Cu2ZnSnSe4 p-type semiconductors currently investigated for use in thin film solar cells can be synthesized by firstly depositing a metallic precursor and secondly annealing the precursor in selenium vapor. Differently stacked Cu-Sn-Zn metallic precursors were characterized after a soft annealing at 350°C under nitrogen atmosphere. For the stack where the Sn and Zn were in direct contact with sufficient Cu to form a stable alloy, a bi-layered structure consisting of Cu-Sn on the bottom and Cu-Zn on the top was formed. Contrarily, when Zn was not in direct contact with Cu, the metals diffused to form a stable alloy and the system segregates horizontally, forming a mixed columnar structure. These two types of precursors were selenized under exactly the same conditions to form kesterite absorbers for solar cell devices. Using this approach the improvement from 0.44% power conversion efficiency for the bi-layered precursor to 4.5% for the mixed precursor was achieved.

In the past 20 years, one of the best catalytic materials for hydrodesulphurization reactions of crude oil has been the transition sulfides, MoS2, known also as the “workhorse” of the refinery industry. It has been proven by this and other research groups that the MoS2 laminar structure can increase its catalytic activity when promoted with cobalt or nickel. The location of active sites seem to be at rim and edge sites on that particular laminar structure, as demonstrated using Mössbauer spectroscopy and x-ray techniques. However, due to maximum capability of this promoted systems, Co(Ni)/MoS2 to remove heterogeneous atoms (S, N, O) - a search for new catalytic materials has currently been an ongoing activity in the HDS community. Here, we will present the new family of ternary phase catalyst with special emphasis on their structural aspects, as revealed by aberration corrected (Cs) high-resolution transmission electron microscopy techniques, in an attempt to describe the nature of active sites on this porous nano-rod like catalytic materials.

This study demonstrates that thin metallic oxide layers, such as OsOx and ZnO, function as a strong adhesion layer between Cu film and glass substrate. The adhesion strength was studied with a micro-scratch tester and the films and interfaces were characterized by energydispersive X-ray spectrometry. The presence of an extremely thin intermixing layer was confirmed at the metal/glass interfaces. The formation of such an interfacial layer increased the adhesion strength significantly.

Our objective is to design nanostructured hybrid inorganic-biological materials using the selfassembly of functionalized nanotubes and lipid molecules. In this presentation, we summarize the multiple control parameters which direct the equilibrium morphology of a specific class of nanostructured biomaterials. Individual lipid molecules are composed of a hydrophilic head group and two hydrophobic tails. A bare nanotube encompasses an ABA architecture, with a hydrophobic shaft (B) and two hydrophilic ends (A). We introduce hydrophilic hairs at one end of the tube to enable selective transport through the channel. The dimensions of the nanotube are set to minimize its hydrophobic mismatch with the lipid bilayer. We use a Molecular Dynamicsbased mesoscopic simulation technique called Dissipative Particle Dynamics which simultaneously resolves the structure and dynamics of the nanoscopic building blocks and the hybrid aggregate. The amphiphilic lipids and functionalized nanotubes self-assemble into a stable hybrid vesicle or a bicelle in the presence of a hydrophilic solvent. We demonstrate that the morphology of the hybrid structures is directed by factors such as the temperature, the molecular rigidity of the lipid molecules, and the concentration of the nanotubes. We present material characterization of the equilibrium morphology of the various hybrid nanostructures. A combination of the material characterization and the morphologies of the hybrid aggregates can be used to predict the structure and properties of other hybrid materials.

Cadmium sulfide (CdS) films were deposited onto glass substrates by chemical bath deposition (CBD) from a bath containing cadmium acetate, ammonium acetate, thiourea, and ammonium hydroxide. The CdS thin films were annealed in argon (neutral atmosphere) or hydrogen (reducing atmosphere) for 1 h at various temperatures (300, 350, 400, 450 and 500 °C). The changes in optical and electrical properties of annealed treated CdS thin films were analyzed. The results showed that, the band-gap and resistivity depend on the post-deposition annealing atmosphere and temperatures. Thus, it was found that these properties of the films, were found to be affected by various processes with opposite effects, some beneficial and others unfavorable. The energy gap and resistivity for different annealing atmospheres was seen to oscillate by thermal annealing. Recrystallization, oxidation, surface passivation, sublimation and materials evaporation were found the main factors of the heat-treatment process responsible for this oscillating behavior. Annealing over 400 °C was seen to degrade the optical and electrical properties of the film.

Nanoporous gold is a material with many possible applications e.g. in catalysts, sensors and electrode materials. We studied the functionalization of the nanoporous gold with TiO2 particles. Aiming at the low temperature oxidation of CO, the nanoporous gold can be coated with TiO2 in order to enhance catalytic activity. Structure and distribution of the TiO2 on the gold surface are important structural features, which were investigated by transmission electron microscopy. The preparation of the porous gold was tested with focused ion beam - preparation, conventional Ar+ ion beam preparation of nanoporous gold embedded in epoxy and ultramicrotome preparation of nanoporous gold embedded in epoxy. Considering the beam damage on the structure and the contamination of the surface, ultramicrotome preparation turned out to be the best solution. It was shown, that the gold ligaments are abundantly covered by approximately 5 nm TiO2 particles. The determination of the largest lattice fringe distance in high resolution mode revealed that the crystalline nanoparticles consist of the anatase phase. The spatial Ti distribution was measured with energy filtered transmission electron microscopy. Scanning transmission electron microscopy tomography was applied to reconstruct the three-dimensional structure of the gold coated with TiO2 particles.

We contribute a fast numerical approach to simulating the roller-imprinting of complex patterns. The technique predicts the extent to which imprinted patterns are fully formed, as well as variation of the imprinted material’s residual layer thickness (RLT). The approach can be used for roll-to-roll and roll-to-plate configurations, and for rollers with or without elastomeric coatings. If patterns vary in pitch, shape or areal density across the roller, RLT and the completeness of pattern transfer can vary with position as well as with processing parameters, and our technique is able to model these effects. The technique has been successfully validated against published experimental data from two different roller-NIL processes: one involving an ultraviolet-curing resist film on a glass plate, and another involving a flexible thermoplastic web softened at its surface.

Spectroscopic Ellipsometry (SE) was chosen to study thin film growth in atomic layer deposition (ALD). It was shown that Cauchy model had limitations in predicting the ultrathin film thickness at initial few deposition cycles, and the fitting results depend on wavelengths range greatly. Effective Medium Approximation (EMA) model is capable of predicting ultrathin film’s physical properties. Our experiments on Al2O3 growth give supporting evidence on the applicability of EMA model, where it is used to successfully explain the initial nucleation and island like growth. EMA model can be extended to be used for Palladium thin film, which can give reasonable thickness and void content.

Effects of adding Erbium(Er) to Aluminum Nitride thin films on their structural and piezoelectric are reported along with stability of the films after annealing them at temperatures up to 600° C. The thin films samples were deposited on the (001) p-type silicon substrates by reactive magnetron sputtering, using the Er alloyed Aluminum targets with Er atomic concentrations of 0, 1, 3 and 4% and the magnetron sputtering power of 200 W. The samples were characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). XPS analysis was used to confirm the stoichiometry of AlN phase, Er atomic content and its possible chemical state in the films. Results show that alloying with Er results in higher piezoelectric coefficient d33 as compared to that in Er-free AlN thin films. Structural analysis of the films by XRD shows the shift of (0002) AlN peak to lower 2θ values upon Er doping, indicating the presence of uniform internal compressive stress.

Papers in the Appendix were published in electronic format as Volume 1534

Ternary nanocomposites of poly (lactic acid) (PLA) were produced by melt blending with two types of elastomers and five types of organoclays to obtain improved mechanical properties such as tensile strength, modulus and impact strength. One of the elastomers is a random copolymer of ethylene and glycidyl methacrylate (E-GMA) and the other one is a random terpolymer of ethylene-butyl acrylate-maleic anhydride (E-BA-MAH). Organically modified montmorillonites (OMMT) were utilized as nanofillers. XRD, DSC, tensile and impact tests were done on the injection molded samples. FTIR, SEM and TEM analyses are still in progress. As preliminary results, thermal analysis showed that the addition of compatibilizers and organoclays does not have a distinct effect on the thermal properties of the composites, and no evidence of nucleation activity of compatibilizers or organoclays was found. For all types of organoclays, the nanocomposites produced with E-GMA exhibited better mechanical properties in comparison to nanocomposites containing E-BA-MAH, especially for the impact strength.

Wehave investigatedthe thickness dependence of air exposure of copper phthalocyanine (CuPc) layerson molybdenum trioxide (MoO3) with ultraviolet photoemission spectroscopy (UPS). It was found that after the air exposure, the WF of MoOx dropped severely. Meanwhile, with ∼10 ÅCuPcthin films covered on the top, there is no big change of the MoOx WF before and after the air exposure.

To better understand the mechanisms of creation and rupture of conductive filaments in resistive switching devices such as Cu/TaOx/Pt, with Cu and Pt being the active and inert electrodes, respectively, a device with limited supply of active metal electrode has been manufactured and electrically characterized. The limited supply of active metal has been realized by depositing a thin (delta) Cu layer (δ-Cu), 6 nm and 12 nm thick, on TaOx, resulting in a Pt/δ-Cu/TaOx/Pt device structure. The limited active metal supply i) has a direct impact on the onresistance (Ron) of the Cu bridge, and leads, after several conventional set-reset cycles, to ii) pulsating behavior, when device turns on and off repeatedly, to iii) symmetric switching behavior with respect to applied voltage polarity, when the device can be set and reset both at positive and negative bias, and to iv) volatile switching behavior.

Applications that produce a large amount of heat, such as combustion engines, can benefit from high temperature thermoelectrics to reduce the amount of energy lost. Superlattice (SL) structures have shown reduced thermal conductivity at room temperature and below, suggesting applicability at high temperatures may be possible. This reduction could greatly increase the thermoelectric figure of merit. The Si/SiGe material system is studied here for high temperature application. Two growth temperatures of 300 C and 500 C are examined. Two superlattice periods were studied (8 nm and 20 nm) to determine the effects of lattice spacing on thermal conductivity. Laser Flash Analysis is applied to determine the thermal diffusivity, hence thermal conductivity, from 100 C to 500 C. Thermal diffusivity was found to be an order of magnitude lower than the constituent alloy at 100 C. Superlattice spacing and growth temperature showed little effect on the diffusivity within the error of this measurement.

A new three-dimensional cell shape index using the AFM height images of cells cultured on cell substrates was defined. The new cell shape index revealed quantitative cell spreading information of cells that is not included in the conventional cell shape index. The quantitative morphometry of rat cerebral cortical astrocytes cultured on four different kinds of cell substrates were investigated using the conventional and the new cell shape index, and the results were compared. The new cell shape index showed the quantitative astrocyte spreading and stellation behavior that agrees with the AFM height images of astrocytes.

The influence of higher processing temperatures on the formation reaction of Cu(In,Ga)(Se,S)2 thin films using a three step reactive annealing process and on the device performance has been investigated. High process temperatures generally lead to the formation of larger grains, decrease the amount of void formation and their distribution at the back Mo/Cu(In,Ga)(Se,S)2 interface, and lead to a much faster formation reaction that shortens the overall reaction process. However, high temperature processing also leads to a decrease in device performance. A loss in open circuit voltage and fill factor could be attributed to enhanced interface recombination processes for the samples fabricated at higher process temperatures, which itself may be caused by a lack of Na and subsequent poor passivation of interface defect states. The lack of Na resulted in a decrease in free charge carrier concentration by two orders of magnitude.

Papers in the Appendix were published in electronic format as Volume 1534

In this study the PANI/PHBV blends were prepared and thermal properties, crystallization behavior, microstructure of the blends were investigated. The PANI/PHBV blends were prepared by dissolution of PANI (emeraldine base doped with dodecylbenzenesulphonic acid, DBSA) and PHBV in chloroform and films were obtained by casting. PANI amount in the blend was varied from 0.1 to 1% wt. PANI/PHBV blends were characterized by FTIR spectroscopy and the thermal behavior were analyzed by differential scanning calorimeter (DSC) and thermogravimetric analysis (TGA). FTIR spectra of the pure PHBV and PANI/PHBV blend had similar peaks. However, blends spectra show an enlargement of bands, due interaction of the chain PANI with PHBV matrix. The crystallization behaviors were investigated using DSC, with at a scanning rate of 10oCmin−1. Curve of pure PHBV showed two melting peaks (159.1°C and 172.3°C). With the increase of PANI amount in the PHBV matrix, both of the melting peaks became wider and shifted to lower temperatures. The decrease trend of first and second melting points with increase of PANI amount, suggests a reduction in the crystallinity of the blends.

Studies of carrier motion in a variety of nanostructures have indicated that a modified Drude model can be applied, by considering carrier bound motion from backscattering mechanisms and localized oscillator modes. Based on the results of these studies a model of damped harmonic oscillation modes is suggested to evaluate transport parameters in piezotronic devices. Here, the case of a system subject to static and low frequency piezoelectric fields is considered which corresponds to typical working conditions of nanogenerators and, as a working example, the response of ZnO nanowires excited by sound waves is analyzed.