Directional selective optical filters increase the photon confinement of solar cells with a Lambertian light-trapping scheme. These filters restrict the transmission of incoming sunlight to a cone of limited acceptance angle. This paper models the efficiency gain or loss caused by an ideal directional and energy selective filter on top of a solar cell, and compares it to a cell with Lambertian surface and a planar absorber. The enhancement of light trapping by the directional filter is illustrated by the enhancement of the quantum efficiency of normally incident light. Simulations of the annual yield demonstrate that the improved light trapping results in an overall energy gain of more than 10 % for a tracked system.To achieve this gain at the equator,a filter with small acceptance angle of 5 ° that is active below the threshold energy ˜1.5 eV has to used.

Cellulose electro-active paper (EAPap) has attracted much attention as a new smart electronic material to be utilized as mechanical sensors, bio compatible applications and wireless communications. The thin EAPap film has many advantages such as lightweight, flexible, dryness, biodegradable, easy to chemically modify, cheap and abundance. Also EAPap film has a good reversibility for mechanical performance, such as bending movement, under electric field. The main actuation mechanism governed by piezoelectric property can be modulated by material direction and stretching ratio during process. In this paper we present the overview as well as fabrication process of cellulose EAPap as a novel smart material. Also we propose the method to enhance the piezoelectricity, its mechanical and electromechanical properties. In addition, the fabrication of high quality metal patterns with Schottky diode on the cellulose surface is an initiating stage for the integration of the EAPap actuator and electronic components. The integration of flexible actuator and electronic elements has huge potential application including flying magic carpets, microwave driven flying insets and micro-robots and smart wall papers.

Solar cells based on hydrogenated nanocrystalline silicon (nc-Si:H) have demonstrated significant improvement in the last few years. From the standpoint of commercial viability, good quality nc-Si:H films must be deposited at a high rate. In this paper, we present the results of our investigations on obtaining high quality nc-Si:H and a-Si:H films and solar cells over large areas using high deposition rate. We have employed the modified very high frequency (MVHF) glow discharge technique to realize high-rate deposition. Modeling studies were conducted to attain good spatial uniformity of electric field over a large area (15”×1”) MVHF cathode for nc-Si:H deposition. A comparative study has been carried out between the RF and MVHF plasma deposited a-Si:H and nc-Si:H single-junction and a-Si:H/nc-Si:H double-junction solar cells. By optimizing the nc-Si:H cell and the tunnel/recombination junctions, we have obtained an initial aperture-area (460 cm2) efficiency of 11.9% for a-Si:H/nc-Si:H double-junction cells using conventional RF (13.56 MHz) plasma deposition. The deposition rate was 3 Å/sec. Results on solar cells made with MVHF will also be presented.

Progress in the state of the art of nanofabrication now allows devices that may enable the experimental sensing of bubble nucleation in nanochannels, and the direct measurement of the bubble nucleation rate in nanoconfined water and other fluids. In this paper we report on two aspects in achieving this goal: 1) new molecular dynamics simulations of nanobubble formation in nanoconfined argon and water model systems and 2) an ultrasensitive nanofluidic device architecture potentially able to detect individual nanobubble nucleation events.

Colloidal lithography is a popular, non-conventional process that uses two–dimensional self-assembled monolayer arrays of colloidal nanoparticles as masks for techniques such as etching or sputtering. Initiated Chemical Vapor Deposition (iCVD) is a surface controlled process which offers unprecedented opportunity for producing polymeric layers grafted to substrates with dangling vinyl bonds and patterned through a colloidal template. We demonstrate a generic “bottom-up” process as an inexpensive and simple technique for creating well-ordered arrays of functional patterned polymeric nanostructures. These patterns were produced from thin polymer films of p(butyl acrylate) and p(hydroxyethyl methacrylate), and are robustly tethered to the underlying substrate, as demonstrated by their ability to withstand aggressive solvents. Furthermore, using capillary force lithography, we created topographical templates for large-scale orientation of the nanoparticle assembly. Through this “top-down” approach, for assisting the bottom-up assembly, we present a process for multi-scale patterning of functional polymeric materials, without the need for expensive lithography tools.

We report the growth and characterization of thin germanium-carbon layers grown directly on Si (111) by ultra high-vacuum chemical vapor deposition. The thickness of the films studied is 8-20 nm. The incorporation of small amount (less than 0.5%) of carbon facilitates 2D growth of high quality Ge crystals grown directly on Si (111) without the need of a buffer layer. The Ge1−xCx layers were grown in ultra high vacuum chemical vapor deposition chamber, at a typical pressure of 50 mTorr and at a growth temperature of 440 °C. CH3GeH3 and GeH4 gases were used as the precursors for the epitaxial growth. The Ge1−xCx films were characterized by atomic force microscopy (AFM), secondary ion mass spectroscopy, x-ray diffraction, cross-sectional transmission electron microscopy and Raman spectroscopy. The AFM rms roughness of Ge1−xCx grown directly on Si (111) is only 0.34 nm, which is by far the lowest rms roughness of Ge films grown directly on Si (111). The dependence of growth rate and rms roughness of the films on temperature, C incorporation and deposition pressure was studied. In Ge, (111) surface orientation has the highest electron mobility; however, compressive strain in Ge degrades electron mobility. The technique of C incorporation leads to a low defect density Ge layer on Si (111), well above the critical thickness. Hence high quality crystalline layer of Ge directly on Si (111) can be achieved without compressive strain. The fabricated MOS capacitors exhibit well-behaved electrical characteristics. Thus demonstrate the feasibility of Ge1−xCx layers on Si (111) for future high-carrier-mobility MOS devices that take advantage of high electron mobility in Ge (111).

The present letter describes a reliability study of the micro-electromechanical system fabrication with a photoresist layer used as sacrificial layer with an aluminum beam deposited by means of RF sputtering method. This work reports changes of the roughness and planarity of the sacrificial layer beneath the aluminum film following the sputtering deposition. Such changes may be attributed to the alteration of the photoresist properties due principally to the outgassing of hydrogen by decomposition of C-H bonds under argon plasma. A safe deposition parameters area was identified where the photoresist layer keeps its properties and may be used as sacrificial layer.

Nanoscale apertures that provide a fluidic path between two reservoirs can be used for numerous applications.These applications include patch-clamp type measurements, Coulter counting and molecular studies. For Coulter counting of nanometer-sized analytes, we have developed a process capable of reproducibly fabricating cylindrical apertures in a silicon-on-insulator substrate with diameters less than 30 nm. The fabrication process utilizes electron beam lithography for the lithographic definition of the apertures enabling accurate control of final device dimensions. Measurements of the conductance of the pores as a function of KCl concentration reveal the presence of a surface conduction mechanism that dominates the conductance of the nanopore and leads to a deviation of the concentration dependence of the conductance from the case of bulk solution. From current traces recorded, the passage of individual particles through the pore can be concluded.

Variable temperature electrical measurement is well-established and used for determining the conduction mechanism in semiconductors. There is a Meyer¡VNeldel relationship between the activation energy and the prefactor with a Meyer¡VNeldel energy of 30.03 meV, which corresponds well with the isokinetic temperature of about 350 K. Therefore, the multiple trapping and release model is properly used to explain the thermally activated phenomenon. By the method, an exponential distribution of traps is assumed to be a better representation of trap states in band tail. Samples with higher temperature during measurement are observed to show better mobility, higher on-current and lower resistance, which agree well with the multiple trapping and release model proposed to explain the conduction mechanism in pentacene-based OTFTs.

A candidate hydrogen storing material should have high storage capacity and fast dehydrogenation kinetics. On this basis, magnesium hydride (MgH2) is an outstanding compound with 7.6 wt% storage capacity, despite its slow dehydriding kinetics and high desorption temperature. Therefore in this study, formation energies of alloyed bulk MgH2, adsorption energies on alloyed magnesium (Mg) and MgH2 surface structures were calculated by total energy pseudopotential methods. Also, the effect of substitutionally placed dopants to the dissociation of hydrogen molecule (H2) at the surface of Mg was investigated via Molecular Dynamics (MD). The results show that 31 out of 32 selected dopants decreased the formation energy of bulk MgH2, within a range of ˜37 kJ/mol-H2 where only Sr did not display any such effect. The most favorable elements in this respect are; P, K, Tl, Si, Sn, Ag and Pb. Moreover, surface adsorption energy values display that all elements are adsorbed substitutionally on the clean (0001) surface of Mg where adsorption on MgH2 (001) surface is possible only for alloying elements other than Zn, Au, In, Ag, Li, Tl, Cd, Na and K. Finally, results of MD simulations point out that the elements giving rise to the dissociation of hydrogen molecule came out to be Ti, V, Cr, Mn, Fe, Co, Ni, Zr, Nb, Mo, Ru, Rh ve Hf.

We report a novel finding of slither propagation of shear bands on the fracture surface of a Cu47.5Zr47.5Al5 bulk metallic glass (BMG). The nanoscale heterogeneities in the as-cast state are aggregated along shear bands with irregular morphology. Such heterogeneities create a fluctuating stress field during shear band propagation leading to a slither propagation mode. The slither propagation of 10 to 15 nm wide shear bands is effective to improve both the plasticity and the “work-hardening-like” behavior of BMGs if the size, the morphology, and the elastic properties of the heterogeneities are intimately intercalated during solidification.

Bi2223 multifilamentary tapes with enhanced transverse resistivity by introducing Ca2CuO3 and SrZrO3 as interfilamentary barriers were prepared and their AC loss properties were examined under AC external magnetic field. To improve the deformation properties of these oxide powders, 20-30wt% Bi2212 powders were mixed with them. The mixed oxide powders were introduced among the twisted Bi2223 filaments by using dip-coating method. AC loss properties under AC parallel or perpendicular field were measured and compared with the results for the tape without barriers. The loss measurements were carried out by changing both the amplitude and the frequency of external field. Based on the experimental results, the effect of barrier introduction on the loss reductions was discussed.

Within the scope of the long term behaviour of the R7T7 glass, which is the French nuclear glass, leaching and its coupling with transport mechanisms is studied. Experiments carried out on a SON 68 glass (inactive R7T7 type glass) model cracks in static basic conditions show a strong coupling between solution transport and glass leaching, depending on crack aperture. Moreover, gravity driven convective transport was evidenced for vertical model cracks, whereas only molecular diffusion was detected for horizontal model cracks under the same alteration conditions. In addition, an original device was developed to study the influence of temperature gradients on alteration kinetics as a convective driving force. These experiments show conclusively that thermally- or gravity-induced convective flow must be taken into account, even if such convective effects have not been established experimentally in neutral condition, which is more realistic condition for geological storage. A modeling, based on a porous geochemical software (HYTEC) accounting for both chemistry and transport, has been successfully applied to describe alteration within simple silicate glass cracks. It will be extended to study SON 68 glass model cracks, and more complex fracture networks.

Gold nanorods have a strong surface plasmon band at the near infrared region. The absorbed light energy is then converted to heat. Since near infrared light can penetrate deeply into tissue, gold nanorods are expected to be used as a contrast agent for bioimaging using the near infrared light and photosensitizers for photothermal therapy. The surface plasmon bands of intravenously injected the gold nanorods were directly monitored from the mouse abdomen by using a spectrophotometer equipped with an integrating sphere. The absorbance at 900 nm from PEG5,000-modified gold nanorods immediately increased after injection and reached a plateau. The injection of phosphatidylcholine-modified gold nanorods also increased the absorbance at 900 nm, but the absorbance decreased single exponentially with a 1.3-min half-life. To demonstrate photothermal tumor therapy, the PEG-modified gold nanorods were directly injected into subcutaneous tumors in mice, then, near infrared laser light was irradiated to the tumor. After the treatment, significant suppression of tumor growth was observed.

Trilayer concentric metallic-piezoelectric-metallic microtubes are fabricated by infiltrating porous Si templates with sol precursors. LaNiO3 (LNO) is used as the inner and outer electrode material and PbZrTiO3 (PZT) is the middle piezoelectric layer. Structure of the microtubes is characterized in details using scanning and transmission electron microscopy which are equipped with energy dispersive X-ray spectroscopy for elemental mapping. The hysteresis of a trilayered thin film structure of LNO-PZT-LNO is shown. This trilayered tubes might find applications in inkjet printing.

Several polymers show bending behavior on exposure to selected solvent systems. Either on emersion or evaporation of particular solvents, films can bend or curl within seconds. The response depends on the interaction between polymer chains and solvent molecules as well as the film geometry and surrounding temperature.

Structure property function relationships provide valuable guidelines for a systematic development of functional materials. It is demonstrated how an augmented bond valence (BV) approach helps to establish such relationships in solid electrolytes. In principle it permits to identify mobile species, transport pathways and provides estimates for ion mobilities. In this work we discuss ion conduction pathways in glassy Lithium metasilicate as an illustrative example. The required representative local structure model is derived from Molecular Dynamics simulations, which provides the opportunity to compare the bond-valence-based predictions from a static structure model with a comprehensive analysis of a complete simulation trajectory. It is shown that understanding the bond valence mismatch as an effective Morse-type interaction opens up a way for systematically analyzing ion transport pathways and for a generally applicable method with improved reliability to predict ion transport characteristics in solid electrolytes from the structure model.

As material processes move to the nanoscale, fine control of process chemistries becomes critical. Atomic Layer Deposition, Chemical Vacuum Deposition, and Selective Gate Oxidation, as well as fabrication of Carbon Nanotubes all need water vapor from 50 sccm (40mg/min) to below 1 sccm ( 0.8 mg/min). Water vapor can be used for oxidation, cleaning and annealing of the nanoscale devices and thin films.

At 0.8 mg/min, flow control of liquid water with a mechanical pump is difficult without pulsation. Because water is liquid at room temperature, a standard thermal mass flow controller for gas cannot be used. Instead bubblers are used. However, they do not provide consistent or repeatable delivery.They are affected by gas and liquid temperature, relative pressures as well as gas velocity, liquid height, thermal droop, and contamination build up.

RASIRC® has developed a new pervaporation device that selectively allows water to diffuse into a carrier gas stream. The liquid water never directly contacts the carrier gas, allowing for independent liquid and gas pressures. A nonporous, hydrophilic membrane provides very rapid diffusion of water vapor into the carrier gas stream. This allows for precise amounts of water vapor to be added to the carrier gas based solely on relative vapor pressures.

To validate the performance of the device at very low flow rates into both atmosphere and vacuum process pressures, a heated humidity probe was used. This device was able to measure flow rates of 1 to 200 sccm in both vacuum and atmospheric pressure. The experimental results were compared with the expected theoretical dew point to validate the procedure. The humidity probe was used to measure both long term stability of the device and the instantaneous response time. Experimental results were compared to the expected time needed to change the water vapor concentration in the test volume.

We present a systematic study on the correlation of hydrogen dilution profiles to structural properties materials and solar cell performance in nc-Si:H solar cells. We deposited nc-Si:H single-junction solar cells using a modified very high frequency (VHF) glow discharge technique on stainless steel substrates with various profiles of hydrogen dilution in the gas mixture during deposition. The material properties were characterized using Raman spectroscopy, X-TEM, AFM, and C-AFM. The solar cell performance correlates well with the material structures. Three major conclusions are made based on the characterization results. First, the optimized nc-Si:H material does not show an incubation layer, indicating that the seeding layer is well optimized and works as per design. Second, the nanocrystalline evolution is well controlled by hydrogen dilution profiling in which the hydrogen dilution ratio is dynamically reduced during the intrinsic layer deposition. Third, the best nc-Si:H single-junction solar cell was made using a proper hydrogen dilution profile, which caused a nanocrystalline distribution close to uniform throughout the thickness, but with a slightly inverse nanocrystalline evolution. We have used the optimized hydrogen dilution profiling and improved the nc-Si:H solar cell performance significantly. As a result, we have achieved an initial active-area cell efficiency of 9.2% with a nc-Si:H single-junction structure, and 15.4% with an a-Si:H/a-SiGe:H/nc-Si:H triple-junction solar cell structure.