Vapor-Phase Halogenation of Hydrogen-Terminated Silicon(100) Using N -Halogen-succinimides
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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
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Locating subsurface gravel with thermal imagery
A method was discussed for using 6 band thermal imagery to locate subsurface gravel deposits in vegetated areas. Geologic history is reviewed to select potential areas of study. An overflight was made using a thermal scanner. The data were processed with a computerized system to delineate areas showing a quartz signature radiated by a gravel deposit. The method was developed during a search for gravel on National Forest land in Louisiana. Processed data from thermal imagery was compared with known gravel deposits and exploratory drill hole logs. A high correlation was noted for a wide range of deposits, from commercial pits to trace deposits only a foot thick. Overburden at these sites varied from zero to sixty feet, near the maximum annual penetration by the thermal wave. It was concluded that the method can be used to locate buried gravel deposits and that more time and effort are needed to verify the usefulness for developing gravel pits adjacent to proposed construction sites.
Scholen, Douglas E.↗
Effective Selective Area Doping for GaN Vertical Power Transistors Enabled by Innovative Materials Engineering
GaN vertical power transistors have emerged as promising candidates for future high efficiency high power electronic applications, with the potential to outperform conventional GaN lateral power devices in terms of power, breakdown, and avalanche characteristics. However, the development of current GaN vertical power transistors is seriously hindered by the poor materials performance of selective area doped p-n junctions. A mechanistic understanding of these fundamental materials issues is essential in order to achieve high performance selective area doped p-n junctions and consequently to advance the GaN vertical power transistor technology. To address this challenge, we carried out a comprehensive research program that advance fundamental knowledge in the selective area doping for GaN materials, and which will lead to the development of high performance GaN vertical power transistors. First, we developed innovative fabrication processes, including novel surface etching, surface passivation, and metalorganic chemical vapor deposition (MOCVD) growth, which provided enhanced opportunities for solving the unique challenges of selective area doping in GaN materials. Second, we performed a fundamental materials study using powerful characterization methods including transmission electron microscopy (TEM), ultraviolet (UV-), x-ray and angle-resolved photoelectron spectroscopy (UPS/XPS/ARPES), electron holography, and cathodoluminescence (CL); Third, we investigated several related issues, including Mg incorporation, polarization effects in carrier transport, and non-ideal material effects, which have rarely been explored so far. At the end of this project, we successfully demonstrated (1) fundamental understanding of selective area etching, regrowth, and doping of GaN, and associated knowledge on defects, interface, and breakdown properties. (2) Effective etch and regrowth processing recipes to achieve etch/regrowth GaN p-n diodes with very low leakage of 3.5 nA at 600 V, which meets the ARPA-E target. (2) High performance vertical GaN p-n didoes and vertical junction termination extension (JTE) devices with breakdown voltage of ~ 2 kV, and breakdown electric field of ~ 3.5 MV/cm, which are close to the performance limit of GaN. The successful outcome has resulted in new fundamental understandings in the selective area doping and regrowth process for GaN, which will lead to groundbreaking GaN vertical transistors for high performance next generation power electronics.
24 POWER TRANSMISSION AND DISTRIBUTION↗
Vacuum Plasma Spraying Of Copper Onto Titanium
Vacuum plasma spraying successful in depositing tenacious copper coat on flanges and other selected areas of titanium valve housing. Oxidation and concomitant brittleness eliminated.
Power, Chris↗
Surface Dynamics of Selective Hydration of Rutile TiO 2 : A Kinetic Monte Carlo Approach
The utility of atomic layer deposition (ALD) continues to expand beyond conformal thin-film fabrication to include area- or site-selective ALD. We previously identified a strategy for site-selective ALD (SS-ALD) via the evaluation of thermodynamically preferred hydration of rutile TiO 2 surfaces, as deduced from electronic structure calculations. Here, we report a novel kinetic Monte Carlo (KMC) model that allows for the investigation of surface dynamics and kinetics that improves our understanding of and intuition for the selective hydration strategy. Here we demonstrate the validity of the strategy with respect to step-edge defects for the lowest energy (110) facet as well as report results for the other common facets which agree with experimental STM observations. The results here indicate that the selective hydration strategy is feasible both thermodynamically (evaluated in our previous publication) and kinetically (from the KMC model). Because diffusion has a slower rate than others, we find that any proximity effects between terrace and defect sites are unlikely to affect the selective hydration strategy for rutile TiO 2 . The KMC model further provides relevant timescales for achieving selectivity experimentally and establishes the kinetic viability of the selective hydration approach to SS-ALD.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Mitigation of Aerosol Impacts of Ash Deposition and Emissions from Coal Combustion (Final Technical Report)
This project was selected under FOA-0001989 Area of Interest (AOI) 2 – Power Plant Component Improvement. The objective of this AOI was to test and validate technologies and methodologies that can improve the efficiency, reliability, and/or flexibility of individual power plant components in existing plants. The aerosol mitigation technology comprises injection of sorbent into the boiler through injection lances using a positive-pressure blower. The injected sorbent interacts with flame-vaporized aerosolforming components produced during combustion reducing the abundance of sub-micrometer (< 1 micron) particles and fireside ash deposits in the boiler. The primary objective of this project was to validate a sorbent-based technology for mitigating fireside heat transfer surface fouling-related challenges in a full-scale coal-fired power generation facility, thereby, improving plant performance and reliability.
01 COAL, LIGNITE, AND PEAT↗
Mesoporous silica-encapsulated gold core–shell nanoparticles for active solvent-free benzyl alcohol oxidation
Silica-encapsulated gold core@shell nanoparticles (Au@SiO2 CSNPs) were synthesized via a bottom-up procedure and used to catalyze the selective oxidation of benzyl alcohol. The pore size, morphology, crystallinity and composition of Au@SiO2 was evaluated using non-local density functional theory, transmission electron microscopy, high-energy x-ray diffraction and inductively coupled plasma-mass spectroscopy, respectively. The nanoparticles exhibit a mesoporous shell with an average thickness of 25.5 Å which can enhance selectivity via preferential transport of the desired product (i.e., benzaldehyde) relative to larger, undesired products (i.e, benzoic acid/benzyl benzoate). GC-FID analysis revealed the addition of potassium carbonate to the solvent-free oxidation of benzyl alcohol increased conversion from 17.3 to 60.4% while decreasing selectivity from 98.7 to 75.0%. Under equivalent conditions, a bare gold nanoparticle control catalyst deposited on a silica support with a similar gold surface area took 6 times as long to reach the same conversion, achieving only 49.4% selectivity. These results suggest that the pore size distribution within the inert silica shell of Au@SiO2 CSNPs inhibits the formation of undesired products to facilitate the selective oxidation of benzaldehyde despite a basic environment, which reduces selectivity under typical conditions. The CSNPs demonstrated a much lower activation energy than the Au-SiO2 control catalyst, 37 ± 1.9 kJ/mol and 72 ± 7.1 kJ/mol, respectively. Thiele modulus analysis indicates the CSNP pore structure does not create a mass transport limitation due to the nano-scale path of diffusion through the pore structure to the active surface. The lower activation energy and mesopore distribution together suggest the Au@SiO2 catalyst demonstrates higher activity through beneficial in-pore orientation, both reducing competitive adsorption and promoting a single, lower activation energy mechanistic pathway.
benzyl alcohol oxidation, catalysis, confinement↗
Self-Aligned, Selective Area Poly-Si/SiO2 Passivated Contacts for Enhanced Photocurrent in Front/Back Solar Cells
Poly-Si/SiO 2 passivated contact front/back solar cells suffer low Jsc due to parasitic absorption in the front poly-Si layer. We demonstrate a self-aligned, selective area front contact dry-etch technique that retains the as-deposited poly-Si beneath the metal grid lines but thins it elsewhere. Jsc improves by 0.7 mA/cm 2 over our standard 40 nm thick poly-Si. Greater improvements are expected with thicker poly-Si needed for fired metal contacts. Surface passivation is slightly diminished with poly-Si thinning but can be partially restored with rehydrogenation.
14 SOLAR ENERGY↗
Improved Method of Manufacturing SiC Devices
The phrase, "common-layered architecture for semiconductor silicon carbide" ("CLASSiC") denotes a method of batch fabrication of microelectromechanical and semiconductor devices from bulk silicon carbide. CLASSiC is the latest in a series of related methods developed in recent years in continuing efforts to standardize SiC-fabrication processes. CLASSiC encompasses both institutional and technological innovations that can be exploited separately or in combination to make the manufacture of SiC devices more economical. Examples of such devices are piezoresistive pressure sensors, strain gauges, vibration sensors, and turbulence-intensity sensors for use in harsh environments (e.g., high-temperature, high-pressure, corrosive atmospheres). The institutional innovation is to manufacture devices for different customers (individuals, companies, and/or other entities) simultaneously in the same batch. This innovation is based on utilization of the capability for fabrication, on the same substrate, of multiple SiC devices having different functionalities (see figure). Multiple customers can purchase shares of the area on the same substrate, each customer s share being apportioned according to the customer s production-volume requirement. This makes it possible for multiple customers to share costs in a common foundry, so that the capital equipment cost per customer in the inherently low-volume SiC-product market can be reduced significantly. One of the technological innovations is a five-mask process that is based on an established set of process design rules. The rules provide for standardization of the fabrication process, yet are flexible enough to enable multiple customers to lay out masks for their portions of the SiC substrate to provide for simultaneous batch fabrication of their various devices. In a related prior method, denoted multi-user fabrication in silicon carbide (MUSiC), the fabrication process is based largely on surface micromachining of poly SiC. However, in MUSiC one cannot exploit the superior sensing, thermomechanical, and electrical properties of single-crystal 6H-SiC or 4H-SiC. As a complement to MUSiC, the CLASSiC five-mask process can be utilized to fabricate multiple devices in bulk single-crystal SiC of any polytype. The five-mask process makes fabrication less complex because it eliminates the need for large-area deposition and removal of sacrificial material. Other innovations in CLASSiC pertain to selective etching of indium tin oxide and aluminum in connection with multilayer metallization. One major characteristic of bulk micromachined microelectromechanical devices is the presence of three-dimensional (3D) structures. Any 3D recesses that already exist at a given step in a fabrication process usually make it difficult to apply a planar coat of photoresist for metallization and other subsequent process steps. To overcome this difficulty, the CLASSiC process includes a reversal of part of the conventional flow: Metallization is performed before the recesses are etched.
Okojie, Robert S.↗
System and method for performing laser powder bed fusion using controlled, supplemental in situ surface heating to control microstructure and residual stresses in formed part
The present disclosure relates to an additive manufacturing system for forming a part using a powder material. In one embodiment the system makes use of a primary heat generating subsystem to generate a fusing beam for heating and fusing at least one of select portions of a powder layer, or an entire area of a powder layer, deposited on a build plate. The system also incorporates a beam steering subsystem for steering the fusing beam over the powder layer. A supplemental heating subsystem is used to generate a wide area beam to heat a portion of the powder layer either prior to fusing, along with the fusing operation, or subsequent to fusing of the powder with the fusing beam. The wide area beam has an intensity which is insufficient to fuse the powder, and alters a microstructure of the powder layer as the powder layer is at least one of fused or as it cools, to thus relieve stress in the part.
Smith, William↗
Electrochemistry-induced deposition for controlled formation of metal–organic framework films on insulator and conductor substrates
A number of technological applications of metal–organic frameworks (MOFs) require the formation of their thin films on insulator and/or conductor substrates at selected areas with desired thicknesses. However, fabrication of such MOF films often requires multi-step processes and/or sophisticated instruments. Herein, we discuss electrochemistry-induced MOF deposition, which permits the direct formation of a thin MOF film with controlled thickness at a desired area on various substrates. So far, we have reported the applicability of this deposition method for the formation of zeolitic imidazolate framework-8 (ZIF-8) films. In this method, a ZIF-8 film is formed on an insulator or a conductor substrate upon applying a cathodic potential to a working electrode that is placed above the substrate. Importantly, the film is formed just below the cathodic working electrode, indicating that the position and lateral dimensions (on the mm- to μm-scale) of the film can be controlled by those of the working electrode. In addition, film thickness is controllable in the range of tens to hundreds of nanometers by adjusting potential application conditions at the cathodic working electrode. These results show that the electrochemistry-induced deposition method will provide a simple means for the fabrication of a patterned MOF film on various substrates without additional lithographic processes.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Regional aeolian dynamics and sand mixing in the Gran Desierto - Evidence from Landsat Thematic Mapper images
Mesoscale mapping of spatial variations in sand composition of the Gran Desierto (Sonora, Mexico) was carried out on multispectral Landsat TM images of this region, making it possible to examine the dynamic development of sand sheets and dunes. Compositions determined from remote imagery were found to agree well with samples from selected areas. The sand populations delineated were used to describe the sediment source areas, transport paths, and deposition sites. The image analysis revealed important compositional variations aver large areas that were not readily apparent in the field data.
Blount, Grady↗
Method for mask-free OLED deposition and manufacture
A method for making an OLED lighting panel is disclosed. A patterned inorganic insulating layer is used to enclose an area over a first electrode layer leaving portions of the first electrode layer and substrate adjacent to the outside of the enclosure exposed. After uniform deposition of the organic layer(s), the organic layer(s) are selectively removed over the inorganic insulating layer and an adjacent portion of the substrate to form a sealing region. After uniform deposition of the second electrode, the enclosed area is encapsulated and any overlying layers over the first and second electrodes outside the enclosed area are removed resulting in an OLED within the enclosed area with electrode contact pads outside the enclosed area. The OLED can be manufactured at low cost with no or limited use of shadow masking and is suitable for roll-to-roll processes.
Hamer, John↗
On-Demand Selection of the Latent Domain Orientation in Spray-Deposited Block Copolymer Thin Films
With their ability to self-assemble spontaneously into well-defined nanoscale morphologies, block copolymer (BCP) thin films are a versatile platform to fabricate functional nanomaterials. An important challenge to wider deployment of BCPs in nanofabrication is combining precise control over the nanoscale domain orientation in BCP assemblies with scalable deposition techniques that are applicable to large-area, curved, and flexible substrates. Here, in this study, we show that spray-deposited smooth films of a nominally disordered BCP exhibit latent orientations, which can be prescriptively selected by controlling solvent evaporation during spray casting. Subsequent solvent vapor annealing triggers assembly toward highly ordered cylindrical morphologies along the pathway determined by solvent evaporation in the prior spray deposition stage. Faster evaporation promotes assembly of vertically oriented cylinders spanning the entire film thickness (100–300 nm). In comparison, slow solvent evaporation permits intermicellar aggregation and incipient cylinder formation in solution, which induces horizontal cylinder assembly upon annealing. The evaporatively controlled latent orientation mechanism presented herein elucidates how nonequilibrium phenomena during casting govern successive self-assembly pathways and facilitates a versatile method to dictate the domain orientation of BCP thin films on demand on flexible and highly curved substrates or in distinct pattern areas on the same substrate.
36 MATERIALS SCIENCE↗
Selective Hydroxylation of In 2 O 3 as A Route to Site-Selective Atomic Layer Deposition
We report that several atomic layer deposition (ALD) processes are now known that leverage the distinct surface chemistry of two disparate substrates (e.g., metal vs oxide) to realize markedly different ALD nucleation rates in an approach referred to as area-selective ALD. In contrast, few ALD processes have been identified that allow selective reaction at distinct surface sites of a single material surface, in a process that might be called site-selective ALD (SS-ALD). We describe one potential strategy to discriminate among several distinct surface sites on bixbyite In 2 O 3 to achieve site selectivity. Using density functional theory, we predict the discriminant hydration and hydroxylation of In 2 O 3 terrace and step-edge sites that depend strongly on the substrate temperature at low water coverage. Infrared measurement of surface hydroxyls on In 2 O 3 nanoparticles supports the predicted temperature dependence. The in situ examination of MgO ALD nucleation also shows results consistent with the predicted temperature dependence of In 2 O 3 hydroxylation. Together, these findings suggest that a selective hydroxylation approach may be a viable route to SS-ALD on In 2 O 3 .
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Strategy for selecting Mars Pathfinder landing sites
A strategy for Pathfinder site selection must be developed that is fundamentally different from most previous considerations. At least two approaches can be identified. In one approach, the objective is to select a site representing a key geologic unit on Mars, i.e., a unit that is widespread, easily recognized, and used frequently as a datum in various investigations. The second approach is to select a site that potentially affords access to a wide variety of rock types. Because rover range is limited, rocks from a variety of sources must be assembled in a small area for sampling. Regardless of the approach taken in site selection, the Pathfinder site should include eolian deposits and provisions should be made to obtain measurements on soils. A recommended approach for selecting the Mars Pathfinder landing site is to identify a deltaic deposit, composed of sediments derived from sources of various ages and geologic units that shows evidence of eolian activity. The site should be located as close as possible to the part of the outwash where rapid deposition occurred because the likelihood of 'sorting' by size and composition increases with distance, decreasing the probability of heterogeneity. In addition, it is recommended that field operation tests be conducted to gain experience and insight into conducting science with Pathfinder.
Greeley, Ronald↗
A study of morphology, provenance, and movement of desert sand seas in Africa, Asia, and Australia
The author has identified the following significant results. The assembling of photomosaics from color prints of ERTS images has made possible the recognition and description of san patterns, and these are to be the basis of a worldwide classification of sand bodies. Progress has been as rapid as the acquisition of the bulk composite images will permit and for some areas the mosaics are now nearly complete. A second step, which consists of the accumulation and analysis of regional wind data, to be plotted as overlays for the dune patterns, is now underway and should soon give tangible results. Other aspects of the project include the gathering of ground truth in the form of air photographs, needed to interpret geomorphic forms and the sampling of sand deposits for analyzing the texture and composition of sand bodies. A start has been made on these studies in several selected areas.
Mckee, E. D.↗
The structural changes of water ice I during warmup
The polymorph transitions of vapor deposited water ice I during warmup from 15 K to 210 K was mapped by means of selected area electron diffraction. The polymorph transitions account for many phenomena observed in laboratory analog studies of cometary outgassing and radial diffusion in UV photolyzed interstellar ices.
Jenniskens, Peter↗