Although epoxy-based polymers remain infrequently used as shape memory polymers (SMP’s), they are a promising base material for highly demanding applications due to their intrinsic physical properties and ease of processing. A series of epoxy SMP’s was synthesized with varying mechanical properties and with glass transition temperatures ranging from 31 to 93 °C, tunable via the variations of the molecular structures. The influence of chemical structures and physical properties of these epoxy SMP’s on their shape memory (SM) behavior is examined in detail along with the impact of the shape memory cycling conditions. While the results show that lower crosslink densities and/or higher molecular flexibility/mobility leads decreased SM performance, at low crosslink density the effect of molecular flexibility/mobility becomes dominant in influencing the SM response.

The use of an ion beam assist during the concurrent deposition of cubic materials can result in the growth of crystallographically oriented thin films. A model system, magnesium oxide (MgO), has been successfully used as a biaxially textured template film and develops texture in a different manner from that of other well-studied materials, like yttria-stablized zirconia. Here, we present data on the initial nucleation of biaxial texture in this model system using a novel in-situ quartz crystal microbalance (QCM) substrate combined with in-situ reflected high-energy electron diffraction (RHEED). Temporal correlation of mass uptake with the RHEED images of the growing surface can be used to elucidate the mechanism of texture development in these films. Experimental data shows that the initially polycrystalline MgO film develops biaxial crystallographic texture at a thickness of ˜2 nm, regardless of the ion-to-molecule ratio. RHEED images show the onset of texture occurs quickly and is somewhat analogous to a solid phase re-crystallization process with crystallite sizes of ˜3 to 4 nm. Imaging with transmission electron microscopy has corroborated these observations. Changes in the ion-to-molecule ratio can influence the crystallite size and affect the nucleation density of these films. Growth of these films on various substrates changes the sticking coefficient of the MgO and influences the nucleation density and film growth mode as well. This opens the possibility of using MgO and other materials to develop biaxially textured crystallites with a narrow, specified size distribution for nanoscale applications.

Poly(lactide) (PLA) and its copolymers degrade through hydrolysis into non-toxic and water soluble metabolic products in vivo. They are ideal materials for resorbable biomedical applications such as drug delivery and tissue engineering. However, these polymers are brittle and often need to be toughened. One of the most effective toughening methods is reactive blending, in which additives are dispersed into polymer matrices as small particles with strong bonding between the two materials. In this paper, we studied toughening poly(lactide-co-glycolide) (PLGA) through reactive blending with poly(trimethylene carbonate) (PTMC). We observed warm-like micelle or swollen warm-like micelle structures created during the reactive blending process with a twin screw extruder at high temperature. The micelle structures were orientated along the extrusion direction with their length ranging from 50 to 1000 nm and diameters about 50 nm. This structure could be produced only with a twin screw extruder. When a batch mixer was used, the PTMC additive (10 to 30 wt%) formed spheres with diameters on the order of 100-500 nm. The PLGA/PTMC copolymers formed in situ were responsible to this microstructure. The mechanical properties of this blend were significantly improved over the pure PLGA.

A multi-physics model encompassing chemical dissolution and mechanical abrasion effects in CMP is developed. This augments a previously developed multi-scale model accounting for both pad response and slurry behavior evolution. The augmented model is utilized to predict scratch propensity in a CMP process. The pad response delineates the interplay between the local particle level deformation and the cell level bending of the pad. The slurry agglomerates in the diffusion limited agglomeration (DLA) or reaction limited agglomeration (RLA) regime. Various nano-scale slurry properties significantly influence the spatial and temporal modulation of the material removal rate (MRR) and scratch generation characteristics. The model predictions are first validated against experimental observations. A parametric study is then undertaken. Such physically based models can be utilized to optimize slurry and pad designs to control the depth of generated scratches and their frequency of occurrence per unit area.

The field-induced phase transition driven by electric field was observed in poly(vinylidene fluoride – hexafluoropropylene) (P(VDF-HFP)) 90/10 wt% copolymers. Experimental results indicated that the electric field may remarkably affect the remanent polarization in terms of changing the D-E loop forms from double loops to single loop, starting from 68 MV/m, and completing at 216 MV/m. It was found that the remanent polarization as well as the piezoelectric constant d31 had a linear relationship with the poling electric field in above electric field range. Thus the magnetoelectric (ME) coupling coefficient ME in P(VDF-HFP)/Metglas laminates increased with the poling electric field. Moreover, the cyclic poled ME device demonstrated different peak d.c. magnetic bias field HDC on the ME - HDC curves from conventional room temperature poled ones. The peak ME coefficient obtained was 4 V/cm Oe.

Creation of superhydrophobic self-cleaning surfaces is an important objective for a variety of applications. Indeed, numerous routes to generate superhydrophobic surfaces have been proposed. In this paper, a facile way of forming superhydrophobic surfaces is reported that uses Au assisted HF/H2O2 etching of silicon wafers. The Au layer was deposited onto a silicon wafer via e-beam evaporation. By controlling the evaporation and etching times, the surface roughness can be manipulated and superhydrophobic surfaces with reduced light reflection can be generated. Contact angles were measured with a CCD camera equipped goniometer; these values determined the water repellency. Light reflection on the as prepared black surfaces was measured to assess the efficiency for low cost solar cell applications. This approach offers a new way both to theoretically study the surface roughness effect and to investigate engineering applications of self-cleaning surfaces in solar cells, MEMS, anti-bacteria coating, and microfluidic devices.

The influence of mechanical constraint imposed by device geometry upon the switching response of a ferroelectric thin film memory capacitor is investigated. The memory capacitor was represented by two-dimensional ferroelectric islands of different aspect ratio, mechanically constrained by surrounding materials. Its ferroelectric non-linear behaviour was modeled by a crystal plasticity constitutive law and calculated using the finite element method. The switching response of the device, in terms of remnant charge storage, was determined as a function of geometry and constraint. The switching response under applied in-plane tensile stress and hydrostatic pressure was also studied experimentally. Our results showed that (1) the capacitor's aspect ratio could significantly affect the clamping behaviour and thus the remnant polarization, (2) it was possible to maximise the switching charge through the optimisation of the device geometry, and (3) it is possible to find a critical switching stress at zero electric field and a critical coercive field at zero residual stress.

High crystallized thin InSb epitaxial growth directly on Si substrate was investigated by molecular-beam epitaxy (MBE). Experimental results indicated that suppressing the desorption of hydrogen atoms which terminated the dangling bonds of Si wafer surface and incorporation of As around the interface between film and Si substrate were the most important to obtained high crystallized InSb film. It could be achieved by the irradiation of As4 cluster beam onto the Si wafer just before film growth. Obtained thin InSb film showed mirror like surface, and its thickness was 0.7 μm. Its electron mobility was 47,600 cm2/V-s, and FWHM of HR-XRD rocking curve was about 300 arcsec. This InSb film on Si wafer was applied to Hall element, and it passed ordinary reliability tests.

Heterogeneous catalysts consisting of nanoparticles dispersed on an oxide support are a mainstay in industrial reactions, and are often made via thermal reduction of metal salts dispersed onto a pre-synthesized support. Herein we document a route towards the design of xerogel-supported nanoparticle catalysts by trapping compositionally-tuned polymer-stabilized nanoparticle precursors into sol-gel matrices. Such a route allows in principle for the tuning of the size, composition, architecture, and electronic properties of nanoparticle catalysts, which allows for the development of highly efficient and selective catalysts. As proof of concept we detail the synthesis of co-reduced PdAu nanoparticles in titania supports. The final materials are well-characterized by HRTEM and energy dispersive spectroscopy (EDS), which confirm the compositional uniformity of the nanoparticles. The importance of controlling calcination conditions in order to retain designed nanoparticle compositions is stressed; high temperature calcination conditions lead to a large degree of sintering and loss of compositional uniformity, while mild calcination temperatures can be used to retain nanoparticle compositions and sizes.

Concentration photovoltaic (CPV) systems are seen as a shortcut to achieve lower photovoltaic (PV) electricity costs/kWh. Within the available CPV configurations, V-trough systems are likely to succeed in the short term since they are less demanding in terms of tracking accuracy and due to their ability to make use of standard PV modules, a well-known and developed technology. However, silicon standard modules were initially designed to operate under 1 sun conditions, facing some challenges when integrated in CPV systems. The present work aims to demonstrate that such application is efficient up to a few suns and also to analyze possible accelerated modules degradation rates. For such analysis we have used a prototype based on the DoubleSun® technology: a 1.9x concentration V-trough system, integrating 2-axis tracking system and making use of conventional silicon modules.

A compact and uniform (Ti, Si, O, N)/Ti composite coating was fabricated on the surface of a NiTi shape memory alloy (SMA) (containing 50.8 at.% Ni) using plasma immersion ion implantation and deposition (PIIID) with radio-frequency (RF) magnetron sputtering. The coating and coated NiTi SMA were studied using various techniques. Analysis showed that the Ni content was drastically reduced on the surface of coated samples due to coating formation. This could greatly improve the biocompatibility of NiTi SMA. There was no TiO2 or TiN formation in the coating. The shape memory ability of NiTi SMA samples was no deteriorated by the coating process. The coating significantly improved the corrosion resistance and wear resistance of NiTi SMA and also rendered the material bioactive.

We have performed a detailed investigation of the molecular beam epitaxial (MBE) growth and characterization of InN nanowires spontaneously formed on Si(111) substrates under nitrogen rich conditions. Controlled epitaxial growth of InN nanowires (NWs) has been demonstrated by using an in situ deposited thin (˜ 0.5 nm) In seeding layer prior to the initiation of growth. By applying this technique, we have achieved non-tapered epitaxial InN NWs that are relatively free of dislocations and stacking faults. Such InN NW ensembles display strong photoluminescence (PL) at room temperature and considerably reduced spectral broadening, with very narrow spectral linewidths of 22 and 40 meV at 77 K and 300 K, respectively.

The nanocrystalline ZnO embedded Zr-doped HfO2 high-k dielectric has been made into MOS capacitors for nonvolatile memory studies. The device shows a large charge storage density, a large memory window, and a long charge retention time. In this paper, authors investigated the temperature effect on the reliability of this kind of device in the range of 25°C to 175°C. In addition to the trap-assisted conduction, the memory window and the breakdown strength decreased with the increase of the temperature. The high-k film's conductivity increased and the nc-ZnO's charge retention capability decreased with the increase of temperature. The nc-ZnO retained the trapped charges even after the high-k film broke down and eventually lost the charges at a higher voltage. The difference between these two voltages decreased with the increase of the temperature.

Introducing a hydrophobic property to vertically aligned hydrophilic metallic nanorods was investigated experimentally and theoretically. First, platinum nanorod arrays were deposited on flat silicon substrates using a sputter Glancing Angle Deposition Technique (GLAD). Then a thin layer of Teflon (nanopatches) was partially deposited on the tips of platinum nanorod at a glancing angle of  = 85° as well as at normal incidence ( = 0°) for different deposition times. We show that GLAD technique is capable of depositing ultrathin isolated Teflon nanopatches on selective regions of nanorod arrays due to the shadowing effect during GLAD. Contact angle measurements on Pt/Teflon nano-composite have shown contact angle values as high as 138°, indicating a significant increase in the hydrophobicity of originally hydrophilic Pt nanostructures. Finally, a 2D simplified wetting model utilizing Cassie and Baxter theory of heterogeneous surfaces has been developed to explain the wetting behavior of Pt/Teflon nanocomposite.

Large area deformable macroelectronics, such as flexible display, smart bandage, electronic textile, have to withstand various modes of deformation (e.g., bending, twisting and stretching). Such electronic systems usually are composed of inorganic parts with limited deformability, and organic parts which can sustain large deformations. Because of the elastic nature of elastomers, these materials are often used as substrates for the specific applications mentioned above. In order to fulfill the demand of deformability, many concepts have been developed. One of these concepts consists of small rigid islands with active devices or individual thin chips which are interconnected by thin metal conductor lines. All rigid components are placed on the small islands to ensure that the strains acting on these brittle components are small when the structure is subjected to a large deformation. Since the thin conductor lines have to withstand all these deformations, a proper structural design is necessary to avoid losing structural integrity and electrical functionality during this deformation.Several technologies have been proposed in recent years, such as in-plane patterned metal conductors, out-of-plane wrinkling metal films, and conductive polymers or liquid alloys. It has been reported that by depositing a thin metal strip with a thickness of few nanometers on an elastomeric substrate, the elongation of the metal can go up to 50% while the strip remains conductive. Upon large strain, the elastic deformation of the elastomeric substrate causes local debondings of the metal film coevolving with strain localizations. Thanks to this coevolved process, even a �straight� line, deposited on a polymer substrate, is stretchable. However, a drawback of this unique characteristic is that the resistance of the thin metal film changes with elongation, which might be a disadvantage for certain applications. Another approach for having a stable resistance is to use bulk metal conductors. Compared to a freestanding bulk metal straight line which ruptures at strains of 1%˜2%, an in-plane patterned horseshoe metal conductor can be stretched up to 100% with a stable resistance before electrical failure.This paper demonstrates a novel in-plane patterned zigzag structure, with resistance independent of elongation before metal rupture, which can be stretched beyond 40%. The advantage compared to the horseshoe is that due to the geometrical design, the in-plane zigzag structural interconnects can be applied in a fine pitch microelectronic device. The experimental observations by both scanning electron microscopy micrographs and resistance measurements show that there is no significant local necking in either the transverse or the thickness direction at the metal breakdown area. Micrographs and simulation results show that a debonding occurs due to the local twisting of a metal interconnect, out-of-plane peeling and strain localized at the crest of a zigzag structure.

Phosphorus and Boron doping effects on the microstructure of nanocrystallites in hydrogenated amorphous and nanocrystalline mixed-phase silicon films were investigated using Raman spectroscopy, secondary ion mass spectrometry, cross-sectional transmission electron microscopy, atomic force microscopy, and conductive atomic force microscopy. The characterizations revealed the following observations. First, the mixed-phase Si:H films can be heavily doped in ˜1021/cm3 by adding PH3 and BF3 in the precursor gases. Second, the intrinsic and doped films can be made in a similar crystalline volume fraction by adjusting hydrogen dilution ratio. The hydrogen dilution ratio is much higher for P-doped films than for the intrinsic film with the similar crystallinity. Third, the doping impacts the nanostructures in the films significantly. Nanograins aggregate to form cone-shaped clusters in the intrinsic and B-doped films but isolate and randomly distribute in amorphous tissues in the P-doped films. The cones in the intrinsic and B-doped films are also different. The cone-angle is smaller and the nanograin density is lower in the B-doped films than in the intrinsic films. These P- and B-doping effects on the nanocrystalline formation are interpreted in terms of diffusions of Si-related radicals during the film growth.

A promising new concept of a diamond amplified photocathode for generation of high-current, high-brightness, and low thermal emittance electron beams was recently proposed and is currently under active development. To better understand the different effects involved, we have been developing models, within the VORPAL computational framework, to simulate secondary electron generation and charge transport in diamond. The implemented models include inelastic scattering of electrons and holes for generation of electron-hole pairs, elastic, phonon, and charge impurity scattering. We will discuss these models and present results from 3D VORPAL simulations on charge gain and collection efficiency as a function of primary electron energy and applied electric field. The implemented modeling capabilities already allow us to investigate specific effects and compare simulation results with experimental data.

Nanowire (NW) arrays form spontaneously after high temperature annealing of a sub monolayer deposition of Pt on a Ge(001) surface. These NWs are a single atom wide, with a length limited only by the underlying beta-terrace to which they are uniquely connected. Using ab-initio density functional theory (DFT) calculations we study possible geometries of the NWs and substrate. Direct comparison to experiment is made via calculated scanning tunneling microscope (STM) images. Based on these images, geometries for the beta-terrace and the NWs are identified, and a formation path for the nanowires as function of increasing local Pt density is presented. We show the beta-terrace to be a dimer row surface reconstruction with a checkerboard pattern of Ge-Ge and Pt-Ge dimers. Most remarkably, comparison of calculated to experimental STM images shows the NWs to consist of germanium atoms embedded in the Pt-lined troughs of the underlying surface, contrary to what was assumed previously in experiments.

4 Nines (99.99%) Cd and Te were purified to the semiconductor grade 6 Nines ∼ 7 Nines purity materials by the distillation and the zone melting processes, in order to be used for the growth of CdTe single crystal. The CdTe single crystal of 100 mm in diameter and 18kg in weight was successfully grown by the traveling heater method (THM). The shape of the growth interface had the key role for the single crystal growth. The distribution of the Te inclusion size was measured by IR microscopy. The uniformity of mobility-lifetime products and energy resolution in the wafer were also evaluated. The CdTe X-ray flat panel detector (FPD) was developed using the THM grown CdTe single crystal wafer. The CdTe pixel detectors with 100 mm pixel pitch were flip-chip bonded with the C-MOS readout ASIC and lined up on the print circuit board to cover the active area of 77 mm × 39 mm. The evaluation results showed that the CdTe X-ray FPD is promising as the imager for the non-destructive testing.