Lamellar Diblock Copolymer Thin Films during Solvent Vapor Annealing Studied by GISAXS:Different Behavior of Parallel and Perpendicular Lamellae

The reorientation of lamellae and the dependence of the lamellar spacing, Dlam, on polymer volume fraction, ϕP, Dlam ∝ ϕP–β, in diblock copolymer thin films during solvent vapor annealing (SVA) are examined by combining white light interferometry (WLI) and grazing-incidence small-angle X-ray scattering (GISAXS). A thin film of lamellae-forming poly(styrene-b-butadiene) prepared by spin-coating features lamellae of different orientations with the lamellar spacing depending on orientation. During annealing with ethyl acetate (EAC) vapor, it is found that perpendicular lamellae behave differently from parallel ones, which is due to the fact that their initial lamellar thicknesses differ strongly. Quantitatively, the swelling process is composed of three regimes and the drying process of two regimes. The first two regimes of swelling are associated with a significant structural rearrangement of the lamellae; i.e., the lamellae first become thicker, and then perpendicular and randomly oriented lamellae vanish, which results in a purely parallel orientation at the end of the swelling process. The rearrangement is attributed to the increase of mobility of the polymer chains imparted by the solvent and to a decrease of total free energy of the thin film. In the third regime of swelling, the scaling exponent is found to be β = −0.32. During drying, the deswelling is nonaffine which may be a consequence of the increase of nonfavorable segmental interactions as the solvent is removed

Morphology and photoluminescence study of titania nanoparticles

Titania nanoparticles are prepared by sol–gel chemistry with a poly(ethylene oxide) methyl ether methacrylate-block-poly(dimethylsiloxane)-block-poly(ethylene oxide) methyl ether methacrylate triblock copolymer acting as the templating agent. The sol–gel components—hydrochloric acid, titanium tetraisopropoxide, and triblock copolymer—are varied to investigate their effect on the resulting titania morphology. An increased titania precursor or polymer content yields smaller primary titania structures. Microbeam grazing incidence small-angle X-ray scattering measurements, which are analyzed with a unified fit model, reveal information about the titania structure sizes. These small structures could not be observed via the used microscopy techniques. The interplay among the sol–gel components via our triblock copolymer results in different sized titania nanoparticles with higher packing densities. Smaller sized titania particles, (∼13–20 nm in diameter) in the range of exciton diffusion length, are formed by 2% by weight polymer and show good crystallinity with less surface defects and high oxygen vacancies

Economic, demographic and fiscal impacts of closing Hill Air Force Base: a statewide and regional analysis

reportThe upcoming round of Defense Base Closure and Realignment (BRAC) is threatening the existence of Hill Air Force Base (Hill AFB). The Department of Defense is aggressively approaching this round of BRAC in its attempt to eliminate 20% to 25% of current capacity. The purpose of this study is to assess the economic, demographic and fiscal impacts of closing Hill AFB on the state of Utah and on the Davis/Weber region. These impacts, which have been generated using the REMI model, project the changes in employment, population, earnings, income and business activity that result from closing Hill AFB. Hill AFB is located in northern Utah approximately 30 miles north of Salt Lake City and eight miles south of Ogden. The base currently covers almost 6,700 acres and stretches across two counties-Davis and Weber. Hill has had a presence in Utah since 1920 when the War Department established the Ogden Arsenal Army Reserve Depot in the area now occupied by the northwestern portion of Hill AFB. Over time, Hill's missions have changed and expanded. Today, the missions of Hill AFB encompass supply and repair of aircraft and missile parts, including munitions storage and handling. The base is one of three air logistics centers in the USAF Materiel Command, serving as home to the Ogden Air Logistics Center which provides worldwide engineering and logistics management for the F-16, A-10, Minuteman III and Peacekeeper Intercontinental Ballistic Missiles. Hill AFB has been the largest component of Utah's defense sector, and one of the largest employers in the state for decades. Long established as an engine of economic growth, Hill AFB directly pumps more than $1.0 billion into Utah's economy each year. The direct operations include a Utah payroll of$962.2 million, direct employment of about 20,000 workers and local purchases totaling $152.9 million.1 In 2003, Utah's defense industry (primarily Hill AFB) was a mainstay that helped steady the Utah economy. Clearly, Hill's economic contributions are substantial and an important source of economic activity in the state of Utah. The actual probability of the complete closure of Hill AFB is unknown. A partial closure scenario that retains some of the missions on the base while eliminating others is quite possibly a more likely outcome. At the request of the research sponsors, only the full closure of the base has been modeled here. Key Findings The information presented here assumes a phased shutdown of Hill AFB that begins in 2006 and is completed in 2008. For most of the analysis, the impacts are presented for 2009 and 2020. The year 2009 was selected to capture the full impact of the base closure after all military personnel and their dependents are realigned but before market adjustments begin. The year 2020 was chosen to show the long-term, permanent impact after markets adjust to the closure of Hill. Statewide Impacts (Financial projections are in constant 2001 dollars) Short-Term Impacts • In 2009, the impact of closing Hill AFB will be a loss of 47,400 jobs, an annual decline of$2.35 billion in earnings and $2.29 billion in personal income. Hill's closure shrinks the state's economy by$3.58 billion (a decline of 2.6% from the projected baseline). The annual loss of state tax revenue will be $192.4 million. • The employment impact, while considerable, does not result in large-scale unemployment. Employment growth statewide will continue as other sectors of the economy create jobs. • The population impact of closing Hill AFB will be 31,000 fewer people living in the state than if Hill remained in operation. The population impact includes about 7,600 school age children, or about 1.3$542 in 2009; this means that each person in Utah will have, on average, $542 less to spend than if Hill AFB remained in operation

Data publication: Temperature-induced surface faceting of M-plane Al₂O₃: An in-situ GISAXS study

-- raw data of GISAXS experiment -- AFM data -- GISAXS simulation file

Real-Time Observation of Temperature-Induced Surface Nanofaceting in M-Plane α\alpha-Al2O3Al_{2}O_{3}

The spontaneous crystal surface reconstruction of M-plane α-Al2O3 is employed for nanopatterning and nanofabrication in various fields of research including, among others, magnetism, superconductivity, and optoelectronics. In this reconstruction process the crystalline surface transforms from a planar morphology to one with a nanoscale ripple patterning. However, the high sample temperature required to induce surface reconstruction made in situ studies of the process seem unfeasible. The kinetics of ripple pattern formation therefore remained uncertain, and thus production of templates for nanofabrication could not advance beyond a trial-and-error stage. We present an approach combining in situ real-time grazing incidence small-angle X-ray scattering experiments (GISAXS) with model-based analysis and with ex situ atomic force microscopy (AFM) to observe this morphological transition in great detail. Our approach provides time-resolved information about all relevant morphological parameters required to trace the surface topography on the nanometer scale during reconstruction, i.e., the time dependence of the pattern wavelength, the ripple length, width, and height, and thus their facet angles. It offers a comprehensive picture of this process exemplified by a M-plane α-Al2O3 surface annealed at 1325 °C for 930 min. Fitting the model parameters to the experimental GISAXS data revealed a Johnson–Mehl–Avrami–Kolmogorov type of behavior for the pattern wavelength and a predominantly linear time dependence of the other parameters. In this case the reconstruction resulted in a crystalline surface fully patterned with asymmetric ripple-shaped nanostructures of 75 nm periodicity, 15 nm in height, and 630 nm in length. By elucidating the time dependence of these morphological parameters, this study shows a powerful way to significantly advance the predictability of annealing outcome and thus to efficiently customize nanopatterned α-Al2O3 templates for improved nanofabrication routines

In-situ GISAXS of block copolymer templated formation of magnetic nanodot arrays and their magnetic properties

The fabrication of bit-patterned media (BPM) is crucial for new types of hard disk drives. The development of methods for the production of BPM is progressing rapidly. Conventional lithography reaches the limit regarding lateral resolution, and new routes are needed. In this study, we mainly focus on the dependence of the size and shape of magnetic nanodots on the Ar+-ion etching duration, using silica dots as masks. Two-dimensional (2D) arrays of magnetic nanostructures are created using silica-filled diblock-copolymer micelles as templates. After the self-assembly of the micelles into 2D hexagonal arrays, the polymer shell is removed, and the SiO2 cores are utilized to transform the morphology into a (Co/Pt)2-multilayer via ion etching under normal incidence. The number of preparation steps is kept as low as possible to simplify the formation of the nanostructure arrays. High-resolution in situ grazing-incidence small-angle X-ray scattering (GISAXS) investigations are performed during the Ar+-ion etching to monitor and control the fabrication process. The in situ investigation provides information on how the etching conditions can be improved for further ex situ experiments. The GISAXS patterns are compared with simulations. We observe that the dots change in shape from cylindrical to conical during the etching process. The magnetic behavior is studied by utilizing the magneto-optic Kerr effect. The Co/Pt dots exhibit different magnetic behaviors depending on their size, interparticle distance, and etching time. They show ferromagnetism with an easy axis of magnetization perpendicular to the film. A systematic dependence of the coercivity on the dot size is observed

Toward an equilibrium structure in lamellar diblock copolymer thin films using solvent vapor annealing:An in-situ, time-resolved GISAXS study

Solvent vapor annealing (SVA) is frequently used to improve the ordering in diblock copolymer thin films. An important question is which SVA protocol should be chosen to ensure thermodynamic equilibrium. Here, we investigate two thin films from a low molar-mass, lamellae-forming polystyrene-block-polybutadiene (PS-b-PB) diblock copolymer (28.0 kg/mol). The films are prepared by spin-coating Si wafers from toluene solutions and have film thicknesses of 215 nm and 332 nm. The as-prepared films have mainly the parallel lamellar orientation with a lamellar thickness D$_{lam,par}$ significantly lower than in the bulk. SVA cycles were carried out with cyclohexane, and the structural changes were followed in-situ using time-resolved grazing-incidence small-angle X-ray scattering (GISAXS). Before and after SVA, D$_{lam,par}$ is significantly lower than in the bulk, i.e. the equilibrium value of Dlam,par in thin film geometry is different from the bulk value. Whereas the behavior of Dlam,par is different for the two films in the early stages of the first swelling, it is very similar in the late stages of swelling and during drying. During the first drying, the lamellae deswell, initially slowly and later, when PS becomes glassy again, affinely. During the second SVA cycle on the thin film, the scaling behavior of the lamellar thickness is identical to the one during the first drying and to the drying behavior of the thicker film. We conclude that one cycle of solvent vapor treatment with a degree of swelling of ca. 1.5 is sufficient to bring the PS-b-PB thin films studied into equilibrium and to create a nearly defect-free lamellar structure