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In this work, low-pressure synthesis of carbon spheres from resorcinol and formaldehyde using an autoclave is presented. The influence of reaction time and process temperature as well as the effect of potassium oxalate, an activator, on the morphology and CO2 adsorption properties was studied. The properties of materials produced at pressureless (atmospheric) conditions were compared with those synthesized under higher pressures. The results of this work show that enhanced pressure treatment is not necessary to produce high-quality carbon spheres, and the morphology and porosity of the spheres produced without an activation step at pressureless conditions are not significantly different from those obtained at higher pressures. In addition, CO2 uptake was not affected by elevated pressure synthesis. It was also demonstrated that addition of the activator (potassium oxalate) had much more effect on key properties than the applied pressure treatment. The use of potassium oxalate as an activator caused non-uniform size distribution of spherical particles. Simultaneously higher values of surface area and total pore volumes were reached. A pressure treatment of the carbon materials in the autoclave significantly enhanced the CO2 uptake at 25 &deg, C, but had no effect on it at 0 &deg, C.

In this work, production and characterization of carbon spheres from resorcinol and formaldehyde, using a microwave assisted solvothermal reactor, is presented. The influence of different experimental conditions, e.g., reaction time, pressure, and power, on the structure of the obtained materials, and carbon dioxide adsorption properties, was studied. Using the method described in this work, it is possible to significantly reduce the reaction time, to as low as 10 min, compared with widely described processes carried out in autoclaves, requiring several hours. Simultaneously, it was discovered that the application of higher reactor pressures, over 3 MPa, resulted in the destruction of spherical shape and the formation of graphitic layers. The importance of micropores below 0.4 nm, for adsorption of carbon dioxide, was also shown in this work. Microporous carbon spheres with efficient CO2 adsorption properties (nearly 7 mmol/g at 1 bar and 0 °C) were synthesized using this process.

An ultra-low percolation threshold electrically conductive polymer nanocomposite incorporating graphene into a polyhedral oligomeric silsesquioxane polycaprolactone (POSS-PCL/graphene) is described in this paper. Multilayer graphene flakes were homogeneously dispersed into POSS-PCL at 0.08, 0.4, 0.8, 1.6, and 4.0 wt% concentrations. The impedance spectroscopy of 0.08 wt% and higher concentration of graphene in POSS-PCL represented major improvement in conductivity over pristine POSS-PCL. The percolation threshold occurred at 0.08 wt% graphene concentration, and at 4.0 wt% the electrical conductivity exceeded 10−4 Scm−1. Furthermore, the chemical, morphological, and mechanical of the POSS-PCL/graphene with various graphene concentrations were investigated. Finally, neural cells cultured on all POSS-PCL/graphene constructs indicated higher metabolic activity and cell proliferation in comparison with pristine POSS-PCL. Herein, we demonstrate a method of developing a neural-compatible and electrically conductive polymer nanocomposite that could potentially function as a neural tissue engineered platform technology for neurological and neurosurgical applications.

Aluminum nitride (AlN) films with controlled oxygen content were deposited on silicon substrates, and optical properties studied with dependency on film morphology. Combinations of argon (Ar) and nitrogen (N2) gases were used in RF magnetron sputtering of an AlN target. The resulting refractive index ranging from 1.6 to 2.0 at 400 nm was tuned by controlling the sputter gas flow rate ratio of Ar and N2. The resulting refractive index is associated with density and aluminum nitride content of the thin films. Distributed Bragg Reflectors (DBRs) optimized for ultraviolet-A reflectivity were fabricated with pairs of alternating AlN thin films using an explicit combination of low-n and high-n to further investigate the thin film optical properties. The effect of structural transformation in the DBR stack on the progress of optical properties was studied. The DBRs exhibit a negligible extinction coefficient, utilizing precise control of oxygen incorporation with one sputtering target.

Vertically aligned graphene was grown by plasma-enhanced chemical vapor deposition using methane feedstock. Optical emission spectroscopy (OES) was used to monitor the plasma species, and Raman spectroscopy was used for characterizing the properties of as-grown vertically aligned graphene. OES-derived information on plasma species, such as C, C2, CH, and H, are correlated with the properties of the vertically aligned graphene. Graphene grown at 250 W and 15 sccm exhibited the lowest amount of defects. Although OES peak intensities occurred at the highest power and lowest flow conditions, the OES peak ratios of plasma species had a greater dependence on flow rate and exhibited a saddle point in the atomic C/H ratio corresponding to optimal growth involving the lowest amount of overall defects. Plasma diagnostics provides a valuable approach to optimize growth characteristics and material properties.

Native oxide grown on copper has been a nuisance in electrical devices due to extra electrical resistance added to copper electrodes. However, copper oxide, known to have two primary stable phases, cuprous oxide (Cu2O) and cupric oxide (CuO), is a material worth investigating for electronic applications. These two phases exhibiting distinctive electrical characteristics, would make copper oxide a prospective material for resistive switches. Cu2O and CuO often form concurrently within the native oxide. Because of their similar refractive index and extinction coefficient, optically differentiating these two phases is a challenge, yet it is critical for designing devices. In this study, thin copper films were deposited using electron-beam evaporation and sputtering. A native oxide was grown on the prepared copper films over 250 days in air and periodically evaluated with reflectometry-ellipsometry. X-ray photoelectron spectroscopy was also performed on the samples aged for 7 months to obtain their chemical characteristics. A comprehensive analysis on the progressive formation of native oxide on copper is discussed.

The oxidation of copper is a complicated process. Copper oxide develops two stable phases at room temperature and standard pressure (RTSP): cuprous oxide (Cu2O) and cupric oxide (CuO). Both phases have different optical and electrical characteristics that make them interesting for applications such as solar cells or resistive switching devices. For a given application, it is necessary to selectively control oxide thickness and cupric/cuprous oxide phase volume fraction. The thickness and composition of a copper oxide film growing on the surface of copper widely depend on the characteristics of as-deposited copper. In this Research Article, two samples, copper films prepared by two different deposition techniques, electron-beam evaporation and sputtering, were studied. As the core part of the study, the formation of the oxidized copper was analyzed routinely over a period of 253 days using spectroscopic polarized reflectometry-spectroscopic ellipsometry (RE). An effective medium approximation (EMA) model was used to fit the RE data. The RE measurements were complemented and validated by using X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and X-ray diffraction (XRD). Our results show that the two samples oxidized under identical laboratory ambient conditions (RTSP, 87% average relative humidity) developed unique oxide films following an inverse-logarithmic growth rate with thickness and composition different from each other over time. Discussion is focused on the ability of RE to simultaneously extract thickness (i.e., growth rate) and composition of copper oxide films and on plausible physical mechanisms responsible for unique oxidation habits observed in the two copper samples. It appears that extended surface characteristics (i.e., surface roughness and grain boundaries) and preferential crystalline orientation of as-deposited polycrystalline copper films control the growth kinetics of the copper oxide film. Analysis based on a noncontact and nondestructive measurement, such as RE, to extract key material parameters is beneficial for conveniently understanding the oxidation process that would ultimately enable copper oxide-based devices at manufacturing scales.

Morphologies of silicon nanowires grown by plasma-assisted metalorganic chemical vapor deposition were studied in the presence of various dopant precursors. The varied precursors affected the axial and radial growth rates over orders of magnitude where triethylborane showed the strongest enhancements for both axial and radial growth, and triethylarsenic and triethylantimony retarded axial growth. Native oxide thickness is also shown to depend strongly on doping condition resulting in increased oxide thicknesses for increased carrier concentration, using shifts in the measured binding energy of the silicon 2p3/2 state as a proxy for carrier concentration.

Preparing an effective workforce in high technology is the goal of both academic and industry training, and has been the engine that drives innovation and product development in the United States for over a century. During the last 50 years, technician training has comprised a combination of two-year academic programs, internships and apprentice training, and extensive On-the-Job Training (OJT). Recently, and especially in Silicon Valley, technicians have four-year college degrees, as well as relevant hands-on training. Characterization in general, and microscopy in particular, is an essential tool in process development, manufacturing and QA/QC, and failure analysis. Training for a broad range of skills and practice is challenging, especially for community colleges. Workforce studies (SRI/Boeing) suggest that even four year colleges often do not provide the relevant training and experience in laboratory skills, especially design of experiments and analysis of data. Companies in high-tech further report difficulty in finding skilled labor, especially with industry specific experience. Foothill College, in partnership with UCSC, SJSU, and NASA-Ames, has developed a microscopy training program embedded in a research laboratory, itself a partnership between university and government, providing hands-on experience in advanced instrumentation, experimental design and problem solving, with real-world context from small business innovators, in an environment called ‘the collaboratory’. The program builds on AFM-SEM training at Foothill, and provides affordable training in FE-SEM and TEM through a cost recovery model. In addition to instrument and engineering training, the collaboratory also supports academic and personal growth through a multiplayer social network of students, faculty, researchers, and innovators.

Semiconducting nanowires are promising materials for a variety of applications, many of which are in optoelectronics where their ability to use quantum confinement to tune transition energy levels and their ability to epitaxially grow on substrates with large lattice-mismatches enable unique opportunities. In addition, the large relative surface area of nanowire-based devices can be either a benefit as in, for example, sensor applications or challenges such as charge trapping, non-radiative recombination or Fermi-level pinning. In this study, indium phosphide nanowires grown by metal organic chemical vapor deposition were conformally coated with aluminum oxide by atomic layer deposition as a means of controlling the surface states within the indium phosphide region. Photoluminescence spectra from the coated nanowires show a strong blueshift and slight peak broadening as compared to uncoated nanowires despite their increased lateral dimension. This degree of blueshift is unlikely to have been caused by strain associated with the coating because of its relatively thin thickness (~10 nm), and the x-ray diffraction profiles collected from the coated nanowires do not indicate the presence of substantial lattice deformation. It is more likely to be a result of altered chemical state at the surface; the uncoated nanowires have oxygen bound to both indium and phosphorus near the surface as confirmed in our X-ray photoelectron spectroscopy studies. Subsequent aluminum oxide deposition alters surface atomic bonding thereby modifying the states electronic responsible for optical properties in the nanowires.

Chemistry and materials science students face a daunting taxonomy of terminology, molecular and crystalline structures, and chemical and physical properties to memorize, organize, and apply. “Emergence of properties at scale” is a foundational concept in nanoscience, yet nothing in nanotechnology curriculum explains how and where specific properties emerge. Through nanotechnology courses and a certificate program, Foothill College is developing a framework that captures emergent network archetype properties. A novel pedagogical approach applies the concept of patterns to nanostructured materials, as a classification means to understand how physical properties emerge from extended networks of atoms and molecules, and the physics of those extended structural networks. From such a foundational understanding, scientists, technicians and engineers will be better informed in “engineering the neighborhood of the atom,” to produce novel materials with unique properties, the working definition of nanotechnology.

An IR and XPS study of the low-pressure, radiofrequency, glow-discharge plasma copolymerization of ethylene (ET) and tetrafluoroethylene (TFE) is presented. The potential for creating Tefzel- or Teflon-like coatings on various polymeric substrates for use in advanced life support systems is examined.

The ESCA spectra and data obtained by Morra et al. (1989) on poly(tetrafluoroethylene) (PTFE) exposed to atomic oxygen plasma are closely reexamined. It is shown that the spikes observed in Morra et al. plots of O/C or F/C versus time of the exposure of PTFE to atomic oxygen plasma were not characteristic of PTFE per se but were instead a result of a contamination by hydrocarbon present in their PTFE samples. This was demonstrated experimentally by comparing data derived for a very clean PTFE sample exposed for 10, 20, and 30 min to oxygen plasma with data obtained on PTFE samples with very small amounts of hydrocarbon contamination.

The surfaces of polymers, metals, and other materials may be bonded in difficult geometries or used in environments where adhesion, printability, or biocompatibility must meet exacting standards. In such cases, the performance of materials is often related to a critical material property, such as surface topography (for example, smoothness, or roughness) or purity (for example, the absence of contaminants, leachable, or surface-segregated oligomers). Analysis of material properties and composition is useful in characterization of materials on selection and receipt, in analyzing failures and other problems, and in validating manufacturing processes. This chapter focuses on the role of modem analytical instrumentation used in electron spectroscopy, microscopy, and organic analysis of material surfaces and sub-surfaces. Many medical devices comprise a combination of complex materials that can be altered in undesirable ways by processing or interaction with other materials. By using a combination of microscopy and organic and surface analysis techniques, both materials and manufacturing processes can be optimized to ensure high yield and good performance.

Physical properties of semiconductor nanowires are tied intimately to their specific morphologies such as length and diameter. We studied the growth of silicon nanowires and found their lengths and diameters to vary over orders of magnitude in different doping environments. In all cases we examined, doping resulted in increased diameters. In addition, boron doping was found to accelerate volume growth rate while arsenic and antimony both appeared to slow it down. We further studied the formation of the native oxides that cover the nanowires. X-ray photoelectron spectroscopy indicated that properties of the native oxides are also dependent on doping environment and correlated to doping-dependent shifts in apparent binding energy of the Si 2p3/2 peak illustrating that the electronic contribution is the dominant mechanism for the oxide growth.

The ESCA (electron spectroscopy for chemical analysis) spectra of films of Tedlar, tetrafluoroethylene-hexafluoropropylene copolymer (in the form of a Teflon FEP coating on Kapton H, i.e., Kapton F), and polytetrafluoroethylene (Teflon or Teflon TFE), exposed to atomic oxygen O(3P) either in LEO on the STS-8 Space Shuttle or within or downstream from a radio-frequency oxygen plasma, were compared. The major difference in surface chemistry of Tedlar induced by the various exposures to O(3P) was a much larger uptake of oxygen when etched either in or out of the glow of an O2 plasma than when etched in LEO. In contrast, Kapton F exhibited very little surface oxidation during any of the three different exposures to O(3P), while Teflon was scarcely oxidized.

The ESCA (electron spectroscopy for chemical analysis) spectra of films of poly(vinylidene fluoride) (PVDF), tetrafluoroethylene-ethylene copolymer (TFE/ET) and polyethylene (PE) exposed to atomic oxygen (O(P-3)), in or out of the glow of a radio-frequency O2 plasma, were compared. ESCA spectra of PE films exposed to (O(P-3)) in low Earth orbit (LEO) on the STS-8 Space Shuttle were also examined. Apart from O(P-3)-induced surface recession (etching), the various polymer films exhibited surface oxidation, which proceeded towards equilibrium saturation oxygen levels. The maximum surface oxygen uptakes for in-glow or out-of-glow exposures were in the order: PE greater than TFE/ET greater than PVDF; for PE itself, the oxygen uptakes were in the order: in glow greater than out of glow greater than LEO. Given prior ESCA data on poly(vinyl fluoride) and polytetrafluoroethylene films exposed to O(P-3), the extent of surface oxidation is seen to decrease regularly with increase in fluorine substitution in a family of ethylene-type polymers. (Keywords: ESCA; poly(vinylidene fluoride); tetrafluoroethylene ethylene copolymer; polyethylene; atomic oxygen; radio-frequency oxygen plasma; low Earth orbit)