3,933 research outputs found
Selective Plasma Deposition of Fluorocarbon Films on SAMs
A dry plasma process has been demonstrated to be useful for the selective modification of self-assembled monolayers (SAMs) of alkanethiolates. These SAMs are used, during the fabrication of semiconductor electronic devices, as etch masks on gold layers that are destined to be patterned and incorporated into the devices. The selective modification involves the formation of fluorocarbon films that render the SAMs more effective in protecting the masked areas of the gold against etching by a potassium iodide (KI) solution. This modification can be utilized, not only in the fabrication of single electronic devices but also in the fabrication of integrated circuits, microelectromechanical systems, and circuit boards. In the steps that precede the dry plasma process, a silicon mold in the desired pattern is fabricated by standard photolithographic techniques. A stamp is then made by casting polydimethylsiloxane (commonly known as silicone rubber) in the mold. The stamp is coated with an alkanethiol solution, then the stamp is pressed on the gold layer of a device to be fabricated in order to deposit the alkanethiol to form an alkanethiolate SAM in the desired pattern (see figure). Next, the workpiece is exposed to a radio-frequency plasma generated from a mixture of CF4 and H2 gases. After this plasma treatment, the SAM is found to be modified, while the exposed areas of gold remain unchanged. This dry plasma process offers the potential for forming masks superior to those formed in a prior wet etching process. Among the advantages over the wet etching process are greater selectivity, fewer pin holes in the masks, and less nonuniformity of the masks. The fluorocarbon films formed in this way may also be useful as intermediate layers for subsequent fabrication steps and as dielectric layers to be incorporated into finished products
Lattice dynamics and vibrational spectra of the orthorhombic, tetragonal and cubic phases of methylammonium lead iodide
The hybrid halide perovskite CH3NH3PbI3 exhibits a complex structural
behaviour, with successive transitions between orthorhombic, tetragonal and
cubic polymorphs at ca. 165 K and 327 K. Herein we report first-principles
lattice dynamics (phonon spectrum) for each phase of CH3NH3PbI3. The
equilibrium structures compare well to solutions of temperature-dependent
powder neutron diffraction. By following the normal modes we calculate infrared
and Raman intensities of the vibrations, and compare them to the measurement of
a single crystal where the Raman laser is controlled to avoid degradation of
the sample. Despite a clear separation in energy between low frequency modes
associated with the inorganic PbI3 network and high-frequency modes of the
organic CH3NH3+ cation, significant coupling between them is found, which
emphasises the interplay between molecular orientation and the corner-sharing
octahedral networks in the structural transformations. Soft modes are found at
the boundary of the Brillouin zone of the cubic phase, consistent with
displacive instabilities and anharmonicity involving tilting of the PbI6
octahedra around room temperature.Comment: 9 pages, 4 figure
Just looking around: Supporting casual users initial encounters with Digital Cultural Heritage
ABSTRACT Cultural Heritage institutions have developed numerous ways of supporting visitors who have simply wandered in through the front door. However, for their digital collections, the CH institutions mostly provide a simple search-box, which supports the expert user, but which does not support the casual user who has just stumbled across the collection. These casual users frequently have no goal or topic in mind, but just want to have a look around what is available in the collection. For these users the blank search-box presents a significant obstacle, as without a goal or topic it is very difficult to formulate an appropriate query. In this paper we propose extending current exploratory search and information seeking models to support the initial interaction between the casual user and the collection
Multiple origins of extra electron diffractions in fcc metals
Diffuse intensities in the electron diffraction patterns of concentrated
face-centered cubic solid solutions have been widely attributed to chemical
short-range order, although this connection has been recently questioned. This
article explores the many non-ordering origins of commonly reported features
using a combination of experimental electron microscopy and multislice
diffraction simulations, which suggest that diffuse intensities largely
represent thermal and static displacement scattering. A limited number of
observations may reflect additional contributions from planar defects, surface
terminations incommensurate with bulk periodicity, or weaker dynamical effectsComment: 8 pages, 3 figure
Extra electron reflections in concentrated alloys may originate from planar defects, not short-range order
In many concentrated alloys of current interest, the observation of diffuse
superlattice intensities by transmission electron microscopy has been
attributed to the presence of chemical short-range order. This interpretation
is questioned on the basis of crystallographic considerations and theoretical
predictions of ordering. The work of Xiao and Daykin [Ultramicroscopy 53
(1994)], which shows how planar defects can produce the exact set of observed
peaks, is highlighted as an alternative explanation that would impact the
conclusions of a number of recent studies.Comment: 5 pages, 3 figure
Fracture Blisters
Fracture blisters are a relatively uncommon complication of fractures in locations of the body, such as the ankle, wrist elbow and foot, where skin adheres tightly to bone with little subcutaneous fat cushioning. The blister that results resembles that of a second degree burn
Algal food and fuel coproduction can mitigate greenhouse gas emissions while improving land and water-use efficiency
The goals of ensuring energy, water, food, and climate security can often conflict.Microalgae (algae) are
being pursued as a feedstockfor both food and fuels—primarily due to algae’s high areal yield and ability
to grow on non-arable land, thus avoiding common bioenergy-food tradeoffs. However, algal cultivation
requires significant energy inputs that may limit potential emission reductions.We examine the tradeoffs
associated with producing fuel andfood from algae at the energy–food–water–climate nexus.We use the
GCAM integrated assessment model to demonstrate that algalfood production can promote reductions
in land-use change emissions through the offset of conventional agriculture. However,fuel production,
either via co-production of algal food and fuel or complete biomass conversion to fuel, is necessary to
ensure long-term emission reductions, due to the high energy costs of cultivation. Cultivation of salt–
water algae for food products may lead to substantial freshwater savings; but, nutrients for algae
cultivation will need to be sourced from waste streams to ensure sustainability. By reducing the land
demand of food production, while simultaneously enhancingfood and energy security, algae can further
enable the development of terrestrial bioenergy technologies including those utilizing carbon capture and
storage. Our results demonstrate that large-scale algae research and commercialization efforts should
focus on developing both food and energy products to achieve environmental goals.https://iopscience.iop.org/article/10.1088/1748-9326/11/11/114006/metaPublished versio
Prospectus, October 22, 1980
INTERNATIONAL STUDENTS CELEBRATE TODAY; Letters to the Editors: Student has questions for Schumacher, Co-editor apologizes to runners, Student supports Schumacher\u27s view; PACT discusses day care; Food, beer, fun planned for Oktoberfest; Seniors to tour Parkland next week; Stories of America will be presented October 29-Nov 1; Two-hundred help celebrate: Parkland students celebrate International Students Day today; State rep. candidates express their views; PC drama department presents its fall production; PC offers Pharmacy Technician program; Fall means football... and football means Homecoming; Handle your properly; Learn to take care of you car: enroll in PC\u27s car care course; Leardship is not shout, flout, and clout; Compunds from marine animals could cure cancer; U of I\u27s John Dickel will talk; Reaching Out ; Jeff Beck gives a hot, jazzy show; Marcel Marceau: the Master isn\u27t up to par; IM football winds down: teams available for volleyball, b-ball; Career center needs guides; X-country third in invitational; PC to offer EMT refresher; Arts showcase scheduled for next week; PC Datebook; Cobras can tie for championship; Freddy\u27s record looking better; Bench Warmer: Women\u27s b-ball team looking for balance; Fast Freddy Contesthttps://spark.parkland.edu/prospectus_1980/1016/thumbnail.jp
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