High electron mobility transistors (HEMTs) with a pseudomorphically strained InAs channel (InAs-PHEMTs) were fabricated, and their high frequency characteristics were estimated by measuring the S-parameters. For a VDS of 1.4 V and VGS of 0.3 V, InAs-PHEMTs showed an excellent intrinsic cut-off frequency (f T, int.) as high as 90 GHz regardless of their longer LG (0.7 μm). Since fT is known to be inversely proportional to LG to the first approximation, f T, int. of our InAs-PHEMTs may reach 630 GHz if their LG is reduced to 0.1 μm.

Moreover, we calculated the InAs-PHEMTs' energy state and potential profile by self-consistently solving the Schrödinger and Poisson equations. In solving the Schrödinger equation, the energy-dependent effective mass was employed to take into account the strong non-parabolicity of InAs conduction-band based on the k·p perturbation theory by E. O. Kane. It was clarified that most electrons are confined to the InAs layer. On the contrary, if the non-parabolicity is not taken into account, electrons will spread over the InGaAs channel layer.

We introduce defects into (1120) oriented highly N-doped 4H-SiC by surface scratching, bending and annealing in the brittle regime. Emerging defects at the sample surface are revealed by chemical etching of the deformed samples. The etch patterns are constituted of straight bulges and grooves exhibiting various topographical features. These etch figures correspond to the emergence of double stacking faults dragged by a pair of partial dislocations. In this paper, we discuss the links between the etch figure characteristics and the defect nature. Results obtained by optical and atomic force microscopy are completed by structural analysis of defects performed by transmission electron microscopy. Mobility of partial dislocations in 4H-SiC is discussed and correlated to their core composition and to the effect of the applied mechanical stress.

The ternary Nb-Cr-Al phase diagram exhibits extended phase fields of the cubic C15 and the hexagonal C14 Laves phases Nb(AlxCr1-x)2. A number of Nb-Cr-Al alloys were prepared by levitation melting and annealed at temperatures between 1150 and 1450 °C for up to 1500 h. Isothermal sections of the ternary Nb-Cr-Al phase diagram at 1150, 1300 and 1450 °C were obtained from electron probe microanalysis, X-ray powder diffraction and metallographic investigations in order to study the effect of Al on the stability and structure of the Laves phases. The C14 Laves phase in the Nb-Cr-Al system can dissolve up to 45 at.% Al by substituting Cr with Al on the two different crystallographic B-sites 2a and 6h of the C14 AB2 unit cell. The site occupations of the Al and Cr atoms on these two B-sites were determined by Rietveld analysis using the program FullProf. The experimental site occupation factors were compared to site occupation factors computed by a statistical mechanics approach based on first-principles electronic structure calculations. The experimental as well as the calculated site occupation factors indicate a preferred occupation of the 2a site by Al.

The remarkable ability of magnesium to store significant quantities of hydrogen has fostered intense research efforts in the last years in view of its future applications where light and safe hydrogen-storage media are needed. Magnesium material, characterized by light weight and low cost of production, can reversibly store about 7.7 wt% hydrogen. However, further research is needed since Mg has a high operation temperature and slow absorption kinetics that prevent the use in practical applications. For these reasons a detailed study of the interface between Mg and MgH2 is needed. Further insights are gained by characterizing the Mg-MgH2 system from both the experimental and the numerical point of view.

The study of the MgH2-Mg phase transformation in powder samples has been performed to gain detailed metallographic information. A method for studying this phase transformation by cross sectional samples scanning electron microscopy observation of partially transformed material has been developed. This method exploits the peculiar features of this system where the MgH2 phase is insulating and the Mg is a metallic conducting phase. This difference can induce a contrast between the two phases owing to the different secondary emission yield. Further insights are gained by characterizing Mg-MgH2 interfaces by means of accurate first-principle molecular dynamics simulations based on the density-functional theory. Extensive electronic structure calculations are used to characterize the equilibrium properties and the behavior of the surfaces in terms of total energy considerations and atomic diffusion.

High-pressure studies have been performed on heavy rare earth metals Terbium (Tb) to 155 GPa and Holmium (Ho) to 134 GPa in a diamond anvil cell at room temperature. The following crystal structure sequence was observed in both metals hcp ⟶ Sm-type ⟶ dhcp ⟶ distorted fcc (hR-24) ⟶ monoclinic (C2/m) with increasing pressure. The last transformation to a low symmetry monoclinic phase is accompanied by a volume collapse of 5 % for Tb at 51 GPa and a volume collapse of 3 % for Ho at 103 GPa. This volume collapse under high pressure is reminiscent of f-shell delocalization in light rare earth metal Cerium (Ce), Praseodymium (Pr), and heavy actinide metals Americium (Am) and Curium (Cm). The orthorhombic Pnma phase that has been reported in Am and Cm after f-shell delocalization is not observed in heavy rare earth metals under high pressures.

Storage of the UK's Intermediate Level Wastes (ILW), which comprises Magnox fuel cladding, uranium and small items of equipment exposed to radiation, is currently achieved via encapsulation within cementitious grout housed in 500 litre 316L stainless steel drums. The cements used display a high pH; in such an environment many metals form surface hydroxides or oxides. Magnox reacts with free water at high pH with the liberation of hydrogen whilst undergoing corrosion to form hydroxide species.

Corrosion of Magnox cladding has previously been monitored by measuring the rate of hydrogen evolution and/or weight loss. Recent work by our group has shown impedance techniques may also be useful in monitoring early corrosion behaviour. In this project electrochemical polarisation techniques will be employed to examine the corrosion behaviour of Magnox fuel in situations where it is in electrical contact with other metals, including uranium, and hence determine how galvanic effects influence corrosion behaviour. In this paper we describe the background to such experiments along with some preliminary results.

Silica-on-silicon label-free biosensor with PMMA (Poly(methyl methacrylate), as the functional layer was designed, fabricated, and tested. The sensor is based on Fabry Perot (FP) interferometry. Specific binding was tested with Human IgG and anti-Human IgG. Non-specific binding was tested with Human IgG and Mouse IgG. The testing results show that the sensor has a nearly six-fold greater response upon specific binding than upon non specific binding. Thermal and long term stability experiments show that the sensor is insensitive to the environment fluctuation. The fabrication process is simple without special surface treatment. In addition, this biosensor is inexpensive and easy to use.

Surface modification of the elastomer polydimethylsiloxane (PDMS) by exposure to oxygen plasma for four minutes creates a thin, stiff film. In this study, the thickness and mechanical properties of this surface-modified layer were determined. Using the phase image capabilities of a tapping-mode atomic force microscope (AFM), the surface-modified region was distinguished from the bulk PDMS; specifically, it suggested a graded surface layer to a depth of about 200 nm. Load-displacement data for elastic indentation using a compliant AFM cantilever was analyzed as a plate bending on an elastic foundation to determine the elastic modulus of the surface (37 MPa). An applied uniaxial strain generated a series of parallel nanocracks with spacing on the order of a few microns. Numerical analyses of this cracking phenomenon showed that the depth of these cracks was in the range of 300–600 nm and that the surface layer was extremely brittle, with toughness in the range of 0.1– 0.3 J/m2.

The Atmospheric Laser Doppler Instrument (ALADIN) is the payload of the ADM-AEOLUS mission, which will make direct measurements of global wind fields. It will determine the wind velocity component normal to the satellite velocity vector. The instrument is a direct detection Doppler Lidar operating in the UV, which will be the first of its kind in space.

ALADIN is now in its final construction stage: the integration of the Flight Model is on-going. Most of the subsystems have been integrated; the payload performance and qualification test campaign will commence.

This paper describes the ALADIN the development status and the results obtained at this stage. This regards the receiver performance, the telescope development and the challenges of the laser.

The paper will also provide insights on the ATLID instrument design which is the backscatter lidar for the EarthCARE mission. This lidar program is starting its detailed design phase.

The ALADIN and ATLID instruments are developed by EADS Astrium Satellites for the European Space Agency.

A novel ceramic synthesis technique, flame spray pyrolysis (FSP) was investigated for the production of nanophosphor particles. Among the various types of synthesis technique for phosphors, FSP is a powerful method which is capable of producing particles with good crystallinity and high luminescence efficiency. Red light emitting Eu3+ doped Y2O3 nanophosphor was prepared by FSP from nitrate based liquid precursors with high flame temperature. Flame temperature is an important factor to obtain phosphor particles with dense and spherical shape. Different molar percentage of urea was added into the precursor, addition of urea increases the temperature in the flame zone and promotes the formation of nano-size and spherical shaped particles. The importance of urea in the precursor to obtain well dispersed Y2O3:Eu3+ nanophosphor has been studied. The characteristics of nanophosphor such as crystallinity, morphology and photoluminescence in the presence of different moles of urea in nitrate based aqueous solution were investigated. On varying the overall concentration of the precursor, both the optical properties and crystallinity were investigated. XRD spectra showed as-prepared phosphors were obtained directly as cubic phase Y2O3:Eu3+ nanophosphor with high crystallinity and without any post-heat treatments. Luminescence intensity of nanophosphor increased with the amount of urea till 2 M percentages, further increase in urea concentration was found to reduce the PL intensity. We have developed a continuous single-step fabrication method for nanocrystalline Y2O3:Eu3+ nanophosphor without any post-heat treatments procedure.

Permalloy (Ni81Fe19) nanoparticles with diameters of hundreds of nanometers have been successfully fabricated by pulsed laser ablation (PLA) in air, distilled water, pure ethanol and sodium dodecyl sulfate (SDS) aqueous solutions. The permalloy nanoparticles made in SDS solutions are typically spherical in shape. Lower laser energy with lower frequency leads to the formation of smaller permalloy nanoparticles. Higher concentration of SDS results in smaller nanoparticles. Lastly, we found some unusual permalloy nanoparticles with interesting morphologies made by PLA in air, distilled water and ethanol.

Mixed-phase hydrogenated amorphous silicon thin films containing nanocrystalline silicon inclusions have been synthesized in a dual chamber co-deposition system. A PECVD deposition system produces small crystalline silicon particles (3-5 nm diameter) in a flow-through reactor, and injects these particles into a separate capacitively-coupled plasma chamber in which hydrogenated amorphous silicon is deposited. Raman spectroscopy is used to determine the volume fraction of nanocrystals in the mixed phase thin films, while infra-red spectroscopy characterizes the hydrogen bonding structure as a function of nanocrystalline concentration. At a moderate concentration of 5 nm silicon crystallites, the dark conductivity and photoconductivity are consistently found to be higher than in mixed phase films with either lower or higher densities of nanocrystalline inclusions.

Vitrification is currently the most widely used technology for the treatment of high level radioactive wastes (HLW) throughout the world. At the Savannah River Site (SRS) actual HLW tank waste has successfully been processed to stringent product and process constraints without any rework into a stable borosilicate glass waste since 1996. A unique “feed forward” statistical process control (SPC) has been used rather than statistical quality control (SQC). In SPC, the feed composition to the melter is controlled prior to vitrification. In SQC, the glass product is sampled after it is vitrified. Individual glass property models form the basis for the “feed forward” SPC. The property models transform constraints on the melt and glass properties into constraints on the feed composition. The property models are mechanistic and depend on glass bonding/structure, thermodynamics, quasicrystalline melt species, and/or electron transfers. The mechanistic models have been validated over composition regions well outside of the regions for which they were developed because they are mechanistic. Mechanistic models allow accurate extension to radioactive and hazardous waste melts well outside the composition boundaries for which they were developed.

To many Americans, nanotechnology remains a science of the future; most are unaware that nanoscale science is already being incorporated into products they use in their everyday lives. Informal learning environments are an ideal venue in which to not only educate the public about current applications of nanotechnology but also engage them in a discussion of its impacts. Developed through a partnership between two NSF-funded Materials Research Science and Engineering Centers at Penn State and Cornell Universities and The Franklin Institute in Philadelphia, the “Small Wonders: Find the Nano in Your Life” program has been distributed to 20 science and children's museums around the United States. This cart-based program includes interactive demonstrations of commercially available products that use nanoscale technology, including sunblock, nanosilver food containers, and nanoiron for environmental remediation. Macroscale models enable visitors to understand the underlying science, while real products allow visitors to explore the hope, hype, and reality of each. Here, we discuss the educational goals of the program, our approach to presenting questions of both science and policy, and methods and results of visitor evaluation. This third collaborative project continues to build on a model of program development and distribution that has been highly successful at reaching a broad audience.

We have carried out an ab initio simulation study of boron in amorphous silicon. In order to understand the possible structural environments of B atoms, we have studied substitutional-like (replacing one Si atom in the amorphous cell by a B atom) and interstitial-like (adding a B atom into an interstitial space) initial configurations. We have evaluated the Fermi-level dependent formation energy of the neutral and charged (±1) configurations and the chemical potential for the neutral ones. For the interstitial-like boron atom, we have find an averaged formation energy of 1.5 eV. For the substitutional case, we have found a dependence of the chemical potential on the distance to Si neighbors, which does not appear for the interstitial ones. From MD simulations, we could observe a diffusion event for an interstitial-like boron atom with a migration barrier of 0.6 eV.

Nanostructured tungsten trioxide films were fabricated with the technique of glancing angle deposition (GLAD) in a thermal evaporation chamber with a base pressure of 1.3 × 10−4 Pa. Films were deposited at vapor incidence angles of 0°, 20°, 40°, and 50° with film thickness varying between 160 and 200 nm, as determined by spectroscopic ellipsometry. After deposition, samples were heated for 1 h in air at 400 °C and were subsequently intercalated with small amounts (5 to 15 nm) of lithium by dry lithiation, a technique developed in our laboratory. Compared with our previous work on as-deposited nanostructured films, these samples showed significantly enhanced coloration in the infrared region. It was found that the films exhibited an absorption- based coloration in the lower wavelengths as well as an increased reflection in the infrared region. Morphological investigation by atomic force microscopy (AFM) showed grain agglomeration and increased surface roughness upon heating. Our studies further indicate that grain agglomeration significantly contributes to the superior coloration properties of the films.

We have observed the assembly of a chemically adsorbed monomolecularlayer (CAM) into microwires, connections, and an electric path according to the location within field regions of a lithographically patterned array of two platinum (Pt) electrodes. A Pt electrode/monolayer/Pt electrode junction was fabricated by the self-assembly of a rigid monomolecular, namely 3-{6-{11-(Trichlorosilyl) undecanoyl} hexyl} thiophene (TEN) with thiophen groups, in the lateral direction between the Pt gap electrodes. The technique of a conductive probe AFM (CP-AFM) has been used to investigate the forward bias conduction properties of a TEN film grown by a wet process deposition on a glass substrate. The self-assembly depends on: (1) the ideal rigidity of the chemically adsorptive monomolecular layer (CAM) and (2) the strong affinity of the thiophen end groups of the CAM for the Pt electrode. The current–voltage (I–V) characteristics of the conjugated thiophen junction exhibited stepwise features at room temperature. From the results in the atmosphere, the conductivity of a lateral conjugated polythiophen group was calculated to be 5.0E4 S/cm.

Laves phases comprise a large group of intermetallic compounds with general composition AB 2 and multi-component derivatives. The crystal structures of Laves phases are often regarded as closest packing of spheres. This observation, beginning with very early work on Laves phases, has led many researchers over the years, to emphasize the role of geometrical factors in the formation of Laves phases. In order to develop a firm understanding of chemical bonding in Laves phases and assess the importance of geometrical factors, we undertake a first-principles-electronic structure-based chemical bonding analysis for several representatives. As a first step towards this goal we concentrate on the K-Cs system which contains the Laves phase CsK2 and the hexagonal Cs6K7 compounds. In such alkali-metal-only compounds it is generally expected that chemical bonding effects are minimal. Atom volumina and charge transfer investigations reported here, however, suggest that even in alkali metal-alkali metal Laves phases chemical bonding plays a non-negligible role.

We synthesized a methanol electrocatalyst with high activity and low noble metal content. The electrocatalyst consists of carbon&supported PtRu nanoparticles, which have 1-2 Pt monoatomic layers on Ru nanocores. In spite of the pure Pt surface, the catalyst showed high catalytic activity when used in the anode of a direct methanol fuel cell. Clearly the underlying Ru atoms modified the property of the surface Pt atoms, bringing about the high catalytic activity.

We investigated crystallization processes of amorphous Si (a-Si) during the excimer laser annealing in the complete-melting and near-complete-melting conditions by using molecular dynamics simulations. The initial a-Si configuration was prepared by quenching liquid Si (l-Si) in a MD cell with a size of 50×50×150Å3 composed of 18666 atoms. KrF excimer laser (wavelength: 248nm) annealing processes of a-Si were calculated by taking account of the change in the optical constant upon melting during a laser pulse shot with the intensity Io exp[−(t–t0)2/ς2] (Io : laser fluence, t: irradiation time). The refractive indices of a-Si and l-Si were set at n+ik=1.0+3.0i and n+ik=1.8+3.0i, respectively. The simulated results well reproduced the observed melting rate and the near-complete-melting and complete-melting conditions were obtained for Io = 160mJ/cm2 and 180mJ/cm2, respectively. It was found that larger grains were obtained in the near-complete-melting condition. Our MD simulations also suggest that nucleation occurs first in a-Si and subsequent crystallization proceeds toward l-Si in the near-complete-melting case.