Finally, since the quantum dots are formed by fluctuations mainly in the conduction band, only electrons are preferentially captured in the 0D confinement potential, whereas holes are expected to be mainly localized through the Coulomb interaction once an electron is captured by the quantum dot. In Paper VII, we investigate this rather peculiar capture mechanism, which we show to lead to unipolar, negative charging of the quantum dot. Moreover, we demonstrate that carrier capture by some quantum dots is strongly affected by the presence of defects in their local surroundings, which further alters the charge state of the quantum dot, where formation of the negatively charged exciton is promoted at the expense of its neutral counterpart. This underlines that the local surroundings of the quantum dots may greatly affect their properties and illustrates a possible way to exploit the defects for charge engineering of the quantum dots. In summary, in this thesis work, we identify several important non-radiative recombination processes in dilute nitride nanowires that can undermine the potential of these novel nanostructures for future optoelectronic applications. The gained knowledge could be found useful for designing strategies to mitigate these harmful processes, thereby improving the efficiency of future light-emitting and photovoltaic devices based on these nanowires. Furthermore, we uncover a set of optically bright quantum dot single-photon emitters embedded in the dilute nitride nanowires, and reveal their unusual electronic structure with strikingly different confinement potentials between electrons and holes. Our findings open a new pathway for charge engineering of the quantum dots in nanowires, attractive for applications in e.g. quantum computation and optical switching.

Book Physics and Applications of Dilute Nitrides

Download or read book Physics and Applications of Dilute Nitrides written by Irina A. Buyanova and published by CRC Press. This book was released on 2020-06-30 with total page 442 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since their development in the 1990s, it has been discovered that diluted nitrides have intriguing properties that are not only distinct from those of conventional semiconductor materials, but also are conducive to various applications in optoelectronics and photonics. The book examines these applications and presents a broad and in-depth look at the basic electronic and optical properties of diluted nitrides. The aim of Physics and Applications of Diluted Nitrides is to provide graduate students, researchers and engineers with a comprehensive overview of the present knowledge and future perspectives of diluted nitrides. Co-authored by a group of leading scientists in the field, this book brings the reader up to speed on the development and current state of diluted nitride applications, as well as the technologies to be developed in the near future.

Book Plasmonic and Magneto Optical Properties of Nonstoichiometric Indium Nitride Nanostructures

Download or read book Plasmonic and Magneto Optical Properties of Nonstoichiometric Indium Nitride Nanostructures written by Shuoyuan Chen and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Localized surface plasmon resonance (LSPR) in semiconductor nanostructures have attracted intense attention recently for its broad application in bio-imaging, chemical sensing, photocatalysis, and photovoltaics. Compared to the LSPR in metallic nanocrystals (NCs), LSPR in semiconductor NCs is highly tunable in the infrared region by tailoring chemical composition and stoichiometry. Moreover, LSPR along with external magnetic field allows the exploration of magneto-plasmonic coupling in single-phase semiconductors, opening up the magneto-optical ways to control charge carriers. In this thesis, we focus on the LSPR as well as magneto-optical properties of indium nitride (InN), providing valuable insights into the insufficiently researched III-V group semiconductors. Wurtzite phase InN NCs were successfully synthesized using the low-temperature colloidal method, and the plasmon intensity is tunable by changing the synthesis environment and varying doping concentrations of aluminum and titanium ions. Due to the combined effects of conduction band non-parabolicity and intraband transition, our InN NCs with different plasmon intensities have an almost fixed plasmonic energy of 0.37 eV. Besides, the optical bandgap of pure InN NCs ranges from 1.5 to 1.75 eV, depending on the reaction conditions, while that of the Al and Ti-doped InN varies from 1.65 to 1.85 eV. The plasmon-dependent phonon change is evaluated by the Raman spectroscopy. Differences in the longitudinal-optical (LO) phonon mode was observed for InN with high and low plasmon intensity. The magneto-optical properties of InN NCs were measured by the magnetic circular dichroism (MCD). The field-dependence and temperature-independence of the measured MCD spectra were investigated, and the plasmon-induced polarization of carriers was demonstrated. Tuning of the carrier polarization by varying LSPR and external magnetic field corroborates the hypothesis of non-resonant coupling between plasmons and excitons in a single-phase semiconductor. The results of this work demonstrate that LSPR can act as a degree of freedom in manipulating electrons in technologically-important III-V nanostructures and lead to potential applications in photonics and quantum computing at room temperature. Finally, InN nanowires (NWs) with LSPR were fabricated via low-temperature chemical vapor deposition (CVD) approach, laying the groundwork for the future research of LSPR and magneto-plasmonics in a one-dimensional system.

Book Properties and Applications of Silicon Carbide

Download or read book Properties and Applications of Silicon Carbide written by Rosario Gerhardt and published by BoD – Books on Demand. This book was released on 2011-04-04 with total page 550 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this book, we explore an eclectic mix of articles that highlight some new potential applications of SiC and different ways to achieve specific properties. Some articles describe well-established processing methods, while others highlight phase equilibria or machining methods. A resurgence of interest in the structural arena is evident, while new ways to utilize the interesting electromagnetic properties of SiC continue to increase.

Book IIl nitride Nanowires and Heterostructures

Download or read book IIl nitride Nanowires and Heterostructures written by Xiang Zhou (Ph. D.) and published by . This book was released on 2014 with total page 194 pages. Available in PDF, EPUB and Kindle. Book excerpt: Gallium nitride (GaN) and indium gallium nitride (InGaN) nanowires promise potential for further improving the electricity-to-light energy conversion efficiencies in light emitting diodes due to strain relaxation, reduced density of structural defects, and easier light extraction. Material quality and effective band engineering of such III-nitride nanowires are crucial for the design and fabrication of their optoelectronic applications such as LEDs, lasers and photodetectors. In this thesis, we first demonstrate effective control over GaN nanowire size, growth rate and structural quality through careful choice of metal seed particles. The differences in morphology, structural defects and optical properties of GaN nanowires grown by metalorganic chemical vapor deposition were studied systematically by electron microscopy and photoluminescence, and related to supersaturation in different seed particles and nanowire nucleation mechanisms. These results also demonstrate that systematic screening of seed materials is essential for synthesizing nanostructures with defect-free structures and other functional heterostructures. Next, challenges for nanoscale mapping of band engineering were successfully addressed through direct spatial correlation of optical properties to a variety of III-nitride heterostructures grown by molecular beam epitaxy, including GaN p-n junction nanorods, InGaN nanodisks, and GaN quantum disks and quantum wires. We demonstrate that effective doping, alloying and quantum confinement can be readily achieved in nanowire heterostructures, by cathodoluminescence in scanning transmission electron microscopy. P-n junction position and carrier diffusion lengths inside a single GaN nanorod were determined with nanometer spatial resolution. InGaN disk compositional uniformities were quantified from their optical emissions, which revealed substantial compositional inhomogeneity in bottom-up synthesized nanostructures. The studies on optical properties of individual GaN quantum structures demonstrated that small differences in the degree of quantum confinements resulted in substantial changes in the optical band gap. More importantly, reduced light emissions are directly correlated to regions containing grain boundaries, dislocations and stacking faults, which were formed as a result of nanorod coalescence and fluctuations in growth environment during nanostructure synthesis. Our findings demonstrate that controlling compositional and structural homogeneity, understanding defect formation mechanism and their effects on materials properties are key challenges to be addressed for developing large scale functional devices based on bottom-up synthesized nanostructured materials.

Book Direction Dependent Electrical and Optical Properties of Gallium Nitride Nanowires

Download or read book Direction Dependent Electrical and Optical Properties of Gallium Nitride Nanowires written by Rahul Makkena and published by . This book was released on 2006 with total page 81 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis also presents optical characterization of the as-synthesized nanowires. Raman spectroscopy, photoluminescence, photoconductivity and ultra violet (UV) visible absorption measurements on the samples containing a- and c-axis nanowires have shown that bandgap of the nanowires grown along the a-axis blue shifts by about 45-70meV compared to the nanowires grown along c-axis.

Book Diluted Magnetic  semimagnetic  Semiconductors

Download or read book Diluted Magnetic semimagnetic Semiconductors written by Roshan Lal Aggarwal and published by . This book was released on 1987 with total page 350 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Dilute Nitride Semiconductors

Download or read book Dilute Nitride Semiconductors written by Mohamed Henini and published by Elsevier. This book was released on 2004-12-15 with total page 648 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book contains full account of the advances made in the dilute nitrides, providing an excellent starting point for workers entering the field. It gives the reader easier access and better evaluation of future trends, Conveying important results and current ideas. Includes a generous list of references at the end of each chapter, providing a useful reference to the III-V-N based semiconductors research community. The high speed lasers operating at wavelength of 1.3 μm and 1.55 μm are very important light sources in optical communications since the optical fiber used as a transport media of light has dispersion and attenuation minima, respectively, at these wavelengths. These long wavelengths are exclusively made of InP-based material InGaAsP/InP. However, there are several problems with this material system. Therefore, there has been considerable effort for many years to fabricate long wavelength laser structures on other substrates, especially GaAs. The manufacturing costs of GaAs-based components are lower and the processing techniques are well developed. In 1996 a novel quaternary material GaInAsN was proposed which could avoid several problems with the existing technology of long wavelength lasers. In this book, several leaders in the field of dilute nitrides will cover the growth and processing, experimental characterization, theoretical understanding, and device design and fabrication of this recently developed class of semiconductor alloys. They will review their current status of research and development. Dilute Nitrides (III-N-V) Semiconductors: Physics and Technology organises the most current available data, providing a ready source of information on a wide range of topics, making this book essential reading for all post graduate students, researchers and practitioners in the fields of Semiconductors and Optoelectronics Contains full account of the advances made in the dilute nitrides, providing an excellent starting point for workers entering the field Gives the reader easier access and better evaluation of future trends, conveying important results and current ideas Includes a generous list of references at the end of each chapter, providing a useful reference to the III-V-N based semiconductors research community

Book Molecular Beam Epitaxy

    Book Details:
  • Author : Hajime Asahi
  • Publisher : John Wiley & Sons
  • Release : 2019-04-15
  • ISBN : 111935501X
  • Pages : 510 pages

Download or read book Molecular Beam Epitaxy written by Hajime Asahi and published by John Wiley & Sons. This book was released on 2019-04-15 with total page 510 pages. Available in PDF, EPUB and Kindle. Book excerpt: Covers both the fundamentals and the state-of-the-art technology used for MBE Written by expert researchers working on the frontlines of the field, this book covers fundamentals of Molecular Beam Epitaxy (MBE) technology and science, as well as state-of-the-art MBE technology for electronic and optoelectronic device applications. MBE applications to magnetic semiconductor materials are also included for future magnetic and spintronic device applications. Molecular Beam Epitaxy: Materials and Applications for Electronics and Optoelectronics is presented in five parts: Fundamentals of MBE; MBE technology for electronic devices application; MBE for optoelectronic devices; Magnetic semiconductors and spintronics devices; and Challenge of MBE to new materials and new researches. The book offers chapters covering the history of MBE; principles of MBE and fundamental mechanism of MBE growth; migration enhanced epitaxy and its application; quantum dot formation and selective area growth by MBE; MBE of III-nitride semiconductors for electronic devices; MBE for Tunnel-FETs; applications of III-V semiconductor quantum dots in optoelectronic devices; MBE of III-V and III-nitride heterostructures for optoelectronic devices with emission wavelengths from THz to ultraviolet; MBE of III-V semiconductors for mid-infrared photodetectors and solar cells; dilute magnetic semiconductor materials and ferromagnet/semiconductor heterostructures and their application to spintronic devices; applications of bismuth-containing III–V semiconductors in devices; MBE growth and device applications of Ga2O3; Heterovalent semiconductor structures and their device applications; and more. Includes chapters on the fundamentals of MBE Covers new challenging researches in MBE and new technologies Edited by two pioneers in the field of MBE with contributions from well-known MBE authors including three Al Cho MBE Award winners Part of the Materials for Electronic and Optoelectronic Applications series Molecular Beam Epitaxy: Materials and Applications for Electronics and Optoelectronics will appeal to graduate students, researchers in academia and industry, and others interested in the area of epitaxial growth.

Book 2D Monoelemental Materials  Xenes  and Related Technologies

Download or read book 2D Monoelemental Materials Xenes and Related Technologies written by Zongyu Huang and published by CRC Press. This book was released on 2022-04-19 with total page 166 pages. Available in PDF, EPUB and Kindle. Book excerpt: Monoelemental 2D materials called Xenes have a graphene-like structure, intra-layer covalent bond, and weak van der Waals forces between layers. Materials composed of different groups of elements have different structures and rich properties, making Xenes materials a potential candidate for the next generation of 2D materials. 2D Monoelemental Materials (Xenes) and Related Technologies: Beyond Graphene describes the structure, properties, and applications of Xenes by classification and section. The first section covers the structure and classification of single-element 2D materials, according to the different main groups of monoelemental materials of different components and includes the properties and applications with detailed description. The second section discusses the structure, properties, and applications of advanced 2D Xenes materials, which are composed of heterogeneous structures, produced by defects, and regulated by the field. Features include: Systematically detailed single element materials according to the main groups of the constituent elements Classification of the most effective and widely studied 2D Xenes materials Expounding upon changes in properties and improvements in applications by different regulation mechanisms Discussion of the significance of 2D single-element materials where structural characteristics are closely combined with different preparation methods and the relevant theoretical properties complement each other with practical applications Aimed at researchers and advanced students in materials science and engineering, this book offers a broad view of current knowledge in the emerging and promising field of 2D monoelemental materials.

Book Functional Metal Oxides

Download or read book Functional Metal Oxides written by Satishchandra Balkrishna Ogale and published by John Wiley & Sons. This book was released on 2013-11-08 with total page 478 pages. Available in PDF, EPUB and Kindle. Book excerpt: Functional oxides are used both as insulators and metallic conductors in key applications across all industrial sectors. This makes them attractive candidates in modern technology ? they make solar cells cheaper, computers more efficient and medical instrumentation more sensitive. Based on recent research, experts in the field describe novel materials, their properties and applications for energy systems, semiconductors, electronics, catalysts and thin films. This monograph is divided into 6 parts which allows the reader to find their topic of interest quickly and efficiently. * Magnetic Oxides * Dopants, Defects and Ferromagnetism in Metal Oxides * Ferroelectrics * Multiferroics * Interfaces and Magnetism * Devices and Applications This book is a valuable asset to materials scientists, solid state chemists, solid state physicists, as well as engineers in the electric and automotive industries.

Book Index to Theses with Abstracts Accepted for Higher Degrees by the Universities of Great Britain and Ireland and the Council for National Academic Awards

Download or read book Index to Theses with Abstracts Accepted for Higher Degrees by the Universities of Great Britain and Ireland and the Council for National Academic Awards written by and published by . This book was released on 2009 with total page 398 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Zinc Oxide Nanostructures

Download or read book Zinc Oxide Nanostructures written by Magnus Willander and published by CRC Press. This book was released on 2014-07-22 with total page 225 pages. Available in PDF, EPUB and Kindle. Book excerpt: Zinc oxide (ZnO) in its nanostructured form is emerging as a promising material with great potential for the development of many smart electronic devices. This book presents up-to-date information about various synthesis methods to obtain device-quality ZnO nanostructures. It describes both high-temperature (over 100 C) and low-temperature (under

Book Quantum Dots  Nanoparticles and Nanowires  Volume 789

Download or read book Quantum Dots Nanoparticles and Nanowires Volume 789 written by P. Guyot-Sionnest and published by . This book was released on 2004-05-04 with total page 456 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanostructures of semiconductors and metals show novel optical and transport properties, and offer the perspective of designing materials properties with unprecedented flexibility and control. This has motivated research in the synthesis and characterization of new materials. This 2004 book brings together scientists with various levels of expertise in the growth, characterization and applications of inorganic nanostructures, such as quantum dots, nanowires and nanorods, to discuss and share developments in the field. Reports focus on techniques to prepare and characterize novel materials, investigations of novel optical and electronic properties, and novel applications, such as those that are biologically inspired. Topics include: synthesis and characterization of semiconductor quantum dots, nanoparticles and nanowires using wet chemistry and molecular beam approaches; synthesis, characterization and novel properties of metallic nanostructures; optical properties of neutral and charged excitons and exciton complexes in self-assembled quantum dots; nanoscale devices and sensors based on nanostructures and their properties; and design and characterization of quantum dot-bioconjugates and their use in assay developments.

Book Compound Semiconductor Photonics

Download or read book Compound Semiconductor Photonics written by Chua Soo-Jin and published by CRC Press. This book was released on 2020-03-26 with total page 230 pages. Available in PDF, EPUB and Kindle. Book excerpt: This proceeding is a collection of selected papers presented at Symposium O of Compound Semiconductor Photonics in the International Conference on Materials for Advanced Technology (ICMAT), which was held in Singapore from 28 June to 3 July 2009. The symposium covers a wide range of topics from fundamental semiconductor materials study to photonic device fabrication and application. The papers collected are of recent progress in the active and wide range of semiconductor photonics research. They include materials-related papers on III-As/P, III-nitride, quantum dot/wire/dash growth, ZnO, and chalcogenide, and devices-related papers on photonic crystals, VCSEL, quantum dot/dash lasers, LEDs, waveguides, solar cells and heterogeneous integrat

Book Handbook of Materials Modeling

Download or read book Handbook of Materials Modeling written by Sidney Yip and published by Springer Science & Business Media. This book was released on 2007-11-17 with total page 2903 pages. Available in PDF, EPUB and Kindle. Book excerpt: The first reference of its kind in the rapidly emerging field of computational approachs to materials research, this is a compendium of perspective-providing and topical articles written to inform students and non-specialists of the current status and capabilities of modelling and simulation. From the standpoint of methodology, the development follows a multiscale approach with emphasis on electronic-structure, atomistic, and mesoscale methods, as well as mathematical analysis and rate processes. Basic models are treated across traditional disciplines, not only in the discussion of methods but also in chapters on crystal defects, microstructure, fluids, polymers and soft matter. Written by authors who are actively participating in the current development, this collection of 150 articles has the breadth and depth to be a major contributor toward defining the field of computational materials. In addition, there are 40 commentaries by highly respected researchers, presenting various views that should interest the future generations of the community. Subject Editors: Martin Bazant, MIT; Bruce Boghosian, Tufts University; Richard Catlow, Royal Institution; Long-Qing Chen, Pennsylvania State University; William Curtin, Brown University; Tomas Diaz de la Rubia, Lawrence Livermore National Laboratory; Nicolas Hadjiconstantinou, MIT; Mark F. Horstemeyer, Mississippi State University; Efthimios Kaxiras, Harvard University; L. Mahadevan, Harvard University; Dimitrios Maroudas, University of Massachusetts; Nicola Marzari, MIT; Horia Metiu, University of California Santa Barbara; Gregory C. Rutledge, MIT; David J. Srolovitz, Princeton University; Bernhardt L. Trout, MIT; Dieter Wolf, Argonne National Laboratory.