Orientation patterned (OP)-GaAs crystals have high potential as non linear optical systems. Mid-infrared and terahertz lasers sources can be fabricated with these crystals by frequency conversion from shorter wavelength sources. The optical propagation losses are critical; therefore, the OP-GaAs crystals must have high quality with low incorporation of defects and high homogeneity to reduce the refractive index fluctuations. Defects with electro-optic signature must be characterized in order to reduce their presence. Cathodoluminescence studies of these crystals permit the distribution of the main defects to be established, both extended and point defects. Special attention is paid to the role of the walls between the two domain orientations, and to the incorporation of impurities in Si-doped samples.

Samples of carbon nanoparticles obtained by different technologies (carbon plasma deposition, irradiation, anodic etching etc.). by Raman scattering and photoluminescence were studied. It was shown that there are carbon nanoparticles which consist of a core containing sp2 bonds and a shell containing sp3 bonds. These particles have a rather intense photoluminescence. We propose the following photoluminescence mechanism of such nanoparticles: first the nanoparticle core absorbs light; further excitation is transmitted to the external cover or environment where photorecombination occurs. This effect occurs when the size of the particles becomes smaller than the size of the wave function excited state of the nanoparticle. The aim of this research is to check this mechanism.

In this work we investigate polymer photodiodes based on a blend system consisting of poly(3-hexylthiophene-2,5-diyl) (P3HT) and the fullerene derivative (6,6)-phenyl C-butyric acid methyl ester (PCBM). An optimized low source impedance architecture allows measurements in the GHz range with minimum distortion, while at the same time allowing to probe the favourable sandwich device structure. We have studied the underlying device physics and investigated the influence of parameters such as active layer thickness and bias voltage on the transient photocurrent response. Using a numerical simulation software combining a self-consistent drift-diffusion model in conjunction with an optical model based on the transfer matrix method we model the transient photocurrent of polymer photodiodes. Transient photocurrent measurements utilizing this low impedance device architecture excited by 1.6 ns short laser pulses show very good correlation between simulated and measured results. Furthermore we have developed an encapsulation technique to integrate high-speed organic photodiodes onto standard printed circuit boards (PCBs) to avoid the degradation of the devices by humidity or oxygen.

The surrounding ambient introduces a gaseous boundary to many potential nanotechnology applications such as nanoscale thermoelectric devices and low dimensional thermal control devices. Despite the large surface area to volume ratio of nanostructures, a formal study of the surface scattering effects induced by a gaseous boundary has received little attention. In this work, we consider the perturbing effects to the electron cloud or jellium of conducting nanostructures when submitted to a gaseous interface of varying interaction energies. Specifically, we incorporate the novel experimental method of Dynamic Electron Scattering (DES) to measure the Seebeck coefficient of 30 nm thick Au and Cu metal films in He and Ar atmospheres. The gas particle impact energy is varied by changing the flow speed from stationary (non-moving gas field) to high speed flow over the metal films. The scattering effects of each gas are clearly observable through a Seebeck coefficient increase as the gas impact energy increases. We find the high collision density of He to induce a greater increase in thermopower than the much heavier Ar with lower collision density. The perturbed transport properties of the Au and Cu thin films are explained by kinetic surface scattering mechanisms that dominate the scattering landscape of high surface area to volume ratio materials as suggested by comparative measurements on bulk Cu.

We have already reported that low-temperature (about 170 °C) preparation technique of silicon dioxide (SiO2) dielectric thin film that has high resistivity and extremely smooth surface by the photo oxidation process. In this paper, we have developed a low-damage preparation technique to fabricate a SiO2 thin film by the photo-assisted low temperature oxidation process in order to apply this process to the flexible electronics using for convenient plastic films. We have reported that the SiO2 dielectric thin film with a high insulation performance can be prepared by the low temperature processing below 100°C by improving the pre-processing of the photo oxidation of thin film.

This paper describes the principle of array sensing with film bulk acoustic resonators (FBARs) for combinatory mass sensing and the use of the arrayed FBAR resonant mass sensor for parallel detection of protein-ligand reactions in liquid environment. Various ligands were immobilized on the gold layer on the FBAR’s sensing surface for selective protein detection. The FBARs of the arrayed FBAR were fabricated to have different resonant frequencies from one another by adding slightly varied amount of mass loading on the resonators. Results showed that the arrayed FBAR could detect specific bindings on its surfaces as the concentration of the target ligand was varied.

We report on our investigation into the use of III-V superlattice structures for thermoelectric (TE) applications. Preliminary review of III-V materials trends indicate that the GaSb/InAs superlattice system should offer one of the best potentials for high thermoelectric performance in the 500K-800K range. MOCVD growth of GaSb/InAs superlattice structures was carried out, and relevant structural, thermal, and electrical characterization has been performed. TEM and XRD results demonstrate a well-ordered superlattice structure. Thermal conductivity measurements reveal a reduction in the room-temperature thermal conductivity of GaSb/InAs superlattices (4.4-10.0 W/m-K), relative to either binary GaSb (32 W/m-K) or InAs (27 W/m-K). Additionally, we have worked to optimize the thermoelectric power factor (α2σ), studying both Se- and Te-doping of the superlattice structures, in an effort to demonstrate optimal thermoelectric performance. Our results demonstrate a maximum ZT of 0.36 at 400K for optimally doped n-type GaSb/InAs superlattice structures.

Rechargeable batteries are in high demand for future hybrid vehicles and electronic devices markets. Among various kinds of rechargeable batteries, Li-ion batteries are most popular for their obvious advantages of high energy and power density, ability to offer higher operating voltage, absence of memory effect, operation over a wider temperature range and showing a low self-discharge rate. Researchers have shown great deal of interest in developing new, improved electrode materials for Li-ion batteries leading to higher specific capacity, longer cycle life and extra safety. In the present study, we have shown that an anode prepared from interface-controlled multiwall carbon nanotubes (MWCNT), directly grown on copper current collectors, may be the best suitable anode for a Li-ion battery. The newly developed anode structure has shown very high specific capacity (almost 2.5 times as that of graphite), excellent rate capability, nil capacity degradation in long-cycle operation and introduced a higher level of safety by avoiding organic binders. Enhanced properties of the anode were well supported by the structural characterization and can be related to very high Li-ion intercalation on the walls of CNTs, as observed in HRTEM. This newly developed CNT-based anode structure is expected to offer appreciable advancement in performance of future Li-ion batteries.

The conventional dye sensitized solar cell (DSSC) is limited by the use of a liquid electrolyte that is prone to leakage and evaporation. Efforts to replace the liquid with a solid equivalent have been met with difficulties in penetrating the mesoporous TiO2 nanostructured photoanode with liquid processing, particularly for photoanode layer thickness greater than 2 μm. Here, initiated chemical vapor deposition (iCVD) is successfully applied to directly synthesize and fill the pores of the mesoporous TiO2 network of up to 12 μm thickness with poly(2-hydroxyethyl methacrylate) (PHEMA) polymer electrolyte. Comparing with equivalent liquid electrolyte cells, DSSCs integrated with PHEMA polymer electrolyte showed consistently higher open circuit voltage, which is attributed to a decrease in electron recombination with the redox couple at the electrode-electrolyte interface.

In this contribution, we report on the optimization of a metal-organic decomposition (MOD) ink based on silver(I) complexes by a systematic variation of the ink formulation. As a result, three different ink concepts turned out to be printable and resulting in a sufficiently high contour definition, layer homogeneity, and conductivity. The ink concepts include increase of the solid load, the usage of N-methyl-2-pyrrolidone (NMP) as a humectant with low vapor pressure, addition of co-solvents such as diethylene glycole and addition of sodium lauryl sulfate (SLS) as stabilizing ligand. It turns out that, for silver precursor concentrations of 40 wt%, the addition of 1 wt% SLS to aqueous inks leads to elevated conductivity up to 3.2x107 Sm-1 at maintained printability and an improved contour definition with respect to pure aqueous inks.

We report that the high crystalline and high efficiency green emission semipolar {101̅1} InGaN/GaN multiple quantum wells (MQWs) grown on the {101̅1} facets of GaN nanopyramid arrays by selective area epitaxy. Clear and sharp interfaces of the semipolar {101̅1} InGaN/GaN MQWs was observed by transmission electron microscopy images. As comparing with (0001) MQWs, the internal electric field of {101̅1} MQWs was remarkably reduced from 1.7 MV/cm to 0.5 MV/cm, and the room temperature (RT) internal quantum efficiency (IQE) at green emission was enhanced by about 80%. This greatly enhancement of IQE is due to suppress the polarization effect in the {101̅1} MQWs which shorten the radiative recombination to compete with nonradiative recombination at RT. These results evince that the {101̅1} planes are promising for solving the efficiency green gap of III-nitride light emitters.

Iron deficiency affects approximately 2 billion people worldwide, especially young women and children. Food fortification with iron is a sustainable approach to alleviate iron deficiency but remains a challenge. Water-soluble compounds with high bioavailability (e.g. the “gold standard” FeSO4) usually cause unacceptable sensory changes in foods, while compounds that are less reactive in food matrices are often less bioavailable. Solubility (and therefore bioavailability) can be improved by increasing the specific surface area (SSA) of the compound, i.e. decreasing its particle size to the nm range. Here, iron oxide-based nanostructured compounds with Mg or Ca are made using scalable flame aerosol technology. Addition of either element increased iron solubility to a level comparable to iron phosphate. Furthermore, these additions lightened the powder color and sensory changes in fruit yoghurt were less prominent than for FeSO4.

The dependency of Young’s and shear modulus on relative density and temperature was determined for three series of skutterudites: p-type MmyFe3CoSb12 (y = 0.70, 0.80), p-type DDyFe3CoSb12 (y = 0.65, 0.68) and n-type Sr0.07Ba0.07Yb0.07Co4Sb12. For all three groups of materials the dependency of Young’s modulus, E, on the density and temperature is linear: E(d) = 4.1(1)×d – 268(3) GPa (d is the relative density in %), ΔE/ΔT = 0.20(1) GPa/K, thus allowing extrapolation of E as a function of temperature and towards 100% density.

The diameter of individual single-walled carbon nanotubes (SWNTs) was successfully modulated along their axes by instant temperature control in a laser-assisted chemical vapor deposition (LCVD) process. SWNTs were grown using different temperature profiles to investigate the effects of temperature variation on their growth. Due to the inverse relationship between SWNT diameter and growth temperature, SWNTs with ascending diameters were obtained by reducing the LCVD temperature from high to low. The diameter-modulated SWNTs were grown across a pair of Mo electrodes to form field-effect transistors (FETs) for investigation of their electronic transport properties. Fabricated devices demonstrated properties similar to Schottky diodes, implying different bandgap structures at the ends of the SWNTs. Raman spectroscopy, transmission electron microscopy, and electronic transport characteristics were studied to investigate the influence of temperature variation on the structural and electronic characteristics of SWNTs.

The interfacial energies between template-directed calcite nuclei and self-assembled monolayers of 16-mercaptohexadecanoic acid (MHA) and 11-mercaptoundecanoic acid (MUA) were measured. The results reveal that (1) the MHA and MUA significantly reduce the effective surface energy of calcite from about 97 mJ/m2 in solution to about 45.3 and 52.7 mJ/m2 on MHA and MUA respectively, providing a thermodynamic basis for the strong capacity of MHA and MUA to promote calcite nuclei; and (2) the barrier to nucleation is dominated by the free energy barrier which enhances the rate of surface nucleation on MHA and MUA.

Crystal structure, pressure response, and polymorph transformation wereinvestigated for crystalline indole through dispersion-corrected densityfunctional theory (DFT-D) method. An accurate, nonempirical method (as inthe latest implementations of CASTEP) is used to correct for the general DFTscheme to include van der Waals interactions important in molecularcrystals. Ambient structural details, including space group symmetry,density, and fine structural details, such as bicyclic angles, have beenreproduced to within experimental accuracy. Pressure response of thestructure was obtained to isostatic pressure up to 25 GPa, in increments of1 GPa. Evolution of space group symmetry and the bicyclic angle were mappedas a function of pressure. A previously unknown phase transformation hasbeen identified around 14 GPa of isostatic pressure. Total energies of thephases before and after phase transformation are nearly identical, with aphase transformation barrier of 0.9 eV. The study opens up the door toreliable DFT investigations of chemical reactions of crystalline aromaticsystems under high pressure (e.g. formation of amorphous sp3hybridized phases).

We have synthesized single crystalline Ba8AlxSix-46 clathrates by using the flux Czochralski (CZ) method with Al-rich melt. The specific electric resistivity, the Seebeck coefficient and the power factor of single crystalline Ba8Al14Si32 were 0.73 mΩcm,70.0μV/K and 6.8×10-4 V2/K2Ωm, respectively. These values are higher than that of single crystalline Ba8Al12Si34 clathrate because of the reduced carrier concentration. It is indicated that Al contents and the carrier concentration of single crystalline Ba8AlxSi46-x can be controlled by using the flux Czochralski method.

We report on Cr2O3 layer by thermal evaporation of Cr2O3 powder as cathode interfacial layer to improve the stability in air for the bulk heterojunction solar cells of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM). Devices with Cr2O3 interfacial layers show higher power conversion efficiency (PCE) and stability than those without interfacial layer. Devices with Cr2O3 show improved stability approximately 100 times than that of devices without interfacial layer or with LiF interfacial layer.

Nanostructuring has opened new ways to increase the thermoelectric performance of a host of materials, mainly by decreasing their thermal conductivity κ while preserving the Seebeck coefficient S and electrical conductivity σ. The thermoelectric properties of degenerated polycrystalline silicon films with nanocavities (NCs) have been studied as a function of annealing temperature upon isochronous annealings in argon carried out every 50°C in the range 500 – 1000°C which were used to modify the shape of the NCs. We found that presence of the NCs had no negative effect on the electronic properties of the system. The measured values of S and σ were close to those previously reported for the blank polycrystalline silicon films with the same doping level. The thermal conductivity was also found to be close to the value measured on the blank sample, about half of the reported value in polycrystals. This led to a power factor of 15.2 mWm-1K-2 and a figure of merit of 0.18 at 300 K.