Locally Er3+-doped noncongruent, Li-deficient Ti:Er:LiNbO3 strip waveguide was fabricated with a technological process in sequence of preparation of Li-deficient LiNbO3 substrate using Li-poor vapor transport equilibration (VTE), Er3+, and Ti4+ diffusion in wet O2. The Li2O content change was evaluated from the measured birefringence. The Ti4+ and Er3+ profile characteristics in the waveguide were studied by secondary ion mass spectrometry. The results show that the VTE and subsequent Er3+ diffusion procedures resulted in totally ∼0.8 mol% Li2O content reduction. The Ti4+ profile follows a sum of two error functions in the width direction and a Gaussian function in the depth direction of waveguide. The Er3+ profile follows also a Gaussian function. At 1130 °C, the Ti4+ surface/depth diffusivity and surface concentration are 8.5 ± 1.3/1.98 ± 0.06 μm2/h and ∼7 mol%, respectively, and the Er3+ diffusivity and surface concentration are (12.8 ± 0.3) × 10−2 μm2/h and ∼0.6 mol%, respectively.

Using scanning near-field lithography (SNP), it is possible to pattern molecules at surfaces with a resolution as good as 9 nm [M. Montague, R. E. Ducker, K. S. L. Chong, R. J. Manning, F. J. M. Rutten, M. C. Davies and G. J. Leggett, Langmuir 23 (13), 7328–7337 (2007)]. However, in common with other scanning probe techniques, SNP has previously been considered a serial process, hindering its use in many applications. IBM’s “Millipede” addresses this problem by utilizing an array of local probes operating in parallel. Here, we describe the construction of two instruments (Snomipedes) that integrate near-field optical methods into the parallel probe paradigm and promise the integration of top–down and bottom–up fabrication methods over macroscopic areas. Both are capable of performing near-field lithography with 16 probes in parallel spanning approximately 2 mm. The instruments can work in both ambient and liquid environments, key to many applications in nanobiology. In both, separate control of writing is possible for each probe. We demonstrate the deprotection of self-assembled monolayers of alkylsilanes with photocleavable protecting groups and subsequent growth of nanostructured polymer brushes from these nanopatterned surfaces by atom-transfer radical polymerization.

Oxidized starch (OSt) films reinforced with natural halloysite were prepared by adding modified natural halloysite nanotubes into an OSt matrix. The halloysite/OSt films were characterized by x-ray diffraction, scanning electron microscopy, and ultraviolet spectrometry. The mechanical properties and moisture absorbability of the films were also studied. The modified halloysite nanotubes were well distributed in the starch matrix, and the tensile strength (TS) of the films was greatly enhanced, but the moisture adsorption ability of the films only changed slightly. The flexibility of the films was improved by adding glycerol but at a cost of reducing the TS. Incorporating a small amount of poly(vinyl alcohol) (PVA) improved both the TS and the percent elongation at break of the halloysite/OSt films.

The bipolar plate is one of the most important components in proton exchange membrane fuel cell. In this article, the graphite/polymer composite bipolar plates have been developed by compression molding technique. The study on effects of different resin types on the electrical conductivity, mechanical property, and corrosion performance of the composite bipolar plates shows that the properties of graphite/novolac epoxy (NE) plate are all better than those of graphite/phenol formaldehyde resin plate. The triple continuous structure provides graphite polymer blends with high electrical conductivity, high flexural strength, less porosity, and high density. Most of the properties, such as electrical conductivity, flexural strength, water adsorption, porosity, and so on, are affected by the properties of the polymer. The graphite/NE composite bipolar plate when used in the unit fuel cell assembly showed single-cell performance comparable to that of the commercially available graphite bipolar plates.

Thick (>150 μm) beryllium coatings are studied as an ablator material of interest for fusion fuel capsules for the National Ignition Facility. DC magnetron sputtering is used because of the relative controllability of the processing temperature and energy of the deposits. However, coatings produced by DC magnetron sputtering leak the fuel gas D2. By using ion-assisted DC magnetron, sputtered coatings can be made that are leak-tight. Transmission electron microscopy (TEM) studies revealed microstructural changes that lead to leak-tight coating. Ultrasmall angle x-ray spectroscopy is used to characterize the void distribution and volume along the spherical surface along with a combination of focused ion beam, scanning electron microscope, and TEM. An in situ multibeam optical stress sensor was used to measure the stress behavior of thick beryllium coatings on flat substrates as the material was being deposited.

Herein rutile (TiO2) single-crystal surfaces, with (001) and (100) orientations, were indented with hemispherical indenters with radii of 13.5, 5, and 1.4 μm. By converting the load–displacement data to nanoindentation (NI) stress–strain curves, together with microscopic post-indentation observations, we conclude that in the (001) orientation, plastic deformation occurs by the activation of all four {101}<10> slip systems. In the (100) orientation, only two of the four {101}<10 > slip systems, along with {100}<00> slip, are activated. Because the four {101}<10> slip systems in the (001) orientation intersect, the surface is harder and exhibits higher hardening rates after the nucleation of dislocations. The latter are manifested by pop-ins, some of which are large. The pop-in stresses are adequately described by Weibull statistics and were significantly higher for the (001) orientation. The elastic moduli, determined from spherical NI stiffness versus contact radii plots, were 349 ± 5 and 229 ± 4 GPa for (001) and (100) orientations, respectively. Fully spontaneous reversible, stress–strain hysteretic curves—only manifest in the (100) orientation—are attributed to the to-and-fro motion of dislocations comprising incipient kink bands in the {100}<00> slip system.

Novel lightweight intermetallic titanium aluminides, so-called γTiAl, provide good strength and creep resistance up to 700 °C. Their stress–strain behavior at room temperature is however strongly confined in elongation due to their low ductility. For studying the stress–strain behavior of γTiAl, the viscoplastic mechanical properties are determined using spherical indentation testing. The identification problem is solved on the continuum level by neural network analysis, which is based on a unified viscoplasticity model. The identified material parameters are validated by comparing the predicted stress–strain behavior with conventional compression tests at different deformation velocities. It was found that the average response of the indentation tests is in good agreement with the compression tests of round bars. Using a spherical indenter tip of R = 0.2 mm, a small volume is tested, offering possibilities for investigation of local property variations due to processing. The experimental indentation curves exhibited wide hysteresis loops, revealing the existence of pure kinematic hardening. Since tensile fracture strength for γTiAl is very low, microcracking occurred during loading as well as during unloading, significantly contributing to the unloading compliance.

We report on the electrical and structural properties of boron-doped diamond tips commonly used for in-situ electromechanical testing during nanoindentation. The boron dopant environment, as evidenced by cathodoluminescence (CL) microscopy, revealed significantly different boron states within each tip. Characteristic emission bands of both electrically activated and nonelectrically activated boron centers were identified in all boron-doped tips. Surface CL mapping also revealed vastly different surface properties, confirming a high amount of nonelectrically activated boron clusters at the tip surface. Raman microspectroscopy analysis showed that structural characteristics at the atomic scale for boron-doped tips also differ significantly when compared to an undoped diamond tip. Furthermore, the active boron concentration, as inferred via the Raman analysis, varied greatly from tip-to-tip. It was found that tips (or tip areas) with low overall boron concentration have a higher number of electrically inactive boron, and thus non-Ohmic contacts were made when these tips contacted metallic substrates. Conversely, tips that have higher boron concentrations and a higher number of electrically active boron centers display Ohmic-like contacts. Our results demonstrate the necessity to understand and fully characterize the boron environments, boron concentrations, and atomic structure of the tips prior to performing in situ electromechanical experiments, particularly if quantitative electrical data are required.

Nanocomposite Cr–Si–N films were prepared on to Ti–6Al–4V substrates by a novel duplex surface treatment technique. Coatings consisting of a Cr3Si surface layer were deposited using a double cathode glow plasma and subsequent surface plasma nitriding. The surface topography, chemical composition, and microstructure of these treated alloys were analyzed by a variety of surface characterization techniques. The resulting Cr–Si–N films consisted of nanocrystallite CrN grains embedded in amorphous SiNx phase. Nanoindentation tests showed that with increasing nitrogen partial pressure the hardness of the Cr–Si–N films increased and the elastic modulus decreased. Wear experiments showed that the Cr–Si–N films produced at a nitrogen partial pressure of 4.5Pa and 800 °C possessed the lowest wear rate and friction coefficient. Moreover, electrochemical measurements in 5 wt% HCl solution indicated that the Cr–Si–N films acted as an effective barrier against acid attack on the alloys.

ZnO crystals have been investigated by scanning cathodoluminescence microscopy and spectroscopy at 80 K following hydrogen incorporation by plasma exposure. The intensity of the ZnO near-band-edge (NBE) emission is greatly enhanced while the defect-related green emission is quenched following plasma treatment. These effects are attributed to the passivation of zinc vacancies by hydrogen. The green and yellow intensities and their intensity ratios to the NBE vary with excitation depth for both undoped and H-doped ZnO crystals. The intensities of the green and yellow emissions exhibit sublinear dependencies on electron beam excitation density while the NBE intensity increases linearly with the excitation density. These saturation effects with increasing excitation density must be taken into account when assessing defects in ZnO by luminescence characterization.

In reactive templated grain growth (RTGG), oriented template crystals are used to seed both phase formation and crystallographic orientation in textured ceramics. This mechanism differs substantially from templated grain growth (TGG), in which texture forms via grain growth mechanism. In this work, characteristics of both RTGG and TGG processes are evaluated in [001] textured Sr0.61Ba0.39Nb2O6 ceramics produced from reactive SrNb2O6 and BaNb2O6 matrix powders and acicular KSr2Nb5O15 (KSN) templates. Above 1100 °C, SrxBa1−xNb2O6 (SBN) forms by oriented nucleation and growth on KSN (the RTGG process) and by nucleation of nonoriented matrix grains. RTGG occurs without densification or coarsening until phase formation is complete (∼1250 °C) and accounts for ∼60% of the texture in dense SBN ceramics. A later TGG process occurs from 1250–1350 °C and is characterized by simultaneous densification, grain growth, and additional texture development.

Mg2Si1−xSnx compounds are promising as “environmentally friendly” thermoelectric (TE) materials. For years, investigations of the TE properties of these compounds have been hindered by the poor reproducibility in sample preparation. In this work, we used a recently developed simple B2O3 flux method to prepare Mg2Si1−xSnx compounds over a wide composition range (0.1 ≤ x ≤ 0.8). The phase structure, microstructure, and TE properties have been investigated. We found that a miscibility gap existed at 0.2 ≤ x ≤ 0.45, substantially lower than the more generally accepted values 0.4 ≤ x ≤ 0.6, and a low lattice thermal conductivity of 1.4 W·m−1·K−1 in undoped Mg2Si0.55Sn0.45, which led to a ZT ∼0.3 at 550 K. These results constitute a solid basis for investigating further optimization of the Mg2Si1−xSnx-based TE materials via doping and possibly nanostrucuring approaches.

Based on a citric acid-assisted hydrothermal method, series of Ce3+/Tb3+ activated fluorides have been synthesized. By controlling the amount of KNO3, the final products evolve from the Ce3+/Tb3+ codoped orthorhombic phase GdF3 to the Ce3+/Tb3+ codoped cubic phase KGdF4. The concentration of Ce3+ has great effects on the crystalline phases and the morphologies of final products. The Ce3+ concentration dependent samples illustrate the appearance of the hexagonal phase solid solution CeF3–GdF3–TbF3 in the final products. When the Ce3+ concentration is 20 mol%, the sample Ce20 presents the hexagonal phase CeF3 but the diffraction peaks move to higher degree. The x-ray diffraction patterns suggest the phase evolution of final products, the field emission scanning electron microscopy images present the variation in morphology of samples, and the photoluminescence excitation and emission spectra as well as the luminescent dynamic curves illustrate the optical properties of samples.

Optical emission spectroscopy (OES) was used to study plasmas generated by a novel plasma-enhanced linear antennas microwave chemical vapor deposition system for nanocrystalline diamond (NCD) growth in gas mixtures of H2 + CH4 + CO2. Atomic hydrogen intensities were investigated for pulsed plasmas and continuous wave (CW) mode plasmas. OES was used to study the effect of pressure (0.38–2 mbar), microwave pulse frequency (3.8–25 kHz), and total gas flow (125–1000 sccm). By using the Boltzmann plot for atomic hydrogen line intensities, plasma electron temperatures for pulsed and CW plasmas were calculated. During experiments, NCD films were deposited, which were investigated by secondary electron microscopy and Raman spectroscopy in terms of surface crystalline morphology and nondiamond carbon content. NCD films produced in high pulse frequency plasmas show low sp2 content (less than 5%) and homogenous crystalline structure with only a small amount of crystalline defects.

Schottky diodes have been fabricated on metalorganic chemical vapor deposition GaN epitaxial layers grown on sapphire substrates. Carbon impurities limit the ability of these films to be used in high-power devices. Although its effect can be mitigated by growing the films at higher pressure, higher flow rates, and larger V/III ratios, it still effectively limits the net carrier concentration to ∼1016 cm−3 and therefore the breakdown voltage to ∼1200 V by acting as a compensating deep acceptor for n-type material. The net carrier concentration is smaller than the carbon concentration indicating that not all of the carbon occupies a nitrogen site acting as a deep acceptor. It is not known whether some of the carbon occupies gallium sites acting as a donor, interstitial sites creating states in the midgap region, and/or is tied up in the large number of dislocations in the films where it is not electrically active.

The current-induced interfacial reactions in the Ni/Sn-3.0Ag-0.5Cu/Au/Pd(P)/Ni–P (ENEPIG) flip chip interconnects and the failure mechanism during electromigration (EM) were reported. When ENEPIG was the cathode, EM significantly enhanced the consumption of Ni–P leaving a Ni3P layer; once the Ni–P was completely consumed, the growth of Ni2SnP was accelerated. The dissolved Ni atoms from the Ni–P and the interfacial intermetallic compounds (IMCs) were driven toward the anode upon electron current stressing and precipitated as large (Ni,Cu)3Sn4 IMCs. The excessive consumption of Ni–P and the formation of voids were responsible for the EM-induced failures. When Ni was the cathode, the rapid localized dissolutions of Ni under bump metallization (UBM) and Cu pad in the current crowding region resulted in a two-stage transformation of interfacial IMCs at the opposite Ni–P/solder interface. The localized dissolutions of Ni UBM and Cu pad on chip, as well as the formation of voids, were responsible for the EM-induced failures.

Two high-temperature pore generators (porogens) have been used to study the effect of porogen structure on moisture uptake and k-value in methylsilsesquioxane/porogen hybrid films and their corresponding porous films in a postintegration porogen removal scheme. Poly(styrene-b-4-vinylpyridine) containing di-block structure and pyridine polar group leads to higher moisture uptake and k-value in the hybrid films as compared to poly(styrene-block-butadiene-block-styrene) with symmetrical structure and nonpolar groups. Moreover, the moisture uptake behavior in both as-prepared hybrid films is in physical sorption mode based on their reversible adsorption–desorption curve measured by quartz crystal microbalance. After porogen removal, the k-values of porous films are favorably not influenced by porogen structures, and their moisture uptake is as low as 1.78 wt% even at 40 vol.% porosity. However, based on the simulation of the modified-Rayleigh model, the porous films are found to possess 0.4 vol.% chemisorbed moisture on the pore surface, resulting in 17–23% deviation from the ideal k-values.