We have determined critical parametres that restrict the vapor→liquid drop→solid growth of silicon NWs. We demonstrate that there are maximum and minimum critical radii for NW growth and identify boundary conditions that lead to solvent droplet breakdown and crystal branching.

Magnetization behavior of Nd9(Fe, B)87Zr2Nb2 nanostructure magnets have been investigated. We will show that the nanostructure magnets are composed of magnetic clusters of exchange-coupled single domains and the coercivity is governed by coupling intensity between soft and hard magnetic clusters in the magnets.

ZnO nanostructures have attracted a great deal of interest because of their biocompatibility and outstanding optical and piezoelectric properties. Their uses are widely varying, including incorporation in sensors, solar cells, and nanogenerators. Biological systems are yet another area of application of ZnO nanowires. Apart from their electrical and optical properties, ZnO nanostructures can be used for the mechanical reinforcement of existing biomimetic scaffolds such as collagen and/or other biodegradable polymers (poly(lactic acid), polyglycolide, poly(alkyene succinate)s or polyhydroxylalkanoates). In this work, we have demonstrated a cheap and comparatively facile hydrothermal growth method for the bulk production of ZnO nanostructures exhibiting an aster-like geometry. The novel nanostructures of ZnO can be used as reinforced material to biopolymers. The aster shape has presented an increased surface area, providing a means for enhancing the stabilization of the gels and\or polymers. With controllable growth of ZnO nanostructures this method allows the geometry which could be tuned for maximal coupling between the two phases of composite and increased mechanical strength.

The α-polymorph of Li3FeF6 has been prepared from aqueous-based solution by precipitation under different conditions to obtain small particles. Several alcohols have been used to vary the precipitation media. Among them 2-propanol has been found to provide particles of about 100 nm under controlled conditions of temperature and H2O: R-OH volume ratio. The average particle size of some of the as-prepared samples is smaller than that obtained for those samples obtained by precipitation in water. However, the expected enhancement of electrochemical performances does not occur for the as-prepared samples. Inserted amount of lithium into the cryolite structure of Li3FeF6 increases significantly only when composites of asprepared Li3FeF6 and carbon are milled mechanically. For example 12h milling is needed to reach 64 mAh/g (45% of theoretical capacity).

We propose the use of amine-rich polyelectrolyte multilayers as a versatile, high quality, tunable adhesive surfaces for biomedical and nanotechnological applications. The films are simple to fabricate under mild conditions and provide at least as good adhesion as standard aminopropyltriethoxysilane terminated glass substrates. In addition, the multilayer surface can be reliably passivated by acetylation with acetic anhydride which reduces the adhesion to the point that non-specific binding of proteins and nanoparticles becomes all but negligible. We demonstrate that this property, in combination with the robustness of the film, makes it possible to pattern the adhesiveness of the film at the nanoscale level.

We briefly review our data on MOCVD growth problems of sandwich stacked heterostructures based on Bi-Sr-Ca-Cu-O and YBa2Cu3O7 high temperature superconductors. Non-superconducting layers were (Ca, Sr)CuO2, (Ca, Ba)CuO2 and Bi4Ti3O12. Structures were with c-axis normal or inclined with about 45° vs. the surface of the substrate. Film-substrate lattice relationship, growth mechanism and the resulting morphology controlling roughness and uniformity, stability domain of the phases and inter diffusion are all important aspects toward significant progress in the field. Our analysis indicates that requirements are more severe for non-c-axis heterostructures, and suggest some ideas for further improvements.

We have performed a detailed analysis of the magnetic (collinear and noncollinear) order and atomic and electron structures of UO2, PuO2 and UN on the basis of density functional theory with the Hubbard electron correlation correction (DFT+U). We have shown that the 3-k magnetic structure of UO2 is stabilized for the Hubbard parameter value of U=4.6 eV (while J=0.5 eV) when Dudarev’s formalism is used. UO2 keeps cubic shape in this structure. Two O atoms nearest to each U atom in direction of its magnetic moment move toward this U atom. Neither UN nor PuO2 shows the energetical preference for the rhombohedral distortion, in contrast to UO2, and, thus, no complex 3-k magnetic structure in these materials. Both materials have the AFM tetragonal <001> structure at reasonable choice of parameters U and J.

In this work, a room temperature spin-polarized LED based on ferromagnetic Ga1-xGdxN is reported. The device was grown by metalorganic chemical vapor deposition (MOCVD) and is the first report of a spin-LED based on Ga1-xGdxN. Electroluminescence from this device had a degree of polarization of 14.6% at 5000 Gauss and retained a degree of polarization of 9.3% after removal of the applied magnetic field. Ga1-xGdxN thin films were grown on 2 μm GaN templates and were co-doped with Si and Mg to achieve n-type and p-type materials. Co-doping of the Ga1-xGdxN films with Si produced conductive n-type material, while co-doping with Mg produced compensated p-type material. Both Si and Mg co-doped films exhibited room temperature ferromagnetism, measured by vibrating sample magnetometry.

A facile anodic electrophoretic deposition (EPD) process has been developed to prepare thin uniform films consisting of titanate nanotubes (TNTs) that were synthesized by a hydrothermal approach. Such an EPD process offers easy control in the film thickness and the adhesion to the substrate was found to be strong. The chemical composition and structure of the products have been characterized by HRTEM, FESEM, XRD and TG/DTA. It was found that the functionalization of TNTs plays a key role on the electrolyte stability and the successful formation of a uniform TNT film with good adhesion. The as-prepared TNT films show exceptional superhydrophilic behavior with ultra-fast spreading, while it converts to superhydrophobicity yet with high adhesion after 1H,1H,2H,2H-perfluorooctyl-triethoxysilane modification. This study provides an interesting method to prepare films with extremely high wettability contrast that are useful for producing different kinds of functional materials.

We have fabricated large-area, thin-film multijunction solar cells based on hydrogenated amorphous silicon (a-Si:H) and nanocrystalline silicon (nc-Si:H) made in a large area batch reactor. The device structure consisted of an a-Si:H/nc-Si:H/nc-Si:H stack on Ag/ZnO back reflector coated stainless steel substrate, deposited using our proprietary High Frequency (HF) glow discharge technique. For the nc-Si:H films, we investigated two deposition rate regimes: (i) low rate <1 nm/s and (ii) high rate >1 nm/s. We optimized the deposition parameters, such as pressure, gas flow, dilution, and power. We did SIMS analysis on the optimized films, and found the impurity concentrations were one order of magnitude lower than the films made with the conventional RF process. In particular, the oxygen concentration is reduced to ~1018 cm-3. This value is among the lowest oxygen concentration reported in literature. The low impurity content is attributed to proprietary cathode hardware and the optimized deposition process. During the initial optimization and investigative phase, we fabricated small-area (0.25 cm2 and 1.1 cm2) cells. The information obtained from the initial phase was used to fabricate large-area (aperture area 400 cm2) cells, and encapsulated the cells using the same flexible encapsulants that are used in our commercial product. We have light soaked the low-rate and high-rate encapsulated modules. The highest initial efficiency of the low-rate modules is 12.0% as confirmed by NREL. The highest corresponding stable efficiency attained for the low-rate samples cells is 11.35%. For the high-rate small-area (1.1 cm2) cells, the highest initial active-area efficiency and corresponding stable efficiency attained are 13.97% and 12.9%, respectively. We present the details of the research conducted to develop the low- and high-rate cells and modules.

We analyze the effect of charged defects on the electrical domains, phase transition characteristics and electrical properties of ferroelectric thin films with thin dead layers using a non-linear thermodynamic model. Depending on their density and field strength, defects can pin and couple to electrical domains in the film. For ultrathin films, depolarizing effects dominate and the transition from the paraelectric state is into the multidomain ferroelectric state during cooling and is strongly smeared. The competition between defect induced extrinsic effects and the dead layer related limit is demonstrated.

Metal-insulator-metal (MIM) resistive switching devices are being pursued for a number of applications, including non-volatile memory and high density/low power computing. Reported resistive switching devices vary greatly in the choice of metal oxide and electrode material. Importantly, the choice of both the metal oxide and electrode material can have significant impact on device performance, their ability to switch, and the mode of switching (unipolar, bipolar, nonpolar) that results. In this study, three metal oxides (Cu2O, HfOx, and TiOx) were deposited onto copper bottom electrodes (BEs). Four different top electrode (TE) materials (Ni, Au, Al, and Pt) were then fabricated on the various metal oxides to form MIM structures. Devices were then characterized electrically to determine switching performance and behavior. Our results show that the metal TE plays a large role in determining whether or not the MIM structure will switch resistively and what mode of switching (unipolar, bipolar, or non-polar) is observed.

Being a dedicated and enthusiastic high school science teacher is not enough to successfully prepare our children to take on the challenges of the 21st century and live up to its potential. We need high quality professional development opportunities in order to enrich our subject knowledge and teaching skills and reflect these skills in our craft. The Glenn Commission report, released ten years ago, details goals and associated action strategies included addressing professional development needs in order to deliver high-quality teaching as well as providing for teachers to engage in common study. We typically must scrutinize long lists of potential development opportunities to weigh the value of the program against the commitment of time and likelihood that intent of the training can be implemented. Beyond the training comes the quest for resources necessary for implementation and support to sustain the intent once new ideas and skills are brought back to school. Too often do teachers get their batteries charged from a professional development experience only to return to school where they become challenged to employ new skills or ideas and become further discouraged if there is no sustained support from the professional development sponsor. The best value-added programs that I have experienced are those where professional relationships can be forged through a significant and meaningful experience. Through these relationships, support networks can be established to help sustain knowledge and initiatives to provide a world-class education for our children.

I have had the excellent fortune to experience a top quality professional development program at the Princeton Center for Complex Materials (PCCM), a Materials Research Science and Engineering Center (MRSEC). My experience with the PCCM programs has demonstrated to me how a truly effective program can change lives. Over the past six consecutive summers I have gained invaluable experience starting with the Research Experience for Teachers (RET) program and subsequent involvement with PUMA and other PCCM programs that have provided me with the necessary resources to improve my teaching skills, depth of knowledge in my discipline and enable me to sustain a higher quality science program at my school. Through the RET program, I engaged directly with professors for two consecutive summers who were enthusiastic about helping improve my teaching skills and supportive of my pursuit to improve the science program at my school. This experience has led to the development of two new courses I have been able to offer for the past four years in Chemistry and Materials Science designed to engage students through hands on experiences. It was this experience that became the catalyst for me to further collaborate with local industry professionals who joined my cause and also helped in the development of one of the two new courses. Through this short paper, I will expand on my professional development experiences over the past six years to demonstrate how others can maximize opportunities provided by MRSEC educational outreach programs.

Nanoporous MgAl2O4 particulates with high porosities were successfully prepared from sol-gel reactions, solvent exchange with castor oil and subsequent combustion and calcination at 700 °C. The products were crystalline and semitransparent. Changes in the metal precursor concentrations allowed control of pore volumes from 0.7 to 1.1 cm3/g and average pore sizes from 14 to 19 nm. The specific surface areas are about 200 m2/g regardless of the precursor concentrations. After heating at 1000 °C for 10 hours, the products kept about 70% of their original pore volume and about 60% of the original surface area. Heating at 1100 °C caused a drastic reduction of pore volume and surface area to 40 and 36%, respectively, as the average particle size increased to 23 nm.

Polycrystalline samples of the single-layered cobaltate La2-x Cax CoO4 were prepared in a wide doping range of 0 ≤ x ≤ 1.5. Structural properties were characterized at room temperature. The orthorhombic distorted structure of the mother compound La2CoO4 changes to a tetragonal structure for x = 0.5 and then becomes orthorhombic again for x > 0.5. The magnetic properties were investigated in the temperature range from 5 K ≤ T ≤ 300 K. With increasing hole-doping a successive decrease of antiferromagnetic exchange is observed for x ≤ 0.5 whereas an increase of ferromagnetic exchange evolves for x ≥ 0.5.

In molecular solar energy harvesting systems, quantum mechanical features may be apparent in the physical processes involved in the acquisition and migration of photon energy. With a sharply declining distance-dependence in transfer efficiency, the excitation energy generally takes a large number of steps en route to the site of its utilization; quantum features are rapidly dissipated in an essentially stochastic process. In the case of engineered dendrimeric polymers, each such step usually takes the form of an inward hop between chromophores in neighboring generation shells. A physically intuitive, structure-determined adjacency matrix formulation of the energy flow affords insights into the key harvesting and inward funneling processes. A numerical method based on this analytic approach has now been developed and is able to deliver results on significantly larger dendrimeric polymers, with the help of large multi-processor computers. Central to this study is the interpretation of key features such as the relevance of a spectroscopic gradient and the presence of traps or irregularities due to conformational changes and folding. With the objective of fine-tune the funneling process, this model now allows the incorporation of parameters derived from quantum chemical calculations, affording new insights into the detailed operation of the harvesting process in a variety of dendrimer systems.

We describe how students explore materials science concepts using animated interactive spreadsheets. An engaging pedagogy is created in the classroom using spreadsheets in a way that initially camouflages mathematical complexity, which can later be revealed and taught. Use of off-the-shelf spreadsheet software, including freeware makes these spreadsheets universally available.

The length-scales at which thermal transport crosses from the diffusive to ballistic regime are of much interest particularly in the design and improvement of nano-structured materials. In this work, we demonstrate that the departure from diffusive transport has been observed in Si and GaAs using an optical transient thermal grating technique where an arbitrary, experimentally set length scale can be imposed on a material. In a transient thermal grating experiment, crossed laser pulses interfere creating a well-defined periodic absorption and temperature profile. A probe beam is diffracted from this transient grating and length-scale dependent thermal transport properties can be determined from the signal decay. As the length scale is decreased to lengths shorter than the mean free paths of heat carrying phonons, quasi-ballistic heat transport effects become apparent allowing us to map out length scales and mean free paths relevant to nondiffusive thermal transport in Si and GaAs.