We propose using macroporous silicon as an ultra-high aspect ratio scaffolding for epitaxially grown thermoelectric materials, so that thin films can be shaped into materials thick enough for practical devices. The self-limiting nature of atomic layer deposition (ALD) makes it an ideal growth technique for this substrate, as uniform thickness can be obtained at all points inside the macroporous structure, and we demonstrate successful deposition of antimony telluride on pore walls using ALD. Extension of this work to telluride superlattices should enable fabrication of thermoelectric devices with figures of merit (ZT) in excess of 2. Characterization of the thermoelectric and other properties of ALD grown telluride on silicon is ongoing.

In situ photodeposition techniques taking advantage of the TiO2 photocatalysis have been developed for coupling metal sulfide quantum dots (QDs) and TiO2 at a nonoscale. The coupled metal sulfide-TiO2 systems possess the following characteristics: (I) a large amount of metal sulfides can be directly formed on TiO2 during a fairly short period with excellent reproducibility, (II) the band energies of metal sulfides QDs are widely tunable by irradiation time, (III) metal sulfide QDs can be deposited on not only the external surfaces but also the inner ones of mesoporous TiO2 nanocrystalline films without pore-blocking, (IV) the simple solution-based technique at low temperature enables the low-cost production, (V) this technique has a wide possibility for coupling TiO2 and narrow gap metal sulfides. These unique features produce the excellent performances of the resulting heteronanojunaction systems as the photoanodes for QD-sensitized solar cells.

We present transport properties of silicon nanowires field effect transistors realized on SOI substrates and their application to probe electrical activity of biological objects. Devices are sensitive to short and weak voltage pulses (ms, mV) applied in an electrolyte solution, allowing a future efficient detection of neuronal activity. For that purpose, the organized growth of neuronal cells along chosen patterns has been obtained, leading to an accurate coupling with silicon nanowire field effect transistors. Both network architectures, neural and semiconducting, have been designed to study some aspects of the propagation and the processing of information by the nervous system.

This work describes the fabrication of highly sensitive graphene-based field effect transistor (FET) biosensors in a cost-effective way and its application in label-free DNA detection. CVD graphene was used to achieve mass production of FET device through photolithography method. Non-covalent functionalization of graphene with 1-Pyrenebutanoic acid succinimidyl ester ensures the high conductivity and sensitivity of the device. The present device could reach the low detection limit as low as 3*10-9 M.

This paper describes the development of nanomonitors, which are electrical immunoassays for detection of multiple protein biomarkers. These devices are hybrid sensors with micro-fabricated electrode arrays on a silicon substrate, and integrated nanoporous alumina membranes to provide protein confinement and signal amplification. The disease biomarkers C-reactive protein and Myeloperoxidase have been detected by the nanomonitors in ultra-low concentrations. Proteins were detected in pure samples, human serum, and patient blood samples. The detection accuracy and sensitivity of the nanomonitors in patient samples was comparable to the Enzyme Linked Immunosorbent Assay (ELISA) method of protein detection. Nanomonitors provide the additional benefits of being rapid, label-free, sensitive, and cost effective, providing improvements over traditional protein detection methods, and having potential applications in disease diagnosis.

The present work reports the synthesis of self-organized strontium-doped titania nanotubes arrays as a potential material for photocatalytic water splitting. Electrochemical anodization process was used to grow such material under various electrochemical conditions. The effect of dopant concentration on the morphology and photoelectrochemical properties of the material was investigated. The microstructure, morphology and composition of as-prepared and heat treated nanotubes were characterized by field emission scanning electron microscopy (FESEM), x-ray diffraction (XRD), transmission electron microscopy (TEM) and x-ray photoelectron spectroscopy (XPS). The results showed that increasing the dopant concentration up to its solubility limit results in higher photoelectrochemical activity. A preliminary proof of concept of the photocatalytic activity of the fabricated material was estimated in terms of the use of such material as a photoanode for photoelectrochemical water splitting.

Selected properties of the lanthanum zirconate (La2Zr2O7, LZ) low-index faces, representing the first theoretical attempt to characterize the surfaces of a pyrochlore oxide, as well as oxygen (O2) interacting with LZ are predicted at the level of density-functional theory. All possible surface terminations formed by cleaving a perfect crystal are considered, as well as selected defective surfaces. After deriving the expression for the free energy of an LZ surface, surface free energies are computed. The most stable surfaces are identified, and it is suggested how to refine the ratios of surface free energies for comparison to experimental results obtained by the analysis of x-ray diffraction (XRD) patterns. The interaction of O2 with selected faces is examined. A strong dependence of the binding energy on surface oxygen content is predicted.

Graphene is a promising candidate material for thermal management of high-power electronics owing to its high intrinsic thermal conductivity. Here we report preliminary results of the proof-of-concept demonstration of graphene lateral heat spreaders. Graphene flakes were transferred on top of GaN devices through the mechanical exfoliation method. The temperature rise in the GaN device channels was monitored in-situ using micro-Raman spectroscopy. The local temperature was measured from the shift in the Raman peak positions. By comparing Raman spectra of GaN devices with and without graphene heat spreader, we demonstrated that graphene lateral heat spreaders effectively reduced the local temperature by ~ 20oC for a given dissipated power density. Numerical simulation of heat dissipation in the considered device structures gave results consistent with the experimental data.

As many reports show that the superlattice structure could greatly enhance the figure of merit ZT value for the thermoelectric application. We studied the thermal and electrical properties of the InGaN/GaN superlattice structure, and further analyze the thermoelectric features with different superlattice period, doping concentration, and operation temperature. The elastic continuum model and Callaway model have been applied to calculate the phonon dispersion relation and the thermal conductivity, respectively. The electrical properties are obtained by the Boltzmann transport equation with the relaxation time approximation. Simulation results indicate that both the reduced thermal conductivity and enhanced power factor would have the contribution to the enhancement of the figure of merit ZT.

Two-body interatomic potentials in the Morse potential form have been developed for bismuth telluride, and the potentials are used in molecular dynamics (MD) simulations to predict the thermal conductivity of Bi2Te3 bulk, nanowires and few-quintuple thin films. The density functional theory with local density approximations is first used to calculate the total energies for many artificially distorted Bi2Te3 configurations to produce the energy surface. Then by fitting to this energy surface and other experimental data, the Morse potential form is parameterized. Molecular dynamics simulations are then performed to predict the thermal conductivity of bulk Bi2Te3 at different temperatures, and the results agree with experimental data well. We also predicted the thermal conductivity of Bi2Te3 nanowires with diameter ranging from 3 to 30 nm with both smooth (SMNW) and rough (STNW) surfaces. It is found that when the nanowire diameter decreases to the molecular scale (below 10 nm, or the so called "quantum wire"), the thermal conductivity shows significant reduction as compared to bulk value. We find the dimensional crossover behavior of thermal transport in few quintuple layer (QL) thin films at room temperature, and we attribute it to the interplay between phonon Umklapp scattering and boundary scattering. Also, nanoporous films show significantly reduced thermal conductivity compared to perfect thin films, indicating that they can be very promising thermoelectric materials.

Assembly of nanoparticles from bioactive peptides, caseinophosphopeptides (CPPs) and chitosan (CS) at physiological conditions and various CS/CPPs mass ratios have been systematically studied using a combination of turbidimetric titration, dynamic light scattering (DLS), electrophoretic mobility (zeta-potential) and transmission electron microscopy (TEM). Peptides, incorporated with CS forming nanoparticles, have already been prepared and identified using liquid chromatography-tandem mass spectrometry (LC-MS-MS). They are characteristic with different amount of clusters of phosphorylated seryl residues. At low salt concentration, an increase of CS/CPP mass ratio shifted the critical pHϕ1, which designated the formation of CS/CPP nanocomplexes, as well as pHmax, representing the neutralization of positive and negative charge to higher pH values. The peptide-polymer binding mechanism was analyzed according to the results of DLS, electrophoretic mobility, and TEM. First, negatively charged CPPs absorbed to positively charged CS molecular chain to form intrapolymer nanocomplexes saturated with CPPs (CPPNP). Then, the negatively charged CPPNP was bridged by added positively charged CS. Finally, novel nano-scaled spherical brushes were formed as additional CS molecule absorbed back to and bound the CPPNP. Phosphorylated groups in the CPPs might be the dominant sites for interaction with –NH3+ on the CS molecular chain.

The lithium titanate Li2Ti6O13 has been prepared from Na2Ti6O13 by Li ion exchange in molten LiNO3 at 325ºC. Chemical analysis and powder X-ray diffraction study of the reaction product, respectively, indicate that total Na/Li exchange takes place and the Ti-O framework of the Na2Ti6O13 parent structure is kept under those experimental conditions. The electrochemical characterization shows that Li2Ti6O13 is able to insert ca. 5 Li per formula unit under equilibrium conditions in the voltage range 1.5-1.0 V vs. Li+/Li. This corresponds to a specific discharge capacity of 250 mAh g-1. Lithium insertion occurs at an average equilibrium voltage of 1.5 V which is typical for oxides and titanates where Ti(IV)/Ti(III) is the active redox couple. After the first redox cycle a high reversible capacity is obtained (ca. 160 mAh g-1 at C/12, with a 70% capacity retention related to a phase transformation upon cycling). On the basis of these results, we are proposing Li2Ti6O13 as new lithium battery anode material to be further investigated.

Oxidized single-walled carbon nanotubes (SWNTs) have been prepared following a widely reported two-step purification/oxidation procedure in the presence or absence of a treatment with base (NaOH). The oxidized nanotube samples washed with solvents or base appear close to identical with respect to both appearance and properties. Efficient removal of both metal and carbonaceous impurities and introduction of –COOH groups on the nanotube surface have been demonstrated by AFM, Raman and FTIR spectroscopy. Furthermore, persistence of optical properties was confirmed using UV-vis/NIR absorption and NIR photoluminescence spectroscopies.

Homogeneous composite thin films of Fe2O3-carbon nanotube were synthesized in a novel, single-step process by metalorganic chemical vapor deposition (MOCVD) using ferric acetyl acetonate as precursor. The deposition of composite takes place in a narrow range of CVD conditions, beyond which the deposition either multiwall carbon nanotubes (MWNTs) only or hematite (α-Fe2O3) only takes place. The composite film formed on stainless steel substrates were tested for their supercapacitive properties in various aqueous electrolytes.

An automated technique for the mapping of nanocrystal phases and orientations in a transmission electron microscope (TEM) is briefly described. It is primarily based on the projected reciprocal lattice geometry that is extracted automatically from precession electron diffraction (PED) enhanced spot patterns. The required hardware allows for a scanning-precession movement of the primary electron beam on the crystalline sample and can be interfaced to any newer or older mid-voltage TEM. Comprehensive open-access crystallographic databases that may be used in support of this technique are mentioned.

More than 100 science and mathematics teachers have participated in the ASU Math and Science Teaching Fellows program for summers in 2007-2010 at Arizona State University. The goal of the program was to expose the teachers to the real world of science and help them transfer the experience into the classroom. The teachers spend the mornings in small groups in assigned research laboratories and afternoons in whole group interactive sessions. During the afternoon sessions the teachers worked on a poster presentation and a classroom unit integrating the research experience. The present study focuses on the impact of the research experiences on the teachers’ classrooms and the differences between a larger and longer program (37 teachers for 5 weeks in 2009) and a smaller and shorter program (8 teachers for 4 weeks in 2010). The lesson plans were coded based on a rubric. The posters were coded using qualitative analysis software. The scores on the lesson plans and the frequency of codes on transfer to classroom were higher in 2010 compared to those in 2009. The results indicate that the research experience program had a better impact on transfer to school curriculum with a smaller cohort of teachers. This implies that future research experience programs should be designed for smaller groups of teachers.

Large amounts of bronze weapons have been unearthed from the pits of the Terracotta Warriors. Though they are of the same period, their condition is quite different; some are slightly corroded; some have almost no corrosion with a gray-black or green-gray surface; some are badly corroded. ICP, XRD, SEM, EDX, XRF, AES and Metalloscope were employed on seven bronze weapons to investigate their composition, structure and differences between the surfaces and bulk metals. Results showed that all these bronze weapons are high-tin bronzes. The three bronze swords contain a higher tin content than the others and have undergone heat treatment, which gives them the necessary tenacity of weapons. The surface layers of the weapons are rich in tin in various degrees because of selective corrosion and the migration of copper ions during corrosion. Some objects are more corrosion-resistant by a quenching treatment and the formation of compact tin oxides.

In this study, we investigate directly bonded germanium-silicon interfaces to facilitate the development of high quality germanium silicon integration for Avalanche photodiode application. Angle resolved x-ray photoelectron spectroscopy data is presented which provides the chemical composition of the germanium surfaces as a function of the surface passivation. The hetero-structure is characterized by measuring forward and reverse current and comparing the measured results to TCAD simulation. The physical structure of hetero-junction is supported by high resolution transmission electron microscopy.

Elimination of degenerate epitaxy in the growth of icosahedral boron arsenide (B12As2, abbreviated as IBA) was achieved on m-plane 15R-SiC substrates and 4H-SiC substrates intentionally misoriented by 7 degrees from (0001) towards [1-100]. Synchrotron white beam x-ray topography (SWBXT) revealed that only single orientation IBA was present in the epitaxial layers demonstrating the absence of twin variants which dominantly constitute the effects of degenerate epitaxy. Additionally, low asterism in the IBA diffraction spots compared to those grown on other SiC substrates indicates a superior film quality. Cross-sectional high resolution transmission electron microscopy (HRTEM) and scanning transmission electron microscopy (STEM) both confirmed the absence of twins in the IBA films and their high quality. The ease of nucleation on the ordered step structures present on these unique substrates overrides symmetry considerations that drive degenerate epitaxy and dominates the nucleation process of the IBA.

In this paper, we present layer-by-layer stacking method to fabricate self-assembled structures of block copolymers (BCP) toward the out-of-plane direction. Layer-by-layer stacking is realized by transferring a BCP film on one substrate to another. Specifically, a water-soluble polymer film is coated on the former substrate, which is placed and fixed in contact with a target substrate. Consequently, the BCP film is released from the substrate and transferred to the target substrate when immersed in de-ionized water. In our experiment, PS-b-PMMA is used to form and transfer self-assembled structures, and polyvinyl alcohol is used as a water-soluble polymer. We prepared two kinds of target substrates; one has horizontal cylindrical structures by BCP self assembly, and the other has groove structures by EB lithography. In the case of BCP patterned substrate, BCP film with vertical cylindrical structures is transferred onto the line structures of BCP. In the case of EB lithography patterned substrate, BCP film with vertical cylindrical structures is transferred in a doubly suspended condition. Furthermore, vertical and horizontal cylindrical structures are also observed to align along the grooves.