We observed significant reduction of thermal conductivity in semiconducting composite films of Si and molybdenum (Mo)-silicide nanocrystals (NCs). These films were synthesized by phase separation due to annealing at 700 -1000°C from sputtered amorphous Mo–Si alloy. Transmission electron microscope images showed that the NCs were grown to diameters of∼10 nm in the films by annealing at 800°C. Raman scattering spectra showed lower shift of peak positions of Si transverse optical (TO) phonon due to the confinement effect and the tensile stress. The electrical resistivity of the films was 0.17- 9 Ωm at room temperature and showed a semiconducting temperature dependence at 20-400 K. Thermal conductivity of the film was reduced to 4.4 W/mK by enhancement of phonon scattering at NC interfaces, suggesting that the composite film is promising as a high-efficiency Si-based thermoelectric material.

In this study Sr2+ diffusion along Ce0.8Gd0.2O2-δ (CGO) grain boundaries is investigated. Model samples with different grain boundary densities were prepared by different thin film tech-niques. Diffusion experiments were performed by annealing and subsequent ToF-SIMS analysis. The activation energy of grain boundary diffusion is determined as 492 kJ/mol, which is 2/3 of the bulk diffusion activation energy 739 kJ/mol, deduced from literature data [1-5].

The formation of an electrical blocking SrZrO3 layer due to grain boundary diffusion of Sr2+ through a CGO barrier layer may limit the long term stability of Solid Oxide Fuel Cells based on Zr0.85Y0.15O2-δ electrolytes and La0.58Sr0.4Co0.2Fe0.8O3-δ cathodes. The grain boundary diffusivity and the CGO grain boundary density highly influence the kinetic of the SrZrO3 formation. Aim of this study is to gain data for a prediction of the maximum lifetime of a SOFC system, limited by the increasing cell resistivity due to SrZrO3 formation. Specifications for the CGO barrier layer preparation concerning grain boundary density are determined.

Wireless communications such as those in cell phones are utilizing increasing chip design complexity. For example analog mixed-signal chips can contain RF capability which requires integrated inductors [1,2]. High performance RF designs are enabled by the use of thick Copper (Cu) and Aluminum (Al) wires (>3um). In particular, the quality factor of the inductor, which is the ratio of magnetic stored energy over average dissipation, is dependent on the metal thickness. High quality factors, can be achieved by using thick Cu inductors. In some applications, the total thickness of Cu in the inductor can be as much as 12 um.

The fabrication of thick Cu layers is in many ways easier than that of thin Cu layers. For example, there are no limitations in terms of lithography or liner and seed layer thickness. However, there are still challenges with fabrication due to stress. Cracking of the dielectric can occur, due to the mismatch in coefficient of thermal expansion between Cu and SiO2, and due to the thick Cu layers in the inductor stack. Both the layout and the processing must be optimized to ensure that cracking does not occur.

This paper will discuss current applications, inductor design, and the reliability challenges and solutions associated with thick Cu interconnects.

Results of finite element analysis of linked two and three scale levels tasks are presented. Fields of components of stress concentration tensor function for several models of unit cells of textile composite materials are presented too. Comparison of experimental and computational results of obtained effective properties was carried out and results of this research are introduced. The basis of this phenomenological approaches was made by Prof. N.S. Bahvalov and Prof. B.E. Pobedriya in 80's and finally this method was renovated by Prof. Yu.I. Dimitrienko at Bauman Moscow State Technical University at «Computational mathematics and mathematical physics» department. Computational procedures and program implementation was made using object-oriented design and C/C++ language by A.P. Sokolov. All computational results have been performed using new-developed distributed high-perfomance software system GCD. Multiscale homogenization method was applied for single macroscopic level of composite construction and several connected microscopic levels. The task of stress-strain determination of composite construction was stated automatically by means of automatically defined plan based on certain computational problems. Architecture of software system and finite-element subsystem were developed too. Several practically important tasks were solved and some of its results are attached.

In this paper, we report the spatial distribution of OH radical density in atmospheric-pressure DC glow discharge using a miniature helium flow and an electrolyte cathode. Laser-induced fluorescence imaging was applied for the measurement of the OH radical density. The effect of collisional quenching was considered in obtaining the spatial distribution of the OH density. The spatial distribution of the OH radical density showed that the peak of the OH density was located at a separated distance from the electrolyte surface. However, the OH radicals kept contact with the electrolyte surface. It was suggested that the OH radicals were generated mainly in a region separated from the electrolyte surface and some fraction of the generated OH radicals reached to the liquid phase.

The open-circuit voltage of an organic solar cell is increasing with decreasing temperature and with increasing illumination intensity. These dependencies are quantitatively investigated for two types of organic solar cells, one with a flat donor-acceptor heterojunction and one with a mixed layer bulk heterojunction. Zinc-phthalocyanine and C60 are used as donor and acceptor, respectively. A qualitative difference is found for the two geometries. We find that a logarithmic illumination intensity dependence with temperature as a linear pre-factor of the logarithm, which is commonly reported and observed, is applicable for the bulk heterojunction. The flat heterojunction, in contrast, shows a constant illumination intensity pre-factor which is independent of the temperature, and the temperature can be modeled as additional linear summand.

Additive nanofabrication by two-photon polymerization (TPP) has recently drawn increased attention due to its sub-100 nm resolution and truly three-dimensional (3D) structuring capability. However, besides additive processes, subtractive process is also demanded for many 3D fabrications. Method possessing both additive and subtractive fabrication capabilities was rarely reported. In this study, we developed a complementary 3D micro/nano-fabrication process by integrating both additive two-photon polymerization (TPP) and subtractive multi-photon ablation (MPA) into a single platform of femtosecond-laser direct writing process. Functional device structures were successfully fabricated including: polymer fiber Bragg gratings containing periodic holes of 500-nm diameter and 3D micro-fluidic systems containing arrays of channels of 1-µm diameter. The integration of TPP and MPA processes enhances the nanofabrication efficiency and enables the fabrication of complex 3D micro/nano-structures that are impractical to produce by either TPP or MPA alone, which is promising for a wide range of applications including integrated optics, metamaterials, MEMS, and micro-fluidics.

This work describes the study of synthesis and physical characterization of nanostructured manganite oxides. The La0.8Sr0.2MnO3 (LSM) nanotubes and fibers have been prepared by electrospinning and pore wetting technique. The samples were characterized by Xray diffraction (XRD), scanning electron microscopy (SEM) and magnetization as a function of temperature (M(T)). XRD results of LSM fibers and nanotubes revealed that both samples crystallize in a rhombohedra-distorted perovskite structure. SEM pictures of these samples revealed ultrafine grains assembled in fibers and nanotubes samples. Analysis of these images revealed samples with external diameter ranging from 300 to 1.4 mm, and 7 μm to hundreds of mm in length. The M(T) measurements of samples La0.8Sr0.2MnO3 revealed a paramagnetic/ferromagnetic transition with decreasing temperature. Such transition occurs at temperatures of Tc ≈ 337 K and Tc ≈ 360 K for the nanotubes and fibers, respectively. Furthermore, this variation of the Tc values is also reported in literature for other manganite nanostructures. Such variation can be related to the microstructural characteristics observed for both LSM samples produced in this work. In general, it is believed that both methodologies allowed the production of nanostructures LSM. Also, these results suggest that the dimensionality of the samples seems to interfere in the physical properties of LSM manganite.

Tissue engineering aims to save lives by producing synthetic organs and bone. This study is attempting to determine what effects a polycaprolactone (PCL) scaffold will have on the blood flow of Rattus norvegicus, as measured by the number of platelets. Prior to experimentation, it was hypothesized that the polycaprolactone scaffold would maintain and/or increase the number of platelets when compared to the control group. This was developed based on prior research that showed polylactic acid (PLA), a polymer being used currently, and polycaprolactone had similar characteristics like boiling point, melting point, and glass transition temperature. To test this hypothesis, the PCL, created from an existing protocol, was used to mold a scaffold in vitro. Three groups of rats were identified, then further split into an “A” and “B” subdivision with 5 members in each. All “A” subdivision members received the scaffold, while the "B" factions lacked it. Each rat underwent surgery to remove 1mm of the right ventricle, which was replaced by the PCL scaffold in the experimental group. The control group did not have the scaffold replacement. Without this piece of the right ventricle, prior research conducted at the University of Virginia in 2006 suggests that the rats would die within one week. However, in the experimental group of rats, the missing piece of the ventricle was replaced with the scaffold, so if it were accepted then the rats would survive beyond 1week. All rats in the experimental group died exactly 1 week after the control group as predicted before experimentation. After all of the rats had a 1-week acclimation period, a 1mm^2 slice of the heart was extracted and then the number of platelets was counted using a phase contrast microscope. The heart extraction was prepared in a petri dish and then placed into a hemocytometer, splitting the dish into smaller sections making it possible to count. The data supports the hypothesis whereby an average 12% increase in the number of platelets in the rats with the PCL scaffold versus the group without it was seen. This increase in platelet count reflects an increase in blood flow. A statistical t-test was conducted on each trial (n=5 per group, n=10 total per trial) comparing experimental versus control group to calculate a p-value. The p-values were 0.034, 0.045, and 0.022, respectively which indicates statistical significance since the value is less than 0.05. After all experimentation, the benefits of using PCL in tissue engineering were examined. For example, PCL costs $80 less to produce per kilogram than polylactic acid. This study suggests that PCL would be a viable candidate for tissue engineering in humans.

We explore theoretically the effect of incorporating a thin tunnel barrier between the electron and hole transport layers of organic heterostructure photovoltaic devices. The device efficiency can be improved significantly by controlling the rates of microscopic processes associated with exciton dissociation and recombination at the interface between the electron and hole transport layers. The effects of different parameters are examined, and conclusions for organic photovoltaic device design are discussed.

The advent of graphene created a new era in materials science. Graphene is a two-dimensional planar honeycomb array of carbon atoms in sp2-hybridized states. A natural question is whether other elements of the IV-group of the periodic table (such as silicon and germanium), could also form graphene-like structures. Structurally, the silicon equivalent to graphene is called silicene. Silicene was theoretically predicted in 1994 and recently experimentally realized by different groups. Similarly to graphene, silicene exhibits electronic and mechanical properties that can be exploited to nanoelectronics applications.

In this work we have investigated, through fully atomistic molecular dynamics (MD) simulations, the mechanical properties of single-layer silicene under mechanical strain. These simulations were carried out using a reactive force field (ReaxFF), as implemented in the LAMMPS code. We have calculated the elastic properties and the fracture patterns.

Our results show that the dynamics of the whole fracturing processes of silicene present some similarities with that of graphene as well as some unique features.

High pressure low temperature electrical resistance measurements were carried out on a series of 122 iron-based superconductors using a designer diamond anvil cell. These studies were complemented by image plate x-ray diffraction measurements under high pressures and low temperatures at beamline 16-BM-D, HPCAT, Advanced Photon Source. A common feature of the 1-2-2 iron-based materials is the observation of anomalous compressibility effects under pressure and a Tetragonal (T) to Collapsed Tetragonal (CT) phase transition under high pressures. Specific studies on antiferromagnetic spin-density-wave Ba0.5Sr0.5Fe2As2 and Ba(Fe0.9Ru0.1)2As2 samples are presented to 10 K and 41 GPa. The collapsed tetragonal phase was observed at a pressure of 14 GPa in Ba0.5Sr0.5Fe2As2 at ambient temperature. The highest superconducting transition temperature in Ba0.5Sr0.5Fe2As2 was observed to be at 32 K at a pressure of 4.7 GPa. The superconductivity was observed to be suppressed on transformation to the CT phase in 122 materials.

We have fabricated high-efficiency a-Si/µc-Si tandem solar cells and modules with a very high µc-Si deposition rate using Localized Plasma Confinement CVD to give very high-rate deposition (>2.0 nm/s) of device-grade µc-Si layers. For further progress in productive plasma-CVD techniques, we have studied plasma phenomena by combining newly developed plasma simulation and plasma diagnosis techniques that reveal the importance of non-emissive atomic hydrogen. We also have proposed a model of defective µc-Si formation on highly textured substrates in which the atomic H in plasma is assumed to play an important role. We are also developing a non-vacuum deposition technique that we term “Liquid Si Printing.” A new record conversion efficiency for HIT solar cells of 24.7% has been achieved using a very thin c-Si wafer (Thickness: 98 µm, Area: 102 cm2).

Inkjet printing provides an interesting technology for electronic devices, as it is a versatile minimum-waste cost-effective technique for direct writing on almost every surface without need of masks or sacrificial layers. Among the fields in which it has been tested, transparent and flexible electronics offer a variety of applications ranging from large-area roll-toroll (such as OLEDs for lighting or solar cells) to small low-consumption biocompatible devices such as biosensors.

This work aims to present some advances in the field of semiconductors synthesized by sol-gel and patterned by inkjet printing. Chemical routes are used to obtain suitable inks, based on salts of Ga, In, Zn, Cu and Sn and solvents as methoxyethanol. Inkjet printing provides thin layers 20-300nm thick, with morphology strongly depending on the materials. Different thermal treatments are tested, and some chemical and optical characterization of the obtained layers allows optimizing the technology for each material.

The effectiveness of the inks and the technique is demonstrated by the electronic behavior of thin-film transistors fabricated by the proposed technology. The different devices are compared, suggesting the properties of the different materials analyzed, as a step ahead in the development of a complete logic for such promising applications of the flexible electronics.

We present comprehensive quantitative analysis of Raman spectra in two-(Si/SiGe superlattices) and three-(Si/SiGe cluster multilayers) dimensional nanostructures. We find that the Raman spectra baseline is due to the sample surface imperfection and instrumental response associated with the stray light. The Raman signal intensity is analyzed, and Ge composition is calculated and compared with the experimental data. The local sample temperature and thermal conductivity are calculated, and the spectrum of longitudinal acoustic phonons is explained.

We performed a thorough investigation of mid-infrared heavy-to-light hole intersubband absorption in the valence band of p-doped GaAs quantum wells with AlAs barriers. For the p-type doping a high-purity solid carbon source was used. The experimental results are compared with theoretical simulations. The inclusion of layer inter-diffusion well reproduces the transition energies. We estimate a 6-10 Å inter-diffusion length that is consistent with electron microscopy measurements. A careful analysis of our results provides valuable information for further design of emitters and detectors based on hole intersubband transitions in the valence band.

In this study, we employed Multiple Internal Reflection Infrared Spectroscopy (MIR-IR) to characterize chemical bonding structures of boron doped hydrogenated amorphous silicon (a-Si:H(B)). This technique has been shown to provide over a hundred fold increase of detection sensitivity when compared with conventional FTIR. Our MIR-IR analyses reveal an interesting counter-balance relationship between boron-doping and hydrogen-dilution growth parameters in PECVD-grown a-Si:H. Specifically, an increase in the hydrogen dilution ratio (H2/SiH4) was found to cause the increase in the Si-H bonding and a decrease in the B-H and SiH2 bonding, as evidenced by the changes in corresponding IR absorption peaks. In addition, although a higher boron dopant gas concentration was seen to increase the BH and SiH2 bonding, it also resulted in the decrease of the most stable SiH bonding configuration. The new chemical bonding information of a-Si:H thin film was correlated with the various boron doping mechanisms proposed by theoretical calculations.

We report on light-sensitive nanocrystal skin (LS-NS) platforms composed of monolayer visible nanocrystals (NCs) on top of bilayers of polyelectrolyte polymers. These LS-NS devices are operated on the principle of photogenerated potential buildup, unlike common photodetectors that operate on the basis of charge collection. The resulting devices are as highly sensitive as common photosensors, despite utilizing a monolayer of NCs and requiring no applied external bias. In this device architecture, using only a single NC monolayer also allows to reduce noise current generation. This LS-NS platform is highly stable under ambient conditions with fully sealed NC monolayer, promising for low-cost large-area UV/visible sensing applications. However, such visible NC based LS-NS devices exhibit limited performance in the long wavelength range due to the low optical absorption of these NCs (e.g., CdTe NCs) in this spectral range. Here, to enhance the device sensitivity, incorporating silver nanoparticles into LS-NS is proposed and demonstrated. For that, the optical absorption of CdTe monolayer NCs in the LS-NS devices is increased using the embedded silver nanostructures. With plasmon coupling, we observe a 2.6-fold enhancement factor in the photosensitivity around the localized surface plasmonic resonance peak of the nanostructures. Higher sensitivity improvement is also obtained at longer wavelengths. To predict the enhancement in the sensitivity of the LS-NS, numerical simulations are performed and the simulation results are found to agree well with the experimental data. Plasmonically enhanced LS-NS hold great promise for large-area photosensing applications extending from UV to IR including windows and facades of smart buildings.

We prepared colloidal crystals by self-assembly of gold-coated silica nanospheres, and formed free-standing nanoporous membranes by sintering these colloidal crystals. We modified the nanopore surface with ionizable functional groups, by forming a monolayer of L-cysteine or by surface-initiated polymerization of methacrylic acid. Diffusion experiments for neutral and cationic dyes showed that transport through these surface-modified Au-coated colloidal membranes can be controlled by pH and presence of metal cations.