In this report, we studied the role of the oxygen concentration in TiOx layer of Ni/TiOx/TiO2/Ni stack based 2-terminal resistive random access memory (RRAM) devices. The sample with oxygen deficient TiOx layer showed Schottky diode type J-V characteristics in the as-fabricated state while the sample with higher oxygen content in TiOx demonstrated MIM or back-to-back connected diode behavior. The Capacitance-Voltage (C-V) profiling was performed and doping density vs. depletion width characteristic was obtained. The conductance technique was implemented to study the interface state density. The RRAM type switching behavior of these samples was studied. The sample with high oxygen in TiOx showed filament based switching after electroforming while the sample with low oxygen in TiOx showed switching governed by the charge trapping.

We apply a thin luminescent downshifting (LDS) coating to a hydrogenated amorphous Si (a-Si:H) solar cell and study the mechanism of possible current enhancement. The conversion material used in this study converts wavelengths below 400 nm to a narrow line around 615 nm. This material is coated on the front of the glass of the a-Si:H solar cell with a glass/TCO/p/i/n/Ag superstrate configuration. The initial efficiency of the solar cell without the LDS coating is above 9.0 % with open circuit voltage of 0.84 V. Typically, the spectral response below 400 nm of an a-Si:H solar cell is weaker than that at 615 nm. By converting ultraviolet (UV) light to red light, the solar cell will receive more red photons; therefore, solar cell performance is expected to improve. We observe evidence of downshifting in reflectance spectra. The cell Jsc decreases by 0.13 mA/cm2, and loss mechanisms are identified.

We present the synthesis of resorcinol-formaldehyde aerogels and carbon aerogels of different nanoporosities, emphasizing on the recent developments in fabrication pathways of lower cost. Recent results showed a simple way to the production of highly nanoporous carbon xerogels. While using an approach combined colloidal silica nanocasting and carbon dioxide supercritical drying, hydrophilicity-controlled carbon aerogels with high mesoporosity were synthesized. Then, we demonstrate the functions of these aerogels for template synthesis of hierarchically nanostructured zeolites having micropores and mesopores.

Systematic first-principles calculations based on density functional theory were performed on a wide range of Ln2TiO5 compositions (Ln = La, Ce, Pr, Nd, Sm, Gd, Tb, Dy and Y) in order to understand the correlation between structural, elastic and electronic properties. A complete set of elastic parameters including elastic constants, Hill’s bulk moduli, shear moduli, Young’s moduli and Poisson’s ratio, were calculated. All Ln2TiO5 are ductile in nature, and analysis of densities of states and charge densities suggests that the oxide bonds are highly ionic.

Electron backscatter diffraction (EBSD) provides information on the crystallographic structure of a sample, while scanning Kelvin probe microscopy (SKPM) provides information on its electrical properties. The advantage of these techniques is their high spatial resolution, which cannot be attained with any other techniques. However, because these techniques analyze the top layers of the sample, surface or cross section features directly influence the results of the measurements, and sample preparation is a main step in the analysis.

In this work we investigated different methods to prepare cross sections of CdTe/CdS solar cells for EBSD and SKPM analyses. We observed that procedures used to prepare surfaces for EBSD are not suitable to prepare cross sections, and we were able to develop a process using polishing and ion-beam milling. This process resulted in very good results and allowed us to reveal important aspects of the cross section of the CdTe films. For SKPM, polishing and a light ion-beam milling resulted in cross sections that provided good data. We were able to observe the depletion region on the CdTe film and the p-n junction as well as the interdiffusion layer between CdTe and CdS. However, preparing good-quality cross sections for SKPM is not a reproducible process, and artifacts are often observed.

We present an overview of the theory developed over the last few years to describe the crystallization of amorphous solids. The microstructure of the crystallizing solid is described in terms of the grain size distribution (GSD). We propose a partial differential equation that captures the physics of crystallization in random nucleation and growth processes. The analytic description is derived for isotropic and anisotropic growth rates and allows for the analysis of different stages of crystallization, from early to full crystallization. We show how the timedependence of effective nucleation and growth rates affect the final distribution. In particular, we demonstrate that for cases described by the Kolmogorov-Avrami-Mehl-Johnson (KAMJ) model applicable to a large class of crystallization processes a lognormal type distribution is obtained at full crystallization. The application of the theory to the crystallization of silicon thin films is discussed.

Cu2ZnSnS4 (CZTS), an emerging p-type quaternary chalcogenide, offers many potential advantages as an absorber material. Using factorial design of experiments approach, single stage Cu-Zn-Sn co-electrodeposition from aqueous solution followed by annealing is reported in this paper. Factorial experiments facilitate to study the effects of each factor on the response variable as well as effects of interactions between individual factors on the response variable. Selected factors include concentration of individual ionic species, time of sulfurization and amount of complexing agent, whereas CZTS phase, band gap, carrier concentration, open circuit voltage, and morphological characteristics are the response variables. A model has been developed to show and predict the domain for the best possible factors for CZTS based device fabrication.

The presented work aims for the development of optically-traceable intracellular nanodiamond sensors, where photoluminescence can be changed by biomolecular attachment/delivery event. High biocompatibility, small size and stable luminescence from its color centers, makes nanodiamond (ND) particles an attractive alternative to molecular dyes for drug-delivery and cell-imaging applications. In our work we study how the surface modification of ND can change ND luminescence spectra. This method can be used as a novel detection tool for remote monitoring of chemical processes in biological systems. We discuss photoluminescence (PL) spectra of oxidized and hydrogenated ND and a single crystal diamond, containing engineered NV centers. The hydrogenation of ND leads to quenching of NV- related luminescence and a PL shift due to changing of occupation from NV- to NV0 states. We model this effect using electrical potential changes at the diamond surface.

Foils from the ethylene-tetrafluoroethylene (ETFE) copolymer are used as transparent, humidity resistant and UV-stabile facade and roof coverings, e.g. for stadia, indoor swimming pools or greenhouses [1]. With pneumatically supported cushions, large translucent structures can be realized. Until now, they are assembled through a thermal welding process [2]. The development of welding techniques using laser irradiation is under way.

Laser welding of transparent polymer foils requires an optical absorber placed in the interface between the two welding pairs. Usually, dye molecules with absorption properties adapted to the laser wavelength are used as absorbers. At a well-defined temperature, the dye molecules will be chemically modified, and transparent laser welding seams can be achieved. To get reproducible laser welding results, a homogenous layer of absorbent molecules or materials at the welding interface have to be realized, which is often very hard to achieve by wet deposition of dye molecules dispersed in a solution.

In our contribution, we report on an inkjet printing system that can be mounted on a R2R manufacturing setup. The main challenge to this approach is to find the right ink that is compatible with this highly hydrophobic ETFE foil. Therefore, both the pretreatment of the substrate as well as the utilization of different inkjet technologies are dealt with in this contribution. It is demonstrated that the inkjet printing of a laser absorbent ink in a defined way onto the substrate is possible.

For quality assurance, an optical inspection system has been developed to ensure a proper deposition of material. This ensures the quality control for the inkjet printing process of the special functional material. In that part the results of the comparison of the use of a dedicated 14‑bit grey level CCD line camera is compared to a high quality webcam.

Laser irradiation of the foil with printed laser absorbent lines together with the untreated joining partner was performed by a continuous wave diode laser at a wavelength of 808 nm using a defocused laser spot. A nearly transparent welding seam was achieved. Mechanical tensile tests of the laser welding seams have demonstrated that their tensile strength is comparable to conventional thermal welding seams.

Hetero-interface between two oxides sometimes forms a dipole layer which is experimentally observable macroscopically, as an electric potential barrier at the interface. Investigation of the flatband voltage shift of the metal-insulator-semiconductor capacitors with bilayer oxides as the insulator is suitable to characterize the dipole formation at the interface of two oxides. A model to explain the driving force to form the dipole is discussed by taking account of the areal density difference of oxygen atoms at the interface, which should be a guideline to predict both the direction and magnitude of the interface dipoles. Based on this model the requirement for the oxides to form the dipoles is also discussed.

The configurations of proton channel network on the surface of Nafion® membranes were studied using current sensing atomic force microscopy after the membranes were annealed at elevated temperatures, aimed at understanding the effect of aging process in the membranes. The results reveal that proton conductance of the membranes becomes more uniform and the proton channels become chain-like aligning in parallel to the membrane surface. Accompanied to the configuration changes, the proton conductivity of the membrane shows an increase. As the annealing continues, the chain-like configuration for the proton channels persists but the conductance of the membranes decreases. The time constant of the conductivity decay decreases with increase of the annealing temperature. The observed changes can be attributed to reorientation of proton channels near the membrane surface from perpendicular to parallel to the surface as the annealing temperature approaches the glass transition of the membranes.

We describe an innovative and simple drop-cast processing strategy to create bonelike multicomponent bionanocomposite materials that consist of an organic poly(ε-caprolactone) (PCL) matrix, minerals such as hydroxyapatite (HAP) and CaCO3, and collagen fibers. The process allows morphological and structural control to achieve the desired nanostructure of the bone mimics. The fabrication method involves adding inorganic and organic components sequentially followed by controlling the growth conditions and composition. This enables organization of collagen nanofibers (∼ 100 nm) into scaffolds while simultaneously allowing nucleation and co-alignment of hydroxyapatite spheres (∼ 100 – 500 nm) within aligned, thermally stable collagen fibers in the porous PCL matrix. We achieved high calcium (26%) and oxygen (17%) within the bioscaffold and adequate phosphorous compositions comparable to the levels of bone tissues. Adequate mineralization along with high oxygen content may help maintain the required bone mineral density and revascularization for nutrient and compensate for the loss of oxygen delivered to the bone cells. Furthermore, since the bionanocomposite scaffold is made of natural materials (calcium, phosphorous and collagen) found in bone tissue, the formulation makes it an excellent biocompatible/biodegradable material. Our preliminary results suggest huge potential of these advanced bionanocomposite scaffolds for bone substitutes and tissue engineering applications.

Reflective display technologies aim to enable the delivery of dynamic digital content to devices that have the look and feel of ink on paper. We are presenting herein a novel device architecture design and proprietary electrically addressable inks, which enable low power, disruptive, print-like full color reflective display that can exceed the chromaticity represented by the Specifications for Newsprint Advertising Production (SNAP) standard. We are approaching the challenge of generating bright high-quality reflective color images from the perspective of printing by stacking electro-optic layers of subtractive colorants to address every available color at every location. Using in-plane optical effects, our novel media technology provides fast switching between clear and color states. Thin, flexible electronic media based on this technology has been fabricated by imprinting three-dimensional micro-scale structures with a continuous roll-to-roll (R2R) manufacturing platform. HP’s combination of novel device architecture, proprietary inks, and R2R manufacturing platform enables the required attributes for electronic media such as flexibility, robustness, low power, transparency, print-quality color, and scalability at low cost. The structure property relationship of surfactants has been carried out; their impact on performance of display devices has been studied. These results have been applied to improve the performance of electronic inks. We have demonstrated 3-layer stacked segmented reflective display prototypes, as well as pixelated stacked color reflective display prototypes. The innovations described in this paper are applicable to electronic skins for customizable electronic surfaces and are currently being developed further for electronic paper and signage markets.

We report evidence for graphene layer rearrangements in heavy ion interactions with carbon onions at 140 MeV and 70 MeV per nucleon kinetic energies. Graphene layer rearrangements have been recently predicted in spherical and cylindrical multi-layer graphene systems. The implications of graphene layer rearrangement on the tribological performance of multi-layer nano-carbons in extreme environments are discussed.

Sub-micrometer ferroelectric-gate field-effect transistors (FeFETs) of 0.56 μm and 0.50 μm gate lengths were successfully fabricated for Fe-NAND cells. Gate stacks of the FeFETs were Pt/SrBi2Ta2O9(SBT)/Hf-Al-O/Si. The gate stacks were formed by electron beam lithography and inductively coupled plasma reactive ion etching (ICP-RIE). Ti and SiO2 hard masks were used for the 0.56 μm- and 0.50 μm-gate FeFETs, respectively, in the ICP-RIE process. Steep SBT sidewalls with the angle of 85° were obtained by using the SiO2 hard masks while 76° sidewalls were shown using Ti hard masks. All fabricated FeFETs showed good electrical characteristics. Drain current hysteresis showed larger memory windows than 0.95 V when the gate voltages were swung between 1±5 V. The FeFETs showed stable endurance behaviors over 108 program/erase cycles. Drain current retention properties of the FeFETs were good so that the drain current on/off ratios did not show practical changes after 3 days.

Carbon-based materials like nanotubes and graphene are heavily investigated as future transistor devices and in interconnect applications. While much of the interest has been devoted to the device aspects in competition to conventional transistors, the paper here will focus on some less known applications of pyrolytically deposited carbon. Proposed and demonstrated are applications in capacitors, gate materials, through-silicon vias, novel non-volatile memories, carbon-silicon Schottky diodes and sensors.

Ion irradiation effects in nanowires are of increasing interest due to potential applications of the wires as e.g. current-carrying elements in transistors or as efficient light emitters. Although several experiments have already demonstrated such functionalities, very few theoretical studies on the fundamental mechanisms of ion irradiation have been carried out. To shed light on the basic mechanisms of nanowire irradiation, we have simulated 0.03- 10 keV Ar ion irradiation of Si nanowires with a < 111 >-oriented axis and with all side facets being < 112 >. We compare the results with those for Si surfaces and bulk. The results show that the damage production in the nanowire is strongly influenced by surface effects.

Hydrogen production from renewables such as bio-ethanol is one of the most promising processes for energy carriers in a sustainable way. In this work we review and compare two catalytic systems: one based on thermal activation over bimetallic catalysts (Rh-Pd/CeO2) and the other over photo-excited semiconductor catalysts (Au/TiO2 anatine, rutile and anatase/rutile). It is found that the hydrogen yield is far higher on the thermally activated catalysts (at 773K) when compared to that of the photo-exited catalysts (at room temperature); about 60 times. However, the photo-excited catalysts are a promising way to create a fully sustainable system for future applications if the complete removal of hydrogen atoms from water and ethanol are obtained at room temperature.

i-ZnO layers were deposited as diffusion barriers fabricated by RF sputtering on stainless-steel substrates (SUS430, matches with AISI SUS24). It was found that the addition of ZnO layer between stainless-steel substrate and Mo back contact film deplete diffusion of metal ions from substrate and reduce recombination at CIGS layer, as identified by an SIMS depth profile, QE and C-V measurements. With such diffusion barriers, the efficiency, open-circuit voltage, short-circuit current and fill factor of CIGS solar cells all increased, compared to reference cells without diffusion barrier. For the better device performance, Na was supplied during Mo back-contact layer deposition by co-sputtering of the target, including Na-source. Efficiencies of cells were increased with increasing the quantity of Na source. Unlike barrier thickness effect, short circuit current was reduced and open circuit voltage, fill factor were increased with increasing Na-source, and achieved 12.6% efficiency without AR(anti-reflection) coating. The relationship and causality between these results and the Na-doping were analyzed using C-V measurements.