We report properties of devices made by the adhesion of semiconductor crystals, including several tetracene specimens, to polymer gate dielectrics along with measurements of tetracene crystals on conventional Si/SiO2 dielectric surfaces. For the best tetracene, pentacene, and alpha-6T devices, mobilities exceeding 0.1 cm2/V were measured, correlating well with expectations based on the literature, and in the case of tetracene and alpha-6T, exceeding the thin film mobility value. The devices were prepared in the open laboratory using simpler crystal handling techniques than had been thought necessary.

By using molecular dynamics simulations, we have accurately determined the true contact area during plastic indentation of materials under an applied in-plane stress. We found that the mean pressure calculated from the true contact area varied slightly with applied pre-stress with higher values in compression than in tension and that the modulus calculated from the true contact area is essentially independent of the press-stress level in the substrate. These findings are largely consistent with the findings of Tsui, Pharr, and Oliver. On the other hand, if the contact area is estimated from approximate formulae, the contact area is underestimated and shows a strong dependence on the pre-stress level. When it is used to determine mean pressure and modulus, the empirically determined area leads to large errors. Our simulations demonstrate that this phenomenon, first reported for macroscale hardness measurements dating back to 1932, also exists at the nanometer-scale contact areas, apparently scaling over 10 orders of magnitude in contact area, from ∼mm2 to ∼100 nm2.

Wet-chemical and electrochemical routes were used to synthesize zinc oxide nanoparticles showing peculiar luminescent properties. ZnO-I are the nanoparticles that show only band gap ultraviolet (UV) emission, whereas ZnO-II type nanoparticles show the defect green luminescence along with the UV emission. Photoluminescence excitation (PLE) spectra of ZnO-I nanocrystals exhibit a single feature located at about 368 nm whereas ZnO-II nanocrystals show two features in PLE: a prominent feature at about 368 nm which is size dependent and a hump at 325 nm. These results are discussed in detail in view of the luminescence behavior in ZnO quantum particles.

Ho ion solubility and diffusivity were evaluated in barium titanate ceramics in which Ho ions were implanted with an accelerating voltage of 500 keV. The depth profile of the ions was composed of three regions in the post-annealed sample: the first was the precipitation region, the second was a region created by lattice diffusion of Ho ions, and the third was a region created by grain-boundary diffusion. The Ho lattice diffusion characteristics were similar to those of Ni ion diffusion in barium titanate ceramics, and we concluded that the diffusion mechanism was the same as that responsible for Ni ions. The Ho ions diffused through the B-site (Ti-site) and were then exchanged with A-site ions. This mechanism suggests that a small number of Ho ions dissolved in the B-site. Preferential grain-boundary diffusion was also observed. The grain-boundary diffusion coefficients were four to five orders of magnitude larger than the volume diffusion coefficients. The solubility of Ho ions was estimated to be a few thousand parts per million in barium titanate ceramics.

Eu(DBM)3phen-doped poly(methyl methacryate) (PMMA) with different doping concentration were prepared. The highest doping concentration sample (10000 ppm) was examined by near-field scanning optical microscopy (NSOM) with a resolution of 50 nm; and the result showed that there were no aggregates larger than 50 nm in the doped polymer. This result was further confirmed by optical properties of the doping material. Concentration quenching was not detected by metastable-state lifetime measurements, indicating that no aggregates existed. According to the fluorescence spectra analysis, the relative intensity ratio (R) of 5D0→7F2 to 5D0→7F1 transition was not shown to be significantly changed with the increasing of Eu3+ content. The analysis reflected that the local structure and asymmetry in the vicinity of europium ions were not changed, and that the Eu3+ ions in PMMA were homogeneously dispersed.

Based on static electromagnetics theory and thermodynamics theory, a new model is proposed to describe the phase separation from the glass doped with metal particles in a static electric field. This model is proved by a heat-treatment experiment of boracic silicate glass doped with gold. The results indicate that the externally applied electric field promotes the phase separation of the glass and leads to a different size of the droplet phase just as this new model has predicted.

Ca-doped lead zirconate titanate (52/48) thin film capacitors were prepared on electroless nickel-coated copper foils for embedded capacitor applications. The impact of Ca doping and process parameter variations was studied. Ca addition significantly reduced the temperature coefficient of capacitance. Specifically, the temperature variation was reduced to less than 10% between 300 and 580 K through calcium addition. Optimized capacitance densities and loss tangents were 400 nF/cm2 and 0.02, respectively. Crystallization temperatures of 600 °C yielded these optimized electrical properties, while higher temperatures resulted in interfacial reactions. The influence of oxygen partial pressure during crystallization was also studied. Dielectric properties were sensitive to pO2, with optimal properties occurring in a narrow pO2 window centered about 10−3 Torr. The trends with oxygen pressure were mirrored by changes in phase assemblage. Electrical transport across the dielectric layers was not strongly dependent upon doping level. This insensitivity was attributed to a thin interfacial layer present in all samples. Interface analysis using equivalent circuit analogues showed the nature of the interface to be highly resistive (insulating), rather than semiconducting or conducting.

The dependence of boron crystallization upon melt cooling has been investigated, as well as boron formation as a result of the chemical reaction of boron oxide with magnesium at a pressure of 7.7 GPa. Crystallization from the melt and the chemical reaction produce a rhombohedral β-boron phase, which is evidence of this phase stability at all temperatures up to the melting curve within the pressure range up to7.7 GPa. The melting temperature Tm at 7.7 GPa is 2480 ± 50 K, which points to a slight positive slope of the melting curve equal to approximately 10 K/GPa. Well-shaped single crystals of boron are formed as a result of the chemical reaction and the subsequent cooling from the melt at a rate of approximately 1 K/s, indicating low viscosity of the liquid phase.

The liquidus projection of the ternary Sn–Ag–Ni system at the Sn-rich side was determined experimentally. No ternary compound was found, and the ζ–Ag4Sn, Ag3Sn, and Sn existed as the primary solidification phases only in very small compositional portions of the ternary Sn–Ag–Ni system. In more than half of the compositional regime of the ternary system, the Ni3Sn2 phase was the primary solidification phase. The differential thermal analysis technique was used to determine the reaction temperatures and solidification sequences of various Sn-rich Sn–Ag–Ni alloys. Three invariant reactions were found: L = Sn + Ni3Sn4 + Ag3Sn, L + ζ–Ag4Sn = Ni3Sn4 + Ag3Sn and L + Ni3Sn2 = ζ–Ag4Sn + Ni3Sn4. Their reaction temperatures have been determined to be 219, 488, and 516.5 °C, respectively.

Aluminum nitride films were deposited by varying the voltages of argon ion beams from 400 to 1200 V in dual ion beam sputtering. The crystal structure, microstructure, and elemental distributions of the aluminum nitride films were analyzed by x-ray diffraction, field emission scanning electron microscopy, and secondary ion mass spectroscopy, respectively. The aluminum nitride films exhibited the 〈002〉 preferred orientation at an optimal ion beam voltage of 800 V. The orientation changed to a mixture of {100} and {002} planes above 800 V, accounting for radiation damage. The thickness of the film increases with increasing ion beam voltage, reaching a steady state value of 210 nm at an ion beam voltage of 1200 V. Under optimal condition (800 V), the c-axis orientation of the aluminum nitride 〈002〉 film was obtained with a dense and high-quality crystal structure.

By variation of reaction temperature and time during the hydrothermal synthesis process, TiO2 nanoparticles in anatase, rutile, and mixture of rutile-anatase phases are formed without adding any mineralizer. Differential thermal analysis studies indicate the rutile phase crystallization at a comparatively lower temperature and a low weight loss. The material synthesized by hydrothermal reaction required no post-calcination for the crystallization. Transmission electron microscopy, selected-area diffraction, Brunauer–Emmett–Teller, and x-ray diffreaction studies confirmed the compositions to be anatase and rutile with the particle size ranging from 5 to 25 nm with surface area as high as 260 m2/g for the anatase and 65 m2/g for rutile. The prepared nanoparticles exhibited a blue shift of the absorption edge in the ultraviolet-visible spectrum greater than 10 nm. The particles with average size around 5 nm showed two band edges in the absorption spectra attributed to two different particle sizes. Simple photocatalytic reactions were tried to demonstrate the photochemical activity of the synthesized material. The synthesized nanoparticles exhibited an ultraviolet radiation simultaneous photoreduction of Cr(VI) to Cr(III) and oxidation of formic acid into carbon dioxide and water.

This article reports degradation experiments on organic thin film transistors using the small organic molecule pentacene as the semiconducting material. Starting with degradation inert p-type silicon wafers as the substrate and SiO2 as the gate dielectric, we show the influence of temperature and exposure to ambient air on the charge carrier field-effect mobility, on-off-ratio, and threshold-voltage. The devices were found to have unambiguously degraded over 3 orders of magnitude in maximum on-current and charge carrier field-effect mobility, but they still operated after a period of 9 months in ambient air conditions. A thermal treatment was carried out in vacuum conditions and revealed a degradation of the charge carrier field-effect mobility, maximum on-current, and threshold voltage.

A microwave-assisted solvothermal method was used for the synthesis of selenium nanorods. The obtained selenium nanorods have axis ratios higher than 100 with their diameters in the range of 30–150 nm. This method is quite simple, rapid, adjustable, and general. Besides the effects of the experimental parameters on the synthesis of the selenium nanorods, the generality of this method has also been investigated, by which other one-dimensional nanostructures, metal lead and semiconductor cadmium sulfide nanorods, were also successfully synthesized.

Nickel films of 1.5–10-μm thickness, produced by dc magnetron sputtering and with disperse grain size distributions peaking in the 30–60-nm range, were subject to in situ tensile straining in a transmission electron microscope. The deformation was stopped frequently, while keeping the load applied, for transmission electron microscopy observation of the internal structure. Contrast changes occurred in many of the grains between strain increments. Ample evidence was seen of dislocation activity, which appears to be the major mechanism for deformation of the samples. Dislocations were seen in grains as small as 20 nm. Parallel arrays of roughly equally spaced dislocations were observed, spaced about 5–10-nm apart. Intergranular nanovoids were found to form and grow with accompanying strain relief in neighboring grains. The results of the current study are generally consistent with previous in situ investigations and contribute to the understanding of deformation mechanisms in free-standing thin films, which may differ somewhat from those in bulk nanocrystalline materials or in films attached to a substrate.

The influence of the variation in (V2O5/ P2O5) ratio on the local structure of iron in V2O5–BaO–Fe2O3–P2O5 glass system was investigated. Infrared analysis and Mössbauer spectroscopy were used for this propose. Infrared spectroscopic analysis showed that vanadium cations act mainly as network former (NWF) while iron ions occupy both NWF and network modifier (NWM) positions. On the other hand, Mössbauer spectra indicated that, at the lowest V2O5 content, about 29% of iron ions take their positions in the glass matrix as NWF and about 71% of iron ions enter the matrix as network modifier NWM. At the highest value of V2O5 content the iron ions that enter the glass as NWF decrease to about 15%, and the iron ions which enter the glass as NWM increase to about 85%. The density and molar volume measurements also indicate the changes in the structure of these glasses.

The Young's modulus of WS2 nanotubes is an important property for various applications. Measurements of the mechanical properties of individual nanotubes are challenged by their small size. In the current work, atomic force microscopy was used to determine the Young's modulus of an individual multiwall WS2 nanotube, which was mounted on a silicon cantilever. The buckling force was measured by pushing the nanotube against a mica surface. The average Young's modulus of an individual WS2 nanotube, which was calculated by using Euler's equation, was found to be 171 GPa. First-principle calculations of the Young's modulus of MoS2 single-wall nanotubes using density-functional–based tight-binding method resulted in a value (230 GPa) that is close to that of the bulk material. Furthermore, the diameter dependence of the Young's modulus in both zigzag and armchair configuration was studied and was found to approach the bulk value for nanotubes with few-nanometer diameters. Similar behavior is expected for WS2 nanotubes. The mechanical behavior of the WS2 nanotubes as atomic force microscope imaging tips gave further support for the measured Young's modulus.

Finite element simulations of conical indentations in two-phase elastic–plastic materials were used to investigate the influence of the shape and the aspect ratio of particles embedded in a matrix material on the deformation behavior and hardness during depth-sensing indentation. Starting with single-phase materials, pile-up behavior and its influence on the contact area was studied. Particle–matrix systems were simulated for elastic–perfectly plastic particles embedded in a matrix, with a yield-strength ratio of 2 or 0.5, respectively. The simulations were motivated by indentation experiments in precipitation hardened nickel-base superalloy with a nanoindenting atomic force microscope. In the studied alloys, the matrix formed channels with a thickness of about 100 nm around the precipitates with diameters of about 500 nm. The simulations explained an experimentally observed transition from particle to matrix deformation behavior during indentation. Depth limits in hardness testing in particle–matrix systems were evaluated. Depending on the aspect ratio, soft and hard particles were tested reliably up to a normalized contact radius of about 70% particle diameter.

The two immiscible liquid phases in equilibrium with a single liquid phase have been observed during the phase diagram study of an organic analog of a metal–nonmetal system involving pentachloropyridine (PCP)–succinonitrile (SCN). The phase equilibrium shows the formation of a monotectic and a eutectic, with large miscibility gap in the system, containing 0.0456 and 0.9658 mole fractions of SCN, respectively, and the consolute temperature being 99.0 °C above the monotectic horizontal line. The heat of mixing, entropy of fusion, roughness parameter, interfacial energy, and excess thermodynamic functions were calculated based on enthalpy of fusion data determined via the differential scanning calorimetry method. The effects of solid–liquid interfacial energy on morphology of monotectic structure as well as the variation of interfacial energies with temperature have been discussed. The microstructures of monotectic and eutectic show peculiar characteristic features. The material properties of PCP and PCP doped with SCN crystals, grown by the Bridgman–Stockbarger method, have been studied via studying second harmonic generation efficiency, transparency range, and mechanical hardness.

The title compositions were prepared by the gel-combustion process using glycine as the fuel and the corresponding metal nitrates as oxidants. The powders after calcination at 600 °C were characterized by x-ray diffraction for phase identification. The lattice parameters were refined by least squares method for each of the title compounds. Sr0.09Ce0.91O1.91 could be prepared in situ, that is, without any further external heating at higher temperatures, whereas phase pure SrCeO3 and Sr2CeO4 could be prepared only after calcination at 950 °C for 3 h. Sr0.09Ce0.91O1.91 was prepared using three different oxidant-to-fuel ratios: the fuel-deficient ratio, the propellant chemistry (stoichiometric) ratio, and the fuel-excess ratio. The crystallite size as calculated by x-ray line broadening was found to be 13 nm, 20 nm, and 42 nm for the products from fuel-deficient, propellant, and fuel-excess ratios, respectively. It was found that the extreme fuel-deficient ratio of 1:0.5 failed to give phase pure Sr0.09Ce0.91O1.91. The transmission electron microscopy studies showed that majority of the particles were in the range 80–100 nm and 200–250 nm for SrCeO3 and Sr2CeO4, respectively. The compositional characterization was done by energy dispersive x-ray. A careful control of the oxidant-to-fuel ratio was found to be necessary to get the desired products, due to their different thermodynamic stabilities. Thus, the versatility of combustion process in synthesizing the products with different thermodynamic stabilities has been shown, which was hitherto unexplored.

Comprehensive results are presented on the influence of interfaces on electronic structure and giant magnetoresistance (GMR). Two structures were calculated for Co5/Cu3/Co5 and Co3/Cu/Co/Cu3/Co/Cu/Co3, where numbers stand for monolayer numbers of atoms, by employing the discrete variational method in the framework of the local spin density approximation. It has been found that the electron spin-dependent scattering is very strong at the interfaces compared to the interiors of the ferromagnetic layers, independent of the moment alignment configuration. The calculation results of total energy for various magnetization configuration revealed that antiferromagnetic exchange coupling was present between any of the ferromagnetic layers separated by Cu layers at zero field in the Co3/Cu/Co/Cu3/Co/Cu/Co3. The evaluated GMR ratio for the Co3/Cu/Co/Cu3/Co/Cu/Co3 (about 35.1%) was much larger than that of the Co5/Cu3/Co5 (about 21.0%), indicating large GMR effect could be expected with more interfaces when the thicknesses were the same. The result also indicated that the negative polarization of 4s electrons could reduce the GMR effect.