Localized surface plasmon resonances (LSPR), collective electron oscillations in nanoparticles, are being heavily scrutinized for applications in chemical and biological sensing, as well as in prototype nanophotonic devices. This phenomenon exhibits an acute dependence on the particle’s size, shape, composition, and environment. The detailed characterization of the structure-function relationship of nanoparticles is obscured by ensemble averaging. Consequently, single-particle data must be obtained to extract useful information from polydisperse reaction mixtures. Recently, a correlated high resolution transmission electron microscopy (HRTEM) LSPR technique has been developed and applied to silver nanocubes. We report here a second generation of experiments using this correlation technique, in which statistical analysis is performed on a large number of single particles. The LSPR dependence on size, shape, material, and environment was probed using silver right bipyramids, silver cubes, and gold cubes. It was found that the slope of the dependence of LSPR peak on size for silver bipyramids increases as the edges become sharper. Also, a plasmon shift of 96 nm was observed between similar silver and gold cubes, while a shift of 26 nm was observed, for gold cubes, between substrates of refractive index (RI) of 1.5 and 2.05.

Pyroelectric infrared (IR) detectors based on perovskite oxides are of interest in part because of their lack of need for cooling, which makes them relatively more affordable and operationally simpler than cooled photon detector systems. We are investigating two methods for low-cost growth of perovskite oxide thin films, namely, a bio-inspired, low-temperature synthesis method and a modified industry-standard metalorganic solution deposition (MOSD) method. Subsequent to film synthesis, we utilize direct-write laser phase conversion and micro-electro-mechanical systems (MEMS) fabrication for development of an uncooled IR focal plane array (FPA). Film growth, crystallization and MEMS processes are compatible with monolithic integration of the detector pixels directly onto Si readout integrated circuits (ROICs).

In this paper we report on the investigation of electrostatic forces between a conductive probe and semiconducting materials by means of Kelvin probe force microscopy measurements. Due to the formation of an asymmetric electric dipole at the semiconductor surface, the measured KPFM bias is related with the energy difference between Fermi energy and respective band edge. Quantitative Kelvin probe force microscopy measurements on semiconductors, namely on a conventional dynamic random-access memory cell and on a cross-sectionally prepared Si epilayer structure, are presented.

Zinalco alloy (Zn-21mass%Al-2mass%Cu) specimens were deformed superplastically with a strain rate (ε) of 1×10-3 s-1 at homologous temperature (TH) of 0.68 (5 ). It was observed neck formation that indicate nonhomegeneus deformation. Grain size and grain boundaries misorientation changes, due superplastic deformation, were characterized by Orientation Imagining Microscopy (OIM) technique. It was studied three regions in deformed specimens and the results were compared with the results for a specimen without deformation. Average grain size of 1 mm was observed in non-deformed specimen and a fraction of 82% for grain boundary misorientation angles with a grain boundaries angles between 15° and 55° was found. For deformed specimen, the fraction of angles between 15° and 55° was decreced to average value of 75% and fractions of low angle (<5°) and high angle (>55°) misorientations were 10% and 15% respectively. The grain size and high fraction of grain boundary misorientation angles between 15° and 55° observed in the alloy without deformation, are favorable for grain rotation and grain boundary sliding (GBS) procces. The changes observed in the fraction of favorable grain boundary angles during superplastic deformation, shown that the superplastic capacity of Zinalco was reduced with the deformation.

Integrating porous low-permittivity dielectrics into Cu metallization is one of the strategies to reduce power consumption, signal propagation delays, and crosstalk between interconnects for the next generation of integrated circuits. The porosity and pore structure of these low-k dielectric materials, however, also affect other important material properties in addition to the dielectric constant. In this paper, we investigate the impact of porogen loading on the stiffness and cohesive fracture energy of a series of porous organosilicate glass (OSG) thin films using nanoindentation and the double-cantilever beam (DCB) technique. The OSG films were deposited by plasma-enhanced chemical vapor deposition (PECVD) and had a porosity in the range of 7−45%. We show that the degree of porogen loading during the deposition process changes both the network structure and the porosity of the dielectric, and we resolve the contributions of both effects to the stiffness and fracture energy of the films. The experimental results for stiffness are compared with micromechanical models and finite element calculations. It is demonstrated that the stiffness of the OSG films depends sensitively on their porosity and that considerable improvements in stiffness may be obtained through further optimization of the pore microstructure. The cohesive fracture energy of the films decreases linearly with increasing porosity, consistent with a simple planar through-pore fracture mechanism.

High-quality Pt-Cu nanocubes were prepared through simultaneous reduction of platinum (II) acetylacetonate and copper II) acetylacetonate in 1-octadecene by 1,2–tetradecanediol in the presence of tetraoctylammonium bromide, oleylamine, and 1-dodecanethiol. The growth process of Pt-Cu nanocubes was explored based on the observation of intermediates. The electrocatalytic behavior indicates that cubic Pt-Cu nanocrystals are more active than spherical Pt-Cu nanocrystals and Pt nanocrystals towards methanol oxidation reaction.

The effects of FePO4 nanoscale coating on PtRu thin films were investigated on the block of Ru crossover. Ru dissolution was examined by the accelerated-potential cycles between 0.4 and 1.05 V. The results showed that Ru dissolution from FePO4-coated PtRu surface was inevitable due to the direct contact between the PtRu surface and aqueous electrolyte. However, the FePO4 coating layer on PtRu thin-film electrodes effectively retained the dissolved Ru species, thus preventing the dissolved Ru species from diffusing into the electrolyte. Moreover, the retained Ru species within the FePO4-coating layer were redeposited onto the PtRu surface during the cycling in the fresh electrolyte.

We have characterized the surface charge on a variety of GaN samples using two surface potential techniques, conventional Kelvin probe and scanning Kelvin probe microscope (SKPM). Kelvin probe was primarily used to measure the change in surface potential under UV illumination, otherwise known as the surface photovoltage (SPV). Due to band bending near the semiconductor surface of about 1 eV in dark conditions, the SPV signal for n-type GaN typically reaches 0.5 to 0.6 eV upon switching on UV light. This value can slowly decrease by up to 0.3 eV during UV illumination in air ambient for 2-3 hours. We report that samples with many hours of ambient UV exposure do not show this slow decrease during SPV measurements, consistent with the UV-induced growth of a thicker surface oxide that limits charge transfer. In addition to prolonged UV exposure, the surface contact potential was also manipulated by local charge injection. In this procedure, the surface is charged using a metallized atomic force microscope tip which is scanned in contact with the sample. Subsequent SKPM measurements indicate an increase or decrease in the surface contact potential for the charged region, depending on the applied voltage polarity. Measurements of the discharge behavior in dark for these regions show a logarithmic time behavior, similar to the decay behavior during our observations of SPV transients after switching off the light. As expected, illumination of the surface increases the discharge rate and restores the charged area to its original state.

Microstructured semiconductor neutron detectors have superior efficiency performance over thin-film coated planar semiconductor detectors. The microstructured detectors have patterns deeply etched into the semiconductor substrates subsequently backfilled with neutron reactive materials. The detectors operate as pn junction diodes. Two variations of the diodes have been fabricated, which either have a rectifying pn junction selectively formed around the etched microstructures or have pn junctions conformally diffused inside the microstructures. The devices with the pn junctions formed in the perforations have lower leakage currents and better signal formation than the devices with selective pn junctions around the etched patterns. Further, pulse height spectra from conformally diffused detectors have the main features predicted by theoretical models, whereas pulse height spectra from the selectively diffused detectors generally do not show these features. The improved performance of the conformal devices is attributed to stronger and more uniform electric fields in the detector active region. Also, system noise, which is directly related to leakage current, has been dramatically reduced as a result of the conformal diffusion fabrication technique. A sinusoidal patterned device with 100 μm deep perforations backfilled with 6LiF was determined to have 11.9 ± 0.078% intrinsic detection efficiency for 0.0253 eV neutrons, as calibrated with thin-film planar semiconductor devices and a 3He proportional counter.

In this paper, fired and non-fired direct PECVD deposited Si-SiNx interface properties with and without NH3 pretreatment on both n- and p-type mono-crystalline silicon samples were investigated with deep-level transient spectroscopy (DLTS) measurements. A and B defect states are identified at the Si-SiNx interface. Energy-dependent electron and hole capture cross sections were measured by small-pulse DLTS. Fired samples with NH3 pretreatment show the lowest DLTS signals, which suggests the lowest overall Dit. The combination of NH3 pretreatment and firing is also suggested for application in the solar cell fabrication.

Large amplitude coherent optical phonons have been investigated in laser-excited Bismuth by means of femtosecond time-resolved X-ray diffraction. For absorbed laser fluences above 2 mJ/cm2, the experimental data reveal an extreme softening of the excited A1g-mode down to frequencies of about 1 THz, only 1/3 of the unperturbed A1g-frequency. At even stronger excitation the measured diffraction signals no longer exhibit an oscillatory behavior presenting strong indication that upon intense laser-excitation the Peierls-distortion, which defines the equilibrium structure of Bismuth, can be transiently reversed.

With relatively high gravimetric and volumetric hydrogen storage capacities, borohydrides have attracted interest as potential hydrogen storage media. Lithium borohydride has a maximum theoretical gravimetric hydrogen storage density of 18.4 wt%, and has been shown to be reversible when heated to 600°C in 350 bar hydrogen1. It is hoped that a greater understanding of the decomposition and reformation mechanisms, may lead to the development of LiBH4-based materials that can absorb and desorb hydrogen under less extreme conditions. However, these studies have proved a challenge: currently most in-situ investigations have used x-ray diffraction or neutron diffraction however these cannot readily give information on non-crystalline or liquid phases. The preparation of samples measured ex-situ via XRD, NMR2 and Raman3 have shown the reaction products and stable intermediates during the thermal decomposition, however, it is very difficult to detect short lived intermediate (or byproduct) species. Raman spectroscopy has the advantages that: materials with only short-range order can be analysed; and by focusing the laser on regions in a sample the reaction path can be monitored with changing temperature with a rapid scan rate.

After heating lithium borohydride through its phase change and melting point, shifts in peak position and peak width were observed, which agreed with other studies4. A sample was also heated to 500°C (under 1 bar Ar) to decompose the sample. A number of intermediates and reaction products have been predicted and observed ex situ. This work shows the in situ formation of lithium dodecaborane (Li2B12H12) and amorphous boron from liquid lithium borohydride. It is therefore possible to determine at what temperatures certain intermediates and products form.

We discuss defect engineering strategies in radiation detector materials. The goal is to increase resistivity by defect-induced Fermi level pinning without causing defect-induced reductions in the carrier drifting length. We show calculated properties of various intrinsic defects and impurities in CdTe. We suggest that the defect complex of a hydrogen atom and an isovalent impurity on an anion site may be an excellent candidate in many semiconductors for Fermi level pinning without carrier trapping.

This paper presents the mechanical characterization of the elastic modulus, hardness and fracture toughness of silicon oxynitride films (SiON) with different oxygen and nitrogen content, subjected to thermal annealing processed at 400 °C and 800 °C. The Fourier-transform infrared (FT-IR) spectroscopy was employed to characterize the SiON films with respect to the absorbance peak in the infrared spectrum. The nanoindentation testing showed that both the elastic modulus and hardness slightly increased after thermal annealing. Finally, the fracture toughness of the SiON films were estimated using Vickers micro-indentation tests and the result revealed that the fracture toughness decreased with increasing rapid thermal annealing (RTA) temperature and nitrogen content. We believe these results benefit microelectromechanical systems (MEMS) in regards to maintaining the structural integrity and improving reliability performance.

Hydrogen incorporation is studied in two Microwave Plasma CVD nanocrystalline diamond films deposited with prolongated BIAS or not during the growth step. The hydrogen content and bonding forms are analysed by Secondary Ion Mass Spectrometry, Raman and Fourier Transformer Infrared Spectroscopy. Our results show a high hydrogen concentration up to 3.1021 cm-1, as expected in nanocrystalline diamond, and in good agreement with the sp2 phase rate measured by Raman spectroscopy . The FTIR spectra exhibit two sharp peaks at 2850 and 2920 cm-1 and show that a fraction of hydrogen is bonded to sp3 CH2 groups. Hydrogen desorption experiments are performed to analyse the local structure modification of the diamond films.

Most designs of disposal facilities for higher toxicity radioactive wastes were developed for generic feasibility assessment and hence tend to be rather simple in terms of layout and conservative in the choice of engineered barrier materials. Recently, there has been a trend to reassess such designs in the light of moves towards implementation, where robustness in terms of post closure safety needs to be balanced against the requirements to assure safety, quality, and economic practicality during operation, to minimise environmental impact and to gain public acceptance. Studies to date have, however, tended to focus predominantly on variants of layout and engineered barrier geometry. Evaluation of alternative materials has received less consideration, despite the huge advances in materials science over the last couple of decades and likely further developments in the time until repositories become operational. This paper will examine the constraints that led to the choice of the most common materials selected for barriers within “wet” host rocks and examine the extent to which performance could be optimised by use of alternative materials.

Ultrafast time-resolved X-ray diffraction has been used to study the dynamics of coherent acoustic phonons in fs laser-excited Ge and Au, with the particular goal to clarify the interplay of the electronic and thermal pressure contributions. For semiconductors it is usually assumed that the electronic pressure is the dominant driving force. Our measurements reveal that in Ge the relative strength of the electronic pressure decreases with increasing laser fluence. Only for low fluences the electronic pressure dominates, while at high fluences the thermal pressure exceeds the electronic pressure. For the case of Au the data are well described within the established theoretical framework using the known values for those material parameters which determine the laser-induced pressure, namely the energy relaxation time and the electronic and lattice Grüneisen parameters.

The Low Frequency Noise (LFN) characteristics of Organic Light Emitting Diodes (OLEDs) were investigated in relation to device degradation. The standard layer structure of indium tin oxide (anode), hole transport layer, Alq3, Lithium Fluoride and Aluminium (cathode) was used. With duration of operation, the device degradation is characterized by an eventual drop in the luminance level and the electroluminescence efficiency. Additionally, the driving voltage at a fixed current and the LFN increase gradually during device degradation, accompanied with the formation of non-emissive areas (dark spots). It is found that the coefficient of correlation between voltage fluctuations across the device and low frequency fluctuations of the optical signals remains constant for an initial period and then decreases exponentially with duration of operation and is a sensitive parameter to predict OLED device lifetime. For a number of OLEDs driven at constant current, the device with higher initial correlation coefficient possesses a longer lifetime. The direct relation between LFN correlation and device lifetime can be explained by carrier recombination mechanisms at the microscopic level. An increase in trap density can reduce the internal radiative recombination rate which at the macroscopic level is reflected by a decrease in the correlation coefficient.

We report solvothermal preparations of nanocrystalline CuIn1-xAlxSe2 materials prepared from the reaction of Se, CuX2 (X = Cl− or stearate), InCl3, and Al(oleate)3 in refluxing oleylamine for 30 minutes to 3 hours. Scanning electron microscopy (SEM) images reveal morphologies consisting of hexagonal plates (100-400 nm diameter) with smaller isomorphic nodules. Micro-Raman spectroscopy, x-ray diffraction, and optical bandgap data are consistent with Al3+ incorporation into the chalcopyrite structure. For aluminum-containing reactions, product Al/(In+Al) ratios are estimated to be between 0.15 and 0.35 regardless of the indium-aluminum stoichiometry employed in the reaction. When Se is added to the reaction last, the reaction pathway involves an early-formed Cu2-xSe(s) intermediate that appears to react with In- and Al-containing species simultaneously. This intermediate is avoided when heating InCl3, Al(oleate)3, and Se together prior to Cu addition, but the final product includes Se contamination that must be removed or reacted by annealing.

The biocompatibility of 6H-SiC (0001) surfaces was increased by more than a factor of six through the covalent grafting of NH2 terminated self-assembled monolayers (SAM) using APDEMS and APTES molecules. Surface functionalization began with a hydroxyl, OH, surface termination. The study included two NH2 terminated surfaces obtained through silanization with APDEMS (aminopropyldiethoxymethylsilane) and APTES (aminopropyltriethoxysilane) molecules (hydrophilic surfaces) and a CH3 terminated surface produced via alkylation with 1-octadecene (hydrophobic surface). H4 human neuroglioma and PC12 rat pheochromocytoma cells were seeded on the functionalized surfaces and the cell morphology was evaluated with atomic force microscopy (AFM). In addition, 96 hour MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assays were employed to evaluate the cell viability on the SAM modified samples. The biocompatibility was enhanced with a 2 fold (171-240%) increase with 1-octadecene, 3-6 fold (320-670%) increase with APDEMS and 5-8 fold (476-850%) increase with APTES with respect to untreated 6H-SiC surfaces.