We have investigated the effect of 3d-transition metal Fe (Iron) doping at Mn site of nanometric polycrystalline La0.7Sr0.3MnO3 (i.e. La0.7Sr0.3Mn1-xFexO3; 0 ≤ x ≤ 0.1) CMR manganites on magneto-transport and magnetic properties. Nanocrystalline Fe doped La0.7Sr0.3MnO3 powders were synthesized through chemical route “Pyrophoric Reaction Process” and calcinated at 850°C for 5 hrs. X-ray diffraction (XRD) patterns of synthesized powder indicate that all samples are having perovskite structure without any secondary impurity phase. Average crystallite size was found to be 20 nm using Debye Scherer formula. Transmission electron micrographs (TEM) show that the average particle sizes are in nanometric regime (φ ˜ 50 nm) and samples are polycrystalline in nature which was observed through selected area electron diffraction (SEAD) patterns. The effect of Fe doping at Mn site of La0.7Sr0.3MnO3 was found to change substantially the magnetic and transport properties without modifying lattice structure. The suppression of magnetic and transport properties were observed due to dilution of double exchange mechanism in Mn3+- O2--Mn4+ network in La0.7Sr0.3MnO3.

Polymerized organic thin films were synthesized on a variety of substrates by Plasma Enhanced Chemical Vapor Deposition (PECVD) technique using isopropanol as precursor. Hydrogen peroxide, ammonium hydroxide, and iodine dissolved in isopropanol were used as dopants and chlorobenzene as copolymerization precursor. The structural, optical and electrical properties of the films were studied as functions of the dopant type and concentration.

The polymeric films were characterized by variable angle ellipsometry (VAE), atomic force microscopy (AFM), Fourier Transform Infrared spectroscopy (FTIR), ultraviolet-visible transmission spectroscopy and photoluminescence. The electrical film behavior was explored by the four points probe method.

The growth rate, refractive index, optical bandgap, chemical structure and resistivity of the films strongly depend on the concentration and type of dopant added. The AFM microphotographs showed smooth surfaces with RMS roughness less than 10 nm. The optical bandgap values of the films were in the range of 2.6 to 3.26 eV, the resistivity was in the order of 103 – 104 ohm-cm. The photoluminescence response of the polymerized films was obtained in the visible region, by exciting with a UV laser.

We investigate the electron spin resonance (ESR) spectroscopy for the field-induced carriers in rubrene single-crystal field-effect transistors (SC-FETs), and compare the results with those on pentacene thin-film transistors (TFTs). We observe Lorentz-type ESR signal in rubrene SC-FETs whose linewidth is narrowed with increasing gate voltage and temperature. It demonstrates that the ESR linewidth is determined by motional narrowing effect as we reported on pentacene TFTs. Based on the observations, we discuss the multiple trap-and-release (MTR) processes in the two systems with and without grain boundaries.

This work is a step towards a viable process for poly-SiGe MEMS structural layers deposited at substrate temperatures below 250°C. Laser annealing was used for post-deposition layer treatment to realize poly-SiGe structural layers with the desired electrical and mechanical properties at low substrate temperatures. The technique uses a pulsed excimer laser beam for the local thermal treatment of a SiGe layer deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD) at 210°C. By tuning the laser treatment and the film deposition conditions, 1-1.8 μm thick films having an electrical resistivity as low as 14.1 mΩ∙cm and optimal strain gradient in the range of -4.3×10-6 to +6.8×10-6 μm-1 were realized.

By using tin chloride solution as the raw material, a nano-sized tin oxide powder with average particle size below 50 nm is generated by spray pyrolysis reaction. This study also examines the influences of the reaction parameters such as reaction temperature and the concentration of raw material solution on the powder properties. As the reaction temperature increases from 800 to 850 ℃, the average particle size of the generated powder increases from 20 nm to 30 nm. As the reaction temperature reaches 900 ℃, the droplets are composed of nano-particles with average size of 30 nm, while the average size of individual particles increases remarkably up to 80˜100 nm. When the tin concentration reaches 75 g/L, the average particle size of the powder is below 20 nm. When the tin concentration reaches 150 g/L, the droplets are composed of nano particles with average size around 30 nm, whereas the average size of independent particles increases up to 80˜100 nm. When the concentration reaches 400 g/L, the droplets are composed of nano-particles with average size of 30 nm.

Organic light-emitting devices (OLEDs) emitting near-infrared (NIR) light have many potential applications, yet the efficiency of these devices remains very low, typically ˜0.1% or less. Here we report efficiency NIR OLEDs based on two fluorescent donor-acceptor-donor oligomers and a phosphorescent Pt-containing organometallic complex. External quantum efficiencies in the range of 0.5–3.8% with emission peak ranging from 700 to 890 nm have been achieved.

In-situ observation on the catalytic effect of Nb2O5 in MgH2 was carried out by using transmission electron microscopy (TEM). We prepared two kinds of samples, because we tried to observe the reaction from two kinds of viewpoints. MgH2 catalyzed with 1 mol% of Nb2O5 was prepared for an overall viewpoint on the desorption process of MgH2 with catalyst by conventional TEM. The dehydrogenation of the 1 mol% sample started at 150 °C and Mg nano-size particles were formed. However, Nb2O5 was not confirmed in diffraction patterns and images, because it was highly dispersed by ball-milled. So MgH2 catalyzed with 10 mol% of Nb2O5 was prepared for local viewpoint to focus the boundary between the catalyst and the Mg phase by high voltage electron micro scope (HVEM). The sample mixed in mortar was prepared for this, because it was difficult to find the boundary in the sample ball-milled. The high resolution images of the 10 mol% sample revealed that the dehydrogenation started from the interface of MgH2 and Nb2O5. The result suggested that the dehydrogenation could proceed with hydrogen diffusion from MgH2 phase to the interface between Mg and Nb2O5.

Coarse-grained network models of proteins successfully predict equilibrium properties related to collective modes of motion. In this study, the network construction strategies and their systematic application to proteins are used to explain the role of network models in defining the collective properties of the system. The analysis is based on the radial distribution function, a newly defined angular distribution function and the spectral dimensions of a large set of globular proteins. Our analysis shows that after reaching a certain threshold for cut-off distance, network construction has negligible effect on the collective motions and the fluctuation patterns of the residues.

In our study, thermosensitive core-shell microgel particles have been used as the carrier system for the deposition of metal nanoparticles, in which the core consists of polystyrene (PS) whereas the shell consists of poly(N-isopropylacrylamide) (PNIPA) network crosslinked by N, N'-methylenebisacrylamide (BIS). Silver, gold and palladium nanoparticles have been homogeneously embedded into thermosensitive PNIPA-networks, respectively. We demonstrate that the catalytic activity of the microgel-metal nanocomposites can be tuned by the volume transition within the microgel of these systems by using the catalytic reduction of 4-nitrophenol as the model reaction. Moreover, following the concept of a “green chemistry”, the oxidation of alcohols to the corresponding aldehydes or ketones can be carried out in aqueous solution under aerobic conditions at room temperature by using microgel-metal nanocomposites as the catalyst. The influence of temperature on the catalytic activity has been also investigated, which will be affected both by the volume transition of the microgel and by the change of polarity of the microgel in this case.

Thin film growth by high vacuum evaporation of the n-type organic semiconductor 5, 5″′-diperfluorohexylcarbonyl-2,2′:5′,2″:5″,2″′-quaterthiophene (DFHCO-4T) on poly-(α-methylstyrene)-coated n++-Si/SiO2 substrates is investigated at various deposition fluxes and substrate temperatures. Film characterization by atomic force microscopy reveals typical Stransky-Krastanov growth. Transistors with Au source-drain top contacts and optimized DFHCO-4T deposition conditions attain an apparent saturation mobility of 4.6 cm2/Vs, whereas this parameter is 100× lower for similar transistors with LiF/Al top contacts. We explain this lower performance by the formation of a thin interfacial layer with poor injection properties resulting from a redox reaction between Al and DFHCO-4T.

Biomimetics deals with the application of nature-made ‘design solutions’ to the realm of engineering. In the quest to understand mechanical implications of structural hierarchies found in biological materials, multiscale mechanics may hold the key to understand ‘building plans’ inherent to entire material classes, here bone and bone replacement materials. Analyzing a multitude of biophysical hierarchical and biomechanical experiments through homogenization theories for upscaling stiffness and strength properties, reveals the following design principles: The elementary component ‘collagen’ induces, right at the nanolevel, the mechanical anisotropy of bone materials, which is amplified by fibrillar collagen-based structures at the 100 nm-scale, and by pores in the micrometer-to-millimeter regime. Hydroxyapatite minerals are poorly organized, and provide stiffness and strength in a quasi-brittle manner. Water layers between hydroxyapatite crystals govern the inelastic behavior of the nano-composite, unless the ‘collagen reinforcement’ breaks. Bone replacement materials should mimic these ‘microstructural mechanics’-features as closely as possible.

Sparse arrays of evaporated silver nanodiscs were fabricated with nanosphere lithography (NSL) on glass substrates and on hydrogenated nanocrystalline silicon solar cells. The optical transmittance spectra for arrays on glass vary substantially with film thickness, and were reasonably consistent with previous work. The quantum efficiency spectra of hydrogenated nanocrystalline silicon solar cells show spectral shifts due to coupling of surface plasmons in the metal nanodiscs to the planar waveguide modes of the cells, with overall photocurrent enhancement up to 10%.

We have shown that (Pb1-mSnmTe)1-x(PbS)x where m = 0.05 and x = 0.08 exhibits a ZT of ˜1.4 at 700 K. This system incorporates two thermoelectric systems: PbSxTe1-x and Pb1-xSnxTe. Here we report the thermoelectric properties of PbSxTe1-x (x = 0.08 and 0.30). The material PbS0.08Te0.92 exhibits nucleation and growth of PbS precipitates, while PbS0.30Te0.70 exhibits PbS precipitation through spinodal decomposition phase separation. We report the thermoelectric properties of this system as a result of the differing precipitation phenomena.

The need of intelligent implant materials for applications in the area of minimally invasive surgery leads to tremendous attention for polymers which combine degradability and shape-memory capability. Application of heat, and thereby exceeding a certain switching temperature T sw, causes the device to changes its shape. The precise control of T sw is particularly challenging. It was investigated in how far T g, that can be used as T sw, of amorphous polymer networks from star-shaped polyester macrotetrols crosslinked with a low-weight linker can be controlled systematically by incorporation of different comonomers into poly(rac-lactide) prepolymers. The molecular mass of the prepolymers as well as type and content of the comonomers was varied. The T g could be adjusted by selection of comonomer type and ratio without affecting the advantageous elastic properties of the polymer networks.

Transmission electron microscopy (TEM), differential scanning calorimetry (DSC), and x-ray diffraction (XRD) investigations were conducted on the hot-pressed Ti2SnC bulk ceramic. Microstructure features of bulk Ti2SnC ceramic were characterized by using TEM, and a needle-shaped β-Sn precipitation was observed inside Ti2SnC grains with the orientation relationship: (0001) Ti2SnC // (200) Sn and Ti2SnC // [001] Sn. With the combination of DSC and XRD analyses, the precipitation of metallic Sn was demonstrated to be a thermal stress-induced process during the cooling procedure. The reheating temperature, even as low as 400 °C, could trigger the precipitation of Sn from Ti2SnC, which indicated the low-temperature instability of Ti2SnC. A substoichiometry Ti2SnxC formed after depletion of Sn from ternary Ti2SnC phase. Under electron beam irradiation, metallic Sn was observed diffusing back into Ti2SnxC. Furthermore, a new Ti7SnC6 phase with the lattice constants of a = 0.32 and c = 4.1 nm was identified and added in the Ti-Sn-C ternary system.

Source material purification according to a thermodynamic analysis is reported for the sublimation crystal growth of aluminum nitride in an inert reactor. OAlOH is strongly favored over all other possible oxygen containing compounds in both the Al-O-H-N and Al-O-H-C-N systems, while Al2O, proved to be the most favorable oxygen containing gas species for Al-O-N system in previous study, become secondary favorable gas species. A low temperature (<1200 °C) treatment is effective in eliminating oxygen and hydrogen from the source powder. Carbon monoxide is another important oxygen containing gas species in the Al-O-H-C-N system, and is favored over Al2O at certain temperature and pressure. Carbothermal reduction with intentionally added carbon (graphite) can further reduce the oxygen concentration. Experiments show that high-temperature sintering minimizes the oxygen concentration and reduces the specific surface area of the source. With only 5.5% of mass loss, the purification produced a source with low O, H, and C concentrations of 0.018 wt%, 6ppm, and 0.006wt%.

Strategies for the structurally identification of nanocrystals from Precession Electron Diffraction (PED) patterns in a Transmission Electron Microscope (TEM) are outlined. A single-crystal PED pattern may be utilized for the structural identification of an individual nanocrystal. Ensembles of nanocrystals may be fingerprinted structurally from “powder PED patterns”. Highly reliable “crystal orientation & structure” maps may be obtained from automatically recorded and processed scanning-PED patterns at spatial resolutions that are superior to those of the competing electron backscattering diffraction technique of scanning electron microscopy. The analysis procedure of that automated technique has recently been extended to Fourier transforms of high resolution TEM images, resulting in similarly effective mappings. Open-access crystallographic databases are mentioned as they may be utilized in support of our structural fingerprinting strategies.

Industrial applications of PE MWCVD diamond grown on large area substrates, 3D shapes, at low substrate temperatures and on standard engineering substrate materials require novel plasma concepts. Based on the pioneering work of the group at AIST in Japan, high-density coaxial delivery type of plasmas have been explored [1]. However, an important challenge is to obtain commercially interesting growth rates at very low substrate temperatures. In the presented work we introduce the concept of novel linear antenna sources, designed at Leybold Optics Dresden, using high-frequency pulsed MW discharge. We present data on high plasma densities in this type of discharge (> 10 E11 cm-3), accompanied by data from OES for CH4 – CO2 - H2 gas chemistry and the basic properties of the nano-crystalline diamond (NCD) films grown.

The strength of submicron FCC structure metal columns, σ, fabricated by FIB machining or electrodeposition, shows a strong correlation with specimen diameter, d, with σ/μ = A(d/b) −0.63, where A is a constant, μ is the single crystal shear modulus resolved onto the slip system and b is the Burgers' vector. The strength of BCC structure metals does not show such a well defined correlation with size across different metals but the data occupies the same region of parameter space as with the FCC metals. Nanoporous gold specimens show a similar size-correlated behaviour but with an exponent of −0.5. This may indicate different mechanisms operating in each case.

Large-scale growth capability is a general requirement for any reliable and cost-effective device application. Catalyst-free vapor-phase growth techniques generally let obtain high purity materials, but their application in large-scale growths of zinc oxide (ZnO) nanostructures is not trivial, because the lack of catalysts makes the control of these process rather difficult. Three different optimizations of the basic vapor phase growth have been studied and performed to obtain selected and reproducible growths of three different ZnO nanostructures with improved yield, i.e. nanotetrapods, nanowires and nanorods. No precursor or catalyst has been used in order to reduce contamination sources as more as possible.