Nanoporous carbon is a widely studied material due to its potential applications in hydrogen storage or for filtering undesirable products. Most of the developments have been experimental although some simulation work has been carried out based on the use of graphene sheets and/or carbon chains and classical molecular dynamics. The slit pore model is one of the oldest models proposed to describe porous carbon. Developed by Emmet in 1948 [1] it has been recurrently used and in its most basic form consists of two parallel graphene layers separated by a distance that is taken as the width of the pore. Its simplicity limits its applicability since experimental evidence suggests that the walls of the carbon pores have widths of a few graphene layers [2], but it still is appealing for computational simulations due to its low computational cost. Using a previously developed ab initio approach to generate porous semiconductors [3] we have obtained porous carbonaceous materials with walls made up of a few graphene layers (four layers), in agreement with experimental results; these walls are separated by distances comparable to those used in the slit pore model [4]. This validates the idea of a modified slit pore model obtained without the use of ad hoc suppositions. Structures will be presented, analyzed and compared to available experimental results.

The micro-photoluminescence (μ-PL) spectra of a single CdTe/CdSe quasi- type II core-shell colloidal quantum dots (CQDs) unambiguously reveal an emission of a biexciton (2X), a triexciton (3X) and a quadraexciton (4X) under continuous-wave excitation. The CQDs were characterized by optical measurements and theoretical consideration of carrier's wavefunctions distribution of a quasi-type II core-shell structure.

Ion-implantation has been used to introduce oxygen concentration-depth profiles into nominally oxygen-free amorphous silicon (a-Si). The effect of O concentrations in excess of 1018 cm−3 on the formation of high pressure crystalline phases (Si-III and Si-XII) during indentation unloading has been studied. By examination of unloading curves and post-indent Raman micro-spectroscopy O is found to inhibit the so-called pop-out event during unloading and, therefore, the formation of the crystalline phases. Furthermore, at high O concentrations (> 1021 cm−3) the formation of these phases is reduced significantly such that under indentation conditions used here the probability of forming the phases is reduced to almost zero. We suggest that the bonding of O with Si reduces the formation of Si-III/XII during unloading through a similar mechanism to that of oxygen-retarded solid phase crystallization of a-Si.

An experimental study on mid-infrared intersubband absorption in InGaAs/GaAsSb multiple quantum wells grown lattice-matched to InP substrates by molecular beam epitaxy is presented. Intersubband absorption in a broad wavelength region (5.8 - 11.6 μm) is observed in multiple quantum well samples with well widths ranging between 4.5 and 12 nm. A conduction band offset at the InGaAs/GaAsSb heterointerface of 360 meV gives an excellent agreement between the theoretically calculated ISB transition energies and the Fourier-transform infrared spectroscopy measurements over the whole range of well widths under investigation. Two kinds of intersubband devices based on the InGaAs/GaAsSb material system are presented: a quantum well infrared photodetector operating at a wavelength of 5.6μm and an aluminum-free quantum cascade laser. The presented quantum cascade laser emits at a wavelength of 11.3 μm, with a threshold current density of 1.7 kA/cm2 at 78 K.

In this paper we investigate the carriers mobility enhancement of the n- and p-channel single-grain silicon thin-film transistors (SG-TFTs) by μ-Czochralski process at low-temperature process (< 350 °C). The high laser energy density nearby the ablation phenomenon that completely melts the silicon layer during the crystallization is responsible for high tensile strain and good crystal quality of the silicon grains, which lead carriers mobility enhancement.

This paper focuses on the measurement of material properties of micro and nano-electromechanical systems. Two different methods are discussed: electrical or optical measurements of the resonance frequency, and measurements of the Raman frequency shift. The main focus of this paper is on challenges and pitfalls related to the use of these techniques for the study of MEMS and NEMS.

Strains in GaN nanowires with InGaN quantum wells (QW) were measured from transmission electron microscope (TEM) images. The nanowires, all from a single growth run, are single crystals of the wurtzite structure that grow along the <0001> direction, and are approximately 1000 nm long and 60 nm to 130 nm wide with hexagonal cross-sections. The In concentration in the QWs ranges from 12 to 15 at %, as determined by energy dispersive spectroscopy in both the transmission and scanning electron microscopes. Fourier transform (FT) analyses of <0002> and <1100> lattice images of the QW region show a 4 to 10 % increase of the c-axis lattice spacing, across the full specimen width, and essentially no change in the a-axis value. The magnitude of the changes in the c-axis lattice spacing far exceeds values that would be expected by using a linear Vegard's law for GaN – InN with the measured In concentration. Therefore the increases are considered to represent tensile strains in the <0001> direction. Visual representations of the location and extent of the strained regions were produced by constructing inverse FT (IFT) images from selected regions in the FT covering the range of c-axis lattice parameters in and near the QW. The present strain values for InGaN QW in nanowires are larger than any found in the literature to date for other forms of InxGa1-xN (QW)/GaN.

This paper uses an efficient and accurate approach to estimate the hydrogen physical adsorption in various carbon structures. By comparing with previous Grand Canonical Monte Carlo (GCMC) and other methods on expanded graphite, the introduced method is shown to be accurate, but the calculation is much faster and more intuitive. Our preliminary results in amorphous carbons show high hydrogen uptake close to 0.8% at 300 K and moderate pressure.

Atom probe (AP) is known to be a unique instrument that makes possible to mass analyze a specimen at atomic level. However, its application is mostly limited to metals and semiconductors because the AP analysis proceeds by field evaporating surface atoms applying the high field, 20-40 V/nm, on the specimen surface. In order to generate such a high field the analyzed area is an apex of a sharp tip. Metals and semiconductors can be formed in such a sharp tip easily. However, the formation of a sharp organic and bio molecule tip is not easy. Thus, we introduced a funnel shaped micro extraction electrode that scans over a specimen surface and confines the high field in a narrow space between the micro open hole at the apex of the electrode and a micro protrusion on a specimen surface. Thus, this type of the AP is named as scanning atom probe (SAP). Then, organic and bio molecules can be deposited on the micro protrusion on the specimen surface. The AP analysis of metals indicates that the field evaporation of metal atoms proceeds one atom by one atom implying that the binding between metal atoms are uniform and non-directional. On the other hand most atoms of non-metallic specimens are field evaporated as clustering atoms. For example, doubly charged thiophene monomers are detected when polythiophene is analyzed. This indicates that one sulfur and four carbon atoms are strongly bound. Similarly, the mass spectra of highly pure single walled carbon nano tubes (SWCNT) exhibit sharp mass peaks of C2+ and C+ indicating that carbon atoms are bound by non-directional strong bonds. This implies that the unique feature of the AP is not only in the identification of individual ion but also in the investigation of binding states of the atoms forming the materials. For the present analysis amino acids are deposited on a small ball of the SWCNT fibers in order to avoid the catalytic reaction of metals. The SWCNT ball is dipped in a solution of sample molecules. The glycine solution is made by dissolving 1 gram of glycine in 15 ml pure water. Cystine, leucine and methionine solutions are made by dissolving 50 mg of the molecules in 1 ml of 0.1 N HCl. Discrimination of the carbon ions of the SWCNT from the fragment ions of the molecules is relatively easy because nearly all of the SWCNT carbon ions are detected as C2+ and C+. Glycine is the smallest amino acid formed by a carboxy group, an amino group and a CH2 group. Thus, it is assumed that the analysis will provide a guideline for the analysis of larger molecule. However, the identification of fragments ions is not easy because many different fragments have the same mass such as CH3 and NH. This indicates that mass analyzer for the bio-molecules requires a mass spectrometer with the mass resolution m/Δm higher than 10,000. The characteristic mass spectra of the amino acids and the structure of a new SAP with a position sensitive ion detector with a spiral delay line will be presented.

Recently, semiconductor nanocrystals or quantum dots (QDs) aroused great concern because of their unique properties such as the size-dependent photoluminescence. They have many excellent applications in areas of molecular bioimaging, medical detection and even energy, especially as biosensing and imaging instead of fluorescent dyes. For the bio-safety, however, we should assess the cytotoxicity of QDs before used in biomedical imaging. Here, the cytotoxicity of amino-functionalized CdSe/CdS (CdSe/CdS-NH2) QDs and carboxy-functionalized CdSe/CdS (CdSe/CdS-COOH) QDs was investigated by MTT assay method. According to our findings, both CdSe/CdS-NH2 and CdSe/CdS-COOH have a dose-dependent effect on cell proliferation. The cytotoxicity of QDs varies with storing time of QDs and kinds of cells. The cytotoxicity of QDs modified with -COOH or -NH2 groups both vary with concentrations in positive linear or change with QD storing time in negative linear. The results indicate that CdSe/CdS-COOH QDs have lower toxicity than CdSe/CdS-NH2 QDs. Hela cell is somewhat more sensitive to amino- and carboxy-modified QDs than Bel7404 cell for MTT assays.

We report a novel hybrid p-i-n heterojunction solar cell consisting of an undoped CdSe quantum dot film sandwiched between electrodeposited n-type ZnO nanowires on a compact ZnO thin film/FTO and a spin-coated hole-conducting layer. Microscopic studies show the conversion of CdSe quantum dots into conformal and continuous polycrystalline thin film coatings on ZnO nanowires upon annealing in CdCl2/ambient air. The morphology change of the CdSe quantum dot layers then provided excellent charge transfer between the absorber layer and the contiguous layers. The quantum-dot-sensitized ZnO nanostructured solar cells exhibited short-circuit current densities ranging from 5 to 10 mA/cm2 and open-circuit voltages of 0.4–0.6 V when illuminated with an 85 mW/cm2 quartz-halogen spectrum. External quantum efficiencies as high as 55–60% were also achieved.

Image deconvolution is introduced as an effective tool to enhance the determination of crystal structures and defects in high-resolution electron microscopy. The essence is to transform a single image that does not intuitively represent the examined crystal structure into the structure image. The principle and method of image deconvolution together with the related image contrast theory, the pseudo weak phase object approximation (pseudo WPOA), are briefly described. The method has been applied to different types of dislocations, twin boundaries, stacking faults, and one-dimensional incommensurate modulated structures. Results on the semiconducting epilayers Si0.76Ge0.24/Si and 3C-SiC/Si are given in some detail. The results on other compounds including AlSb/GaAs, GaN, Y0.6Na0.4Ba2Cu2.7Zn0.3O7-δ, Ca0.28Ba0.72Nb2O6 and Bi2.31Sr1.69CuO6+δ are briefly summarized. It is also shown how to recognize atoms of Si from C based on the pseudo WPOA, when the defect structures in SiC was determined at the atomic level with a 200 kV LaB6 microscope.

Smart Materials are those which can undergo a reversible property change in response to an external influence. An important polymeric Smart Material is poly(vinylidene fluoride), or PVF2, which is piezoelectric. The structure of PVF2 determines which crystal phases will be electrically active. Recent research has shown that the electrically active beta phase of PVF2 grows preferentially in nanocomposites of PVF2 mixed with organically modified silicates (OMS) ‘1-4’. These nanocomposite Smart Materials offer a new processing strategy for PVF2 piezo-films. Using PVF2 nanocomposites as the research focal point, a summer internship program was developed for deaf and hard of hearing (DHH) undergraduate students [5,6]. This paper describes the program and presents research results achieved by the interns. It is written from the perspective of the Principal Investigator, Cebe, on behalf of all the co-authors.

Reinforcement with nanotubes, nanofibers, and nanoparticles is an attractive option for enhancing the properties of micromachined polymeric structures employed in microelectromechanical systems (MEMS). Calculations based on Eshelby-Mori-Tanaka micromechanics predict that the elastic modulus and wave velocity can be increased by over an order of magnitude by reinforcing polymers with aligned, dispersed, single-walled carbon nanotubes (SWNT). Motivated by this prediction, we measured the elastic moduli of polyimide films reinforced with SWNT at volume fractions ranging from 0 to 10%. For dilute composites, the elastic modulus increased with increasing nanotube loading from 2.5 GPa for the neat polymer to 3.5 GPa for a nanocomposite containing 0.5 vol% of SWNT. However, with further increase in the nanotube content, the elastic modulus remained essentially constant even for high loadings of 10 vol% of SWNT. In addition, significantly different elastic moduli were measured for specimens containing the same volume fraction (0.5 vol%) of SWNT produced by two different processes.

X-ray topography data are compared with photodiode responsivity maps to identify potential candidates for electron trapping in high purity, single crystal diamond. X-ray topography data reveal the defects that exist in the diamond material, which are dominated by non-electrically active linear dislocations. However, many diamonds also contain defects configurations (groups of threading dislocations originating from a secondary phase region or inclusion) in the bulk of the wafer which map well to regions of photoconductive gain, indicating that these inclusions are a source of electron trapping which affect the performance of diamond X-ray detectors. It was determined that photoconductive gain is only possible with the combination of an injecting contact and charge trapping in the near surface region. Typical photoconductive gain regions are 0.2 mm across; away from these near-surface inclusions the device yields the expected diode responsivity.

The roles of minor organic layers in influencing the mechanical response of such biomineralized composites as mollusk shells and sponge spicules have been investigated. The mechanisms whereby such minor constituents govern energy dissipation in rigid biomineralized structures are discussed, and a rationale for new modes of toughening that may relate more generally to families of ceramic- or glass/organic composites is offered. New results of simple torsional tests conducted on spicule fibers of a hexactinellid sponge, Euplectella aspergillum (Euplectella a.), compared with those done on melt-drawn glass fibers, showed an enhanced ability to resist failure in torsion, whereas the glass fibers did not. This behavior was attributed to the presence of a very thin adhesive viscoelastic phase between the siliceous layers of the spicule fibers, combined with the architectural and surface features of the spicule fiber.

In this paper, the impurity influences of BNNTs on photoluminescence (PL) analysis have been investigated systematically. Similar PL spectra were obtained from bulk disk of the cold-pressed BNNTs and dispersed individual BNNTs deposited on CaF2 substrate. Metal impurities such as Fe and Au do not affect PL emissions of the BNNTs strongly possibly because Au doping creates sever structural damages but do not change the electronic structure.

To develop efficient organic and/or hybrid organic-inorganic solar energy devices, it is necessary to use, among other components, an active donor–acceptor layer with highly ordered nanoscale morphology. In an idealized morphology, the effectiveness of internal processes is optimized leading to an efficient conversion of photons to electricity. Using a poly(3-hexylthiophene)-block-poly(L-lactide) rod-coil block copolymer as a structure-directing agent, we have rationally designed and developed an ordered nanoscale morphology consisting of self-assembled poly(3-hexylthiophene) donor domains of molecular dimension, each of them separated by fullerene C60 hydroxide acceptor domains. Using this morphological control, one can begin to probe structure-property relationships with unprecedented detail with the ultimate goal of maximizing the performance of future organic/hybrid photovoltaic devices.

We investigated the formation mechanism and thermal behaviors of defects which were induced at a microscopic area inside (1120) sapphire. We used a femtosecond laser having a pulse width, wavelength, and repetition rate of 238 fs, 780 nm, and 1 kHz, respectively. Cracks were formed at the focal point along the {1102} and the {1100} planes by laser irradiation. The preferential crack formation on these planes was attributed to the different surface fracture energy between the crystallographic planes of sapphire. The cracks transformed into the array of discrete pores by the subsequent heat treatment above 1300 °C, which was due to the diffusive crack healing process. In addition, dislocations were also introduced at the interface between closed cracks.

The salt damage such as the snow melting salts in winter or the sea salt particle flying in the coast region has significant effect on the corrosive environment of the automobile. Moreover, the corrosive environment of the automobile become more severe by the wet/dry cyclic condition, for example, a car gets wet with the splash water and dryness by the thermal loading while driving. On the other hand, the further application of the high strength stainless steel to the automobile parts is expected because it can contribute durability and lightening. Then, it is important to clarify the corrosion characteristic of this material under the salt damage environment.In this study cold rolled type304 stainless steel pipe with shot peening were used to investigate the corrosion property of high strength type304 stainless steel for automotive applications in a salt damage environment. The hardness of the pipe was about HV450, and a clear difference was not admitted in the thickness direction. A crevice was created between the outside of the pipe and an O-ring, and the pipe was applied stress by press fitting of another part. The corrosion property of the sample was evaluated in an automotive field test in Okinawa. Cracking from a corrosion pit was observed in the crevice. The Electron Prove Micro Analysis（EPMA） indicated that pitting corrosion was caused by chloride (from sea salt) concentrated in the crevice. The crack occurred in the residual compressive stress layer created by shot peening. In this regard, it was confirmed by the XRD analysis that about 85% of the metallographic structure had been transformed into the martensite. And the observation of the metallographic structure by the Electron Back Scatter Diffraction（EBSD） clarified the crystal grain was greatly transformed by the strong processing. It means that the accumulation of strain occurred. These two factors are considered to raise the receptivity to the crack generation of this sample.A crack generated at a corrosion pit was reproduced in a wet/dry cyclic corrosion test after one flash of artificial seawater. To investigate the crack generating mechanism, a corrosion pit was previously generated on the sample by cyclic corrosion test, after which a cathodic charge test in artificial sea water was done. Similar cracking from a corrosion pit was observed on the sample after this test. Therefore, the cracking is presumed to be Hydrogen Embrittlement-Stress Corrosion Cracking（HE-SCC）