Layers that enhance light scattering and Raman-scattering-based spectral modification for solar cell applications were investigated. Titanium-oxide based rear diffuse reflector were found to increase the long wavelength response of crystalline solar cells. Also particle within the Titanium-oxide produce a far greater Stokes and anti-Stokes shift when compared to bulk crystal counterparts. The anti-Stokes to Stokes shift ratio in these particle systems is also greater and increased with increasing probe or bias light intensity. When applied to solar cells these layers extend the red response and thereby increase the overall performance.

The SLIM-Cut process is a kerf-free wafering technique to obtain silicon substrates as thin as 50μm. The quality of the resulting material must be assessed to ensure that this innovative Si-foil approach does not jeopardize the potential efficiency of the final solar cell in terms of electronic activity, defect density and location. For that reason, we performed Microwave-Detected Photoconductance Decay (MW-PCD), Deep-Level Transient Spectroscopy (DLTS) and optical inspections after defect etching of the foils surface. Analyses indicate that SLIM-Cut generates crystallographic defects which create deep level traps that have a negative impact on the lifetime of the silicon foil. Nonetheless, a decrease of the thermal budget will lead to a reduction of plasticity and hence lower the amount of defects and increase the foil quality.

In the electrospinning process, fibers ranging from 50 nm to 1000 nm or greater can be produced by applying an electric potential to a polymeric solution [1, 2]. Our group has studied the fabrication of electro-spun Poly-caprolactone (PCL) nanofiber consisting of a range of fiber diameter (nm-um) and pore sizes. PCL is a biocompatible, FDA approved and biodegradable [3, 4] polymer. As a solvent we have used 2,2,2-trifluoroethanol (TFE) for its biocompatibility, conductivity and high dielectric constant. The electrospinning technique consists of a simple setup with a number of variables working in a complex and unpredictable way. The variables affecting fiber diameter are polymer concentration in the solution, flow rate, applied voltage, tip to collector distance, diameter of the needle/capillary, polymer/solvent dielectric constant etc. In our study we have found that concentration of the solution and molecular weight of the polymer are the most important parameters for forming the nanofibers and viscosity is important for the fiber diameter. To optimize so many variables to control the fiber diameter, we have used the factorial design method. The study is important for the fabrication of biomimetic scaffold for vascular implant and tissue engineering application.

We developed ultra-violet field-emission devices using rare-earth nitrides of Al1-x Gdx N grown by a reactive radio-frequency magnetron sputtering technique. The Al1-x Gdx N phosphor film excited by high-energy electrons shows a resolution limited, narrow intra-orbital luminescence from Gd3+ ions at 318 nm. The devise characteristics depend on injected current and acceleration voltage, which were analyzed by considering multiple excitation process of injected high-energy electrons.

In-situ doped Eu ions in GaN grown by Organometallic Vapor-phase Epitaxy (OMVPE) at different pressures were investigated under different excitation methods and through the use of the following experimental techniques: (1) resonant site-selective laser irradiation (2) electron beam excitation, and (3) a dual excitation using a combination of electron beam and laser irradiation. With these means, we have examined the difference in the excitation pathways that result from resonant laser and electron hole (e-h) pair excitation of Eu ions for two different distinct incorporation sites, which are responsible for most of the luminescence. We have obtained clear evidence that e-h pairs do not have the ability to excite all of the ions and that there is excitation trapping by defects involved in the Eu excitation.

An Investigation of the piezoresistive response of a metal-polymer composite based on nickel conductive filler in a polydimethylsiloxane (PDMS) insulating matrix for tactile sensor application is presented in this paper. Lacking a mechanical deformation, the prepared composites show no electric conductivity, even though the metal particle content is well above the expected percolation threshold. In contrast, when subjected to uniaxial compression, the electric resistance is strongly reduced. A variation of up to nine orders of magnitude was registered. The thickness of the insulating layer between particles decreases when the sample composite is compressed. Therefore, the electric conduction which is related to a tunneling phenomena, increases exponentially. This behavior is further enhanced by the presence of very sharp nanometric spikes on the particles surface which act as field enhancement factors. In the presented work, the piezoresistive behavior of the composite, the stability in time of the resistance value and the response to several cycles of compression and decompression are evaluated on samples with different physical parameters like nickel content, PDMS copolymer/curing agent ratio and thickness.

The performance of a co-integrated silicon pressure sensor for the 1-bar full scale range was optimized. A gain in signal of ca. 5% was calculated and verified by optimizing the piezoresis-tors position on the membrane. The influence of alignment errors between the backside cavity mask and the positions of the piezoresistors on the membrane’s front side were calculated. De-pending on the asymmetry, a maximal electrical signal deviation of 1% was found. The impact of underetching effects (KOH) at the backside mask on electrical signals was also analyzed. Un-deretching has a certain range, alters the membrane size, and has a strong impact on sensor per-formances. In a worst case scenario signal variations caused by underetching could be finally reduced from 15% to 4%.

This paper introduces a highly reliable Cu interconnect technology at the 32 nm node with CuMn alloy seed. A CuMn alloy liner seed process combined with a non-gouging liner has been integrated into the minimum-pitch wiring level. Stress migration fails with CuMn seed at plate-below-via structures were shut down by a non-gouging liner process. Integration with gouging liner and non-gouging liner is compared, and results of interaction with CuMn seed are discussed in this paper.

The surface of Indium-tin-oxide (ITO) substrate was modified with a newly designed silane coupling molecule bearing azobenzene moiety. The silane coupling molecules formed self-assembled monolayer (SAM) on pretreated ITO surface. The SAM growth and coverage were quantified by contact angle measurement and X-ray photoelectron spectroscopy (XPS). The silane coupling molecules improved the adhesion between the ITO surface and an amphiphilic block copolymer (BC) thin film, which consists of poly(ethylene oxide) (PEO) and poly(methacrylate) (PMA) with azobenzene mesogens, because the azobenzene moieties of the SAM anchor the liquid crystalline PMA azobenzene domains of BC.

We studied the electrical and optical responses of organic light-emitting devices (OLEDs) with green and red phosphorescent dyes doped in a polymer matrix to compressive stresses. The green OLED converted stresses as low as 6.8 kPa into measurable and reversible changes in both current density and electroluminescence (EL) intensity. The current showed a nearly linear characteristic response with sensitivity up to 205 μA kPa-1, whereas the EL intensity decreased by over three orders of magnitude at 107 kPa. In contrast, stress-induced modulations in current and light intensity were noticeable in the red OLED only above 160 kPa. The discrepancy has been attributed to different rates of stress-enhanced back exciton energy transfer between guest and host molecules, which quenches the EL of the green OLED, but has a much smaller impact on the performance of the red OLED. It is expected that similar green phosphorescent OLEDs built on large curved surfaces may directly image stress distributions and sense touch on a par with a human finger.

The modeling of single wall carbon nanotubes properties (length, diameter, chirality, defective wall structure) influence on sorption capability at different thermodynamic conditions (T= 80-273 К; P = 2-12 MPa) is presented in this work. The applied simulation procedure is the molecular dynamics as well the new event-driven simulation algorithm has been used. In the frameworks of this event-driven simulation algorithm the modeling of structure formation for carbon nanotubes have been done with different chirality and with wall defects presence. The analysis of obtained results and their comparison with published experimental and theoretical results are performed.

We present data on micrometer-scale localized single-pulse laser irradiation of Au, Cu, Al, or Ti films on borosilicate glass substrates. These metals represent a range of thermal properties, chemical reactivity levels, and relevance to specific applications. A mask projection technique employing a Q-switched Nd:YAG laser, emitting at its fourth harmonic of 266nm, was used to produce the irradiation spots in this work. The metal films, deposited by RF-sputtering, had thicknesses of several hundred nanometers. Sample irradiation was performed in either vacuum or ambient air, and the resulting microstructures were examined by electron microscopy. The results indicate that irradiation of Cu films can lead to the formation of bumps, sharp cones or protrusions. However, the controllability of these structures on Cu films is limited, compared to those formed on Au or Si. The results, upon irradiation of Ti films, are limited to melting and surface roughening or ablation openings, regardless of the conditions of irradiation, film thickness, substrate or ambient gas. The modifications that occur within Al films are reproducible, but limited in shape and size.

The mechanical properties and deformation behavior of each constituent layer of multilayered steel composites were examined using microtensile testing. Three-layered integrated steels consisting of SUS420 and SPCC (cold-reduced carbon steel sheets) were fabricated by a cold-rolling process. Different heat treatment processes were used to prepare three types of specimens (as-rolled, 823K-2 min heat-treated, and 823K-500 min heat-treated), and the effect of heat treatment on their mechanical properties was investigated. In the as-rolled specimens, the average tensile strengths in the SUS420 and SPCC layers were 1063 and 606 MPa, respectively, while in the specimens heat-treated for 500 min, they were 680 and 451 MPa, respectively. The tensile strength decreased with the increase in the heat treatment time. The tensile strength of the specimens was also calculated by using the rule of mixture. For the as-rolled specimens and the 823K-2 min heat-treated specimens, the calculated value was consistent with the measured value; however, for the 823K-500 min heat-treated specimens, the calculated value was lower than the measured value. This result suggests that the necking of this layered structure was effectively obstructed by the outer ductile layer. The micromechanical characterization technique used in this study is useful not only for investigating deformation behavior but also for designing multilayered steel composites with superior mechanical properties.

Exchange coupling observed recently in Fe/ Fe3O4 (001) junctions shows comparable intensity to that in Co/Ru/Co trilayers, and has potential applicability to spintronics devices. To clarify the mechanism of the exchange coupling, electronic and magnetic states of Fe/ Fe3O4 junctions are calculated in the first principles method by assuming four junction structures of bcc Fe and Fe3O4 layers. It is shown that the local moments of bcc Fe atoms at the interface increase, but those of Fe ions at the interface of Fe3O4 layer decrease. The total energy of the junctions is plotted as a function of distance between Fe and Fe3O4 layers. Calculated results of the coupling energy between Fe and Fe3O4 layers, however, are larger than experimental ones by two orders of magnitude, and they correspond to inter-atomic exchange interactions at the interface. In order to explain the experimental results, we propose a mechanism of exchange coupling mediated by impurity-like states of interfacial Fe atoms which possess reversed magnetic moments in bcc Fe layer. Frustration effects in exchange coupling between Fe and Fe3O4 layers are also discussed.

We report a novel system for sorting single wall carbon nanotubes (SWCNTs) by length via cross-flow filtration with three membrane filters of different pore sizes, 1.0, 0.45, and 0.2 μm. SWCNTs dispersed in water with the help of polymer type detergents, such as sodium carboxymethylcellulose (CMC) and polyoxyethylene stearyl ether (Brij 700), were successfully fractionated into four samples, and the atomic force microscopy (AFM) observation of those samples confirmed that their length distribution peaks are within the expected ranges from pore sizes of used filters. However, the result of the similar filtration process using a non-polymer detergent, sodium dodecylbenzenesulfonate (SDBS), showed no pronounced correlation between the length distribution of SWCNTs and the pore size. The observed difference in the sorting phenomena caused by the detergent type suggests that the permeation property depends on the complex structure resulting from the dispersed SWCNTs and detergent molecules.

Atomic Layer Deposition (ALD) is a gas phase deposition technique for depositing very high quality thin films with an unsurpassed conformality. The main drawback of ALD however is the very low deposition rate (~ 1 nm/min). Recently, record deposition rates for alumina of up to 1 nm/s were reached using spatial ALD, while maintaining the typical assets regarding film quality as obtained by conventional, slow ALD [1]. This allows for ALD at high throughput numbers.

One interesting application is passivation of crystalline silicon solar cells. Applying a thin alumina layer is reported to increase solar cell efficiency and enables the use of thinner wafers, thus reducing the main cost factor [2]. In this paper we report on the latest progress made by SoLayTec that delivered a working prototype of a system realizing full area single sided deposition of alumina on 156 x 156 mm2, mono- and multi crystalline silicon wafers for solar cell applications. The alumina layers showed excellent passivation. Based on this concept, a high-throughput ALD deposition tool is being developed targeting throughput numbers of up to 3000 wafers/hr. Finally, we report on the process of commercializing this technology.

ZnO TFTs with bottom gate top S/D contact architecture were fabricated by sputtering of ZnO with layer thicknesses from 30 nm to 100 nm. The effect of post deposition annealing in oxygen and forming gas atmospheres at 400°C to 500°C on the devices was investigated. The tendencies of a lower threshold voltage Vth and a higher saturation mobility μsat for higher annealing temperature can be observed for both oxygen and forming gas annealing. Reduction of trap density in oxygen annealing and additional hydrogen incorporation in forming gas annealing play an important role for these electrical parameters. Morphological changes of increased grain size and fewer grain boundaries in the channel also contribute to tendencies in electrical characteristics of ZnO TFTs.

Different types of biological adhesion can be categorized according to thelength scales, structures, and materials involved. The setal adhesion systemof the gekkonid lizards occupies a hierarchy of scales from the toes (~ 1cm) to the terminal spatular pads on the setal branches (~ 100 nm). Thisunique combination of scale and foot-hair morphology allow the animalrobust, controllable, and near-universal adhesion via van der Waalsattraction, but it is also apparent that the mechanical behavior of theβ-keratin plays an important role in an animal’s climbing ability.Experimental results show a four-fold increase in the viscoelastic losstangent of β-keratin, alongside a substantial increase in adhesion of setalarrays, over a range of relative humidity from 10 to 80%. A model ofsingle-spatular deformation predicts that the elastic energy stored in thesetal branches, energy which is not completely recovered on detachment, isstrongly influenced by these properties changes. The enhanced dissipationcharacteristics of the system explain the effects of environmental humidityon the clinging ability of geckos.