Perfluoropolyether-Impregnated Mesoporous Alumina Composites Overcome the Dewetting-Tribological Properties Trade-Off.

Science.gov (United States)

Rowthu, Sriharitha; Hoffmann, Patrik

2018-03-28

Conventional omniphobic surfaces suffer from wear-sensitivity due to soft apolar coatings or substrates and protruding surface features that are eroded even for mild abrasion treatments, leading to the loss of dewetting properties after wear. Evidently, there was a trade-off between dewetting and tribological properties. Here, we show the establishment of self-healing slippery properties post severe abrasion by utilizing perfluoropolyether-impregnated mesoporous Al 2 O 3 (MPA) composites. The hard polar alumina matrix provides the optimal tribological properties, and the liquid lubricant in the porous network contributes to both tribological and self-healing dewetting properties. These composites sustained normal pressures up to 350 MPa during reciprocating sliding contacts. The severely abraded surfaces are capable of self-replenishing in ambient environment, driven by capillarity and surface diffusion processes, and regained their slippery properties toward water and hexadecane after 15 h of self-healing. Eventually, a dewetting-tribology diagram has been introduced to show different regimes, namely-optimal slippery properties, optimal tribological properties, and a mixed regime). We found out that the microstructural expression [Formula: see text] is a robust guiding tool to predict the regime of interest. This dewetting-tribological diagram may be marked as an inception to designing abrasion-resistant slippery liquid impregnated composites for overcoming the dewetting tribological properties trade-off. Such surfaces may potentially find applications in paint industries and as anti-icing surfaces.

Kinetics of sub-spinodal dewetting of thin films of thickness dependent viscosity.

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Kotni, Tirumala Rao; Khanna, Rajesh; Sarkar, Jayati

2017-05-04

An alternative explanation of the time varying and very low growth exponents in dewetting of polymer films like polystyrene films is presented based on non-linear simulations. The kinetics of these films is explored within the framework of experimentally observed thickness dependent viscosity. These films exhibit sub-spinodal dewetting via formation of satellite holes in between primary dewetted holes under favorable conditions of excess intermolecular forces and film thicknesses. We find that conditions responsible for sub-spinodal dewetting concurrently lead to remarkable changes in the kinetics of dewetting of even primary holes. For example, the radius of the hole grows in time with a power-law growth exponent sequence of [Formula: see text], in contrast to the usual  ∼4/5. This is due to the cumulative effect of reduced rim mobility due to thickness dependent viscosity and hindrance created by satellite holes.

Reduction of nanowire diameter beyond lithography limits by controlled catalyst dewetting

Science.gov (United States)

Calahorra, Yonatan; Kerlich, Alexander; Amram, Dor; Gavrilov, Arkady; Cohen, Shimon; Ritter, Dan

2016-04-01

Catalyst assisted vapour-liquid-solid is the most common method to realize bottom-up nanowire growth; establishing a parallel process for obtaining nanoscale catalysts at pre-defined locations is paramount for further advancement towards commercial nanowire applications. Herein, the effect of a selective area mask on the dewetting of metallic nanowire catalysts, deposited within lithography-defined mask pinholes, is reported. It was found that thin disc-like catalysts, with diameters of 120-450 nm, were transformed through dewetting into hemisphere-like catalysts, having diameters 2-3 fold smaller; the process was optimized to about 95% yield in preventing catalyst splitting, as would otherwise be expected due to their thickness-to-diameter ratio, which was as low as 1/60. The catalysts subsequently facilitated InP and InAs nanowire growth. We suggest that the mask edges prevent surface migration mediated spreading of the dewetted metal, and therefore induce its agglomeration into a single particle. This result presents a general strategy to diminish lithography-set dimensions for NW growth, and may answer a fundamental challenge faced by bottom-up nanowire technology.

The Influence of Cross-Sectional Shape and Orientation of Micropillar Surface on Microdroplet Formation by a Dewetting Process

Directory of Open Access Journals (Sweden)

Bambang Arip Dwiyantoro

2013-07-01

Full Text Available In this study the dewetting process on micropillars of three different cross-sectional shapes, i.e. circular, square and triangular, was numerically investigated. The influence of the orientation of the triangular and square micropillars on the dewetting behavior was also studied. The numerical simulations showed that the cross-sectional shapes of the micropillars and their orientation play an important role in determining the flow pattern of the dewetting process, especially the evolution and movement of the meniscus across the micropillar before a microdroplet is formed. The diameter of the microdroplets is mainly determined by the capillary effect, viscous drag and fluid inertia contributed by the peeling rate and the thickness of the water layer above the micropillar. The numerical results also indicate that the hydraulic diameter of the micropillars (Dp is one of the parameters governing the size of the microdroplets formed on the top surface of the micropillars after the dewetting process, while the microdroplet diameter is almost insensitive to the cross-sectional shape and orientation of the micropillars. The dimensionless diameter of the microdroplets (d can then be expressed as a function of a dimensionless group, i.e. the Ohnesorge number (Oh, the capillary number (Ca, the dimensionless liquid thickness (H, and the contact angle (q.

Influence of film structure on the dewetting kinetics of thin polymer films in the solvent annealing process.

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Zhang, Huanhuan; Xu, Lin; Lai, Yuqing; Shi, Tongfei

2016-06-28

On a non-wetting solid substrate, the solvent annealing process of a thin polymer film includes the swelling process and the dewetting process. Owing to difficulties in the in situ analysis of the two processes simultaneously, a quantitative study on the solvent annealing process of thin polymer films on the non-wetting solid substrate is extremely rare. In this paper, we design an experimental method by combining spectroscopic ellipsometry with optical microscopy to achieve the simultaneous in situ study. Using this method, we investigate the influence of the structure of swollen film on its dewetting kinetics during the solvent annealing process. The results show that for a thin PS film with low Mw (Mw = 4.1 kg mol(-1)), acetone molecules can form an ultrathin enriched layer between the PS film and the solid substrate during the swelling process. The presence of the acetone enriched layer accounts for the exponential kinetic behavior in the case of a thin PS film with low Mw. However, the acetone enriched layer is not observed in the case of a thin PS film with high Mw (Mw = 400 kg mol(-1)) and the slippage effect of polymer chains is valid during the dewetting process.

The dewetting properties of lotus leaves.

Science.gov (United States)

Zhang, Jihua; Sheng, Xianliang; Jiang, Lei

2009-02-03

The high dewetting abilities of lotus leaves can be transited to a complete wetting state by soaking the leaves in water at a depth of 50 cm for 2 h. However, after being dried by N2 gas, the high dewetting behavior of lotus leaves may be mostly restored. This indicates that experimental procedure might considerably affect the dewetting abilities of lotus leaves. To discover the mechanism underlying this interesting dewetting phenomena, the dewetting force was used to characterize the dewetting abilities of surfaces, and model studies to mimic the papillae were done. Surface hydrophobicity, sizes, rise angles, and secondary structures of the models' sides affected their dewetting force with water. So we suggested that the dewetting states, Cassie or Wenzel's state, of lotus surfaces depend much on the depth of water, i.e., the hydraulic pressure. On the other hand, the primary structures of papillae in Cassie's state led to a high receding angle with respect to the plane of the leaf during the dewetting measurement. The secondary structures and micro/nano arrays of papillae increased the dewetting abilities of lotus leaves, since no water intruded between papillae. However, the structures of papillae in Wenzle's state significantly reduced the dewetting abilities of lotus leaves after being soaked at a depth of 50 cm for 2 h. Therefore, as for novel designs of microdevices floating on water, including the use of the high dewetting properties of suphydrophobic materials, surface (primary or secondary) microstructure and external pressure, such as static hydraulic pressure, must be taken into account.

Enhanced Self-Organized Dewetting of Ultrathin Polymer Blend Film for Large-Area Fabrication of SERS Substrate.

Science.gov (United States)

Zhang, Huanhuan; Xu, Lin; Xu, Yabo; Huang, Gang; Zhao, Xueyu; Lai, Yuqing; Shi, Tongfei

2016-12-06

We study the enhanced dewetting of ultrathin Polystyrene (PS)/Poly (methyl methacrylate) (PMMA) blend films in a mixed solution, and reveal the dewetting can act as a simple and effective method to fabricate large-area surface-enhanced Raman scattering (SERS) substrate. A bilayer structure consisting of under PMMA layer and upper PS layer forms due to vertical phase separation of immiscible PS/PMMA during the spin-coating process. The thicker layer of the bilayer structure dominates the dewetting structures of PS/PMMA blend films. The diameter and diameter distribution of droplets, and the average separation spacing between the droplets can be precisely controlled via the change of blend ratio and film thickness. The dewetting structure of 8 nm PS/PMMA (1:1 wt%) blend film is proved to successfully fabricate large-area (3.5 cm × 3.5 cm) universal SERS substrate via deposited a silver layer on the dewetting structure. The SERS substrate shows good SERS-signal reproducibility (RSD dewetting of polymer blend films broadens the application of dewetting of polymer films, especially in the nanotechnology, and may open a new approach for the fabrication of large-area SERS substrate to promote the application of SERS substrate in the rapid sensitive detection of trace molecules.

Molecular dewetting on insulators

International Nuclear Information System (INIS)

Burke, S A; Topple, J M; Gruetter, P

2009-01-01

Recent attention given to the growth and morphology of organic thin films with regard to organic electronics has led to the observation of dewetting (a transition from layer(s) to islands) of molecular deposits in many of these systems. Dewetting is a much studied phenomenon in the formation of polymer and liquid films, but its observation in thin films of the 'small' molecules typical of organic electronics requires additional consideration of the structure of the interface between the molecular film and the substrate. This review covers some key concepts related to dewetting and molecular film growth. In particular, the origins of different growth modes and the thickness dependent interactions which give rise to dewetting are discussed in terms of surface energies and the disjoining pressure. Characteristics of molecular systems which may lead to these conditions, including the formation of metastable interface structures and commensurate-incommensurate phase transitions, are also discussed. Brief descriptions of some experimental techniques which have been used to study molecular dewetting are given as well. Examples of molecule-on-insulator systems which undergo dewetting are described in some detail, specifically perylene derivatives on alkali halides, C 60 on alkali halides, and the technologically important system of pentacene on SiO 2 . These examples point to some possible predicting factors for the occurrence of dewetting, most importantly the formation of an interface layer which differs from the bulk crystal structure. (topical review)

Molecular dewetting on insulators.

Science.gov (United States)

Burke, S A; Topple, J M; Grütter, P

2009-10-21

Recent attention given to the growth and morphology of organic thin films with regard to organic electronics has led to the observation of dewetting (a transition from layer(s) to islands) of molecular deposits in many of these systems. Dewetting is a much studied phenomenon in the formation of polymer and liquid films, but its observation in thin films of the 'small' molecules typical of organic electronics requires additional consideration of the structure of the interface between the molecular film and the substrate. This review covers some key concepts related to dewetting and molecular film growth. In particular, the origins of different growth modes and the thickness dependent interactions which give rise to dewetting are discussed in terms of surface energies and the disjoining pressure. Characteristics of molecular systems which may lead to these conditions, including the formation of metastable interface structures and commensurate-incommensurate phase transitions, are also discussed. Brief descriptions of some experimental techniques which have been used to study molecular dewetting are given as well. Examples of molecule-on-insulator systems which undergo dewetting are described in some detail, specifically perylene derivatives on alkali halides, C(60) on alkali halides, and the technologically important system of pentacene on SiO(2). These examples point to some possible predicting factors for the occurrence of dewetting, most importantly the formation of an interface layer which differs from the bulk crystal structure.

Anisotropic dewetting of ion irradiated solid films

Energy Technology Data Exchange (ETDEWEB)

Repetto, L., E-mail: luca.repetto@unige.it [Dipartimento di fisica, Università di Genova, Via Dodecaneso 33, 16146 Genova (Italy); Šetina Batič, B. [Inštitut Za Kovinske Materiale in Tehnologije, Lepi pot 11, 1000 Ljubljana (Slovenia); Firpo, G.; Piano, E.; Valbusa, U. [Dipartimento di fisica, Università di Genova, Via Dodecaneso 33, 16146 Genova (Italy)

2013-11-15

Experiments of irradiation with 30 keV Ga ions were conducted on ultrathin chromium films on rippled silicon substrates. The evolution of their surface morphology, as detected by real time scanning electron microscopy, shows an apparent differential sputtering yield for regions of positive and negative curvature which is in contrast with the standard theory for curvature depending sputtering yield. In particular, at the end of the irradiation process, chromium wires are left in the valleys of the substrate. This result was explained in terms of local melting caused by the ion impact and of a process of dewetting under the concurring actions of surface tension and Van der Waals forces while ion sputtering is active. The interpretation of the reported experimental results are fully supported by numeric simulations implementing the same continuum model used to explain ion induced spinodal dewetting. This hierarchical self-organization process breaks the symmetry of previously demonstrated ion induced dewetting, making possible to create new structures by using the same fundamental effects.

Not spreading in reverse: The dewetting of a liquid film into a single drop.

Science.gov (United States)

Edwards, Andrew M J; Ledesma-Aguilar, Rodrigo; Newton, Michael I; Brown, Carl V; McHale, Glen

2016-09-01

Wetting and dewetting are both fundamental modes of motion of liquids on solid surfaces. They are critically important for processes in biology, chemistry, and engineering, such as drying, coating, and lubrication. However, recent progress in wetting, which has led to new fields such as superhydrophobicity and liquid marbles, has not been matched by dewetting. A significant problem has been the inability to study the model system of a uniform film dewetting from a nonwetting surface to a single macroscopic droplet-a barrier that does not exist for the reverse wetting process of a droplet spreading into a film. We report the dewetting of a dielectrophoresis-induced film into a single equilibrium droplet. The emergent picture of the full dewetting dynamics is of an initial regime, where a liquid rim recedes at constant speed and constant dynamic contact angle, followed by a relatively short exponential relaxation of a spherical cap shape. This sharply contrasts with the reverse wetting process, where a spreading droplet follows a smooth sequence of spherical cap shapes. Complementary numerical simulations and a hydrodynamic model reveal a local dewetting mechanism driven by the equilibrium contact angle, where contact line slip dominates the dewetting dynamics. Our conclusions can be used to understand a wide variety of processes involving liquid dewetting, such as drop rebound, condensation, and evaporation. In overcoming the barrier to studying single film-to-droplet dewetting, our results provide new approaches to fluid manipulation and uses of dewetting, such as inducing films of prescribed initial shapes and slip-controlled liquid retraction.

Reduction of nanowire diameter beyond lithography limits by controlled catalyst dewetting

International Nuclear Information System (INIS)

Calahorra, Yonatan; Kerlich, Alexander; Gavrilov, Arkady; Cohen, Shimon; Ritter, Dan; Amram, Dor

2016-01-01

Catalyst assisted vapour-liquid–solid is the most common method to realize bottom-up nanowire growth; establishing a parallel process for obtaining nanoscale catalysts at pre-defined locations is paramount for further advancement towards commercial nanowire applications. Herein, the effect of a selective area mask on the dewetting of metallic nanowire catalysts, deposited within lithography-defined mask pinholes, is reported. It was found that thin disc-like catalysts, with diameters of 120–450 nm, were transformed through dewetting into hemisphere-like catalysts, having diameters 2–3 fold smaller; the process was optimized to about 95% yield in preventing catalyst splitting, as would otherwise be expected due to their thickness-to-diameter ratio, which was as low as 1/60. The catalysts subsequently facilitated InP and InAs nanowire growth. We suggest that the mask edges prevent surface migration mediated spreading of the dewetted metal, and therefore induce its agglomeration into a single particle. This result presents a general strategy to diminish lithography-set dimensions for NW growth, and may answer a fundamental challenge faced by bottom-up nanowire technology. (paper)

The kinetics of dewetting ultra-thin Si layers from silicon dioxide

International Nuclear Information System (INIS)

Aouassa, M; Favre, L; Ronda, A; Berbezier, I; Maaref, H

2012-01-01

In this study, we investigate the kinetically driven dewetting of ultra-thin silicon films on silicon oxide substrate under ultra-high vacuum, at temperatures where oxide desorption and silicon lost could be ruled out. We show that in ultra-clean experimental conditions, the three different regimes of dewetting, namely (i) nucleation of holes, (ii) film retraction and (iii) coalescence of holes, can be quantitatively measured as a function of temperature, time and thickness. For a nominal flat clean sample these three regimes co-exist during the film retraction until complete dewetting. To discriminate their roles in the kinetics of dewetting, we have compared the dewetting evolution of flat unpatterned crystalline silicon layers (homogeneous dewetting), patterned crystalline silicon layers (heterogeneous dewetting) and amorphous silicon layers (crystallization-induced dewetting). The first regime (nucleation) is described by a breaking time which follows an exponential evolution with temperature with an activation energy E H ∼ 3.2 eV. The second regime (retraction) is controlled by surface diffusion of matter from the edges of the holes. It involves a very fast redistribution of matter onto the flat Si layer, which prevents the formation of a rim on the edges of the holes during both heterogeneous and homogeneous dewetting. The time evolution of the linear dewetting front measured during heterogeneous dewetting follows a characteristic power law x ∼ t 0.45 consistent with a surface diffusion-limited mechanism. It also evolves as x ∼ h -1 as expected from mass conservation in the absence of thickened rim. When the surface energy is isotropic (during dewetting of amorphous Si) the dynamics of dewetting is considerably modified: firstly, there is no measurable breaking time; secondly, the speed of dewetting is two orders of magnitude larger than for crystalline Si; and thirdly, the activation energy of dewetting is much smaller due to the different driving

Nanoscale View of Dewetting and Coating on Partially Wetted Solids.

Science.gov (United States)

Deng, Yajun; Chen, Lei; Liu, Qiao; Yu, Jiapeng; Wang, Hao

2016-05-19

There remain significant gaps in our ability to predict dewetting and wetting despite the extensive study over the past century. An important reason is the absence of nanoscopic knowledge about the processes near the moving contact line. This experimental study for the first time obtained the liquid morphology within 10 nm of the contact line, which was receding at low speed (U dewetting far from a simple reverse of wetting. A complete scenario for dewetting and coating is provided.

Templated dewetting: designing entirely self-organized platforms for photocatalysis.

Science.gov (United States)

Altomare, Marco; Nguyen, Nhat Truong; Schmuki, Patrik

2016-12-01

Formation and dispersion of metal nanoparticles on oxide surfaces in site-specific or even arrayed configuration are key in various technological processes such as catalysis, photonics, electrochemistry and for fabricating electrodes, sensors, memory devices, and magnetic, optical, and plasmonic platforms. A crucial aspect towards an efficient performance of many of these metal/metal oxide arrangements is a reliable fabrication approach. Since the early works on graphoepitaxy in the 70s, solid state dewetting of metal films on patterned surfaces has been much explored and regarded as a most effective tool to form defined arrays of ordered metal particles on a desired substrate. While templated dewetting has been studied in detail, particularly from a mechanistic perspective on lithographically patterned Si surfaces, the resulting outstanding potential of its applications on metal oxide semiconductors, such as titania, has received only limited attention. In this perspective we illustrate how dewetting and particularly templated dewetting can be used to fabricate highly efficient metal/TiO 2 photocatalyst assemblies e.g. for green hydrogen evolution. A remarkable advantage is that the synthesis of such photocatalysts is completely based on self-ordering principles: anodic self-organized TiO 2 nanotube arrays that self-align to a highest degree of hexagonal ordering are an ideal topographical substrate for a second self-ordering process, that is, templated-dewetting of sputter-deposited metal thin films. The controllable metal/semiconductor coupling delivers intriguing features and functionalities. We review concepts inherent to dewetting and particularly templated dewetting, and outline a series of effective tools that can be synergistically interlaced to reach fine control with nanoscopic precision over the resulting metal/TiO 2 structures (in terms of e.g. high ordering, size distribution, site specific placement, alloy formation) to maximize their photocatalytic

Solid-state dewetting of Au/Ni bilayers: The effect of alloying on morphology evolution

International Nuclear Information System (INIS)

Herz, A.; Wang, D.; Kups, Th.; Schaaf, P.

2014-01-01

The solid-state dewetting of thin Au/Ni bilayers deposited onto SiO 2 /Si substrates is investigated. A rapid thermal treatment is used to induce the dewetting process by an increase in temperature. The evolution of the (111) peaks of X-ray diffraction reveals a characteristic change due to mixing of Au and Ni. At low temperature, the Au-Ni thin film is found to break up at the phase boundaries and growing voids are shown to be surrounded by a Ni-rich phase. Branch-like void growth is observed. Upon annealing at increasing temperatures, Au-Ni solid solutions are formed well above the bulk equilibrium solubility of Au and Ni. It is found that this metastable phase formation makes the Au-Ni thin film less vulnerable to rupturing. Moreover, growth mode of still evolving voids changes into a more regular, faceted one due to alloying. Finally, it is shown that annealing above the miscibility gap forms supersaturated, well-oriented Au-Ni solid solution agglomerates via dewetting.

Solid-state dewetting of Au/Ni bilayers: The effect of alloying on morphology evolution

Energy Technology Data Exchange (ETDEWEB)

Herz, A.; Wang, D., E-mail: dong.wang@tu-ilmenau.de; Kups, Th.; Schaaf, P. [Institute of Materials Engineering and Institute of Micro- and Nanotechnologies MacroNano, Chair Materials for Electronics and Electrical Engineering, TU Ilmenau, Ilmenau 98693 (Germany)

2014-07-28

The solid-state dewetting of thin Au/Ni bilayers deposited onto SiO{sub 2}/Si substrates is investigated. A rapid thermal treatment is used to induce the dewetting process by an increase in temperature. The evolution of the (111) peaks of X-ray diffraction reveals a characteristic change due to mixing of Au and Ni. At low temperature, the Au-Ni thin film is found to break up at the phase boundaries and growing voids are shown to be surrounded by a Ni-rich phase. Branch-like void growth is observed. Upon annealing at increasing temperatures, Au-Ni solid solutions are formed well above the bulk equilibrium solubility of Au and Ni. It is found that this metastable phase formation makes the Au-Ni thin film less vulnerable to rupturing. Moreover, growth mode of still evolving voids changes into a more regular, faceted one due to alloying. Finally, it is shown that annealing above the miscibility gap forms supersaturated, well-oriented Au-Ni solid solution agglomerates via dewetting.

Sub-10 nm structures on silicon by thermal dewetting of platinum

International Nuclear Information System (INIS)

Strobel, Sebastian; Kirkendall, Christopher; Chang, Jae-Byum; Berggren, Karl K

2010-01-01

A study of the dewetting behavior of platinum-thin-films on silicon was carried out to determine how variation of dewetting parameters affects the evolution of film morphology and to pinpoint which parameters yielded the smallest, most circular features. Platinum film thickness as well as dewetting time and temperature were varied and the film morphology characterized by means of scanning electron microscopy (SEM) analysis. Two different pathways of dewetting predicted in the literature (Vrij 1966 Discuss. Faraday Soc. 42 23, Becker et al 2003 Nat. Mater. 2 59-63) were observed. Depending on the initial criteria, restructuring of the film occurred via hole or droplet formation. With increased annealing time, a transition from an intermediate network structure to separated islands occurred. In addition, the formation of multilayered films, silicide crystals and nanowires occurred for certain parameters. Nevertheless, the dewetting behavior witnessed could be related to physical processes. Droplets with a mean diameter of 9 nm were formed by using a 1.5 nm thick platinum film annealed at 800 deg. C for 30 s. To demonstrate the suitability of the annealed films for further processing, we then used the dewetted films as masks for reactive ion etching to transfer the pattern into the silicon substrate, forming tapered nanopillars.

On sub-T(g) dewetting of nanoconfined liquids and autophobic dewetting of crystallites.

Science.gov (United States)

Souda, Ryutaro

2012-03-28

The glass transition temperature (T(g)) of thin films is reduced by nanoconfinement, but it is also influenced by the free surface and substrate interface. To gain more insights into their contributions, dewetting behaviors of n-pentane, 3-methylpentane, and toluene films are investigated on various substrates as functions of temperature and film thickness. It is found that monolayers of these molecules exhibit sub-T(g) dewetting on a perfluoro-alkyl modified Ni substrate, which is attributable to the evolution of a 2D liquid. The onset temperature of dewetting increases with film thickness because fluidity evolves via cooperative motion of many molecules; sub-T(g) dewetting is observed for films thinner than 5 monolayers. In contrast, monolayers wet substrates of graphite, silicon, and amorphous solid water until crystallization occurs. The crystallites exhibit autophobic dewetting on the substrate covered with a wetting monolayer. The presence of premelting layers is inferred from the fact that n-pentane crystallites disappear on amorphous solid water via intermixing. Thus, the properties of quasiliquid formed on the crystallite surface differ significantly from those of the 2D liquid formed before crystallization.

Role of substrate morphology in ion induced dewetting of thin solid films

Energy Technology Data Exchange (ETDEWEB)

Repetto, Luca, E-mail: luca.repetto@unige.it [Physics Department and Nanomed Labs, Università di Genova, Via Dodecaneso 33, 16146 Genova (Italy); Lo Savio, Roberto [Physics Department and Nanomed Labs, Università di Genova, Via Dodecaneso 33, 16146 Genova (Italy); Šetina Batič, Barbara [Inštitut Za Kovinske Materiale in Tehnologije, Lepi pot 11, 1000 Ljubljana (Slovenia); Firpo, Giuseppe; Valbusa, Ugo [Physics Department and Nanomed Labs, Università di Genova, Via Dodecaneso 33, 16146 Genova (Italy)

2014-10-01

Highlights: • We have created by ion bombardment silicon substrates with different topographies. • The substrates have been characterized by ellipsometry, AFM, SEM and EDX. • The substrates have been used for experiments of ion induced Cr films. • We show that different substrate topographies can induce different dewetted patterns. • Substrate topography can favor spinodal dewetting against heterogeneous nucleations. - Abstract: We investigate the role of the substrate morphology in the dewetting of ultrathin chromium films irradiated with 30 keV Ga ions. Silicon surfaces with different roughness were used as substrates for the films. The results of the irradiation experiments and of related simulations indicate that the chromium films can undergo a dewetting-like process through the two standard channels that show up for liquids, namely the spinodal channel, and the dewetting by heterogeneous nucleation. The two processes are competitive, and the prevailing one can be predicted and selected according to the characteristics of the substrate.

Role of substrate morphology in ion induced dewetting of thin solid films

International Nuclear Information System (INIS)

Repetto, Luca; Lo Savio, Roberto; Šetina Batič, Barbara; Firpo, Giuseppe; Valbusa, Ugo

2014-01-01

Highlights: • We have created by ion bombardment silicon substrates with different topographies. • The substrates have been characterized by ellipsometry, AFM, SEM and EDX. • The substrates have been used for experiments of ion induced Cr films. • We show that different substrate topographies can induce different dewetted patterns. • Substrate topography can favor spinodal dewetting against heterogeneous nucleations. - Abstract: We investigate the role of the substrate morphology in the dewetting of ultrathin chromium films irradiated with 30 keV Ga ions. Silicon surfaces with different roughness were used as substrates for the films. The results of the irradiation experiments and of related simulations indicate that the chromium films can undergo a dewetting-like process through the two standard channels that show up for liquids, namely the spinodal channel, and the dewetting by heterogeneous nucleation. The two processes are competitive, and the prevailing one can be predicted and selected according to the characteristics of the substrate

Competition between dewetting and cross-linking in poly(N-vinylpyrrolidone)/polystyrene bilayer films.

Science.gov (United States)

Telford, Andrew M; Thickett, Stuart C; James, Michael; Neto, Chiara

2011-12-06

We investigated the dewetting of metastable poly(N-vinylpyrrolidone) (PNVP) thin films (45 nm) on top of polystyrene (PS) thin films (58 nm) as a function of annealing temperature and molecular weight of PS (96 and 6850 kg/mol). We focused on the competition between dewetting, occurring as a result of unfavorable intermolecular interactions at the PNVP/PS interface, and spontaneous cross-linking of PNVP, occurring during thermal annealing, as we recently reported (Telford, A. M.; James, M.; Meagher, L.; Neto, C. ACS Appl. Mater. Interfaces 2010, 2, 2399-2408). Using optical microscopy, we studied how the dewetting morphology and dynamics at different temperatures depended on the relative viscosity of the top PNVP film, which increased with cross-linking time, and of the bottom PS film. In the PNVP/PS96K system, cross-linking dominated over dewetting at temperatures below 180 °C, reducing drastically nucleated hole density and their maximum size, while above 180 °C the two processes reversed, with complete dewetting occurring at 200 °C. On the other hand, the PNVP/PS6850K system never achieved advanced dewetting stages as the dewetting was slower than cross-linking in the investigated temperature range. In both systems, dewetting of the PNVP films could be avoided altogether by thermally annealing the bilayers at temperatures where cross-linking dominated. The cross-linking was characterized quantitatively using neutron reflectometry, which indicated shrinkage and densification of the PNVP film, and qualitatively through selective removal of the bottom PS film. A simple model accounting for progressive cross-linking during the dewetting process predicted well the observed hole growth profiles and produced estimates of the PNVP cross-linking rate coefficients and of the activation energy of the process, in good agreement with literature values for similar systems. © 2011 American Chemical Society

Domain growth of carbon nanotubes assisted by dewetting of thin catalyst precursor films

Energy Technology Data Exchange (ETDEWEB)

Srivastava, Alok Kumar [Defence Materials and Stores R and D Establishment (DRDO), GT Road, Kanpur 208013 (India); Department of Chemical Engineering, Indian Institute of Technology, Kanpur 208016 (India); Sachan, Priyanka; Samanta, Chandan [Department of Chemical Engineering, Indian Institute of Technology, Kanpur 208016 (India); Mukhopadhyay, Kingsuk [Defence Materials and Stores R and D Establishment (DRDO), GT Road, Kanpur 208013 (India); Sharma, Ashutosh, E-mail: ashutos@iitk.ac.in [Department of Chemical Engineering, Indian Institute of Technology, Kanpur 208016 (India)

2014-01-01

We explore self-organized dewetting of ultrathin films of a novel metal complex as a one step surface patterning method to create nanoislands of iron, using which spatially separated carbon nanostructures were synthesized. Dewetting of ultrathin metal complex films was induced by two different methods: liquid solvent exposure and thermal annealing to engender surface patterning. For thermal dewetting, thin films of the iron oleate complex were dewetted at high temperature. In the case of liquid solvent assisted dewetting, the metal complex, mixed with a sacrificial polymer (polystyrene) was spin coated as thin films (<40 nm) and then dewetted under an optimal solution mixture consisting of methyl ethyl ketone, acetone and water. The carrier polymer was then selectively removed to produce the iron metal islands. These metal islands were used for selective growth of discrete patches of multiwall CNTs and CNFs by a chemical vapor deposition (CVD) process. Solvent induced dewetting showed clear advantages over thermal dewetting owing to reduced size of catalyst domains formed by dewetting, an improved control over CNT growth as well as in its ability to immobilize the seed particles. The generic solution mediated dewetting and pattern generation in thin films of various catalytic precursors can thus be a powerful method for selective domain growth of a variety of functional nanomaterials.

Mechanism of solid-state plasma-induced dewetting for formation of copper and gold nanoparticles.

Science.gov (United States)

Kwon, Soon-Ho; Choe, Han Joo; Lee, Hyo-Chang; Chung, Chin-Wook; Lee, Jung-Joong

2013-09-01

Cu and Au nanoparticles were fabricated by plasma treatment on Cu and Au films at 653 K. The nanoparticles were formed by dewetting the metallic films using plasma. Scanning electron microscopy and transmission electron microscopy investigations showed that the plasma-induced dewetting of the Cu and Au films proceeded through heterogeneous hole nucleation and growth along the grain boundaries to lower the surface energy. The amount of energy transferred to surface atoms by one Ar ion was calculated to be 16.1 eV, which was sufficient for displacing Cu and Au atoms. Compared to thermally activated dewetting, more uniform particles could be obtained by plasma-induced dewetting because a much larger number of holes with smaller sizes was generated. The plasma dewetting process is less sensitive to the oxidation of metallic films compared to the annealing process. As a result, Cu nanoparticles could be fabricated at 653 K, whereas the thermally activated dewetting was not possible.

Nucleation mechanisms in high energy ion beam induced dewetting

Energy Technology Data Exchange (ETDEWEB)

Haag, Michael; Garmatter, Daniel; Ferhati, Redi; Amirthapandian, Sankarakumar; Bolse, Wolfgang [Institut fuer Halbleiteroptik und Funktionelle Grenzflaechen, Universitaet Stuttgart (Germany)

2011-07-01

Solid coatings, when heated above their melting points, often break up by forming small round holes, which then grow, coalesce and finally turn the initially contiguous film into a pattern of isolated droplets. Such dewetting has been intensively studied using thin polymer films on Si. Three different hole nucleation mechanisms were discovered: homogeneous (spontaneous) nucleation, heterogeneous nucleation at defects, and spinodal dewetting by self-amplifying capillary waves. We have recently found that swift heavy ion (SHI) irradiation of thin oxide films on Si results in similar dewetting patterns, even though the films were kept far below their melting points. Using our new in-situ SEM at the UNILAC accelerator of GSI, we were now able to identify the mechanisms behind this SHI induced dewetting phenomenon. By varying the film thickness and introducing defects at the interface, we can directly address the hole nucleation processes. Besides homogeneous and heterogeneous nucleation, we also found a process, which very much resembles the spinodal mechanism found for liquid polymers, although in the present case the instable wavy surface is not generated by capillary waves, but by ion beam induced stresses.

Chemically-induced solid-state dewetting of thin Au films

International Nuclear Information System (INIS)

Gazit, Nimrod; Klinger, Leonid; Rabkin, Eugen

2017-01-01

We employed the solid state dewetting technique to produce nanoparticles of silver-gold alloy on a sapphire substrate. We deposited a thin gold layer on the substrate with alloy nanoparticles, and studied its thermal stability at low homological temperatures. We demonstrated that a large number of densely spaced holes form at the initial stages of dewetting of the gold layer with nanoparticles. A similar homogeneous gold film deposited on a bare sapphire substrate remained stable under identical annealing conditions, exhibiting the onset of dewetting at higher temperatures, and with a lower number of holes. We attributed the decreased thermal stability of the gold film deposited on the substrate with the silver-gold nanoparticles to accelerated grooving at the grain boundaries and triple junctions in the film. The grooving process is accelerated by the diffusion fluxes of Au atoms driven from the film towards the nanoparticles by the gradient of chemical potential. We developed a quantitative model of this chemically-induced dewetting process, and discussed its applicability for the design of better catalytic systems. Our work demonstrates that the chemical driving forces have to be reckoned with in the analysis of thermal stability of multicomponent thin films.

High aspect ratio 10-nm-scale nanoaperture arrays with template-guided metal dewetting.

Science.gov (United States)

Wang, Ying Min; Lu, Liangxing; Srinivasan, Bharathi Madurai; Asbahi, Mohamed; Zhang, Yong Wei; Yang, Joel K W

2015-04-10

We introduce an approach to fabricate ordered arrays of 10-nm-scale silica-filled apertures in a metal film without etching or liftoff. Using low temperature (dewetting of metal films guided by nano-patterned templates, apertures with aspect ratios up to 5:1 are demonstrated. Apertures form spontaneously during the thermal process without need for further processing. Although the phenomenon of dewetting has been well studied, this is the first demonstration of its use in the fabrication of nanoapertures in a spatially controllable manner. In particular, the achievement of 10-nm length-scale patterning at high aspect ratio with thermal dewetting is unprecedented. By varying the nanotemplate design, we show its strong influence over the positions and sizes of the nanoapertures. In addition, we construct a three-dimensional phase field model of metal dewetting on nano-patterned substrates. The simulation data obtained closely corroborates our experimental results and reveals new insights to template dewetting at the nanoscale. Taken together, this fabrication method and simulation model form a complete toolbox for 10-nm-scale patterning using template-guided dewetting that could be extended to a wide range of material systems and geometries.

Time-resolved analysis of thickness-dependent dewetting and ablation of silver films upon nanosecond laser irradiation

International Nuclear Information System (INIS)

Qi, Dongfeng; Paeng, Dongwoo; Yeo, Junyeob; Kim, Eunpa; Wang, Letian; Grigoropoulos, Costas P.; Chen, Songyan

2016-01-01

Nanosecond pulsed laser dewetting and ablation of thin silver films is investigated by time-resolved imaging. Laser pulses of 532 nm wavelength and 5 ns temporal width are irradiated on silver films of different thicknesses (50 nm, 80 nm, and 350 nm). Below the ablation threshold, it is observed that the dewetting process does not conclude until 630 ns after the laser irradiation for all samples, forming droplet-like particles in the spot central region. At higher laser intensities, ablative material removal occurs in the spot center. Cylindrical rims are formed in the peripheral dewetting zone due to the solidification of transported matter at about 700 ns following the laser pulse exposure. In addition to these features, droplet fingers are superposed upon irradiation of 350-nm thick silver films with higher intensity.

Time-resolved analysis of thickness-dependent dewetting and ablation of silver films upon nanosecond laser irradiation

Energy Technology Data Exchange (ETDEWEB)

Qi, Dongfeng [Laser Thermal Laboratory, Department of Mechanical Engineering, University of California, Berkeley, California 94720-1740 (United States); Semiconductor Photonics Research Center, Department of Physics, Xiamen University, Xiamen 361005 (China); Paeng, Dongwoo; Yeo, Junyeob; Kim, Eunpa; Wang, Letian; Grigoropoulos, Costas P., E-mail: cgrigoro@berkeley.edu [Laser Thermal Laboratory, Department of Mechanical Engineering, University of California, Berkeley, California 94720-1740 (United States); Chen, Songyan [Semiconductor Photonics Research Center, Department of Physics, Xiamen University, Xiamen 361005 (China)

2016-05-23

Nanosecond pulsed laser dewetting and ablation of thin silver films is investigated by time-resolved imaging. Laser pulses of 532 nm wavelength and 5 ns temporal width are irradiated on silver films of different thicknesses (50 nm, 80 nm, and 350 nm). Below the ablation threshold, it is observed that the dewetting process does not conclude until 630 ns after the laser irradiation for all samples, forming droplet-like particles in the spot central region. At higher laser intensities, ablative material removal occurs in the spot center. Cylindrical rims are formed in the peripheral dewetting zone due to the solidification of transported matter at about 700 ns following the laser pulse exposure. In addition to these features, droplet fingers are superposed upon irradiation of 350-nm thick silver films with higher intensity.

Influence of the substrate on the morphological evolution of gold thin films during solid-state dewetting

International Nuclear Information System (INIS)

Nsimama, Patrick D.; Herz, Andreas; Wang, Dong; Schaaf, Peter

2016-01-01

Highlights: • Dewetting of thin gold films is faster on TiO_2 than on SiO_2. • Dewetting of thin gold films is faster on amorphous TiO_2 than on crystalline TiO_2. • The kinetics is attributed to the energy of adhesion. • The morphology of thin Au films deposited on TiO_2 substrates is different to those deposited on SiO_2 substrates. • The dewetting activation energy of Au films deposited on crystalline substrates was higher than the activation energy of Au nanofilms deposited on amorphous TiO_2 substrates. - Abstract: The evolution of electron-beam evaporated Au thin films deposited on crystalline TiO_2 (c-TiO_2) and amorphous TiO_2 (a-TiO_2) as well as amorphous SiO_2 substrates are investigated. The kinetic of dewetting is clearly dependent on the type of substrate and is faster on TiO_2 substrates than on SiO_2 substrates. This difference can result from the difference in adhesion energy. Furthermore, the kinetic of dewetting is faster on a-TiO_2 than on c-TiO_2, possibly due to the crystallization of TiO_2 during annealing induced dewetting process. The morphologies of dewetted Au films deposited on crystalline TiO_2 are characterized by branched holes. The XRD patterns of the Au films deposited on TiO_2 substrates constituted peaks from both metallic Au and anatase TiO_2. The activation energy of Au films deposited on crystalline TiO_2 substrates was higher than that that of the films deposited on amorphous TiO_2 substrates.

Oxygen-induced inhibition of silicon-on-insulator dewetting

Energy Technology Data Exchange (ETDEWEB)

Curiotto, S.; Leroy, F.; Cheynis, F.; Müller, P. [Aix Marseille Université, CNRS, CINaM UMR 7325, 13288 Marseille (France)

2014-02-10

We report that solid state dewetting of Si thin film on SiO{sub 2} can be reversibly inhibited by exposing the Si surface to a partial pressure of dioxygen (∼10{sup −7}Torr) at high temperature (∼1100K). Coupling in situ Low-Energy Electron Microscopy and ex situ atomic force microscopy we propose that the pinning of the contact line induced by the presence of small amounts of silicon oxide is the main physical process that inhibits the dewetting.

Dewetting and Segregation of Zn-Doped InSb in Microgravity Experiments

Science.gov (United States)

Ostrogorsky, A. G.; Marin, C.; Duffar, T.; Volz, M.

2009-01-01

In directional solidification, dewetting is characterized by the lack of contact between the crystal and the crucible walls, due to the existence of a liquid meniscus at the level of the solid-liquid interface. This creates a gap of a few tens of micrometers between the crystal and the crucible. One of the immediate consequences of this phenomenon is the dramatic improvement of the quality of the crystal. This improvement is partly due to the modification of the solid-liquid interface curvature and partly to the absence of sticking and spurious nucleation at the crystal-crucible interface. Dewetting has been, commonly observed during the growth of semiconductors in crucibles under microgravity conditions where it appears to be very stable: the gap between the crystal and the crucible remains constant along several centimetres of growth. The physical models of the phenomenon are well established and they predict that dewetting should not occur in microgravity, if sufficient static pressure is imposed on the melt, pushing it towards the crucible. We present the results of InSb(Zn) solidification experiments conducted at the International Space Station (ISS) where, in spite of a spring exerting a pressure on the liquid, partial dewetting did occur. This surprising result is discussed in terms of force exerted .by the spring on the liquid and of possibility that the spring did not work properly. Furthermore, it appears that the segregation of the Zn was not affected by the occurrence of the dewetting. The data suggest that there was no significant interference of convection with segregation of Zn in InSb.

Mechanically modulated dewetting by atomic force microscope for micro- and nano- droplet array fabrication.

Science.gov (United States)

Wang, Feifei; Li, Pan; Wang, Dong; Li, Longhai; Xie, Shuangxi; Liu, Lianqing; Wang, Yuechao; Li, Wen Jung

2014-10-06

Organizing a material into well-defined patterns during the dewetting process provides an attractive micro-/nano-fabrication method without using a conventional lithographic process, and hence, offers potential applications in organic electronics, optics systems, and memory devices. We report here how the mechanical modification of polymer surface by an Atomic Force Microscope (AFM) can be used to guide thin film dewetting evolution and break the intrinsic spatial correlation of spontaneous instability. An AFM is used to implement the mechanical modification of progressively narrow grids to investigate the influence of pattern size on the modulation of ultrathin polystyrene films dewetting evolution. For films with different initial thicknesses, when grid size is close to or below the characteristic wavelength of instability, the spinodal dewetting is suppressed, and film rupture is restricted to the cutting trench. We will show in this paper it is possible to generate only one droplet per gridded area on a thin film subsequent to nucleation dominated dewetting on a non-patterned substrate. Furthermore, when the grid periodicity exceeds the spinodal length, the number of droplets in predefined areas gradually approaches that associated with unconfined dewetting.

Ordered arrays of Au catalysts by FIB assisted heterogeneous dewetting.

Science.gov (United States)

Benkouider, A; Ronda, A; David, T; Favre, L; Abbarchi, M; Naffouti, M; Osmond, J; Delobbe, A; Sudraud, P; Berbezier, I

2015-12-18

Synthesizing Au0.8Si0.2 nanocatalysts that are homogeneous in size and have controlled position is becoming a challenging and crucial prequisite for the fabrication of ordered semiconductor nanowires. In this study, Au0.8Si0.2 nanocatalysts are synthesized via dewetting of Au layers on Si(111) during thermal annealing in an ultra-high vacuum. In the first part of the paper, the mechanism of homogeneous dewetting is analyzed as a function of the Au-deposited thickness (h Au). We distinguish three different dewetting regimes: (I) for a low thickness ([Formula: see text]), a submonolyer coverage of Au is stabilized and there is no dewetting. (II) For an intermediate thickness ([Formula: see text]), there is both dewetting and Au0.8Si0.2 phase formation. The size and density of the Au0.8Si0.2 clusters are directly related to h Au. When cooling down to room temperature, the clusters decompose and reject the Si at the Au/Si substrate interface. (III) For a large thickness ([Formula: see text]), only dewetting takes place, without forming AuSi clusters. In this regime, the dewetting is kinetically controlled by the self-diffusion of Au (activation energy ∼0.43 eV) without evidence of an Si-alloying effect. As a practical consequence, when relying solely on the homogeneous dewetting of Au/Si(111) to form the Au0.8Si0.2 catalysts (without a supply of Si atoms from vapor), regime II should be used to obtain good size and density control. In the second part of the paper, a process for ordering the catalysts using focused ion beam-(FIB) assisted dewetting (heterogeneous dewetting) is developed. We show that no matter what the FIB milling conditions and the Au nominal thickness are, dewetting is promoted by ion beam irradiation and is accompanied by the formation of Au0.8Si0.2 droplets. The droplets preferentially form on the patterned areas, while in similar annealing conditions, they do not form on the unpatterned areas. This behavior is attributed to the larger Au

Influence of the substrate on the morphological evolution of gold thin films during solid-state dewetting

Energy Technology Data Exchange (ETDEWEB)

Nsimama, Patrick D. [TU Ilmenau, Institute of Materials Engineering and Institute of Micro- and Nanotechnologies MacroNano, Chair Materials for Electrical Engineering and Electronics, 98693 Ilmenau (Germany); Dar Es Salaam Institute of Technology, P.O. Box 2958, Dar Es Salaam (Tanzania, United Republic of); Herz, Andreas; Wang, Dong [TU Ilmenau, Institute of Materials Engineering and Institute of Micro- and Nanotechnologies MacroNano, Chair Materials for Electrical Engineering and Electronics, 98693 Ilmenau (Germany); Schaaf, Peter, E-mail: peter.schaaf@tu-ilmenau.de [TU Ilmenau, Institute of Materials Engineering and Institute of Micro- and Nanotechnologies MacroNano, Chair Materials for Electrical Engineering and Electronics, 98693 Ilmenau (Germany)

2016-12-01

Highlights: • Dewetting of thin gold films is faster on TiO{sub 2} than on SiO{sub 2}. • Dewetting of thin gold films is faster on amorphous TiO{sub 2} than on crystalline TiO{sub 2}. • The kinetics is attributed to the energy of adhesion. • The morphology of thin Au films deposited on TiO{sub 2} substrates is different to those deposited on SiO{sub 2} substrates. • The dewetting activation energy of Au films deposited on crystalline substrates was higher than the activation energy of Au nanofilms deposited on amorphous TiO{sub 2} substrates. - Abstract: The evolution of electron-beam evaporated Au thin films deposited on crystalline TiO{sub 2} (c-TiO{sub 2}) and amorphous TiO{sub 2} (a-TiO{sub 2}) as well as amorphous SiO{sub 2} substrates are investigated. The kinetic of dewetting is clearly dependent on the type of substrate and is faster on TiO{sub 2} substrates than on SiO{sub 2} substrates. This difference can result from the difference in adhesion energy. Furthermore, the kinetic of dewetting is faster on a-TiO{sub 2} than on c-TiO{sub 2}, possibly due to the crystallization of TiO{sub 2} during annealing induced dewetting process. The morphologies of dewetted Au films deposited on crystalline TiO{sub 2} are characterized by branched holes. The XRD patterns of the Au films deposited on TiO{sub 2} substrates constituted peaks from both metallic Au and anatase TiO{sub 2}. The activation energy of Au films deposited on crystalline TiO{sub 2} substrates was higher than that that of the films deposited on amorphous TiO{sub 2} substrates.

Beyond the Young-Laplace model for cluster growth during dewetting of thin films: effective coarsening exponents and the role of long range dewetting interactions.

Science.gov (United States)

Constantinescu, Adi; Golubović, Leonardo; Levandovsky, Artem

2013-09-01

Long range dewetting forces acting across thin films, such as the fundamental van der Waals interactions, may drive the formation of large clusters (tall multilayer islands) and pits, observed in thin films of diverse materials such as polymers, liquid crystals, and metals. In this study we further develop the methodology of the nonequilibrium statistical mechanics of thin films coarsening within continuum interface dynamics model incorporating long range dewetting interactions. The theoretical test bench model considered here is a generalization of the classical Mullins model for the dynamics of solid film surfaces. By analytic arguments and simulations of the model, we study the coarsening growth laws of clusters formed in thin films due to the dewetting interactions. The ultimate cluster growth scaling laws at long times are strongly universal: Short and long range dewetting interactions yield the same coarsening exponents. However, long range dewetting interactions, such as the van der Waals forces, introduce a distinct long lasting early time scaling behavior characterized by a slow growth of the cluster height/lateral size aspect ratio (i.e., a time-dependent Young angle) and by effective coarsening exponents that depend on cluster size. In this study, we develop a theory capable of analytically calculating these effective size-dependent coarsening exponents characterizing the cluster growth in the early time regime. Such a pronounced early time scaling behavior has been indeed seen in experiments; however, its physical origin has remained elusive to this date. Our theory attributes these observed phenomena to ubiquitous long range dewetting interactions acting across thin solid and liquid films. Our results are also applicable to cluster growth in initially very thin fluid films, formed by depositing a few monolayers or by a submonolayer deposition. Under this condition, the dominant coarsening mechanism is diffusive intercluster mass transport while the

Effect of film thickness on morphological evolution in dewetting and crystallization of polystyrene/poly(ε-caprolactone) blend films.

Science.gov (United States)

Ma, Meng; He, Zhoukun; Yang, Jinghui; Chen, Feng; Wang, Ke; Zhang, Qin; Deng, Hua; Fu, Qiang

2011-11-01

In this Article, the morphological evolution in the blend thin film of polystyrene (PS)/poly(ε-caprolactone) (PCL) was investigated via mainly AFM. It was found that an enriched two-layer structure with PS at the upper layer and PCL at the bottom layer was formed during spinning coating. By changing the solution concentration, different kinds of crystal morphologies, such as finger-like, dendritic, and spherulitic-like, could be obtained at the bottom PCL layer. These different initial states led to the morphological evolution processes to be quite different from each other, so the phase separation, dewetting, and crystalline morphology of PS/PCL blend films as a function of time were studied. It was interesting to find that the morphological evolution of PS at the upper layer was largely dependent on the film thickness. For the ultrathin (15 nm) blend film, a liquid-solid/liquid-liquid dewetting-wetting process was observed, forming ribbons that rupture into discrete circular PS islands on voronoi finger-like PCL crystal. For the thick (30 nm) blend film, the liquid-liquid dewetting of the upper PS layer from the underlying adsorbed PCL layer was found, forming interconnected rim structures that rupture into discrete circular PS islands embedded in the single lamellar PCL dendritic crystal due to Rayleigh instability. For the thicker (60 nm) blend film, a two-step liquid-liquid dewetting process with regular holes decorated with dendritic PCL crystal at early annealing stage and small holes decorated with spherulite-like PCL crystal among the early dewetting holes at later annealing stage was observed. The mechanism of this unusual morphological evolution process was discussed on the basis of the entropy effect and annealing-induced phase separation.

Coupling of microphase separation and dewetting in weakly segregated diblock co-polymer ultrathin films.

Science.gov (United States)

Yan, Derong; Huang, Haiying; He, Tianbai; Zhang, Fajun

2011-10-04

We have studied the coupling behavior of microphase separation and autophobic dewetting in weakly segregated poly(ε-caprolactone)-block-poly(L-lactide) (PCL-b-PLLA) diblock co-polymer ultrathin films on carbon-coated mica substrates. At temperatures higher than the melting point of the PLLA block, the co-polymer forms a lamellar structure in bulk with a long period of L ∼ 20 nm, as determined using small-angle X-ray scattering. The relaxation procedure of ultrathin films with an initial film thickness of h = 10 nm during annealing has been followed by atomic force microscopy (AFM). In the experimental temperature range (100-140 °C), the co-polymer dewets to an ultrathin film of itself at about 5 nm because of the strong attraction of both blocks with the substrate. Moreover, the dewetting velocity increases with decreasing annealing temperatures. This novel dewetting kinetics can be explained by a competition effect of the composition fluctuation driven by the microphase separation with the dominated dewetting process during the early stage of the annealing process. While dewetting dominates the relaxation procedure and leads to the rupture of the ultrathin films, the composition fluctuation induced by the microphase separation attempts to stabilize them because of the matching of h to the long period (h ∼ 1/2L). The temperature dependence of these two processes leads to this novel relaxation kinetics of co-polymer thin films. © 2011 American Chemical Society

Pulsed laser dewetting of nickel catalyst for carbon nanofiber growth

International Nuclear Information System (INIS)

Guan, Y F; Pearce, R C; Simpson, M L; Rack, P D; Melechko, A V; Hensley, D K

2008-01-01

We present a pulsed laser dewetting technique that produces single nickel catalyst particles from lithographically patterned disks for subsequent carbon nanofiber growth through plasma enhanced chemical vapor deposition. Unlike the case for standard heat treated Ni catalyst disks, for which multiple nickel particles and consequently multiple carbon nanofibers (CNFs) are observed, single vertically aligned CNFs could be obtained from the laser dewetted catalyst. Different laser dewetting parameters were tested in this study, such as the laser energy density and the laser processing time measured by the total number of laser pulses. Various nickel disk radii and thicknesses were attempted and the resultant number of carbon nanofibers was found to be a function of the initial disk dimension and the number of laser pulses

Satellite hole formation during dewetting: experiment and simulation

International Nuclear Information System (INIS)

Neto, Chiara; Jacobs, Karin; Seemann, Ralf; Blossey, Ralf; Becker, Juergen; Gruen, Guenther

2003-01-01

The dewetting of thin polymer films on solid substrates has been studied extensively in recent years. These films can decay either by nucleation events or by spinodal dewetting, essentially only depending on the interface potential describing the short- and long-range intermolecular interactions between the interfaces and the initial film thickness. Here, we describe experiments and simulations concerned with the decay of polystyrene thin films. The rupture of the film occurs by the formation of a correlated pattern of holes ('satellite holes') along the liquid rims accumulating at the channel borders. The development of this complex film rupture process, which is neither simply spinodal nor nucleation dewetting, can be mimicked precisely by making use of a novel simulation code based on a rigorous mathematical treatment of the thin film equation and on the knowledge of the effective interface potential of the system. The conditions that determine the appearance and the position of the satellite holes around pre-existing holes are discussed

Satellite hole formation during dewetting: experiment and simulation

CERN Document Server

Neto, C; Seemann, R; Blossey, R; Becker, J; Grün, G

2003-01-01

The dewetting of thin polymer films on solid substrates has been studied extensively in recent years. These films can decay either by nucleation events or by spinodal dewetting, essentially only depending on the interface potential describing the short- and long-range intermolecular interactions between the interfaces and the initial film thickness. Here, we describe experiments and simulations concerned with the decay of polystyrene thin films. The rupture of the film occurs by the formation of a correlated pattern of holes ('satellite holes') along the liquid rims accumulating at the channel borders. The development of this complex film rupture process, which is neither simply spinodal nor nucleation dewetting, can be mimicked precisely by making use of a novel simulation code based on a rigorous mathematical treatment of the thin film equation and on the knowledge of the effective interface potential of the system. The conditions that determine the appearance and the position of the satellite holes around ...

Nanoscale Dewetting Transition in Protein Complex Folding

Science.gov (United States)

Hua, Lan; Huang, Xuhui; Liu, Pu; Zhou, Ruhong; Berne, Bruce J.

2011-01-01

In a previous study, a surprising drying transition was observed to take place inside the nanoscale hydrophobic channel in the tetramer of the protein melittin. The goal of this paper is to determine if there are other protein complexes capable of displaying a dewetting transition during their final stage of folding. We searched the entire protein data bank (PDB) for all possible candidates, including protein tetramers, dimers, and two-domain proteins, and then performed the molecular dynamics (MD) simulations on the top candidates identified by a simple hydrophobic scoring function based on aligned hydrophobic surface areas. Our large scale MD simulations found several more proteins, including three tetramers, six dimers, and two two-domain proteins, which display a nanoscale dewetting transition in their final stage of folding. Even though the scoring function alone is not sufficient (i.e., a high score is necessary but not sufficient) in identifying the dewetting candidates, it does provide useful insights into the features of complex interfaces needed for dewetting. All top candidates have two features in common: (1) large aligned (matched) hydrophobic areas between two corresponding surfaces, and (2) large connected hydrophobic areas on the same surface. We have also studied the effect on dewetting of different water models and different treatments of the long-range electrostatic interactions (cutoff vs PME), and found the dewetting phenomena is fairly robust. This work presents a few proteins other than melittin tetramer for further experimental studies of the role of dewetting in the end stages of protein folding. PMID:17608515

Templated assembly of Co-Pt nanoparticles via thermal and laser-induced dewetting of bilayer metal films.

Science.gov (United States)

Oh, Yong-Jun; Kim, Jung-Hwan; Thompson, Carl V; Ross, Caroline A

2013-01-07

Templated dewetting of a Co/Pt metal bilayer film on a topographic substrate was used to assemble arrays of Co-Pt alloy nanoparticles, with highly uniform particle size, shape and notably composition compared to nanoparticles formed on an untemplated substrate. Solid-state and liquid-state dewetting processes, using furnace annealing and laser irradiation respectively, were compared. Liquid state dewetting produced more uniform, conformal nanoparticles but they had a polycrystalline disordered fcc structure and relatively low magnetic coercivity. In contrast, solid state dewetting enabled formation of magnetically hard, ordered L1(0) Co-Pt single-crystal particles with coercivity >12 kOe. Furnace annealing converted the nanoparticles formed by liquid state dewetting into the L1(0) phase.

Correlated dewetting patterns in thin polystyrene films

CERN Document Server

Neto, C; Seemann, R; Blossey, R; Becker, J; Grün, G

2003-01-01

We describe preliminary results of experiments and simulations concerned with the dewetting of thin polystyrene films (thickness < 7 nm) on top of silicon oxide wafers. In the experiments we scratched an initially flat film with an atomic force microscopy (AFM) tip, producing dry channels in the film. Dewetting of the films was imaged in situ using AFM and a correlated pattern of holes ('satellite holes') was observed along the rims bordering the channels. The development of this complex film rupture process was simulated and the results of experiments and simulations are in good agreement. On the basis of these results, we attempt to explain the appearance of satellite holes and their positions relative to pre-existing holes.

Correlated dewetting patterns in thin polystyrene films

International Nuclear Information System (INIS)

Neto, Chiara; Jacobs, Karin; Seemann, Ralf; Blossey, Ralf; Becker, Juergen; Gruen, Guenther

2003-01-01

We describe preliminary results of experiments and simulations concerned with the dewetting of thin polystyrene films (thickness < 7 nm) on top of silicon oxide wafers. In the experiments we scratched an initially flat film with an atomic force microscopy (AFM) tip, producing dry channels in the film. Dewetting of the films was imaged in situ using AFM and a correlated pattern of holes ('satellite holes') was observed along the rims bordering the channels. The development of this complex film rupture process was simulated and the results of experiments and simulations are in good agreement. On the basis of these results, we attempt to explain the appearance of satellite holes and their positions relative to pre-existing holes

Surface phase separation, dewetting feature size, and crystal morphology in thin films of polystyrene/poly(ε-caprolactone) blend.

Science.gov (United States)

Ma, Meng; He, Zhoukun; Li, Yuhan; Chen, Feng; Wang, Ke; Zhang, Qing; Deng, Hua; Fu, Qiang

2012-12-01

Thin films of polystyrene (PS)/poly(ε-caprolactone) (PCL) blends were prepared by spin-coating and characterized by tapping mode force microscopy (AFM). Effects of the relative concentration of PS in polymer solution on the surface phase separation and dewetting feature size of the blend films were systematically studied. Due to the coupling of phase separation, dewetting, and crystallization of the blend films with the evaporation of solvent during spin-coating, different size of PS islands decorated with various PCL crystal structures including spherulite-like, flat-on individual lamellae, and flat-on dendritic crystal were obtained in the blend films by changing the film composition. The average distance of PS islands was shown to increase with the relative concentration of PS in casting solution. For a given ratio of PS/PCL, the feature size of PS appeared to increase linearly with the square of PS concentration while the PCL concentration only determined the crystal morphology of the blend films with no influence on the upper PS domain features. This is explained in terms of vertical phase separation and spinodal dewetting of the PS rich layer from the underlying PCL rich layer, leading to the upper PS dewetting process and the underlying PCL crystalline process to be mutually independent. Copyright © 2012 Elsevier Inc. All rights reserved.

The influence of polymer architectures on the dewetting behavior of thin polymer films: from linear chains to ring chains.

Science.gov (United States)

Wang, Lina; Xu, Lin; Liu, Binyuan; Shi, Tongfei; Jiang, Shichun; An, Lijia

2017-05-03

The dewetting behavior of ring polystyrene (RPS) film and linear polystyrene (LPS) film on silanized Si substrates with different grafting densities and PDMS substrate was investigated. Results showed that polymer architectures greatly influenced the dewetting behavior of the thin polymer film. On the silanized Si substrate with 69% grafting density, RPS chains exhibited stronger adsorption compared with LPS chains, and as a result the wetting layer formed more easily. For LPS films, with a decreased annealing temperature, the stability of the polymer film changed from non-slip dewetting via apparent slip dewetting to apparently stable. However, for RPS films, the polymer film stability switched from apparent slip dewetting to apparently stable. On the silanized Si substrate with 94% grafting density, the chain adsorption became weaker and the dewetting processes were faster than that on the substrate with 69% grafting density at the same experimental temperature for both the LPS and RPS films. Moreover, on the PDMS substrate, LPS films always showed non-slip dewetting, while the dewetting kinetics of RPS films switched from non-slip dewetting to slip dewetting behaviour. Forming the wetting layer strongly influenced the stability and dewetting behavior of the thin polymer films.

Spinodal Theory: A Common Rupturing Mechanism in Spinodal Dewetting and Surface Directed Phase Separation (Some Technological Aspects: Spatial Correlations and the Significance of Dipole-Quadrupole Interaction in Spinodal Dewetting)

International Nuclear Information System (INIS)

Singh, S.P.; Singh, S.P.

2011-01-01

The emerging structures in spinodal dewetting of thin nano films and spinodal decomposition of binary mixtures are found to be similar with certain differences attributed to the nonlinearities inherent in the wetting forces. This paper deals with the technological aspects of the spinodal processes by giving a brief account of the theory and to correlate the two phenomena termed as spinodal dewetting of thin nano films and surface-directed phase separation. The MC simulation micrographs at early stage of spinodal dewetting of a (linear) polymer film confined between two hard walls (using FENE potential between the beads on same chain and Morse potential between inter and intra chain beads) show similarities with surface-directed phase separation (using metropolis algorithm) in creation of holes. The spinodal dewetting is also criticized on the basis of global minimization of free energy emerging from dipole-quadrupole interactions. A novel molecular scale-driving mechanism coming from asymmetric interface formation in spinodal processes is also proposed. It can be believed that the modeling done with the films under confinement of two walls works as a classical mathematical Ansatz to the dipole-quadrupole interaction coming from quantum origins and giving rise to lateral interactions in the process reflecting a colossal behavior in thin nano films though weak in nature

Spinodal Theory: A Common Rupturing Mechanism in Spinodal Dewetting and Surface Directed Phase Separation (Some Technological Aspects: Spatial Correlations and the Significance of Dipole-Quadrupole Interaction in Spinodal Dewetting

Directory of Open Access Journals (Sweden)

Satya Pal Singh

2011-01-01

Full Text Available The emerging structures in spinodal dewetting of thin nano films and spinodal decomposition of binary mixtures are found to be similar with certain differences attributed to the nonlinearities inherent in the wetting forces. This paper deals with the technological aspects of the spinodal processes by giving a brief account of the theory and to correlate the two phenomena termed as spinodal dewetting of thin nanofilms and surface-directed phase separation. The MC simulation micrographs at early stage of spinodal dewetting of a (linear polymer film confined between two hard walls (using FENE potential between the beads on same chain and Morse potential between inter and intra chain beads show similarities with surface-directed phase separation (using metropolis algorithm in creation of holes. The spinodal dewetting is also criticized on the basis of global minimization of free energy emerging from dipole-quadrupole interactions. A novel molecular scale-driving mechanism coming from asymmetric interface formation in spinodal processes is also proposed. It can be believed that the modeling done with the films under confinement of two walls works as a classical mathematical ansatz to the dipole-quadrupole interaction coming from quantum origins and giving rise to lateral interactions in the process reflecting a colossal behavior in thin nano films though weak in nature.

Templated Solid-State Dewetting of Thin Silicon Films.

Science.gov (United States)

Naffouti, Meher; David, Thomas; Benkouider, Abdelmalek; Favre, Luc; Delobbe, Anne; Ronda, Antoine; Berbezier, Isabelle; Abbarchi, Marco

2016-11-01

Thin film dewetting can be efficiently exploited for the implementation of functionalized surfaces over very large scales. Although the formation of sub-micrometer sized crystals via solid-state dewetting represents a viable method for the fabrication of quantum dots and optical meta-surfaces, there are several limitations related to the intrinsic features of dewetting in a crystalline medium. Disordered spatial organization, size, and shape fluctuations are relevant issues not properly addressed so far. This study reports on the deterministic nucleation and precise positioning of Si- and SiGe-based nanocrystals by templated solid-state dewetting of thin silicon films. The dewetting dynamics is guided by pattern size and shape taking full control over number, size, shape, and relative position of the particles (islands dimensions and relative distances are in the hundreds nm range and fluctuate ≈11% for the volumes and ≈5% for the positioning). © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ordered alternating binary polymer nanodroplet array by sequential spin dewetting.

Science.gov (United States)

Bhandaru, Nandini; Das, Anuja; Salunke, Namrata; Mukherjee, Rabibrata

2014-12-10

We report a facile technique for fabricating an ordered array of nearly equal-sized mesoscale polymer droplets of two constituent polymers (polystyrene, PS and poly(methyl methacrylate), PMMA) arranged in an alternating manner on a topographically patterned substrate. The self-organized array of binary polymers is realized by sequential spin dewetting. First, a dilute solution of PMMA is spin-dewetted on a patterned substrate, resulting in an array of isolated PMMA droplets arranged along the substrate grooves due to self-organization during spin coating itself. The sample is then silanized with octadecyltrichlorosilane (OTS), and subsequently, a dilute solution of PS is spin-coated on to it, which also undergoes spin dewetting. The spin-dewetted PS drops having a size nearly equal to the pre-existing PMMA droplets position themselves between two adjacent PMMA drops under appropriate conditions, forming an alternating binary polymer droplet array. The alternating array formation takes place for a narrow range of solution concentration for both the polymers and depends on the geometry of the substrate. The size of the droplets depends on the extent of confinement, and droplets as small as 100 nm can be obtained by this method, on a suitable template. The findings open up the possibility of creating novel surfaces having ordered multimaterial domains with a potential multifunctional capability.

Dewetting of low-viscosity films at solid/liquid interfaces.

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Péron, Nicolas; Brochard-Wyart, Françoise; Duval, Hervé

2012-11-13

We report new experimental results on the dewetting of a mercury film (A) intercalated between a glass slab and an external nonmiscible liquid phase (B) under conditions of a large equilibrium contact angle. The viscosity of the external phase, ηB, was varied over 7 orders of magnitude. We observe a transition between two regimes of dewetting at a threshold viscosity of η(B)* ≈ (ρ(A)e|S̃|)(1/2), where ρ(A) is the mercury density, e is the film thickness, and |S̃| is the effective spreading coefficient. For η(B) dewetting is constant and ruled by Culick’s law, V ≈ (|S̃|/(ρ(A)e))(1/2). Capillary waves were observed at high dewetting velocities: they are a signature of hydraulic shock. For η(B) > η(B)*, the regime is viscous. The dewetting velocity is constant and scales as V ≈ |S̃|/η(B) in the limit of large η(B). We interpret this regime by a balance between the surface energy released during dewetting and the viscous dissipation in the surrounding liquid.

Retardation the dewetting dynamics of ultrathin polystyrene films using highly branched aromatic molecules as additives

International Nuclear Information System (INIS)

Pangpaiboon, Nampueng; Traiphol, Nisanart; Promarak, Vinich; Traiphol, Rakchart

2013-01-01

This study introduces a new class of materials as a dewetting inhibitor for polystyrene (PS) ultrathin films. Two types of highly branched aromatic (HBA) molecules are added into PS films with thicknesses of 7 nm and 23 nm. Their concentrations range from 0.75 to 5 wt.%. The films are annealed in vacuum oven at elevated temperatures to accelerate dewetting process. Evolution of the film morphologies is followed by utilizing atomic force microscopy and optical microscopy. Contact angle measurements are used to evaluate interfacial interactions in each system. Dewetting area as a function of annealing time and HBA concentration are calculated. We have found that the presence of only 0.5 wt.% HBA can suppress the dewetting dynamics of PS films. Increasing the HBA concentration from 0.5 to 5 wt.% causes systematic decrease of the dewetting rate. In this system, the HBA molecules behave as physical cross-linking points for PS chains, which lead to the improvement of film stability. The efficiency of HBA as a dewetting inhibitor varies with molecular weight of PS while the change of HBA structure hardly affects the dewetting behaviors. - Highlights: • New method for improving stability of polystyrene (PS) thin films • Highly branched aromatic molecules (HBA) are used to suppress the dewetting. • Thermal stability of blended PS/HBA films greatly improves. • The effectiveness of HBA varies with molecular weight of PS. • Important results for designing materials in coating application

Retardation the dewetting dynamics of ultrathin polystyrene films using highly branched aromatic molecules as additives

Energy Technology Data Exchange (ETDEWEB)

Pangpaiboon, Nampueng [Research Unit of Advanced Ceramics, Department of Materials Science, Faculty of Science, Chulalongkorn University, Bangkok 10330 (Thailand); Traiphol, Nisanart, E-mail: Nisanart.T@chula.ac.th [Research Unit of Advanced Ceramics, Department of Materials Science, Faculty of Science, Chulalongkorn University, Bangkok 10330 (Thailand); Promarak, Vinich [School of Chemistry and Center of Excellence for Innovation in Chemistry, Institute of Science, Suranaree University of Technology, Nakhon Ratchasima 30000 (Thailand); Traiphol, Rakchart, E-mail: Rakchartt@nu.ac.th [Laboratory of Advanced Polymers and Nanomaterials, Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Naresuan University, Phitsanulok 65000 (Thailand); NANOTEC-MU Excellence Center on Intelligent Materials and Systems, Faculty of Science, Rama 6 Road, Ratchathewi, Bangkok 10400 (Thailand)

2013-12-02

This study introduces a new class of materials as a dewetting inhibitor for polystyrene (PS) ultrathin films. Two types of highly branched aromatic (HBA) molecules are added into PS films with thicknesses of 7 nm and 23 nm. Their concentrations range from 0.75 to 5 wt.%. The films are annealed in vacuum oven at elevated temperatures to accelerate dewetting process. Evolution of the film morphologies is followed by utilizing atomic force microscopy and optical microscopy. Contact angle measurements are used to evaluate interfacial interactions in each system. Dewetting area as a function of annealing time and HBA concentration are calculated. We have found that the presence of only 0.5 wt.% HBA can suppress the dewetting dynamics of PS films. Increasing the HBA concentration from 0.5 to 5 wt.% causes systematic decrease of the dewetting rate. In this system, the HBA molecules behave as physical cross-linking points for PS chains, which lead to the improvement of film stability. The efficiency of HBA as a dewetting inhibitor varies with molecular weight of PS while the change of HBA structure hardly affects the dewetting behaviors. - Highlights: • New method for improving stability of polystyrene (PS) thin films • Highly branched aromatic molecules (HBA) are used to suppress the dewetting. • Thermal stability of blended PS/HBA films greatly improves. • The effectiveness of HBA varies with molecular weight of PS. • Important results for designing materials in coating application.

Thermodynamics of (Ga, In)-Sb-O-Si and impact on dewetting process

Energy Technology Data Exchange (ETDEWEB)

Sylla, L. [Cyberstar, Echirolles (France); Duffar, T. [SIMaP-EPM, Saint Martin d' Heres (France)

2011-11-15

A thermodynamic study is performed for the systems (Ga or In)-Sb-O-Si in order to better understand the difference observed during dewetting experiments of GaSb and InSb in silica ampoules. Results show that the melts can be considered as non reactive toward silica. When the atmosphere is clean ({<=}1 ppm O{sub 2}), no oxide is formed, while, under oxidising atmosphere, oxides exist above the melting point of the antimonide and are known to increase the wetting angle of the melt on the crucible. However the temperature range for oxide stability is smaller in the case of InSb and this may explain why dewetting is easy for GaSb in presence of oxygen, while it is difficult for InSb. (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Pathways to dewetting in hydrophobic confinement.

Science.gov (United States)

Remsing, Richard C; Xi, Erte; Vembanur, Srivathsan; Sharma, Sumit; Debenedetti, Pablo G; Garde, Shekhar; Patel, Amish J

2015-07-07

Liquid water can become metastable with respect to its vapor in hydrophobic confinement. The resulting dewetting transitions are often impeded by large kinetic barriers. According to macroscopic theory, such barriers arise from the free energy required to nucleate a critical vapor tube that spans the region between two hydrophobic surfaces--tubes with smaller radii collapse, whereas larger ones grow to dry the entire confined region. Using extensive molecular simulations of water between two nanoscopic hydrophobic surfaces, in conjunction with advanced sampling techniques, here we show that for intersurface separations that thermodynamically favor dewetting, the barrier to dewetting does not correspond to the formation of a (classical) critical vapor tube. Instead, it corresponds to an abrupt transition from an isolated cavity adjacent to one of the confining surfaces to a gap-spanning vapor tube that is already larger than the critical vapor tube anticipated by macroscopic theory. Correspondingly, the barrier to dewetting is also smaller than the classical expectation. We show that the peculiar nature of water density fluctuations adjacent to extended hydrophobic surfaces--namely, the enhanced likelihood of observing low-density fluctuations relative to Gaussian statistics--facilitates this nonclassical behavior. By stabilizing isolated cavities relative to vapor tubes, enhanced water density fluctuations thus stabilize novel pathways, which circumvent the classical barriers and offer diminished resistance to dewetting. Our results thus suggest a key role for fluctuations in speeding up the kinetics of numerous phenomena ranging from Cassie-Wenzel transitions on superhydrophobic surfaces, to hydrophobically driven biomolecular folding and assembly.

Suppression of dewetting phenomena during excimer laser melting of thin metal films on SiO2

International Nuclear Information System (INIS)

Kline, J.E.; Leonard, J.P.

2005-01-01

Pulsed excimer laser irradiation has been used to fully melt 200 nm films of elemental Au and Ni on SiO 2 substrates. With the use of a capping layer of SiO 2 and line irradiation via projection optics, the typical liquid-phase dewetting processes associated with these metals on SiO 2 has been suppressed. In a series of experiments varying line widths and fluence, a process region is revealed immediately above the complete melting threshold for which the films remain continuous and smooth after melting and resolidification. Simple energetic arguments for mechanisms leading to initiation of dewetting support these observations, and a gas-mediated model is proposed to describe the process conditions that are necessary for the suppression of dewetting

Repeated Solid-state Dewetting of Thin Gold Films for Nanogap-rich Plasmonic Nanoislands.

Science.gov (United States)

Kang, Minhee; Park, Sang-Gil; Jeong, Ki-Hun

2015-10-15

This work reports a facile wafer-level fabrication for nanogap-rich gold nanoislands for highly sensitive surface enhanced Raman scattering (SERS) by repeating solid-state thermal dewetting of thin gold film. The method provides enlarged gold nanoislands with small gap spacing, which increase the number of electromagnetic hotspots and thus enhance the extinction intensity as well as the tunability for plasmon resonance wavelength. The plasmonic nanoislands from repeated dewetting substantially increase SERS enhancement factor over one order-of-magnitude higher than those from a single-step dewetting process and they allow ultrasensitive SERS detection of a neurotransmitter with extremely low Raman activity. This simple method provides many opportunities for engineering plasmonics for ultrasensitive detection and highly efficient photon collection.

Spatial control of direct chemical vapor deposition of graphene on silicon dioxide by directional copper dewetting

NARCIS (Netherlands)

van den Beld, Wesley Theodorus Eduardus; van den Berg, Albert; Eijkel, Jan C.T.

2016-01-01

In this paper we present a method for the spatial control of direct graphene synthesis onto silicon dioxide by controlled dewetting. The dewetting process is controlled through a combination of using a grooved substrate and conducting copper deposition at an angle. The substrate is then treated

Fabrication of poly-crystalline Si-based Mie resonators via amorphous Si on SiO2 dewetting.

Science.gov (United States)

Naffouti, Meher; David, Thomas; Benkouider, Abdelmalek; Favre, Luc; Ronda, Antoine; Berbezier, Isabelle; Bidault, Sebastien; Bonod, Nicolas; Abbarchi, Marco

2016-02-07

We report the fabrication of Si-based dielectric Mie resonators via a low cost process based on solid-state dewetting of ultra-thin amorphous Si on SiO2. We investigate the dewetting dynamics of a few nanometer sized layers annealed at high temperature to form submicrometric Si-particles. Morphological and structural characterization reveal the polycrystalline nature of the semiconductor matrix as well as rather irregular morphologies of the dewetted islands. Optical dark field imaging and spectroscopy measurements of the single islands reveal pronounced resonant scattering at visible frequencies. The linewidth of the low-order modes can be ∼20 nm in full width at half maximum, leading to a quality factor Q exceeding 25. These values reach the state-of-the-art ones obtained for monocrystalline Mie resonators. The simplicity of the dewetting process and its cost-effectiveness opens the route to exploiting it over large scales for applications in silicon-based photonics.

Grain growth: The key to understand solid-state dewetting of silver thin films

International Nuclear Information System (INIS)

Jacquet, P.; Podor, R.; Ravaux, J.; Teisseire, J.; Gozhyk, I.; Jupille, J.; Lazzari, R.

2016-01-01

The dynamics of solid-state dewetting of polycrystalline silver thin films in oxygen atmosphere was investigated with in situ and real-time environmental Scanning Electron Microscopy at high temperature combined with Atomic Force Microscopy. Three steps were identified during dewetting: induction, hole propagation without specific rim and sintering. Moreover, it was observed that a very selective grain growth, promoted by surface diffusion, plays a key role all along the process.

Confinement induced ordering in dewetting of ultra-thin polymer bilayers on nanopatterned substrates.

Science.gov (United States)

Bhandaru, Nandini; Das, Anuja; Mukherjee, Rabibrata

2016-01-14

We report the dewetting of a thin bilayer of polystyrene (PS) and poly(methylmethacrylate) (PMMA) on a topographically patterned nonwettable substrate comprising an array of pillars, arranged in a square lattice. With a gradual increase in the concentration of the PMMA solution (Cn-PMMA), the morphology of the bottom layer changes to: (1) an aligned array of spin dewetted droplets arranged along substrate grooves at very low Cn-PMMA; (2) an interconnected network of threads surrounding each pillar at intermediate Cn-PMMA; and (3) a continuous bottom layer at higher Cn-PMMA. On the other hand the morphology of the PS top layer depends largely on the nature of the pre-existing bottom layer, in addition to Cn-PS. An ordered array of PMMA core-PS shell droplets forms right after spin coating when both Cn-PMMA and Cn-PS are very low. Bilayers with all other initial configurations evolve during thermal annealing, resulting in a variety of ordered structures. Unique morphologies realized include laterally coexisting structures of the two polymers confined within the substrate grooves due to initial rupture of the bottom layer on the substrate followed by a squeezing flow of the top layer; an array of core-shell and single polymer droplets arranged in an alternating order etc., to highlight a few. Such structures cannot be fabricated by any stand-alone lithography technique. On the other hand, in some cases the partially dewetted bottom layer imparts stability to an intact top PS layer against dewetting. Apart from ordering, under certain specific conditions significant miniaturization and downsizing of dewetted feature periodicity and dimension as compared to dewetting of a single layer on a flat substrate is observed. With the help of a morphology phase diagram we show that ordering is achieved over a wide combination of Cn-PMMA and Cn-PS, though the morphology and dewetting pathway differs significantly with variation in the thickness of the individual layers.

On dewetting dynamics of solid films of hydrogen isotopes and its influence on tritium β spectroscopy

International Nuclear Information System (INIS)

Fleischmann, L.; Bonn, J.; Bornschein, B.; Otten, E.W.; Przyrembel, M.; Weinheimer, Ch.

2000-01-01

The dewetting dynamics of solid films of hydrogen isotopes, quench-condensed on a graphite substrate, was measured at various temperatures below desorption by observing the stray light from the film. A schematic model describing the dewetting process by surface diffusion is presented, which agrees qualitatively with our data. The activation energies of different hydrogen isotopes for surface diffusion were determined. The time constant for dewetting of a quench-condensed T 2 film at the working temperature of 1.86 K of the mainz neutrino mass experiment was extrapolated. (orig.)

Stability and dewetting kinetics of thin gold films on Ti, TiOx and ZnO adhesion layers

International Nuclear Information System (INIS)

Schaefer, Brian T.; Cheung, Jeffrey; Ihlefeld, Jon F.; Jones, Jacob L.; Nagarajan, Valanoor

2013-01-01

We present an in situ high-temperature confocal laser microscopy study on the thermal stability of 40 nm thick gold thin films grown on 40 nm Ti, TiO x and ZnO adhesion layers on (0 0 1) Si. In situ observation of the dewetting process was performed over a wide range of set temperatures (400–800 °C) and ramp rates (10–50 °C min −1 ) for each gold/adhesion layer combination. We found that significant dewetting and subsequent formation of gold islands occurs only at and above 700 °C for all adhesion layers. The dewetting is driven to equilibrium for gold/ZnO compared to gold/Ti and gold/TiO x as confirmed by ex situ X-ray diffraction and scanning electron microscopy characterization. Quantification of the in situ data through stretched exponential kinetic models reveals an underlying apparent activation energy of the dewetting process. This energy barrier for dewetting is higher for gold/Ti and gold/TiO x compared to gold/ZnO, thus confirming the ex situ observations. We rationalize that these apparent activation energies correspond to the underlying thermal stability of each gold/adhesion layer system

Multiscale Modeling of Dewetting Damage in Highly Filled Particulate Composites

Science.gov (United States)

Geubelle, P. H.; Inglis, H. M.; Kramer, J. D.; Patel, J. J.; Kumar, N. C.; Tan, H.

2008-02-01

Particle debonding or dewetting constitutes one of the key damage processes in highly filled particulate composites such as solid propellant and other energetic materials. To analyze this failure process, we have developed a multiscale finite element framework that combines, at the microscale, a nonlinear description of the binder response with a cohesive model of the damage process taking place in a representative periodic unit cell (PUC). To relate micro-scale damage to the macroscopic constitutive response of the material, we employ the mathematical theory of homogenization (MTH). After a description of the numerical scheme, we present the results of the damage response of a highly filled particulate composite subjected to a uniaxial macroscopic strain, and show the direct correlation between the complex damage processes taking place in the PUC and the nonlinear macroscopic constitutive response. We also present a detailed study of the PUC size and a comparison between the finite element MTH-based study and a micromechanics model of the dewetting process.

A study on the correlation between the dewetting temperature of Ag film and SERS intensity.

Science.gov (United States)

Quan, Jiamin; Zhang, Jie; Qi, Xueqiang; Li, Junying; Wang, Ning; Zhu, Yong

2017-11-07

The thermally dewetted metal nano-islands have been actively investigated as cost-effective SERS-active substrates with a large area, good reproducibility and repeatability via simple fabrication process. However, the correlation between the dewetting temperature of metal film and SERS intensity hasn't been systematically studied. In this work, taking Ag nano-islands (AgNIs) as an example, we reported a strategy to investigate the correlation between the dewetting temperature of metal film and SERS intensity. We described the morphology evolution of AgNIs on the SiO 2 planar substrate in different temperatures and got the quantitative information in surface-limited diffusion process (SLDP) as a function of annealing temperature via classical mean-field nucleation theory. Those functions were further used in the simulation of electromagnetic field to obtain the correlation between the dewetting temperature of Ag film and theoretical analysis. In addition, Raman mapping was done on samples annealed at different temperatures, with R6G as an analyte, to accomplish the analysis of the correlation between the dewetting temperature of Ag film and SERS intensity, which is consistent with the theoretical analysis. For SLDP, we used the morphological characterization of five samples prepared by different annealing temperatures to successfully illustrate the change in SERS intensity with the temperature fluctuation, obtaining a small deviation between the experimental results and theoretic prediction.

Accelerating dewetting on deformable substrates by adding a liquid underlayer.

Science.gov (United States)

Xu, Lin; Reiter, Günter; Shi, Tongfei; An, Lijia

2010-05-18

We investigated the dependence of the dewetting velocity of a thin, low-viscosity polystyrene (PS) top film on a poly(methyl methacrylate) (PMMA) double layer consisting of a low-viscosity underlayer of thickness h(L) coated with a high-viscosity middle layer of thickness h(M). The addition of the liquid underlayer generated complex nonmonotonic behavior of the dewetting velocity as a function of increasing h(M). In particular, we observed an acceleration of dewetting for an intermediate range of h(M). This phenomenon has been interpreted by a combination deformation of the middle elastic layer and a concurrent change in the contact angle. On one hand, deformation led to the formation of a trench that dissipated energy during its movement through the liquid underlayer and thus caused a slowing down of dewetting. However, with an increase in the thickness of the elastic middle layer, the size of the trench decreased and its influence on the dewetting velocity also decreased. On the other hand, the deformation of the elastic layer also led to an increase in the contact angle. This increase in the driving capillary forces caused an increase in the dewetting velocity.

Pattern formation by dewetting and evaporating sedimenting suspensions

NARCIS (Netherlands)

Habibi, M.; Moller, P.; Fall, A.; Rafaï, S.; Bonn, D.

2012-01-01

Pattern formation from drying droplets containing sedimenting particles and dewetting of thin films of such suspensions was studied. The dewetting causes the formation of finger-like patterns near the contact line which leave behind a deposit of branches. We find that the strikingly low speed of

Wetting-dewetting films: the role of structural forces.

Science.gov (United States)

Nikolov, Alex; Wasan, Darsh

2014-04-01

The liquid wetting and dewetting of solids are ubiquitous phenomena that occur in everyday life. Understanding the nature of these phenomena is beneficial for research and technological applications. However, despite their importance, the phenomena are still not well understood because of the nature of the substrate's surface energy non-ideality and dynamics. This paper illustrates the mechanisms and applications of liquid wetting and dewetting on hydrophilic and hydrophobic substrates. We discuss the classical understanding and application of wetting and film stability criteria based on the Frumkin-Derjaguin disjoining pressure model. The roles of the film critical thickness and capillary pressure on the film instability based on the disjoining pressure isotherm are elucidated, as are the criteria for stable and unstable wet films. We consider the film area in the model for the film stability and the applicable experiments. This paper also addresses the two classic film instability mechanisms for suspended liquid films based on the conditions of the free energy criteria originally proposed by de Vries (nucleation hole formation) and Vrij-Scheludko (capillary waves vs. van der Waals forces) that were later adapted to explain dewetting. We include a discussion of the mechanisms of nanofilm wetting and dewetting on a solid substrate based on nanoparticles' tendency to form a 2D layer and 2D inlayer in the film under the wetting film's surface confinement. We also present our view on the future of wetting-dewetting modeling and its applications in developing emerging technologies. We believe the review and analysis presented here will benefit the current and future understanding of the wetting-dewetting phenomena, as well as aid in the development of novel products and technologies. © 2013.

Self-ordering of small-diameter metal nanoparticles by dewetting on hexagonal mesh templates.

Science.gov (United States)

Meshot, Eric R; Zhao, Zhouzhou; Lu, Wei; Hart, A John

2014-09-07

Arrays of small-diameter nanoparticles with high spatial order are useful for chemical and biological sensors, data storage, synthesis of nanowires and nanotubes, and many other applications. We show that self-ordered metal nanoparticle arrays can be formed by dewetting of thin films on hexagonal mesh substrates made of anodic aluminum oxide (AAO). Upon heating, the metal (Fe) film dewets onto the interstitial sites (i.e., the node points) between pores on the top surface of the AAO. We investigated the particle morphology and dynamics of dewetting using a combination of atomic force microscopy (AFM), grazing-incidence small-angle X-ray scattering (GISAXS), and numerical simulations. Templated metal particles are more monodisperse and have higher local order than those formed by the same dewetting process on flat, nonporous alumina. The degree of order depends on the initial film thickness, and for the optimal thickness tested (nominally 2 nm), we achieved uniform coverage and high order of the particles, comparable to that of the AAO template itself. Computational modeling of dewetting on templates with various pore order and size shows that the order of AAO pores is primarily influential in determining particle position and spacing, while the variance in pore size is less impactful. Potential uses of these ordered nanoparticle arrays on porous materials include plasmonic sensors and spatially controlled catalysts.

In situ investigation of ion-induced dewetting of a thin iron-oxide film on silicon by high resolution scanning electron microscopy

Energy Technology Data Exchange (ETDEWEB)

Amirthapandian, S. [Institut fuer Halbleiteroptik und Funktionelle Grenzflaechen, Universitaet Stuttgart, 70569 Stuttgart (Germany); Material Physics Division, Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India); Schuchart, F.; Garmatter, D.; Bolse, W. [Institut fuer Halbleiteroptik und Funktionelle Grenzflaechen, Universitaet Stuttgart, 70569 Stuttgart (Germany)

2012-11-15

Using our new in situ high resolution scanning electron microscope, which is integrated into the UNILAC ion beamline at the Helmholtzzentrum fuer Schwerionenforschung (GSI) in Darmstadt, Germany, we investigated the swift heavy ion induced dewetting of a thin iron oxide layer on Si. Besides heterogeneous hole nucleation at defects and spontaneous (homogeneous) hole nucleation, we could clearly identify a dewetting mechanism, which is similar to the spinodal dewetting observed for liquid films. Instead of being due to capillary waves, it is based on a stress induced surface instability. The latter results in the formation of a wavy surface with constant dominant wave-length and increasing amplitude during ion irradiation. Dewetting sets in as soon as the wave-troughs reach the film-substrate interface. Inspection of the hole radii and rim shapes indicates that removal of the material from the hole area occurs mainly by plastic deformation at the inner boundary and ion induced viscous flow in the peripheral zone due to surface tension.

Effects of copolymer composition, film thickness, and solvent vapor annealing time on dewetting of ultrathin block copolymer films.

Science.gov (United States)

Huang, Changchun; Wen, Gangyao; Li, Jingdan; Wu, Tao; Wang, Lina; Xue, Feifei; Li, Hongfei; Shi, Tongfei

2016-09-15

Effects of copolymer composition, film thickness, and solvent vapor annealing time on dewetting of spin-coated polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) films (dewetting of the films with different thicknesses occur via the spinodal dewetting and the nucleation and growth mechanisms, respectively. The PS-b-PMMA films rupture into droplets which first coalesce into large ones to reduce the surface free energy. Then the large droplets rupture into small ones to increase the contact area between PMMA blocks and acetone molecules resulting from ultimate migration of PMMA blocks to droplet surface, which is a novel dewetting process observed in spin-coated films for the first time. Copyright © 2016 Elsevier Inc. All rights reserved.

130 MeV Au ion irradiation induced dewetting on In2Te3 thin film

International Nuclear Information System (INIS)

Matheswaran, P.; Abhirami, K.M.; Gokul, B.; Sathyamoorthy, R.; Prakash, Jai; Asokan, K.; Kanjilal, D.

2012-01-01

Highlights: ► In 2 Te 3 phase formed from In/Te bilayer by 130 MeV Au ion irradiation. ► Lower fluence results mixed phases with initial state of dewetting. ► At higher fluence, In 2 Te 3 phase with complete dewetting pattern is formed. ► Thermal spike model is used to explain the inter face mixing phenomena. ► SHI irradiation may be used to functionalize the structural and surface properties of thin films. - Abstract: In/Te bilayer thin films were prepared by sequential thermal evaporation and subsequently irradiated by 130 MeV Au ions. The pristine and irradiated samples were characterized by X-ray diffraction (XRD), Rutherford backscattering spectrometry (RBS), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) techniques. RBS spectra reveal the sputtering of Te film and interface mixing, with increasing fluence. The surface morphology showed the beginning of dewetting of Te thin film and formation of the partially connected with the mixed zones at the fluence of 1 × 10 13 ions/cm 2 . At the higher fluence of 3 × 10 13 ions/cm 2 , dewetted structures were isolated at the surface. Above results are explained based on the formation of craters, sputtering and dewetting followed by inter-diffusion at the interface of molten zones due to thermal spike induced by Au ions.

Dewetting-Induced Photoluminescent Enhancement of Poly(lauryl methacrylate)/Quantum Dot Thin Films.

Science.gov (United States)

Geldmeier, Jeffrey; Rile, Lexy; Yoon, Young Jun; Jung, Jaehan; Lin, Zhiqun; Tsukruk, Vladimir V

2017-12-19

A new method for enhancing photoluminescence from quantum dot (QD)/polymer nanocomposite films is proposed. Poly(lauryl methacrylate) (PLMA) thin films containing embedded QDs are intentionally allowed to undergo dewetting on substrates by exposure to a nonsolvent vapor. After controlled dewetting, films exhibited typical dewetting morphologies with increased amounts of scattering that served to outcouple photoluminescence from the film and reduce internal light propagation within the film. Up to a 5-fold enhancement of the film emission was achieved depending on material factors such as the initial film thickness and QD concentration within the film. An increase in initial film thickness was shown to increase the dewetted maximum feature size and its characteristic length until a critical thickness was reached where dewetting became inhibited. A unique light exposure-based photopatterning method is also presented for the creation of high contrast emissive patterns as guided by spatially controlled dewetting.

Modelling approaches to the dewetting of evaporating thin films of nanoparticle suspensions

International Nuclear Information System (INIS)

Thiele, U; Vancea, I; Archer, A J; Robbins, M J; Frastia, L; Stannard, A; Pauliac-Vaujour, E; Martin, C P; Blunt, M O; Moriarty, P J

2009-01-01

We review recent experiments on dewetting thin films of evaporating colloidal nanoparticle suspensions (nanofluids) and discuss several theoretical approaches to describe the ongoing processes including coupled transport and phase changes. These approaches range from microscopic discrete stochastic theories to mesoscopic continuous deterministic descriptions. In particular, we describe (i) a microscopic kinetic Monte Carlo model, (ii) a dynamical density functional theory and (iii) a hydrodynamic thin film model. Models (i) and (ii) are employed to discuss the formation of polygonal networks, spinodal and branched structures resulting from the dewetting of an ultrathin 'postcursor film' that remains behind a mesoscopic dewetting front. We highlight, in particular, the presence of a transverse instability in the evaporative dewetting front, which results in highly branched fingering structures. The subtle interplay of decomposition in the film and contact line motion is discussed. Finally, we discuss a simple thin film model (iii) of the hydrodynamics on the mesoscale. We employ coupled evolution equations for the film thickness profile and mean particle concentration. The model is used to discuss the self-pinning and depinning of a contact line related to the 'coffee-stain' effect. In the course of the review we discuss the advantages and limitations of the different theories, as well as possible future developments and extensions.

Self-Assembly of Organic Ferroelectrics by Evaporative Dewetting: A Case of β-Glycine.

Science.gov (United States)

Seyedhosseini, Ensieh; Romanyuk, Konstantin; Vasileva, Daria; Vasilev, Semen; Nuraeva, Alla; Zelenovskiy, Pavel; Ivanov, Maxim; Morozovska, Anna N; Shur, Vladimir Ya; Lu, Haidong; Gruverman, Alexei; Kholkin, Andrei L

2017-06-14

Self-assembly of ferroelectric materials attracts significant interest because it offers a promising fabrication route to novel structures useful for microelectronic devices such as nonvolatile memories, integrated sensors/actuators, or energy harvesters. In this work, we demonstrate a novel approach for self-assembly of organic ferroelectrics (as exemplified by ferroelectric β-glycine) using evaporative dewetting, which allows forming quasi-regular arrays of nano- and microislands with preferred orientation of polarization axes. Surprisingly, self-assembled islands are crystallographically oriented in a radial direction from the center of organic "grains" formed during dewetting process. The kinetics of dewetting process follows the t -1/2 law, which is responsible for the observed polygon shape of the grain boundaries and island coverage as a function of radial position. The polarization in ferroelectric islands of β-glycine is parallel to the substrate and switchable under a relatively small dc voltage applied by the conducting tip of piezoresponse force microscope. Significant size effect on polarization is observed and explained within the Landau-Ginzburg-Devonshire phenomenological formalism.

Morphological evolution in dewetting polystyrene/polyhedral oligomeric silsesquioxane thin film bilayers.

Science.gov (United States)

Paul, Rituparna; Karabiyik, Ufuk; Swift, Michael C; Hottle, John R; Esker, Alan R

2008-05-06

Morphological evolution in dewetting thin film bilayers of polystyrene (PS) and a polyhedral oligomeric silsesquioxane (POSS), trisilanolphenyl-POSS (TPP), was studied as a function of annealing temperature and annealing time. The results demonstrate unique dewetting morphologies in PS/TPP bilayers at elevated temperatures that are significantly different from those typically observed in dewetting polymer/polymer bilayers. During temperature ramp studies by optical microscopy (OM) in the reflection mode, PS/TPP bilayers form cracks with a weak optical contrast at approximately 130 degrees C. The crack formation is attributed to tensile stresses within the upper TPP layer. The weak optical contrast of the cracks observed in the bilayers for annealing temperatures below approximately 160 degrees C is consistent with the cracking and dewetting of only the upper TPP layer from the underlying PS layer. The optical contrast of the morphological features is significantly enhanced at annealing temperatures of >160 degrees C. This observation suggests dewetting of both the upper TPP and the lower PS layers that results in the exposure of the silicon substrate. Upon annealing the PS/TPP bilayers at 200 degrees C in a temperature jump experiment, the upper TPP layer undergoes instantaneous cracking as observed by OM. These cracks in the upper TPP layer serve as nucleation sites for rapid dewetting and aggregation of the TPP layer, as revealed by OM and atomic force microscopy (AFM). X-ray photoelectron spectroscopy (XPS) results indicated that dewetting of the lower PS layer ensued for annealing times >5 min and progressed up to 90 min. For annealing times >90 min, OM, AFM, and XPS results revealed complete dewetting of both the layers with the formation of TPP encapsulated PS droplets.

Observation and optical implications of oil dewetting patterns in electrowetting displays

International Nuclear Information System (INIS)

Sun Bo; Heikenfeld, Jason

2008-01-01

Growth of surface instabilities leading to periodic oil patterns in electrowetting display pixels has been experimentally observed. In the electrowetting display pixels, an electrical potential ranging between 0 V and 80 V is applied among a water electrode, dielectric layers consisting of an oil film, fluoropolymer, Parylene C and a lower electrode. As predicted by spinodal dewetting theory, application of electromechanical pressure to the oil film causes the film to dewet into a periodic arrangement of oil droplets. The separation distance, or wavelength, for the dewetted oil droplets decreases with increasing voltage or with decreasing oil film thickness. Various test voltages of 20–80 V and oil thicknesses values of 3.3–8.9 µm were shown to experimentally generate dewetting wavelengths ranging from 10's to 100's of µm. An increased number of oil droplets inside the display pixel decreases the maximum display transmission or reflection proportional to the cube root of the number of droplets. This work therefore provides a means to further understand oil film dewetting in electrowetting display pixels and explains the implications of the dewetting pattern on display optical performance

Polymer underlayer assisted dewetting of a top metal nanofilm

International Nuclear Information System (INIS)

Abeysinghe, Don C; Chen Weibin; Zhan Qiwen; Nelson, Robert E

2009-01-01

We demonstrated polymethylmethacrylate (PMMA) polymer underlayer assisted, focused-ion-beam (FIB)-induced dewetting of a top Au nanofilm where we found that the underlayer played a prominent and, in some cases, a useful role in the dewetting of the top layer. For an Au nanofilm deposited on a thick uniform PMMA underlayer, where the underlayer is stable and therefore does not dewet, irregularly spaced Au nanoparticles (AuNPs) were formed as expected by raster-scanning of a focused Ga-ion beam. On the other hand, topographically pre-patterned thin PMMA film provided heterogeneous nucleation sites for both the Au top layer and the PMMA underlayer to initiate dewetting at and guidance for forming regularly spaced AuNPs with much narrower size distribution at significantly lower ion dose levels when compared to the thick, uniform underlayer case. We also found that the underlayer assisted dewetting in this case relaxes the restriction on pre-pattern periodicity to obtain a single NP per pattern period, which is a noteworthy departure from the pre-patterned solid substrate case. FIB-induced AuNP areas can have sharp boundaries and can be positioned on a selected area of a substrate with high positional accuracy, which is important for the implementation of devices in sensing, nano-optics/photonics, and optoelectronic applications.

Method of drying passivated micromachines by dewetting from a liquid-based process

Science.gov (United States)

Houston, Michael R.; Howe, Roger T.; Maboudian, Roya; Srinivasan, Uthara

2000-01-01

A method of fabricating a micromachine includes the step of constructing a low surface energy film on the micromachine. The micromachine is then rinsed with a rinse liquid that has a high surface energy, relative to the low surface energy film, to produce a contact angle of greater than 90.degree. between the low surface energy film and the rinse liquid. This relatively large contact angle causes any rinse liquid on the micromachine to be displaced from the micromachine when the micromachine is removed from the rinse liquid. In other words, the micromachine is dried by dewetting from a liquid-based process. Thus, a separate evaporative drying step is not required, as the micromachine is removed from the liquid-based process in a dry state. The relatively large contact angle also operates to prevent attractive capillary forces between micromachine components, thereby preventing contact and adhesion between adjacent microstructure surfaces. The low surface energy film may be constructed with a fluorinated self-assembled monolayer film. The processing of the invention avoids the use of environmentally harmful, health-hazardous chemicals.

Complex dewetting scenarios of ultrathin silicon films for large-scale nanoarchitectures.

Science.gov (United States)

Naffouti, Meher; Backofen, Rainer; Salvalaglio, Marco; Bottein, Thomas; Lodari, Mario; Voigt, Axel; David, Thomas; Benkouider, Abdelmalek; Fraj, Ibtissem; Favre, Luc; Ronda, Antoine; Berbezier, Isabelle; Grosso, David; Abbarchi, Marco; Bollani, Monica

2017-11-01

Dewetting is a ubiquitous phenomenon in nature; many different thin films of organic and inorganic substances (such as liquids, polymers, metals, and semiconductors) share this shape instability driven by surface tension and mass transport. Via templated solid-state dewetting, we frame complex nanoarchitectures of monocrystalline silicon on insulator with unprecedented precision and reproducibility over large scales. Phase-field simulations reveal the dominant role of surface diffusion as a driving force for dewetting and provide a predictive tool to further engineer this hybrid top-down/bottom-up self-assembly method. Our results demonstrate that patches of thin monocrystalline films of metals and semiconductors share the same dewetting dynamics. We also prove the potential of our method by fabricating nanotransfer molding of metal oxide xerogels on silicon and glass substrates. This method allows the novel possibility of transferring these Si-based patterns on different materials, which do not usually undergo dewetting, offering great potential also for microfluidic or sensing applications.

Texture evolution and microstructural changes during solid-state dewetting: A correlative study by complementary in situ TEM techniques

International Nuclear Information System (INIS)

Niekiel, Florian; Kraschewski, Simon M.; Schweizer, Peter; Butz, Benjamin; Spiecker, Erdmann

2016-01-01

The transition of a thin film into an energetically favorable set of particles at temperatures below the melting point of the bulk material is known as solid-state dewetting. In this work the dewetting behavior of 16 nm thick discontinuous Au thin films on amorphous silicon nitride membranes is quantitatively studied by complementary in situ transmission electron microscopy techniques taking advantage of the unique capabilities of a chip-based heating system. The combination of dedicated imaging and diffraction techniques is used to investigate the interplay of grain growth and texture evolution with the process of dewetting. The results show an initial coarsening of the microstructure preceding the other processes. Texture evolution is highly correlated to material retraction and agglomeration during the following dewetting process. In-plane grain rotation has been observed, acting as an additional mechanism for orientation changes. From a methodological perspective this work demonstrates the capabilities of today’s transmission electron microscopy in combination with state-of-the-art in situ instrumentation. In particular the combination of complementary information from different dedicated techniques in one and the same setup is demonstrated to be highly beneficial.

Dewetted growth of CdTe in microgravity (STS-95)

International Nuclear Information System (INIS)

Fiederle, M.; Babentsov, V.; Benz, K.W.; Duffar, T.; Dusserre, P.; Corregidor, V.; Dieguez, E.; Delaye, P.; Roosen, G.; Chevrier, V.; Launay, J.C.

2004-01-01

Two CdTe crystals had been grown in microgravity during the STS-95 mission. The growth configuration was dedicated to obtain dewetting of the crystals and to achieve high quality material. Background for the performed experiments was based on the theory of the dewetting and previous experience. The after flight characterization of the crystals has demonstrated existence of the dewetting areas of the crystals and their improved quality regarding the earth grown reference sample. The samples had been characterized by EDAX, Synchrotron X-ray topography, Photoluminescence and Optical and IR microscopy. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Assembly of metallic nanoparticle arrays on glass via nanoimprinting and thin-film dewetting

Directory of Open Access Journals (Sweden)

Sun-Kyu Lee

2017-05-01

Full Text Available We propose a nanofabrication process to generate large-area arrays of noble metal nanoparticles on glass substrates via nanoimprinting and dewetting of metallic thin films. Glass templates were made via pattern transfer from a topographic Si mold to an inorganically cross-linked sol–gel (IGSG resist on glass using a two-layer polydimethylsiloxane (PDMS stamp followed by annealing, which turned the imprinted resist into pure silica. The transparent, topographic glass successfully templated the assembly of Au and Ag nanoparticle arrays via thin-film deposition and dewetting at elevated temperatures. The microstructural and mechanical characteristics that developed during the processes were discussed. The results are promising for low-cost mass fabrication of devices for several photonic applications.

Assembly of metallic nanoparticle arrays on glass via nanoimprinting and thin-film dewetting.

Science.gov (United States)

Lee, Sun-Kyu; Hwang, Sori; Kim, Yoon-Kee; Oh, Yong-Jun

2017-01-01

We propose a nanofabrication process to generate large-area arrays of noble metal nanoparticles on glass substrates via nanoimprinting and dewetting of metallic thin films. Glass templates were made via pattern transfer from a topographic Si mold to an inorganically cross-linked sol-gel (IGSG) resist on glass using a two-layer polydimethylsiloxane (PDMS) stamp followed by annealing, which turned the imprinted resist into pure silica. The transparent, topographic glass successfully templated the assembly of Au and Ag nanoparticle arrays via thin-film deposition and dewetting at elevated temperatures. The microstructural and mechanical characteristics that developed during the processes were discussed. The results are promising for low-cost mass fabrication of devices for several photonic applications.

Cellular Dewetting: Opening of Macroapertures in Endothelial Cells

Science.gov (United States)

Gonzalez-Rodriguez, David; Maddugoda, Madhavi P.; Stefani, Caroline; Janel, Sebastien; Lafont, Frank; Cuvelier, Damien; Lemichez, Emmanuel; Brochard-Wyart, Françoise

2012-05-01

Pathogenic bacteria can cross from blood vessels to host tissues by opening transendothelial cell macroapertures (TEMs). To induce TEM opening, bacteria intoxicate endothelial cells with proteins that disrupt the contractile cytoskeletal network. Cell membrane tension is no longer resisted by contractile fibers, leading to the opening of TEMs. Here we model the opening of TEMs as a new form of dewetting. While liquid dewetting is irreversible, we show that cellular dewetting is transient. Our model predicts the minimum radius for hole nucleation, the maximum TEM size, and the dynamics of TEM opening, in good agreement with experimental data. The physical model is then coupled with biological experimental data to reveal that the protein missing in metastasis (MIM) controls the line tension at the rim of the TEM and opposes its opening.

Wafer scale formation of monocrystalline silicon-based Mie resonators via silicon-on-insulator dewetting.

Science.gov (United States)

Abbarchi, Marco; Naffouti, Meher; Vial, Benjamin; Benkouider, Abdelmalek; Lermusiaux, Laurent; Favre, Luc; Ronda, Antoine; Bidault, Sébastien; Berbezier, Isabelle; Bonod, Nicolas

2014-11-25

Subwavelength-sized dielectric Mie resonators have recently emerged as a promising photonic platform, as they combine the advantages of dielectric microstructures and metallic nanoparticles supporting surface plasmon polaritons. Here, we report the capabilities of a dewetting-based process, independent of the sample size, to fabricate Si-based resonators over large scales starting from commercial silicon-on-insulator (SOI) substrates. Spontaneous dewetting is shown to allow the production of monocrystalline Mie-resonators that feature two resonant modes in the visible spectrum, as observed in confocal scattering spectroscopy. Homogeneous scattering responses and improved spatial ordering of the Si-based resonators are observed when dewetting is assisted by electron beam lithography. Finally, exploiting different thermal agglomeration regimes, we highlight the versatility of this technique, which, when assisted by focused ion beam nanopatterning, produces monocrystalline nanocrystals with ad hoc size, position, and organization in complex multimers.

Formation of patterned arrays of Au nanoparticles on SiC surface by template confined dewetting of normal and oblique deposited nanoscale films

Energy Technology Data Exchange (ETDEWEB)

Ruffino, F., E-mail: francesco.ruffino@ct.infn.it; Grimaldi, M.G.

2013-06-01

We report on the formation of patterned arrays of Au nanoparticles (NPs) on 6H SiC surface. To this end, we exploit the thermal-induced dewetting properties of a template confined deposited nanoscale Au film. In this approach, the Au surface pattern order, on the SiC substrate, is established by a template confined deposition using a micrometric template. Then, a dewetting process of the patterned Au film is induced by thermal processes. We compare the results, about the patterns formation, obtained for normal and oblique deposited Au films. We show that the normal and oblique depositions, through the same template, originate different patterns of the Au film. As a consequence of these different starting patterns, after the thermal processes, different patterns for the arrays of NPs originating from the dewetting mechanisms are obtained. For each fixed deposition angle α, the pattern evolution is analyzed, by scanning electron microscopy, as a function of the annealing time at 1173 K (900 °C). From these analyses, quantitative evaluations on the NPs size evolution are drawn. - Highlights: • Micrometric template-confined nanoscale gold films are deposited on silicon carbide. • The dewetting process of template-confined gold films on silicon carbide is studied. • Comparison of dewetting process of normal and oblique deposited gold films is drawn. • Patterned arrays of gold nanoparticles on silicon carbide surface are produced.

Formation of patterned arrays of Au nanoparticles on SiC surface by template confined dewetting of normal and oblique deposited nanoscale films

International Nuclear Information System (INIS)

Ruffino, F.; Grimaldi, M.G.

2013-01-01

We report on the formation of patterned arrays of Au nanoparticles (NPs) on 6H SiC surface. To this end, we exploit the thermal-induced dewetting properties of a template confined deposited nanoscale Au film. In this approach, the Au surface pattern order, on the SiC substrate, is established by a template confined deposition using a micrometric template. Then, a dewetting process of the patterned Au film is induced by thermal processes. We compare the results, about the patterns formation, obtained for normal and oblique deposited Au films. We show that the normal and oblique depositions, through the same template, originate different patterns of the Au film. As a consequence of these different starting patterns, after the thermal processes, different patterns for the arrays of NPs originating from the dewetting mechanisms are obtained. For each fixed deposition angle α, the pattern evolution is analyzed, by scanning electron microscopy, as a function of the annealing time at 1173 K (900 °C). From these analyses, quantitative evaluations on the NPs size evolution are drawn. - Highlights: • Micrometric template-confined nanoscale gold films are deposited on silicon carbide. • The dewetting process of template-confined gold films on silicon carbide is studied. • Comparison of dewetting process of normal and oblique deposited gold films is drawn. • Patterned arrays of gold nanoparticles on silicon carbide surface are produced

Fabrication of three-dimensional ordered nanodot array structures by a thermal dewetting method

International Nuclear Information System (INIS)

Li Zhenxing; Yoshino, Masahiko; Yamanaka, Akinori

2012-01-01

A new fabrication method for three-dimensional nanodot arrays with low cost and high throughput is developed in this paper. In this process, firstly a 2D nanodot array is fabricated by combination of top-down and bottom-up approaches. A nanoplastic forming technique is utilized as the top-down approach to fabricate a groove grid pattern on an Au layer deposited on a substrate, and self-organization by thermal dewetting is employed as the bottom-up approach. On the first-layer nanodot array, SiO 2 is deposited as a spacer layer. Au is then deposited on the spacer layer and thermal dewetting is conducted to fabricate a second-layer nanodot array. The effective parameters influencing dot formation on the second layer, including Au layer thickness and SiO 2 layer thickness, are studied. It is demonstrated that a 3D nanodot array of good vertical alignment is obtained by repeating the SiO 2 deposition, Au deposition and thermal dewetting. The mechanism of the dot agglomeration process is studied based on geometrical models. The effects of the spacer layer thickness and Au layer thickness on the morphology and alignment of the second-layer dots are discussed. (paper)

Film thickness dependence of phase separation and dewetting behaviors in PMMA/SAN blend films.

Science.gov (United States)

You, Jichun; Liao, Yonggui; Men, Yongfeng; Shi, Tongfei; An, Lijia

2010-09-21

Film thickness dependence of complex behaviors coupled by phase separation and dewetting in blend [poly(methyl methacrylate) (PMMA) and poly(styrene-ran-acrylonitrile) (SAN)] films on silicon oxide substrate at 175 °C was investigated by grazing incidence ultrasmall-angle X-ray scattering (GIUSAX) and in situ atomic force microscopy (AFM). It was found that the dewetting pathway was under the control of the parameter U(q0)/E, which described the initial amplitude of the surface undulation and original thickness of film, respectively. Furthermore, our results showed that interplay between phase separation and dewetting depended crucially on film thickness. Three mechanisms including dewetting-phase separation/wetting, dewetting/wetting-phase separation, and phase separation/wetting-pseudodewetting were discussed in detail. In conclusion, it is relative rates of phase separation and dewetting that dominate the interplay between them.

Dewetting acrylic polymer films with water/propylene carbonate/surfactant mixtures - implications for cultural heritage conservation.

Science.gov (United States)

Baglioni, M; Montis, C; Brandi, F; Guaragnone, T; Meazzini, I; Baglioni, P; Berti, D

2017-09-13

The removal of hydrophobic polymer films from surfaces is one of the top priorities of modern conservation science. Nanostructured fluids containing water, good solvents for polymers, either immiscible or partially miscible with water, and surfactants have been used in the last decade to achieve controlled removal. The dewetting of the polymer film is often an essential step to achieve efficient removal; however, the role of the surfactant throughout the process is yet to be fully understood. We report on the dewetting of a methacrylate/acrylate copolymer film induced by a ternary mixture of water, propylene carbonate (PC) and C 9-11 E 6 , a nonionic alcohol ethoxylate surfactant. The fluid microstructure was characterised through small angle X-ray scattering and the interactions between the film and water, water/PC and water/PC/C 9-11 E 6 , were monitored through confocal laser-scanning microscopy (CLSM) and analised both from a thermodynamic and a kinetic point of view. The presence of a surfactant is a prerequisite to induce dewetting of μm-thick films at room temperature, but it is not a thermodynamic driver. The amphiphile lowers the interfacial energy between the phases and favors the loss of adhesion of the polymer on glass, decreasing, in turn, the activation energy barrier, which can be overcome by the thermal fluctuations of polymer film stability, initiating the dewetting process.

Dewetting of nickel oxide-films on silicon under swift heavy ion irradiation

International Nuclear Information System (INIS)

Bolse, Thunu; Elsanousi, Ammar; Paulus, Hartmut; Bolse, Wolfgang

2006-01-01

Dewetting, occurring when a thin film on a non-wettable substrate turns into its liquid state, has gained strong interest during the last decade, since it results in nano-scale, large-area covering pattern formation. Recently we found that swift heavy ion (SHI) irradiation of thin NiO films on Si substrates at 80 K results in similar dewetting pattern, although in this case the coating has never reached its melting point. Careful inspection of the SEM images clearly revealed that the same nucleation mechanisms as observed for molten polymer films on Si (heterogeneous and homogeneous nucleation) were active. AFM shows that the circular holes formed in the early stages of the dewetting process exhibit a high and asymmetric rim-structure. RBS analysis was used to measure the coverage of the surface by the oxide films and revealed that the holes grow at constant velocity. This, and the shape of the rims, indicate that the material removed from the substrate surface piles up by plastic deformation, which points at a balance of the capillary driving forces and the hindered material dissipation

Dewetting dynamics of a gold film on graphene: implications for nanoparticle formation.

Science.gov (United States)

Namsani, Sadanandam; Singh, Jayant K

2016-01-01

The dynamics of dewetting of gold films on graphene surfaces is investigated using molecular dynamics simulation. The effect of temperature (973-1533 K), film diameter (30-40 nm) and film thickness (0.5-3 nm) on the dewetting mechanism, leading to the formation of nanoparticles, is reported. The dewetting behavior for films ≤5 Å is in contrast to the behavior seen for thicker films. The retraction velocity, in the order of ∼300 m s(-1) for a 1 nm film, decreases with an increase in film thickness, whereas it increases with temperature. However at no point do nanoparticles detach from the surface within the temperature range considered in this work. We further investigated the self-assembly behavior of nanoparticles on graphene at different temperatures (673-1073 K). The process of self-assembly of gold nanoparticles is favorable at lower temperatures than at higher temperatures, based on the free-energy landscape analysis. Furthermore, the shape of an assembled structure is found to change from spherical to hexagonal, with a marked propensity towards an icosahedral structure based on the bond-orientational order parameters.

Morphology and Pattern Control of Diphenylalanine Self-Assembly via Evaporative Dewetting.

Science.gov (United States)

Chen, Jiarui; Qin, Shuyu; Wu, Xinglong; Chu, And Paul K

2016-01-26

Self-assembled peptide nanostructures have unique physical and biological properties and promising applications in electrical devices and functional molecular recognition. Although solution-based peptide molecules can self-assemble into different morphologies, it is challenging to control the self-assembly process. Herein, controllable self-assembly of diphenylalanine (FF) in an evaporative dewetting solution is reported. The fluid mechanical dimensionless numbers, namely Rayleigh, Marangoni, and capillary numbers, are introduced to control the interaction between the solution and FF molecules in the self-assembly process. The difference in the film thickness reflects the effects of Rayleigh and Marangoni convection, and the water vapor flow rate reveals the role of viscous fingering in the emergence of aligned FF flakes. By employing dewetting, various FF self-assembled patterns, like concentric and spokelike, and morphologies, like strips and hexagonal tubes/rods, can be produced, and there are no significant lattice structural changes in the FF nanostructures.

Polymer Film Dewetting by Water/Surfactant/Good-Solvent Mixtures: A Mechanistic Insight and Its Implications for the Conservation of Cultural Heritage.

Science.gov (United States)

Baglioni, Michele; Montis, Costanza; Chelazzi, David; Giorgi, Rodorico; Berti, Debora; Baglioni, Piero

2018-06-18

Aqueous nanostructured fluids (NSFs) have been proposed to remove polymer coatings from the surface of works of art; this process usually involves film dewetting. The NSF cleaning mechanism was studied using several techniques that were employed to obtain mechanistic insight on the interaction of a methacrylic/acrylic copolymer (Paraloid B72) film laid on glass surfaces and several NSFs, based on two solvents and two surfactants. The experimental results provide a detailed picture of the dewetting process. The gyration radius and the reduction of the T g of Paraloid B72 fully swollen in the two solvents is larger for propylene carbonate than for methyl ethyl ketone, suggesting higher mobility of polymer chains for the former, while a nonionic alcohol ethoxylate surfactant was more effective than sodium dodecylsulfate in favoring the dewetting process. FTIR 2D imaging showed that the dewetting patterns observed on model samples are also present on polymer-coated mortar tiles when exposed to NSFs. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Solid state de-wetting observed for vapor deposited copper films on carbon substrates

International Nuclear Information System (INIS)

Schrank, C.; Eisenmenger-Sittner, C.; Neubauer, E.; Bangert, H.; Bergauer, A.

2004-01-01

Copper-Carbon composites are a good example for novel materials consisting of components with extremely different physical and chemical properties. They have a high potential for an application as heat sinks for electronic components, but the joining of the two materials is a difficult task. To obtain reasonable mechanical and thermal contact between copper and carbon the following route was chosen. First glassy-carbon substrates were subjected to an RF-Nitrogen plasma treatment. Then 300 nm thick copper coatings were sputter-deposited on the plasma treated surface within the same vacuum chamber. Finally, the samples were removed from the deposition chamber and either investigated immediately or thermally annealed at 850 deg. C under high vacuum conditions (10 -4 Pa). While non-annealed copper-coatings were continuous and showed excellent adhesion values of approximately 700 N/cm 2 , the heat treated samples lose their continuity by a de-wetting process. At the beginning holes are formed, then a labyrinth-like morphology develops and finally the coating consists of isolated droplets. All these processes occur well below the melting temperature of copper and were observed by AFM and SEM. The mechanism of this solid-state de-wetting process is investigated in relation to the recent literature on de-wetting and its consequences on the manufacturing of copper-carbon composites are discussed

Dewetting of polymer thin films on modified curved surfaces: preparation of polymer nanoparticles with asymmetric shapes by anodic aluminum oxide templates.

Science.gov (United States)

Liu, Chih-Ting; Tsai, Chia-Chan; Chu, Chien-Wei; Chi, Mu-Huan; Chung, Pei-Yun; Chen, Jiun-Tai

2018-04-18

We study the dewetting behaviors of poly(methyl methacrylate) (PMMA) thin films coated in the cylindrical nanopores of anodic aluminum oxide (AAO) templates by thermal annealing. Self-assembled monolayers (SAMs) of n-octadecyltrichlorosilane (ODTS) are introduced to modify the pore surfaces of the AAO templates to induce the dewetting process. By using scanning electron microscopy (SEM), the dewetting-induced morphology transformation from the PMMA thin films to PMMA nanoparticles with asymmetric shapes can be observed. The sizes of the PMMA nanoparticles can be controlled by the original PMMA solution concentrations. The dewetting phenomena on the modified nanopores are explained by taking into account the excess intermolecular interaction free energy (ΔG). This work opens a new possibility for creating polymer nanoparticles with asymmetric shapes in confined geometries.

130 MeV Au ion irradiation induced dewetting on In{sub 2}Te{sub 3} thin film

Energy Technology Data Exchange (ETDEWEB)

Matheswaran, P.; Abhirami, K.M.; Gokul, B. [Department of Physics, Kongunadu Arts and Science College, Coimbatore 641029 (India); Sathyamoorthy, R., E-mail: rsathya1959@gmail.com [Department of Physics, Kongunadu Arts and Science College, Coimbatore 641029 (India); Prakash, Jai [Department of Chemistry, M.M.H. College, Ghaziabad 201001 (India); Asokan, K.; Kanjilal, D. [Materials Science Division, Inter University Accelerator Centre, New Delhi 110067 (India)

2012-09-01

Highlights: Black-Right-Pointing-Pointer In{sub 2}Te{sub 3} phase formed from In/Te bilayer by 130 MeV Au ion irradiation. Black-Right-Pointing-Pointer Lower fluence results mixed phases with initial state of dewetting. Black-Right-Pointing-Pointer At higher fluence, In{sub 2}Te{sub 3} phase with complete dewetting pattern is formed. Black-Right-Pointing-Pointer Thermal spike model is used to explain the inter face mixing phenomena. Black-Right-Pointing-Pointer SHI irradiation may be used to functionalize the structural and surface properties of thin films. - Abstract: In/Te bilayer thin films were prepared by sequential thermal evaporation and subsequently irradiated by 130 MeV Au ions. The pristine and irradiated samples were characterized by X-ray diffraction (XRD), Rutherford backscattering spectrometry (RBS), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) techniques. RBS spectra reveal the sputtering of Te film and interface mixing, with increasing fluence. The surface morphology showed the beginning of dewetting of Te thin film and formation of the partially connected with the mixed zones at the fluence of 1 Multiplication-Sign 10{sup 13} ions/cm{sup 2}. At the higher fluence of 3 Multiplication-Sign 10{sup 13} ions/cm{sup 2}, dewetted structures were isolated at the surface. Above results are explained based on the formation of craters, sputtering and dewetting followed by inter-diffusion at the interface of molten zones due to thermal spike induced by Au ions.

Thermal dewetting with a chemically heterogeneous nano-template for self-assembled L1(0) FePt nanoparticle arrays.

Science.gov (United States)

Wang, Liang-Wei; Cheng, Chung-Fu; Liao, Jung-Wei; Wang, Chiu-Yen; Wang, Ding-Shuo; Huang, Kuo-Feng; Lin, Tzu-Ying; Ho, Rong-Ming; Chen, Lih-Juann; Lai, Chih-Huang

2016-02-21

A design for the fabrication of metallic nanoparticles is presented by thermal dewetting with a chemically heterogeneous nano-template. For the template, we fabricate a nanostructured polystyrene-b-polydimethylsiloxane (PS-b-PDMS) film on a Si|SiO2 substrate, followed by a thermal annealing and reactive ion etching (RIE) process. This gives a template composed of an ordered hexagonal array of SiOC hemispheres emerging in the polystyrene matrix. After the deposition of a FePt film on this template, we utilize the rapid thermal annealing (RTA) process, which provides in-plane stress, to achieve thermal dewetting and structural ordering of FePt simultaneously. Since the template is composed of different composition surfaces with periodically varied morphologies, it offers more tuning knobs to manipulate the nanostructures. We show that both the decrease in the area of the PS matrix and the increase in the strain energy relaxation transfer the dewetted pattern from the randomly distributed nanoparticles into a hexagonal periodic array of L10 FePt nanoparticles. Transmission electron microscopy with the in situ heating stage reveals the evolution of the dewetting process, and confirms that the positions of nanoparticles are aligned with those of the SiOC hemispheres. The nanoparticles formed by this template-dewetting show an average diameter and center-to-center distance of 19.30 ± 2.09 nm and 39.85 ± 4.80 nm, respectively. The hexagonal array of FePt nanoparticles reveals a large coercivity of 1.5 T, much larger than the nanoparticles fabricated by top-down approaches. This approach offers an efficient pathway toward self-assembled nanostructures in a wide range of material systems.

Thermally induced delay and reversal of liquid film dewetting on chemically patterned surfaces.

Science.gov (United States)

Kalpathy, Sreeram K; Francis, Lorraine F; Kumar, Satish

2013-10-15

A thin liquid film resting on a solid substrate that is heated or cooled from below experiences surface tension gradients, which lead to Marangoni flows. We explore the behavior of such a film on a chemically patterned substrate which drives film dewetting in order to determine how surface patterning and applied temperature gradients can be designed to influence the behavior of thin-film coatings. A nonlinear partial differential equation for the film height based on lubrication theory is solved numerically for a broad range of problem parameters. Uniform cooling of the substrate is found to significantly delay dewetting that is driven by wettability gradients. Uniform heating speeds up dewetting but can destroy the near-perfect templating imposed by the surface patterning. However, localized heating and cooling together can accelerate dewetting while maintaining templating quality. Localized heating and cooling can also be used to drive liquid onto areas that it would dewet from in the absence of heating. Overall, these results indicate that applied temperature gradients can significantly influence dewetting driven by surface patterning, and suggest strategies for the creation of spatially patterned thin-film coatings and flow control in microfluidic devices. Copyright © 2013 Elsevier Inc. All rights reserved.

Robust nanopatterning by laser-induced dewetting of metal nanofilms

International Nuclear Information System (INIS)

Favazza, Christopher; Kalyanaraman, Ramki; Sureshkumar, Radhakrishna

2006-01-01

We have observed nanopattern formation with robust and controllable spatial ordering by laser-induced dewetting in nanoscopic metal films. Pattern evolution in Co film of thickness 1≤h≤8 nm on SiO 2 was achieved under multiple pulse irradiation using a 9 ns pulse laser. Dewetting leads to the formation of cellular patterns which evolve into polygons that eventually break up into nanoparticles with unimodal size distribution and short range ordering in nearest neighbour spacing R. Spatial ordering was attributed to a hydrodynamic thin film instability and resulted in a predictable variation of R and particle diameter D with h. The length scales R and D were found to be independent of the laser energy. These results suggest that spatially ordered metal nanoparticles can be robustly assembled by laser-induced dewetting

Robust nanopatterning by laser-induced dewetting of metal nanofilms

Energy Technology Data Exchange (ETDEWEB)

Favazza, Christopher [Department of Physics, Washington University in St Louis, MO 63130 (United States); Kalyanaraman, Ramki [Department of Physics, Washington University in St Louis, MO 63130 (United States); Sureshkumar, Radhakrishna [Center for Materials Innovation, Washington University in St Louis, MO 63130 (United States)

2006-08-28

We have observed nanopattern formation with robust and controllable spatial ordering by laser-induced dewetting in nanoscopic metal films. Pattern evolution in Co film of thickness 1{<=}h{<=}8 nm on SiO{sub 2} was achieved under multiple pulse irradiation using a 9 ns pulse laser. Dewetting leads to the formation of cellular patterns which evolve into polygons that eventually break up into nanoparticles with unimodal size distribution and short range ordering in nearest neighbour spacing R. Spatial ordering was attributed to a hydrodynamic thin film instability and resulted in a predictable variation of R and particle diameter D with h. The length scales R and D were found to be independent of the laser energy. These results suggest that spatially ordered metal nanoparticles can be robustly assembled by laser-induced dewetting.

Robust nanopatterning by laser-induced dewetting of metal nanofilms.

Science.gov (United States)

Favazza, Christopher; Kalyanaraman, Ramki; Sureshkumar, Radhakrishna

2006-08-28

We have observed nanopattern formation with robust and controllable spatial ordering by laser-induced dewetting in nanoscopic metal films. Pattern evolution in Co film of thickness 1≤h≤8 nm on SiO(2) was achieved under multiple pulse irradiation using a 9 ns pulse laser. Dewetting leads to the formation of cellular patterns which evolve into polygons that eventually break up into nanoparticles with unimodal size distribution and short range ordering in nearest neighbour spacing R. Spatial ordering was attributed to a hydrodynamic thin film instability and resulted in a predictable variation of R and particle diameter D with h. The length scales R and D were found to be independent of the laser energy. These results suggest that spatially ordered metal nanoparticles can be robustly assembled by laser-induced dewetting.

Pathways from disordered to ordered nanostructures from defect guided dewetting of ultrathin bilayers.

Science.gov (United States)

Hens, Abhiram; Mondal, Kartick; Biswas, Gautam; Bandyopadhyay, Dipankar

2016-03-01

Transitions from spinodal to pattern-guided dewetting of a bilayer of ultrathin films (dewetting to generate ordered patterns of nanoscopic size and periodicity. Comparing the results obtained from the MD simulations with the more widely employed continuum dynamics approach highlights the importance of the MD approach in quantitatively analyzing the dynamics of the dewetting of ultrathin films. The study demonstrates that the pattern-guided dewetting of confined bilayers can lead to ordered holes, droplets, and stripes with size and periodicity less than 10nm, which are yet to be realized experimentally and can be of significance for a number of future applications. Copyright © 2015 Elsevier Inc. All rights reserved.

Dewetting and nanopattern formation of thin Pt films on SiO2 induced by ion beam irradiation

International Nuclear Information System (INIS)

Hu, Xiaoyuan; Cahill, David G.; Averback, Robert S.

2001-01-01

Dewetting and nanopattern formation of 3 - 10 nm Pt thin films upon ion irradiation is studied using scanning electron microscopy (SEM). Lateral feature size and the fraction of exposed surface area are extracted from SEM images and analyzed as functions of ion dose. The dewetting phenomenon has little temperature dependence for 3 nm Pt films irradiated by 800 keV Kr + at temperatures ranging from 80 to 823 K. At 893 K, the films dewet without irradiation, and no pattern formation is observed even after irradiation. The thickness of the Pt films, in the range 3 - 10 nm, influences the pattern formation, with the lateral feature size increasing approximately linearly with film thickness. The effect of different ion species and energies on the dewetting process is also investigated using 800 keV Kr + and Ar + irradiation and 19.5keVHe + , Ar + , Kr + , and Xe + irradiation. The lateral feature size and exposed surface fraction scale with energy deposition density (J/cm2) for all conditions except 19.5keVXe + irradiation. [copyright] 2001 American Institute of Physics

High-speed nanoscale characterization of dewetting via dynamic transmission electron microscopy

International Nuclear Information System (INIS)

Hihath, Sahar; Santala, Melissa K.; Campbell, Geoffrey; Benthem, Klaus van

2016-01-01

The dewetting of thin films can occur in either the solid or the liquid state for which different mass transport mechanisms are expected to control morphological changes. Traditionally, dewetting dynamics have been examined on time scales between several seconds to hours, and length scales ranging between nanometers and millimeters. The determination of mass transport mechanisms on the nanoscale, however, requires nanoscale spatial resolution and much shorter time scales. This study reports the high-speed observation of dewetting phenomena for kinetically constrained Ni thin films on crystalline SrTiO_3 substrates. Movie-mode Dynamic Transmission Electron Microscopy (DTEM) was used for high-speed image acquisition during thin film dewetting at different temperatures. DTEM imaging confirmed that the initial stages of film agglomeration include edge retraction, hole formation, and growth. Finite element modeling was used to simulate temperature distributions within the DTEM samples after laser irradiation with different energies. For pulsed laser irradiation at 18 μJ, experimentally observed hole growth suggests that Marangoni flow dominates hole formation in the liquid nickel film. After irradiation with 13.8 μJ, however, the observations suggest that dewetting was initiated by nucleation of voids followed by hole growth through solid-state surface diffusion.

High-speed nanoscale characterization of dewetting via dynamic transmission electron microscopy

Energy Technology Data Exchange (ETDEWEB)

Hihath, Sahar [Department of Materials Science and Engineering, University of California, Davis, 1 Shields Ave., Davis, California 95616 (United States); Department of Physics, University of California, Davis, 1 Shields Ave., Davis, California 95616 (United States); Santala, Melissa K.; Campbell, Geoffrey [Materials Science Division, Lawrence Livermore National Laboratory, 7000 East Ave., Livermore, California 94550 (United States); Benthem, Klaus van, E-mail: benthem@ucdavis.edu [Department of Materials Science and Engineering, University of California, Davis, 1 Shields Ave., Davis, California 95616 (United States)

2016-08-28

The dewetting of thin films can occur in either the solid or the liquid state for which different mass transport mechanisms are expected to control morphological changes. Traditionally, dewetting dynamics have been examined on time scales between several seconds to hours, and length scales ranging between nanometers and millimeters. The determination of mass transport mechanisms on the nanoscale, however, requires nanoscale spatial resolution and much shorter time scales. This study reports the high-speed observation of dewetting phenomena for kinetically constrained Ni thin films on crystalline SrTiO{sub 3} substrates. Movie-mode Dynamic Transmission Electron Microscopy (DTEM) was used for high-speed image acquisition during thin film dewetting at different temperatures. DTEM imaging confirmed that the initial stages of film agglomeration include edge retraction, hole formation, and growth. Finite element modeling was used to simulate temperature distributions within the DTEM samples after laser irradiation with different energies. For pulsed laser irradiation at 18 μJ, experimentally observed hole growth suggests that Marangoni flow dominates hole formation in the liquid nickel film. After irradiation with 13.8 μJ, however, the observations suggest that dewetting was initiated by nucleation of voids followed by hole growth through solid-state surface diffusion.

Dewetting at the edge of a thin NiO-film on Si by swift heavy ion irradiation

International Nuclear Information System (INIS)

Dautel, Knut; Ferhati, Redi; Bolse, Wolfgang

2014-01-01

We have investigated dewetting along a straight edge of a thin NiO-film on a Si-wafer induced by irradiation with 4.8 MeV/u Au-ions at room temperature. Both, the retreat of the edge as well as the opening and growth of circular holes in the film were monitored using our in-situ high resolution scanning electron microscope at the UNILAC accelerator at the Helmholtz Centre for Heavy Ion Research in Darmstadt. The “dewetting kinetics” (dependence of the retreated length and the hole radius on the ion fluence) are compared to previously published results on dewetting of poly-crystalline (Au) and glassy (polymer) films. In the present case the dewetting kinetics compare well with those observed for isothermal dewetting of the highly viscous polymer films, presumed that the role of time in thermally induced dewetting is taken over by the ion fluence in ion induced dewetting. Both, from the dewetting kinetics and the shape of the remaining NiO-traces in the dewetted area in front of the retreating edge, we conclude that the presently observed swift heavy ion induced dewetting occurs by interfacial slipping. It occurs in spatially and timely separated steps in the transiently molten single ion tracks, where the required reduction of the viscosity of NiO is achieved

Dewetting at the edge of a thin NiO-film on Si by swift heavy ion irradiation

Energy Technology Data Exchange (ETDEWEB)

Dautel, Knut; Ferhati, Redi; Bolse, Wolfgang, E-mail: w.bolse@ihfg.uni-stuttgart.de

2014-01-01

We have investigated dewetting along a straight edge of a thin NiO-film on a Si-wafer induced by irradiation with 4.8 MeV/u Au-ions at room temperature. Both, the retreat of the edge as well as the opening and growth of circular holes in the film were monitored using our in-situ high resolution scanning electron microscope at the UNILAC accelerator at the Helmholtz Centre for Heavy Ion Research in Darmstadt. The “dewetting kinetics” (dependence of the retreated length and the hole radius on the ion fluence) are compared to previously published results on dewetting of poly-crystalline (Au) and glassy (polymer) films. In the present case the dewetting kinetics compare well with those observed for isothermal dewetting of the highly viscous polymer films, presumed that the role of time in thermally induced dewetting is taken over by the ion fluence in ion induced dewetting. Both, from the dewetting kinetics and the shape of the remaining NiO-traces in the dewetted area in front of the retreating edge, we conclude that the presently observed swift heavy ion induced dewetting occurs by interfacial slipping. It occurs in spatially and timely separated steps in the transiently molten single ion tracks, where the required reduction of the viscosity of NiO is achieved.

Thickness-dependent spontaneous dewetting morphology of ultrathin Ag films

Energy Technology Data Exchange (ETDEWEB)

Krishna, H; Favazza, C [Department of Physics, Washington University in St Louis, MO 63130 (United States); Sachan, R; Strader, J; Kalyanaraman, R [Department of Material Science and Engineering, University of Tennessee, Knoxville, TN 37996 (United States); Khenner, M, E-mail: ramki@utk.edu [Department of Mathematics, Western Kentucky University, Bowling Green, KY 42101 (United States)

2010-04-16

We show here that the morphological pathway of spontaneous dewetting of ultrathin Ag films on SiO{sub 2} under nanosecond laser melting is dependent on film thickness. For films with thickness h of 2 nm {<=} h {<=} 9.5 nm, the morphology during the intermediate stages of dewetting consisted of bicontinuous structures. For films with 11.5 nm {<=} h {<=} 20 nm, the intermediate stages consisted of regularly sized holes. Measurement of the characteristic length scales for different stages of dewetting as a function of film thickness showed a systematic increase, which is consistent with the spinodal dewetting instability over the entire thickness range investigated. This change in morphology with thickness is consistent with observations made previously for polymer films (Sharma and Khanna 1998 Phys. Rev. Lett. 81 3463-6; Seemann et al 2001 J. Phys.: Condens. Matter 13 4925-38). Based on the behavior of free energy curvature that incorporates intermolecular forces, we have estimated the morphological transition thickness for the intermolecular forces for Ag on SiO{sub 2}. The theory predictions agree well with observations for Ag. These results show that it is possible to form a variety of complex Ag nanomorphologies in a consistent manner, which could be useful in optical applications of Ag surfaces, such as in surface enhanced Raman sensing.

Influences of ultra-thin Ti seed layers on the dewetting phenomenon of Au films deposited on Si oxide substrates

Science.gov (United States)

Kamiko, Masao; Kim, So-Mang; Jeong, Young-Seok; Ha, Jae-Ho; Koo, Sang-Mo; Ha, Jae-Geun

2018-05-01

The influences of a Ti seed layer (1 nm) on the dewetting phenomenon of Au films (5 nm) grown onto amorphous SiO2 substrates have been studied and compared. Atomic force microscopy results indicated that the introduction of Ti between the substrate and Au promoted the dewetting phenomenon. X-ray diffraction measurements suggested that the initial deposition of Ti promoted crystallinity of Au. A series of Auger electron spectroscopy and X-ray photoelectron spectroscopy results revealed that Ti transformed to a Ti oxide layer by reduction of the amorphous SiO2 substrate surface, and that the Ti seed layer remained on the substrate, without going through the dewetting process during annealing. We concluded that the enhancement of Au dewetting and the improvement in crystallinity of Au by the insertion of Ti could be attributed to the fact that Au location was changed from the surface of the amorphous SiO2 substrate to that of the Ti oxide layer.

Dynamic dewetting through micropancake growth

NARCIS (Netherlands)

Seddon, James Richard Thorley; Bliznyuk, O.; Bliznyuk, Olesya; Kooij, Ernst S.; Poelsema, Bene; Zandvliet, Henricus J.W.; Lohse, Detlef

2010-01-01

We experimentally investigate the dynamics of nanometer-high, micrometer-wide gassy layers at the interface between a hydrophobic solid and bulk water. These micropancakes grow laterally in time, on the timescale of an hour, leading to partial dewetting of the solid. The growth is directional,

Controlling the alloy composition of PtNi nanocrystals using solid-state dewetting of bilayer films

Energy Technology Data Exchange (ETDEWEB)

Seo, Okkyun; Oh, Se An; Lee, Ji Yeon; Ha, Sung Soo; Kim, Jae Myung; Choi, Jung Won; Kim, Jin-Woo [Department of Physics and Photon Science & School of Materials Science and Engineering, Gwangju Institute of Science and Technology, Gwangju 61005 (Korea, Republic of); Kang, Hyon Chol [Department of Materials and Science Engineering, Chosun University, Gwangju 61542 (Korea, Republic of); Noh, Do Young, E-mail: dynoh@gist.ac.kr [Department of Physics and Photon Science & School of Materials Science and Engineering, Gwangju Institute of Science and Technology, Gwangju 61005 (Korea, Republic of)

2016-05-15

We demonstrate that solid-state dewetting of bilayer films is an effective way for obtaining bimetallic alloy nanocrystals of controlled composition. When a Pt–Ni bilayer film were annealed near 700 °C, Pt and Ni atoms inter-diffused to form a PtNi bimetallic alloy film. Upon annealing at higher temperatures, the bilayer films transformed into <111> oriented PtNi alloy nanocrystals in small-rhombicuboctahedron shape through solid-state dewetting process. The Pt content of the nanocrystals and the alloy films, estimated by applying the Vegard's law to the relaxed lattice constant, was closely related to the thickness of each layer in the as-grown bilayer films which can be readily controlled during bilayer deposition. - Highlights: • Composition control of PtNi nanoparticles using solid state dewetting is proposed. • PtNi alloy composition was controlled by thickness ratio of Pt–Ni bilayer films. • PtNi alloy nanocrystals were obtained in small-rhombicuboctahedron shape.

Dewetting of Epitaxial Silver Film on Silicon by Thermal Annealing

Science.gov (United States)

Sanders, Charlotte E.; Kellogg, Gary L.; Shih, C.-K.

2013-03-01

It has been shown that noble metals can grow epitaxially on semiconducting and insulating substrates, despite being a non-wetting system: low temperature deposition followed by room temperature annealing leads to atomically flat film morphology. However, the resulting metastable films are vulnerable to dewetting, which has limited their utility for applications under ambient conditions. The physics of this dewetting is of great interest but little explored. We report on an investigation of the dewetting of epitaxial Ag(111) films on Si(111) and (100). Low energy electron microscopy (LEEM) shows intriguing evolution in film morphology and crystallinity, even at temperatures below 100oC. On the basis of these findings, we can begin to draw compelling inferences about film-substrate interaction and the kinetics of dewetting. Financial support is from NSF, DGE-0549417 and DMR-0906025. This work was performed, in part, at the Center for Integrated Nanotechnologies, User Facility operated for the U.S. DOE Office of Science. Sandia National Lab is managed and operated by Sandia Corp., a subsidiary of Lockheed Martin Corp., for the U.S. DOE's National Nuclear Security Administration under DE-AC04-94AL85000.

Promoting effect of ethanol on dewetting transition in the confined region of melittin tetramer

International Nuclear Information System (INIS)

Ren Xiuping; Zhou Bo; Wang Chunlei

2012-01-01

To study the influence of ethanol molecules on the melittin tetramer folding, we investigated the dewetting transition of the melittin tetramer immersed in pure water and 8% aqueous ethanol solution (mass fraction) by the molecular dynamics simulations. We found that the marked dewetting transitions occurred inside a nanoscale channel of the melittin tetramer both in pure water and in aqueous ethanol solution. Also, ethanol molecules promoted this dewetting transition. We attributed this promoting effect to ethanol molecules which prefer to locate at the liquid-vapor interface and decrease the liquid-vapor surface energy. The results provide insight into the effect of ethanol on the water dewetting phenomena. (authors)

Thermal dewetting behavior of polystyrene composite thin films with organic-modified inorganic nanoparticles.

Science.gov (United States)

Kubo, Masaki; Takahashi, Yosuke; Fujii, Takeshi; Liu, Yang; Sugioka, Ken-ichi; Tsukada, Takao; Minami, Kimitaka; Adschiri, Tadafumi

2014-07-29

The thermal dewetting of polystyrene composite thin films with oleic acid-modified CeO2 nanoparticles prepared by the supercritical hydrothermal synthesis method was investigated, varying the nanoparticle concentration (0-30 wt %), film thickness (approximately 50 and 100 nm), and surface energy of silanized silicon substrates on which the composite films were coated. The dewetting behavior of the composite thin films during thermal annealing was observed by an optical microscope. The presence of nanoparticles in the films affected the morphology of dewetting holes, and moreover suppressed the dewetting itself when the concentration was relatively high. It was revealed that there was a critical value of the surface energy of the substrate at which the dewetting occurred. In addition, the spatial distributions of nanoparticles in the composite thin films before thermal annealing were investigated using AFM and TEM. As a result, we found that most of nanoparticles segregated to the surface of the film, and that such distributions of nanoparticles contribute to the stabilization of the films, by calculating the interfacial potential of the films with nanoparticles.

Thickness-dependent spontaneous dewetting morphology of ultrathin Ag films.

Science.gov (United States)

Krishna, H; Sachan, R; Strader, J; Favazza, C; Khenner, M; Kalyanaraman, R

2010-04-16

We show here that the morphological pathway of spontaneous dewetting of ultrathin Ag films on SiO2 under nanosecond laser melting is dependent on film thickness. For films with thickness h of 2 nm < or = h < or = 9.5 nm, the morphology during the intermediate stages of dewetting consisted of bicontinuous structures. For films with 11.5 nm < or = h < or = 20 nm, the intermediate stages consisted of regularly sized holes. Measurement of the characteristic length scales for different stages of dewetting as a function of film thickness showed a systematic increase, which is consistent with the spinodal dewetting instability over the entire thickness range investigated. This change in morphology with thickness is consistent with observations made previously for polymer films (Sharma and Khanna 1998 Phys. Rev. Lett. 81 3463-6; Seemann et al 2001 J. Phys.: Condens. Matter 13 4925-38). Based on the behavior of free energy curvature that incorporates intermolecular forces, we have estimated the morphological transition thickness for the intermolecular forces for Ag on SiO2. The theory predictions agree well with observations for Ag. These results show that it is possible to form a variety of complex Ag nanomorphologies in a consistent manner, which could be useful in optical applications of Ag surfaces, such as in surface enhanced Raman sensing.

Stability and dewetting of metal nanoparticle filled thin polymer films: control of instability length scale and dynamics.

Science.gov (United States)

Mukherjee, Rabibrata; Das, Soma; Das, Anindya; Sharma, Satinder K; Raychaudhuri, Arup K; Sharma, Ashutosh

2010-07-27

We investigate the influence of gold nanoparticle addition on the stability, dewetting, and pattern formation in ultrathin polymer-nanoparticle (NP) composite films by examining the length and time scales of instability, morphology, and dynamics of dewetting. For these 10-50 nm thick (h) polystyrene (PS) thin films containing uncapped gold nanoparticles (diameter approximately 3-4 nm), transitions from complete dewetting to arrested dewetting to absolute stability were observed depending on the concentration of the particles. Experiments show the existence of three distinct stability regimes: regime 1, complete dewetting leading to droplet formation for nanoparticle concentration of 2% (w/w) or below; regime 2, partial dewetting leading to formation of arrested holes for NP concentrations in the range of 3-6%; and regime 3, complete inhibition of dewetting for NP concentrations of 7% and above. Major results are (a) length scale of instability, where lambdaH approximately hn remains unchanged with NP concentration in regime 1 (n approximately 2) but increases in regime 2 with a change in the scaling relation (n approximately 3-3.5); (b) dynamics of instability and dewetting becomes progressively sluggish with an increase in the NP concentration; (c) there are distinct regimes of dewetting velocity at low NP concentrations; (d) force modulation AFM, as well as micro-Raman analysis, shows phase separation and aggregation of the gold nanoparticles within each dewetted polymer droplet leading to the formation of a metal core-polymer shell morphology. The polymer shell could be removed by washing in a selective solvent, thus exposing an array of bare gold nanoparticle aggregates.

Hierarchical Micro/Nano Structures by Combined Self-Organized Dewetting and Photopatterning of Photoresist Thin Films.

Science.gov (United States)

Sachan, Priyanka; Kulkarni, Manish; Sharma, Ashutosh

2015-11-17

Photoresists are the materials of choice for micro/nanopatterning and device fabrication but are rarely used as a self-assembly material. We report for the first time a novel interplay of self-assembly and photolithography for fabrication of hierarchical and ordered micro/nano structures. We create self-organized structures by the intensified dewetting of unstable thin (∼10 nm to 1 μm) photoresist films by annealing them in an optimal solvent and nonsolvent liquid mixture that allows spontaneous dewetting to form micro/nano smooth dome-like structures. The density, size (∼100 nm to millimeters), and curvature/contact angle of the dome/droplet structures are controlled by the film thickness, composition of the dewetting liquid, and time of annealing. Ordered dewetted structures are obtained simply by creating spatial variation of viscosity by ultraviolet exposure or by photopatterning before dewetting. Further, the structures thus fabricated are readily photopatterned again on the finer length scales after dewetting. We illustrate the approach by fabricating several three-dimensional structures of varying complexity with secondary and tertiary features.

A method for the formation of Pt metal nanoparticle arrays using nanosecond pulsed laser dewetting

Energy Technology Data Exchange (ETDEWEB)

Owusu-Ansah, Ebenezer; Horwood, Corie A.; Birss, Viola I.; Shi, Yujun J., E-mail: shiy@ucalgary.ca [Department of Chemistry, University of Calgary, Calgary, Alberta T2N 1N4 (Canada); El-Sayed, Hany A. [Institute for Technical Electrochemistry, Technische Universität München, D-85748 Garching (Germany)

2015-05-18

Nanosecond pulsed laser dewetting of Pt thin films, deposited on a dimpled Ta (DT) surface, has been studied here in order to form ordered Pt nanoparticle (NP) arrays. The DT substrate was fabricated via a simple electrochemical anodization process in a highly concentrated H{sub 2}SO{sub 4} and HF solution. Pt thin films (3–5 nm) were sputter coated on DT and then dewetted under vacuum to generate NPs using a 355 nm laser radiation (6–9 ns, 10 Hz). The threshold laser fluence to fully dewet a 3.5 nm thick Pt film was determined to be 300 mJ/cm{sup 2}. Our experiments have shown that shorter irradiation times (≤60 s) produce smaller nanoparticles with more uniform sizes, while longer times (>60 s) give large nanoparticles with wider size distributions. The optimum laser irradiation time of 1 s (10 pulses) has led to the formation of highly ordered Pt nanoparticle arrays with an average nanoparticle size of 26 ± 3 nm with no substrate deformation. At the optimum condition of 1 s and 500 mJ/cm{sup 2}, as many as 85% of the dewetted NPs were found neatly in the well-defined dimples. This work has demonstrated that pulsed laser dewetting of Pt thin films on a pre-patterned dimpled substrate is an efficient and powerful technique to produce highly ordered Pt nanoparticle arrays. This method can thus be used to produce arrays of other high-melting-point metal nanoparticles for a range of applications, including electrocatalysis, functionalized nanomaterials, and analytical purposes.

Fabrication of metallic nanoparticles by spinodal dewetting of thin films: A high-throughput approach

Energy Technology Data Exchange (ETDEWEB)

Michalak, William D.; Miller, James B. [U.S. Department of Energy, National Energy Technology Laboratory, Pittsburgh, PA 15262 (United States); Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213 (United States); Yolcu, Cem [Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213 (United States); Gellman, Andrew J., E-mail: gellman@cmu.edu [U.S. Department of Energy, National Energy Technology Laboratory, Pittsburgh, PA 15262 (United States); Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213 (United States)

2012-11-01

Metal nanoparticles on structured supports are used in a variety of technological applications including biosensing, energy harvesting, and electronics. In every case, the functions and properties of the metallic nanostructures depend on both their composition and structure (i.e. size, shape, and spatial distribution). Among the challenges to the development of metal nanoparticles for these applications is the characterization of relationships between their structure and their functional properties over multiple structural degrees of freedom spanning a large range of values. In this work, a method for creating a morphological gradient of metal nanoparticles on a substrate is described. The approach, suited for high-throughput fabrication and characterization, is based on spinodal dewetting of a metallic thin film from its substrate. Through control of initial film thickness, anneal temperature, and anneal time, spinodal dewetting results in supported nanoparticles with well-defined and controlled structure. The approach is demonstrated through its application to preparation of Pd nanoparticles on a silicon nitride substrate. The morphologies of the particles were characterized by scanning electron and atomic force microscopies. Free energy-based stability and topological analyses were used to confirm the dewetting mechanism. In addition, the stability theory provides a connection to the thermophysical properties of the resulting nanoparticle array. The dewetting approach is general to any metal/support system and provides an alternative, inexpensive, and robust means to rapidly create metal nanostructures with control of morphology. It shows promise for large scale production of metal nanoparticles structures, as well as understanding basic stability properties of thin metal films. - Highlights: Black-Right-Pointing-Pointer Pd dewetting from SiN occurs by a spinodal dewetting mechanism. Black-Right-Pointing-Pointer Dewetting occurs at temperatures well below the

Fabrication of metallic nanoparticles by spinodal dewetting of thin films: A high-throughput approach

International Nuclear Information System (INIS)

Michalak, William D.; Miller, James B.; Yolcu, Cem; Gellman, Andrew J.

2012-01-01

Metal nanoparticles on structured supports are used in a variety of technological applications including biosensing, energy harvesting, and electronics. In every case, the functions and properties of the metallic nanostructures depend on both their composition and structure (i.e. size, shape, and spatial distribution). Among the challenges to the development of metal nanoparticles for these applications is the characterization of relationships between their structure and their functional properties over multiple structural degrees of freedom spanning a large range of values. In this work, a method for creating a morphological gradient of metal nanoparticles on a substrate is described. The approach, suited for high-throughput fabrication and characterization, is based on spinodal dewetting of a metallic thin film from its substrate. Through control of initial film thickness, anneal temperature, and anneal time, spinodal dewetting results in supported nanoparticles with well-defined and controlled structure. The approach is demonstrated through its application to preparation of Pd nanoparticles on a silicon nitride substrate. The morphologies of the particles were characterized by scanning electron and atomic force microscopies. Free energy-based stability and topological analyses were used to confirm the dewetting mechanism. In addition, the stability theory provides a connection to the thermophysical properties of the resulting nanoparticle array. The dewetting approach is general to any metal/support system and provides an alternative, inexpensive, and robust means to rapidly create metal nanostructures with control of morphology. It shows promise for large scale production of metal nanoparticles structures, as well as understanding basic stability properties of thin metal films. - Highlights: ► Pd dewetting from SiN occurs by a spinodal dewetting mechanism. ► Dewetting occurs at temperatures well below the melting point of Pd. ► Spinodal dewetting allows

Ion induced spinodal dewetting of thin solid films

Energy Technology Data Exchange (ETDEWEB)

Repetto, Luca; Setina Batic, Barbara; Firpo, Giuseppe; Piano, Emanuele; Valbusa, Ugo [Dipartimento di Fisica, Universita di Genova, Via Dodecaneso 33, 16146 Genova (Italy)

2012-05-28

We present experimental data and numerical simulations in order to show that the mechanism of spinodal dewetting is active during ion beam irradiation of thin solid films. The expected scaling law for the characteristic wavelengths versus the initial film thickness is modified by the presence of sputtering. The conclusion is fully supported by model simulation which shows a square law dependence for null sputtering yield and a bimodal trend when sputtering is included. This result is in contrast to earlier studies and opens the possibility to control and use ion induced dewetting for the fabrication of functional nanostructures.

Dewetting Properties of Metallic Liquid Film on Nanopillared Graphene

Science.gov (United States)

Li, Xiongying; He, Yezeng; Wang, Yong; Dong, Jichen; Li, Hui

2014-01-01

In this work, we report simulation evidence that the graphene surface decorated by carbon nanotube pillars shows strong dewettability, which can give it great advantages in dewetting and detaching metallic nanodroplets on the surfaces. Molecular dynamics (MD) simulations show that the ultrathin liquid film first contracts then detaches from the graphene on a time scale of several nanoseconds, as a result of the inertial effect. The detaching velocity is in the order of 10 m/s for the droplet with radii smaller than 50 nm. Moreover, the contracting and detaching behaviors of the liquid film can be effectively controlled by tuning the geometric parameters of the liquid film or pillar. In addition, the temperature effects on the dewetting and detaching of the metallic liquid film are also discussed. Our results show that one can exploit and effectively control the dewetting properties of metallic nanodroplets by decorating the surfaces with nanotube pillars. PMID:24487279

Solvent-vapor-assisted dewetting of prepatterned thin polymer films: control of morphology, order, and pattern miniaturization.

Science.gov (United States)

Bhandaru, Nandini; Goohpattader, Partho Sarathi; Faruqui, Danish; Mukherjee, Rabibrata; Sharma, Ashutosh

2015-03-17

Ultrathin (dewet by the growth of surface instability, the wavelength (λ) of which depends on the film thickness (h(f)). While the dewetting of a flat polymer thin film results in random structures, we show that the dewetting of a prepatterned film results in myriad ordered mesoscale morphologies under specific conditions. Such a film undergoes rupture over the thinnest parts when the initial local thickness of these zones (h(rm)) is lower than a limiting thickness h(lim) ≈ 10 nm. Additionally, the width of the pattern grooves (l(s)) must be wider than λ(s) corresponding to a flat film having a thickness of h(rm) for pattern-directed dewetting to take place over surface-tension-induced flattening. We first present an experimentally obtained morphology phase diagram that captures the conditions where a transition from surface-tension-induced flattening to pattern-directed-rupture takes place. Subsequently, we show the versatility of this technique in achieving a variety of aligned mesopatterns starting from a prepatterned film with simple grating geometry. The morphology of the evolving patterns depends on several parameters such as the initial film thickness (h(f)), prepattern amplitude (h(st)), duration of solvent vapor exposure (SVE), and wettability of the stamp used for patterning. Periodic rupture of the film at regular intervals imposes directionality on the evolving patterns, resulting in isolated long threads/cylindrical ridges of polymers, which subsequently disintegrate into an aligned array of droplets due to Rayleigh-Plateau instability under specific conditions. Other patterns such as a double periodic array of droplets and an array of holes are also possible to obtain. The evolution can be interrupted at any intermediate stage by terminating the solvent vapor annealing, allowing the creation of pattern morphology on demand. The created patterns are significantly miniaturized in size as compared to features obtained from dewetting a flat film with

Water in contact with extended hydrophobic surfaces: Direct evidence of weak dewetting

DEFF Research Database (Denmark)

Jensen, Torben René; Jensen, Morten Østergaard; Reitzel, Niels

2003-01-01

X-ray reflectivity measurements reveal a significant dewetting of a large hydrophobic paraffin surface floating on water. The dewetting phenomenon extends less than 15 Angstrom into the bulk water phase and results in an integrated density deficit of about one water molecule per 25-30 Angstrom(2...

Directed dewetting of amorphous silicon film by a donut-shaped laser pulse

International Nuclear Information System (INIS)

Yoo, Jae-Hyuck; Zheng, Cheng; Grigoropoulos, Costas P; In, Jung Bin; Sakellari, Ioanna; Raman, Rajesh N; Matthews, Manyalibo J; Elhadj, Selim

2015-01-01

Irradiation of a thin film with a beam-shaped laser is proposed to achieve site-selectively controlled dewetting of the film into nanoscale structures. As a proof of concept, the laser-directed dewetting of an amorphous silicon thin film on a glass substrate is demonstrated using a donut-shaped laser beam. Upon irradiation of a single laser pulse, the silicon film melts and dewets on the substrate surface. The irradiation with the donut beam induces an unconventional lateral temperature profile in the film, leading to thermocapillary-induced transport of the molten silicon to the center of the beam spot. Upon solidification, the ultrathin amorphous silicon film is transformed to a crystalline silicon nanodome of increased height. This morphological change enables further dimensional reduction of the nanodome as well as removal of the surrounding film material by isotropic silicon etching. These results suggest that laser-based dewetting of thin films can be an effective way for scalable manufacturing of patterned nanostructures. (paper)

Directed dewetting of amorphous silicon film by a donut-shaped laser pulse.

Science.gov (United States)

Yoo, Jae-Hyuck; In, Jung Bin; Zheng, Cheng; Sakellari, Ioanna; Raman, Rajesh N; Matthews, Manyalibo J; Elhadj, Selim; Grigoropoulos, Costas P

2015-04-24

Irradiation of a thin film with a beam-shaped laser is proposed to achieve site-selectively controlled dewetting of the film into nanoscale structures. As a proof of concept, the laser-directed dewetting of an amorphous silicon thin film on a glass substrate is demonstrated using a donut-shaped laser beam. Upon irradiation of a single laser pulse, the silicon film melts and dewets on the substrate surface. The irradiation with the donut beam induces an unconventional lateral temperature profile in the film, leading to thermocapillary-induced transport of the molten silicon to the center of the beam spot. Upon solidification, the ultrathin amorphous silicon film is transformed to a crystalline silicon nanodome of increased height. This morphological change enables further dimensional reduction of the nanodome as well as removal of the surrounding film material by isotropic silicon etching. These results suggest that laser-based dewetting of thin films can be an effective way for scalable manufacturing of patterned nanostructures.

Dewetting and deposition of thin films with insoluble surfactants from curved silicone hydrogel substrates.

Science.gov (United States)

Bhamla, M Saad; Balemans, Caroline; Fuller, Gerald G

2015-07-01

We investigate the stabilizing effect of insoluble surfactant monolayers on thin aqueous films. We first describe an experimental platform that enables the formation of aqueous films laden with dipalmitoylphosphatidylcholine (DPPC) monolayers on curved silicone hydrogel (SiHy) substrates. We show that these surfactant layers extend the lifetime of the aqueous films. The films eventually "dewet" by the nucleation and growth of dry areas and the onset of this dewetting can be controlled by the surface rheology of the DPPC layer. We thus demonstrate that increasing the interfacial rheology of the DPPC layer leads to stable films that delay dewetting. We also show that dewetting can be exploited to controllably pattern the underlying curved SiHy substrates with DPPC layers. Copyright © 2015 Elsevier Inc. All rights reserved.

Competitive concurrence of surface wrinkling and dewetting of liquid crystalline polymer films on non-wettable substrates.

Science.gov (United States)

Song, Sung E; Choi, Gwan H; Yi, Gi-Ra; Yoo, Pil J

2017-11-01

Polymeric thin films coated on non-wettable substrates undergo film-instabilities, which are usually manifested as surface deformation in the form of dewetting or wrinkling. The former takes place in fluidic films, whereas the latter occurs in solid films. Therefore, there have rarely been reports of systems involving simultaneous deformations of dewetting and wrinkling. In this study, we propose polymeric thin films of liquid crystalline (LC) mesogens prepared on a non-wettable Si substrate and apply a treatment of plasma irradiation to form a thin polymerized layer at the surface. The resulting compressive stress generated in the surface region drives the formation of wrinkles, while at the same time, dipolar attraction between LC molecules induces competitive cohesive dewetting. Intriguing surface structures were obtained whereby dewetting-like hole arrays are nested inside the randomly propagated wrinkles. The structural features are readily controlled by the degree of surface cross-linking, hydrophilicity of the substrates, and the LC film thickness. In particular, dewetting of LC mesogens is observed to be restricted to occur at the trough regions of wrinkles, exhibiting the typical behavior of geometrically confined dewetting. Finally, wrinkling-dewetting mixed structures are separated from the substrate in the form of free standing films to demonstrate the potential applicability as membranes.

Dynamics of solid thin-film dewetting in the silicon-on-insulator system

Science.gov (United States)

Bussmann, E.; Cheynis, F.; Leroy, F.; Müller, P.; Pierre-Louis, O.

2011-04-01

Using low-energy electron microscopy movies, we have measured the dewetting dynamics of single-crystal Si(001) thin films on SiO2 substrates. During annealing (T>700 °C), voids open in the Si, exposing the oxide. The voids grow, evolving Si fingers that subsequently break apart into self-organized three-dimensional (3D) Si nanocrystals. A kinetic Monte Carlo model incorporating surface and interfacial free energies reproduces all the salient features of the morphological evolution. The dewetting dynamics is described using an analytic surface-diffusion-based model. We demonstrate quantitatively that Si dewetting from SiO2 is mediated by surface-diffusion driven by surface free-energy minimization.

Dynamics of solid thin-film dewetting in the silicon-on-insulator system

International Nuclear Information System (INIS)

Bussmann, E; Cheynis, F; Leroy, F; Mueller, P; Pierre-Louis, O

2011-01-01

Using low-energy electron microscopy movies, we have measured the dewetting dynamics of single-crystal Si(001) thin films on SiO 2 substrates. During annealing (T>700 deg. C), voids open in the Si, exposing the oxide. The voids grow, evolving Si fingers that subsequently break apart into self-organized three-dimensional (3D) Si nanocrystals. A kinetic Monte Carlo model incorporating surface and interfacial free energies reproduces all the salient features of the morphological evolution. The dewetting dynamics is described using an analytic surface-diffusion-based model. We demonstrate quantitatively that Si dewetting from SiO 2 is mediated by surface-diffusion driven by surface free-energy minimization.

Design of free patterns of nanocrystals with ad hoc features via templated dewetting

Energy Technology Data Exchange (ETDEWEB)

Aouassa, M.; Berbezier, I.; Favre, L.; Ronda, A. [IM2NP, CNRS, AMU, Marseille (France); Bollani, M.; Sordan, R. [LNES, Como (Italy); Delobbe, A.; Sudraud, P. [Orsay Physics, Fuveau (France)

2012-07-02

Design of monodisperse ultra-small nanocrystals (NCs) into large scale patterns with ad hoc features is demonstrated. The process makes use of solid state dewetting of a thin film templated through alloy liquid metal ion source focused ion beam (LMIS-FIB) nanopatterning. The solid state dewetting initiated at the edges of the patterns controllably creates the ordering of NCs with ad hoc placement and periodicity. The NC size is tuned by varying the nominal thickness of the film while their position results from the association of film retraction from the edges of the lay out and Rayleigh-like instability. The use of ultra-high resolution LMIS-FIB enables to produce monocrystalline NCs with size, periodicity, and placement tunable as well. It provides routes for the free design of nanostructures for generic applications in nanoelectronics.

Transition from Spin Dewetting to continuous film in spin coating of Liquid Crystal 5CB.

Science.gov (United States)

Dhara, Palash; Bhandaru, Nandini; Das, Anuja; Mukherjee, Rabibrata

2018-05-08

Spin dewetting refers to spontaneous rupture of the dispensed solution layer during spin coating, resulting in isolated but periodic, regular sized domains of the solute and is pre-dominant when the solute concentration (C n ) is very low. In this article we report how the morphology of liquid crystal (LC) 5CB thin films coated on flat and patterned PMMA substrate transform from spin dewetted droplets to continuous films with increase in C n . We further show that within the spin dewetted regime, with gradual increase in the solute concentration, periodicity of the isotropic droplets (λ D ) as well as their mean diameter (d D ), gradually decreases, till the film becomes continuous at a critical concentration (C n *). Interestingly, the trend that λ D reduces with increase in C n is exact opposite to what is observed in thermal/solvent vapor induced dewetting of a thin film. The spin dewetted droplets exhibit transient Radial texture, in contrast to Schlieren texture observed in elongated threads and continuous films of 5CB, which remains in the Nematic phase at room temperature. Finally we show that by casting the film on a grating patterned substrate it becomes possible to align the spin dewetted droplets along the contours substrate patterns.

Dynamics of solid thin-film dewetting in the silicon-on-insulator system

Energy Technology Data Exchange (ETDEWEB)

Bussmann, E; Cheynis, F; Leroy, F; Mueller, P [Centre Interdisciplinaire de Nanoscience de Marseille (CINaM) CNRS UPR 3118, Aix-Marseille Universite, 13288 Marseille (France); Pierre-Louis, O, E-mail: muller@cinam.univ-mrs.fr [LPMCN, Universite Lyon 1, 43 Bd du 11 novembre, 69622 Villeurbane (France)

2011-04-15

Using low-energy electron microscopy movies, we have measured the dewetting dynamics of single-crystal Si(001) thin films on SiO{sub 2} substrates. During annealing (T>700 deg. C), voids open in the Si, exposing the oxide. The voids grow, evolving Si fingers that subsequently break apart into self-organized three-dimensional (3D) Si nanocrystals. A kinetic Monte Carlo model incorporating surface and interfacial free energies reproduces all the salient features of the morphological evolution. The dewetting dynamics is described using an analytic surface-diffusion-based model. We demonstrate quantitatively that Si dewetting from SiO{sub 2} is mediated by surface-diffusion driven by surface free-energy minimization.

The Optical Properties of Cu-Ni Nanoparticles Produced via Pulsed Laser Dewetting of Ultrathin Films: The Effect of Nanoparticle Size and Composition on the Plasmon Response

International Nuclear Information System (INIS)

Wu, Yeuyeng; Fowlkes, Jason Davidson; Rack, Philip D.

2011-01-01

Thin film Cu-Ni alloys ranging from 2-8nm were synthesized and their optical properties were measured as-deposited and after a laser treatment which dewet the films into arrays of spatially correlated nanoparticles. The resultant nanoparticle size and spacing are attributed to laser induced spinodal dewetting process. The evolution of the spinodal dewetting process is investigated as a function of the thin film composition which ultimately dictates the size distribution and spacing of the nanoparticles. The optical measurements of the copper rich alloy nanoparticles reveal a signature absorption peak suggestive of a plasmonic peak which red-shifts with increasing nanoparticle size and blue shifts and dampens with increasing nickel concentration.

In situ observation of electron-beam-induced dewetting of CdSe thin film embedded in SiO2

DEFF Research Database (Denmark)

Fabrim, Zacarias Eduardo; Kjelstrup-Hansen, Jakob; Fichtner, Paulo F. P.

In this work we show the dewetting process of the CdSe thin films induced by electron beam irradiation. A multilayer heterostructure of SiO2/CdSe/SiO2 was made by a magnetron sputtering process. A plan-view (PV) sample was irradiated with 200 kV electrons in the TEM with two current densities: 0.......33 A.cm2 and 1.0 A.cm2 and at 80 kV with 0.37 A.cm2. The dewetting of the CdSe film is inferred by a number of micrographs taken during the irradiation. The microstructural changes were analyzed under the assumption of being induced by ballistic collision effects in the absence of sample heating....

Nanoparticles for dewetting suppression of thin polymer films used in chemical sensors

International Nuclear Information System (INIS)

Holmes, Melissa A.; Mackay, Michael E.; Giunta, Rachel K.

2007-01-01

Addition of fullerenes (C 60 or buckyballs) to a linear polymer has been found to eliminate dewetting when a thin (∼50 nm) film is exposed to solvent vapor. Based on neutron reflectivity measurements, it is found that the fullerenes form a coherent layer approximately 2 nm thick at the substrate - polymer film interface during the spin-coating process. The thickness and relative fullerene concentration (∼29 vol%) is not altered during solvent vapor annealing and it is thought this layer forms a solid-like buffer shielding the adverse van der Waals forces promoted by the underlying substrate. Several polymer films produced by spin- or spray-coating were tested on both silicon wafers and live surface acoustic wave sensors demonstrating fullerenes stabilize many different polymer types, prepared by different procedures and on various surfaces. Further, the fullerenes drastically improve sensor performance since dewetted films produce a sensor that is effectively inoperable

Influence of etching process parameters on the antireflection property of Si SWSs by thermally dewetted Ag and Ag/SiO{sub 2} nanopatterns

Energy Technology Data Exchange (ETDEWEB)

Leem, Jung Woo; Yu, Jae Su [Department of Electronics and Radio Engineering, Kyung Hee University, 446-701 Yongin (Korea, Republic of); Song, Young Min; Lee, Yong Tak [Department of Information and Communications, Gwangju Institute of Science and Technology, 500-712 Gwangju (Korea, Republic of)

2011-08-15

The etching parameter dependent antireflection characteristics of disordered Si subwavelength structures (SWSs) by inductively coupled plasma (ICP) etching in a mixture gas of SiCl{sub 4}/Ar using thermally dewetted Ag and Ag/SiO{sub 2} nanopatterns are investigated. The average size and period of Si SWSs are closely correlated with thermal dewetting conditions. For desirable Ag nanoparticle patterns, the profile of Si SWSs is optimized by changing the ICP etching process parameters to obtain the lowest reflectance spectrum. The most tapered SWS with the highest height leads to a relatively low reflectance. The Ag nanopatterns result in more tapered and rough surface SWSs compared to the Ag/SiO{sub 2} nanopatterns, indicating a slightly reduced reflectance. The Si SWS etched using Ag nanopatterns by SiCl{sub 4}/Ar of 5 sccm/10 sccm at 50 W RF power, 200 W ICP power, and 10 mTorr process pressure exhibits a very low total reflectance of <{proportional_to}2.4% in the wavelength range of 400-1000 nm, maintaining a specular reflectance of <16% at 350-1100 nm up to the incident angle of {theta}{sub i} = 50 . (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Nanopatterning Gold by Templated Solid State Dewetting on the Silica Warp and Weft of Diatoms

Directory of Open Access Journals (Sweden)

Jon Hiltz

2016-01-01

Full Text Available The diatom, Nitzschia palea, exhibits complex silica shell (frustule topography that resembles the warp and weft pattern of woven glass. The surface is perforated with a rhombic lattice of roughly oblong pores between periodically undulating transverse weft costae. Exfoliated frustules can be used to template gold nanoparticles by thermally induced dewetting of thin gold films. Acting as templates for the process, the frustules give rise to two coexisting hierarchies of particle sizes and patterned distributions of nanoparticles. By examining temperature dependent dewetting of 5, 10, and 15 nm Au films for various annealing times, we establish conditions for particle formation and patterning. The 5 nm film gives distributions of small particles randomly distributed over the surface and multiple particles at the rhombic lattice points in the pores. Thicker films yield larger faceted particles on the surface and particles that exhibit shapes that are roughly conformal with the shape of the pore container. The pores and costae are sources of curvature instabilities in the film that lead to mass transport of gold and selective accumulation in the weft valleys and pores. We suggest that, with respect to dewetting, the frustule comprises 2-dimensional sublattices of trapping sites. The pattern of dewetting is radically altered by interposing a self-assembled molecular adhesive of mercaptopropyltrimethoxysilane between the Au film overlayer and the frustule. By adjusting the interfacial energy in this manner, a fractal-like overlay of Au islands coexists with a periodic distribution of nanoparticles in the pores.

Bioplasmonic Alloyed Nanoislands Using Dewetting of Bilayer Thin Films.

Science.gov (United States)

Kang, Minhee; Ahn, Myeong-Su; Lee, Youngseop; Jeong, Ki-Hun

2017-10-25

Unlike monometallic materials, bimetallic plasmonic materials offer extensive benefits such as broadband tuning capability or high environmental stability. Here we report a broad range tuning of plasmon resonance of alloyed nanoislands by using solid-state dewetting of gold and silver bilayer thin films. Thermal dewetting after successive thermal evaporation of thin metal double-layer films readily forms AuAg-alloyed nanoislands with a precise composition ratio. The complete miscibility of alloyed nanoislands results in programmable tuning of plasmon resonance wavelength in a broadband visible range. Such extraordinary tuning capability opens up a new direction for plasmonic enhancement in biophotonic applications such as surface-enhanced Raman scattering or plasmon-enhanced fluorescence.

Thin film evolution equations from (evaporating) dewetting liquid layers to epitaxial growth

International Nuclear Information System (INIS)

Thiele, U

2010-01-01

In the present contribution we review basic mathematical results for three physical systems involving self-organizing solid or liquid films at solid surfaces. The films may undergo a structuring process by dewetting, evaporation/condensation or epitaxial growth, respectively. We highlight similarities and differences of the three systems based on the observation that in certain limits all of them may be described using models of similar form, i.e. time evolution equations for the film thickness profile. Those equations represent gradient dynamics characterized by mobility functions and an underlying energy functional. Two basic steps of mathematical analysis are used to compare the different systems. First, we discuss the linear stability of homogeneous steady states, i.e. flat films, and second the systematics of non-trivial steady states, i.e. drop/hole states for dewetting films and quantum-dot states in epitaxial growth, respectively. Our aim is to illustrate that the underlying solution structure might be very complex as in the case of epitaxial growth but can be better understood when comparing the much simpler results for the dewetting liquid film. We furthermore show that the numerical continuation techniques employed can shed some light on this structure in a more convenient way than time-stepping methods. Finally we discuss that the usage of the employed general formulation does not only relate seemingly unrelated physical systems mathematically, but does allow as well for discussing model extensions in a more unified way.

Transcellular tunnel dynamics: Control of cellular dewetting by actomyosin contractility and I-BAR proteins.

Science.gov (United States)

Lemichez, Emmanuel; Gonzalez-Rodriguez, David; Bassereau, Patricia; Brochard-Wyart, Françoise

2013-03-01

Dewetting is the spontaneous withdrawal of a liquid film from a non-wettable surface by nucleation and growth of dry patches. Two recent reports now propose that the principles of dewetting explain the physical phenomena underpinning the opening of transendothelial cell macroaperture (TEM) tunnels, referred to as cellular dewetting. This was discovered by studying a group of bacterial toxins endowed with the property of corrupting actomyosin cytoskeleton contractility. For both liquid and cellular dewetting, the growth of holes is governed by a competition between surface forces and line tension. We also discuss how the dynamics of TEM opening and closure represent remarkable systems to investigate actin cytoskeleton regulation by sensors of plasma membrane curvature and investigate the impact on membrane tension and the role of TEM in vascular dysfunctions. Copyright © 2013 Soçiété Française des Microscopies and Soçiété de Biologie Cellulaire de France.

Gold nanoparticle array formation on dimpled Ta templates using pulsed laser-induced thin film dewetting.

Science.gov (United States)

El-Sayed, Hany A; Horwood, Corie A; Owusu-Ansah, Ebenezer; Shi, Yujun J; Birss, Viola I

2015-04-28

Here we show that pulsed laser-induced dewetting (PLiD) of a thin Au metallic film on a nano-scale ordered dimpled tantalum (DT) surface results in the formation of a high quality Au nanoparticle (NP) array. In contrast to thermal dewetting, PLiD does not result in deformation of the substrate, even when the Au film is heated to above its melting point. PLiD causes local heating of only the metal film and thus thermal oxidation of the Ta substrate can be avoided, also because of the high vacuum (low pO2) environment employed. Therefore, this technique can potentially be used to fabricate NP arrays composed of high melting point metals, such as Pt, not previously possible using conventional thermal annealing methods. We also show that the Au NPs formed by PLiD are more spherical in shape than those formed by thermal dewetting, likely demonstrating a different dewetting mechanism in the two cases. As the metallic NPs formed on DT templates are electrochemically addressable, a longer-term objective of this work is to determine the effect of NP size and shape (formed by laser vs. thermal dewetting) on their electrocatalytic properties.

Water in contact with extended hydrophobic surfaces: Direct evidence of weak dewetting

International Nuclear Information System (INIS)

Jensen, Torben R.; Kjaer, Kristian; Oestergaard Jensen, Morten; Peters, Guenther H.; Reitzel, Niels; Balashev, Konstantin; Bjoernholm, Thomas

2003-01-01

X-ray reflectivity measurements reveal a significant dewetting of a large hydrophobic paraffin surface floating on water. The dewetting phenomenon extends less than 15 A into the bulk water phase and results in an integrated density deficit of about one water molecule per 25-30 A 2 of water in contact with the paraffin surface. The results are supported by molecular dynamics simulations and related to the hydrophobic effect

Cross-sectional characterization of the dewetting of a Au/Ni bilayer film

Energy Technology Data Exchange (ETDEWEB)

Cen, Xi; Thron, Andrew M.; Zhang, Xinming; Benthem, Klaus van

2017-07-15

The solid state dewetting of Au/Ni bilayer films was investigated by cross-sectional transmission electron microscopy techniques, including energy-dispersive X-ray spectroscopy, electron energy-loss spectroscopy and precession electron diffraction. After annealing under high vacuum conditions the early stage of film agglomeration revealed significant changes in film morphology and chemical distribution. Both Au and Ni showed texturing. Despite the initial deposition sequence of the as-deposited Au/Ni/SiO{sub 2}/Si interface structure, the majority of the metal/SiO{sub 2} interface was Au/SiO{sub 2} after annealing at 675 °C for 1 h. Void nucleation was predominantly observed at Au/Ni/SiO{sub 2} triple junctions, rather than grain boundary grooving at free surface of the metal film. Detailed cross-sectional characterization reveals that the Au/Ni interface in addition to small amounts of metal alloying strongly affects film break-up and agglomeration kinetics. The formation of Au/SiO{sub 2} interface sections is found to be energetically preferred over Ni/SiO{sub 2} due to compressive stress in the as-deposited Ni layer. Void nucleation is observed at the film/substrate interface, while the formation of voids at Ni/Au phase boundaries inside the metal film is caused by the Kirkendall effect. - Highlights: • The dewetting of Au/Ni bilayer films was studied by cross-sectional TEM techniques. • The majority of the metal/SiO{sub 2} interface was comprised of Au/SiO{sub 2} after annealing. • Void formation was dominant for hole nucleation at early dewetting stage. • The Kirkendall effect was also observed to cause the formation of voids.

Solvent annealing induced phase separation and dewetting in PMMA∕SAN blend film: film thickness and solvent dependence.

Science.gov (United States)

You, Jichun; Zhang, Shuangshuang; Huang, Gang; Shi, Tongfei; Li, Yongjin

2013-06-28

The competition between "dewetting" and "phase separation" behaviors in polymer blend films attracts significant attention in the last decade. The simultaneous phase separation and dewetting in PMMA∕SAN [poly(methyl methacrylate) and poly(styrene-ran-acrylonitrile)] blend ultrathin films upon solvent annealing have been observed for the first time in our previous work. In this work, film thickness and annealing solvent dependence of phase behaviors in this system has been investigated using atomic force microscopy and grazing incidence small-angle X-ray scattering (GISAXS). On one hand, both vertical phase separation and dewetting take place upon selective solvent vapor annealing, leading to the formation of droplet∕mimic-film structures with various sizes (depending on original film thickness). On the other hand, the whole blend film dewets the substrate and produces dispersed droplets on the silicon oxide upon common solvent annealing. GISAXS results demonstrate the phase separation in the big dewetted droplets resulted from the thicker film (39.8 nm). In contrast, no period structure is detected in small droplets from the thinner film (5.1 nm and 9.7 nm). This investigation indicates that dewetting and phase separation in PMMA∕SAN blend film upon solvent annealing depend crucially on the film thickness and the atmosphere during annealing.

Ordered to isotropic morphology transition in pattern-directed dewetting of polymer thin films on substrates with different feature heights.

Science.gov (United States)

Roy, Sudeshna; Mukherjee, Rabibrata

2012-10-24

Controlled dewetting of a thin polymer film on a topographically patterned substrate is an interesting approach for aligning isotropic dewetted structures. In this article, we investigate the influence of substrate feature height (H(S)) on the dewetting pathway and final pattern morphology by studying the dewetting of polystyrene (PS) thin films on grating substrates with identical periodicity (λ(P) = 1.5 μm), but H(S) varying between 10 nm and 120 nm. We identify four distinct categories of final dewetted morphology, with different extent of ordering: (1) array of aligned droplets (H(S) ≈ 120 nm); (2) aligned undulating ribbons (H(S) ≈ 70-100 nm); (3) multilength scale structures with coexisting large droplets uncorrelated to the substrate and smaller droplets/ribbons aligned along the stripes (H(S) ≈ 40-60 nm); and (4) large droplets completely uncorrelated to the substrate (H(S) dewetted morphologies and transition across categories remain generically unaltered. We finally show that the structures obtained by dewetting on different H(S) substrates exhibits different levels of hydrophobicity because of combined spatial variation of chemical and topographic contrast along the surface. Thus, the work reported in this article can find potential application in fabricating surfaces with controlled wettability.

Solid-State Dewetting of Gold Aggregates/Islands on TiO2 Nanorod Structures Grown by Oblique Angle Deposition.

Science.gov (United States)

Liu, Shizhao; Plawsky, Joel L

2017-12-12

A composite film made of a stable gold nanoparticle (NP) array with well-controlled separation and size atop a TiO 2 nanorod film was fabricated via the oblique angle deposition (OAD) technique. The fabrication of the NP array is based on controlled, Rayleigh-instability-induced, solid-state dewetting of as-deposited gold aggregates on the TiO 2 nanorods. It was found that the initial spacing between as-deposited gold aggregates along the vapor flux direction should be greater than the TiO 2 interrod spacing created by 80° OAD to control dewetting and produce NP arrays. A numerical investigation of the process was conducted using a phase-field modeling approach. Simulation results showed that coalescence between neighboring gold aggregates is likely to have caused the uncontrolled dewetting in the 80° deposition, and this could be circumvented if the initial spacing between gold aggregates is larger than a critical value s min . We also found that TiO 2 nanorod tips affect dewetting dynamics differently than planar TiO 2 . The topology of the tips can induce contact line pinning and an increase in the contact angle along the vapor flux direction to the supported gold aggregates. These two effects are beneficial for the fabrication of monodisperse NPs based on Rayleigh-instability-governed self-assembly of materials, as they help to circumvent the undesired coalescence and facilitate the instability growth on the supported material. The findings uncover the application potential of OAD as a new method to fabricate structured films as template substrates to mediate dewetting. The reported composite films would have uses in optical coatings and photocatalytic systems, taking advantage of their ability to combine plasmonic nanostructures within a nanostructured dielectric film.

Influence of surfactants in forced dynamic dewetting.

Science.gov (United States)

Henrich, Franziska; Fell, Daniela; Truszkowska, Dorota; Weirich, Marcel; Anyfantakis, Manos; Nguyen, Thi-Huong; Wagner, Manfred; Auernhammer, Günter K; Butt, Hans-Jürgen

2016-09-20

In this work we show that the forced dynamic dewetting of surfactant solutions depends sensitively on the surfactant concentration. To measure this effect, a hydrophobic rotating cylinder was horizontally half immersed in aqueous surfactant solutions. Dynamic contact angles were measured optically by extrapolating the contour of the meniscus to the contact line. Anionic (sodium 1-decanesulfonate, S-1DeS), cationic (cetyl trimethylammonium bromide, CTAB) and nonionic surfactants (C 4 E 1 , C 8 E 3 and C 12 E 5 ) with critical micelle concentrations (CMCs) spanning four orders of magnitude were used. The receding contact angle in water decreased with increasing velocity. This decrease was strongly enhanced when adding surfactant, even at surfactant concentrations of 10% of the critical micelle concentration. Plots of the receding contact angle-versus-velocity almost superimpose when being plotted at the same relative concentration (concentration/CMC). Thus the rescaled concentration is the dominating property for dynamic dewetting. The charge of the surfactants did not play a role, thus excluding electrostatic effects. The change in contact angle can be interpreted by local surface tension gradients, i.e. Marangoni stresses, close to the three-phase contact line. The decrease of dynamic contact angles with velocity follows two regimes. Despite the existence of Marangoni stresses close to the contact line, for a dewetting velocity above 1-10 mm s -1 the hydrodynamic theory is able to describe the experimental results for all surfactant concentrations. At slower velocities an additional steep decrease of the contact angle with velocity was observed. Particle tracking velocimetry showed that the flow profiles do not differ with and without surfactant on a scales >100 μm.

Solution-Processed Small-Molecule Bulk Heterojunctions: Leakage Currents and the Dewetting Issue for Inverted Solar Cells.

Science.gov (United States)

Destouesse, Elodie; Chambon, Sylvain; Courtel, Stéphanie; Hirsch, Lionel; Wantz, Guillaume

2015-11-11

In organic photovoltaic (PV) devices based on solution-processed small molecules, we report here that the physicochemical properties of the substrate are critical for achieving high-performances organic solar cells. Three different substrates were tested: ITO coated with PSS, ZnO sol-gel, and ZnO nanoparticles. PV performances are found to be low when the ZnO nanoparticles layer is used. This performance loss is attributed to the formation of many dewetting points in the active layer, because of a relatively high roughness of the ZnO nanoparticles layer, compared to the other layers. We successfully circumvented this phenomenon by adding a small quantity of polystyrene (PS) in the active layer. The introduction of PS improves the quality of film forming and reduces the dark currents of solar cells. Using this method, high-efficiency devices were achieved, even in the case of substrates with higher roughness.

Wetting and Dewetting Transitions on Submerged Superhydrophobic Surfaces with Hierarchical Structures.

Science.gov (United States)

Wu, Huaping; Yang, Zhe; Cao, Binbin; Zhang, Zheng; Zhu, Kai; Wu, Bingbing; Jiang, Shaofei; Chai, Guozhong

2017-01-10

The wetting transition on submersed superhydrophobic surfaces with hierarchical structures and the influence of trapped air on superhydrophobic stability are predicted based on the thermodynamics and mechanical analyses. The dewetting transition on the hierarchically structured surfaces is investigated, and two necessary thermodynamic conditions and a mechanical balance condition for dewetting transition are proposed. The corresponding thermodynamic phase diagram of reversible transition and the critical reversed pressure well explain the experimental results reported previously. Our theory provides a useful guideline for precise controlling of breaking down and recovering of superhydrophobicity by designing superhydrophobic surfaces with hierarchical structures under water.

Self-organized morphological evolution and dewetting in solvent vapor annealing of spin coated polymer blend nanostructures.

Science.gov (United States)

Roy, Sudeshna; Sharma, Ashutosh

2015-07-01

Dewetting pathways, kinetics and morphologies of thin films of phase separating polymer blends are governed by the relative mobilities of the two components. We characterize the morphological transformations of the nanostructures of a PS/PMMA blend by annealing in toluene and chloroform vapors. Toluene leads to faster reorganization of PS, whereas chloroform engenders the opposite effect. Spin coating produces a very rough PMMA rich layer that completely wets the substrate and forms a plethora of slender columns protruding through the continuous PS rich layer on top. The nanostructures were stable under long thermal annealing but in the vapor annealing, phase separation and dewetting occurred readily to form the equilibrium structures of dewetted droplets of PS on top of PMMA which also climbed around the PS droplets to form rims. Toluene and chloroform annealing required around 50 h and 1 h respectively to attain the equilibrium. Substantial differences are observed in the intermediate morphologies (heights of nanostructures, roughness and size). PMMA columns remained embedded in the dewetted PS droplets, whereas a high mobility of PMMA in chloroform allowed its rapid evacuation during dewetting to produce an intermediate swiss-cheese like morphology of PS domains. Copyright © 2015 Elsevier Inc. All rights reserved.

Magnetic Iron Oxide Nanowires Formed by Reactive Dewetting.

Science.gov (United States)

Bennett, Roger A; Etman, Haitham A; Hicks, Hannah; Richards, Leah; Wu, Chen; Castell, Martin R; Dhesi, Sarnjeet S; Maccherozzi, Francesco

2018-04-11

The growth and reactive dewetting of ultrathin films of iron oxides supported on Re(0001) surfaces have been imaged in situ in real time. Initial growth forms a nonmagnetic stable FeO (wüstite like) layer in a commensurate network upon which high aspect ratio nanowires of several microns in length but less than 40 nm in width can be fabricated. The nanowires are closely aligned with the substrate crystallography and imaging by X-ray magnetic circular dichroism shows that each contain a single magnetic domain. The driving force for dewetting appears to be the minimization of strain energy of the Fe 3 O 4 crystallites and follows the Tersoff and Tromp model in which strain is minimized at constant height by extending in one epitaxially matched direction. Such wires are promising in spintronic applications and we predict that the growth will also occur on other hexagonal substrates.

Smooth perfluorinated surfaces with different chemical and physical natures: their unusual dynamic dewetting behavior toward polar and nonpolar liquids.

Science.gov (United States)

Cheng, Dalton F; Masheder, Benjamin; Urata, Chihiro; Hozumi, Atsushi

2013-09-10

The effects of surface chemistry and the mobility of surface-tethered functional groups of various perfluorinated surfaces on their dewetting behavior toward polar (water) and nonpolar (n-hexadecane, n-dodecane, and n-decane) liquids were investigated. In this study, three types of common smooth perfluorinated surfaces, that is, a perfluoroalkylsilane (heptadecafluoro-1,1,2,2-tetrahydrooctyl-dimethylchlorosilane, FAS17) monomeric layer, an amorphous fluoropolymer film (Teflon AF 1600), and a perfluorinated polyether (PFPE)-terminated polymer brush film (Optool DSX), were prepared and their static/dynamic dewetting characteristics were compared. Although the apparent static contact angles (CAs) of these surfaces with all probe liquids were almost identical to each other, the ease of movement of liquid drops critically depended on the physical (solidlike or liquidlike) natures of the substrate surface. CA hysteresis and substrate tilt angles (TAs) of all probe liquids on the Optool DSX surface were found to be much lower than those of Teflon AF1600 and FAS17 surfaces due to its physical polymer chain mobility at room temperature and the resulting liquidlike nature. Only 6.0° of substrate incline was required to initiate movement for a small drop (5 μL) of n-decane, which was comparable to the reported substrate TA value (5.3°) for a superoleophobic surface (θ(S) > 160°, textured perfluorinated surface). Such unusual dynamic dewetting behavior of the Optool DSX surface was also markedly enhanced due to the significant increase in the chain mobility of PFPE by moderate heating (70 °C) of the surface, with substrate TA reducing to 3.0°. CA hysteresis and substrate TAs rather than static CAs were therefore determined to be of greater consequence for the estimation of the actual dynamic dewetting behavior of alkane probe liquids on these smooth perfluorinated surfaces. Their dynamic dewettability toward alkane liquids is in the order of Optool DSX > Teflon AF1600 �

Dynamics of the evaporative dewetting of a volatile liquid film confined within a circular ring.

Science.gov (United States)

Sun, Wei; Yang, Fuqian

2015-04-07

The dewetting dynamics of a toluene film confined within a copper ring on a deformable PMMA film is studied. The toluene film experiences evaporation and dewetting, which leads to the formation of a circular contact line around the center of the copper ring. The contact line recedes smoothly toward the copper ring at a constant velocity until reaching a dynamic "stick" state to form the first circular polymer ridge. The average receding velocity is found to be dependent on the dimensions of the copper ring (the copper ring diameter and the cross-sectional diameter of the copper wire) and the thickness of the PMMA films. A model is presented to qualitatively explain the evaporative dewetting phenomenon.

Electric field induced dewetting at polymer/polymer interfaces

NARCIS (Netherlands)

Lin, Z.Q.; Kerle, T.; Russell, T.P.; Schäffer, E.; Steiner, U

2002-01-01

External electric fields were used to amplify interfacial fluctuations in the air/polymer/polymer system where one polymer dewets the other. Two different hydrodynamic regimes were found as a function of electric field strength. If heterogeneous nucleation leads to the formation of holes before the

Sequence control of phase separation and dewetting in PS/PVME blend thin films by changing molecular weight of PS.

Science.gov (United States)

Xia, Tian; Qin, Yaping; Huang, Yajiang; Huang, Ting; Xu, Jianhui; Li, Youbing

2016-11-28

The morphology evolution mechanism of polystyrene (PS)/poly (vinyl methyl ether) (PVME) blend thin films with different PS molecular weights (M w ) was studied. It was found that the morphology evolution was closely related to the molecular weight asymmetry between PS and PVME. In the film where M w (PS) ≈ M w (PVME), dewetting happened at the interface between the bottom layer and substrate after SD phase separation. While in the film where M w (PS) > M w (PVME), dewetting happened at the interface between the middle PS/PVME blend layer and bottom PVME layer near the substrate prior to phase separation. The different sequences of phase separation and dewetting and different interface for dewetting occurrence were studied by regarding the competitive effects of viscoelasticity contrast between polymer components and preferential wetting between PVME and the substrate. The viscoelastic nature of the PS component played a crucial role in the sequence of phase separation and dewetting.

A novel in-vitro method for assessing contact lens surface dewetting: Non-invasive keratograph dry-up time (NIK-DUT).

Science.gov (United States)

Marx, Sebastian; Sickenberger, Wolfgang

2017-12-01

This study was designed to develop a novel technique called non-invasive keratograph dry-up time (NIK-DUT), which used an adapted corneal topographer, to analyse in-vitro contact lens surface dewetting and the effects of combinations of lenses and lens care solutions on dewetting. Variables were assessed to optimise sensitivity and reproducibility. To validate the method, in-vitro dewetting of silicone hydrogel contact lenses (balafilcon A, comfilcon A, lotrafilcon A, lotrafilcon B and senofilcon A) was tested. All lens types were soaked in OPTI-FREE ® PureMoist ® Multipurpose Disinfecting Solution (OFPM) and Sensitive Eyes ® Saline Solution. The mean NIK-DUT, defined as drying of 25% of the placido ring measurement segments (NIK-DUT_S25), was calculated for each lens/lens solution combination and a visual map constructed representing the time and location of the dry-up event. Optimal conditions for NIK-DUT measurement included mounting onto a glass stage with a surface geometry of r=8.5mm, e=0, and measuring with high intensity red or white illumination. This method detected significant differences in contact lens dewetting with different lens soaking solutions. NIK-DUT_S25 for all lenses was longer when pre-soaked in OFPM versus saline. Visual analysis showed that dewetting of contact lenses was not uniform across surfaces and differed between test solutions. NIK-DUT is suitable for detecting differences in dewetting among various contact lenses and lens-care combinations. NIK-DUT can quantify the dewetting of large areas of lens surfaces with little subjective influence. Lens care solutions containing surface-active wetting agents were found to delay surface dewetting of silicone hydrogel lenses. Copyright © 2017. Published by Elsevier Ltd.

Controllable Fabrication of Au Nanocups by Confined-Space Thermal Dewetting for OCT Imaging.

Science.gov (United States)

Gao, Aiqin; Xu, Wenjing; Ponce de León, Yenisey; Bai, Yaocai; Gong, Mingfu; Xie, Kongliang; Park, Boris Hyle; Yin, Yadong

2017-07-01

Here, this study reports a novel confined-space thermal dewetting strategy for the fabrication of Au nanocups with tunable diameter, height, and size of cup opening. The nanocup morphology is defined by the cup-shaped void space created by a yolk-shell silica template that spontaneously takes an eccentric configuration during annealing. Thermal dewetting of Au, which is sandwiched between the yolk and shell, leads to the desired nanocup morphology. With strong scattering in near infrared, the Au nanocups exhibit superior efficiency as contrast agents for spectral-domain optical coherence tomography imaging. This confined-space thermal dewetting strategy is scalable and general, and can be potentially extended to the synthesis of novel anisotropic nanostructures of various compositions that are difficult to produce by conventional wet chemical or physical methods, thus opening up opportunities for many new applications. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Structure Formation of Ultrathin PEO Films at Solid Interfaces—Complex Pattern Formation by Dewetting and Crystallization

Science.gov (United States)

Braun, Hans-Georg; Meyer, Evelyn

2013-01-01

The direct contact of ultrathin polymer films with a solid substrate may result in thin film rupture caused by dewetting. With crystallisable polymers such as polyethyleneoxide (PEO), molecular self-assembly into partial ordered lamella structures is studied as an additional source of pattern formation. Morphological features in ultrathin PEO films (thickness dewetting patterns and diffusion limited growth pattern of ordered lamella growing within the dewetting areas. Besides structure formation of hydrophilic PEO molecules, n-alkylterminated (hydrophobic) PEO oligomers are investigated with respect to self-organization in ultrathin films. Morphological features characteristic for pure PEO are not changed by the presence of the n-alkylgroups. PMID:23385233

Lithography-Free Fabrication of Large Area Subwavelength Antireflection Structures Using Thermally Dewetted Pt/Pd Alloy Etch Mask

Directory of Open Access Journals (Sweden)

Kang Jeong-Jin

2009-01-01

Full Text Available Abstract We have demonstrated lithography-free, simple, and large area fabrication method for subwavelength antireflection structures (SAS to achieve low reflectance of silicon (Si surface. Thin film of Pt/Pd alloy on a Si substrate is melted and agglomerated into hemispheric nanodots by thermal dewetting process, and the array of the nanodots is used as etch mask for reactive ion etching (RIE to form SAS on the Si surface. Two critical parameters, the temperature of thermal dewetting processes and the duration of RIE, have been experimentally studied to achieve very low reflectance from SAS. All the SAS have well-tapered shapes that the refractive index may be changed continuously and monotonously in the direction of incident light. In the wavelength range from 350 to 1800 nm, the measured reflectance of the fabricated SAS averages out to 5%. Especially in the wavelength range from 550 to 650 nm, which falls within visible light, the measured reflectance is under 0.01%.

Nanostructure Formation by controlled dewetting on patterned substrates: A combined theoretical, modeling and experimental study.

Science.gov (United States)

Lu, Liang-Xing; Wang, Ying-Min; Srinivasan, Bharathi Madurai; Asbahi, Mohamed; Yang, Joel K W; Zhang, Yong-Wei

2016-09-01

We perform systematic two-dimensional energetic analysis to study the stability of various nanostructures formed by dewetting solid films deposited on patterned substrates. Our analytical results show that by controlling system parameters such as the substrate surface pattern, film thickness and wetting angle, a variety of equilibrium nanostructures can be obtained. Phase diagrams are presented to show the complex relations between these system parameters and various nanostructure morphologies. We further carry out both phase field simulations and dewetting experiments to validate the analytically derived phase diagrams. Good agreements between the results from our energetic analyses and those from our phase field simulations and experiments verify our analysis. Hence, the phase diagrams presented here provide guidelines for using solid-state dewetting as a tool to achieve various nanostructures.

Dewetting of thin films on flexible substrates via direct-write laser exposure

Science.gov (United States)

Ferrer, Anthony Jesus

Microelectromechanical systems (MEMS) have enabled a wide variety of technologies both in the consumer space and in industrial/research areas. At the market level, such devices advance by the invention and innovation of production techniques. Additionally, there has been increased demand for flexible versions of such MEMS devices. Thin film patterning, represents a key technology for the realization of such flexible electronics. Patterns and methods that can be directly written into the thin film allow for design modification on the fly with the need for harsh chemicals and long etching steps. Laser-induced dewetting has the potential to create patterns in thin films at both the microscopic and nanoscopic level without wasting deposited material. This thesis presents the first demonstration of high-speed direct-write patterning of metallic thin films that uses a laser-induced dewetting phenomenon to prevent material loss. The ability to build film material with this technique is explored using various scanning geometries. Finally, demonstrations of direct-write dewetting of a variety of thin films will be presented with special consideration for high melting point metals deposited upon polymer substrates.

The effect of different thickness alumina capping layers on the final morphology of dewet thin Ni films

Science.gov (United States)

White, Benjamin C.; Behbahanian, Amir; Stoker, T. McKay; Fowlkes, Jason D.; Hartnett, Chris; Rack, Phillip D.; Roberts, Nicholas A.

2018-03-01

Nanoparticles on a substrate have numerous applications in nanotechnology, from enhancements to solar cell efficiency to improvements in carbon nanotube growth. Producing nanoparticles in a cost effective fashion with control over size and spacing is desired, but difficult to do. This work presents a scalable method for altering the radius and pitch distributions of nickel nanoparticles. The introduction of alumina capping layers to thin nickel films during a pulsed laser-induced dewetting process has yielded reductions in the mean and standard deviation of radii and pitch for dewet nanoparticles with no noticeable difference in final morphology with increased capping layer thickness. The differences in carbon nanotube mats grown, on the uncapped sample and one of the capped samples, is also presented here, with a more dense mat being present for the capped case.

Local nanostructuring of gold thin films through dewetting induced by Ga{sup +} irradiation

Energy Technology Data Exchange (ETDEWEB)

Lo Savio, R., E-mail: roberto.lo.savio@edu.unige.it [Physics Department and Nanomed Labs, Università di Genova, Via Dodecaneso 33, 16146 Genova (Italy); Repetto, L. [Physics Department and Nanomed Labs, Università di Genova, Via Dodecaneso 33, 16146 Genova (Italy); Šetina Batič, B. [Inštitut Za Kovinske Materiale in Tehnologije, Lepi pot 11, 1000 Ljubljana (Slovenia); Firpo, G.; Valbusa, U. [Physics Department and Nanomed Labs, Università di Genova, Via Dodecaneso 33, 16146 Genova (Italy)

2015-07-01

Dewetting of ion-irradiated metal films is a consequence of the local melting occurring during the irradiation. In this study we present the dewetting evolution of Au thin films bombarded with Ga{sup +} ions in a focused ion beam system, pointing out the different surface patterns observed in films having different starting thickness and morphology. In fact, in ion-irradiated films thicker than 2 nm the typical features of dewetted liquids appear, i.e. enlarging dry holes surrounded by metal interconnections. On the other side, a different behavior is observed in thinner discontinuous films, where a dense distribution of circular nanoparticles is formed upon irradiation. We studied the dependence of Au nanoparticles distribution obtained for different ion energies and fluences, determining that a maximum fluence of ∼2 × 10{sup 14} Ga/cm{sup 2} can be used to achieve a monomodal distribution of nanoparticles with regular shape, before detrimental effects of sputtering occur.

Au nanoparticles decorated SiO2 nanowires by dewetting on curved surfaces: facile synthesis and nanoparticles–nanowires sizes correlation

International Nuclear Information System (INIS)

Ruffino, F.; Grimaldi, M. G.

2013-01-01

We report a solid-state synthesis for SiO 2 nanowires (NWs) (up to 20 microns in length and from about 40 to about 150 nm in diameter) coated by Au nanoparticles (NPs) (from about 20 to about 80 nm in diameter). This protocol is based on three steps: (1) large area production of very long SiO 2 NWs on a Si surface exploiting a simple Au/Si solid-state reaction at high temperature; (2) coating of the SiO 2 NWs by a Au film of desired thickness using sputtering depositions; and (3) a thermal process to induce a dewetting process of the Au-film coating the SiO 2 NWs to obtain Au NPs on the curved surface of the NWs. The morphology evolution of the SiO 2 NWs was followed, in each step, by scanning electron microscopy analyses. They allowed to correlate the evolution of the NPs size with the NWs sizes for different thicknesses of the starting Au-film coating the NWs and different annealing temperatures of the dewetting process. Some theoretical concepts, related to the dewetting process of a film on a curved surface were used to describe the experimental data. The main advantages of the proposed protocols include: (i) simplicity and low-cost (it is based only on sputtering depositions and thermal processes), and (ii) versatility based on the possibility of tuning Au-film thickness and annealing temperature to tune the NPs–NWs sizes ratio. These advantages can make this technique suitable for the mass production of Au NPs-coated SiO 2 NWs toward applications in electronic devices, biosensors, and nanoscale optical devices

Solid-state dewetting of continuous thin platinum coatings

Energy Technology Data Exchange (ETDEWEB)

Hanief, N. [University of Cape Town, Private Bag X3, Rondebosch 7701 (South Africa); Topić, M.; Pineda-Vargas, C. [iThemba LABS, National Research Foundation, P.O. Box 722, Somerset West (South Africa)

2015-11-15

Thermal stability of coatings is of crucial importance for reliability of electronic devices operating at high temperature. Thus, we investigated the Cr–Pt system where a thin platinum coating of 0.1 μm was deposited on chromium substrate and annealed at 1000 °C for 8 h. The scanning electron microscope (SEM) showed that a continuous and uniformly deposited Pt coating experienced the formation of “islands” after annealing. The grain-boundary grooving, dewetting and agglomeration were the main mechanisms of degradation of thermally annealed coatings. Results by μ-PIXE (particle-induced X-ray emission) and transmission electron microscope (TEM) showed the presence of Cr{sub 3}Pt phase in “islands” and the coating thickness was approximately 0.5 μm. The surrounding regions were left uncovered due to coating agglomeration at the expense of initially deposited coating.

Structure Formation of Ultrathin PEO Films at Solid Interfaces—Complex Pattern Formation by Dewetting and Crystallization

Directory of Open Access Journals (Sweden)

Hans-Georg Braun

2013-02-01

Full Text Available The direct contact of ultrathin polymer films with a solid substrate may result in thin film rupture caused by dewetting. With crystallisable polymers such as polyethyleneoxide (PEO, molecular self-assembly into partial ordered lamella structures is studied as an additional source of pattern formation. Morphological features in ultrathin PEO films (thickness < 10 nm result from an interplay between dewetting patterns and diffusion limited growth pattern of ordered lamella growing within the dewetting areas. Besides structure formation of hydrophilic PEO molecules, n-alkylterminated (hydrophobic PEO oligomers are investigated with respect to self-organization in ultrathin films. Morphological features characteristic for pure PEO are not changed by the presence of the n-alkylgroups.

Dewetting of thin liquid films on chemically patterned substrates : front propatation along narrow lyophobic stripes and stripe arrays

NARCIS (Netherlands)

Brasjen, B.J.; Gu, H.; Darhuber, A.A.

2013-01-01

Using experiments and numerical simulations, we investigate the dewetting of thin liquid films on chemically patterned substrates. The patterns consist of long and narrow hydrophobic stripes, separated by larger hydrophilic domains. We characterize the morphology and dynamics of the dewetting front

Directed ordering of phase separated domains and dewetting of thin polymer blend films on a topographically patterned substrate.

Science.gov (United States)

Bhandaru, Nandini; Karim, Alamgir; Mukherjee, Rabibrata

2017-07-21

Substrate pattern guided self-organization of ultrathin and confined polymeric films on a topographically patterned substrate is a useful approach for obtaining ordered meso and nano structures over large areas, particularly if the ordering is achieved during film preparation itself, eliminating any post-processing such as thermal or solvent vapor annealing. By casting a dilute solution of two immiscible polymers, polystyrene (PS) and polymethylmethacrylate (PMMA), from a common solvent (toluene) on a topographically patterned substrate with a grating geometry, we show the formation of self-organized meso patterns with various degrees of ordering. The morphology depends on both the concentration of the dispensed solution (C n ) and the blend composition (R B ). Depending on the extent of dewetting during spin coating, the final morphologies can be classified into three distinct categories. At a very low C n the solution dewets fully, resulting in isolated polymer droplets aligned along substrate grooves (Type 1). Type 2 structures comprising isolated threads with aligned phase separated domains along each substrate groove are observed at intermediate C n . A continuous film (Type 3) is obtained above a critical concentration (C n *) that depends on R B . While the extent of ordering of the domains gradually diminishes with an increase in film thickness for Type 3 patterns, the size of the domains remains much smaller than that on a flat substrate, resulting in significant downsizing of the features due to the lateral confinement imposed on the phase separation process by the topographic patterns. Finally, we show that some of these structures exhibit excellent broadband anti-reflection (AR) properties.

In-situ investigation of thermal instabilities and solid state dewetting in polycrystalline platinum thin films via confocal laser microscopy

Energy Technology Data Exchange (ETDEWEB)

Jahangir, S.; Cheng, Xuan; Huang, H. H.; Nagarajan, V. [School of Materials Science and Engineering, University of New South Wales, Sydney 2052 (Australia); Ihlefeld, J. [Electronic, Optical, and Nanomaterials Department, Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)

2014-10-28

Solid state dewetting and the subsequent morphological changes for platinum thin films grown on zinc oxide (ZnO) buffered (001) silicon substrates (Pt/ZnO/SiO{sub 2}/(001)Si system) is investigated under vacuum conditions via a custom-designed confocal laser microscope coupled with a laser heating system. Live imaging of thin film dewetting under a range of heating and quenching vacuum ambients reveals events including hillock formation, hole formation, and hole growth that lead to formation of a network of Pt ligaments, break up of Pt ligaments to individual islands and subsequent Pt islands shape reformation, in chronological fashion. These findings are corroborated by ex-situ materials characterization and quantitative electron microscopy analysis. A secondary hole formation via blistering before film rupture is revealed to be the critical stage, after which a rapid dewetting catastrophe occurs. This process is instantaneous and cannot be captured by ex-situ methods. Finally, an intermetallic phase forms at 900 °C and alters the morphology of Pt islands, suggesting a practical limit to the thermal environments that may be used for these platinized silicon wafers in vacuum conditions.

In-situ investigation of thermal instabilities and solid state dewetting in polycrystalline platinum thin films via confocal laser microscopy

International Nuclear Information System (INIS)

Jahangir, S.; Cheng, Xuan; Huang, H. H.; Nagarajan, V.; Ihlefeld, J.

2014-01-01

Solid state dewetting and the subsequent morphological changes for platinum thin films grown on zinc oxide (ZnO) buffered (001) silicon substrates (Pt/ZnO/SiO 2 /(001)Si system) is investigated under vacuum conditions via a custom-designed confocal laser microscope coupled with a laser heating system. Live imaging of thin film dewetting under a range of heating and quenching vacuum ambients reveals events including hillock formation, hole formation, and hole growth that lead to formation of a network of Pt ligaments, break up of Pt ligaments to individual islands and subsequent Pt islands shape reformation, in chronological fashion. These findings are corroborated by ex-situ materials characterization and quantitative electron microscopy analysis. A secondary hole formation via blistering before film rupture is revealed to be the critical stage, after which a rapid dewetting catastrophe occurs. This process is instantaneous and cannot be captured by ex-situ methods. Finally, an intermetallic phase forms at 900 °C and alters the morphology of Pt islands, suggesting a practical limit to the thermal environments that may be used for these platinized silicon wafers in vacuum conditions.

Micropatterned Surfaces for Atmospheric Water Condensation via Controlled Radical Polymerization and Thin Film Dewetting.

Science.gov (United States)

Wong, Ian; Teo, Guo Hui; Neto, Chiara; Thickett, Stuart C

2015-09-30

Inspired by an example found in nature, the design of patterned surfaces with chemical and topographical contrast for the collection of water from the atmosphere has been of intense interest in recent years. Herein we report the synthesis of such materials via a combination of macromolecular design and polymer thin film dewetting to yield surfaces consisting of raised hydrophilic bumps on a hydrophobic background. RAFT polymerization was used to synthesize poly(2-hydroxypropyl methacrylate) (PHPMA) of targeted molecular weight and low dispersity; spin-coating of PHPMA onto polystyrene films produced stable polymer bilayers under appropriate conditions. Thermal annealing of these bilayers above the glass transition temperature of the PHPMA layer led to complete dewetting of the top layer and the formation of isolated PHPMA domains atop the PS film. Due to the vastly different rates of water nucleation on the two phases, preferential dropwise nucleation of water occurred on the PHPMA domains, as demonstrated by optical microscopy. The simplicity of the preparation method and ability to target polymers of specific molecular weight demonstrate the value of these materials with respect to large-scale water collection devices or other materials science applications where patterning is required.

Efficient Photocatalytic H2 Evolution: Controlled Dewetting-Dealloying to Fabricate Site-Selective High-Activity Nanoporous Au Particles on Highly Ordered TiO2 Nanotube Arrays.

Science.gov (United States)

Nguyen, Nhat Truong; Altomare, Marco; Yoo, JeongEun; Schmuki, Patrik

2015-05-27

Anodic self-organized TiO2 nanostumps are formed and exploited for self-ordering dewetting of Au-Ag sputtered films. This forms ordered particle configurations at the tube top (crown position) or bottom (ground position). By dealloying from a minimal amount of noble metal, porous Au nanoparticles are then formed, which, when in the crown position, allow for a drastically improved photocatalytic H2 production compared with nanoparticles produced by conventional dewetting processes. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Influence of germanium on thermal dewetting and agglomeration of the silicon template layer in thin silicon-on-insulator

International Nuclear Information System (INIS)

Zhang, P P; Yang, B; Rugheimer, P P; Roberts, M M; Savage, D E; Lagally, M G; Liu Feng

2009-01-01

We investigate the influence of heteroepitaxially grown Ge on the thermal dewetting and agglomeration of the Si(0 0 1) template layer in ultrathin silicon-on-insulator (SOI). We show that increasing Ge coverage gradually destroys the long-range ordering of 3D nanocrystals along the (1 3 0) directions and the 3D nanocrystal shape anisotropy that are observed in the dewetting and agglomeration of pure SOI(0 0 1). The results are qualitatively explained by Ge-induced bond weakening and decreased surface energy anisotropy. Ge lowers the dewetting and agglomeration temperature to as low as 700 0 C.

Au nanoparticles decorated SiO{sub 2} nanowires by dewetting on curved surfaces: facile synthesis and nanoparticles-nanowires sizes correlation

Energy Technology Data Exchange (ETDEWEB)

Ruffino, F., E-mail: francesco.ruffino@ct.infn.it; Grimaldi, M. G. [Universita di Catania, Dipartimento di Fisica e Astronomia (Italy)

2013-09-15

We report a solid-state synthesis for SiO{sub 2} nanowires (NWs) (up to 20 microns in length and from about 40 to about 150 nm in diameter) coated by Au nanoparticles (NPs) (from about 20 to about 80 nm in diameter). This protocol is based on three steps: (1) large area production of very long SiO{sub 2} NWs on a Si surface exploiting a simple Au/Si solid-state reaction at high temperature; (2) coating of the SiO{sub 2} NWs by a Au film of desired thickness using sputtering depositions; and (3) a thermal process to induce a dewetting process of the Au-film coating the SiO{sub 2} NWs to obtain Au NPs on the curved surface of the NWs. The morphology evolution of the SiO{sub 2} NWs was followed, in each step, by scanning electron microscopy analyses. They allowed to correlate the evolution of the NPs size with the NWs sizes for different thicknesses of the starting Au-film coating the NWs and different annealing temperatures of the dewetting process. Some theoretical concepts, related to the dewetting process of a film on a curved surface were used to describe the experimental data. The main advantages of the proposed protocols include: (i) simplicity and low-cost (it is based only on sputtering depositions and thermal processes), and (ii) versatility based on the possibility of tuning Au-film thickness and annealing temperature to tune the NPs-NWs sizes ratio. These advantages can make this technique suitable for the mass production of Au NPs-coated SiO{sub 2} NWs toward applications in electronic devices, biosensors, and nanoscale optical devices.

Graphene Oxide Monolayer as a Compatibilizer at the Polymer-Polymer Interface for Stabilizing Polymer Bilayer Films against Dewetting.

Science.gov (United States)

Kim, Tae-Ho; Kim, Hyeri; Choi, Ki-In; Yoo, Jeseung; Seo, Young-Soo; Lee, Jeong-Soo; Koo, Jaseung

2016-12-06

We investigate the effect of adding graphene oxide (GO) sheets at the polymer-polymer interface on the dewetting dynamics and compatibility of immiscible polymer bilayer films. GO monolayers are deposited at the poly(methyl methacrylate) (PMMA)-polystyrene (PS) interface by the Langmuir-Schaefer technique. GO monolayers are found to significantly inhibit the dewetting behavior of both PMMA films (on PS substrates) and PS films (on PMMA substrates). This can be interpreted in terms of an interfacial interaction between the GO sheets and these polymers, which is evidenced by the reduced contact angle of the dewet droplets. The favorable interaction of GO with both PS and PMMA facilitates compatibilization of the immiscible polymer bilayer films, thereby stabilizing their bilayer films against dewetting. This compatibilization effect is verified by neutron reflectivity measurements, which reveal that the addition of GO monolayers broadens the interface between PS and the deuterated PMMA films by 2.2 times over that of the bilayer in the absence of GO.

Inorganic Surface Coating with Fast Wetting-Dewetting Transitions for Liquid Manipulations.

Science.gov (United States)

Yang, Yajie; Zhang, Liaoliao; Wang, Jue; Wang, Xinwei; Duan, Libing; Wang, Nan; Xiao, Fajun; Xie, Yanbo; Zhao, Jianlin

2018-06-06

Liquid manipulation is a fundamental issue for microfluidics and miniaturized sensors. Fast wetting-state transitions by optical methods have proven being efficient for liquid manipulations by organic surface coatings, however rarely been achieved by using inorganic coatings. Here, we report a fast optical-induced wetting-state transition surface achieved by inorganic coating, enabling tens of second transitions for a wetting-dewetting cycle, shortened from an hour, as typically reported. Here, we demonstrate a gravity-driven microfluidic reactor and switch it to a mixer after a second-step exposure in a minimum of within 80 s of UV exposure. The fast wetting-dewetting transition surfaces enable the fast switchable or erasable smart surfaces for water collection, miniature chemical reaction, or sensing systems by using inorganic surface coatings.

Dewetting and spreading transitions for active matter on random pinning substrates.

Science.gov (United States)

Sándor, Cs; Libál, A; Reichhardt, C; Olson Reichhardt, C J

2017-05-28

We show that sterically interacting self-propelled disks in the presence of random pinning substrates exhibit transitions among a variety of different states. In particular, from a phase separated cluster state, the disks can spread out and homogeneously cover the substrate in what can be viewed as an example of an active matter wetting transition. We map the location of this transition as a function of activity, disk density, and substrate strength, and we also identify other phases including a cluster state, coexistence between a cluster and a labyrinth wetted phase, and a pinned liquid. Convenient measures of these phases include the cluster size, which dips at the wetting-dewetting transition, and the fraction of sixfold coordinated particles, which drops when dewetting occurs.

Raman and photoluminescence spectroscopy of SiGe layer evolution on Si(100) induced by dewetting

Science.gov (United States)

Shklyaev, A. A.; Volodin, V. A.; Stoffel, M.; Rinnert, H.; Vergnat, M.

2018-01-01

High temperature annealing of thick (40-100 nm) Ge layers deposited on Si(100) at ˜400 °C leads to the formation of continuous films prior to their transformation into porous-like films due to dewetting. The evolution of Si-Ge composition, lattice strain, and surface morphology caused by dewetting is analyzed using scanning electron microscopy, Raman, and photoluminescence (PL) spectroscopies. The Raman data reveal that the transformation from the continuous to porous film proceeds through strong Si-Ge interdiffusion, reducing the Ge content from 60% to about 20%, and changing the stress from compressive to tensile. We expect that Ge atoms migrate into the Si substrate occupying interstitial sites and providing thereby the compensation of the lattice mismatch. Annealing generates only one type of radiative recombination centers in SiGe resulting in a PL peak located at about 0.7 and 0.8 eV for continuous and porous film areas, respectively. Since annealing leads to the propagation of threading dislocations through the SiGe/Si interface, we can tentatively associate the observed PL peak to the well-known dislocation-related D1 band.

Effect of argon implantation on solid-state dewetting: control of size and surface density of silicon nanocrystals.

Science.gov (United States)

Almadori, Y; Borowik, Ł; Chevalier, N; Barbé, J-C

2017-01-27

Thermally induced solid-state dewetting of ultra-thin films on insulators is a process of prime interest, since it is capable of easily forming nanocrystals. If no particular treatment is performed to the film prior to the solid-state dewetting, it is already known that the size, the shape and the density of nanocrystals is governed by the initial film thickness. In this paper, we report a novel approach to control the size and the surface density of silicon nanocrystals based on an argon-implantation preliminary surface treatment. Using 7.5 nm thin layers of silicon, we show that increasing the implantation dose tends to form smaller silicon nanocrystals with diameter and height lower than 50 nm and 30 nm, respectively. Concomitantly, the surface density is increased by a factor greater than 20, going from 5 μm -2 to values over 100 μm -2 .

Theory Of Dewetting In A Filled Elastomer Under Stress

Science.gov (United States)

Peng, Steven T. J.

1993-01-01

Report presents theoretical study of dewetting between elastomeric binder and filler particles of highly filled elastomer under multiaxial tension and resulting dilatation of elastomer. Study directed toward understanding and predicting nonlinear stress-vs.-strain behavior of filled elastomeric rocket propellant, also applicable to rubber in highly loaded tire or in damping pad.

Critical point dewetting: competition between the gravity and the dispersion force

International Nuclear Information System (INIS)

Ohmasa, Y; Takahashi, S; Fujii, K; Yao, M

2008-01-01

Near the critical temperature of an immiscible binary liquid system, a solid substrate is usually covered completely by one of the liquid phases. This phenomenon is called the 'critical point wetting , which is predicted by Cahn in 1977, and have been confirmed for many fluid systems experimentally. However, we found that liquid Se-Tl system on a quartz substrate does not show the critical point wetting near the liquid-liquid critical point. On a contrary, when the temperature goes down from the critical point, a Se-rich wetting film intrudes between the Tl-rich bulk liquid and the quartz wall. This result is a clear evidence of the 'critical point dewetting' phenomenon. It is suggested from a theoretical consideration that the critical point dewetting takes place as a result of the competition between the long-range dispersion force and the gravity

Unusual dewetting of thin polymer films in liquid media containing a poor solvent and a nonsolvent.

Science.gov (United States)

Xu, Lin; Sharma, Ashutosh; Joo, Sang Woo; Liu, Hui; Shi, Tongfei

2014-12-16

We investigate the control of pattern size and kinetics in spontaneous dewetting of thin polymer films (polystyrene) that are stable to thermal annealing by annealing in a poor solvent (acetone)/nonsolvent (ethanol or n-hexane) liquid mixture. Dewetting occurs by the formation and growth of circular holes that coalesce to form droplets. The influence of the nature and the volume fraction of the nonsolvents on the contact angle of polymer droplets, number density of holes, and the kinetics of holes formation and growth is studied. Addition of ethanol greatly increases the hole density and slows down the kinetics substantially, while affecting only a small change in wettability. n-Hexane addition shows an interesting nonmonotonic response in decreasing the hole density and contact angle in the volume fraction range of 0-0.3 but an opposite effect beyond that. Although the two nonsolvents chosen cannot by themselves induce dewetting, their relative affinity for the solid substrate vis-à-vis acetone can strongly influence the observed dewetting scenarios that are not understood by the existing theoretical considerations. n-Hexane, for example, has great affinity for silicon substrate. In addition to the changes in wettability, viscosity, and film interfacial tension engendered by the nonsolvents, the possibility of the formation of adsorbed liquid layers at the substrate-polymer interface, which can modify the interfacial friction and slippage, needs to be considered.

Self-organization of yeast cells on modified polymer surfaces after dewetting: new perspectives in cellular patterning

Energy Technology Data Exchange (ETDEWEB)

Carnazza, S [Department of Microbiological, Genetic and Molecular Sciences, University of Messina, Messina (Italy); Satriano, S [Department of Chemical Sciences, University of Catania, Catania (Italy); Guglielmino, S [Department of Microbiological, Genetic and Molecular Sciences, University of Messina, Messina (Italy)

2006-08-23

In recent years, biological micro-electro-mechanical systems (commonly referred to as BioMEMS) have found widespread use, becoming increasingly prevalent in diagnostics and therapeutics. Cell-based sensors are nowadays gaining increasing attention, due to cellular built-in natural selectivity and physiologically relevant response to biologically active chemicals. On the other hand, surrogate microbial systems, including yeast models, have become a useful alternative to animal and mammalian cell systems for high-throughput screening for the identification of new pharmacological agents. A main obstacle in biosensor device fabrication is the need for localized geometric confinement of cells, without losing cell viability and sensing capability. Here we illustrate a new approach for cellular patterning using dewetting processes to control cell adhesion and spatial confinement on modified surfaces. By the control of simple system parameters, a rich variety of morphologies, ranging through hexagonal arrays, polygonal networks, bicontinuous structures, and elongated fingers, can be obtained.

Solid state dewetting and stress relaxation in a thin single crystalline Ni film on sapphire

International Nuclear Information System (INIS)

Rabkin, E.; Amram, D.; Alster, E.

2014-01-01

In this study, we deposited a 80 nm thick single crystalline Ni film on a sapphire substrate. Heat treatment of this film at 1000 °C followed by slow cooling resulted in the formation of faceted holes, star-like channel instabilities and faceted microwires. The ridges at the rims of faceted holes and channels exhibited a twinning orientation relationship with the rest of the film. A sub-nanometer-high hexagonal topography pattern on the surface of the unperturbed film was observed by atomic force microscopy. No such pattern was observed on the top facets of isolated Ni particles and hole ridges. We discuss the observed dewetting patterns in terms of the effects of Ni surface anisotropy and faceting on solid state dewetting. The hexagonal pattern on the surface of the unperturbed film was attributed to thermal stress relaxation in the film via dislocations glide. This work demonstrates that solid state dewetting of single crystalline metal films can be utilized for film patterning and for producing hierarchical surface topographies

Self-assembly of bimetallic AuxPd1-x alloy nanoparticles via dewetting of bilayers through the systematic control of temperature, thickness, composition and stacking sequence

Science.gov (United States)

Kunwar, Sundar; Pandey, Puran; Sui, Mao; Bastola, Sushil; Lee, Jihoon

2018-03-01

Bimetallic alloy nanoparticles (NPs) are attractive materials for various applications with their morphology and elemental composition dependent optical, electronic, magnetic and catalytic properties. This work demonstrates the evolution of AuxPd1-x alloy nanostructures by the solid-state dewetting of sequentially deposited bilayers of Au and Pd on sapphire (0001). Various shape, size and configuration of AuxPd1‑x alloy NPs are fabricated by the systematic control of annealing temperature, deposition thickness, composition as well as stacking sequence. The evolution of alloy nanostructures is attributed to the surface diffusion, interface diffusion between bilayers, surface and interface energy minimization, Volmer-Weber growth model and equilibrium configuration. Depending upon the temperature, the surface morphologies evolve with the formation of pits, grains and voids and gradually develop into isolated semi-spherical alloy NPs by the expansion of voids and agglomeration of Au and Pd adatoms. On the other hand, small isolated to enlarged elongated and over-grown layer-like alloy nanostructures are fabricated due to the coalescence, partial diffusion and inter-diffusion with the increased bilayer thickness. In addition, the composition and stacking sequence of bilayers remarkably affect the final geometry of AuxPd1‑x nanostructures due to the variation in the dewetting process. The optical analysis based on the UV–vis-NIR reflectance spectra reveals the surface morphology dependent plasmonic resonance, scattering, reflection and absorption properties of AuxPd1‑x alloy nanostructures.

Solid-state dewetting of single- and bilayer Au-W thin films: Unraveling the role of individual layer thickness, stacking sequence and oxidation on morphology evolution

Directory of Open Access Journals (Sweden)

A. Herz

2016-03-01

Full Text Available Self-assembly of ultrathin Au, W, and Au-W bilayer thin films is investigated using a rapid thermal annealing technique in an inert ambient. The solid-state dewetting of Au films is briefly revisited in order to emphasize the role of initial film thickness. W films deposited onto SiO2 evolve into needle-like nanocrystals rather than forming particle-like agglomerates upon annealing at elevated temperatures. Transmission electron microscopy reveals that such nanocrystals actually consist of tungsten (VI oxide (WO3 which is related to an anisotropic oxide crystal growth out of the thin film. The evolution of W films is highly sensitive to the presence of any residual oxygen. Combination of both the dewetting of Au and the oxide crystal growth of WO3 is realized by using various bilayer film configurations of the immiscible Au and W. At low temperature, Au dewetting is initiated while oxide crystal growth is still suppressed. Depending on the stacking sequence of the Au-W bilayer thin film, W acts either as a substrate or as a passivation layer for the dewetting of Au. Being the ground layer, W changes the wettability of Au which clearly modifies its initial state for the dewetting. Being the top layer, W prevents Au from dewetting regardless of Au film thickness. Moreover, regular pattern formation of Au-WO3 nanoparticles is observed at high temperature demonstrating how bilayer thin film dewetting can create unique nanostructure arrangements.

Solid-state dewetting of single- and bilayer Au-W thin films: Unraveling the role of individual layer thickness, stacking sequence and oxidation on morphology evolution

Energy Technology Data Exchange (ETDEWEB)

Herz, A., E-mail: andreas.herz@tu-ilmenau.de, E-mail: dong.wang@tu-ilmenau.de; Franz, A.; Theska, F.; Hentschel, M.; Kups, Th.; Wang, D., E-mail: andreas.herz@tu-ilmenau.de, E-mail: dong.wang@tu-ilmenau.de; Schaaf, P. [Department of Materials for Electronics and Electrical Engineering, Institute of Materials Science and Engineering and Institute of Micro- and Nanotechnologies MacroNano, TU Ilmenau, D-98693 Ilmenau (Germany)

2016-03-15

Self-assembly of ultrathin Au, W, and Au-W bilayer thin films is investigated using a rapid thermal annealing technique in an inert ambient. The solid-state dewetting of Au films is briefly revisited in order to emphasize the role of initial film thickness. W films deposited onto SiO{sub 2} evolve into needle-like nanocrystals rather than forming particle-like agglomerates upon annealing at elevated temperatures. Transmission electron microscopy reveals that such nanocrystals actually consist of tungsten (VI) oxide (WO{sub 3}) which is related to an anisotropic oxide crystal growth out of the thin film. The evolution of W films is highly sensitive to the presence of any residual oxygen. Combination of both the dewetting of Au and the oxide crystal growth of WO{sub 3} is realized by using various bilayer film configurations of the immiscible Au and W. At low temperature, Au dewetting is initiated while oxide crystal growth is still suppressed. Depending on the stacking sequence of the Au-W bilayer thin film, W acts either as a substrate or as a passivation layer for the dewetting of Au. Being the ground layer, W changes the wettability of Au which clearly modifies its initial state for the dewetting. Being the top layer, W prevents Au from dewetting regardless of Au film thickness. Moreover, regular pattern formation of Au-WO{sub 3} nanoparticles is observed at high temperature demonstrating how bilayer thin film dewetting can create unique nanostructure arrangements.

Coexistence of Two Singularities in Dewetting Flows: Regularizing the Corner Tip

NARCIS (Netherlands)

Peters, I.R.; Snoeijer, Jacobus Hendrikus; Daerr, Adrian; Limat, Laurent

2009-01-01

Entrainment in wetting and dewetting flows often occurs through the formation of a corner with a very sharp tip. This corner singularity comes on top of the divergence of viscous stress near the contact line, which is only regularized at molecular scales. We investigate the fine structure of corners

Dewetting-mediated pattern formation inside the coffee ring

Science.gov (United States)

Li, Weibin; Lan, Ding; Wang, Yuren

2017-04-01

The rearrangement of particles in the final stage of droplet evaporation has been investigated by utilizing differential interference contrast microscopy and the formation mechanism of a network pattern inside a coffee ring has been revealed. A tailored substrate with a circular hydrophilic domain is prepared to obtain thin liquid film containing monolayer particles. Real-time bottom-view images show that the evolution of a dry patch could be divided into three stages: rupture initiation, dry patch expansion, and drying of the residual liquid. A growing number of dry patches will repeat these stages to form the network patterns inside the ringlike stain. It can be shown that the suction effect promotes the rupture of the liquid film and the formation of the dry patch. The particle-assembling process is totally controlled by the liquid film dewetting and dominated by the surface tension of the liquid film, which eventually determine the ultimate deposition patterns.

Phenomenological understanding of dewetting and embedding of noble metal nanoparticles in thin films induced by ion irradiation

Energy Technology Data Exchange (ETDEWEB)

Prakash, Jai, E-mail: jai.gupta1983@gmail.com [Department of Chemistry, MMH College (Ch. Charan Singh University Meerut), Ghaiziabad 201001 (India); Chemical Physics of Materials, Université Libre de Bruxelles, Campus de la Plaine, CP 243, B-1050 Bruxelles (Belgium); Tripathi, A. [Inter University Accelerator Centre, Aruna Asif Ali Marg, New Delhi 110067 (India); Gautam, Sanjeev; Chae, K.H.; Song, Jonghan [Advanced Analysis Center, Korea Institute of Science and Technology, Seoul 136–791 (Korea, Republic of); Rigato, V. [INFN Laboratori Nazionali di Legnaro, Via Romea. 4, 35020 Legnaro, Padova (Italy); Tripathi, Jalaj [Department of Chemistry, MMH College (Ch. Charan Singh University Meerut), Ghaiziabad 201001 (India); Asokan, K. [Inter University Accelerator Centre, Aruna Asif Ali Marg, New Delhi 110067 (India)

2014-10-15

The present experimental work provides the phenomenological approach to understand the dewetting in thin noble metal films with subsequent formation of nanoparticles (NPs) and embedding of NPs induced by ion irradiation. Au/polyethyleneterepthlate (PET) bilayers were irradiated with 150 keV Ar ions at varying fluences and were studied using scanning electron microscopy (SEM) and cross-sectional transmission electron microscopy (X-TEM). Thin Au film begins to dewet from the substrate after irradiation and subsequent irradiation results in spherical nanoparticles on the surface that at a fluence of 5 × 10{sup 16} ions/cm{sup 2} become embedded into the substrate. In addition to dewetting in thin films, synthesis and embedding of metal NPs by ion irradiation, the present article explores fundamental thermodynamic principles that govern these events systematically under the effect of irradiation. The results are explained on the basis of ion induced sputtering, thermal spike inducing local melting and of thermodynamic driving forces by minimization of the system free energy where contributions of surface and interfacial energies are considered with subsequent ion induced viscous flow in substrate. - Highlights: • Phenomenological interpretation of dewetting and embedding of metal NPs in thin film. • Exploring fundamental thermodynamic principles under influence of ion irradiation. • Ion induced surface/interface microstructural changes using SEM/X-TEM. • Ion induced sputtering, thermal spike induced local melting. • Thermodynamic driving forces relate to surface and interfacial energies.

A novel approach to fabricate dye-encapsulated polymeric micro- and nanoparticles by thin film dewetting technique.

Science.gov (United States)

Chatterjee, Manosree; Hens, Abhiram; Mahato, Kuldeep; Jaiswal, Namita; Mahato, Nivedita; Nagahanumaiah; Chanda, Nripen

2017-11-15

A new method is reported for fabrication of polymeric micro- and nanoparticles from an intermediate patterned surface originated by dewetting of a polymeric thin film. Poly (d, l-lactide-co-glycolide) or PLGA, a biocompatible polymer is used to develop a thin film over a clean glass substrate which dewets spontaneously in the micro-/nano-patterned surface of size range 50nm to 3.5µm. Since another water-soluble polymer, poly vinyl alcohol (PVA) is coated on the same glass substrate before PLGA thin film formation, developed micro-/nano-patterns are easily extracted in water in the form of micro- and nanoparticle mixture of size range 50nm to 3.0µm. This simplified method is also used to effectively encapsulate a dye molecule, rhodamine B inside the PLGA micro-/nanoparticles. The developed dye-encapsulated nanoparticles, PLGA-rhodamine are separated from the mixture and tested for in-vitro delivery application of external molecules inside human lung cancer cells. For the first time, the use of thin film dewetting technique is reported as a potential route for the synthesis of polymeric micro-/nanoparticles and effective encapsulation of external species therein. Copyright © 2017 Elsevier Inc. All rights reserved.

Apparent de-wetting due to superfluid flow

CERN Document Server

Poujade, M; Rolley, E

2002-01-01

We have investigated the wetting behaviour of superfluid helium-4 on silicon. Surprisingly, we observe pseudo-de-wetting: though a thick superfluid film covers the substrate, the meniscus displays a finite contact angle which decreases from about 5 deg C at low temperature down to zero at the superfluid transition. We show that this behaviour can be explained by a pressure decrease due to a superfluid flow, closely related to the Kontorovich effect. (authors)

Dynamic Chemically Driven Dewetting, Spreading, and Self-Running of Sessile Droplets on Crystalline Silicon.

Science.gov (United States)

Arscott, Steve

2016-12-06

A chemically driven dewetting effect is demonstrated using sessile droplets of dilute hydrofluoric acid on chemically oxidized silicon wafers. The dewetting occurs as the thin oxide is slowly etched by the droplet and replaced by a hydrogen-terminated surface; the result of this is a gradual increase in the contact angle of the droplet with time. The time-varying work of adhesion is calculated from the time-varying contact angle; this corresponds to the changing chemical nature of the surface during dewetting and can be modeled by the well-known logistic (sigmoid) function often used for the modeling of restricted growth, in this case, the transition from an oxidized surface to a hydrogen-terminated silicon surface. The observation of the time-varying contact angle allows one to both measure the etch rate of the silicon oxide and estimate the hydrogenation rate as a function of HF concentration and wafer type. In addition to this, at a certain HF concentration, a self-running droplet effect is observed. In contrast, on hydrogen-terminated silicon wafers, a chemically induced spreading effect is observed using sessile droplets of nitric acid. The droplet spreading can also be modeled using a logistical function, where the restricted growth is the transition from hydrogen-terminated to a chemically induced oxidized silicon surface. The chemically driven dewetting and spreading observed here add to the methods available to study dynamic wetting (e.g., the moving three-phase contact line) of sessile droplets on surfaces. By slowing down chemical kinetics of the wetting, one is able to record the changing profile of the sessile droplet with time and gather information concerning the time-varying surface chemistry. The data also indicates a chemical interface hysteresis (CIH) that is compared to contact angle hysteresis (CAH). The approach can also be used to study the chemical etching and deposition behavior of thin films using liquids by monitoring the macroscopic

A parametric finite element method for solid-state dewetting problems with anisotropic surface energies

Science.gov (United States)

Bao, Weizhu; Jiang, Wei; Wang, Yan; Zhao, Quan

2017-02-01

We propose an efficient and accurate parametric finite element method (PFEM) for solving sharp-interface continuum models for solid-state dewetting of thin films with anisotropic surface energies. The governing equations of the sharp-interface models belong to a new type of high-order (4th- or 6th-order) geometric evolution partial differential equations about open curve/surface interface tracking problems which include anisotropic surface diffusion flow and contact line migration. Compared to the traditional methods (e.g., marker-particle methods), the proposed PFEM not only has very good accuracy, but also poses very mild restrictions on the numerical stability, and thus it has significant advantages for solving this type of open curve evolution problems with applications in the simulation of solid-state dewetting. Extensive numerical results are reported to demonstrate the accuracy and high efficiency of the proposed PFEM.

Formation of precise 2D Au particle arrays via thermally induced dewetting on pre-patterned substrates

Directory of Open Access Journals (Sweden)

Dong Wang

2011-06-01

Full Text Available The fabrication of precise 2D Au nanoparticle arrays over a large area is presented. The technique was based on pre-patterning of the substrate before the deposition of a thin Au film, and the creation of periodic particle arrays by subsequent dewetting induced by annealing. Two types of pre-patterned substrates were used: The first comprised an array of pyramidal pits and the second an array of circular holes. For the dewetting of Au films on the pyramidal pit substrate, the structural curvature-driven diffusion cooperates with capillarity-driven diffusion, resulting in the formation of precise 2D particle arrays for films within a structure dependent thickness-window. For the dewetting of Au films on the circular hole substrate, the periodic discontinuities in the films, induced by the deposition, can limit the diffusion paths and lead to the formation of one particle per individual separated region (holes or mesas between holes, and thus, result in the evolution of precise 2D particle arrays. The influence of the pre-patterned structures and the film thickness is analyzed and discussed. For both types of pre-patterned substrate, the Au film thickness had to be adjusted in a certain thickness-window in order to achieve the precise 2D particle arrays.

Formation of precise 2D Au particle arrays via thermally induced dewetting on pre-patterned substrates

Science.gov (United States)

Ji, Ran

2011-01-01

Summary The fabrication of precise 2D Au nanoparticle arrays over a large area is presented. The technique was based on pre-patterning of the substrate before the deposition of a thin Au film, and the creation of periodic particle arrays by subsequent dewetting induced by annealing. Two types of pre-patterned substrates were used: The first comprised an array of pyramidal pits and the second an array of circular holes. For the dewetting of Au films on the pyramidal pit substrate, the structural curvature-driven diffusion cooperates with capillarity-driven diffusion, resulting in the formation of precise 2D particle arrays for films within a structure dependent thickness-window. For the dewetting of Au films on the circular hole substrate, the periodic discontinuities in the films, induced by the deposition, can limit the diffusion paths and lead to the formation of one particle per individual separated region (holes or mesas between holes), and thus, result in the evolution of precise 2D particle arrays. The influence of the pre-patterned structures and the film thickness is analyzed and discussed. For both types of pre-patterned substrate, the Au film thickness had to be adjusted in a certain thickness-window in order to achieve the precise 2D particle arrays. PMID:21977445

Synergism of Dewetting and Self-Wrinkling To Create Two-Dimensional Ordered Arrays of Functional Microspheres.

Science.gov (United States)

Han, Xue; Hou, Jing; Xie, Jixun; Yin, Jian; Tong, Yi; Lu, Conghua; Möhwald, Helmuth

2016-06-29

Here we report a simple, novel, yet robust nonlithographic method for the controlled fabrication of two-dimensional (2-D) ordered arrays of polyethylene glycol (PEG) microspheres. It is based on the synergistic combination of two bottom-up processes enabling periodic structure formation for the first time: dewetting and the mechanical wrinkle formation. The deterministic dewetting results from the hydrophilic polymer PEG on an incompatible polystyrene (PS) film bound to a polydimethylsiloxane (PDMS) substrate, which is directed both by a wrinkled template and by the template-directed in-situ self-wrinkling PS/PDMS substrate. Two strategies have been introduced to achieve synergism to enhance the 2-D ordering, i.e., employing 2-D in-situ self-wrinkling substrates and boundary conditions. As a result, we achieve highly ordered 2-D arrays of PEG microspheres with desired self-organized microstructures, such as the array location (e.g., selectively on the crest/in the valley of the wrinkles), diameter, spacing of the microspheres, and array direction. Additionally, the coordination of PEG with HAuCl4 is utilized to fabricate 2-D ordered arrays of functional PEG-HAuCl4 composite microspheres, which are further converted into different Au nanoparticle arrays. This simple versatile combined strategy could be extended to fabricate highly ordered 2-D arrays of other functional materials and achieve desirable properties and functionalities.

Room-temperature deposition of crystalline patterned ZnO films by confined dewetting lithography

International Nuclear Information System (INIS)

Sepulveda-Guzman, S.; Reeja-Jayan, B.; De la Rosa, E.; Ortiz-Mendez, U.; Reyes-Betanzo, C.; Cruz-Silva, R.; Jose-Yacaman, M.

2010-01-01

In this work patterned ZnO films were prepared at room-temperature by deposition of ∼5 nm size ZnO nanoparticles using confined dewetting lithography, a process which induces their assembly, by drying a drop of ZnO colloidal dispersion between a floating template and the substrate. Crystalline ZnO nanoparticles exhibit a strong visible (525 nm) light emission upon UV excitation (λ = 350 nm). The resulting films were characterized by scanning electron microscopy (SEM) and atomic force microscope (AFM). The method described herein presents a simple and low cost method to prepare crystalline ZnO films with geometric patterns without additional annealing. Such transparent conducting films are attractive for applications like light emitting diodes (LEDs). As the process is carried out at room temperature, the patterned crystalline ZnO films can even be deposited on flexible substrates.

Room-temperature deposition of crystalline patterned ZnO films by confined dewetting lithography

Energy Technology Data Exchange (ETDEWEB)

Sepulveda-Guzman, S., E-mail: selene.sepulvedagz@uanl.edu.mx [Centro de Innovacion, Investigacion y Desarrollo en Ingenieria y Tecnologia. UANL, PIIT Monterrey, CP 66629, Apodaca NL (Mexico); Reeja-Jayan, B. [Texas Materials Institute, University of Texas at Austin, Austin, TX 78712 (United States); De la Rosa, E. [Centro de Investigacion en Optica, Loma del Bosque 115 Col. Lomas del Campestre C.P. 37150 Leon, Gto. Mexico (Mexico); Ortiz-Mendez, U. [Centro de Innovacion, Investigacion y Desarrollo en Ingenieria y Tecnologia. UANL, PIIT Monterrey, CP 66629, Apodaca NL (Mexico); Reyes-Betanzo, C. [Instituto Nacional de Astrofisica Optica y Electronica, Calle Luis Enrique Erro No. 1, Santa Maria Tonanzintla, Puebla. Apdo. Postal 51 y 216, C.P. 72000 Puebla (Mexico); Cruz-Silva, R. [Centro de Investigacion en Ingenieria y Ciencias Aplicadas, UAEM. Av. Universidad 1001, Col. Chamilpa, CP 62210 Cuernavaca, Mor. (Mexico); Jose-Yacaman, M. [Physics and Astronomy Department University of Texas at San Antonio 1604 campus San Antonio, TX 78249 (United States)

2010-03-15

In this work patterned ZnO films were prepared at room-temperature by deposition of {approx}5 nm size ZnO nanoparticles using confined dewetting lithography, a process which induces their assembly, by drying a drop of ZnO colloidal dispersion between a floating template and the substrate. Crystalline ZnO nanoparticles exhibit a strong visible (525 nm) light emission upon UV excitation ({lambda} = 350 nm). The resulting films were characterized by scanning electron microscopy (SEM) and atomic force microscope (AFM). The method described herein presents a simple and low cost method to prepare crystalline ZnO films with geometric patterns without additional annealing. Such transparent conducting films are attractive for applications like light emitting diodes (LEDs). As the process is carried out at room temperature, the patterned crystalline ZnO films can even be deposited on flexible substrates.

Dewetting and Hydrophobic Interaction in Physical and Biological Systems

Science.gov (United States)

Berne, Bruce J.; Weeks, John D.; Zhou, Ruhong

2013-01-01

Hydrophobicity manifests itself differently on large and small length scales. This review focuses on large length scale hydrophobicity, particularly on dewetting at single hydrophobic surfaces and drying in regions bounded on two or more sides by hydrophobic surfaces. We review applicable theories, simulations and experiments pertaining to large scale hydrophobicity in physical and biomoleclar systems and clarify some of the critical issues pertaining to this subject. Given space constraints, we could not review all of the significant and interesting work in this very active field. PMID:18928403

Dynamic Wetting and Dewetting: Comparison of Experiment with Theories

Directory of Open Access Journals (Sweden)

Orlova Evgeniya.G.

2016-01-01

Full Text Available The dynamics wetting/dewetting of a metal surface by distilled water drop was studied experimentally. The advancing and receding dynamic contact angles were obtained as a function of a contact line speed. The hydrodynamic and molecular-kinetic models have been applied to the experimental data to interpret the obtained results. The independent variables of the molecular-kinetic and hydrodynamic models, and the determination coefficient were determined by fitting procedure. The receding contact angles are found to be fitted better to the wetting models in comparison with the advancing dynamic contact angles.

Crystallographic analysis of the solid-state dewetting of polycrystalline gold film using automated indexing in a transmission electron microscope

Energy Technology Data Exchange (ETDEWEB)

Jang, S. A.; Lee, H. J.; Oh, Y. J., E-mail: yjoh@hanbat.ac.kr [Department of Advanced Materials Science and Engineering, Hanbat National University, 125, Dongseo-daero, Yuseong-gu, Daejeon 305-719 (Korea, Republic of); Thompson, C. V.; Ross, C. A., E-mail: caross@mit.edu [Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

2015-12-01

We analyzed the effect of crystallographic anisotropy on the morphological evolution of a 12-nm-thick gold film during solid-state dewetting at high temperatures using automated indexing tool in a transmission electron microscopy. Dewetting initiated at grain-boundary triple junctions adjacent to large grains resulting from abnormal grain growth driven by (111) texture development. Voids at the junctions developed shapes with faceted edges bounded by low-index crystal planes. The kinetic mobility of the edges varied with the crystal orientation normal to the edges, with a predominance of specific edges with the slowest retraction rates as the annealing time was increased.

A dewetting route to grow heterostructured nanoparticles based on thin film heterojunctions.

Science.gov (United States)

Li, Junjie; Yin, Deqiang; Li, Qiang; Chen, Chunlin; Huang, Sumei; Wang, Zhongchang

2015-12-21

Heterostructured nanoparticles have received considerable attention for their various applications due to their unique and tunable functionalities with respect to their individual bulk constituents. However, the current wet chemical synthesis of multicomponent heterostructured nanoparticles is rather complicated. Here, we report a simple and quick method to fabricate Co-Au dumbbell arrays by dewetting Co/Au heterojunctions on a Si substrate and demonstrate that the Co-Au dumbbells vary in size from 2 to 28 nm. We further show by chemical mapping that Co bells are covered by a pseudomorphic Au wetting layer of ∼4 Å, preventing the bells from oxidation. By controlling the thickness of metal heterojunctions and the annealing time, the morphology of the Co-Au nanoparticle is found to be transformed from the dumbbell to the core shell. This facile route is demonstrated to be useful for fabricating other metal-metal and metal-oxide heterostructures and hence holds technological promise for functional applications.

Dewetting of thin film blends containing block copolymer: effects of nonadsorbing block length and substrate hydrophobicity

Czech Academy of Sciences Publication Activity Database

Costa, A. C.; Composto, R. J.; Vlček, Petr

2003-01-01

Roč. 36, č. 9 (2003), s. 3254-3260 ISSN 0024-9297 R&D Projects: GA AV ČR KSK4050111 Keywords : polymer films * adsorption * dewetting Subject RIV: CD - Macromolecular Chemistry Impact factor: 3.621, year: 2003

Solid-state dewetting and island morphologies in strongly anisotropic materials

International Nuclear Information System (INIS)

Jiang, Wei; Wang, Yan; Zhao, Quan; Srolovitz, David J.; Bao, Weizhu

2016-01-01

We propose a sharp-interface continuum model based on a thermodynamic variational approach to investigate the strong anisotropic effect on solid-state dewetting including contact line dynamics. For sufficiently strong surface energy anisotropy, we show that multiple equilibrium shapes may appear that cannot be described by the widely employed Winterbottom construction, i.e., the modified Wulff construction for an island on a substrate. We repair the Winterbottom construction to include multiple equilibrium shapes and employ our evolution model to demonstrate that all such shapes are dynamically accessible.

Crystallographic analysis of the solid-state dewetting of polycrystalline gold film using automated indexing in a transmission electron microscope

Directory of Open Access Journals (Sweden)

S. A. Jang

2015-12-01

Full Text Available We analyzed the effect of crystallographic anisotropy on the morphological evolution of a 12-nm-thick gold film during solid-state dewetting at high temperatures using automated indexing tool in a transmission electron microscopy. Dewetting initiated at grain-boundary triple junctions adjacent to large grains resulting from abnormal grain growth driven by (111 texture development. Voids at the junctions developed shapes with faceted edges bounded by low-index crystal planes. The kinetic mobility of the edges varied with the crystal orientation normal to the edges, with a predominance of specific edges with the slowest retraction rates as the annealing time was increased.

A study of growth and thermal dewetting behavior of ultra-thin gold films using transmission electron microscopy

Directory of Open Access Journals (Sweden)

Sudheer

2017-07-01

Full Text Available The growth and solid-state dewetting behavior of Au thin films (0.7 to 8.4 nm deposited on the formvar film (substrate by sputtering technique have been studied using transmission electron microscopy. The size and number density of the Au nanoparticles (NPs change with an increase in the film thickness (0.7 to 2.8 nm. Nearly spherical Au NPs are obtained for 6 nm show capability to be used as an irreversible temperature sensor with a sensitivity of ∼0.1 CAF/°C. It is observed that annealing affects the crystallinity of the Au grains in the films. The electron diffraction measurement also shows annealing induced morphological evolution in the percolated Au thin films (≥3 nm during solid-state dewetting and recrystallization of the grains.

Controlling thin film structure for the dewetting of catalyst nanoparticle arrays for subsequent carbon nanofiber growth

International Nuclear Information System (INIS)

Randolph, S J; Fowlkes, J D; Melechko, A V; Klein, K L; III, H M Meyer; Simpson, M L; Rack, P D

2007-01-01

Vertically aligned carbon nanofiber (CNF) growth is a catalytic chemical vapor deposition process in which structure and functionality is controlled by the plasma conditions and the properties of the catalyst nanoparticles that template the fiber growth. We have found that the resultant catalyst nanoparticle network that forms by the dewetting of a continuous catalyst thin film is dependent on the initial properties of the thin film. Here we report the ability to tailor the crystallographic texture and composition of the nickel catalyst film and subsequently the nanoparticle template by varying the rf magnetron sputter deposition conditions. After sputtering the Ni catalyst thin films, the films are heated and exposed to an ammonia dc plasma, to chemically reduce the native oxide on the films and induce dewetting of the film to form nanoparticles. Subsequent nanoparticle treatment in an acetylene plasma at high substrate temperature results in CNF growth. Evidence is presented that the texture and composition of the nickel thin film has a significant impact on the structure and composition of the formed nanoparticle, as well as the resultant CNF morphology. Nickel films with a preferred (111) or (100) texture were produced and conditions favoring interfacial silicidation reactions were identified and investigated. Both compositional and structural analysis of the films and nanoparticles indicate that the properties of the as-deposited Ni catalyst film influences the subsequent nanoparticle formation and ultimately the catalytic growth of the carbon nanofibers

Phase transformations in Au(Fe) nano- and microparticles obtained by solid state dewetting of thin Au–Fe bilayer films

International Nuclear Information System (INIS)

Amram, D.; Klinger, L.; Rabkin, E.

2013-01-01

Sub-micrometer-sized particles of Au–Fe alloys were obtained by solid-state dewetting of single-crystalline Au–Fe bilayer films, deposited on c-plane sapphire (α-Al 2 O 3 ) substrates. Depending on the annealing parameters, precipitation of an Fe-rich phase occurred on the side facets of the particles in an interface-limited reaction. Based on the literature values of surface and interface energies in the system, the precipitates were expected to grow inside the Au(Fe) particles, resulting in an (Fe) core–(Au) shell morphology. However, more complex, time-dependent precipitate morphologies were observed, with faceted Fe-rich precipitates attached to the parent faceted Au-rich particles of the same height being dominant at the last stages of the transformation. Our high-resolution transmission electron microscopy observations revealed a nanometric segregation layer of Au on the surface of Fe-rich particles and at their interface with sapphire. This segregation layer modified the surface and interface energies of the Fe-rich particles. A thermodynamic transformation model based on the concept of weighted mean curvature was developed, describing the kinetics of precipitations and morphology evolution of the particles during the dewetting process. Employing the values of surface and interface energies modified by segregation resulted in a good qualitative agreement between theory and experiment

Shape-shifting colloids via stimulated dewetting

Science.gov (United States)

Youssef, Mena; Hueckel, Theodore; Yi, Gi-Ra; Sacanna, Stefano

2016-01-01

The ability to reconfigure elementary building blocks from one structure to another is key to many biological systems. Bringing the intrinsic adaptability of biological systems to traditional synthetic materials is currently one of the biggest scientific challenges in material engineering. Here we introduce a new design concept for the experimental realization of self-assembling systems with built-in shape-shifting elements. We demonstrate that dewetting forces between an oil phase and solid colloidal substrates can be exploited to engineer shape-shifting particles whose geometry can be changed on demand by a chemical or optical signal. We find this approach to be quite general and applicable to a broad spectrum of materials, including polymers, semiconductors and magnetic materials. This synthetic methodology can be further adopted as a new experimental platform for designing and rapidly prototyping functional colloids, such as reconfigurable micro swimmers, colloidal surfactants and switchable building blocks for self-assembly. PMID:27426418

Slip-mediated dewetting of polymer microdroplets

Science.gov (United States)

McGraw, Joshua D.; Chan, Tak Shing; Maurer, Simon; Salez, Thomas; Benzaquen, Michael; Raphaël, Elie; Brinkmann, Martin; Jacobs, Karin

2016-01-01

Classical hydrodynamic models predict that infinite work is required to move a three-phase contact line, defined here as the line where a liquid/vapor interface intersects a solid surface. Assuming a slip boundary condition, in which the liquid slides against the solid, such an unphysical prediction is avoided. In this article, we present the results of experiments in which a contact line moves and where slip is a dominating and controllable factor. Spherical cap-shaped polystyrene microdroplets, with nonequilibrium contact angle, are placed on solid self-assembled monolayer coatings from which they dewet. The relaxation is monitored using in situ atomic force microscopy. We find that slip has a strong influence on the droplet evolutions, both on the transient nonspherical shapes and contact line dynamics. The observations are in agreement with scaling analysis and boundary element numerical integration of the governing Stokes equations, including a Navier slip boundary condition. PMID:26787903

Fabrication of highly oriented D03-Fe3Si nanocrystals by solid-state dewetting of Si ultrathin layer

International Nuclear Information System (INIS)

Naito, Muneyuki; Nakagawa, Tatsuhiko; Machida, Nobuya; Shigematsu, Toshihiko; Nakao, Motoi; Sudoh, Koichi

2013-01-01

In this paper, highly oriented nanocrystals of Fe 3 Si with a D0 3 structure are fabricated on SiO 2 using ultrathin Si on insulator substrate. First, (001) oriented Si nanocrystals are formed on the SiO 2 layer by solid state dewetting of the top Si layer. Then, Fe addition to the Si nanocrystals is performed by reactive deposition epitaxy and post-deposition annealing at 500 °C. The structures of the Fe–Si nanocrystals are analyzed by cross-sectional transmission electron microscopy and nanobeam electron diffraction. We observe that Fe 3 Si nanocrystals with D0 3 , B2, and A2 structures coexist on the 1-h post-annealed samples. Prolonged annealing at 500 °C is effective in obtaining Fe 3 Si nanocrystals with a D0 3 single phase, thereby promoting structural ordering in the nanocrystals. We discuss the formation process of the highly oriented D0 3 -Fe 3 Si nanocrystals on the basis of the atomistic structural information. - Highlights: • Highly oriented Fe–Si nanocrystals (NCs) are fabricated by reactive deposition. • Si NCs formed by solid state dewetting of Si thin layers are used as seed crystals. • The structures of Fe–Si NCs are analyzed by nanobeam electron diffraction. • Most of Fe–Si NCs possess the D0 3 structure after post-deposition annealing

Functional patterned coatings by thin polymer film dewetting.

Science.gov (United States)

Telford, Andrew M; Thickett, Stuart C; Neto, Chiara

2017-12-01

An approach for the fabrication of functional polymer surface coatings is introduced, where micro-scale structure and surface functionality are obtained by means of self-assembly mechanisms. We illustrate two main applications of micro-patterned polymer surfaces obtained through dewetting of bilayers of thin polymer films. By tuning the physical and chemical properties of the polymer bilayers, micro-patterned surface coatings could be produced that have applications both for the selective attachment and patterning of proteins and cells, with potential applications as biomaterials, and for the collection of water from the atmosphere. In all cases, the aim is to achieve functional coatings using approaches that are simple to realize, use low cost materials and are potentially scalable. Copyright © 2017 Elsevier Inc. All rights reserved.

Fabrication of ordered arrays of micro- and nanoscale features with control over their shape and size via templated solid-state dewetting.

Science.gov (United States)

Ye, Jongpil

2015-05-08

Templated solid-state dewetting of single-crystal films has been shown to be used to produce regular patterns of various shapes. However, the materials for which this patterning method is applicable, and the size range of the patterns produced are still limited. Here, it is shown that ordered arrays of micro- and nanoscale features can be produced with control over their shape and size via solid-state dewetting of patches patterned from single-crystal palladium and nickel films of different thicknesses and orientations. The shape and size characteristics of the patterns are found to be widely controllable with varying the shape, width, thickness, and orientation of the initial patches. The morphological evolution of the patches is also dependent on the film material, with different dewetting behaviors observed in palladium and nickel films. The mechanisms underlying the pattern formation are explained in terms of the influence on Rayleigh-like instability of the patch geometry and the surface energy anisotropy of the film material. This mechanistic understanding of pattern formation can be used to design patches for the precise fabrication of micro- and nanoscale structures with the desired shapes and feature sizes.

3D Dewetting for Crystal Patterning: Toward Regular Single-Crystalline Belt Arrays and Their Functionality.

Science.gov (United States)

Wu, Yuchen; Feng, Jiangang; Su, Bin; Jiang, Lei

2016-03-16

Arrays of unidirectional dewetting behaviors can be generated by using 3D-wettability-difference micropillars, yielding highly ordered organic single-crystalline belt arrays. These patterned organic belts show an improved mobility record and can be used as flexible pressure sensors with high sensitivity. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Properties of three-dimensional structures prepared by Ge dewetting from Si(111) at high temperatures

Energy Technology Data Exchange (ETDEWEB)

Shklyaev, Alexander, E-mail: shklyaev@isp.nsc.ru [A. V. Rzhanov Institute of Semiconductor Physics, SB RAS, Novosibirsk 630090 (Russian Federation); Novosibirsk State University, Novosibirsk 630090 (Russian Federation); Bolotov, Leonid; Poborchii, Vladimir; Tada, Tetsuya [National Institute of Advanced Industrial Science and Technology, Higashi 1-1-1, Tsukuba, Ibaraki 305-8562 (Japan)

2015-05-28

The formation of three-dimensional (3D) structures during Ge deposition on Si(111) at about 800 °C is studied with scanning tunneling, Kelvin probe and electron microscopies, and scanning tunneling and Raman spectroscopies. The observed surface morphology is formed by dewetting of Ge from Si(111), since it occurs mainly by means of minimization of surface and interfacial energies. The dewetting proceeds through massive Si eroding around growing 3D structures, providing them to be composed of SiGe with about a 30% Ge content, and leads to the significant reduction of the SiGe/Si interface area. It is found that the SiGe top component of 3D structures forms sharp interfaces with the underlying Si. The minimization of interfacial and strain energies occurs on the way that the 3D structures appear to get the dendrite-like shape. The Ge distribution in the 3D SiGe structures is inhomogeneous in the lateral dimension with a higher Ge concentration in their central areas and Ge segregation on their surface.

Properties of three-dimensional structures prepared by Ge dewetting from Si(111) at high temperatures

International Nuclear Information System (INIS)

Shklyaev, Alexander; Bolotov, Leonid; Poborchii, Vladimir; Tada, Tetsuya

2015-01-01

The formation of three-dimensional (3D) structures during Ge deposition on Si(111) at about 800 °C is studied with scanning tunneling, Kelvin probe and electron microscopies, and scanning tunneling and Raman spectroscopies. The observed surface morphology is formed by dewetting of Ge from Si(111), since it occurs mainly by means of minimization of surface and interfacial energies. The dewetting proceeds through massive Si eroding around growing 3D structures, providing them to be composed of SiGe with about a 30% Ge content, and leads to the significant reduction of the SiGe/Si interface area. It is found that the SiGe top component of 3D structures forms sharp interfaces with the underlying Si. The minimization of interfacial and strain energies occurs on the way that the 3D structures appear to get the dendrite-like shape. The Ge distribution in the 3D SiGe structures is inhomogeneous in the lateral dimension with a higher Ge concentration in their central areas and Ge segregation on their surface

Dewetting and adsorption in homopolymer films containing triblock copolymers: role of chain architecture and anchoring block molar fraction

Czech Academy of Sciences Publication Activity Database

Costa, A. C.; Composto, R. J.; Vlček, Petr; Morera, S.

2005-01-01

Roč. 81, 7-8 (2005), s. 683-698 ISSN 0021-8464 Institutional research plan: CEZ:AV0Z40500505 Keywords : adhesion * dewetting * forward recoil spectrometry Subject RIV: CD - Macromolecular Chemistry Impact factor: 1.128, year: 2005

Deference and Due Process

OpenAIRE

Vermeule, Cornelius Adrian

2015-01-01

In the textbooks, procedural due process is a strictly judicial enterprise; although substantive entitlements are created by legislative and executive action, it is for courts to decide independently what process the Constitution requires. The notion that procedural due process might be committed primarily to the discretion of the agencies themselves is almost entirely absent from the academic literature. The facts on the ground are very different. Thanks to converging strands of caselaw ...

5 CFR 732.301 - Due process.

Science.gov (United States)

2010-01-01

... 5 Administrative Personnel 2 2010-01-01 2010-01-01 false Due process. 732.301 Section 732.301...) NATIONAL SECURITY POSITIONS Due Process and Reporting § 732.301 Due process. When an agency makes an... any determination. (b) Comply with all applicable administrative due process requirements, as provided...

Energy driven self-organization in nanoscale metallic liquid films.

Science.gov (United States)

Krishna, H; Shirato, N; Favazza, C; Kalyanaraman, R

2009-10-01

Nanometre thick metallic liquid films on inert substrates can spontaneously dewet and self-organize into complex nanomorphologies and nanostructures with well-defined length scales. Nanosecond pulses of an ultraviolet laser can capture the dewetting evolution and ensuing nanomorphologies, as well as introduce dramatic changes to dewetting length scales due to the nanoscopic nature of film heating. Here, we show theoretically that the self-organization principle, based on equating the rate of transfer of thermodynamic free energy to rate of loss in liquid flow, accurately describes the spontaneous dewetting. Experimental measurements of laser dewetting of Ag and Co liquid films on SiO(2) substrates confirm this principle. This energy transfer approach could be useful for analyzing the behavior of nanomaterials and chemical processes in which spontaneous changes are important.

Generalized Harmonic Functions and the Dewetting of Thin Films

International Nuclear Information System (INIS)

Auchmuty, Giles; Kloucek, Petr

2007-01-01

This paper describes the solvability of Dirichlet problems for Laplace's equation when the boundary data is not smooth enough for the existence of a weak solution in H 1 Ω. Scales of spaces of harmonic functions and of boundary traces are defined and the solutions are characterized as limits of classical harmonic functions in special norms. The generalized harmonic functions, and their norms, are defined using series expansions involving harmonic Steklov eigenfunctions on the domain. It is shown that the usual trace operator has a continuous extension to an isometric isomorphism of specific spaces. This provides a characterization of the generalized solutions of harmonic Dirichlet problems. Numerical simulations of a model problem are described. This problem is related to the dewetting of thin films and the associated phenomenology is described

Preventing dewetting during rapid-thermal annealing of FePt films with enhanced L10 ordering by introducing Ag cap-layers

International Nuclear Information System (INIS)

Hsiao, S.N.; Wu, S.C.; Liu, S.H.; Tsai, J.L.; Chen, S.K.; Chang, Y.C.; Lee, H.Y.

2015-01-01

High-order FePt continuous films with a strong (001) texture were fabricated on a glass substrate by introducing Ag layers and rapid thermal annealing (RTA). The dewetting of the (001)-textured FePt was suppressed during RTA with high heating rates (>80 K/s). The Ag cap layers not only increased the in-plane tensile stress, but also improved the (001) anisotropy and L1 0 ordering of the FePt layers. All continuous Ag/FePt bilayer films possessed strong perpendicular anisotropies and high-ordered states irrespective of the Ag layer thickness. - Highlights: • Dewetting of (001) FePt fims were suppressed by introducing Ag cap layers. • Ag layers enhanced in-plane tensile stress, (001) texture and L1 0 ordering. • Irrespective of Ag thickness, the Ag/FePt films exhibited strong (001) texture

Importance of dewetting in organic molecular-beam deposition: Pentacene on gold

International Nuclear Information System (INIS)

Beernink, G.; Strunskus, T.; Witte, G.; Woell, Ch.

2004-01-01

Organic molecular-beam deposition of pentacene on gold substrates has been investigated using a multitechnique approach. The morphology of the organic thin films depends strongly on the substrate temperature. Pronounced dewetting and island formation are observed at room temperature. Whereas pentacene molecules adopt a planar monolayer structure, they continue to grow in an upright orientation in multilayer films as inferred from x-ray absorption spectroscopy and atomic force microscopy. These results are in pronounced contrast to a recent scanning tunneling microscopy (STM) study by Kang and Zhu [Appl. Phys. Lett. 82, 3248 (2003)] and indicate fundamental problems in the interpretation of STM measurements for organic thin films

Dewetting transition assisted clearance of (NFGAILS) amyloid fibrils from cell membranes by graphene

Energy Technology Data Exchange (ETDEWEB)

Liu, Jiajia; Yang, Zaixing; Gu, Zonglin [Institute of Quantitative Biology and Medicine, SRMP and RAD-X, Collaborative Innovation Center of Radiation Medicine of Jiangsu Higher Education Institutions, and Jiangsu Provincial Key Laboratory of Radiation Medicine and Protection, Soochow University, Suzhou 215123 (China); Li, Haotian [Bio-X Lab, Department of Physics, Zhejiang University, Hangzhou 310027 (China); Garate, Jose Antonio [IBM Thomas J. Watson Research Center, Yorktown Heights, New York 10598 (United States); Zhou, Ruhong, E-mail: ruhongz@us.ibm.com [Institute of Quantitative Biology and Medicine, SRMP and RAD-X, Collaborative Innovation Center of Radiation Medicine of Jiangsu Higher Education Institutions, and Jiangsu Provincial Key Laboratory of Radiation Medicine and Protection, Soochow University, Suzhou 215123 (China); IBM Thomas J. Watson Research Center, Yorktown Heights, New York 10598 (United States); Department of Chemistry, Columbia University, New York, New York 10027 (United States)

2014-12-14

Clearance of partially ordered oligomers and monomers deposited on cell membrane surfaces is believed to be an effective route to alleviate many potential protein conformational diseases (PCDs). With large-scale all-atom molecular dynamics simulations, here we show that graphene nanosheets can easily and quickly win a competitive adsorption of human islet amyloid polypeptides (hIAPP{sub 22-28}) NFGAILS and associated fibrils against cell membrane, due to graphene's unique two-dimensional, highly hydrophobic surface with its all-sp{sup 2} hybrid structure. A nanoscale dewetting transition was observed at the interfacial region between the fibril (originally deposited on the membrane) and the graphene nanosheet, which significantly assisted the adsorption of fibrils onto graphene from the membrane. The π–π stacking interaction between Phe23 and graphene played a crucial role, providing the driving force for the adsorption at the graphene surface. This study renders new insight towards the importance of water during the interactions between amyloid peptides, the phospholipidic membrane, and graphene, which might shed some light on future developments of graphene-based nanomedicine for preventing/curing PCDs like type II diabetes mellitus.

Dewetting transition assisted clearance of (NFGAILS) amyloid fibrils from cell membranes by graphene

International Nuclear Information System (INIS)

Liu, Jiajia; Yang, Zaixing; Gu, Zonglin; Li, Haotian; Garate, Jose Antonio; Zhou, Ruhong

2014-01-01

Clearance of partially ordered oligomers and monomers deposited on cell membrane surfaces is believed to be an effective route to alleviate many potential protein conformational diseases (PCDs). With large-scale all-atom molecular dynamics simulations, here we show that graphene nanosheets can easily and quickly win a competitive adsorption of human islet amyloid polypeptides (hIAPP 22-28 ) NFGAILS and associated fibrils against cell membrane, due to graphene's unique two-dimensional, highly hydrophobic surface with its all-sp 2 hybrid structure. A nanoscale dewetting transition was observed at the interfacial region between the fibril (originally deposited on the membrane) and the graphene nanosheet, which significantly assisted the adsorption of fibrils onto graphene from the membrane. The π–π stacking interaction between Phe23 and graphene played a crucial role, providing the driving force for the adsorption at the graphene surface. This study renders new insight towards the importance of water during the interactions between amyloid peptides, the phospholipidic membrane, and graphene, which might shed some light on future developments of graphene-based nanomedicine for preventing/curing PCDs like type II diabetes mellitus

Formation of controllable polymer micropatterns through liquid film electro-dewetting

Science.gov (United States)

Zhou, Shangru; Zheng, Huai; Li, Guoliang; Liu, Jie; Liu, Sheng

2018-04-01

Controllable polymer micropatterns, served as indispensable function structures, are extensively required in many micro/nano scientific areas and engineering applications. Exploring advanced methods of fabricating micropatterns is always a research hotspot. In this article, we introduce a novel method of patterning polymer by the electro-dewetting induced by corona discharge. For the first time, it is observed experimentally that liquid polymer on conductive/non-conductive patterned substrates, spontaneously converges from non-conductive areas to conductive areas under the action of ion wind. Taking advantage of such a flow phenomenon, controllable polymer micropatterns including microbump arrays and microwell arrays are fabricated successfully. Their sizes range from hundreds of microns to millimeters. Micropattern surfaces present an ultra-smooth characteristic, with roughness in the nanometer range.

Fabrication of highly oriented D0{sub 3}-Fe{sub 3}Si nanocrystals by solid-state dewetting of Si ultrathin layer

Energy Technology Data Exchange (ETDEWEB)

Naito, Muneyuki, E-mail: naito22@center.konan-u.ac.jp [Department of Chemistry, Konan University, Okamoto, Higashinada, Kobe, Hyogo 658-8501 (Japan); Nakagawa, Tatsuhiko; Machida, Nobuya; Shigematsu, Toshihiko [Department of Chemistry, Konan University, Okamoto, Higashinada, Kobe, Hyogo 658-8501 (Japan); Nakao, Motoi [Graduate School of Engineering, Kyushu Institute of Technology, Sensui, Tobata, Kitakyushu, Fukuoka 804-8550 (Japan); Sudoh, Koichi [The Institute of Scientific and Industrial Research, Osaka University, Mihogaoka, Ibaraki, Osaka 567-0047 (Japan)

2013-07-31

In this paper, highly oriented nanocrystals of Fe{sub 3}Si with a D0{sub 3} structure are fabricated on SiO{sub 2} using ultrathin Si on insulator substrate. First, (001) oriented Si nanocrystals are formed on the SiO{sub 2} layer by solid state dewetting of the top Si layer. Then, Fe addition to the Si nanocrystals is performed by reactive deposition epitaxy and post-deposition annealing at 500 °C. The structures of the Fe–Si nanocrystals are analyzed by cross-sectional transmission electron microscopy and nanobeam electron diffraction. We observe that Fe{sub 3}Si nanocrystals with D0{sub 3}, B2, and A2 structures coexist on the 1-h post-annealed samples. Prolonged annealing at 500 °C is effective in obtaining Fe{sub 3}Si nanocrystals with a D0{sub 3} single phase, thereby promoting structural ordering in the nanocrystals. We discuss the formation process of the highly oriented D0{sub 3}-Fe{sub 3}Si nanocrystals on the basis of the atomistic structural information. - Highlights: • Highly oriented Fe–Si nanocrystals (NCs) are fabricated by reactive deposition. • Si NCs formed by solid state dewetting of Si thin layers are used as seed crystals. • The structures of Fe–Si NCs are analyzed by nanobeam electron diffraction. • Most of Fe–Si NCs possess the D0{sub 3} structure after post-deposition annealing.

Solid-state dewetting of Au-Ni bi-layer films mediated through individual layer thickness and stacking sequence

Science.gov (United States)

Herz, Andreas; Theska, Felix; Rossberg, Diana; Kups, Thomas; Wang, Dong; Schaaf, Peter

2018-06-01

In the present work, the solid-state dewetting of Au-Ni bi-layer thin films deposited on SiO2/Si is systematically studied with respect to individual layer thickness and stacking sequence. For this purpose, a rapid heat treatment at medium temperatures is applied in order to examine void formation at the early stages of the dewetting. Compositional variations are realized by changing the thickness ratio of the bi-layer films, while the total thickness is maintained at 20 nm throughout the study. In the event of Au/Ni films annealed at 500 °C, crystal voids exposing the substrate are missing regardless of chemical composition. In reverse order, the number of voids per unit area in two-phase Au-Ni thin films is found to be governed by the amount of Au-rich material. At higher temperatures up to 650 °C, a decreased probability of nucleation comes at the expense of a major portion of cavities, resulting in the formation of bubbles in 15 nm Ni/5 nm Au bi-layers. Film buckling predominantly occurred at phase boundaries crossing the bubbles.

Mimicking the stenocara beetle--dewetting of drops from a patterned superhydrophobic surface.

Science.gov (United States)

Dorrer, Christian; Rühe, Jürgen

2008-06-17

This paper describes the preparation of superhydrophobic surfaces that have been selectively patterned with circular hydrophilic domains. These materials mimicked the back of the stenocara beetle and collected drops of water if exposed to mist or fog. Under the effect of gravity, the drops dewetted from the hydrophilic regions once a critical volume had been reached. The surface energy in the hydrophilic regions was carefully controlled and assumed various values, allowing us to study the behavior of drops as a function of the superhydrophobic/hydrophilic contrast. We have investigated the development of drops and quantitatively analyzed the critical volumes as a function of several parameters.

Preventing dewetting during rapid-thermal annealing of FePt films with enhanced L1{sub 0} ordering by introducing Ag cap-layers

Energy Technology Data Exchange (ETDEWEB)

Hsiao, S.N., E-mail: pmami.hsiao@gmail.com [Department of Materials Science and Engineering, Feng Chia University, Taichung 40724, Taiwan (China); Department of Power Mechanical Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Wu, S.C. [Department of Materials Science and Engineering, National Chung Hsing University, Taichung 40227, Taiwan (China); Liu, S.H. [Department of Materials Science and Engineering, Feng Chia University, Taichung 40724, Taiwan (China); Tsai, J.L., E-mail: tsaijl@dragon.nchu.edu.tw [Department of Materials Science and Engineering, National Chung Hsing University, Taichung 40227, Taiwan (China); Chen, S.K. [Department of Materials Science and Engineering, Feng Chia University, Taichung 40724, Taiwan (China); Chang, Y.C. [Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Lee, H.Y. [Scientific Research Division, National Synchrotron Radiation Research Center, Hsinchu 30077, Taiwan (China)

2015-11-15

High-order FePt continuous films with a strong (001) texture were fabricated on a glass substrate by introducing Ag layers and rapid thermal annealing (RTA). The dewetting of the (001)-textured FePt was suppressed during RTA with high heating rates (>80 K/s). The Ag cap layers not only increased the in-plane tensile stress, but also improved the (001) anisotropy and L1{sub 0} ordering of the FePt layers. All continuous Ag/FePt bilayer films possessed strong perpendicular anisotropies and high-ordered states irrespective of the Ag layer thickness. - Highlights: • Dewetting of (001) FePt fims were suppressed by introducing Ag cap layers. • Ag layers enhanced in-plane tensile stress, (001) texture and L1{sub 0} ordering. • Irrespective of Ag thickness, the Ag/FePt films exhibited strong (001) texture.

Effect of annealing ambient on anisotropic retraction of film edges during solid-state dewetting of thin single crystal films

Energy Technology Data Exchange (ETDEWEB)

Kim, Gye Hyun; Thompson, Carl V., E-mail: cthomp@mit.edu [Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 01239 (United States); Ma, Wen [Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 01239 (United States); Yildiz, Bilge [Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 01239 (United States); Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 01239 (United States)

2016-08-21

During solid-state dewetting of thin single crystal films, film edges retract at a rate that is strongly dependent on their crystallographic orientations. Edges with kinetically stable in-plane orientations remain straight as they retract, while those with other in-plane orientations develop in-plane facets as they retract. Kinetically stable edges have retraction rates that are lower than edges with other orientations and thus determine the shape of the natural holes that form during solid-state dewetting. In this paper, measurements of the retraction rates of kinetically stable edges for single crystal (110) and (100) Ni films on MgO are presented. Relative retraction rates of kinetically stable edges with different crystallographic orientations are observed to change under different annealing conditions, and this accordingly changes the initial shapes of growing holes. The surfaces of (110) and (100) films were also characterized using low energy electron diffraction, and different surface reconstructions were observed under different ambient conditions. The observed surface structures were found to correlate with the observed changes in the relative retraction rates of the kinetically stable edges.

Constitutional Due Process and Educational Administration.

Science.gov (United States)

Uerling, Donald F.

1985-01-01

Discusses substantive and procedural due process as required by the United States Constitution and interpreted by the Supreme Court, with particular reference to situations arising in educational environments. Covers interests protected by due process requirements, the procedures required, and some special considerations that may apply. (PGD)

Cross-sectional characterization of the dewetting of a Au/Ni bilayer film.

Science.gov (United States)

Cen, Xi; Thron, Andrew M; Zhang, Xinming; van Benthem, Klaus

2017-07-01

The solid state dewetting of Au/Ni bilayer films was investigated by cross-sectional transmission electron microscopy techniques, including energy-dispersive X-ray spectroscopy, electron energy-loss spectroscopy and precession electron diffraction. After annealing under high vacuum conditions the early stage of film agglomeration revealed significant changes in film morphology and chemical distribution. Both Au and Ni showed texturing. Despite the initial deposition sequence of the as-deposited Au/Ni/SiO 2 /Si interface structure, the majority of the metal/SiO 2 interface was Au/SiO 2 after annealing at 675°C for 1h. Void nucleation was predominantly observed at Au/Ni/SiO 2 triple junctions, rather than grain boundary grooving at free surface of the metal film. Detailed cross-sectional characterization reveals that the Au/Ni interface in addition to small amounts of metal alloying strongly affects film break-up and agglomeration kinetics. The formation of Au/SiO 2 interface sections is found to be energetically preferred over Ni/SiO 2 due to compressive stress in the as-deposited Ni layer. Void nucleation is observed at the film/substrate interface, while the formation of voids at Ni/Au phase boundaries inside the metal film is caused by the Kirkendall effect. Copyright © 2016 Elsevier B.V. All rights reserved.

Static or breakloose friction for lubricated contacts: the role of surface roughness and dewetting

International Nuclear Information System (INIS)

Lorenz, B; Persson, B N J; Krick, B A; Sawyer, W G; Rodriguez, N; Mangiagalli, P

2013-01-01

We present experimental data for the static or breakloose friction for lubricated elastomer contacts, as a function of the time of stationary contact. Due to fluid squeeze-out from the asperity contact regions, the breakloose friction force increases continuously with the time of stationary contact. We consider three different cases: (a) PDMS rubber balls against flat smooth glass surfaces, (b) PDMS cylinder ribs against different substrates (glass, smooth and rough PMMA and an inert polymer) and (c) application to syringes. Due to differences in the surface roughness and contact pressures the three systems exhibit very different time dependences of the breakloose friction. In case (a) for rough surfaces the dry contact area A is a small fraction of the nominal contact area A 0 , and the fluid squeeze-out is fast. In case (b) the dry contact area is close to the nominal contact area, A/A 0 ≈ 1, and fluid squeeze-out is very slow due to percolation of the contact area. In this case, remarkably, different fluids with very different viscosities, ranging from 0.005 Pa s (water–glycerol mixture) to 1.48 Pa s (glycerol), give very similar breakloose friction forces as a function of the time of stationary contact. In case (c) the contact pressure and the surface roughness are larger than in case (b), and the squeeze-out is very slow so that even after a very long time the area of real contact is below the percolation threshold. For all cases (a)–(c), the increase in the breakloose friction is mainly due to the increase in the area of real contact with increasing time, because of the fluid squeeze-out and dewetting. (paper)

Static or breakloose friction for lubricated contacts: the role of surface roughness and dewetting.

Science.gov (United States)

Lorenz, B; Krick, B A; Rodriguez, N; Sawyer, W G; Mangiagalli, P; Persson, B N J

2013-11-06

We present experimental data for the static or breakloose friction for lubricated elastomer contacts, as a function of the time of stationary contact. Due to fluid squeeze-out from the asperity contact regions, the breakloose friction force increases continuously with the time of stationary contact. We consider three different cases: (a) PDMS rubber balls against flat smooth glass surfaces, (b) PDMS cylinder ribs against different substrates (glass, smooth and rough PMMA and an inert polymer) and (c) application to syringes. Due to differences in the surface roughness and contact pressures the three systems exhibit very different time dependences of the breakloose friction. In case (a) for rough surfaces the dry contact area A is a small fraction of the nominal contact area A0, and the fluid squeeze-out is fast. In case (b) the dry contact area is close to the nominal contact area, A/A0 ≈ 1, and fluid squeeze-out is very slow due to percolation of the contact area. In this case, remarkably, different fluids with very different viscosities, ranging from 0.005 Pa s (water–glycerol mixture) to 1.48 Pa s (glycerol), give very similar breakloose friction forces as a function of the time of stationary contact. In case (c) the contact pressure and the surface roughness are larger than in case (b), and the squeeze-out is very slow so that even after a very long time the area of real contact is below the percolation threshold. For all cases (a)–(c), the increase in the breakloose friction is mainly due to the increase in the area of real contact with increasing time, because of the fluid squeeze-out and dewetting.

A hierarchical structure through imprinting of a polyimide precursor without residual layers

International Nuclear Information System (INIS)

Pai, I-Ting; Hon, Min-Hsiung; Leu, Ing-Chi

2008-01-01

A patterned polyimide without a residual layer is obtained by imprinting with the assistance of a residual solvent. The effects of the wetting behaviors of the poly-amic acid (PAA) solution coated on various surfaces are examined and the formation of hierarchical patterns without residual layers is demonstrated. polydimethylsiloxane (PDMS) and PEI/PDMS are used as imprinting molds with Si and 300 nm SiO 2 /Si as substrates. The results indicate that the various ambits of patterns without a residual layer are formed due to the dewetting phenomena caused by surface tension (Suh 2006 Small 2 832). During imprinting, PDMS with a low surface energy makes the PAA solution flow away from its surface exposing the contact area due to dewetting. Self-organized hierarchical structures are also obtained from this process due to effective dewetting. The present study provides a new approach for fabricating patterns without residual layers and the consequent preparation of hierarchical structures, which is considered to be impossible using the lithographic technique

Interaction of 3D dewetting nanodroplets on homogeneous and chemically heterogeneous substrates

International Nuclear Information System (INIS)

Asgari, M; Moosavi, A

2014-01-01

Long-time interaction of dewetting nanodroplets is investigated using a long-wave approximation method. Although three-dimensional (3D) droplets evolution dynamics exhibits qualitative behavior analogous to two-dimensional (2D) dynamics, there is an extensive quantitative difference between them. 3D dynamics is substantially faster than 2D dynamics. This can be related to the larger curvature and, as a consequence, the larger Laplace pressure difference between the droplets in 3D systems. The influence of various chemical heterogeneities on the behavior of droplets has also been studied. In the case of gradient surfaces, it is shown how the gradient direction could change the dynamics. For a chemical step located between the droplets, the dynamics is enhanced or weakened depending on the initial configuration of the system. (paper)

Procedural Due Process Rights in Student Discipline.

Science.gov (United States)

Pressman, Robert; Weinstein, Susan

To assist administrators in understanding procedural due process rights in student discipline, this manual draws together hundreds of citations and case summaries of federal and state court decisions and provides detailed commentary as well. Chapter 1 outlines the general principles of procedural due process rights in student discipline, such as…

Dewetting based fabrication of fibrous micro-scaffolds as potential injectable cell carriers.

Science.gov (United States)

Song, Hokyung; Yin, Liya; Chilian, William M; Zhang Newby, Bi-Min

2015-03-01

Although regenerative medicine utilizing tissue scaffolds has made enormous strides in recent years, many constraints still hamper their effectiveness. A limitation of many scaffolds is that they form surface patches, which are not particularly effective for some types of "wounds" that are deep within tissues, e.g., stroke and myocardial infarction. In this study, we reported the generation of fibrous micro-scaffolds feasible for delivering cells by injection into the tissue parenchyma. The micro-scaffolds (widthsdewetting of poly(lactic-co-glycolic acid) thin films containing parallel strips, and cells were seeded to form cell/polymer micro-constructs during or post the micro-scaffold fabrication process. Five types of cells including rat induced vascular progenitor cells were assessed for the formation of the micro-constructs. Critical factors in forming fibrous micro-scaffolds via dewetting of polymer thin films were found to be properties of polymers and supporting substrates, temperature, and proteins in the culture medium. Also, the ability of cells to attach to the micro-scaffolds was essential in forming cell/polymer micro-constructs. Both in vitro and in vivo assessments of injecting these micro-scaffolding constructs showed, as compared to free cells, enhanced cell retention at the injected site, which could lead to improved tissue engineering and regeneration. Copyright © 2014 Elsevier B.V. All rights reserved.

Spontaneous recovery of superhydrophobicity on nanotextured surfaces

Science.gov (United States)

Prakash, Suruchi; Xi, Erte; Patel, Amish J.

2016-01-01

Rough or textured hydrophobic surfaces are dubbed “superhydrophobic” due to their numerous desirable properties, such as water repellency and interfacial slip. Superhydrophobicity stems from an aversion of water for the hydrophobic surface texture, so that a water droplet in the superhydrophobic “Cassie state” contacts only the tips of the rough surface. However, superhydrophobicity is remarkably fragile and can break down due to the wetting of the surface texture to yield the “Wenzel state” under various conditions, such as elevated pressures or droplet impact. Moreover, due to large energetic barriers that impede the reverse transition (dewetting), this breakdown in superhydrophobicity is widely believed to be irreversible. Using molecular simulations in conjunction with enhanced sampling techniques, here we show that on surfaces with nanoscale texture, water density fluctuations can lead to a reduction in the free energetic barriers to dewetting by circumventing the classical dewetting pathways. In particular, the fluctuation-mediated dewetting pathway involves a number of transitions between distinct dewetted morphologies, with each transition lowering the resistance to dewetting. Importantly, an understanding of the mechanistic pathways to dewetting and their dependence on pressure allows us to augment the surface texture design, so that the barriers to dewetting are eliminated altogether and the Wenzel state becomes unstable at ambient conditions. Such robust surfaces, which defy classical expectations and can spontaneously recover their superhydrophobicity, could have widespread importance, from underwater operation to phase-change heat transfer applications. PMID:27140619

Wetting and dewetting of extracellular matrix and glycocalix models

International Nuclear Information System (INIS)

Tanaka, Motomu; Rehfeldt, Florian; Schneider, Matthias F; Mathe, Gerald; Albersdoerfer, Antero; Neumaier, Klaus R; Purrucker, Oliver; Sackmann, Erich

2005-01-01

In this paper, we study wetting and dewetting of hydrated biopolymer layers mediating cell-cell and cell-tissue contacts, called the extracellular matrix and cell surface glycocalix, by the combination of various physical techniques. Here, the sum of the net effects of the various interfacial forces, which is referred to as the disjoining pressure, is used as a semi-quantitative measure to describe the thermodynamics of hydrated interlayers. The disjoining pressure can be measured by applying external forces to maintain the equilibrium distance between two parallel surfaces (in biology, two neighbouring plasma membranes). Using artificial models of the extracellular matrix and glycocalix, we describe stable cell-cell contacts in terms of the wetting (or spreading) of complex fluids on polymer surfaces. In fact, the adjustment of the wetting interaction via thin hydrating layers enables us to transform three-dimensional cell membranes into quasi-two-dimensional films on macroscopically large surfaces. Fine-tuning of local wetting conditions at the interface further allows for the selective wetting of native cell membranes on microstructured polysaccharide films, which has a large potential for individual detection of biological functions in confined geometries

Twin-assisted growth of nominally stable substrates underneath dewetted Au nanoparticles

International Nuclear Information System (INIS)

Liu, Fang; Xie, Dong Yue; Majdi, Tahereh; Zhu, Guo-zhen

2016-01-01

By applying a simple and inexpensive thermal treatment, we synthesized supported gold-oxide nanostructures, which have potential applications to plasmonic devices and biosensors. The regrowth of nominally stable substrates under gold nanoparticles is associated with the appearance of preferential orientations of dewetted nanoparticles and the formation of atomically sharp interfacial monolayers. Steps present at the interfacial monolayer usually occur at defects including the intersection points of twin planes at the interface. They were related to the nucleation and immigration of the interfacial monolayers, prompting the substrate regrowth. Accordingly, we proposed the twin-assisted growth mechanism, which provides insight on the synthesis of gold-oxide nanostructures. - Highlights: • The twin-assisted growth mechanism is proposed for the abnormal regrowth of substrate underneath Au nanoparticles. • The substrate regrowth is related to the steps and ledges that are present at the Au–MgAl_2O_4 interfacial monolayers. • Interfacial steps are detected at defects such as the intersecting points of twin planes at the interface.

Twin-assisted growth of nominally stable substrates underneath dewetted Au nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Liu, Fang; Xie, Dong Yue [State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, 800 Dongchuan Rd., Shanghai 200240 (China); Majdi, Tahereh [Department of Engineering Physics, McMaster University, 1280 Main St. W., Hamilton, ON L8S 4L7 (Canada); Zhu, Guo-zhen, E-mail: zhugz@sjtu.edu.cn [State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, 800 Dongchuan Rd., Shanghai 200240 (China)

2016-03-15

By applying a simple and inexpensive thermal treatment, we synthesized supported gold-oxide nanostructures, which have potential applications to plasmonic devices and biosensors. The regrowth of nominally stable substrates under gold nanoparticles is associated with the appearance of preferential orientations of dewetted nanoparticles and the formation of atomically sharp interfacial monolayers. Steps present at the interfacial monolayer usually occur at defects including the intersection points of twin planes at the interface. They were related to the nucleation and immigration of the interfacial monolayers, prompting the substrate regrowth. Accordingly, we proposed the twin-assisted growth mechanism, which provides insight on the synthesis of gold-oxide nanostructures. - Highlights: • The twin-assisted growth mechanism is proposed for the abnormal regrowth of substrate underneath Au nanoparticles. • The substrate regrowth is related to the steps and ledges that are present at the Au–MgAl{sub 2}O{sub 4} interfacial monolayers. • Interfacial steps are detected at defects such as the intersecting points of twin planes at the interface.

1-D Metal Nanobead Arrays within Encapsulated Nanowires via a Red-Ox-Induced Dewetting: Mechanism Study by Atom-Probe Tomography.

Science.gov (United States)

Sun, Zhiyuan; Tzaguy, Avra; Hazut, Ori; Lauhon, Lincoln J; Yerushalmi, Roie; Seidman, David N

2017-12-13

Metal nanoparticle arrays are excellent candidates for a variety of applications due to the versatility of their morphology and structure at the nanoscale. Bottom-up self-assembly of metal nanoparticles provides an important complementary alternative to the traditional top-down lithography method and makes it possible to assemble structures with higher-order complexity, for example, nanospheres, nanocubes, and core-shell nanostructures. Here we present a mechanism study of the self-assembly process of 1-D noble metal nanoparticles arrays, composed of Au, Ag, and AuAg alloy nanoparticles. These are prepared within an encapsulated germanium nanowire, obtained by the oxidation of a metal-germanium nanowire hybrid structure. The resulting structure is a 1-D array of equidistant metal nanoparticles with the same diameter, the so-called nanobead (NB) array structure. Atom-probe tomography and transmission electron microscopy were utilized to investigate the details of the morphological and chemical evolution during the oxidation of the encapsulated metal-germanium nanowire hybrid-structures. The self-assembly of nanoparticles relies on the formation of a metal-germanium liquid alloy and the migration of the liquid alloy into the nanowire, followed by dewetting of the liquid during shape-confined oxidation where the liquid column breaks-up into nanoparticles due to the Plateau-Rayleigh instability. Our results demonstrate that the encapsulating oxide layer serves as a structural scaffold, retaining the overall shape during the eutectic liquid formation and demonstrates the relationship between the oxide mechanical properties and the final structural characteristics of the 1-D arrays. The mechanistic details revealed here provide a versatile tool-box for the bottom-up fabrication of 1-D arrays nanopatterning that can be modified for multiple applications according to the RedOx properties of the material system components.

Teacher Dismissal and Due Process.

Science.gov (United States)

Leichner, Edward C.; Blackstone, Sidney

1977-01-01

This article addresses due process requirements in the nonrenewal and dismissal of tenured and nontenured teachers. The Georgia Fair Dismissal Law is used as a basis for discussing the grounds for teacher dismissal. Dismissal grounds discussed are 1) incompetency; 2) insubordination; 3) willful neglect of duties; 4) immorality; 5) inciting,…

Due Process Hearing Case Study

Science.gov (United States)

Bateman, David F.

2009-01-01

William is 9 years of age, residing with his parent within the boundaries of an unnamed district ("the District"). As a student with autism he is eligible for special education programming and services. There was one issue presented for this due process hearing: What was the appropriate program and placement for him for the 2008-2009 school year?…

Influences of poly[(styrene){sub x}-stat-(chloromethylstyrene){sub y}]s additives on dewetting behaviors of polystyrene thin films: effects of polar group ratio and film thickness

Energy Technology Data Exchange (ETDEWEB)

Sangjan, Suntree [Research Unit of Advanced Ceramics, Department of Materials Science, Faculty of Science, Chulalongkorn University, Bangkok 10330 (Thailand); Traiphol, Nisanart, E-mail: Nisanart.T@chula.ac.th [Research Unit of Advanced Ceramics, Department of Materials Science, Faculty of Science, Chulalongkorn University, Bangkok 10330 (Thailand); Center for Petroleum, Petrochemical, and Advanced Materials, Chulalongkorn University, Bangkok 10330 (Thailand); Traiphol, Rakchart, E-mail: Rakchartt@nu.ac.th [Laboratory of Advanced Polymers and Nanomaterials, Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Naresuan University, Phitsanulok 65000 (Thailand); NANOTEC Center of Excellence at Mahidol University, Rama 6 Road, Ratchathewi, Bangkok 10400 (Thailand)

2012-05-31

This contribution investigates the addition of poly(styrene-stat-chloromethylstyrene (ClMS))s as dewetting inhibitors of polystyrene (PS) thin films with thicknesses ranging from 12 to 38 nm. The ClMS ratios in the copolymers are 5, 25 and 45 mol%. Atomic force microscopy and optical microscopy are utilized to follow morphological changes of blended PS/copolymer films upon annealing above their glass transition temperatures. We have found that thermal stability of the PS films is greatly improved when a small amount of the copolymers is added into the system. The polar ClMS groups provide anchoring sites with the polar SiO{sub x}/Si substrate while the styrene segments favorably interact with the PS matrix. The effectiveness of the copolymers as dewetting inhibitors is also found to increase with mole ratio of ClMS group. While the stability of PS films is systematically improved upon addition of the highly substituted copolymers, using the copolymer with relatively low ratio of ClMS group could lead to the opposite result. This class of copolymers can be utilized for improving thermal stability of ultrathin PS films. The fundamental knowledge from this study is also important for designing or selecting structure of additives used to improve the stability of polymeric thin films. - Highlights: Black-Right-Pointing-Pointer Efficient method for improving stability of polystyrene (PS) thin films. Black-Right-Pointing-Pointer Poly(styrene-stat-chloromethylstyrene)s are used as dewetting inhibitors. Black-Right-Pointing-Pointer Thermal stability of blended PS/copolymers greatly improved. Black-Right-Pointing-Pointer Effectiveness of the copolymers increases with mole ratio of chloromethylstyrene group. Black-Right-Pointing-Pointer Important results for designing materials in coating application.

Scope and limitations of due process in administrative proceedings

Directory of Open Access Journals (Sweden)

Bernardo Carvajal Sánchez

2010-12-01

Full Text Available In order to explain in a better way the scope of Due Process in Administrative Law as a legal norm whose respect is essential to all government agencies, three points of view (formal, structural and material are proposed. Those items seem useful to understand “Administrative Due Process” in all its dimensions: as a constitutional norm developed by the enactment of laws and decrees; as a principle inspiring some conducts and new norms; and as an objective and subjective fundamental right. On the other hand, it is shown that Administrative Due Process is not an absolute rule because in some cases its full application is subject to normative relativism. Two opposite trends can be perceived at this point: in the first place, government agencies usually do not act the same way judges do, so Administrative Due Process should be distinguished from Judicial Due Process; therefore, it could actually have a more restricted scope. In the second place, some administrative authorities are nowadays playing a role more or less similar to what judges do. This means that new procedural guarantees will be claimed. In any case, admitting valid limitations to Administrative Due Process leads to the quest of the limits of these limitations. The application of the rule of Due Process cannot be totally suppressed; its scope cannot be completely reduced. This is the result of its fundamental nature as a legal norm that ensures justice and equity in all administrative procedures, and proscribes random decisions.

Self-destruction and dewetting of thin polymer films the role of interfacial tensions

CERN Document Server

Reiter, G; Sharma, A

2003-01-01

We present real-time optical microscopy observations of the pattern evolution in self-destruction and subsequent dewetting of thin polymer films based on experiments with polydimethylsiloxane films sandwiched between silicon wafers and aqueous surfactant solutions. A clear scenario consisting of four distinct stages has been identified: amplification of surface fluctuations, break-up of the film and formation of holes, growth and coalescence of holes, and droplet formation and ripening. Besides a linear dependence on film viscosity and surface tension, the time tau for film rupture varied significantly with film thickness h (tau approx h sup 5), as expected from theory. While the role of long-range forces is dominant only in the first stage, the later stages are controlled by the combination of interfacial tensions resulting in the contact angle characterizing the three-phase contact line. During the first stage, the characteristic distance of the pattern remains constant, represented by a time-independent wa...

Procedural Due Process and Fairness in Student Discipline. A Legal Memorandum.

Science.gov (United States)

Johnson, T. Page

When the Supreme Court decided that the Constitution requires public school principals to follow procedural due process in suspension and expulsion cases, the Justices recognized a link between procedural due process and the fairness of effective discipline. This report reviews the constitutional due process required when public school officials…

AFT Chief Promises Due-Process Reform

Science.gov (United States)

Sawchuk, Stephen

2010-01-01

The president of the American Federation of Teachers (AFT), Randi Weingarten, is putting the sensitive issue of due process on the education reform table, with a pledge to work with districts to streamline the often-cumbersome procedures for dismissing teachers who fail to improve their performance after receiving help and support. She has also…

Photonic metasurface made of array of lens-like SiGe Mie resonators formed on (100) Si substrate via dewetting

Science.gov (United States)

Poborchii, Vladimir; Shklyaev, Alexander; Bolotov, Leonid; Uchida, Noriyuki; Tada, Tetsuya; Utegulov, Zhandos N.

2017-12-01

Metasurfaces consisting of arrays of high-index Mie resonators concentrating/redirecting light are important for integrated optics, photodetectors, and solar cells. Herein, we report the optical properties of low-Ge-content SiGe lens-like Mie resonator island arrays fabricated via dewetting during Ge deposition on a Si(100) surface at approximately 900 °C. We observe enhancement of the Si interaction with light owing to the efficient island-induced light concentration in the submicron-depth Si layer, which is mediated by both near-field Mie resonance leaking into the substrate and far-field light focusing. Such metasurfaces can improve the Si photodetector and solar-cell performance.

On The Role of Wetting, Structure Width, and Flow Characteristics in Polymer Replication on Micro- and Nanoscale

DEFF Research Database (Denmark)

Rytka, Christian; Opara, Nadia; Andersen, Nis Korsgaard

2016-01-01

The replication of functional polymeric micro- and nanostructures requires a deep understanding of material and process interrelations. In this investigation the dewetting potential of a polymer is proposed as a simple rationale for estimation of the replicability of functional micro- and nanostr......The replication of functional polymeric micro- and nanostructures requires a deep understanding of material and process interrelations. In this investigation the dewetting potential of a polymer is proposed as a simple rationale for estimation of the replicability of functional micro......- and nanostructures by injection molding. The dewetting potential of a polymer is determined by integrating the spreading coefficient over the range from melt temperature to no-flow temperature. From all polymers tested, the lowest dewetting potential is calculated for PP and the highest for polymethylmethacrylate....... The dewetting potential correlates well with the replicated height of four different structures covering both the micro- and the nanorange on two different surfaces (brass and fluorocarbon modified nickel) and polymers with different spreading coefficients. It is clearly shown that a lower dewetting potential...

The due diligence process for acquiring and building power plants

International Nuclear Information System (INIS)

Vallen, M.A.; Bullinger, C.D.

1999-01-01

The restructuring of the electric generating business is continuing at a torrid pace. New auctions of generation portfolios are initiated almost monthly, and announcements of new development projects arrive almost daily. It has become imperative, then, that participants in both acquisitions and development projects become conversant with the necessary due diligence process, a complex and critical task that can mean the difference between success and failure. A thorough due diligence process allows bidder/developers to uncover value and quantify liabilities before bidding/building, translating into the best analysis possible and resulting in a winning investment decision. This article describes the process by which buyers and developers approach and manage the due diligence process as a key step in making their investment decision

Contract Law, Due Process, and the NCAA.

Science.gov (United States)

Dickerson, Jaffe D.; Chapman, Mayer

1978-01-01

The NCAA has enjoyed almost total freedom from judicial scrutiny of its rules, procedures, and official acts in large part because of its private nature as an unincorporated association. The function of the NCAA, California State University, Hayward v NCAA, and due process of the student-athlete are discussed. (MLW)

34 CFR 300.508 - Due process complaint.

Science.gov (United States)

2010-07-01

... attending; (5) A description of the nature of the problem of the child relating to the proposed or refused initiation or change, including facts relating to the problem; and (6) A proposed resolution of the problem... section, the hearing officer must make a determination on the face of the due process complaint of whether...

Designing Diameter-Modulated Heterostructure Nanowires of PbTe/Te by Controlled Dewetting.

Science.gov (United States)

Kumar, Abinash; Kundu, Subhajit; Samantaray, Debadarshini; Kundu, Paromita; Zanaga, Daniele; Bals, Sara; Ravishankar, N

2017-12-13

Heterostructures consisting of semiconductors with controlled morphology and interfaces find applications in many fields. A range of axial, radial, and diameter-modulated nanostructures have been synthesized primarily using vapor phase methods. Here, we present a simple wet chemical routine to synthesize heterostructures of PbTe/Te using Te nanowires as templates. A morphology evolution study for the formation of these heterostructures has been performed. On the basis of these control experiments, a pathway for the formation of these nanostructures is proposed. Reduction of a Pb precursor to Pb on Te nanowire templates followed by interdiffusion of Pb/Te leads to the formation of a thin shell of PbTe on the Te wires. Controlled dewetting of the thin shell leads to the formation of cube-shaped PbTe that is periodically arranged on the Te wires. Using control experiments, we show that different reactions parameters like rate of addition of the reducing agent, concentration of Pb precursor and thickness of initial Te nanowire play a critical role in controlling the spacing between the PbTe cubes on the Te wires. Using simple surface energy arguments, we propose a mechanism for the formation of the hybrid. The principles presented are general and can be exploited for the synthesis of other nanoscale heterostructures.

In-situ observation of equilibrium transitions in Ni films; agglomeration and impurity effects

Energy Technology Data Exchange (ETDEWEB)

Thron, Andrew M., E-mail: AMThron@lbl.gov [Department of Chemical Engineering and Materials Science, University of California, Davis, CA 95616 (United States); Greene, Peter; Liu, Kai [Department of Physics, University of California, Davis, CA 95616 (United States); Benthem, Klaus van [Department of Chemical Engineering and Materials Science, University of California, Davis, CA 95616 (United States)

2014-02-01

Dewetting of ultra-thin Ni films deposited on SiO{sub 2} layers was observed, in cross-section, by in situ scanning transmission electron microscopy. Holes were observed to nucleate by voids which formed at the Ni/SiO{sub 2} interface rather than at triple junctions at the free surface of the Ni film. Ni islands were observed to retract, in attempt to reach equilibrium on the SiO{sub 2} layer. SiO{sub 2} layers with 120 nm thickness were found to limit in situ heating experiments due to poor thermal conductivity of SiO{sub 2}. The formation of graphite was observed during the agglomeration of ultra-thin Ni films. Graphite was observed to wet both the free surface and the Ni/SiO{sub 2} interface of the Ni islands. Cr forms surface oxide layers on the free surface of the SiO{sub 2} layer and the Ni islands. Cr does not prevent the dewetting of Ni, however it will likely alter the equilibrium shape of the Ni islands. - Highlights: • In Situ observation of dewetting in ultra-thin Ni films sputtered on SiO{sub 2} layers. • Dewetting is observed in an edge-on position by in situ STEM. • Characterization of interface structure pre and post in situ annealing by STEM and EELS. • Analyze the effects of Cr{sub 1−x}O{sub x} and graphite impurities on the Ni film agglomeration. • Examine influence of the SiO{sub 2} layers on the dewetting process.

Fabrication of Au-Pd Core-shell Nanoparticles using Au Thin-Film Dewetting at High Temperature and Chemical Synthesis Methods

Energy Technology Data Exchange (ETDEWEB)

Kim, Min-Gyu; Lee, Hye-Jung; Oh, Yong-Jun [Hanbat National Univ., Daejeon (Korea, Republic of)

2016-07-15

Au-Pd bimetallic nanoparticles (NPs) have received a lot of attention in the fields of catalysts and hydrogen sensors. In this study, Au-Pd core-shell NP arrays were successfully fabricated using two steps: formation of the ordered array of Au NPs cores via solid-state dewetting of a Au thin film on a topographic silica substrate, and Pd shell formation via chemical synthesis using two different surfactants (CTAB and CTAC). Using the CTAB surfactant in particular, a 2-D composite structure comprised of an ordered array of Au-Pd NPs, with smaller Pd NPs on the nanoscopic gaps between the Au-Pd NPs, could be formed. This structure is expected to have potential application in resistance-base hydrogen sensors.

Solution-processed flexible NiO resistive random access memory device

Science.gov (United States)

Kim, Soo-Jung; Lee, Heon; Hong, Sung-Hoon

2018-04-01

Non-volatile memories (NVMs) using nanocrystals (NCs) as active materials can be applied to soft electronic devices requiring a low-temperature process because NCs do not require a heat treatment process for crystallization. In addition, memory devices can be implemented simply by using a patterning technique using a solution process. In this study, a flexible NiO ReRAM device was fabricated using a simple NC patterning method that controls the capillary force and dewetting of a NiO NC solution at low temperature. The switching behavior of a NiO NC based memory was clearly observed by conductive atomic force microscopy (c-AFM).

A Longitudinal Study of Special Education Due Process Hearings in Massachusetts

Directory of Open Access Journals (Sweden)

William H. Blackwell

2015-03-01

Full Text Available Of the three formal dispute resolution procedures provided by the Individuals With Disabilities Education Act of 2004(IDEA, due process hearings are the most costly in terms of time, fiscal resources, and impact on relationships between school personnel and parents. This study examined 258 due process hearings held over the past 8 years in Massachusetts to examine the characteristics of students at the center of these disputes, the issues that were addressed in the hearings, and the representation utilized by parents and school districts. The findings from this study indicated that (a Massachusetts school districts utilized attorney representation and won due process hearings at notably higher levels than parents, and (b the most frequently addressed issues at due process hearings were Individualized Education Program (IEP development/implementation and educational program placement, which are issues that represent the core mandate of IDEA to provide a free appropriate public education in the least restrictive environment (34 C.F.R. §300.300, 300.550. The authors present recommendations for policy actions and areas for future research.

Block copolymer assisted self-assembly of nanoparticles into Langmuir–Blodgett films: Effect of polymer concentration

International Nuclear Information System (INIS)

Martín-García, Beatriz; Velázquez, M. Mercedes

2013-01-01

We propose to use the self-assembly ability of a block copolymer to obtain CdSe quantum dots (QDs) structures of different morphology. The methodology proposed consist in transferring mixed Langmuir monolayers of QDs and the polymer poly (styrene-co-maleic anhydride) partial 2 buthoxy ethyl ester cumene terminated, PS-MA-BEE onto mica by the Langmuir–Blodgett (LB) methodology. The morphology of the LB films was analyzed by AFM and TEM measurements. Our results show that it is possible to modulate the self-assembly process by modifying the composition of the mixed Langmuir monolayer precursor of the LB film. The different morphologies are interpreted according to two different dewetting mechanisms, growth of holes and spinodal-like dewetting. The growth of holes dewetting process is driven by gravitatory effects and was observed for LB films obtained by transferring Langmuir monolayer of the smallest elasticity values in which the polymer is in brush conformation. The spinodal dewetting mechanism prevailed when the Langmuir monolayer presents the highest elasticity values. - Graphical abstract: Display Omitted - Highlights: • Effect of the surface composition on the LB films architecture. • QDs/polymer LB films morphology interpreted in terms of dewetting mechanism. • The dewetting mechanism depends on the Langmuir monolayer state

Block copolymer assisted self-assembly of nanoparticles into Langmuir–Blodgett films: Effect of polymer concentration

Energy Technology Data Exchange (ETDEWEB)

Martín-García, Beatriz; Velázquez, M. Mercedes, E-mail: mvsal@usal.es

2013-08-15

We propose to use the self-assembly ability of a block copolymer to obtain CdSe quantum dots (QDs) structures of different morphology. The methodology proposed consist in transferring mixed Langmuir monolayers of QDs and the polymer poly (styrene-co-maleic anhydride) partial 2 buthoxy ethyl ester cumene terminated, PS-MA-BEE onto mica by the Langmuir–Blodgett (LB) methodology. The morphology of the LB films was analyzed by AFM and TEM measurements. Our results show that it is possible to modulate the self-assembly process by modifying the composition of the mixed Langmuir monolayer precursor of the LB film. The different morphologies are interpreted according to two different dewetting mechanisms, growth of holes and spinodal-like dewetting. The growth of holes dewetting process is driven by gravitatory effects and was observed for LB films obtained by transferring Langmuir monolayer of the smallest elasticity values in which the polymer is in brush conformation. The spinodal dewetting mechanism prevailed when the Langmuir monolayer presents the highest elasticity values. - Graphical abstract: Display Omitted - Highlights: • Effect of the surface composition on the LB films architecture. • QDs/polymer LB films morphology interpreted in terms of dewetting mechanism. • The dewetting mechanism depends on the Langmuir monolayer state.

Dynamically slow processes in supercooled water confined between hydrophobic plates

Energy Technology Data Exchange (ETDEWEB)

Franzese, Giancarlo [Departamento de Fisica Fundamental, Universidad de Barcelona, Diagonal 647, Barcelona 08028 (Spain); Santos, Francisco de los, E-mail: gfranzese@ub.ed, E-mail: fdlsant@ugr.e [Departamento de Electromagnetismo y Fisica de la Materia, Universidad de Granada, Fuentenueva s/n, 18071 Granada (Spain)

2009-12-16

We study the dynamics of water confined between hydrophobic flat surfaces at low temperature. At different pressures, we observe different behaviors that we understand in terms of the hydrogen bond dynamics. At high pressure, the formation of the open structure of the hydrogen bond network is inhibited and the surfaces can be rapidly dried (dewetted) by formation of a large cavity with decreasing temperature. At lower pressure we observe strong non-exponential behavior of the correlation function, but with no strong increase of the correlation time. This behavior can be associated, on the one hand, to the rapid ordering of the hydrogen bonds that generates heterogeneities and, on the other hand, to the lack of a single timescale as a consequence of the cooperativity in the vicinity of the liquid-liquid critical point that characterizes the phase diagram at low temperature of the water model considered here. At very low pressures, the gradual formation of the hydrogen bond network is responsible for the large increase of the correlation time and, eventually, the dynamical arrest of the system, with a strikingly different dewetting process, characterized by the formation of many small cavities.

Dynamically slow processes in supercooled water confined between hydrophobic plates

International Nuclear Information System (INIS)

Franzese, Giancarlo; Santos, Francisco de los

2009-01-01

We study the dynamics of water confined between hydrophobic flat surfaces at low temperature. At different pressures, we observe different behaviors that we understand in terms of the hydrogen bond dynamics. At high pressure, the formation of the open structure of the hydrogen bond network is inhibited and the surfaces can be rapidly dried (dewetted) by formation of a large cavity with decreasing temperature. At lower pressure we observe strong non-exponential behavior of the correlation function, but with no strong increase of the correlation time. This behavior can be associated, on the one hand, to the rapid ordering of the hydrogen bonds that generates heterogeneities and, on the other hand, to the lack of a single timescale as a consequence of the cooperativity in the vicinity of the liquid-liquid critical point that characterizes the phase diagram at low temperature of the water model considered here. At very low pressures, the gradual formation of the hydrogen bond network is responsible for the large increase of the correlation time and, eventually, the dynamical arrest of the system, with a strikingly different dewetting process, characterized by the formation of many small cavities.

Constituents’ formal participation in the IASB’s due process: New insights into the impact of country and due process document characteristics

Directory of Open Access Journals (Sweden)

Michael Dobler

2016-09-01

Full Text Available This paper adopts a multi-issue/multi-period approach to provide new insights into key determinants of constituents’ formal participation in the due process of the International Accounting Standards Board (IASB. Based on an analysis of 8,825 comment letters submitted during the period 2006–2012, we find imbalances in the representation of constituents. Multiple regressions reveal that among various economic and cultural variables equity market capitalization and the society’s level of individualism are the key drivers of the country-level of constituents’ participation, and each variable has explanatory power over the other. The level of constituents’ participation is positively associated with the number of input opportunities offered by a due process document but unrelated to the complexity of a standard-setting project. The results are robust across various sub-samples and to additional sensitivity tests. Our findings indicate threats to the input legitimacy of the IASB and suggest avenues to stimulate constituents’ participation.

Teaching about Due Process of Law. ERIC Digest.

Science.gov (United States)

Vontz, Thomas S.

Fundamental constitutional and legal principles are central to effective instruction in the K-12 social studies curriculum. To become competent citizens, students need to develop an understanding of the principles on which their society and government are based. Few principles are as important in the social studies curriculum as due process of…

Mn-doped Ge self-assembled quantum dots via dewetting of thin films

Energy Technology Data Exchange (ETDEWEB)

Aouassa, Mansour, E-mail: mansour.aouassa@yahoo.fr [LMON, Faculté des Sciences de Monastir, Avenue de l’environnement Monastir 5019 (Tunisia); Jadli, Imen [LMON, Faculté des Sciences de Monastir, Avenue de l’environnement Monastir 5019 (Tunisia); Bandyopadhyay, Anup [Department of Mechanical Engineering, Texas A& M University, College Station, TX 77843 (United States); Kim, Sung Kyu [Center for Nanomaterials and Chemical Reactions, Institute for Basic Science (IBS), Yuseong-daero 1689-gil, Yuseong-gu, Daejeon (Korea, Republic of); Department of Materials Science and Engineering, KAIST 291 Daehak-ro, Yuseong-gu, Daejeon (Korea, Republic of); Karaman, Ibrahim [Department of Mechanical Engineering, Texas A& M University, College Station, TX 77843 (United States); Lee, Jeong Yong [Center for Nanomaterials and Chemical Reactions, Institute for Basic Science (IBS), Yuseong-daero 1689-gil, Yuseong-gu, Daejeon (Korea, Republic of); Department of Materials Science and Engineering, KAIST 291 Daehak-ro, Yuseong-gu, Daejeon (Korea, Republic of)

2017-03-01

Highlights: • We report the new fabrication approach for producing a self- assembled Mn dpoed Ge quantum dots (QDs) on SiO{sub 2} thin film with a Curie temperature above room temperature. These magnetic QDs are crystalline, monodisperse and have a well-defined shape and a controlled size. The investigation opens new routes for elaboration of self-assembled magnetic nanocrystals - Abstract: In this study, we demonstrate an original elaboration route for producing a Mn-doped Ge self-assembled quantum dots on SiO{sub 2} thin layer for MOS structure. These magnetic quantum dots are elaborated using dewetting phenomenon at solid state by Ultra-High Vacuum (UHV) annealing at high temperature of an amorphous Ge:Mn (Mn: 40%) nanolayer deposed at very low temperature by high-precision Solid Source Molecular Beam Epitaxy on SiO{sub 2} thin film. The size of quantum dots is controlled with nanometer scale precision by varying the nominal thickness of amorphous film initially deposed. The magnetic properties of the quantum-dots layer have been investigated by superconducting quantum interference device (SQUID) magnetometry. Atomic force microscopy (AFM), x-ray energy dispersive spectroscopy (XEDS) and transmission electron microscopy (TEM) were used to examine the nanostructure of these materials. Obtained results indicate that GeMn QDs are crystalline, monodisperse and exhibit a ferromagnetic behavior with a Curie temperature (TC) above room temperature. They could be integrated into spintronic technology.

Inherent-opening-controlled pattern formation in carbon nanotube arrays

International Nuclear Information System (INIS)

Huang Xiao; Zhou, Jijie J; Sansom, Elijah; Gharib, Morteza; Haur, Sow Chorng

2007-01-01

We have introduced inherent openings into densely packed carbon nanotube arrays to study self-organized pattern formation when the arrays undergo a wetting-dewetting treatment from nanotube tips. These inherent openings, made of circular or elongated hollows in nanotube mats, serve as dewetting centres, from where liquid recedes from. As the dewetting centres initiate dry zones and the dry zones expand, surrounding nanotubes are pulled away from the dewetting centres by liquid surface tension. Among short nanotubes, the self-organized patterns are consistent with the shape of the inherent openings, i.e. slender openings lead to elongated trench-like structures, and circular holes result in relatively round nest-like arrangements. Nanotubes in a relatively high mat are more connected, like in an elastic body, than those in a short mat. Small cracks often initialize themselves in a relatively high mat, along two or more adjacent round openings; each of the cracks evolves into a trench as liquid dries up. Self-organized pattern control with inherent openings needs to initiate the dewetting process above the nanotube tips. If there is no liquid on top, inherent openings barely enlarge themselves after the wetting-dewetting treatment

Single-machine common/slack due window assignment problems with linear decreasing processing times

Science.gov (United States)

Zhang, Xingong; Lin, Win-Chin; Wu, Wen-Hsiang; Wu, Chin-Chia

2017-08-01

This paper studies linear non-increasing processing times and the common/slack due window assignment problems on a single machine, where the actual processing time of a job is a linear non-increasing function of its starting time. The aim is to minimize the sum of the earliness cost, tardiness cost, due window location and due window size. Some optimality results are discussed for the common/slack due window assignment problems and two O(n log n) time algorithms are presented to solve the two problems. Finally, two examples are provided to illustrate the correctness of the corresponding algorithms.

25 CFR 42.6 - When does due process require a formal disciplinary hearing?

Science.gov (United States)

2010-04-01

... 25 Indians 1 2010-04-01 2010-04-01 false When does due process require a formal disciplinary... RIGHTS § 42.6 When does due process require a formal disciplinary hearing? Unless local school policies and procedures provide for less, a formal disciplinary hearing is required before a suspension in...

Dynamics of ultrathin metal films on amorphous substrates under fast thermal processing

International Nuclear Information System (INIS)

Favazza, Christopher; Kalyanaraman, Ramki; Sureshkumar, Radhakrishna

2007-01-01

A mathematical model is developed to analyze the growth/decay rate of surface perturbations of an ultrathin metal film on an amorphous substrate (SiO 2 ). The formulation combines the approach of Mullins [W. W. Mullins, J. Appl. Phys. 30, 77 (1959)] for bulk surfaces, in which curvature-driven mass transport and surface deformation can occur by surface/volume diffusion and evaporation-condensation processes, with that of Spencer et al. [B. J. Spencer, P. W. Voorhees, and S. H. Davis, Phys. Rev. Lett. 67, 26 (1991)] to describe solid-state transport in thin films under epitaxial strain. Modifications of the Mullins model to account for thin-film boundary conditions result in qualitatively different dispersion relationships especially in the limit as kh o o is the unperturbed film height. The model is applied to study the relative rate of solid-state mass transport as compared to that of liquid phase dewetting in a thin film subjected to a fast thermal pulse. Specifically, we have recently shown that multiple cycles of nanosecond (ns) pulsed laser melting and resolidification of ultrathin metal films on amorphous substrates can lead to the formation of various types of spatially ordered nanostructures [J. Trice, D. Thomas, C. Favazza, R. Sureshkumar, and R. Kalyanaraman, Phys. Rev. B 75, 235439 (2007)]. The pattern formation has been attributed to the dewetting of the thin film by a hydrodynamic instability. In such experiments the film is in the solid state during a substantial fraction of each thermal cycle. However, results of a linear stability analysis based on the aforementioned model suggest that solid-state mass transport has a negligible effect on morphological changes of the surface. Further, a qualitative analysis of the effect of thermoelastic stress, induced by the rapid temperature changes in the film-substrate bilayer, suggests that stress relaxation does not appreciably contribute to surface deformation. Hence, surface deformation caused by liquid

"Ingraham v. Wright" and the Decline of Due Process.

Science.gov (United States)

Clark, Gerard J.

1978-01-01

Suggests that the constitutional questions in "Ingraham vs Wright" lend credence to a concern that the Court is seeking to eliminate all due process intervention outside of the incorporation and privacy cases and to limit even these cases to defenses of a criminal prosecution. Available from Suffolk University Law Review Office, 41…

Due Process in the Realm of Higher Education: Considerations for Dealing with Students Rights

Science.gov (United States)

Fishner, Jason T.

2006-01-01

Court decisions have laid out expectations of what due process procedures need to be followed in student disciplinary cases and academic dismissal cases due to poor academic performance. This paper will give show where due process comes from and how it found its way into higher education. It will show that there are differences in the ways public…

Water Dynamics and Dewetting Transitions in the Small Mechanosensitive Channel MscS

Science.gov (United States)

Anishkin, Andriy; Sukharev, Sergei

2004-01-01

The dynamics of confined water in capillaries and nanotubes suggests that gating of ion channels may involve not only changes of the pore geometry, but also transitions between water-filled and empty states in certain locations. The recently solved heptameric structure of the small mechanosensitive channel of Escherichia coli, MscS, has revealed a relatively wide (7–15 Å) yet highly hydrophobic transmembrane pore. Continuum estimations based on the properties of pore surface suggest low conductance and a thermodynamic possibility of dewetting. To test the predictions we performed molecular dynamics simulations of MscS filled with flexible TIP3P water. Irrespective to the initial conditions, several independent 6-ns simulations converged to the same stable state with the pore water-filled in the wider part, but predominantly empty in the narrow hydrophobic part, displaying intermittent vapor-liquid transitions. The polar gain-of-function substitution L109S in the constriction resulted in a stable hydration of the entire pore. Steered passages of Cl− ions through the narrow part of the pore consistently produced partial ion dehydration and required a force of 200–400 pN to overcome an estimated barrier of 10–20 kcal/mole, implying negligibly low conductance. We conclude that the crystal structure of MscS does not represent an open state. We infer that MscS gate, which is similar to that of the nicotinic ACh receptor, involves a vapor-lock mechanism where limited changes of geometry or surface polarity can locally switch the regime between water-filled (conducting) and empty (nonconducting) states. PMID:15111405

Sensitivity of Process Design due to Uncertainties in Property Estimates

DEFF Research Database (Denmark)

Hukkerikar, Amol; Jones, Mark Nicholas; Sarup, Bent

2012-01-01

The objective of this paper is to present a systematic methodology for performing analysis of sensitivity of process design due to uncertainties in property estimates. The methodology provides the following results: a) list of properties with critical importance on design; b) acceptable levels of...... in chemical processes. Among others vapour pressure accuracy for azeotropic mixtures is critical and needs to be measured or estimated with a ±0.25% accuracy to satisfy acceptable safety levels in design....

Measured spatial variability of beach erosion due to aeolian processes.

NARCIS (Netherlands)

de Vries, S.; Verheijen, A.H.; Hoonhout, B.M.; Vos, S.E.; Cohn, Nicholas; Ruggiero, P; Aagaard, T.; Deigaard, R.; Fuhrman, D.

2017-01-01

This paper shows the first results of measured spatial variability of beach erosion due to aeolian processes during the recently conducted SEDEX2 field experiment at Long Beach, Washington, U.S.A.. Beach erosion and sedimentation were derived using series of detailed terrestrial LIDAR measurements

Basic Substantive Law for Paralegals: Contracts, Torts, and Due Process.

Science.gov (United States)

Marcin, Raymond B.

Part of the paralegal, or legal assistant, training materials prepared by the National Paralegal Institution under a Federal grant, the text comprises an overview of the basic legal concepts usually found in introductory law courses concerning contracts, torts, and the due process area of constitutional law. Part 1, Contracts, covers: definition,…

Polymer/surfactant assisted self-assembly of nanoparticles into Langmuir–Blodgett films

International Nuclear Information System (INIS)

Alejo, T.; Merchán, M.D.; Velázquez, M.M.; Pérez-Hernández, J.A.

2013-01-01

We studied the ability of poly(octadecene-co-maleic anhydride) (PMAO) and a Gemini surfactant [C 18 H 37 (CH 3 ) 2 N + Br − –(CH 2 ) 2 –N + Br − (CH 3 ) 2 C 18 H 37 ] (18-2-18) to assist in the self-assembly process of CdSe quantum dots (QDs) at the air–water interface. Results show that, while QD agglomeration is generally inhibited by the addition of these components to the Langmuir monolayer of QDs, structure of the film transferred onto mica by the Langmuir–Blodgett method is strongly affected by the dewetting process. Nucleation-and-growth of holes and spinodal-like dewetting were respectively observed in the presence of either PMAO or 18-2-18. When PMAO/18-2-18 mixtures were used, both mechanisms were allowed; nevertheless, even in films prepared with mixtures of low polymer contents, characteristic morphology from the polymer dewetting route prevailed. Highlights: ► Effect of the composition on the LB films of QDs/polymer. ► Effect of the composition on the LB films of QDs/Gemini surfactant. ► Dewetting mechanisms

Dynamics of ultrathin metal films on amorphous substrates under fast thermal processing

Science.gov (United States)

Favazza, Christopher; Kalyanaraman, Ramki; Sureshkumar, Radhakrishna

2007-11-01

A mathematical model is developed to analyze the growth/decay rate of surface perturbations of an ultrathin metal film on an amorphous substrate (SiO2). The formulation combines the approach of Mullins [W. W. Mullins, J. Appl. Phys. 30, 77 (1959)] for bulk surfaces, in which curvature-driven mass transport and surface deformation can occur by surface/volume diffusion and evaporation-condensation processes, with that of Spencer etal . [B. J. Spencer, P. W. Voorhees, and S. H. Davis, Phys. Rev. Lett. 67, 26 (1991)] to describe solid-state transport in thin films under epitaxial strain. Modifications of the Mullins model to account for thin-film boundary conditions result in qualitatively different dispersion relationships especially in the limit as kho≪1, where k is the wavenumber of the perturbation and ho is the unperturbed film height. The model is applied to study the relative rate of solid-state mass transport as compared to that of liquid phase dewetting in a thin film subjected to a fast thermal pulse. Specifically, we have recently shown that multiple cycles of nanosecond (ns) pulsed laser melting and resolidification of ultrathin metal films on amorphous substrates can lead to the formation of various types of spatially ordered nanostructures [J. Trice, D. Thomas, C. Favazza, R. Sureshkumar, and R. Kalyanaraman, Phys. Rev. B 75, 235439 (2007)]. The pattern formation has been attributed to the dewetting of the thin film by a hydrodynamic instability. In such experiments the film is in the solid state during a substantial fraction of each thermal cycle. However, results of a linear stability analysis based on the aforementioned model suggest that solid-state mass transport has a negligible effect on morphological changes of the surface. Further, a qualitative analysis of the effect of thermoelastic stress, induced by the rapid temperature changes in the film-substrate bilayer, suggests that stress relaxation does not appreciably contribute to surface

Fabrication of core-shell nanostructures via silicon on insulator dewetting and germanium condensation: towards a strain tuning method for SiGe-based heterostructures in a three-dimensional geometry.

Science.gov (United States)

Naffouti, Meher; David, Thomas; Benkouider, Abdelmalek; Favre, Luc; Cabie, Martiane; Ronda, Antoine; Berbezier, Isabelle; Abbarchi, Marco

2016-07-29

We report on a novel method for the implementation of core-shell SiGe-based nanocrystals combining silicon on insulator dewetting in a molecular beam epitaxy reactor with an ex situ Ge condensation process. With an in situ two-step process (annealing and Ge deposition) we produce two families of islands on the same sample: Si-rich, formed during the first step and, all around them, Ge-rich formed after Ge deposition. By increasing the amount of Ge deposited on the annealed samples from 0 to 18 monolayers, the islands' shape in the Si-rich zones can be tuned from elongated and flat to more symmetric and with a larger vertical aspect ratio. At the same time, the spatial extension of the Ge-rich zones is progressively increased as well as the Ge content in the islands. Further processing by ex situ rapid thermal oxidation results in the formation of a core-shell composition profile in both Si and Ge-rich zones with atomically sharp heterointerfaces. The Ge condensation induces a Ge enrichment of the islands' shell of up to 50% while keeping a pure Si core in the Si-rich zones and a ∼25% SiGe alloy in the Ge-rich ones. The large lattice mismatch between core and shell, the absence of dislocations and the islands' monocrystalline nature render this novel class of nanostructures a promising device platform for strain-based band-gap engineering. Finally, this method can be used for the implementation of ultralarge scale meta-surfaces with dielectric Mie resonators for light manipulation at the nanoscale.

How metal films de-wet substrates-identifying the kinetic pathways and energetic driving forces

International Nuclear Information System (INIS)

McCarty, Kevin F; Hamilton, John C; Thuermer, Konrad; Jones, Frank; Talin, A Alec; Bartelt, Norman C; Sato, Yu; K Schmid, Andreas; Saa, Angela; Figuera, Juan de la; Stumpf, Roland

2009-01-01

We study how single-crystal chromium films of uniform thickness on W(110) substrates are converted to arrays of three-dimensional (3D) Cr islands during annealing. We use low-energy electron microscopy (LEEM) to directly observe a kinetic pathway that produces trenches that expose the wetting layer. Adjacent film steps move simultaneously uphill and downhill relative to the staircase of atomic steps on the substrate. This step motion thickens the film regions where steps advance. Where film steps retract, the film thins, eventually exposing the stable wetting layer. Since our analysis shows that thick Cr films have a lattice constant close to bulk Cr, we propose that surface and interface stress provide a possible driving force for the observed morphological instability. Atomistic simulations and analytic elastic models show that surface and interface stress can cause a dependence of film energy on thickness that leads to an instability to simultaneous thinning and thickening. We observe that de-wetting is also initiated at bunches of substrate steps in two other systems, Ag/W(110) and Ag/Ru(0001). We additionally describe how Cr films are converted into patterns of unidirectional stripes as the trenches that expose the wetting layer lengthen along the W[001] direction. Finally, we observe how 3D Cr islands form directly during film growth at elevated temperature. The Cr mesas (wedges) form as Cr film steps advance down the staircase of substrate steps, another example of the critical role that substrate steps play in 3D island formation.

Polymer/surfactant assisted self-assembly of nanoparticles into Langmuir–Blodgett films

Energy Technology Data Exchange (ETDEWEB)

Alejo, T.; Merchán, M.D. [Departamento de Química Física, Facultad de Ciencias Químicas, Universidad de Salamanca, Plaza de los Caídos s/n, E-37008 Salamanca (Spain); Velázquez, M.M., E-mail: mvsal@usal.es [Departamento de Química Física, Facultad de Ciencias Químicas, Universidad de Salamanca, Plaza de los Caídos s/n, E-37008 Salamanca (Spain); Pérez-Hernández, J.A. [Centro de Láseres Pulsados Ultraintensos (CLPU), E-37008 Salamanca (Spain)

2013-02-15

We studied the ability of poly(octadecene-co-maleic anhydride) (PMAO) and a Gemini surfactant [C{sub 18}H{sub 37} (CH{sub 3}){sub 2}N{sup +}Br{sup −}–(CH{sub 2}){sub 2}–N{sup +}Br{sup −}(CH{sub 3}){sub 2} C{sub 18}H{sub 37}] (18-2-18) to assist in the self-assembly process of CdSe quantum dots (QDs) at the air–water interface. Results show that, while QD agglomeration is generally inhibited by the addition of these components to the Langmuir monolayer of QDs, structure of the film transferred onto mica by the Langmuir–Blodgett method is strongly affected by the dewetting process. Nucleation-and-growth of holes and spinodal-like dewetting were respectively observed in the presence of either PMAO or 18-2-18. When PMAO/18-2-18 mixtures were used, both mechanisms were allowed; nevertheless, even in films prepared with mixtures of low polymer contents, characteristic morphology from the polymer dewetting route prevailed. Highlights: ► Effect of the composition on the LB films of QDs/polymer. ► Effect of the composition on the LB films of QDs/Gemini surfactant. ► Dewetting mechanisms.

20 CFR 670.545 - How does Job Corps ensure that students receive due process in disciplinary actions?

Science.gov (United States)

2010-04-01

... receive due process in disciplinary actions? 670.545 Section 670.545 Employees' Benefits EMPLOYMENT AND... process in disciplinary actions? The center operator must ensure that all students receive due process in disciplinary proceedings according to procedures developed by the Secretary. These procedures must include, at...

The due-diligence process of purchasing or buying into a dental practice.

Science.gov (United States)

Conner, Vincent L

2003-01-01

A due-diligence or evaluation process is necessary when assessing a practice purchase opportunity. The standards for assessing the investment remain the same whether the buyer is purchasing a practice outright or buying a co-ownership interest.

Standard Setting as Psychometric Due Process: Going a Little Further Down an Uncertain Road.

Science.gov (United States)

Cizek, Gregory J.

The concept of due process provides an analogy for the process of standard setting that emphasizes many of the procedural and substantive elements of the process over technical and statistical concerns. Surely such concerns can and should continue to be addressed. However, a sound rationale for standard setting does not rest on this foundation.…

Due Diligence Processes for Public Acquisition of Mining-Impacted Landscapes

Science.gov (United States)

Martin, E.; Monohan, C.; Keeble-Toll, A. K.

2016-12-01

The acquisition of public land is critical for achieving conservation and habitat goals in rural regions projected to experience continuously high rates of population growth. To ensure that public funds are utilized responsibly in the purchase of conservation easements appropriate due diligence processes must be established that limit landowner liability post-acquisition. Traditional methods of characterizing contamination in regions where legacy mining activities were prevalent may not utilize current scientific knowledge and understanding of contaminant fate, transport and bioavailability, and therefore are likely to have type two error. Agency prescribed assessment methods utilized under CERLA in many cases fail to detect contamination that presents liability issues by failing to require water quality sampling that would reveal offsite transport potential of contaminants posing human health risks, including mercury. Historical analysis can be used to inform judgmental sampling to identify hotspots and contaminants of concern. Land acquisition projects at two historic mine sites in Nevada County, California, the Champion Mine Complex and the Black Swan Preserve have established the necessity of re-thinking due diligence processes for mining-impacted landscapes. These pilot projects demonstrate that pre-acquisition assessment in the Gold Country must include judgmental sampling and evaluation of contaminant transport. Best practices using the current scientific knowledge must be codified by agencies, consultants, and NGOs in order to ensure responsible use of public funds and to safeguard public health.

The Analytical Pragmatic Structure of Procedural Due Process: A Framework for Inquiry in Administrative Decision Making.

Science.gov (United States)

Fisher, James E.; Sealey, Ronald W.

The study describes the analytical pragmatic structure of concepts and applies this structure to the legal concept of procedural due process. This structure consists of form, purpose, content, and function. The study conclusions indicate that the structure of the concept of procedural due process, or any legal concept, is not the same as the…

Mediation and Due Process Procedures in Special Education: An Analysis of State Policies. Final Report. Project FORUM.

Science.gov (United States)

Ahearn, Eileen M.

This survey of 50 states and 3 of 10 non-state U.S. jurisdictions concerning state due process procedures focuses mainly on the use of mediation as a form of dispute resolution that offers an alternative to due process hearings in special education. A background section discusses the definition of mediation and the mediation process. Survey…

In situ laser processing in a scanning electron microscope

Energy Technology Data Exchange (ETDEWEB)

Roberts, Nicholas A.; Magel, Gregory A.; Hartfield, Cheryl D.; Moore, Thomas M.; Fowlkes, Jason D.; Rack, Philip D. [Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996 (United States) and Omniprobe, Inc., an Oxford Instruments Company, 10410 Miller Rd., Dallas, Texas 75238 (United States); Omniprobe, Inc., an Oxford Instruments Company, 10410 Miller Rd., Dallas, Texas 75238 (United States); Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996 (United States) and Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)

2012-07-15

Laser delivery probes using multimode fiber optic delivery and bulk focusing optics have been constructed and used for performing materials processing experiments within scanning electron microscope/focused ion beam instruments. Controlling the current driving a 915-nm semiconductor diode laser module enables continuous or pulsed operation down to sub-microsecond durations, and with spot sizes on the order of 50 {mu}m diameter, achieving irradiances at a sample surface exceeding 1 MW/cm{sup 2}. Localized laser heating has been used to demonstrate laser chemical vapor deposition of Pt, surface melting of silicon, enhanced purity, and resistivity via laser annealing of Au deposits formed by electron beam induced deposition, and in situ secondary electron imaging of laser induced dewetting of Au metal films on SiO{sub x}.

Insights into the IASB due process: the influence of country characteristics on constituents’ formal participation

Directory of Open Access Journals (Sweden)

Karsten Eisenschmidt

2017-12-01

Full Text Available The paper explores the impact of country characteristics on constituents’ formal participation in the IASB’s due process. We hypothesize that there is an association between the level of constituents’ partic- ipation and (1 the level of economic development, and (2 the cultural characteristics of the country of origin. We use a number of comment letters (CLs and their length as proxies for constituents’ formal participation in the IASB’s due process. The results indicate that economic development (equity market capitalization is the most important explanatory factor for the different levels of participation. In con- trast, the cultural characteristics measured by Hofstede’s cultural framework can only partially explain that differences. Only individualism is a significant positive influence factor for the level of constituents’ participation. The results of our descriptive analysis for the CLs and the information input provided show that there is still a lack of participation in the IASB’s due process. Despite the huge impact of accounting norms on societies, only a limited number of constituents participate, and some constituent groups, like users or academics, participate less.

The Procedural Queer: Substantive Due Process, "Lawrence v. Texas," and Queer Rhetorical Futures

Science.gov (United States)

Campbell, Peter Odell

2012-01-01

This essay discusses Justice Anthony M. Kennedy's choice to foreground arguments from due process rather than equal protection in the majority opinion in Lawrence v. Texas. Kennedy's choice can realize constitutional legal doctrine that is more consistent with radical queer politics than arguments from equal protection. Unlike some recent…

Instability of hydrophobic and viscoelastic polymer thin films in water at room temperature

International Nuclear Information System (INIS)

Liu Dan; Wang Tao

2013-01-01

The instability of a polyisoprene (PI) thin film on a silicon substrate at room temperature in an aqueous environment was investigated by atomic force microscopy and optical microscopy. The instability mechanism changes from spinodal dewetting to hole nucleation with increasing film thickness, with the transitional thickness found to be around 46–50 nm. For PI films ≥50 nm, the dewetting was observed to proceed via successive stages of hole nucleation and growth, hole coalescence, cellular pattern formation and droplet formation. There is also a slowing down in the rate of the PI dewetting process and an increase in the pattern size as the film thickness is increased. In those films with observable holes, we also observed the coexistence of fine cellular cracking that is on a much smaller scale of hundreds of nanometres and extends only a few nanometres in depth from the film surface. (paper)

Reversibility of temperature driven discrete layer-by-layer formation of dioctyl-benzothieno-benzothiophene films.

Science.gov (United States)

Dohr, M; Ehmann, H M A; Jones, A O F; Salzmann, I; Shen, Q; Teichert, C; Ruzié, C; Schweicher, G; Geerts, Y H; Resel, R; Sferrazza, M; Werzer, O

2017-03-22

Film forming properties of semiconducting organic molecules comprising alkyl-chains combined with an aromatic unit have a decisive impact on possible applications in organic electronics. In particular, knowledge on the film formation process in terms of wetting or dewetting, and the precise control of these processes, is of high importance. In the present work, the subtle effect of temperature on the morphology and structure of dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) films deposited on silica surfaces by spin coating is investigated in situ via X-ray diffraction techniques and atomic force microscopy. Depending on temperature, bulk C8-BTBT exhibits a crystalline, a smectic A and an isotropic phase. Heating of thin C8-BTBT layers at temperatures below the smectic phase transition temperature leads to a strong dewetting of the films. Upon approaching the smectic phase transition, the molecules start to rewet the surface in the form of discrete monolayers with a defined number of monolayers being present at a given temperature. The wetting process and layer formation is well defined and thermally stable at a given temperature. On cooling the reverse effect is observed and dewetting occurs. This demonstrates the full reversibility of the film formation behavior and reveals that the layering process is defined by an equilibrium thermodynamic state, rather than by kinetic effects.

Dynamics of metal nanodroplets; Dynamik metallischer Nanotroepfchen

Energy Technology Data Exchange (ETDEWEB)

Habenicht, Anja

2007-11-12

In this work flat metal nanostructures on inert substrates like glass, silicon or graphite have been illuminated by single intensive laser pulses with fluences above the melting threshold. The liquid structures produced in this way are far from their equilibrium shape and a dewetting process starts. On a timescale of a few nanoseconds, the liquid but still flat nanostructure transforms toward a sphere. During this deformation the center of mass moves upward, which can lead to detachment of droplets from the surface due to inertia. The velocity of the detaching nanodroplets is measured with a light barrier technique. The experiment shows that the velocity of the detached droplet is constant over a large range of laser energy densities. This supports the model of a dewetting driven process: The droplet gains surface energy by transforming toward a sphere which is then converted into kinetic energy. Loss mechanisms like excitation of droplet oscillations and dissipation due to viscous friction are discussed. With this model the escape velocity was predicted for nanostructures of different materials and forms, hence other material parameters like surface tension or density and has been confirmed experimentally. The droplets are landed on another surface. Two scenarios are found: There are spheres with a similar shape as the droplet or heavily deformed structures. These structures of splashing and rebounding are identical to the structures which can be observed in the macroscopic impact of liquids. The two scenarios can be explained by different temperatures of the droplets when reaching the substrate. (orig.)

Maximum Lateness Scheduling on Two-Person Cooperative Games with Variable Processing Times and Common Due Date

OpenAIRE

Liu, Peng; Wang, Xiaoli

2017-01-01

A new maximum lateness scheduling model in which both cooperative games and variable processing times exist simultaneously is considered in this paper. The job variable processing time is described by an increasing or a decreasing function dependent on the position of a job in the sequence. Two persons have to cooperate in order to process a set of jobs. Each of them has a single machine and their processing cost is defined as the minimum value of maximum lateness. All jobs have a common due ...

Due Process and Higher Education: A Systemic Approach to Fair Decision Making. ERIC Digest.

Science.gov (United States)

Stevens, Ed

University officials and faculty are frequently required to make decisions based on interpretations of disputed facts. By applying the concept of due process within the context of higher education, they can meet legal challenges of contract and constitutional law and the pedagogical demand for justice. To guide their efforts, decision makers can…

Swift heavy ion induced de wetting of metal oxide thin films on silicon

International Nuclear Information System (INIS)

Bolse, T.; Paulus, H.; Bolse, W.

2006-01-01

We have observed that thin oxide coatings (NiO, Fe 2 O 3 ) tend to dewet their Si substrate when being bombarded with swift heavy ions (350-600 MeV Au ions) even though the irradiation was carried out about 80 K and hence, the films never reached their melting point. Scanning electron and atomic force microscopy reveal a surprising similarity of the dewetting morphologies with those observed for molten polymer films on Si, which have recently been reported by others [S. Herminghaus, K. Jakobs, K. Mecke, J. Bischof, A. Fery, M. Ibn-Elhaj, S. Schlagowsky, Science 282 (1998) 916; R. Seemann, S. Herminghaus, K. Jacobs, J. Phys.: Condens. Matter 13 (2001) 4925]. Like in that cases also here heterogeneous and homogeneous hole nucleation could be identified. Heterogeneous nucleation is less pronounced in Fe 2 O 3 /Si than in NiO/Si. The occurrence of spinodal-like dewetting cannot be detected unambiguously. The dewetting kinetics were determined by means of Rutherford backscattering spectroscopy and found to slightly differ for the two compounds. The dewetting kinetics as well as the final dewetting pattern strongly depend on the initial film thicknesses. No dewetting occurs for film thicknesses above about 150 nm, while for very small thicknesses below about 40 nm the film decays into nm-sized spherical droplets. At intermediate film thicknesses percolated networks of small oxide bridges are formed

Formal participation in the IASB's due process of standard setting : A multi-issue/multiperiod analysis

NARCIS (Netherlands)

Jorissen, A.; Lybaert, N.; Orens, R.; van der Tas, L.G.

2012-01-01

This paper sets out to enquire about the nature of constituents' participation in the IASB's due process in terms of representation (constituents' diversity and characteristics) and drivers to participate. We choose to adopt a multi-issue/multi-period approach to investigate constituents' formal

Evidences of landslide earthquake triggering due to self-excitation process

Science.gov (United States)

Bozzano, F.; Lenti, L.; Martino, Salvatore; Paciello, A.; Scarascia Mugnozza, G.

2011-06-01

The basin-like setting of stiff bedrock combined with pre-existing landslide masses can contribute to seismic amplifications in a wide frequency range (0-10 Hz) and induce a self-excitation process responsible for earthquake-triggered landsliding. Here, the self-excitation process is proposed to justify the far-field seismic trigger of the Cerda landslide (Sicily, Italy) which was reactivated by the 6th September 2002 Palermo earthquake ( M s = 5.4), about 50 km far from the epicentre. The landslide caused damage to farm houses, roads and aqueducts, close to the village of Cerda, and involved about 40 × 106 m3 of clay shales; the first ground cracks due to the landslide movement formed about 30 min after the main shock. A stress-strain dynamic numerical modelling, performed by FDM code FLAC 5.0, supports the notion that the combination of local geological setting and earthquake frequency content played a fundamental role in the landslide reactivation. Since accelerometric records of the triggering event are not available, dynamic equivalent inputs have been used for the numerical modelling. These inputs can be regarded as representative for the local ground shaking, having a PGA value up to 0.2 m/s2, which is the maximum expected in 475 years, according to the Italian seismic hazard maps. A 2D numerical modelling of the seismic wave propagation in the Cerda landslide area was also performed; it pointed out amplification effects due to both the structural setting of the stiff bedrock (at about 1 Hz) and the pre-existing landslide mass (in the range 3-6 Hz). The frequency peaks of the resulting amplification functions ( A( f)) fit well the H/ V spectral ratios from ambient noise and the H/ H spectral ratios to a reference station from earthquake records, obtained by in situ velocimetric measurements. Moreover, the Fourier spectra of earthquake accelerometric records, whose source and magnitude are consistent with the triggering event, show a main peak at about 1 Hz

Effects of surveillance on the rule of law, due process and the presumption of innocence

NARCIS (Netherlands)

Galetta, Antonella; de Hert, Paul; Wright, D.; Kreissl, R.

2015-01-01

This contribution focuses on the impact of surveillance on the rule of law, due process and the presumption of innocence, key values and principles of a democratic order. It illustrates how they are implemented and enforced in contemporary surveillance societies, while referring to European law and

Due Process in the Internet Jurisdiction: Landing Softly on the Other Side of the Looking Glass

National Research Council Canada - National Science Library

Kolb, Natalie A

2001-01-01

.... However, even if a U.S. state court exercises improper jurisdiction over a non-resident defendant in an Internet case, due process protection can be revived at the choice-of-law and enforcement stages of the judicial proceeding...

Enhanced light scattering in Si nanostructures produced by pulsed laser irradiation

Energy Technology Data Exchange (ETDEWEB)

Sberna, P. M.; Scapellato, G. G.; Boninelli, S.; Miritello, M.; Crupi, I.; Bruno, E.; Privitera, V.; Simone, F.; Mirabella, S. [MATIS IMM-CNR and Dipartimento di Fisica e Astronomia, Università di Catania, via S. Sofia 64, 95123 Catania (Italy); Piluso, N. [IMM-CNR, VIII strada 5, 95121 Catania (Italy)

2013-11-25

An innovative method for Si nanostructures (NS) fabrication is proposed, through nanosecond laser irradiation (λ = 532 nm) of thin Si film (120 nm) on quartz. Varying the laser energy fluences (425–1130 mJ/cm{sup 2}) distinct morphologies of Si NS appear, going from interconnected structures to isolated clusters. Film breaking occurs through a laser-induced dewetting process. Raman scattering is enhanced in all the obtained Si NS, with the largest enhancement in interconnected Si structures, pointing out an increased trapping of light due to multiple scattering. The reported method is fast, scalable and cheap, and can be applied for light management in photovoltaics.

Understanding Coatings that Protect Plasmonic Structures for Materials Characterization and Detection and Identification of Chemical, Biological and Explosive Agents

Science.gov (United States)

2013-04-11

require the rough metal films that result from dewetting , the silver films for X-ray photoelectron spectroscopy (XPS) and XR study were made thick...enough to avoid dewetting , since smooth, planar films were needed for those techniques. The preparation conditions for these flat samples were the same...spectroscopy (XPS) and AFM. While TERS and SERS- based detection techniques require the rough metal films that result from dewetting , the silver 4 films

Optimizing Grain Boundary Complexions to Produce Dense Pressure-Less Sintered Boron Carbide (B4C)

Science.gov (United States)

2008-11-14

discontinuous distribution of the yttria. At this stage it is difficult to determine if the discontinuity is genuine or results from dewetting upon cooling...sample. However, the tendency of the film to form beads indicates a dewetting behavior. The weak interface between the yttria and the boron carbide...conform to the dewetting behavior. There is a possibility of a complexion transition as the sample is cooled down in the furnace. At high temperature the

Hybrid Materials for Thermal Management in Thin Films and Bulk Composites

Science.gov (United States)

2012-02-01

dewetting  via  stimuli  responsive  structural  relaxation...acryloylundecyl]-­‐3-­‐methyl-­‐imidazolium  bromide)  –   dewetting  and  nanoparticle  condensation  phenomena;”  X.  Ma,  Md...plastic  was  not   dewetted ,  and  dry  shiny  films  were  obtained   on  all  surfaces  wetted.        

Defective motion processing in children with cerebral visual impairment due to periventricular white matter damage.

Science.gov (United States)

Weinstein, Joel M; Gilmore, Rick O; Shaikh, Sumera M; Kunselman, Allen R; Trescher, William V; Tashima, Lauren M; Boltz, Marianne E; McAuliffe, Matthew B; Cheung, Albert; Fesi, Jeremy D

2012-07-01

We sought to characterize visual motion processing in children with cerebral visual impairment (CVI) due to periventricular white matter damage caused by either hydrocephalus (eight individuals) or periventricular leukomalacia (PVL) associated with prematurity (11 individuals). Using steady-state visually evoked potentials (ssVEP), we measured cortical activity related to motion processing for two distinct types of visual stimuli: 'local' motion patterns thought to activate mainly primary visual cortex (V1), and 'global' or coherent patterns thought to activate higher cortical visual association areas (V3, V5, etc.). We studied three groups of children: (1) 19 children with CVI (mean age 9y 6mo [SD 3y 8mo]; 9 male; 10 female); (2) 40 neurologically and visually normal comparison children (mean age 9y 6mo [SD 3y 1mo]; 18 male; 22 female); and (3) because strabismus and amblyopia are common in children with CVI, a group of 41 children without neurological problems who had visual deficits due to amblyopia and/or strabismus (mean age 7y 8mo [SD 2y 8mo]; 28 male; 13 female). We found that the processing of global as opposed to local motion was preferentially impaired in individuals with CVI, especially for slower target velocities (p=0.028). Motion processing is impaired in children with CVI. ssVEP may provide useful and objective information about the development of higher visual function in children at risk for CVI. © The Authors. Journal compilation © Mac Keith Press 2011.

Single Machine Scheduling and Due Date Assignment with Past-Sequence-Dependent Setup Time and Position-Dependent Processing Time

Directory of Open Access Journals (Sweden)

Chuan-Li Zhao

2014-01-01

Full Text Available This paper considers single machine scheduling and due date assignment with setup time. The setup time is proportional to the length of the already processed jobs; that is, the setup time is past-sequence-dependent (p-s-d. It is assumed that a job's processing time depends on its position in a sequence. The objective functions include total earliness, the weighted number of tardy jobs, and the cost of due date assignment. We analyze these problems with two different due date assignment methods. We first consider the model with job-dependent position effects. For each case, by converting the problem to a series of assignment problems, we proved that the problems can be solved in On4 time. For the model with job-independent position effects, we proved that the problems can be solved in On3 time by providing a dynamic programming algorithm.

Induced Current Characteristics Due to Laser Induced Plasma and Its Application to Laser Processing Monitoring

International Nuclear Information System (INIS)

Madjid, Syahrun Nur; Idris, Nasrullah; Kurniawan, Koo Hendrik; Kagawa, Kiichiro

2011-01-01

In laser processing, suitable conditions for laser and gas play important role in ensuring a high quality of processing. To determine suitable conditions, we employed the electromagnetic phenomena associated with laser plasma generation. An electrode circuit was utilised to detect induced current due to the fast electrons propelled from the material during laser material processing. The characteristics of induced current were examined by changing parameters such as supplied voltage, laser pulse energy, number of laser shots, and type of ambient gas. These characteristics were compared with the optical emission characteristics. It was shown that the induced current technique proposed in this study is much more sensitive than the optical method in monitoring laser processing, that is to determine the precise focusing condition, and to accurately determine the moment of completion of laser beam penetration. In this study it was also shown that the induced current technique induced by CW CO 2 laser can be applied in industrial material processing for monitoring the penetration completion in a stainless steel plate drilling process.

Tube failures due to cooling process problem and foreign materials in power plants

Energy Technology Data Exchange (ETDEWEB)

Ahmad, J. [Kapar Energy Ventures Sdn Bhd, Jalan Tok Muda, Kapar 42200 (Malaysia); Purbolaksono, J., E-mail: judha@uniten.edu.m [Department of Mechanical Engineering, Universiti Tenaga Nasional, Km 7 Jalan Kajang-Puchong, Kajang 43009, Selangor (Malaysia); Beng, L.C. [Kapar Energy Ventures Sdn Bhd, Jalan Tok Muda, Kapar 42200 (Malaysia)

2010-07-15

Cooling process which uses water for heat transfer is an essential factor in coal-fired and nuclear plants. Loss of cooling upset can force the plants to shut down. In particular, this paper reports visual inspections and metallurgical examinations on the failed SA210-A1 right-hand side (RHS) water wall tube of a coal-fired plant. The water wall tube showed the abnormal outer surface colour and has failed with wide-open ductile rupture and thin edges indicating typical signs of short-term overheating. Metallurgical examinations confirmed the failed tube experiencing higher temperature operation. Water flow starvation due to restriction inside the upstream tube is identified as the main root cause of failure. The findings are important to take failure mitigation actions in the future operation. Discussion on the typical problems related to the cooling process in nuclear power plants is also presented.

Tube failures due to cooling process problem and foreign materials in power plants

International Nuclear Information System (INIS)

Ahmad, J.; Purbolaksono, J.; Beng, L.C.

2010-01-01

Cooling process which uses water for heat transfer is an essential factor in coal-fired and nuclear plants. Loss of cooling upset can force the plants to shut down. In particular, this paper reports visual inspections and metallurgical examinations on the failed SA210-A1 right-hand side (RHS) water wall tube of a coal-fired plant. The water wall tube showed the abnormal outer surface colour and has failed with wide-open ductile rupture and thin edges indicating typical signs of short-term overheating. Metallurgical examinations confirmed the failed tube experiencing higher temperature operation. Water flow starvation due to restriction inside the upstream tube is identified as the main root cause of failure. The findings are important to take failure mitigation actions in the future operation. Discussion on the typical problems related to the cooling process in nuclear power plants is also presented.

Investigating the Catalytic Growth of Carbon Nanotubes with In Situ Raman Monitoring

Science.gov (United States)

2015-06-01

thickness and leading to the formation of small particles (less than 5 nm) and (ii) surface dewetting prevailing for thick catalyst layers and leading to...large particles (5–20 nm, see AFM data in Fig. S1) with a higher degree of oxidation (i.e. Co3O4) by surface dewetting . Under weakly-reducing growth... dewetting . These bimodal size and chemi- cal distributions strongly impact the conditions required for activating nanotube growth: weakly-reducing

Size Dependent Mechanical Behavior of Free-Standing Glassy Polymer Thin Films

Science.gov (United States)

2014-08-31

thickness is less than 20 ( ) 1 ( / ) bulk film E EE h hδ = + 14 nm using the liquid dewetting method. Additionally, earlier studies by McKenna’s group and...coated substrates: Rupture, dewetting , and drop formation. J. Colloid Interface Sci. 178(2), 383 (1996). 8. C.B. Roth and J.R. Dutcher: Glass transition...Phys. J. E. 20(2), 143 (2006). 31. J. Wang and G.B. McKenna: Viscoelastic and Glass Transition Properties of Ultrathin Polystyrene Films by Dewetting

Impact of residual by-products from tungsten film deposition on process integration due to nonuniformity of the tungsten film

CERN Document Server

Sidhwa, A; Gandy, T; Melosky, S; Brown, W; Ang, S; Naseem, H; Ulrich, R

2002-01-01

The effects of residual by products from a tungsten film deposition process and their impact on process integration due to the nonuniformity of the tungsten film were investigated in this work. The tungsten film deposition process involves three steps: nucleation, stabilization, and tungsten bulk fill. Six experiments were conducted in search for a solution to the problem. The resulting data suggest that excess nitrogen left in the chamber following the tungsten nucleation step, along with residual by products, causes a shift in the tungsten film uniformity during the tungsten bulk fill process. Data reveal that, due to the residual by products, an abnormal grain growth occurs causing a variation in the tungsten thickness across the wafer during the bulk fill step. Although several possible solutions were revealed by the experiments, potential integration problems limited the acceptable solutions to one. The solution chosen was the introduction of a 10 s pumpdown immediately following the nucleation step. Thi...

Maximum Lateness Scheduling on Two-Person Cooperative Games with Variable Processing Times and Common Due Date

Directory of Open Access Journals (Sweden)

Peng Liu

2017-01-01

Full Text Available A new maximum lateness scheduling model in which both cooperative games and variable processing times exist simultaneously is considered in this paper. The job variable processing time is described by an increasing or a decreasing function dependent on the position of a job in the sequence. Two persons have to cooperate in order to process a set of jobs. Each of them has a single machine and their processing cost is defined as the minimum value of maximum lateness. All jobs have a common due date. The objective is to maximize the multiplication of their rational positive cooperative profits. A division of those jobs should be negotiated to yield a reasonable cooperative profit allocation scheme acceptable to them. We propose the sufficient and necessary conditions for the problems to have positive integer solution.

Fiber Strength of Hi Nicalon(TM) S After Oxidation and Scale Crystallization in Si(OH)4 Saturated Steam (Postprint)

Science.gov (United States)

2017-02-06

transmission electron microscopy. At 700°C and higher, if SiO2 glass scales got too thick they often dewetted the SiC fibers and would spheroidize... SiO2 glass wicked to the spheroids as fast as it formed on the dewetted SiC surface, causing faster oxidation. SiO2 crystallization to cristobalite... glass scales got too thick they often dewetted the SiC fibers and would spheroidize. SiO2 glass wicked to the spheroids as fast as it formed on the

Evaluation of a process for the decontamination of radioactive hotspots due to activated stellite particles

International Nuclear Information System (INIS)

Subramanian, V.; Chandramohan, P.; Srinivasan, M.P.; Rangarajan, S.; Velmurugan, S.; Narasimhan, S.V.; Khandelwal, R.C.

2010-01-01

Some of the Indian PHWRs which used stellite balls in the ball and screw mechanism of the adjustor rod drive mechanism in the moderator circuit encountered high radiation field in moderator system due to 60 Co. Release of particulate stellite was responsible for the hotspots besides the general uniform contamination of internal surfaces with 60 Co. Extensive laboratory studies have shown that it is possible to dissolve these stellite particles by adopting a three step redox process with permanganic acid as the oxidizing agent. These investigations with inactive stellite in powder form helped to optimize the process conditions. Permanganic acid was found to have the highest dissolution efficiency as compared to alkaline and nitric acid permanganate. The concentration of the permanganate was also found to be an important factor in deciding the efficiency of the dissolution of stellite. The efficiency of dissolution as a function of permanganic acid concentration showed a maximum. This process was evaluated for its effectiveness on components from nuclear power plants. Component decontamination was carried out on adjustor rod drive assemblies which had 60 Co activity due to stellite particles with the radiation field ranging from 3 R/h to 20 R/h. They were subjected to decontamination with permanganic acid as oxidizing agent, followed by citric acid and a solution containing EDTA, ascorbic acid and citric acid in 4:3:3 ratio by weight (EAC) as reducing formulations. A test rig was fabricated for this purpose. In the first trial, one adjustor rod drive mechanism was subjected to decontamination. After two cycles of treatment, an average decontamination factor (DF) of 6.8, with a maximum DF of 11.7 was achieved. The same process but one cycle was repeated on eight more adjustor rod drive mechanisms. 60 Co activity in the range of 13 - 93 mCi was removed from these adjustor rods. Loose contamination of the order of 30000 - 40000 dpm/cm 2 observed before decontamination

Thin polymer films on chemically patterned, corrugated substrates

International Nuclear Information System (INIS)

Geoghegan, Mark; Wang Chun; Rehse, Nicolaus; Magerle, Robert; Krausch, Georg

2005-01-01

We study the effect of a chemical pattern on the wetting and dewetting behaviour of thin polystyrene (PS) films on regularly corrugated silicon substrates. Our results reveal that the film preparation, annealing method, and confinement play a critical role in the final film structure. On evaporating gold on both sides of the facets (such that it covered the crests of the facets, and not the troughs), we observed dewetting, which proceeded to the gold, demonstrating an enthalpic effect contrary to the outcome previously observed when gold was only evaporated on one side of the facet. We also coated the substrate with octadecyltrichlorosilane (OTS); this led to a gold and OTS striped structure. PS films several nanometres thick dewet such substrates, with a preferential direction for dewetting in the direction of the stripes forming droplets of a considerably larger size than the stripes

Segmentation and accuracy-based scores for the automatic assessment of oral proficiency for proficient L2 speakers

CSIR Research Space (South Africa)

De Wet, Febe

2010-11-01

Full Text Available stream_source_info DeWet_2011.pdf.txt stream_content_type text/plain stream_size 6 Content-Encoding ISO-8859-1 stream_name DeWet_2011.pdf.txt Content-Type text/plain; charset=ISO-8859-1 ...

Segmentation and accuracy-based scores for the automatic assessment of oral proficiency for proficient L2 speakers

CSIR Research Space (South Africa)

De Wet, Febe

2010-11-01

Full Text Available stream_source_info deWet_2010.pdf.txt stream_content_type text/plain stream_size 109 Content-Encoding ISO-8859-1 stream_name deWet_2010.pdf.txt Content-Type text/plain; charset=ISO-8859-1 /var...

U.S. Case Law and Legal Precedent Affirming the Due Process Rights of Immigrants Fleeing Persecution.

Science.gov (United States)

Sidhu, Shawn S; Boodoo, Ramnarine

2017-09-01

The political discourse on domestic immigration policy has shifted rapidly in recent years, mirrored by similar shifts in the geopolitical climate worldwide. However, a nuanced assessment of the legal basis backing such rhetoric is sorely lacking. This article examines the historical, legal, and case law precedent as it pertains specifically to immigrants who are fleeing persecution and residing within the United States. Due process rights emerged from the Fifth, Sixth, and Fourteenth Constitutional Amendments and have been expanded to include this population through several sequential United States Supreme Court Cases. We review the 1951 Convention Related to the Status of Refugees and 1967 Protocol Relating to the Status of Refugees and examine subsequent case law and legal precedent. We then present evidence documenting widespread violations of due process rights for immigrants fleeing persecution. Specifically, we address the right to a fair hearing for individuals fearing for their lives upon return to their home country, the right against wrongful detainment, and the right to apply for asylum regardless of religion or country of origin. We conclude by addressing potential counterarguments to our thesis, future directions, and the role of forensic psychiatrists. © 2017 American Academy of Psychiatry and the Law.

Evaluation of a process for the decontamination of radioactive hotspots due to activated stellite particles

International Nuclear Information System (INIS)

Subramanian, Veena; Chandramohan, Palogi; Chandran, Sinu; Srinivasan, Madapusi P.; Rangarajan, Srinivasan; Velmurugan, Sankaralingam; Narasimhan, Sevilmedu V.

2011-01-01

Some of the Indian pressurized heavy water reactors (PHWRs) which use Stellite balls in the ball and screw mechanism of the adjustor rod drive mechanism in the moderator circuit have encountered high radiation fields in the moderator system due to 60 Co. Release of particulate Stellite is responsible for the hotspots in addition to the general uniform contamination of internal surfaces with 60 Co. Extensive laboratory studies have shown that it is possible to dissolve these Stellite particles by adopting a three-step redox process with permanganic acid as the oxidizing agent. These investigations with inactive Stellite in powder form helped to optimize the process conditions. Permanganic acid was found to have the highest dissolution efficiency as compared to alkaline and nitric acid permanganate. The susceptibility of Stellite to corrode or dissolve was found to depend on the concentration of the permanganate, pH and temperature of the process and microstructure of the Stellite alloy. This process was evaluated for its effectiveness on components from nuclear power plants. Component decontamination was carried out on adjustor rod drive assemblies which had 60 Co activity due to Stellite particles with the radiation field ranging from 3 R . h -1 to 20 R . h -1 . They were subjected to decontamination with permanganic acid as the oxidizing agent, followed by citric acid and a solution containing ethylenediaminetetraacetic acid, ascorbic acid and citric acid in a 4:3:3 ratio by weight as the reducing formulation. In the first trial, one adjustor rod drive mechanism was subjected to decontamination. After two cycles of treatment, an average decontamination factor (DF) of 6.8, with a maximum DF of 11.7, was achieved. The same process but with one cycle was repeated on eight more adjustor rod drive mechanisms. 60 Co activity in the range of 13-93 mCi was removed from these adjustor rods. Loose contamination of the order of 30 000-40 000 decays per min and cm 2 observed

Evaluation of a process for the decontamination of radioactive hotspots due to activated stellite particles

Energy Technology Data Exchange (ETDEWEB)

Subramanian, Veena; Chandramohan, Palogi; Chandran, Sinu; Srinivasan, Madapusi P.; Rangarajan, Srinivasan; Velmurugan, Sankaralingam; Narasimhan, Sevilmedu V. [BARC Facilities, Kalpakkam, Tamil Nadu (India). Water and Steam Chemistry Div.

2011-06-15

Some of the Indian pressurized heavy water reactors (PHWRs) which use Stellite balls in the ball and screw mechanism of the adjustor rod drive mechanism in the moderator circuit have encountered high radiation fields in the moderator system due to {sup 60}Co. Release of particulate Stellite is responsible for the hotspots in addition to the general uniform contamination of internal surfaces with {sup 60}Co. Extensive laboratory studies have shown that it is possible to dissolve these Stellite particles by adopting a three-step redox process with permanganic acid as the oxidizing agent. These investigations with inactive Stellite in powder form helped to optimize the process conditions. Permanganic acid was found to have the highest dissolution efficiency as compared to alkaline and nitric acid permanganate. The susceptibility of Stellite to corrode or dissolve was found to depend on the concentration of the permanganate, pH and temperature of the process and microstructure of the Stellite alloy. This process was evaluated for its effectiveness on components from nuclear power plants. Component decontamination was carried out on adjustor rod drive assemblies which had {sup 60}Co activity due to Stellite particles with the radiation field ranging from 3 R . h{sup -1} to 20 R . h{sup -1}. They were subjected to decontamination with permanganic acid as the oxidizing agent, followed by citric acid and a solution containing ethylenediaminetetraacetic acid, ascorbic acid and citric acid in a 4:3:3 ratio by weight as the reducing formulation. In the first trial, one adjustor rod drive mechanism was subjected to decontamination. After two cycles of treatment, an average decontamination factor (DF) of 6.8, with a maximum DF of 11.7, was achieved. The same process but with one cycle was repeated on eight more adjustor rod drive mechanisms. {sup 60}Co activity in the range of 13-93 mCi was removed from these adjustor rods. Loose contamination of the order of 30 000-40 000

Evaluation of a process for the decontamination of radioactive hotspots due to activated stellite particles

Energy Technology Data Exchange (ETDEWEB)

Subramanian, V.; Chandramohan, P.; Srinivasan, M.P.; Rangarajan, S.; Velmurugan, S.; Narasimhan, S.V., E-mail: svn@igcar.gov.in [BARC Facilities, Water and Steam Chemistry Div., Kalpakkam, Tamilnadu (India); Khandelwal, R.C. [Kakrapara Atomic Power Station, KAPS, Surat, Gujarat (India)

2010-07-01

Some of the Indian PHWRs which used stellite balls in the ball and screw mechanism of the adjustor rod drive mechanism in the moderator circuit encountered high radiation field in moderator system due to {sup 60}Co. Release of particulate stellite was responsible for the hotspots besides the general uniform contamination of internal surfaces with {sup 60}Co. Extensive laboratory studies have shown that it is possible to dissolve these stellite particles by adopting a three step redox process with permanganic acid as the oxidizing agent. These investigations with inactive stellite in powder form helped to optimize the process conditions. Permanganic acid was found to have the highest dissolution efficiency as compared to alkaline and nitric acid permanganate. The concentration of the permanganate was also found to be an important factor in deciding the efficiency of the dissolution of stellite. The efficiency of dissolution as a function of permanganic acid concentration showed a maximum. This process was evaluated for its effectiveness on components from nuclear power plants. Component decontamination was carried out on adjustor rod drive assemblies which had {sup 60}Co activity due to stellite particles with the radiation field ranging from 3 R/h to 20 R/h. They were subjected to decontamination with permanganic acid as oxidizing agent, followed by citric acid and a solution containing EDTA, ascorbic acid and citric acid in 4:3:3 ratio by weight (EAC) as reducing formulations. A test rig was fabricated for this purpose. In the first trial, one adjustor rod drive mechanism was subjected to decontamination. After two cycles of treatment, an average decontamination factor (DF) of 6.8, with a maximum DF of 11.7 was achieved. The same process but one cycle was repeated on eight more adjustor rod drive mechanisms. {sup 60}Co activity in the range of 13 - 93 mCi was removed from these adjustor rods. Loose contamination of the order of 30000 - 40000 dpm/cm{sup 2} observed

Wetting phenomena in films of molecular hydrogen isotopes

International Nuclear Information System (INIS)

Albrecht, U.; Conradt, R.; Herminghaus, S.; Leiderer, P.

1996-01-01

We have investigated various aspects of the wetting behavior of hydrogen films (including the heavier isotopes) using surface plasmon resonance, light scattering, and photoelectron emission. Studies in the vicinity of the triple point (T 3 (H 2 )=13,96 K) confirmed the known >, and gave no indications for a prewetting transition in this range. At low temperatures (T 3 /3) the equilibrium film thickness reaches only a few monolayers. Thicker films, prepared by quench-condensation of H 2 gas at 1.5 K, undergo a dewetting process during annealing: most of the film material contracts to clusters, and in between the films thins down to its equilibrium thickness. This surface diffusion process is thermally activated, with an activation energy of 23 K (in the case of H 2 ). The dewetting kinetics has not revealed any indication for a surface-molten layer on the solid films at low temperatures, or for a superfluid component

Polymer Surface Textured with Nanowire Bundles to Repel High-Speed Water Drops.

Science.gov (United States)

Li, Y P; Li, X Y; Zhu, X P; Lei, M K; Lakhtakia, A

2018-05-11

Water drops impacting windshields of high-speed trains and aircraft as well as blades in steam turbine power generators obliquely and at high speeds are difficult to repel. Impacting drops penetrate the void regions of nanotextured and microtextured superhydrophobic coatings, with this pinning resulting in the loss of drop mobility. In order to repel high-speed water drops, we nanotextured polymer surfaces with nanowire bundles separated from their neighbors by microscale void regions, with the nanowires in a bundle separated from their neighbors by nanoscale void regions. Water drops with speeds below a critical speed rebound completely. Water drops with speeds exceeding a critical speed rebound partially, but residual droplets that begin to be pinned undergo a spontaneous dewetting process and slide off. The natural oscillations of residual droplets drive this dewetting process in the interbundle void regions, resulting in a transition from the sticky Wenzel state to the slippery Cassie state without external stimuli.

Stochastic level-set variational implicit-solvent approach to solute-solvent interfacial fluctuations

Energy Technology Data Exchange (ETDEWEB)

Zhou, Shenggao, E-mail: sgzhou@suda.edu.cn, E-mail: bli@math.ucsd.edu [Department of Mathematics and Mathematical Center for Interdiscipline Research, Soochow University, 1 Shizi Street, Jiangsu, Suzhou 215006 (China); Sun, Hui; Cheng, Li-Tien [Department of Mathematics, University of California, San Diego, La Jolla, California 92093-0112 (United States); Dzubiella, Joachim [Soft Matter and Functional Materials, Helmholtz-Zentrum Berlin, 14109 Berlin, Germany and Institut für Physik, Humboldt-Universität zu Berlin, 12489 Berlin (Germany); Li, Bo, E-mail: sgzhou@suda.edu.cn, E-mail: bli@math.ucsd.edu [Department of Mathematics and Quantitative Biology Graduate Program, University of California, San Diego, La Jolla, California 92093-0112 (United States); McCammon, J. Andrew [Department of Chemistry and Biochemistry, Department of Pharmacology, Howard Hughes Medical Institute, University of California, San Diego, La Jolla, California 92093-0365 (United States)

2016-08-07

Recent years have seen the initial success of a variational implicit-solvent model (VISM), implemented with a robust level-set method, in capturing efficiently different hydration states and providing quantitatively good estimation of solvation free energies of biomolecules. The level-set minimization of the VISM solvation free-energy functional of all possible solute-solvent interfaces or dielectric boundaries predicts an equilibrium biomolecular conformation that is often close to an initial guess. In this work, we develop a theory in the form of Langevin geometrical flow to incorporate solute-solvent interfacial fluctuations into the VISM. Such fluctuations are crucial to biomolecular conformational changes and binding process. We also develop a stochastic level-set method to numerically implement such a theory. We describe the interfacial fluctuation through the “normal velocity” that is the solute-solvent interfacial force, derive the corresponding stochastic level-set equation in the sense of Stratonovich so that the surface representation is independent of the choice of implicit function, and develop numerical techniques for solving such an equation and processing the numerical data. We apply our computational method to study the dewetting transition in the system of two hydrophobic plates and a hydrophobic cavity of a synthetic host molecule cucurbit[7]uril. Numerical simulations demonstrate that our approach can describe an underlying system jumping out of a local minimum of the free-energy functional and can capture dewetting transitions of hydrophobic systems. In the case of two hydrophobic plates, we find that the wavelength of interfacial fluctuations has a strong influence to the dewetting transition. In addition, we find that the estimated energy barrier of the dewetting transition scales quadratically with the inter-plate distance, agreeing well with existing studies of molecular dynamics simulations. Our work is a first step toward the

Microencapsulation of indocyanine green for potential applications in image-guided drug delivery.

Science.gov (United States)

Zhu, Zhiqiang; Si, Ting; Xu, Ronald X

2015-02-07

We present a novel process to encapsulate indocyanine green (ICG) in liposomal droplets at high concentration for potential applications in image-guided drug delivery. The microencapsulation process follows two consecutive steps of droplet formation by liquid-driven coaxial flow focusing (LDCFF) and solvent removal by oil phase dewetting. These biocompatible lipid vesicles may have important applications in drug delivery and fluorescence imaging.

Poisson’s Ratio Extrapolation from Digital Image Correlation Experiments

Science.gov (United States)

2013-03-01

prior to dewetting ). Also, it is often impractical to measure compressibility. Current rocket laboratory methods measure strains in propellants...distribution unlimited. Public Affairs Clearance Number XXXXX. Damage Characterization of Propellants 16 Dewetting Results 0 2 4 6 8 10 0 5 10 15 20

The Lead Free Electronics Manhattan Project - Phase I

Science.gov (United States)

2009-07-30

and tabs. This standard also includes a test method for the Resistance to Dissolution/ Dewetting of Metallization. This standard is intended for use...Resistance to Dissolution/ Dewetting of Metallization. This standard is intended for use by both vendor and user. Appendix A 261 Baseline Practice Test and

Effect of Annealing Temperature on Morphological and Optical Transition of Silver Nanoparticles on c-Plane Sapphire.

Science.gov (United States)

Pandey, Puran; Kunwar, Sundar; Sui, Mao; Li, Ming-Yu; Zhang, Quanzhen; Lee, Jihoon

2018-05-01

As a promising candidate for the improved performance, silver nanoparticles (Ag NPs) have been successfully adapted in various applications such as photovoltaics, light emitting diodes (LEDs), sensors and catalysis by taking the advantage of their controllable plasmonic properties. In this paper, the control on the morphologies and optical properties of Ag NPs on c-plane sapphire (0001) is demonstrated by the systematic control of annealing temperature (between 200 and 950 °C) with 20 and 6 nm thick Ag films through the solid state dewetting. With the relatively thicker film of 20 nm, various configuration and size of Ag NPs are fabricated such as irregular, round dome-shaped and tiny Ag NPs depending on the annealing temperature. In a shrill contrast, the 6 nm Ag set exhibits a sharp distinction with the formation of densely packed small NPs and ultra-highly dense tiny Ag NPs due to the higher dewetting rate. While, the surface diffusion assumes the main driving force in the evolution process of Ag NP morphologies up to 550 °C, the sublimation of Ag atoms has played a significant role on top on the surface diffusion between 600 and 950 °C. The reflectance spectra of Ag NPs exhibit the quadrupolar resonance and dipolar resonance peaks, and the evolution of peaks, shift and average reflectance were discussed based on the Ag NPs size and surface coverage. In particular, the dipolar resonance peak in the reflectance spectra red shifts from ~475 to ~570 nm due to the size increment of Ag NPs (38.31 to 74.68 nm). The wide surface coverage of Ag NPs exhibits the highest average reflectance (~27%) and the lowest Raman intensity.

Plasmonic Optical Fiber Sensor Based on Double Step Growth of Gold Nano-Islands.

Science.gov (United States)

de Almeida, José M M M; Vasconcelos, Helena; Jorge, Pedro A S; Coelho, Luis

2018-04-20

It is presented the fabrication and characterization of optical fiber sensors for refractive index measurement based on localized surface plasmon resonance (LSPR) with gold nano-islands obtained by single and by repeated thermal dewetting of gold thin films. Thin films of gold deposited on silica (SiO₂) substrates and produced by different experimental conditions were analyzed by Scanning Electron Microscope/Dispersive X-ray Spectroscopy (SEM/EDS) and optical means, allowing identifying and characterizing the formation of nano-islands. The wavelength shift sensitivity to the surrounding refractive index of sensors produced by single and by repeated dewetting is compared. While for the single step dewetting, a wavelength shift sensitivity of ~60 nm/RIU was calculated, for the repeated dewetting, a value of ~186 nm/RIU was obtained, an increase of more than three times. It is expected that through changing the fabrication parameters and using other fiber sensor geometries, higher sensitivities may be achieved, allowing, in addition, for the possibility of tuning the plasmonic frequency.

Plasmonic Optical Fiber Sensor Based on Double Step Growth of Gold Nano-Islands

Science.gov (United States)

Vasconcelos, Helena

2018-01-01

It is presented the fabrication and characterization of optical fiber sensors for refractive index measurement based on localized surface plasmon resonance (LSPR) with gold nano-islands obtained by single and by repeated thermal dewetting of gold thin films. Thin films of gold deposited on silica (SiO2) substrates and produced by different experimental conditions were analyzed by Scanning Electron Microscope/Dispersive X-ray Spectroscopy (SEM/EDS) and optical means, allowing identifying and characterizing the formation of nano-islands. The wavelength shift sensitivity to the surrounding refractive index of sensors produced by single and by repeated dewetting is compared. While for the single step dewetting, a wavelength shift sensitivity of ~60 nm/RIU was calculated, for the repeated dewetting, a value of ~186 nm/RIU was obtained, an increase of more than three times. It is expected that through changing the fabrication parameters and using other fiber sensor geometries, higher sensitivities may be achieved, allowing, in addition, for the possibility of tuning the plasmonic frequency. PMID:29677108

Polymer Thin Film Stabilization.

Science.gov (United States)

Costa, A. C.; Oslanec, R.; Composto, R. J.; Vlcek, P.

1998-03-01

We study the dewetting dynamics of thin polystyrene (PS) films deposited on silicon oxide surfaces using optical (OM) and atomic force (AFM) microscopes. Quantitative analysis of the hole diameter as a function of annealing time at 175^oC shows that blending poly(styrene-block-methyl-methacrylate) (PS-b-PMMA) with PS acts to dramatically slow down the dewetting rate and even stops holes growth before they impinge. AFM studies show that the hole floor is smooth for a pure PS film but contains residual polymer for the blend. At 5% vol., a PS-b-PMMA with high molar mass and low PMMA is a more effective stabilizing agent than a low molar mass/high PMMA additive. The optimum copolymer concentration is 3% vol. beyond which film stability doesn't improve. Although dewetting is slowed down relative to pure PS, PS/PS-b-PMMA bilayers dewet at a faster rate than blends having the same overall additive concentration.

Stability of Polymer Ultrathin Films (Top-Down Approach.

Science.gov (United States)

Bal, Jayanta Kumar; Beuvier, Thomas; Unni, Aparna Beena; Chavez Panduro, Elvia Anabela; Vignaud, Guillaume; Delorme, Nicolas; Chebil, Mohamed Souheib; Grohens, Yves; Gibaud, Alain

2015-08-25

In polymer physics, the dewetting of spin-coated polystyrene ultrathin films on silicon remains mysterious. By adopting a simple top-down method based on good solvent rinsing, we are able to prepare flat polystyrene films with a controlled thickness ranging from 1.3 to 7.0 nm. Their stability was scrutinized after a classical annealing procedure above the glass transition temperature. Films were found to be stable on oxide-free silicon irrespective of film thickness, while they were unstable (2.9 nm) on 2 nm oxide-covered silicon substrates. The Lifshitz-van der Waals intermolecular theory that predicts the domains of stability as a function of the film thickness and of the substrate nature is now fully reconciled with our experimental observations. We surmise that this reconciliation is due to the good solvent rinsing procedure that removes the residual stress and/or the density variation of the polystyrene films inhibiting thermodynamically the dewetting on oxide-free silicon.

Average thermal stress in the Al+SiC composite due to its manufacturing process

International Nuclear Information System (INIS)

Miranda, Carlos A.J.; Libardi, Rosani M.P.; Marcelino, Sergio; Boari, Zoroastro M.

2013-01-01

The numerical analyses framework to obtain the average thermal stress in the Al+SiC Composite due to its manufacturing process is presented along with the obtained results. The mixing of Aluminum and SiC powders is done at elevated temperature and the usage is at room temperature. A thermal stress state arises in the composite due to the different thermal expansion coefficients of the materials. Due to the particles size and randomness in the SiC distribution, some sets of models were analyzed and a statistical procedure used to evaluate the average stress state in the composite. In each model the particles position, form and size are randomly generated considering a volumetric ratio (VR) between 20% and 25%, close to an actual composite. The obtained stress field is represented by a certain number of iso stress curves, each one weighted by the area it represents. Systematically it was investigated the influence of: (a) the material behavior: linear x non-linear; (b) the carbide particles form: circular x quadrilateral; (c) the number of iso stress curves considered in each analysis; and (e) the model size (the number of particles). Each of above analyzed condition produced conclusions to guide the next step. Considering a confidence level of 95%, the average thermal stress value in the studied composite (20% ≤ VR ≤ 25%) is 175 MPa with a standard deviation of 10 MPa. Depending on its usage, this value should be taken into account when evaluating the material strength. (author)

Thermo-Rheometric Studies of New Class Ionic Liquid Lubricants

Science.gov (United States)

Bakhtiyarov, Sayavur; Street, Kenneth; Scheiman, Daniel; van Dyke, Alan

2010-11-01

Due to their specific properties, such as small volatility, nonflammability, extreme thermal stability, low melting point, wide liquid range, and good miscibility with organic materials, ionic liquids attracted particular interest in various industrial processes. Recently, the unique properties of ionic liquids caught the attention of space tribologists. The traditional lubricating materials used in space have limited lifetimes in vacuum due to the catalytic degradation on metal surfaces, high vaporization at high temperatures, dewetting, and other disadvantages. The lubricants for the space applications must have vacuum stability, high viscosity index, low creep tendency, good elastohydrodynamic and boundary lubrication properties, radiation atomic oxygen resistance, optical or infrared transparency. Unfortunately, the properties such as heat flow, heat capacity, thermogravimetric weight loss, and non-linearity in the rheological behavior of the lubricants are not studied well for newly developed systems. These properties are crucial to analyzing thermodynamic and energy dissipative aspects of the lubrication process. In this paper we will present the rheological and heat and mass transfer measurements for the ionic liquid lubricants, their mixtures with and without additive.

Frequency of deflagration in the in-tank precipitation process tanks due to loss of nitrogen purge system

International Nuclear Information System (INIS)

Jansen, J.M.; Mason, C.L.; Olsen, L.M.; Shapiro, B.J.; Gupta, M.K.; Britt, T.E.

1994-01-01

High-level liquid wastes (HLLW) from the processing of nuclear material at the Savannah River Site (SRS) are stored in large tanks in the F- and H-Area tank farms. The In-Tank Precipitation (ITP) process is one step in the processing and disposal of HLLW. The process hazards review for the ITP identified the need to implement provisions that minimize deflagration/explosion hazards associated with the process. The objective of this analysis is to determine the frequency of a deflagration in Tank 48 and/or 49 due to nitrogen purge system failures (including external events) and coincident ignition source. A fault tree of the nitrogen purge system coupled with ignition source probability is used to identify dominant system failures that contribute to the frequency of deflagration. These system failures are then used in the recovery analysis. Several human actions, recovery actions, and repair activities are identified that reduce total frequency. The actions are analyzed and quantified as part of a Human Reliability Analysis (HRA). The probabilities of failure of these actions are applied to the fault tree cutsets and the event trees

Poly(styrene-co-butadiene) random copolymer thin films and nanostructures on a mica surface: morphology and contact angles of nanodroplets.

Science.gov (United States)

McClements, Jake; Buffone, Cosimo; Shaver, Michael P; Sefiane, Khellil; Koutsos, Vasileios

2017-09-20

The self-assembly of poly(styrene-co-butadiene) random copolymers on mica surfaces was studied by varying solution concentrations and polymer molecular weights. Toluene solutions of the poly(styrene-co-butadiene) samples were spin coated onto a mica surface and the resulting polymer morphology was investigated by atomic force microscopy. At higher concentrations, thin films formed with varying thicknesses; some dewetting was observed which depended on the molecular weight. Total dewetting did not occur despite the polymer's low glass transition temperature. Instead, partial dewetting was observed suggesting that the polymer was in a metastable equilibrium state. At lower concentrations, spherical cap shaped nanodroplets formed with varying sizes from single polymer chains to aggregates containing millions of chains. As the molecular weight was increased, fewer aggregates were observed on the surface, albeit with larger sizes resulting from increased solution viscosities and more chain entanglements at higher molecular weights. The contact angles of the nanodroplets were shown to be size dependent. A minimum contact angle occurs for droplets with radii of 100-250 nm at each molecular weight. Droplets smaller than 100 nm showed a sharp increase in contact angle; attributed to an increase in the elastic modulus of the droplets, in addition, to a positive line tension value. Droplets larger than 250 nm also showed an increased contact angle due to surface heterogeneities which cannot be avoided for larger droplets. This increase in contact angle plateaus as the droplet size reaches the macroscopic scale.

South African, Rural ICT Implementation: a critical retrospective application of Latour's due process model

Directory of Open Access Journals (Sweden)

Jo Rhodes

2004-05-01

Full Text Available The potential developmental role of ICTs can pressurise governments to engage in ‘catch up’ and ‘leapfrog’. Consequently, analysis of the accompanying socio-political dimensions and risks can be, disastrously, neglected. This paper examines a specific technology implementation – a South African government sponsored telecentre using Latour’s Due Process model, an analytical tool grounded in Actor-Network Theory, where technology implementation is viewed as a symmetrical treatment of technology and society within a single collective. It is used here, retrospectively, to make sense of why the telecentre both failed to institutionalise within a successful actor-network, and, contributed to the destabilization and partial destruction of a successfully established women’s development organisation.

Temperature resolution enhancing of commercially available THz passive cameras due to computer processing of images

Science.gov (United States)

Trofimov, Vyacheslav A.; Trofimov, Vladislav V.; Kuchik, Igor E.

2014-06-01

As it is well-known, application of the passive THz camera for the security problems is very promising way. It allows seeing concealed object without contact with a person and this camera is non-dangerous for a person. Efficiency of using the passive THz camera depends on its temperature resolution. This characteristic specifies possibilities of the detection of concealed object: minimal size of the object, maximal distance of the detection, image detail. One of probable ways for a quality image enhancing consists in computer processing of image. Using computer processing of the THz image of objects concealed on the human body, one may improve it many times. Consequently, the instrumental resolution of such device may be increased without any additional engineering efforts. We demonstrate new possibilities for seeing the clothes details, which raw images, produced by the THz cameras, do not allow to see. We achieve good quality of the image due to applying various spatial filters with the aim to demonstrate independence of processed images on math operations. This result demonstrates a feasibility of objects seeing. We consider images produced by THz passive cameras manufactured by Microsemi Corp., and ThruVision Corp., and Capital Normal University (Beijing, China).

High Performance Organic Semiconductors

Science.gov (United States)

2012-07-31

induce dewetting of the solutions (Fig. 7A, black region). The obtained crystals are well-aligned and separated with distinct areas of C60 and TIPS...ozone and becomes solvent- dewetting . As the solvent evaporates slowly, the crystals of C60 and TIPS-pentacene nucleate near the contact lines of the

The Analysis and Modeling of Phase Stability and Multiphase Designs in High Temperature Refractory Metal-Silicon-Boron Alloys

Science.gov (United States)

2009-01-27

1) dewetting method and (2) exponential growth LBL; (3) spin-assisted LBL; and (4) Large scale LBL deposition (Figure 1). 5. Method of...Agarwal A., Tang Z., Ho S., Ingle P.’ Patterson D., Lu W., Kotov N. A., Nanostructured Thin Films made by Dewetting Method Of Layer-By-Layer Assembly

Self-organised nano-structuring of thin oxide-films under swift heavy ion bombardment

International Nuclear Information System (INIS)

Bolse, Wolfgang

2006-01-01

Surface instabilities and the resulting self-organisation processes play an important role in nano-technology since they allow for large-array nano-structuring. We have recently found that the occurrence of such instabilities in thin film systems can be triggered by energetic ion bombardment and the subsequent self-assembly of the surface can be nicely controlled by fine-tuning of the irradiation conditions. The role of the ion in such processes is of double nature: If the instability is latently present already in the virgin sample, but self-assembly cannot take place because of kinetic barriers, the ion impact may just supply the necessary atomic mobility. On the other hand, the surface may become instable due to the ion beam induced material modifications and further irradiation then results in its reorganisation. In the present paper, we will review recently observed nano-scale self-organisation processes in thin oxide-films induced by the irradiation with swift heavy ions (SHI) at some MeV/amu energies. The first example is about SHI induced dewetting, which is driven by capillary forces already present in the as-deposited samples. The achieved dewetting pattern show an amazing similarity to those observed for liquid polymer films on Si, although in the present case the samples were kept at 80 K and hence have never reached their melting point. The second example is about self-organised lamellae formation driven by planar stresses, which are induced by SHI bombardment under grazing incidence and result in a surface instability and anisotropic plastic deformation (hammering effect). Taking advantage of these effects and modifying the irradiation procedure, we were able to generate more complex structures like NiO-'nano-towers' of 2 μm height and 200 nm in diameter

Study of thermal degradation of organic light emitting device structures by X-ray scattering

International Nuclear Information System (INIS)

Lee, Young-Joo; Lee, Heeju; Byun, Youngsuk; Song, Sanghoon; Kim, Je-Eun; Eom, Daeyong; Cha, Wonsuk; Park, Seong-Sik; Kim, Jinwoo; Kim, Hyunjung

2007-01-01

We report the process of thermal degradation of organic light emitting devices (OLEDs) having multilayered structure of [LiF/tris-(8-hydroxyquinoline) aluminum(Alq 3 )/N,N'-Bis(naphthalen-1-yl)-N,N'-bis(phenyl)benzidine (NPB)/copper phthalocyanine (CuPc)/indium tin oxide (ITO)/SiO 2 on a glass] by synchrotron X-ray scattering. The results show that the thermally induced degradation process of OLED multilayers has undergone several evolutions due to thermal expansion of NPB, intermixing between NPB, Alq 3 , and LiF layers, dewetting of NPB on CuPc, and crystallization of NPB and Alq 3 depending on the annealing temperature. The crystallization of NPB appears at 180 deg. C, much higher temperature than the glass transition temperature (T g = 96 deg. C) of NPB. The results are also compared with the findings from the atomic force microscope (AFM) images

Plasmonic Optical Fiber Sensor Based on Double Step Growth of Gold Nano-Islands

Directory of Open Access Journals (Sweden)

José M. M. M. de Almeida

2018-04-01

Full Text Available It is presented the fabrication and characterization of optical fiber sensors for refractive index measurement based on localized surface plasmon resonance (LSPR with gold nano-islands obtained by single and by repeated thermal dewetting of gold thin films. Thin films of gold deposited on silica (SiO2 substrates and produced by different experimental conditions were analyzed by Scanning Electron Microscope/Dispersive X-ray Spectroscopy (SEM/EDS and optical means, allowing identifying and characterizing the formation of nano-islands. The wavelength shift sensitivity to the surrounding refractive index of sensors produced by single and by repeated dewetting is compared. While for the single step dewetting, a wavelength shift sensitivity of ~60 nm/RIU was calculated, for the repeated dewetting, a value of ~186 nm/RIU was obtained, an increase of more than three times. It is expected that through changing the fabrication parameters and using other fiber sensor geometries, higher sensitivities may be achieved, allowing, in addition, for the possibility of tuning the plasmonic frequency.

Home-Schools and Interscholastic Sports: Denying Participation Violates United States Constitutional Due Process and Equal Protection Rights. Chalk Talk.

Science.gov (United States)

Webb, Derwin L.

1997-01-01

Participation in sports, in some instances, is considered a right which grants students the opportunity to be involved in extracurricular activities. Discusses the potential violation of home-schooled students' constitutional due process and equal protection rights and the pertinent laws regarding students and their ability to participate in…

Elevated temperature transmission Kikuchi diffraction in the SEM

DEFF Research Database (Denmark)

Fanta, Alice Bastos; Todeschini, Matteo; Burrows, Andrew

2018-01-01

heating associated with this system enables reliable TKD measurements at elevated temperatures without notable disturbance from infrared radiation. The dewetting of an Au thin film into Au nanoparticles upon heating is followed with orientation mapping in a temperature range between 20 °C and 900 °C....... The local thickness variation associated with the dewetting is observed qualitatively by observing the intensity of the transmitted beam, which decreases as the film thickness increases locally. The results of this study reveal that TKD is a well suited technique to study thin-film stability and solid state...... dewetting. Moreover, the outcome of this methodological study provides a baseline for further in-situ crystallographic studies of electron transparent samples in the SEM....

Laser-induced short- and long-range orderings of Co nanoparticles on SiO2

International Nuclear Information System (INIS)

Favazza, C.; Trice, J.; Krishna, H.; Kalyanaraman, R.; Sureshkumar, R.

2006-01-01

Laser irradiation of ultrathin Co films leads to pattern formation by dewetting with short-range order (SRO) as well as long-range order (LRO). When a 1.5 nm thick Co film is irradiated by a single laser beam, a monomodal size distribution of particles with average diameter of 31±10 nm and nearest-neighbor spacing of 75 nm is observed. Moreover, melting by two-beam interference irradiation produces LRO as well as SRO giving a quasi-two-dimensional arrangement of nanoparticles. The SRO is attributed to spinodal dewetting while the LRO is conjectured to be induced by in-plane interfacial tension gradients. Laser-induced dewetting of metals could be a simple technique to fabricate ordered metal nanoarrays

Effect of Systematic Control of Pd Thickness and Annealing Temperature on the Fabrication and Evolution of Palladium Nanostructures on Si (111) via the Solid State Dewetting.

Science.gov (United States)

Kunwar, Sundar; Pandey, Puran; Sui, Mao; Zhang, Quanzhen; Li, Ming-Yu; Lee, Jihoon

2017-12-01

Si-based optoelectronic devices embedded with metallic nanoparticles (NPs) have demonstrated the NP shape, size, spacing, and crystallinity dependent on light absorption and emission induced by the localized surface plasmon resonance. In this work, we demonstrate various sizes and configurations of palladium (Pd) nanostructures on Si (111) by the systematic thermal annealing with the variation of Pd thickness and annealing temperature. The evolution of Pd nanostructures are systematically controlled by the dewetting of thin film by means of the surface diffusion in conjunction with the surface and interface energy minimization and Volmer-Weber growth model. Depending on the control of deposition amount ranging between 0.5 and 100 nm at various annealing temperatures, four distinctive regimes of Pd nanostructures are demonstrated: (i) small pits and grain formation, (ii) nucleation and growth of NPs, (iii) lateral evolution of NPs, and (iv) merged nanostructures. In addition, by the control of annealing between 300 and 800 °C, the Pd nanostructures show the evolution of small pits and grains, isolated NPs, and finally, Pd NP-assisted nanohole formation along with the Si decomposition and Pd-Si inter-diffusion. The Raman analysis showed the discrepancies on phonon modes of Si (111) such that the decreased peak intensity with left shift after the fabrication of Pd nanostructures. Furthermore, the UV-VIS-NIR reflectance spectra revealed the existence of surface morphology dependent on absorption, scattering, and reflectance properties.

Transport in nanoparticle chains influenced by reordering

International Nuclear Information System (INIS)

Luedtke, T.; Mirovsky, P.; Huether, R.; Govor, L.; Bauer, G.H.; Parisi, J.; Haug, R.J.

2011-01-01

Nanoparticles are deposited onto a mica substrate in a dewetting process of hexane solution containing the nanoparticles. The array of nanoparticles was measured inside an electron beam microscope containing a self-developed probing-tip setup. Transport measurements performed under vacuum conditions at room temperature show a power law behavior as expected for low-dimensional cluster systems. During the measurement a variation of the threshold voltage in the nonlinear current-voltage (I-V) characteristic was observed which we attribute to a reordering of the system by an applied electric field. - Highlights: → Fabrication of chains of ordered Au-nanoparticles. → Contact these nanoparticles without further chemical treatment with probing tips inside an electron microscope. → Observation of low-dimensional transport and Coulomb blockade. → Reordering of nanoparticles due to the applied electric field between the tips.

Heterogeneity of glucagonomas due to differential processing of proglucagon-derived peptides

DEFF Research Database (Denmark)

Challis, Benjamin G; Albrechtsen, Nicolai J Wewer; Bansiya, Vishakha

2015-01-01

activities including critical roles in glucose and amino acid metabolism, energy homeostasis and gastrointestinal physiology.The clinical manifestations of proglucagon-expressing tumours may exhibit marked phenotypic variation due to the biochemical heterogeneity of their secreted peptide repertoire...... the rash. Case 2, a 48-year-old male presented with diabetes mellitus, diarrhoea, weight loss, nausea, vomiting and perineal rash due to a grade 1 metastatic pNET and hyperglucagonaemia. In both cases, plasma levels of all measured PGDPs were elevated and attenuated following SSA therapy. In case 1...

Analysis of the Processes in Spent Fuel Pools in Case of Loss of Heat Removal due to Water Leakage

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Algirdas Kaliatka

2013-01-01

Full Text Available The safe storage of spent fuel assemblies in the spent fuel pools is very important. These facilities are not covered by leaktight containment; thus, the consequences of overheating and melting of fuel in the spent fuel pools can be very severe. On the other hand, due to low decay heat of fuel assemblies, the processes in pools are slow in comparison with processes in reactor core during LOCA accident. Thus, the accident management measures play a very important role in case of some accidents in spent fuel pools. This paper presents the analysis of possible consequences of fuel overheating due to leakage of water from spent fuel pool. Also, the accident mitigation measure, the late injection of water was evaluated. The analysis was performed for the Ignalina NPP Unit 2 spent fuel pool, using system thermal hydraulic code for severe accident analysis ATHLET-CD. The phenomena, taking place during such accident, are discussed. Also, benchmarking of results of the same accident calculation using ASTEC and RELAP/SCDAPSIM codes is presented here.

Evolution of Ternary AuAgPd Nanoparticles by the Control of Temperature, Thickness, and Tri-Layer

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Sundar Kunwar

2017-11-01

Full Text Available Metallic alloy nanoparticles (NPs possess great potential to enhance the optical, electronic, chemical, and magnetic properties for various applications by the control of morphology and elemental composition. This work presents the fabrication of ternary AuAgPd alloy nanostructures on sapphire (0001 via the solid-state dewetting of sputter-deposited tri-metallic layers. Based on the systematic control of temperature, thickness, and deposition order of tri-layers, the composite AuAgPd alloy nanoparticles (NPs with various shape, size, and density are demonstrated. The metallic tri-layers exhibit various stages of dewetting based on the increasing growth temperatures between 400 and 900 °C at 15 nm tri-layer film thickness. Specifically, the nucleation of tiny voids and hillocks, void coalescence, the growth and isolated nanoparticle formation, and the shape transformation with Ag sublimation are observed. With the reduced film thickness (6 nm, tiny alloy NPs with improved structural uniformity and spatial arrangement are obtained due to enhanced dewetting. The growth trend of alloy NPs is drastically altered by changing the deposition order of metallic tri-layers. The overall evolution is governed by the surface diffusion and inter-mixing of metallic atoms, Rayleigh-like instability, surface and interface energy minimization, and equilibrium state of the system. The UV-VIS-NIR reflectance spectra reveal the formation of an absorption band and reflectance maxima at specific wavelengths based on the morphology and composition of AuAgPd alloy NPs. In addition, Raman spectra analysis shows the modulation of intensity and peak position of natural vibration modes of sapphire (0001.

Effects due to spectator interaction in deep inelastic processes

International Nuclear Information System (INIS)

Smilga, A.V.

1979-01-01

The simplest diagrams describing interaction with the spectator in the e - π→e - + hadrons deep inelastic process are considered. The contribution of the final state interaction diagram to the structure function considerable in the Feynman gauge is suppressed under the temporal gauge choice in accordance with the results of the naive parton model. The expressin for the cross section of the process when large quark momentum is transferred to the spectator is derived

Enhancing Title Ix Due Process Standards in Campus Sexual Assault Adjudication: Considering the Roles of Distributive, Procedural, and Restorative Justice

Science.gov (United States)

Harper, Shannon; Maskaly, Jon; Kirkner, Anne; Lorenz, Katherine

2017-01-01

Title IX prohibits sex discrimination--including sexual assault--in higher education. The Department of Education Office for Civil Rights' 2011 "Dear Colleague Letter" outlines recommendations for campus sexual assault adjudication allowing a variety of procedures that fail to protect accused students' due process rights and victims'…

Anomalous diffusion due to hindering by mobile obstacles undergoing Brownian motion or Orstein-Ulhenbeck processes.

Science.gov (United States)

Berry, Hugues; Chaté, Hugues

2014-02-01

In vivo measurements of the passive movements of biomolecules or vesicles in cells consistently report "anomalous diffusion," where mean-squared displacements scale as a power law of time with exponent αmovement hindrance by obstacles is often invoked. However, our understanding of how hindered diffusion leads to subdiffusion is based on diffusion amidst randomly located immobile obstacles. Here, we have used Monte Carlo simulations to investigate transient subdiffusion due to mobile obstacles with various modes of mobility. Our simulations confirm that the anomalous regimes rapidly disappear when the obstacles move by Brownian motion. By contrast, mobile obstacles with more confined displacements, e.g., Orstein-Ulhenbeck motion, are shown to preserve subdiffusive regimes. The mean-squared displacement of tracked protein displays convincing power laws with anomalous exponent α that varies with the density of Orstein-Ulhenbeck (OU) obstacles or the relaxation time scale of the OU process. In particular, some of the values we observed are significantly below the universal value predicted for immobile obstacles in two dimensions. Therefore, our results show that subdiffusion due to mobile obstacles with OU type of motion may account for the large variation range exhibited by experimental measurements in living cells and may explain that some experimental estimates are below the universal value predicted for immobile obstacles.

Synthesis of Au nanoparticles at the surface and embedded in carbonaceous matrix by 150 keV Ar ion irradiation

International Nuclear Information System (INIS)

Prakash, Jai; Tripathi, Jalaj; Tripathi, A; Kumar, P; Asokan, K; Avasthi, D K; Rigato, V; Pivin, J C; Chae, Keun Hwa; Gautam, Sanjeev

2011-01-01

We report on synthesis of spherical Au nanoparticles at the surface and embedded in carbonaceous matrix by 150 keV Ar ion irradiation of thin Au film on polyethyleneterepthlate (PET). The pristine and irradiated samples are characterized by Rutherford backscattering spectrometry (RBS), atomic force microscopy, scanning electron microscopy and transmission electron microscopy (TEM) techniques. RBS spectra reveal the sputtering of Au film and interface mixing, increasing with increasing fluence. Surface morphology shows that at the fluence of 5 x 10 15 ions cm -2 , dewetting of thin Au film begins and partially connected nanostructures are formed whereas, at the higher fluence of 5 x 10 16 ions cm -2 , isolated spherical Au nanoparticles (45 ± 20 nm) are formed at the surface. Cross-sectional TEM observations also evidence the Au nanoparticles at the surface and mixed metal-polymer region indicating the formation of nanocomposites with small Au nanoparticles. The results are explained by the crater formation, sputtering followed by dewetting of the thin Au film and interdiffusion at the interface, through molten zones due to thermal spike induced by Ar ions.

In-situ observation of equilibrium transitions in Ni films; agglomeration and impurity effects.

Science.gov (United States)

Thron, Andrew M; Greene, Peter; Liu, Kai; van Benthem, Klaus

2014-02-01

Dewetting of ultra-thin Ni films deposited on SiO2 layers was observed, in cross-section, by in situ scanning transmission electron microscopy. Holes were observed to nucleate by voids which formed at the Ni/SiO2 interface rather than at triple junctions at the free surface of the Ni film. Ni islands were observed to retract, in attempt to reach equilibrium on the SiO2 layer. SiO2 layers with 120 nm thickness were found to limit in situ heating experiments due to poor thermal conductivity of SiO2. The formation of graphite was observed during the agglomeration of ultra-thin Ni films. Graphite was observed to wet both the free surface and the Ni/SiO2 interface of the Ni islands. Cr forms surface oxide layers on the free surface of the SiO2 layer and the Ni islands. Cr does not prevent the dewetting of Ni, however it will likely alter the equilibrium shape of the Ni islands. © 2013 Published by Elsevier B.V.

Eyewitness Identification Reform: Data, Theory, and Due Process.

Science.gov (United States)

Clark, Steven E

2012-05-01

Some commentators view my analyses (Clark, 2012, this issue) as an important step forward in assessing the costs and benefits of eyewitness identification reform. Others suggest that the trade-off between correct identifications lost and false identifications avoided is well-known; that the expected utility model is misspecified; and that the loss of correct identifications due to the use of reformed eyewitness identification procedures is irrelevant to policy decisions, as those correct identifications are the illegitimate product of suggestion and lucky guesses. Contrary to these criticisms, the loss of correct identifications has not been adequately considered in theoretical or policy matters, criticisms regarding the various utilities do not substantively change the nature of the trade-off, and the dismissal of lost correct identifications is based not on data but on an outdated theory of recognition memory. © The Author(s) 2012.

Qubit dephasing due to quasiparticle tunneling

Energy Technology Data Exchange (ETDEWEB)

Zanker, Sebastian; Marthaler, Michael; Schoen, Gerd [Institut fuer Theoretische Festkoerperphysik, Karlsruhe Institute of Technology, D-76128 Karlsruhe (Germany)

2015-07-01

We study dephasing of a superconducting qubit due to quasiparticle tunneling through a Josephson junction. While qubit decay due to tunneling processes is well understood within a golden rule approximation, pure dephasing due to BCS quasiparticles gives rise to a divergent golden rule rate. We calculate qubit dephasing due to quasiparticle tunneling beyond lowest order approximation in coupling between qubit and quasiparticles. Summing up a certain class of diagrams we show that qubit dephasing due to purely longitudinal coupling to quasiparticles leads to dephasing ∝ exp(-x(t)) where x(t) ∝ t{sup 3/2} for short time scales and x(t) ∝ tlog(t) for long time scales.

Accommodaton of constitutional due process rights within the new patients' rights legislation in Slovenia.

Science.gov (United States)

Ivanc, Blaz

2011-09-01

The Constitutional Court of the Republic of Slovenia issued several decisions concerning the protection of patients' rights (e.g. decisions on involuntary commitment, on access to health care, on rights related to obligatory and voluntary health insurance). Consequently, the Parliament renewed Health Legislation by the enactment of the Patients' Rights Act (February 2008) and of the Mental Health Act (July 2008). Both bills enshrine a charter of patients' rights that may be considered as concretization of several human rights that are protected by the Constitution. The discussion is focused on the due process rights (e.g. equal protection of rights, right to judicial protection, right to legal remedies, legal guarantees in proceedings related to deprivation of personal liberty) that were in particular addressed by the Court. The results demonstrate that their effective implementation was one of the most important demands that the Legislature had to accommodate when enacting new bills.

Adaptive memory: the survival-processing memory advantage is not due to negativity or mortality salience.

Science.gov (United States)

Bell, Raoul; Röer, Jan P; Buchner, Axel

2013-05-01

Recent research has highlighted the adaptive function of memory by showing that imagining being stranded in the grasslands without any survival material and rating words according to their survival value in this situation leads to exceptionally good memory for these words. Studies examining the role of emotions in causing the survival-processing memory advantage have been inconclusive, but some studies have suggested that the effect might be due to negativity or mortality salience. In Experiments 1 and 2, we compared the survival scenario to a control scenario that implied imagining a hopeless situation (floating in outer space with dwindling oxygen supplies) in which only suicide can avoid the agony of choking to death. Although this scenario was perceived as being more negative than the survival scenario, the survival-processing memory advantage persisted. In Experiment 3, thinking about the relevance of words for survival led to better memory for these words than did thinking about the relevance of words for death. This survival advantage was found for concrete, but not for abstract, words. The latter finding is consistent with the assumption that the survival instructions encourage participants to think about many different potential uses of items to aid survival, which may be a particularly efficient form of elaborate encoding. Together, the results suggest that thinking about death is much less effective in promoting recall than is thinking about survival. Therefore, the survival-processing memory advantage cannot be satisfactorily explained by negativity or mortality salience.

Meghan Rene, et al., v. Dr. Suellen Reed, et al. "Due Process." Lesson Plans for Secondary School Teachers on the Constitutional Requirement of "Due Process of Law." Courts in the Classroom: Curriculum Concepts and Other Information on Indiana's Courts for the K-12 Educator.

Science.gov (United States)

Osborn, Elizabeth

In the Rene v. Reed case, Meghan Rene and other disabled students argued that their due process rights were violated in regard to the Indiana Statewide Testing for Educational Progress (ISTEP) graduation examination. This set of four lesson plans uses the case of Rene v. Reed, which was first argued before the Indiana Supreme Court, to study the…

Final report for grant: DE-FG02-93ER45481 [Polymers at engineered interfaces

International Nuclear Information System (INIS)

Rafailovich, Miriam; Sokolov, Jonathan

2000-01-01

Studies have been made of polymer interfaces, self-assembly of micelles at surfaces, phase separation in blends, diffusion and dewetting at and near interfaces, and nanomechanical properties of thin films. The main projects are summarized under the following topics: dislocations in lamellar diblock structures, effects of surface tension; compliance measurements and profiles of end-grafted polystyrene in solution observed by atomic force microscopy and neutron reflectivity; self-assembly of diblock polymer micelles from solution; dewetting dynamics; polymers on patterned surfaces; Flory-Huggins interaction parameter for polystyrene/poly-2-vinylpyridine (PS/P 4 VP) blends; phase separation-induced patterns in dPS/PVME and dPEP/PEP blends; and high-resolution lateral imaging studies of phase separation and dewetting by scanning transmission X-ray microscopy (STXM) and photoemission electron microscopy (PEEM)

Study of test-mass charging process in the LISA missions due to diffuse γ-rays

International Nuclear Information System (INIS)

Finetti, N; Scrimaglio, R; Grimani, C; Fabi, M

2009-01-01

Gravitational inertial sensors will be placed on board the Laser Interferometer Space Antenna (LISA) and aboard its precursor mission LISA Pathfinder (LISA-PF) in order to detect low frequency gravitational waves in space. Free-floating test-masses (Au 7 Pt 3 cubes) will be housed in inertial sensors for detecting possible laser signal variations induced by gravitational waves. Charging of the LISA test-masses due to exposure of the spacecraft to cosmic radiation and energetic solar particles will affect operation of gravitational inertial sensors. In this paper we report on the role of diffuse γ-rays in charging the LISA and LISA-PF test-masses with respect to protons and helium nuclei. The diffuse γ-ray flux in the Galaxy has been interpolated taking into account the outcomes of recent calculations. A comparison with γ-ray observations gathered by different experiments (COMPTEL and EGRET, Milagro, Whipple, HEGRA, TIBET) has been carried out. Simulations of the test-mass charging process have been performed by means of the FLUKA2006.3b package. Monte Carlo simulations of the interaction of cosmic particles with the LISA spacecraft indicate that the diffuse γ-ray contribution to the average steady-state test-mass charging rate and to the single-sided power spectrum of the charge rate noise is marginal with respect to that due to galactic cosmic-rays.

T-Shaped Indan-1,3-dione derivatives as promising electron donors for bulk heterojunction small molecule solar cell

Science.gov (United States)

Adhikari, Tham; Solanke, Parmeshwar; Pathak, Dinesh; Wagner, Tomas; Bureš, Filip; Reed, Tyler; Nunzi, Jean-Michel

2017-07-01

We report on the photovoltaic performance of novel T-Shaped Indan-1,3-dione derivatives as donors in a solution processed bulk heterojunction solar cells. Small molecule bulk heterojunction solar cells of these molecules with [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) were fabricated and characterized. The preliminary characterization of these devices yielded a PCE of 0.24% and 0.33% for two separate derivatives. These low power conversion efficiencies were attributed to a high surface roughness with a large number of dewetting spots. Doping with 10% Polystyrene in the Indan-1,3-dione derivatives decreases surface roughness and dewetting spots thereby improving the efficiency of the devices. Efficiency of the devices was found as 0.39% and 0.51% for two derivatives after doping with polystyrene. The charge transfer mechanism was studied with photoluminescence quenching. The morphology and packing behavior of molecules were further studied using Atomic Force Microscopy (AFM) and X-ray diffraction (XRD).

Research Amplitudo Vibration On Holder Due To The Process Of Lathe Nozzle Rocket RX 450

Science.gov (United States)

Ediwan; Budi Djatmiko, Agus; Dody Arisandi, EfFendy; Purnomo, Heri; Ibadi, Mahfud

2018-04-01

The main function of the rocket nozzle is to convert the enthalpy efficiency from combustion gas to kinetic energy and also to make high velocity out of the gas. The rocket nozzle usually consists of a converging and diverging part. With a smaller area on the neck and enlarged at the exit area. The velocity flow through the nozzle enlarges into the speed of sound through the neck and then becomes super sonic in the divergent part. Nozzle making or machining using conventional lathes, first performed is drilling on a massive metal that is bonded to the veneer, then after a sufficient gap is done deep-boring. At the time of the process of lathe in the nozzle RX 450 there is an obstacle that is vibrating tool holder chisel or holder so it is worried about not precision of the process of lathe. This should not happen because it can cause failure in the latter for it needs to be studied and studied further so that the lathe process goes accordingly. The holder material of ST 60 with a modulus of elasticity 200 GPa and a nozzle material of AISI 4340 alloy steel with σyield = 470 MPa, Shear Modulus G = 80 GPa. The purpose of this research is to observe the amplitude of vibration on the holder due to RX- 450 nozzle lathe processing for the purpose of amplitude that occurs in accordance with the desired so that the nozzle structure is no damage process. The result of the research was obtained holder with length (L) 80cm, profile width (B) 5 cm, height of profile (H) 10 cm, turning machine ω = 8.98 rad / sec and natural holder frequency ωn = 89.8 rad / second, Amplitude of vibration of δ = 1.21 mm, while the amplitude of the design X = 1.22 mm From the results of this study it can be said that the holder of a chisel or holder can be used as a tool at the time of RX nozzle retrieval process and is quite safe because it works under the condition ω/ω n Rocket Payload "AKPV Engineering University of Wyoming 2009 )

Influence of predictive contamination to agricultural products due to dry and wet processes during an accidental release of radionuclides

International Nuclear Information System (INIS)

Hwang, Won Tae; Kim, Eun Han; Suh, Kyung Suk; Jeong, Hyo Joon; Han, Moon Hee; Lee, Chang Woo

2003-01-01

The influence of predictive contamination to agricultural products due to the wet processes as well as dry processes from radioactive air concentration during a nuclear emergency is comprehensively analyzed. The previous dynamic food chain model DYNACON considering Korean agricultural and environmental conditions, in which the initial input parameter was radionuclide concentrations on the ground, is improved so as to evaluate radioactive contamination to agricultural products from either radioactive air concentrations or radionuclide concentrations on the ground. As for the results, wet deposition is a more dominant mechanism than dry deposition in contamination on the ground. While, the contamination levels of agricultural products are strongly dependent on radionuclide and precipitation when the deposition of radionuclides occurs. It means that the contamination levels of agricultural products are determined from which is the more dominant process between deposition on the ground and interception to agricultural plants

Growth and evolution of nickel germanide nanostructures on Ge(001).

Science.gov (United States)

Grzela, T; Capellini, G; Koczorowski, W; Schubert, M A; Czajka, R; Curson, N J; Heidmann, I; Schmidt, Th; Falta, J; Schroeder, T

2015-09-25

Nickel germanide is deemed an excellent material system for low resistance contact formation for future Ge device modules integrated into mainstream, Si-based integrated circuit technologies. In this study, we present a multi-technique experimental study on the formation processes of nickel germanides on Ge(001). We demonstrate that room temperature deposition of ∼1 nm of Ni on Ge(001) is realized in the Volmer-Weber growth mode. Subsequent thermal annealing results first in the formation of a continuous NixGey wetting layer featuring well-defined terrace morphology. Upon increasing the annealing temperature to 300 °C, we observed the onset of a de-wetting process, characterized by the appearance of voids on the NixGey terraces. Annealing above 300 °C enhances this de-wetting process and the surface evolves gradually towards the formation of well-ordered, rectangular NixGey 3D nanostructures. Annealing up to 500 °C induces an Ostwald ripening phenomenon, with smaller nanoislands disappearing and larger ones increasing their size. Subsequent annealing to higher temperatures drives the Ni-germanide diffusion into the bulk and the consequent formation of highly ordered, {111} faceted Ni-Ge nanocrystals featuring an epitaxial relationship with the substrate Ni-Ge (101); (010) || Ge(001); (110).

Growth and evolution of nickel germanide nanostructures on Ge(001)

International Nuclear Information System (INIS)

Grzela, T; Capellini, G; Schubert, M A; Schroeder, T; Koczorowski, W; Czajka, R; Curson, N J; Heidmann, I; Schmidt, Th; Falta, J

2015-01-01

Nickel germanide is deemed an excellent material system for low resistance contact formation for future Ge device modules integrated into mainstream, Si-based integrated circuit technologies. In this study, we present a multi-technique experimental study on the formation processes of nickel germanides on Ge(001). We demonstrate that room temperature deposition of ∼1 nm of Ni on Ge(001) is realized in the Volmer–Weber growth mode. Subsequent thermal annealing results first in the formation of a continuous Ni_xGe_y wetting layer featuring well-defined terrace morphology. Upon increasing the annealing temperature to 300 °C, we observed the onset of a de-wetting process, characterized by the appearance of voids on the Ni_xGe_y terraces. Annealing above 300 °C enhances this de-wetting process and the surface evolves gradually towards the formation of well-ordered, rectangular Ni_xGe_y 3D nanostructures. Annealing up to 500 °C induces an Ostwald ripening phenomenon, with smaller nanoislands disappearing and larger ones increasing their size. Subsequent annealing to higher temperatures drives the Ni-germanide diffusion into the bulk and the consequent formation of highly ordered, {111} faceted Ni-Ge nanocrystals featuring an epitaxial relationship with the substrate Ni-Ge (101); (010) || Ge(001); (110). (paper)

SILTATION AND EROSION PROCESSES ON A TRIBUTARY OF LAKE ITAIPU DUE A DAM RESERVOIR

Directory of Open Access Journals (Sweden)

Cristiano Poleto

2012-12-01

creating an imbalance between the small amount of sediment transported after the hydroelectric and flow transport capacity. There are two cases occurring in a dam: 1 the dam upstream has a reduction of velocity and it start a process of sedimentation that will accelerate its siltation and reducing its useful life, 2 dam downstream has water velocity again and then initiate erosion process due the lack of sediments in the liquid mass. It can be concluded that changes of use and occupation of land in the watershed generate increased occurrence of peak flow and sediment transport, but the inadequate management of the area (with removal of riparian vegetation and lack of energy sinks in outputs of drainage systems potentiates the increasing the instability of water bodies morphology. In case of presence of reservoirs, the alterations are worst because they create siltation and erosion process at the same river.

Moving contact lines in partial wetting: bridging the gap across the scales

Science.gov (United States)

Pahlavan, Amir; Cueto-Felgueroso, Luis; McKinley, Gareth; Juanes, Ruben

2017-11-01

The spreading and dewetting of liquid films on solid substrates is a common phenomenon in nature and industry from a snail secreting a mucosal film to printing and coating processes. A quantitative description of these phenomena, however, requires a detailed understanding of the flow physics at the nanoscale as the intermolecular interactions become important close to the contact line. Classical hydrodynamic theory describes wetting as an interplay between viscous and interfacial forces, neglecting the intermolecular interactions, leading to a paradox known as the moving contact line singularity. By contrast, molecular kinetic theory describes wetting as an activated process, neglecting the bulk hydrodynamics in the spreading viscous fluid film altogether. Here, we show that our recently developed model for thin liquid films in partial wetting, which properly incorporates the role of van der Waals interactions in a thin spreading fluid layer into a height-dependent surface tension, bridges the gap between these two approaches and leads to a unified framework for the description of wetting phenomena. We further use our model to investigate the instability and dewetting of nanometric liquid films, and show that it brings theoretical predictions closer to experimental observations.

Super-Penrose process due to collisions inside ergosphere

Science.gov (United States)

Zaslavskii, O. B.

If two particles collide inside the ergosphere, the energy in the center of mass frame can be made unbound provided at least one of particles has a large negative angular momentum [A. A. Grib and Yu. V. Pavlov, Europhys. Lett. 101 (2013) 20004]. We show that the same condition can give rise to unbounded Killing energy of debris at infinity, i.e. super-Penrose process. Proximity of the point of collision to the black hole horizon is not required.

Selective modulation of nociceptive processing due to noise distraction.

Science.gov (United States)

Boyle, Yvonne; El-Deredy, Wael; Martínez Montes, Eduardo; Bentley, Deborah E; Jones, Anthony K P

2008-09-15

This study investigates the effects of noise distraction on the different components and sources of laser-evoked potentials (LEPs) whilst attending to either the spatial component (localisation performance task) or the affective component (unpleasantness rating task) of pain. LEPs elicited by CO2 laser stimulation of the right forearm were recorded from 64 electrodes in 18 consenting healthy volunteers. Subjects reported either pain location or unpleasantness, in the presence and absence of distraction by continuous 85 dBa white noise. Distributed sources of the LEP peaks were identified using Low Resolution Electromagnetic Tomography (LORETA). Pain unpleasantness ratings and P2 (430 ms) peak amplitude were significantly reduced by distraction during the unpleasantness task, whereas the localisation ability and the corresponding N1/N2 (310 ms) peak amplitude remained unchanged. Noise distraction (at 310 ms) reduced activation in the anterior cingulate cortex (ACC) and precuneus during attention to localisation and unpleasantness, respectively. This suggests a complimentary role for these two areas in the control of attention to pain. In contrast, activation of the occipital pole and SII were enhanced by noise during the localisation and unpleasantness task, respectively, suggesting that the presence of noise was associated with increased spatial attentional load. This study has shown selective modulation of affective pain processing by noise distraction, indicated by a reduction in the unpleasantness ratings and P2 peak amplitude and associated activity within the medial pain system. These results show that processing of the affective component of pain can be differentially modulated by top-down processes, providing a potential mechanism for therapeutic intervention.

Influence of radioactive contamination to agricultural products due to dry and wet deposition processes during a nuclear emergency

International Nuclear Information System (INIS)

Hwang, Won Tae; Kim, Eun Han; Suh, Kyung Suk; Han, Moon Hee; Choi, Yong Ho; Lee, Chang Woo

2002-01-01

Combined with deposition model onto the ground of radionuclides, the influence of radioactive contamination to agricultural products was analyzed due to wet deposition as well as dry deposition from radioactive air concentration during a nuclear emergency. The previous dynamic food chain model, in which initial input parameter is only radionuclide concentrations on the ground, was improved for the evaluating of radioactive contamination to agricultural products from either radionuclide concentrations in air or radionuclide concentrations on the ground. As the results, in case of deposition onto the ground, wet deposition was more dominant process than dry deposition. While the contamination levels of agricultural products were dependent on the a variety of factors such as radionuclides and rainfall rate. It means that the contamination levels of agricultural products are determined from which is more dominant process between deposition on the ground and interception onto agricultural plants

Constitutional Law--Procedural Due Process--Student Has Right to Have Attorney Present at University Disciplinary Hearing When Criminal Charges Are Pending.

Science.gov (United States)

Vessels, Rodney Jay

1978-01-01

In the case of Gabrilowitz v Newman the court used the due process balancing test to conclude that a student has a right to have counsel present at a university disciplinary hearing where the conduct in question is the object of a pending criminal proceeding. Available from J. Reuben Clark Law School, Brigham Young U., Provo, UT 84602. (MSE)

Dynamic Wetting Behavior of Vibrated Droplets on a Micropillared Surface

Directory of Open Access Journals (Sweden)

Zhi-hai Jia

2016-01-01

Full Text Available The dynamical wetting behavior has been observed under vertical vibration of a water droplet placed on a micropillared surface. The wetting transition takes place under the different processes. In compression process, the droplet is transited from Cassie state to Wenzel state. The droplet undergoes a Wenzel-Cassie wetting transition in restoring process and the droplet bounces off from the surface in bouncing process. Meanwhile, the wetting and dewetting models during vibration are proposed. The wetting transition is confirmed by the model calculation. This study has potential to be used to control the wetting state.

Reviewing IT in due diligence are you buying an IT asset or liability

CERN Document Server

Wright, Christopher

2015-01-01

Reviewing IT in Due Diligence provides an introduction to IRM in due diligence, and outlines some of the key IT issues to consider as part of the due diligence process. For those new to the process, it explains how to conduct an IT due diligence review, from scoping to reporting, and includes information on post-merger integration to realise business benefits from the deal. For more experienced practitioners, Reviewing IT in Due Diligence provides fresh insight into the process, highlighting issues that need to be addressed, and provides a business case for IRM involvement in the due diligenc

Investigation on the morphological and optical evolution of bimetallic Pd-Ag nanoparticles on sapphire (0001) by the systematic control of composition, annealing temperature and time.

Science.gov (United States)

Pandey, Puran; Kunwar, Sundar; Sui, Mao; Bastola, Sushil; Lee, Jihoon

2017-01-01

Multi-metallic alloy nanoparticles (NPs) can offer additional opportunities for modifying the electronic, optical and catalytic properties by the control of composition, configuration and size of individual nanostructures that are consisted of more than single element. In this paper, the fabrication of bimetallic Pd-Ag NPs is systematically demonstrated via the solid state dewetting of bilayer thin films on c-plane sapphire by governing the temperature, time as well as composition. The composition of Pd-Ag bilayer remarkably affects the morphology of alloy nanostructures, in which the higher Ag composition, i.e. Pd0.25Ag0.75, leads to the enhanced dewetting of bilayers whereas the higher Pd composition (Pd0.75Ag0.25) hinders the dewetting. Depending on the annealing temperature, Pd-Ag alloy nanostructures evolve with a series of configurations, i.e. nucleation of voids, porous network, elongated nanoclusters and round alloy NPs. In addition, with the annealing time set, the gradual configuration transformation from the elongated to round alloy NPs as well as size reduction is demonstrated due to the enhanced diffusion and sublimation of Ag atoms. The evolution of various morphology of Pd-Ag nanostructures is described based on the surface diffusion and inter-diffusion of Pd and Ag adatoms along with the Ag sublimation, Rayleigh instability and energy minimization mechanism. The reflectance spectra of bimetallic Pd-Ag nanostructures exhibit various quadrupolar and dipolar resonance peaks, peak shifts and absorption dips owing to the surface plasmon resonance of nanostructures depending on the surface morphology. The intensity of reflectance spectra is gradually decreased along with the surface coverage and NP size evolution. The absorption dips are red-shifted towards the longer wavelength for the larger alloy NPs and vice-versa.

Investigation on the morphological and optical evolution of bimetallic Pd-Ag nanoparticles on sapphire (0001 by the systematic control of composition, annealing temperature and time.

Directory of Open Access Journals (Sweden)

Puran Pandey

Full Text Available Multi-metallic alloy nanoparticles (NPs can offer additional opportunities for modifying the electronic, optical and catalytic properties by the control of composition, configuration and size of individual nanostructures that are consisted of more than single element. In this paper, the fabrication of bimetallic Pd-Ag NPs is systematically demonstrated via the solid state dewetting of bilayer thin films on c-plane sapphire by governing the temperature, time as well as composition. The composition of Pd-Ag bilayer remarkably affects the morphology of alloy nanostructures, in which the higher Ag composition, i.e. Pd0.25Ag0.75, leads to the enhanced dewetting of bilayers whereas the higher Pd composition (Pd0.75Ag0.25 hinders the dewetting. Depending on the annealing temperature, Pd-Ag alloy nanostructures evolve with a series of configurations, i.e. nucleation of voids, porous network, elongated nanoclusters and round alloy NPs. In addition, with the annealing time set, the gradual configuration transformation from the elongated to round alloy NPs as well as size reduction is demonstrated due to the enhanced diffusion and sublimation of Ag atoms. The evolution of various morphology of Pd-Ag nanostructures is described based on the surface diffusion and inter-diffusion of Pd and Ag adatoms along with the Ag sublimation, Rayleigh instability and energy minimization mechanism. The reflectance spectra of bimetallic Pd-Ag nanostructures exhibit various quadrupolar and dipolar resonance peaks, peak shifts and absorption dips owing to the surface plasmon resonance of nanostructures depending on the surface morphology. The intensity of reflectance spectra is gradually decreased along with the surface coverage and NP size evolution. The absorption dips are red-shifted towards the longer wavelength for the larger alloy NPs and vice-versa.

Atomically flat surface of (0 0 1) textured FePt thin films by residual stress control

Energy Technology Data Exchange (ETDEWEB)

Liu, S.H. [Department of Materials Science and Engineering, Feng Chia University, Taichung 407, Taiwan (China); Hsiao, S.N., E-mail: pmami.hsiao@gmail.com [Department of Materials Science and Engineering, Feng Chia University, Taichung 407, Taiwan (China); Department of Power Mechanical Engineering, National Tsing Hua University, Hsinchu 300, Taiwan (China); Chou, C.L.; Chen, S.K. [Department of Materials Science and Engineering, Feng Chia University, Taichung 407, Taiwan (China); Lee, H.Y. [National Synchrotron Radiation Research Center, Hsinchu 300, Taiwan (China); Department of Applied Science, National Hsinchu University of Education, Hsinchu 300, Taiwan (China)

2015-11-01

Highlights: • We demonstrate crystallographic structure, (0 0 1) texture, surface roughness, and residual stress in the single-layered FePt thin films annealed at various heating rates (10–110 K/s). • Texture coefficient of (0 0 1)-plane of the samples increases with increasing heating rate from 10 to 40 K/s, which is correlated with perpendicular magnetic anisotropy and in-plane tensile stress. • Dewetting phenomenon due to stress relaxation leads to the broadening of [0 0 1] easy axis and degradation of perpendicular magnetic anisotropy. • A strong dependence of surface roughness on in-plane residual stress was revealed. • When the samples are RTA at 40 K/s, the enhanced perpendicular magnetic anisotropy and atomically surface roughness are achieved. - Abstract: Single-layered Fe{sub 52}Pt{sub 48} films with thickness of 10 nm were sputter-deposited on glass substrates. Rapid thermal annealing with different heating rates (10–110 K/s) was applied to transform as-deposited fcc phase into L1{sub 0} phase and meanwhile to align [0 0 1]-axis of L1{sub 0} crystal along plane normal direction. Based on X-ray diffractometry using synchrotron radiation source, the texture coefficient of (0 0 1)-plane increases with increasing heating rate from 10 to 40 K/s, which is correlated with perpendicular magnetic anisotropy and in-plane tensile stress analyzed by asymmetric sin{sup 2} ψ method. Furthermore, it was revealed by atomic force microscopy that the dewetting process occurred as heating rate was raised up to 80 K/s and higher. The change in the microstructure due to stress relaxation leads to the degradation of (0 0 1) orientation and magnetic properties. Surface roughness is closely related to the in-plane tensile stress. Enhanced perpendicular magnetic anisotropy and atomically flat surface were achieved for the samples annealed at 40 K/s, which may be suitable for further practical applications. This work also suggests a feasible way for surface

Variation Process of Radiation Belt Electron Fluxes due to Interaction With Chorus and EMIC Rising-tone Emissions Localized in Longitude

Science.gov (United States)

Kubota, Y.; Omura, Y.

2017-12-01

Using results of test particle simulations of a large number of electrons interacting with a pair of chorus emissions, we create Green's functions to model the electron distribution function after all of the possible interactions with the waves [Omura et al., 2015]. Assuming that the waves are generated in a localized range of longitudes in the dawn side, we repeat taking the convolution integral of the Green's function with the distribution function of the electrons injected into the generation region of the localized waves. From numerical and theoretical analyses, we find that electron acceleration process only takes place efficiently below 4 MeV. Because extremely relativistic electrons go through the wave generation region rapidly due to grad-B0 and curvature drift, they don't have enough interaction time to be accelerated. In setting up the electrons after all interaction with chorus emissions as initial electron distribution function, we also compute the loss process of radiation belt electron fluxes due to interaction with EMIC rising-tone emissions generated in a localized range of longitudes in the dusk side [Kubota and Omura,2017]. References: (1) Omura, Y., Y. Miyashita, M. Yoshikawa, D. Summers, M. Hikishima, Y. Ebihara, and Y. Kubota (2015), Formation process of relativistic electron flux through interaction with chorus emissions in the Earth's inner magnetosphere, J. Geophys. Res. Space Physics, 120, 9545-9562, doi:10.1002/2015JA021563. (2) Kubota, Y., and Y. Omura (2017), Rapid precipitation of radiation belt electrons induced by EMIC rising tone emissions localized in longitude inside and outside the plasmapause, J. Geophys. Res. Space Physics, 122, 293-309, doi:10.1002/2016JA023267.

High speed direct imaging of thin metal film ablation by movie-mode dynamic transmission electron microscopy

Science.gov (United States)

Hihath, Sahar; Santala, Melissa K.; Cen, Xi; Campbell, Geoffrey; van Benthem, Klaus

2016-03-01

Obliteration of matter by pulsed laser beams is not only prevalent in science fiction movies, but finds numerous technological applications ranging from additive manufacturing over machining of micro- and nanostructured features to health care. Pulse lengths ranging from femtoseconds to nanoseconds are utilized at varying laser beam energies and pulse lengths, and enable the removal of nanometric volumes of material. While the mechanisms for removal of material by laser irradiation, i.e., laser ablation, are well understood on the micrometer length scale, it was previously impossible to directly observe obliteration processes on smaller scales due to experimental limitations for the combination of nanometer spatial and nanosecond temporal resolution. Here, we report the direct observation of metal thin film ablation from a solid substrate through dynamic transmission electron microscopy. Quantitative analysis reveals liquid-phase dewetting of the thin-film, followed by hydrodynamic sputtering of nano- to submicron sized metal droplets. We discovered unexpected fracturing of the substrate due to evolving thermal stresses. This study confirms that hydrodynamic sputtering remains a valid mechanism for droplet expulsion on the nanoscale, while irradiation induced stress fields represent limit laser processing of nanostructured materials. Our results allow for improved safety during laser ablation in manufacturing and medical applications.

The Substantive and Procedural Due Process Rights of Students Accused of Criminal Behavior in School and the Educational Rights of Adjudicated Youths.

Science.gov (United States)

Brown, Frank

This paper--part of a collection of 54 papers from the 48th annual conference of the Education Law Association held in November 2002-- addresses juvenile justice. Its central issue is how to protect children of color in elementary and secondary schools with constitutional due process where attendance is compulsory and, at the same time, maintain a…

Equilibrium positions due to different cooling processes in superconducting levitation systems

International Nuclear Information System (INIS)

Navau, C; Sanchez, A; Pardo, E; Chen, D-X

2004-01-01

The equilibrium position of a superconducting levitation device is determined not only by the geometry and electromagnetic properties of its components, but also by the cooling process of the superconductor. In this work we study the dependence of the equilibrium positions upon the cooling process by introducing diagrams of a new kind which display the different possibilities for a given levitation system. Using the critical state model and the principle of magnetic energy, we calculate different diagrams of this type for the case of a cylindrically symmetric permanent magnet-superconductor system. The results allow us to find out, for a given levitation system, which cooling process improves the capabilities of the system

Online interferometric study of viscoelastic rupture and necking deformation of as-spun (iPP) fibres due to creep process.

Science.gov (United States)

Sokkar, Taha; El-Farahaty, Kermal; Azzam, Amira

2015-01-01

Creep deformation under constant load leads to rupture when the polymer chains can no longer separate and accommodate the load. This fracture phenomenon is investigated interferometrically. The creep behaviour of as-spun isotactic Polypropylene (iPP) fibres is studied at different stresses, different initial lengths and different radii. The creep rate, which defines the velocity of the creep deformation and the dimensional stability of the material, is studied. The failure time and stress of iPP due to creep process is determined. The necking deformation was in situ detected during creep process. The mean refractive indices (n(P) andn⊥) profiles of iPP fibres were determined at different positions along the fibre axis before and after necking. The relation between the creep behaviour and different optical and structural parameters is investigated. Microinterferograms are given for illustration. © 2015 The Authors Journal of Microscopy © 2015 Royal Microscopical Society.

On the Internal Structure of Mobile Barchan Sand Dunes due to Granular Processes

Science.gov (United States)

Vriend, N. M.; Arran, M.; Louge, M. Y.; Hay, A. G.; Valance, A.

2017-12-01

In this work, we visualize the internal structure of mobile barchan desert dunes at the avalanche scale. We reveal an intriguing history of dune building using a novel combination of local sand sampling and advanced geophysical techniques resulting in high resolution measurements of individual avalanche events. Due to progressive rebuilding, granular avalanching, erosional and depositional processes, these marching barchan dunes are reworked every few years and a characteristic zebra-pattern (figure 1a), orientated parallel to the slipface at the angle of repose, appears at regular intervals. We present scientific data on the structure obtained from several mobile barchan dunes of different sizes during recent desert field campaigns (2014, 2015, 2017) in a mobile barchan dune field in Qatar (25.01°N, 51.34°E in the AlWakrah municipality). The site has been equipped with a weather station and has been regularly visited by a multidisciplinary research team in recent years (e.g. [1]). By applying high-frequency (1200 MHz) ground penetrating radar (GPR) transects across the midline (figure 1b) we map the continuous evolution of this cross-bedding at high resolution deep within the dune. The GPR reveals a slope reduction of the slipface near the base of the dune; evidence of irregular wind reversals; and the presence of a harder aeolian cap around the crest and extending to the brink. The data is supplemented with granulometry from layers stabilized by dyed water injection and uncovered by excavating vertical walls perpendicular to old buried avalanches. We attribute visible differences in water penetration between adjacent layers to fine particle segregation processes in granular avalanches. This work was made possible by the support of NPRP grant 6-059-2-023 from the Qatar National Research Fund to MYL and AGH, and a Royal Society Dorothy Hodgkin Research Fellowship to NMV. We thank Jean-Luc Métayer for performing detailed particle size distribution measurements

Impact of pH on hydrogen oxidizing redox processes in aquifers due to gas intrusions

Science.gov (United States)

Metzgen, Adrian; Berta, Marton; Dethlefsen, Frank; Ebert, Markus; Dahmke, Andreas

2017-04-01

Hydrogen production from excess energy and its storage can help increasing the efficiency of solar and wind in the energy mix. Therefore, hydrogen needs large-scale intermediate storage independent of the intended later use as hydrogen gas or as reactant to produce methane in the Sabatier process. A possible storage solution is using the geological subsurface such as caverns built in salt deposits or aquifers that are not used for drinking water production. However, underground storage of hydrogen gas potentially leads to accidental gas leakages into near-surface potable aquifers triggering subsequent geochemical processes. These leakages pose potential risks that are currently not sufficiently understood. To close this gap in knowledge, a high-pressure laboratory column system was used to simulate a hydrogen gas intrusion into a shallow aquifer. Water and sediment were gained from a sandy Pleistocene aquifer near Neumünster, Germany. In the first stage of the experiment, 100% hydrogen gas was used to simulate dissolved hydrogen concentrations between 800 and 4000 µM by varying pH2 between 2 and 15 bars. pH values rose to between 7.9 and 10.4, partly due to stripping CO2 from the groundwater used during H2 gas addition. In a second stage, the pH was regulated in a range of 6.7 to 7.9 by using a gas mixture of 99% H2 and 1% CO2 at 5 bars of total gas pressure. Observed processes included hydrogen oxidation, sulfate reduction, acetogenesis, formate production, and methanogenesis, which were independent of the hydrogen concentration. Hydrogen oxidation and sulfate reduction showed zeroth order reaction rates and rate constants (106 to 412 µM/h and 12 to 33 µM/h, respectively) in the pH range between 8 and 10. At pH levels between 7 and 8, both reactions started out faster near the column's inflow but then seemed limited towards the columns outflow, suggesting the dependence of sulfate reduction on the pH-value. Acetogenesis dominated the pH range between 8 and 10

Conformation-dependent DNA attraction

Science.gov (United States)

Li, Weifeng; Nordenskiöld, Lars; Zhou, Ruhong; Mu, Yuguang

2014-05-01

Understanding how DNA molecules interact with other biomolecules is related to how they utilize their functions and is therefore critical for understanding their structure-function relationships. For a long time, the existence of Z-form DNA (a left-handed double helical version of DNA, instead of the common right-handed B-form) has puzzled the scientists, and the definitive biological significance of Z-DNA has not yet been clarified. In this study, the effects of DNA conformation in DNA-DNA interactions are explored by molecular dynamics simulations. Using umbrella sampling, we find that for both B- and Z-form DNA, surrounding Mg2+ ions always exert themselves to screen the Coulomb repulsion between DNA phosphates, resulting in very weak attractive force. On the contrary, a tight and stable bound state is discovered for Z-DNA in the presence of Mg2+ or Na+, benefiting from their hydrophobic nature. Based on the contact surface and a dewetting process analysis, a two-stage binding process of Z-DNA is outlined: two Z-DNA first attract each other through charge screening and Mg2+ bridges to phosphate groups in the same way as that of B-DNA, after which hydrophobic contacts of the deoxyribose groups are formed via a dewetting effect, resulting in stable attraction between two Z-DNA molecules. The highlighted hydrophobic nature of Z-DNA interaction from the current study may help to understand the biological functions of Z-DNA in gene transcription.Understanding how DNA molecules interact with other biomolecules is related to how they utilize their functions and is therefore critical for understanding their structure-function relationships. For a long time, the existence of Z-form DNA (a left-handed double helical version of DNA, instead of the common right-handed B-form) has puzzled the scientists, and the definitive biological significance of Z-DNA has not yet been clarified. In this study, the effects of DNA conformation in DNA-DNA interactions are explored by

Human due diligence.

Science.gov (United States)

Harding, David; Rouse, Ted

2007-04-01

Most companies do a thorough job of financial due diligence when they acquire other companies. But all too often, deal makers simply ignore or underestimate the significance of people issues in mergers and acquisitions. The consequences are severe. Most obviously, there's a high degree of talent loss after a deal's announcement. To make matters worse, differences in decision-making styles lead to infighting; integration stalls; and productivity declines. The good news is that human due diligence can help companies avoid these problems. Done early enough, it helps acquirers decide whether to embrace or kill a deal and determine the price they are willing to pay. It also lays the groundwork for smooth integration. When acquirers have done their homework, they can uncover capability gaps, points of friction, and differences in decision making. Even more important, they can make the critical "people" decisions-who stays, who goes, who runs the combined business, what to do with the rank and file-at the time the deal is announced or shortly thereafter. Making such decisions within the first 30 days is critical to the success of a deal. Hostile situations clearly make things more difficult, but companies can and must still do a certain amount of human due diligence to reduce the inevitable fallout from the acquisition process and smooth the integration. This article details the steps involved in conducting human due diligence. The approach is structured around answering five basic questions: Who is the cultural acquirer? What kind of organization do you want? Will the two cultures mesh? Who are the people you most want to retain? And how will rank-and-file employees react to the deal? Unless an acquiring company has answered these questions to its satisfaction, the acquisition it is making will be very likely to end badly.

Discipline and Due Process.

Science.gov (United States)

Collins, Mildred; Dowell, Mary L.

1998-01-01

Increasing numbers of parents do not accept a school's discipline policy and are refusing to permit their children to comply with disciplinary sanctions. According to the California Education Code, educators have the right to expect parents to accept disciplinary decisions made in compliance with required procedures. Parental defiance might worsen…

Red-luminescence band: A tool for the quality assessment of germanium and silicon nanocrystals

Science.gov (United States)

Fraj, I.; Favre, L.; David, T.; Abbarchi, M.; Liu, K.; Claude, J. B.; Ronda, A.; Naffouti, M.; Saidi, F.; Hassen, F.; Maaref, H.; Aqua, J. N.; Berbezier, I.

2017-10-01

We present the photoluminescence (PL) emission of Silicon and Germanium nanocrystals (NCs) of different sizes embedded in two different matrices. Formation of the NCs is achieved via solid-state dewetting during annealing in a molecular beam epitaxy ultra-high vacuum system of ultrathin amorphous Si and Ge layers deposited at room temperature on SiO2. During the dewetting process, the bi-dimensional amorphous layers transform into small pseudo-spherical islands whose mean size can be tuned directly with the deposited thickness. The nanocrystals are capped either ex situ by silicon dioxide or in situ by amorphous Silicon. The surface-state dependent emission (typically in the range 1.74 eV-1.79 eV) exhibited higher relative PL quantum yields compared to the emission originating from the band gap transition. This red-PL emission comes from the radiative transitions between a Si band and an interface level. It is mainly ascribed to the NCs and environment features deduced from morphological and structural analyses. Power dependent analysis of the photoluminescence intensity under continuous excitation reveals a conventional power law with an exponent close to 1, in agreement with the type II nature of the emission. We show that Ge-NCs exhibit much lower quantum efficiency than Si-NCs due to non-radiative interface states. Low quantum efficiency is also obtained when NCs have been exposed to air before capping, even if the exposure time is very short. Our results indicate that a reduction of the non-radiative surface states is a key strategy step in producing small NCs with increased PL emission for a variety of applications. The red-PL band is then an effective tool for the quality assessment of NCs based structures.

Brand-name drug, generic drug, orphan drug. Pharmacological therapy with biosimilar drugs - provision of due diligence in the treatment process.

Science.gov (United States)

Zajdel, Justyna; Zajdel, Radosław

2013-01-01

Due diligence in the process of provision of healthcare services refers, among other elements, to the application of pharmacological therapy at a time which offers the greatest chance for a successful outcome of treatment, i.e. for achieving the optimum expected effect understood as an improvement in the patient's health, reduction of health risks or elimination of the disease. However, due diligence may also refer to actions aimed at ensuring that neither the patient nor the healthcare payer is required to incur unreasonable costs in the process of treatment. The validity of that statement stems not only from normative acts but also from ethical standards laid down in the Medical Code of Ethics (Article 57 section 2). It often happens that the provision of optimal treatment calls for deviations from the formal provisions included in Summary Product Characteristics (SPCs), and the application of drugs that are bioequivalent to reference drugs, which translates into a significant reduction of costs. The present study addresses the problem of acceptability of a specific form of drug substitution consisting in the replacement of a reference drug with a generic drug. Also explored are legal aspects associated with the possibility of therapy based on "off-label use". The study reviews normative acts existing in the Polish and EU legislation. It also provides a clear definition of orphan drug, which has made it possible to make a distinction and investigate mutual relations between the concepts of brand-name (reference) drug, orphan drug and generic drug.

Length of proceedings as standard of due process of law in the practise of the Constitutional Court of Albania

Directory of Open Access Journals (Sweden)

Elsa Toska Dobjani

2016-01-01

Full Text Available ECHR, as an international treaty is part of the Albanian legal system. Among international law instruments, the ECHR enjoys a privileged status in the Albanian legal system by virtue of Article 17 paragraph 2 of the Constitution according to which restrictions to human rights and freedoms cannot infringe the substance of those rights and freedoms and in no case can exceed the restrictions provided for in the ECHR. Article 1 of the Convention requires States to secure the substance of the rights to those in their jurisdiction. The effect of Article 13 is thus to require the provision of a domestic remedy to deal with the substance of an arguable complaint under the Convention and to grant appropriate relief. The scope of this paper is to analyse the effectiveness of the complaint to the Constitutional Court with regard to length of proceedings as part of due process of law in terms of proceedings during the court trial and after the process has been finalized and the final decision should be executed.

Structural investigations of silicon nanostructures grown by self-organized island formation for photovoltaic applications

Energy Technology Data Exchange (ETDEWEB)

Roczen, Maurizio; Malguth, Enno; Barthel, Thomas; Gref, Orman; Toefflinger, Jan A.; Schoepke, Andreas; Schmidt, Manfred; Ruske, Florian; Korte, Lars; Rech, Bernd [Institute for Silicon Photovoltaics, Helmholtz-Zentrum Berlin, Berlin (Germany); Schade, Martin; Leipner, Hartmut S. [Martin-Luther-Universitaet Halle-Wittenberg, Interdisziplinaeres Zentrum fuer Materialwissenschaften, Halle (Germany); Callsen, Gordon; Hoffmann, Axel [Technische Universitaet Berlin, Institut fuer Festkoerperphysik, Berlin (Germany); Phillips, Matthew R. [University of Technology Sydney, Department of Physics and Advanced Materials, NSW (Australia)

2012-09-15

The self-organized growth of crystalline silicon nanodots and their structural characteristics are investigated. For the nanodot synthesis, thin amorphous silicon (a-Si) layers with different thicknesses have been deposited onto the ultrathin (2 nm) oxidized (111) surface of Si wafers by electron beam evaporation under ultrahigh vacuum conditions. The solid phase crystallization of the initial layer is induced by a subsequent in situ annealing step at 700 C, which leads to the dewetting of the initial a-Si layer. This process results in the self-organized formation of highly crystalline Si nanodot islands. Scanning electron microscopy confirms that size, shape, and planar distribution of the nanodots depend on the thickness of the initial a-Si layer. Cross-sectional investigations reveal a single-crystalline structure of the nanodots. This characteristic is observed as long as the thickness of the initial a-Si layer remains under a certain threshold triggering coalescence. The underlying ultra-thin oxide is not structurally affected by the dewetting process. Furthermore, a method for the fabrication of close-packed stacks of nanodots is presented, in which each nanodot is covered by a 2 nm thick SiO{sub 2} shell. The chemical composition of these ensembles exhibits an abrupt Si/SiO{sub 2} interface with a low amount of suboxides. A minority charge carrier lifetime of 18 {mu}s inside of the nanodots is determined. (orig.)

Thin film phase and local chirality of surface-bound MOP4 nanofibers

DEFF Research Database (Denmark)

Balzer, Frank; Röthel, Christian; Rubahn, Horst-Günter

2016-01-01

Vacuum deposition of the methoxy-functionalized p-quaterphenylene MOP4 on muscovite mica at elevated temperatures led to the formation of several ten micrometer long nanofibers. As shown by X-ray diffraction and polarized optical microscopy, the fibers are formed by lying molecules which grow...... diffraction (LEED) that had a crystal structure different from that of the fibers. Transfer of the sample from a vacuum to ambient conditions led to dewetting and the formation of clusters from the lying molecules. The samples aged via Ostwald ripening due to the presence of water vapor, which was monitored...

Surface Self-Assembly and Properties of Monolayers Formed by Reverse Poly(butylene oxide)-poly(ethylene oxide)-poly(butylene oxide) Triblock Copolymers with Lengthy Hydrophilic Blocks

DEFF Research Database (Denmark)

Villar-Alvarez, Eva; Freire, Adriana Cambón; Blanco, Mateo

2017-01-01

for the former at low surface transfer pressures, evolving to continent-like structures first and then dewetted structures as the transfer pressure increases. Conversely, for BO20EO411BO20 and BO21EO385BO21 copolymers micelle formation is noted at lower transfer pressures than the shortest counterparts......, and the formed micelles appear to be elongated, interconnected and with larger thickness. As the transfer pressure increases, attractive micellar interactions are enhanced and then-lead to formation of a dense network of interconnected micelles, first followed by an evolvement to continent-like and dewetted...

Multi-Objective Flexible Flow Shop Scheduling Problem Considering Variable Processing Time due to Renewable Energy

Directory of Open Access Journals (Sweden)

Xiuli Wu

2018-03-01

Full Text Available Renewable energy is an alternative to non-renewable energy to reduce the carbon footprint of manufacturing systems. Finding out how to make an alternative energy-efficient scheduling solution when renewable and non-renewable energy drives production is of great importance. In this paper, a multi-objective flexible flow shop scheduling problem that considers variable processing time due to renewable energy (MFFSP-VPTRE is studied. First, the optimization model of the MFFSP-VPTRE is formulated considering the periodicity of renewable energy and the limitations of energy storage capacity. Then, a hybrid non-dominated sorting genetic algorithm with variable local search (HNSGA-II is proposed to solve the MFFSP-VPTRE. An operation and machine-based encoding method is employed. A low-carbon scheduling algorithm is presented. Besides the crossover and mutation, a variable local search is used to improve the offspring’s Pareto set. The offspring and the parents are combined and those that dominate more are selected to continue evolving. Finally, two groups of experiments are carried out. The results show that the low-carbon scheduling algorithm can effectively reduce the carbon footprint under the premise of makespan optimization and the HNSGA-II outperforms the traditional NSGA-II and can solve the MFFSP-VPTRE effectively and efficiently.

Process Measurement Deviation Analysis for Flow Rate due to Miscalibration

Energy Technology Data Exchange (ETDEWEB)

Oh, Eunsuk; Kim, Byung Rae; Jeong, Seog Hwan; Choi, Ji Hye; Shin, Yong Chul; Yun, Jae Hee [KEPCO Engineering and Construction Co., Deajeon (Korea, Republic of)

2016-10-15

An analysis was initiated to identify the root cause, and the exemption of high static line pressure correction to differential pressure (DP) transmitters was one of the major deviation factors. Also the miscalibrated DP transmitter range was identified as another major deviation factor. This paper presents considerations to be incorporated in the process flow measurement instrumentation calibration and the analysis results identified that the DP flow transmitter electrical output decreased by 3%. Thereafter, flow rate indication decreased by 1.9% resulting from the high static line pressure correction exemption and measurement range miscalibration. After re-calibration, the flow rate indication increased by 1.9%, which is consistent with the analysis result. This paper presents the brief calibration procedures for Rosemount DP flow transmitter, and analyzes possible three cases of measurement deviation including error and cause. Generally, the DP transmitter is required to be calibrated with precise process input range according to the calibration procedure provided for specific DP transmitter. Especially, in case of the DP transmitter installed in high static line pressure, it is important to correct the high static line pressure effect to avoid the inherent systematic error for Rosemount DP transmitter. Otherwise, failure to notice the correction may lead to indicating deviation from actual value.

Evaluation of the Process of Solvent Vapor Annealing on Organic Thin Films

KAUST Repository

Ren, Yi

2011-07-01

Solvent vapor annealing has recently emerged as an intriguing, room-temperature, and highly versatile alternative to thermal annealing. The chemically selective interaction between solvents and organic semiconductors opens new opportunities to selectively anneal certain components of the device, while leaving others intact. On the downside, these interactions are complex and rather unpredictable, requiring further investigation. We propose a novel methodology to investigate solvent-film interactions, based on use of an in situ quartz crystal microbalance with dissipation (QCM-D) capability and in situ grazing incidence wide angle X-ray scattering (GIWAXS). These methods make it possible to investigate both qualitatively and quantitatively the solvent vapor uptake, the resulting softening and changes (reversible and/or irreversible) in crystallinity. Using this strategy, we have investigated the solvent vapor annealing of traditional donor and acceptor materials, namely poly(3-hexylthiophene-2,5-diyl) (P3HT) and [6,6]-Phenyl-C61-butyric acid methyl ester (PCBM). We find these materials retain their rigid structure during toluene vapor annealing and do not dewet. We also investigated the toluene vapor annealing of several newly proposed acceptor molecules (pentacene-based) modified with various silyl groups and electron withdrawing groups to tune the packing structure of the acceptor domains and energy levels at the donor-acceptor interface. We found a dramatic effect of the electron-withdrawing group on vapor uptake and whether the film remains rigid, softens, or dissolves completely. In the case of trifluoromethyl electron-withdrawing group, we found the film dissolves, resulting in complete and irreversible loss of long range order. By contrast, the cyano group prevented loss of long range order, instead promoting crystallization in some cases. The silyl groups had a secondary effect in comparison to these. In the last part of the thesis, we investigated the

Conducting financial due diligence of medical practices.

Science.gov (United States)

Louiselle, P

1995-12-01

Many healthcare organizations are acquiring medical practices in an effort to build more integrated systems of healthcare products and services. This acquisition activity must be approached cautiously to ensure that medical practices being acquired do not have deficiencies that would jeopardize integration efforts. Conducting a thorough due diligence analysis of medical practices before finalizing the transaction can limit the acquiring organizations' legal and financial exposure and is a necessary component to the acquisition process. The author discusses the components of a successful financial due diligence analysis and addresses some of the risk factors in a practice acquisition.

34 CFR 682.208 - Due diligence in servicing a loan.

Science.gov (United States)

2010-07-01

... 34 Education 3 2010-07-01 2010-07-01 false Due diligence in servicing a loan. 682.208 Section 682.208 Education Regulations of the Offices of the Department of Education (Continued) OFFICE OF... § 682.208 Due diligence in servicing a loan. (a) The loan servicing process includes reporting to...

Brand-name drug, generic drug, orphan drug. Pharmacological therapy with biosimilar drugs – provision of due diligence in the treatment process

Science.gov (United States)

Zajdel, Justyna

2013-01-01

Due diligence in the process of provision of healthcare services refers, among other elements, to the application of pharmacological therapy at a time which offers the greatest chance for a successful outcome of treatment, i.e. for achieving the optimum expected effect understood as an improvement in the patient's health, reduction of health risks or elimination of the disease. However, due diligence may also refer to actions aimed at ensuring that neither the patient nor the healthcare payer is required to incur unreasonable costs in the process of treatment. The validity of that statement stems not only from normative acts but also from ethical standards laid down in the Medical Code of Ethics (Article 57 section 2). It often happens that the provision of optimal treatment calls for deviations from the formal provisions included in Summary Product Characteristics (SPCs), and the application of drugs that are bioequivalent to reference drugs, which translates into a significant reduction of costs. The present study addresses the problem of acceptability of a specific form of drug substitution consisting in the replacement of a reference drug with a generic drug. Also explored are legal aspects associated with the possibility of therapy based on “off-label use”. The study reviews normative acts existing in the Polish and EU legislation. It also provides a clear definition of orphan drug, which has made it possible to make a distinction and investigate mutual relations between the concepts of brand-name (reference) drug, orphan drug and generic drug. PMID:24592133

Constitutional Law--Irrebuttable Statutory Presemption of Student Non-Residency Held Violative of Due Process Clause of Fourteenth Amendment--Vlandis v. Kline, 93 S. Ct. 2230 (1973)

Science.gov (United States)

University of Richmond Law Review, 1974

1974-01-01

In the past the durational residence requirement in colleges and universities has been subject to constitutional challenge under the equal protection clause of the fourteenth amendment. The durational residence requirement in this case displays a further fourteenth amendment vulnerability--the contravention of procedural due process. (Author/PG)

Anomalous scaling due to correlations: limit theorems and self-similar processes

International Nuclear Information System (INIS)

Stella, Attilio L; Baldovin, Fulvio

2010-01-01

We derive theorems which outline explicit mechanisms by which anomalous scaling for the probability density function of the sum of many correlated random variables asymptotically prevails. The results characterize general anomalous scaling forms, explain their universal character, and specify universality domains in the spaces of joint probability density functions of the summand variables. These density functions are assumed to be invariant under arbitrary permutations of their arguments. Examples from the theory of critical phenomena are discussed. The novel notion of stability implied by the limit theorems also allows us to define sequences of random variables whose sum satisfies anomalous scaling for any finite number of summands. If regarded as developing in time, the stochastic processes described by these variables are non-Markovian generalizations of Gaussian processes with uncorrelated increments, and provide, e.g., explicit realizations of a recently proposed model of index evolution in finance

Effects of Cu interlayer on the wettability of aluminum on carbon

Energy Technology Data Exchange (ETDEWEB)

Ko, Young Jin [School of Advanced Material Engineering, Yonsei University, Seoul 120-749 (Korea, Republic of); Yoon, Juil [Department of Mechanical Systems Engineering, Hansung University, Seoul 136-792 (Korea, Republic of); Lee, Joonho [Department of Materials Science and Engineering, Korea University, Seoul 136-701 (Korea, Republic of); Han, Jun Hyun, E-mail: jhhan@cnu.ac.kr [Department of Nano Materials Engineering, Chungnam National University, Daejeon 305-764 (Korea, Republic of)

2013-10-15

Highlights: •The enhancement of wettability of Al on the Cu-coated graphite was restricted by the dewetting of the Cu layer. •The pre-sputtering of Cu could enhanced the wettability of Al more than the Cu single layer coating using electroless plating. •A thick Cu coating layer is needed to enhance the wettability of Al on graphite with time without dewetting of the Al droplet. -- Abstract: Wettability of Al on Cu coated graphites and the interfacial reactions between Al and the Cu coating were analyzed to examine in depth the effect of the Cu coating layer used to enhance the wettability of Al on carbon. The wetting behaviors of Al according to Cu coating method and Cu thickness were also investigated. The Cu/Cu double layer coated by sputtering the Cu single layer coated by electroless plating because it improved the stability of the Cu layer coated on graphite at high temperature. In order to suppress the dewetting of Al on graphite and improve the wettability of Al on graphite, a thick Cu coating layer to supply sufficient Cu atoms for saturation in an Al droplet is needed.

Effects of Cu interlayer on the wettability of aluminum on carbon

International Nuclear Information System (INIS)

Ko, Young Jin; Yoon, Juil; Lee, Joonho; Han, Jun Hyun

2013-01-01

Highlights: •The enhancement of wettability of Al on the Cu-coated graphite was restricted by the dewetting of the Cu layer. •The pre-sputtering of Cu could enhanced the wettability of Al more than the Cu single layer coating using electroless plating. •A thick Cu coating layer is needed to enhance the wettability of Al on graphite with time without dewetting of the Al droplet. -- Abstract: Wettability of Al on Cu coated graphites and the interfacial reactions between Al and the Cu coating were analyzed to examine in depth the effect of the Cu coating layer used to enhance the wettability of Al on carbon. The wetting behaviors of Al according to Cu coating method and Cu thickness were also investigated. The Cu/Cu double layer coated by sputtering the Cu single layer coated by electroless plating because it improved the stability of the Cu layer coated on graphite at high temperature. In order to suppress the dewetting of Al on graphite and improve the wettability of Al on graphite, a thick Cu coating layer to supply sufficient Cu atoms for saturation in an Al droplet is needed

Ultrahigh stability of atomically thin metallic glasses

Energy Technology Data Exchange (ETDEWEB)

Cao, C. R.; Huang, K. Q.; Zhao, N. J.; Sun, Y. T.; Bai, H. Y.; Gu, L., E-mail: l.gu@iphy.ac.cn, E-mail: dzheng@iphy.ac.cn, E-mail: whw@iphy.ac.cn; Zheng, D. N., E-mail: l.gu@iphy.ac.cn, E-mail: dzheng@iphy.ac.cn, E-mail: whw@iphy.ac.cn; Wang, W. H., E-mail: l.gu@iphy.ac.cn, E-mail: dzheng@iphy.ac.cn, E-mail: whw@iphy.ac.cn [Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China)

2014-07-07

We report the fabrication and study of thermal stability of atomically thin ZrCu-based metallic glass films. The ultrathin films exhibit striking dynamic properties, ultrahigh thermal stability, and unique crystallization behavior with discrete crystalline nanoparticles sizes. The mechanisms for the remarkable high stability and crystallization behaviors are attributed to the dewetting process of the ultrathin film. We demonstrated a promising avenue for understanding some fundamental issues such as glassy structure, crystallization, deformation, and glass formation through atomic resolution imaging of the two dimensional like metallic glasses.

Due Process in Dual Process: Model-Recovery Simulations of Decision-Bound Strategy Analysis in Category Learning

Science.gov (United States)

Edmunds, Charlotte E. R.; Milton, Fraser; Wills, Andy J.

2018-01-01

Behavioral evidence for the COVIS dual-process model of category learning has been widely reported in over a hundred publications (Ashby & Valentin, 2016). It is generally accepted that the validity of such evidence depends on the accurate identification of individual participants' categorization strategies, a task that usually falls to…

Importance of layer thermal conductivity on the sharpness of patterns produced by laser interference

Energy Technology Data Exchange (ETDEWEB)

Peláez, R.J., E-mail: rpelaez@io.cfmac.csic.es [Laser Processing Group, Instituto de Optica, CSIC, Serrano 121, 28006 Madrid (Spain); Afonso, C.N. [Laser Processing Group, Instituto de Optica, CSIC, Serrano 121, 28006 Madrid (Spain); Škereň, M. [Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University in Prague, Brehova 7, 115 19 Prague 1 (Czech Republic); Bulíř, J. [Institute of Physics, ASCR, v.v.i., Na Slovance 2, Prague (Czech Republic)

2016-06-30

Highlights: • Temperature profile matches laser intensity profile in poor thermally conducting layers. • Patterns produced in poor thermally conducting layers have sharp interfaces. • Lateral heat flow smears the temperature profile in thermally conducting layers. • Both liquid and solid state dewetting occurs upon patterning thermally conducting layers. • The thermal conductivity of layers limits the minimum period achievable. - Abstract: In this work, we compare patterns produced in Ag layers having similar thickness in the range 8.3–10.8 nm but having different initial nanostructure, i.e. behaving either as discontinuous or continuous layers and thus having very different thermal conductivities. The patterns are produced by exposing a phase mask to an excimer laser operating at 193 nm and using a projection optics that leads to similar fringed patterns with periods in the range 6.3–6.7 μm. The layer breaks up into isolated NPs due to laser induced melting at the regions around the intensity maxima sites. The resulting fringes have sharp interfaces in the case of discontinuous layers while a variety of regions across the pattern with no sharp interfaces are produced in the case of continuous layers. The results show that while the temperature distribution across the pattern matches almost perfectly the laser beam intensity profile for the former case, it becomes smeared due to lateral heat flow for the latter case. These results provide evidences for significant heating at the intensity minima sites that lead to solid-state dewetting and will eventually limit the minimum period achievable in the case of continuous metal layers or thermally conducting layers.

Conformation-dependent DNA attraction.

Science.gov (United States)

Li, Weifeng; Nordenskiöld, Lars; Zhou, Ruhong; Mu, Yuguang

2014-06-21

Understanding how DNA molecules interact with other biomolecules is related to how they utilize their functions and is therefore critical for understanding their structure-function relationships. For a long time, the existence of Z-form DNA (a left-handed double helical version of DNA, instead of the common right-handed B-form) has puzzled the scientists, and the definitive biological significance of Z-DNA has not yet been clarified. In this study, the effects of DNA conformation in DNA-DNA interactions are explored by molecular dynamics simulations. Using umbrella sampling, we find that for both B- and Z-form DNA, surrounding Mg(2+) ions always exert themselves to screen the Coulomb repulsion between DNA phosphates, resulting in very weak attractive force. On the contrary, a tight and stable bound state is discovered for Z-DNA in the presence of Mg(2+) or Na(+), benefiting from their hydrophobic nature. Based on the contact surface and a dewetting process analysis, a two-stage binding process of Z-DNA is outlined: two Z-DNA first attract each other through charge screening and Mg(2+) bridges to phosphate groups in the same way as that of B-DNA, after which hydrophobic contacts of the deoxyribose groups are formed via a dewetting effect, resulting in stable attraction between two Z-DNA molecules. The highlighted hydrophobic nature of Z-DNA interaction from the current study may help to understand the biological functions of Z-DNA in gene transcription.

Amplitude growth due to random, correlated kicks

International Nuclear Information System (INIS)

Michelotti, L.; Mills, F.

1989-03-01

Historically, stochastic processes, such as gas scattering or stochastic cooling, have been treated by the Fokker-Planck equation. In this approach, usually considered for one dimension only, the equation can be considered as a continuity equation for a variable which would be a constant of the motion in the absence of the stochastic process, for example, the action variable, I = ε/2π for betatron oscillations, where ε is the area of the Courant-Snyder ellipse, or energy in the case of unbunched beams, or the action variable for phase oscillations in case the beam is bunched. A flux, /Phi/, including diffusive terms can be defined, usually to second order. /Phi/ = M 1 F(I) + M 2 ∂F/∂I + /hor ellipsis/. M 1 and M 2 are the expectation values of δI and (δI) 2 due to the individual stochastic kicks over some period of time, long enough that the variance of these quantities is sufficiently small. Then the Fokker-Planck equation is just ∂F/∂I + ∂/Phi//∂I = 0. In many cases those where the beam distribution has already achieved its final shape, it is sufficient to find the rate of increase of by taking simple averages over the Fokker-Planck equation. At the time this work was begun, there was good knowledge of the second moment for general stochastic processes due to stochastic cooling theory, but the form of the first moment was known only for extremely wideband processes. The purposes of this note are to derive an expression relating the expected single particle amplitude growth to the noise autocorrelation function and to obtain, thereby, the form of M 1 for narrow band processes. 4 refs

Measurement of the energetics of metal film growth on a semiconductor: Ag/ Si(100)-2x1

DEFF Research Database (Denmark)

Starr, D.E.; Ranney, J.T.; Larsen, Jane Hvolbæk

2001-01-01

The first direct calorimetric measurements of the energetics of metal film growth on a semiconductor surface are presented. The heat of adsorption of Ag on Si(100)-(2 x 1) at 300 K decreases from similar to 347 to 246 kJ/mol with coverage in the first monolayer (ML) due to overlap of substrate...... strain from nearby Ag islands. It then rises quickly toward the bulk sublimation enthalpy (285 kJ/mol) as 3D particles grow. A wetting layer grows to 1.0 ML, but is metastable above similar to0.55 ML and dewets when kinetics permit. This may be common when adsorbate islands induce a large strain...

Process-oriented dose assessment model for 14C due to releases during normal operation of a nuclear power plant

International Nuclear Information System (INIS)

Aquilonius, Karin; Hallberg, Bengt

2005-01-01

Swedish nuclear utility companies are required to assess doses due to releases of radionuclides during normal operation. In 2001, calculation methods used earlier were updated due to new authority regulations. The isotope 14 C is of special interest in dose assessments due to the role of carbon in the metabolism of all life forms. Earlier, factors expressing the ratio between concentration of 14 C in air and in various plants were used. In order to extend the possibility to take local conditions into account, a process-oriented assessment model for uptake of carbon and doses from releases of 14 C to air was developed (POM 14 C). The model uses part of Daisy which has been developed to model the turnover of carbon in crops. [Hansen, S., Jensen, H.E., Nielsen, N.E., Svendsen, H., 1993. Description of the Soil Plant System Model DAISY, Basic Principles and Modelling Approach. Simulation Model for Transformation and Transport of Energy and Matter in the Soil Plant Atmosphere System. Jordbruksfoerlaget, The Royal Veterianary and Agricultural University, Copenhagen, Denmark]. The main objectives were to test model performance of the former method, and to investigate if taking site specific parameters into account to a greater degree would lead to major differences in the results. Several exposure pathways were considered: direct consumption of locally grown cereals, vegetables, and root vegetables, as well as consumption of milk and meat from cows having eaten fodder cereals and green fodder from the area around the nuclear plant. The total dose of the earlier model was compared with that of POM 14 C. The result of the former was shown to be slightly higher than the latter, but POM 14 C confirmed that the earlier results were of a reasonable magnitude. When full account of local conditions was taken, e.g. as regards solar radiation, temperature, and concentration of 14 C in air at various places in the surroundings of each nuclear plant, a difference in dose between

Morphological, Structural and Optical Evolution of Ag Nanostructures on c-Plane GaN Through the Variation of Deposition Amount and Temperature

Science.gov (United States)

Sui, Mao; Li, Ming-Yu; Pandey, Puran; Zhang, Quanzhen; Kunwar, Sundar; Lee, Jihoon

2018-03-01

Owing to their tunable properties, Ag nanostructures have been widely adapted in various applications and the morphological control can determine their performance and effectiveness. In this work, we demonstrate the morphological and optical evolution of Ag nanostructures on GaN (0001) by the systematic control of deposition amount at two distinctive annealing temperatures. Based on the Volmer-Weber and coalescence growth models, the nanostructure growth commenced by the thermal solid-state-dewetting evolve in terms of size, density and configuration. At 450 °C, the round-dome shaped Ag nanoparticles (regime I), irregular Ag nano-mounds (regime II) and void-layer structures (regime III) are observed along with the gradually increased deposition amount. As a sharp distinction, the solid state dewetting process occur more radically at 700 °C and also, the Ag sublimation and the effect on the nanostructure formation are observed in a clear regime shift scaled by the deposition amount. Meanwhile, a strong dependency of reflectance spectra evolution on the Ag nanostructure morphology is witnessed for both sets. In particular, Ag dipolar resonance peaks are significantly red-shifted from VIS to NIR regions along with the nanostructure evolution. The reflectance, PL and Raman intensity variation are also observed and discussed based on the evolution of Ag nanostructures.

Exploring the return-to-work process for workers partially returned to work and partially on long-term sick leave due to common mental disorders : a qualitative study

NARCIS (Netherlands)

Noordik, Erik; Nieuwenhuijsen, Karen; Varekamp, Inge; van der Klink, Jac J.; van Dijk, Frank J.

2011-01-01

Purpose. We conducted a qualitative study into the return-to-work process of workers partially on sick leave due to common mental disorders. Our objectives were to describe the barriers to a full return to work, solutions, communicating to the working environment and the aim of a full return to

Due diligence

International Nuclear Information System (INIS)

Sanghera, G.S.

1999-01-01

The Occupational Health and Safety (OHS) Act requires that every employer shall ensure the health and safety of workers in the workplace. Issues regarding the practices at workplaces and how they should reflect the standards of due diligence were discussed. Due diligence was described as being the need for employers to identify hazards in the workplace and to take active steps to prevent workers from potentially dangerous incidents. The paper discussed various aspects of due diligence including policy, training, procedures, measurement and enforcement. The consequences of contravening the OHS Act were also described

Exploring the return-to-work process for workers partially returned to work and partially on long-term sick leave due to common mental disorders: a qualitative study

NARCIS (Netherlands)

Noordik, Erik; Nieuwenhuijsen, Karen; Varekamp, Inge; van der Klink, Jac J.; Van Dijk, Frank J.

2011-01-01

We conducted a qualitative study into the return-to-work process of workers partially on sick leave due to common mental disorders. Our objectives were to describe the barriers to a full return to work, solutions, communicating to the working environment and the aim of a full return to work, all as

A liquid-like model for the morphology evolution of ion bombarded thin films

Energy Technology Data Exchange (ETDEWEB)

Repetto, L., E-mail: luca.repetto@unige.it [Department of Physics and Nanomed Labs, Università di Genova, Via Dodecaneso 33, 16146 Genova (Italy); Lo Savio, R. [Department of Physics and Nanomed Labs, Università di Genova, Via Dodecaneso 33, 16146 Genova (Italy); Šetina Batič, B. [Inštitut Za Kovinske Materiale in Tehnologije, Lepi pot 11, 1000 Ljubljana (Slovenia); Firpo, G.; Angeli, E.; Valbusa, U. [Department of Physics and Nanomed Labs, Università di Genova, Via Dodecaneso 33, 16146 Genova (Italy)

2015-07-01

Thin solid films exposed to ion irradiation exhibit a peculiar evolution that can differ substantially from what is observed for bulk samples. The phenomenology of the patterns that self-organize on the substrate is very rich, with morphologies that display several degrees of order upon the modification of initial film characteristics and irradiation parameters. This richness paves the way for the fabrication of novel functional surfaces, but it is also an indication of the complexity of the underlying driving mechanisms. A remarkable simplification for the comprehension of these phenomena can come from the noteworthy similarity of the obtained patterns with those showing up when liquids dewet from their substrates. Here, we analyze the possibility to apply a liquid-like model to explain the morphology evolution of ion bombarded thin films for the whole phenomenology showing up in experiments. In establishing this connection between liquids and ion bombarded thin films, we propose to use also for liquids the insight gained for our system with recent experiments that stress the importance of the substrate topography for the selection of the dewetting mechanism. If confirmed, this result would lead to a reconsideration of the importance of capillary waves in spinodal dewetting, and will help to understand the low reproducibility of the related experimental results.

Presence and absence of a water film between moving air bubbles and a plate

International Nuclear Information System (INIS)

Remenyik, C.J.

1990-01-01

The thickness of water films between an inclined Lucite plate submerged in water and air bubbles moving beneath it was measured with a small impedance probe. The instrument was calibrated with a laser interferometer built for this purpose. The bubbles released beneath the plate varied in size from 10 cc to 100 cc. At a plate inclination angle of 0.98 degree, and in tap water, an uninterrupted water film covered most of the bubbles. Some bubbles, however, dewetted the plate, and the water film covered only a forward part of the bubble. When the film was uninterrupted, its thickness was very uniform from front to rear. When the bubble dewetted the plate, a large forward section of the film had the same uniform thickness, but this was followed by a hump on the film the rear slope of which ended at the plate surface. For some of the experiments, the surface tension of the water was reduced by admixing a detergent. In these experiments, dewetting was not observed. In a second set of experiments, a hand held transparent container filled with water and a 1.3 cm3 air bubble was used to observe visually the behavior of the moving bubble and its associated water film

Estimation of the Past and Future Infrastructure Damage Due the Permafrost Evolution Processes

Science.gov (United States)

Sergeev, D. O.; Chesnokova, I. V.; Morozova, A. V.

2015-12-01

The geocryological processes such as thermokarst, frost heaving and fracturing, icing, thermal erosion are the source of immediate danger for the structures. The economic losses during the construction procedures in the permafrost area are linked also with the other geological processes that have the specific character in cold regions. These processes are swamping, desertification, deflation, flooding, mudflows and landslides. Linear transport structures are most vulnerable component of regional and national economy. Because the high length the transport structures have to cross the landscapes with different permafrost conditions that have the different reaction to climate change. The climate warming is favorable for thermokarst and the frost heaving is linked with climate cooling. In result the structure falls in the circumstances that are not predicted in the construction project. Local engineering problems of structure exploitation lead to global risks of sustainable development of regions. Authors developed the database of geocryological damage cases for the last twelve years at the Russian territory. Spatial data have the attributive table that was filled by the published information from various permafrost conference proceedings. The preliminary GIS-analysis of gathered data showed the widespread territorial distribution of the cases of negative consequences of geocryological processes activity. The information about maximum effect from geocryological processes was validated by detailed field investigation along the railways in Yamal and Transbaicalia Regions. Authors expect the expanding of database by similar data from other sectors of Arctic. It is important for analyzing the regional, time and industrial tendencies of geocryological risk evolution. Obtained information could be used in insurance procedures and in information systems of decisions support in different management levels. The investigation was completed with financial support by Russian

The management of over closured anterior teeth due to attrition

OpenAIRE

Eha Djulaeha; Sukaedi Sukaedi

2009-01-01

Background: Tooth is the hardest tissue in human body, that can be injured because of attrition process. For old people, denture attrition process is caused by psysiological process relating with the mastication function which also supported by some bad habits such an bruxism, premature contact, and consuming habit of abrasive food. Attrition or abrasion can also be happened with patien’t dentition who does not have teeth subtutition for long time due the lost of their maxillary as well as ma...

A canned food scheduling problem with batch due date

Science.gov (United States)

Chung, Tsui-Ping; Liao, Ching-Jong; Smith, Milton

2014-09-01

This article considers a canned food scheduling problem where jobs are grouped into several batches. Jobs can be sent to the next operation only when all the jobs in the same batch have finished their processing, i.e. jobs in a batch, have a common due date. This batch due date problem is quite common in canned food factories, but there is no efficient heuristic to solve the problem. The problem can be formulated as an identical parallel machine problem with batch due date to minimize the total tardiness. Since the problem is NP hard, two heuristics are proposed to find the near-optimal solution. Computational results comparing the effectiveness and efficiency of the two proposed heuristics with an existing heuristic are reported and discussed.

Manufacturing of polymer optical waveguides using self-assembly effect on pre-conditioned 3D-thermoformed flexible substrates

Science.gov (United States)

Hoffmann, Gerd-Albert; Wolfer, Tim; Zeitler, Jochen; Franke, Jörg; Suttmann, Oliver; Overmeyer, Ludger

2017-02-01

Optical data communication is increasingly interesting for many applications in industrial processes. Therefore mass production is required to meet the requested price and lot sizes. Polymer optical waveguides show great promises to comply with price requirements while providing sufficient optical quality for short range data transmission. A high efficient fabrication technology using polymer materials could be able to create the essential backbone for 3D-optical data transmission in the future. The approach for high efficient fabrication technology of micro optics described in this paper is based on a self-assembly effect of fluids on preconditioned 3D-thermoformed polymer foils. Adjusting the surface energy on certain areas on the flexible substrate by flexographic printing mechanism is presented in this paper. With this technique conditioning lines made of silicone containing UV-varnish are printed on top of the foils and create gaps with the exposed substrate material in between. Subsequent fabrication processes are selected whether the preconditioned foil is coated with acrylate containing waveguide material prior or after the thermoforming process. Due to the different surface energy this material tends to dewet from the conditioning lines. It acts like regional barriers and sets the width of the arising waveguides. With this fabrication technology it is possible to produce multiple waveguides with a single coating process. The relevant printing process parameters that affect the quality of the generated waveguides are discussed and results of the produced waveguides with width ranging from 10 to 300 μm are shown.

Numerical simulation of baseflow modification due to effects of ...

African Journals Online (AJOL)

Numerical simulation of baseflow modification due to effects of sediment yield. ... Physically-based mathematical modelling affords the opportunity to look at this kind of interaction, which should be simulated by deterministic responses of both water and fluvial processes. In addition to simulating the streamflow and ...

4-Amino-1,2,4-triazole: Playing a key role in the chemical deposition of Cu-In-Ga metal layers for photovoltaic applications

Energy Technology Data Exchange (ETDEWEB)

Berner, Ulrich, E-mail: ulrich.berner@de.bosch.com [Robert Bosch GmbH, Corporate Sector Research and Advance Engineering, Applied Research Chemistry (CR/ARC), Robert Bosch Platz 1, 70839 Gerlingen-Schillerhöhe (Germany); Physics and Materials Science Research Unit, Université du Luxembourg, 41, rue du Brill, L-4422 Belvaux (Luxembourg); Widenmeyer, Markus; Engler, Patrick [Robert Bosch GmbH, Corporate Sector Research and Advance Engineering, Applied Research Chemistry (CR/ARC), Robert Bosch Platz 1, 70839 Gerlingen-Schillerhöhe (Germany); Dale, Phillip J. [Physics and Materials Science Research Unit, Université du Luxembourg, 41, rue du Brill, L-4422 Belvaux (Luxembourg)

2015-05-01

Liquid film processing of Cu(In,Ga)Se{sub 2} absorber layers has the potential to lower the cell production costs significantly namely because of the absence of vacuum steps and high material utilization. In this work an ink system based on metal carboxylates in a mixture of a nitrogen-containing base and an alcohol is investigated. After the coating step on a suitable substrate followed by the drying of the alcohol, the metal ions are reduced to the respective metals with a simple heat treatment. However, depending on the conditions, the resulting metal layers are either highly porous or dewetting above 160 °C due to the high surface tension of the intermediate liquid indium. Adding 4-amino-1,2,4-triazole to the ink leads to a homogeneous metal layer, which is crucial for the formation of dense chalcopyrite layers. We propose a stabilization mechanism based on a temporary polymeric complex of Cu{sup 2+} and the additive 4-amino-1,2,4-triazole which is decomposing completely at selenization conditions. - Highlights: • Influence of 4-amino-1,2,4-triazole on the film formation has been investigated. • Two polymers identified forming an organic matrix during the layer processing • This matrix allows processing of dense and crack free metallic layers. • The polymers decompose completely under selenization conditions.

Plasmonic response and transformation mechanism upon single laser exposure of metal discontinuous films

Energy Technology Data Exchange (ETDEWEB)

Rodríguez, C.E. [Laser Processing Group, Instituto de Óptica, CSIC, Serrano 121, 28006 Madrid (Spain); Peláez, R.J., E-mail: rpelaez@io.cfmac.csic.es [Laser Processing Group, Instituto de Óptica, CSIC, Serrano 121, 28006 Madrid (Spain); Afonso, C.N. [Laser Processing Group, Instituto de Óptica, CSIC, Serrano 121, 28006 Madrid (Spain); Riedel, S.; Leiderer, P. [Faculty of Physics, University of Konstanz, Universitätsstraße 10, 78457 Konstanz (Germany); Jimenez-Rey, D.; Font, A. Climent- [Centro de Micro-Análisis de Materiales (CMAM) and Departamento de Física Aplicada, University Autonoma Madrid, 28049 Madrid (Spain)

2014-05-01

Ag and Au discontinuous films were exposed to single nanosecond pulses of a homogenized beam of an excimer laser operating at 193 nm. For low fluences, the films convert into big, almost spherical and isolated nanoparticles (NPs) due to laser-induced dewetting. Their optical response exhibits a sharp surface plasmon resonance (SPR) consistent with that of spherical and non-interacting NPs. For higher fluences, the formation of many small NPs and almost no big NPs is observed instead. The SPR features change and the plasmonic response becomes influenced by multipolar interactions among neighbouring NPs. Low and high fluence regimes are respectively related to melting and boiling threshold of the metal, and additionally, craters appear in the latter regime.

Radiocontamination of agricultural workers due to nuclear accidents

International Nuclear Information System (INIS)

Petrovic, B.; Smelcerovic, M.; Djuric, G.; Popovic, D.

1989-01-01

In the radiocontamination of the environment due to nuclear accidents, agricultural workers should be considered as a critical group of population. The presented paper discusses this problem from the aspects of folder production. The values of the effective dose equivalent are estimated for different phases of the production process and certain procedures aimed to reduce the radiation risk are proposed (author)

Radiocontamination of agricultural workers due to nuclear accidents

Energy Technology Data Exchange (ETDEWEB)

Petrovic, B [Faculty of Veterinary Medicine, Beograd, (Serbia and Montenegro); Smelcerovic, M; Djuric, G; Popovic, D [Institute of Nuclear Sciences Boris Kidric, Vinca, Beograd (Serbia and Montenegro)

1989-07-01

In the radiocontamination of the environment due to nuclear accidents, agricultural workers should be considered as a critical group of population. The presented paper discusses this problem from the aspects of folder production. The values of the effective dose equivalent are estimated for different phases of the production process and certain procedures aimed to reduce the radiation risk are proposed (author)

A theoretical approach to sputtering due to molecular ion bombardment, 1

International Nuclear Information System (INIS)

Karashima, Shosuke; Ootoshi, Tsukuru; Kamiyama, Masahide; Kim, Pil-Hyon; Namba, Susumu.

1981-01-01

A shock wave model is proposed to explain theoretically the non-linear effects in sputtering phenomena by molecular ion bombardments. In this theory the sputtering processes are separated into two parts; one is due to linear effects and another is due to non-linear effects. The treatment of the linear parts is based on the statistical model by Schwarz and Helms concerning a broad range of atomic collision cascades. The non-linear parts are treated by the model of shock wave due to overlapping cascades, and useful equations to calculate the sputtering yields and the dynamical quantities in the system are derived. (author)

The effect of growth temperature variation on partially bismuth filled carbon nanotubes synthesis using a soft semi-metallic template.

Science.gov (United States)

Sahoo, R K; Jacob, C

2014-06-01

The dewetting of a low melting point metal thin film deposited on silicon substrates was studied. The experimental results suggest that the change in the growth temperature affects the nanostructures that form. Based on the experimental results, the temperature which yielded the smallest features for the growth of nanotubes is determined. The mechanism by which these nano-templates become an efficient seeds for the growth of the carbon nanotubes is discussed. The partial bismuth filling inside the CNTs was optimized. Based on the results, a schematic growth model for better understanding of the process parameters has also been proposed.

Fabrication and characteristics of self-assembly nano-polystyrene films by laser induced CVD

Energy Technology Data Exchange (ETDEWEB)

Xiao, Tingting [Department of Applied Physics, Chongqing University, Chongqing 401331 (China); Science and Technology on Plasma Physics Laboratory, Research Center of Laser Fusion, CAEP, Mianyang 621900 (China); Cai, Congzhong [Department of Applied Physics, Chongqing University, Chongqing 401331 (China); Peng, Liping [Science and Technology on Plasma Physics Laboratory, Research Center of Laser Fusion, CAEP, Mianyang 621900 (China); Wu, Weidong, E-mail: wuweidongding@163.com [Science and Technology on Plasma Physics Laboratory, Research Center of Laser Fusion, CAEP, Mianyang 621900 (China)

2013-10-01

The self-assembly nano-polystyrene (PS) films have been prepared by laser induced CVD at room temperature. The XPS, Raman and UV–vis absorption spectra all indicated that the films were PS. The optical properties, microstructure and controllable nanostructure of PS films have been investigated. Dewetting-like microstructure in PS films was investigated and uniform island structures with a diameter of about 200 nm were observed at the deposition pressure of 14 Pa. The films possess good toughness and precisely controlled thicknesses. The free-standing PS films with thickness of 10 nm could be obtained by this method though a series of process.

Nano-electron beam induced current and hole charge dynamics through uncapped Ge nanocrystals

Energy Technology Data Exchange (ETDEWEB)

Marchand, A.; El Hdiy, A.; Troyon, M. [Laboratoire de Recherche en Nanosciences, Bat. 6, case no 15, UFR Sciences, Universite de Reims Champagne Ardenne, 51687 Reims Cedex 2 (France); Amiard, G.; Ronda, A.; Berbezier, I. [IM2NP, Faculte des Sciences et Techniques, Campus de Saint Jerome - Case 142, Avenue Escadrille Normandie Niemen, 13397 Marseille Cedex 20 (France)

2012-04-16

Dynamics of hole storage in spherical Ge nanocrystals (NCs) formed by a two step dewetting/nucleation process on an oxide layer grown on an n-doped <001> silicon substrate is studied using a nano-electron beam induced current technique. Carrier generation is produced by an electron beam irradiation. The generated current is collected by an atomic force microscope--tip in contact mode at a fixed position away from the beam spot of about 0.5 {mu}m. This distance represents the effective diffusion length of holes. The time constants of holes charging are determined and the effect of the NC size is underlined.

Fabrication of Ternary AgPdAu Alloy Nanoparticles on c-Plane Sapphire by the Systematical Control of Film Thickness and Deposition Sequence

Science.gov (United States)

Kunwar, Sundar; Pandey, Puran; Sui, Mao; Bastola, Sushil; Lee, Jihoon

2018-06-01

In this work, a systematic study on the fabrication of ternary AgPdAu alloy nanoparticles (NPs) on c-plane sapphire (0001) is presented and the corresponding structural and optical characteristics are demonstrated. The metallic trilayers of various thicknesses and deposition orders are annealed in a controlled manner (400 °C to 900 °C) to induce the solid-state dewetting that yields the various structural configurations of AgPdAu alloy NPs. The dewetting of relatively thicker trilayers (15 nm) is gradually progressed with void nucleation, growth, and coalescence, isolated NP formation, and shape transformation, along with the temperature control. For 6 nm thickness, owing to the sufficient dewetting of trilayers along with enhanced diffusion, dense and small spherical alloy NPs are fabricated. Depending on the specific growth condition, the surface diffusion and interdiffusion of metal atoms, surface and interface energy minimization, Rayleigh instability, and equilibrium configuration are correlated to describe the fabrication of ternary alloy NPs. Ternary alloy NPs exhibit morphology-dependent ultraviolet-visible-near infrared (UV-VIS-NIR) reflectance properties such as the inverse relationship of average reflectance with the surface coverage, absorption enhancement in specific regions, and reflectance maxima in UV and NIR regions. In addition, Raman spectra depict the six active phonon modes of sapphires and their intensity and position modulation by the alloy NPs.

The equilibrium crystal shape of nickel

International Nuclear Information System (INIS)

Meltzman, Hila; Chatain, Dominique; Avizemer, Dan; Besmann, Theodore M.; Kaplan, Wayne D.

2011-01-01

Highlights: → The ECS of pure Ni is completely facetted with both dense and high-index planes. → The partial pressure of oxygen has a significant effect on the surface anisotropy. → The addition of Fe decreased the anisotropy and de-stabilized high-index planes. → During solid dewetting nucleation barriers prevent equilibration of the top facet. - Abstract: The crystal shape of Ni particles, dewetted in the solid state on sapphire substrates, was examined as a function of the partial pressure of oxygen (P(O 2 )) and iron content using scanning and transmission electron microscopy. The chemical composition of the surface was characterized by atom-probe tomography. Unlike other face-centered cubic (fcc) equilibrium crystal shapes, the Ni crystals containing little or no impurities exhibited a faceted shape, indicating large surface anisotropy. In addition to the {1 1 1}, {1 0 0} and {1 1 0} facets, which are usually present in the equilibrium crystal shape of fcc metals, high-index facets were identified such as {1 3 5} and {1 3 8} at low P(O 2 ), and {0 1 2} and {0 1 3} at higher P(O 2 ). The presence of iron altered the crystal shape into a truncated sphere with only facets parallel to denser planes. The issue of particle equilibration is discussed specifically for the case of solid-state dewetting.

Engineering the size and density of silicon agglomerates by controlling the initial surface carbonated contamination

Energy Technology Data Exchange (ETDEWEB)

Borowik, Ł., E-mail: Lukasz.Borowik@cea.fr [CEA, LETI, MINATEC Campus, 17 rue des Martyrs, 38054 Grenoble Cedex 9 (France); Chevalier, N.; Mariolle, D.; Martinez, E.; Bertin, F.; Chabli, A.; Barbé, J.-C. [CEA, LETI, MINATEC Campus, 17 rue des Martyrs, 38054 Grenoble Cedex 9 (France)

2013-04-01

Actually, thermally induced thin-films dewetting silicon in the silicon-on-insulator is a way to obtain silicon agglomerates with a size and a density fixed by the silicon film thickness. In this paper we report a new method to monitor both the size and the density of the Si agglomerates thanks to the deposition of a carbon-like layer. We show that using a 5-nm thick layer of silicon and additional ≤1-nm carbonated layer; we obtain agglomerates sizes ranging from 35 nm to 60 nm with respectively an agglomerate density ranging from 38 μm{sup −2} to 18 μm{sup −2}. Additionally, for the case of strained silicon films an alternative dewetting mechanism can be induced by monitoring the chemical composition of the sample surface.

Challenges in the Structure Determination of Self-Assembled Metallacages: What Do Cage Cavities Contain, Internal Vapor Bubbles or Solvent and/or Counterions?

Czech Academy of Sciences Publication Activity Database

Givelet, C. C.; Dron, P. I.; Wen, J.; Magnera, T. F.; Zamadar, M.; Čépe, K.; Fujiwara, H.; Shi, Y.; Tuchband, M. R.; Clark, N.; Zbořil, R.; Michl, Josef

2016-01-01

Roč. 138, č. 20 (2016), s. 6676-6687 ISSN 0002-7863 Institutional support: RVO:61388963 Keywords : capillary evaporation * dewetting transition * computer simulation Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 13.858, year: 2016

ANALYSIS OF FINANCIAL DUE DILIGENCE UNSUCCESSFUL BUSINESS COMPANIES IN SERBIA

Directory of Open Access Journals (Sweden)

JELENA Toskovic

2015-06-01

Full Text Available In conditions of extreme financial and corporate scandals, in order to achieve a good position in the market and thus maximize profit, modern companies and their top managers must make continual innovation and change, as an adaptation of one of the basic imperatives of modern business. This means that today's modern enterprises are facing numerous challenges, including the need to find a way to survival, growth and development. The global economic crisis that occurred in 2007 passed the downfall of many companies and put into focus the creative application of financial resources in the process of bankruptcy. Each company during its life cycle comes to a situation that is found in some form of crisis, but if it fails to overcome the crisis inevitably is to declare bankruptcy, which is a recognition that the company failed to meet its objectives. The causes of business failure are different, so the task of the financial due diligence to do the recording of enterprises, carefully, systematically and thoroughly investigate, examine and analyze them information company that filed for bankruptcy. The point of introduction of due diligence is in providing input as soon as possible, in order to take advantage of information in the right way and made the right decisions and strategies of the business. So due diligence serves as a tool or vehicle for designing business decisions, which is in the territory of the Republic of Serbia still minimal use. The reorganization process is applied rather than the liquidation process, precisely in order to use all the resources that the company has, and thus protect shareholders, creditors and suppliers. This process is strictly controlled and regularized to avoid possible abuse by management that led the company to bankruptcy. The legislation allows considerable benefits company in the reorganization process, just to fit in a healthy leg, changed unsuccessful business and financial structure of the successful and

Spiritual Occlusion and Systemic Integrity: Legal Evaluations of Due Process Protections and Freedom of Religious Expression and Practices Safeguards

Directory of Open Access Journals (Sweden)

Jason R. Jolicoeur

2018-05-01

Full Text Available As is the case with other constitutionally protected rights, the freedom of religion is not unlimited nor without restriction or constraint. Rather, the courts have long held that the state may have legitimate reasons for placing reasonable restrictions on the otherwise free exercise of religious practice. The courts have also held that the state cannot restrict religious practice in a capricious or gratuitous manner. However, the courts have also held that individuals have a constitutional right to due process legal protections. In many instances, these two freedoms exist independently of each other. In instances when they intersect, conflict may result from one right seeking hegemony over the other. In instances such as these, the courts may have to resolve conflicts by establishing legal principles and precedents regarding which of these constitutional protections will be granted contextual prominence over the other. Thus far, the legal evaluation of this important question has been confused at best and contradictory at worst. This has resulted in a number of substantive outcomes that pose significant challenges to the practice and application of both rights and an underlying avoidance of broader constitutional questions.

Finančné due diligence: teória a prax pri M&A transakciách

OpenAIRE

Vavrovič, Maroš

2015-01-01

This thesis focuses on financial due diligence within M&A transactions. In the first part, due diligence is characterized as one of the main factors of M&A failure. Due diligence process and definition is described afterwards, as well as purpose of due diligence, various types of due diligence and position of due diligence within individual phases of M&A transaction. Furthermore, financial due diligence and its main principles are defined. Essential differences between financial due diligence...

Coffee-Ring Defined Short Channels for Inkjet-Printed Metal Oxide Thin-Film Transistors.

Science.gov (United States)

Li, Yuzhi; Lan, Linfeng; Xiao, Peng; Sun, Sheng; Lin, Zhenguo; Song, Wei; Song, Erlong; Gao, Peixiong; Wu, Weijing; Peng, Junbiao

2016-08-03

Short-channel electronic devices several micrometers in length are difficult to implement by direct inkjet printing due to the limitation of position accuracy of the common inkjet printer system and the spread of functional ink on substrates. In this report, metal oxide thin-film transistors (TFTs) with channel lengths of 3.5 ± 0.7 μm were successfully fabricated with a common inkjet printer without any photolithography steps. Hydrophobic CYTOP coffee stripes, made by inkjet-printing and plasma-treating processes, were utilized to define the channel area of TFTs with channel lengths as short as ∼3.5 μm by dewetting the inks of the source/drain (S/D) precursors. Furthermore, by introduction of an ultrathin layer of PVA to modify the S/D surfaces, the spreading of precursor ink of the InOx semiconductor layer was well-controlled. The inkjet-printed short-channel TFTs exhibited a maximum mobility of 4.9 cm(2) V(-1) s(-1) and an on/off ratio of larger than 10(9). This approach of fabricating short-channel TFTs by inkjet printing will promote the large-area fabrication of short-channel TFTs in a cost-effective manner.

Evaluation of consequence due to higher hydrazine content in partitioning stream of PUREX process

Energy Technology Data Exchange (ETDEWEB)

Kumar, K. Suresh [Bhabha Atomic Research Centre, Mumbai (India). Special Nuclear Recycle Facility

2016-07-01

Hydrazine nitrate is being used as a stabilizer for U(IV) as well as Pu(III) during partitioning of Pu in PUREX process by scavenging the nitrous acid present along with nitric acid. As hydrazine hydrate as well as its salts have been successfully used for scrubbing of degradation products of TBP to aqueous phase, experiments were conducted to evaluate the consequence of hydrazine content during Pu partitioning. It was observed that higher amount of hydrazine nitrate along with uranous nitrate in the partitioning stream of PUREX process leads to build up of DBP in aqueous phase and resulted in precipitation of Pu.

Due date assignment procedures with dynamically updated coefficients for multi-level assembly job shops

NARCIS (Netherlands)

Adam, N.R.; Bertrand, J.W.M.; Morehead, D.C.; Surkis, J.

1993-01-01

This paper presents a study of due date assignment procedures in job shop environments where multi-level assembly jobs are processed and due dates are internally assigned. Most of the reported studies in the literature have focused on string type jobs. We propose a dynamic update approach (which

Ground movement and deformation due to dewatering and open pit excavation

International Nuclear Information System (INIS)

Liu, B.; Yang, J.; Zhang, J.

1996-01-01

In the application of stochastic medium theory, it is assumed that ground movement process has the property of Markov Process. Based on superposition principle and rock consolidation principle, the ground movement and deformation due to dewatering and open pit excavation can be calculated. The comparison between the field measurements in Morwell Open Pit, Latrobe Valley (Victoria, Australia) and the calculated results shows the validity of the method in this paper. 5 refs

Period dependence of laser induced patterns in metal films

Czech Academy of Sciences Publication Activity Database

Peláez, R.J.; Afonso, C.N.; Škereň, M.; Bulíř, Jiří

2015-01-01

Roč. 26, č. 1 (2015), 1-11 ISSN 0957-4484 Institutional support: RVO:68378271 Keywords : patterning * nanoparticles * thin films * silver * laser interference * dewetting Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.573, year: 2015

Law n. 13.015/2014: Amendment of Labor Magazine Feature and Possible offenses to Constitutional Principles of Due Process Legal Access to Jurisdiction and Effectiveness

Directory of Open Access Journals (Sweden)

Sérgio Henriques Zandona Freitas

2015-12-01

Full Text Available This scientific article aims to study the reforms undertaken by the Law 13.015/2014 under the proposed amendments to the labor resources of magazines, and a growing demand in the edition of overviews by the Regionals Labors Court. At first, the theoretical basis, we analyze the prospects of the constitutional process model within the framework leveraged as a democratic state. After, it enters to the principle concept of due process of law, the access Jurisdiction and Effectiveness, doing, in a third moment, a brief survey and survey as the main proposals of changes made by Law n. 13.015/2014, demonstrating the likelihood that some provisions of this standard or not contradict principles and constitutional guarantees. Trough the deductive method and the bibliographic research this article has been written from a large conception to a small one. And as technical proceeding were used the theme analysis as a way of looking for a solution for the problem.

34 CFR 602.25 - Due process.

Science.gov (United States)

2010-07-01

... before an appeals panel that— (i) May not include current members of the agency's decision-making body... significance and materiality are determined by the agency. (iii) The only remaining deficiency cited by the...

The Drone Court And Due Process

Science.gov (United States)

2016-12-01

authority, even during wartime, when it heard Youngstown Tube and Sheet Co. v. Sawyer.68 In 1951, when the United States went to war with Korea , labor...national origin, religion , alienage, and poverty.” See “Strict Scrutiny,” Legal Information Institute, accessed December 9, 2016, https

Ordered arrays of nanoporous gold nanoparticles

Directory of Open Access Journals (Sweden)

Dong Wang

2012-09-01

Full Text Available A combination of a “top-down” approach (substrate-conformal imprint lithography and two “bottom-up” approaches (dewetting and dealloying enables fabrication of perfectly ordered 2-dimensional arrays of nanoporous gold nanoparticles. The dewetting of Au/Ag bilayers on the periodically prepatterned substrates leads to the interdiffusion of Au and Ag and the formation of an array of Au–Ag alloy nanoparticles. The array of alloy nanoparticles is transformed into an array of nanoporous gold nanoparticles by a following dealloying step. Large areas of this new type of material arrangement can be realized with this technique. In addition, this technique allows for the control of particle size, particle spacing, and ligament size (or pore size by varying the period of the structure, total metal layer thickness, and the thickness ratio of the as-deposited bilayers.

Formation of GaAs/AlGaAs and InGaAs/GaAs nanorings by droplet molecular-beam epitaxy

International Nuclear Information System (INIS)

Gong, Z.; Niu, Z.C.; Huang, S.S.; Fang, Z.D.; Sun, B.Q.; Xia, J.B.

2005-01-01

GaAs/AlGaAs lattice-matched nanorings are formed on GaAs (100) substrates by droplet epitaxy. The crucial step in the formation of nanorings is annealing Ga droplets under As flux for proper time. The observed morphologic evolution of Ga droplets during annealing does not support the hypothesis that As atoms preferentially react with Ga around the periphery of the droplets, but somehow relates to a dewetting process similar to that of unstable films. Photoluminescene (PL) test results confirm the quantum-confinement effect of these GaAs nanorings. Using similar methods, we have fabricated InGaAs/GaAs lattice-mismatched rings

Method of removing clogging materials due to ruthenium precipitates and sealing them in device

International Nuclear Information System (INIS)

Hoshikawa, Tadahiro; Sasahira, Akira.

1994-01-01

In a facility, such as a reprocessing facility, for processing a solution containing a great amount of ruthenium, precipitates due to evaporated ruthenium and cooled NO x are brought into contact with each other to decompose the precipitates due to the evaporated ruthenium. Precipitates due to ruthenium evaporated from the solution are reacted with cooled NO x , and the precipitates of ruthenium are decomposed and returned to the solution in the form of extremely fine particles together with recycling flow from the inner wall of the device. Since the precipitates of ruthenium returned to the solution are stable, they are no more evaporated and precipitated on the inner wall of the device. In the solution processing device having a possibility of clogging, clogging can be prevented and the precipitates of ruthenium can be sealed by decomposing them. (T.M.)

Air pollution due to road traffic in Ljubljana

Directory of Open Access Journals (Sweden)

Matej Ogrin

2007-01-01

Full Text Available Air pollution is due to road traffic an inevitable outcome of internal combustion in engines ofvehicles and some other processes. Air near the roads is more polluted with some pollutants,such as carbon monoxide, nitrogen oxides, ozone, particulate matter and some others.Monitoring the air quality is a key issue, when one wants to estimate environmental impactsof the road traffic. The article shows a method of passive samplers for air quality monitoringalong different roads in the area of Ljubljana Municipality.

Synthesis, fractionation, and thin film processing of nanoparticles using the tunable solvent properties of carbon dioxide gas expanded liquids

Science.gov (United States)

Anand, Madhu

Nanoparticles have received significant attention because of their unusual characteristics including high surface area to volume ratios. Materials built from nanoparticles possess unique chemical, physical, mechanical and optical properties. Due to these properties, they hold potential in application areas such as catalysts, sensors, semiconductors and optics. At the same time, CO 2 in the form of supercritical fluid or CO2 gas-expanded liquid mixtures has gained significant attention in the area of processing nanostructures. This dissertation focuses on the synthesis and processing of nanoparticles using CO2 tunable solvent systems. Nanoparticle properties depend heavily on their size and, as such, the ability to finely control the size and uniformity of nanoparticles is of utmost importance. Solution based nanoparticle formation techniques are attractive due to their simplicity, but they often result in the synthesis of particles with a wide size range. To address this limitation, a post-synthesis technique has been developed in this dissertation to fractionate polydisperse nanoparticles ( s . = 30%) into monodisperse fractions ( s . = 8%) using tunable physicochemical properties of CO 2 expanded liquids, where CO2 is employed as an antisolvent. This work demonstrates that by controlling the addition of CO2 (pressurization) to an organic dispersion of nanoparticles, the ligand stabilized nanoparticles can be size selectively precipitated within a novel high pressure apparatus that confines the particle precipitation to a specified location on a surface. Unlike current techniques, this CO2 expanded liquid approach provides faster and more efficient particle size separation, reduction in organic solvent usage, and pressure tunable size selection in a single process. To improve our fundamental understanding and to further refine the size separation process, a detailed study has been performed to identify the key parameters enabling size separation of various

Antireflective glass nanoholes on optical lenses.

Science.gov (United States)

Lee, Youngseop; Bae, Sang-In; Eom, Jaehyeon; Suh, Ho-Cheol; Jeong, Ki-Hun

2018-05-28

Antireflective structures, inspired from moth eyes, are still reserved for practical use due to their large-area nanofabrication and mechanical stability. Here we report an antireflective optical lens with large-area glass nanoholes. The nanoholes increase light transmission due to the antireflective effect, depending on geometric parameters such as fill factor and height. The glass nanoholes of low effective refractive index are achieved by using solid-state dewetting of ultrathin silver film, reactive ion etching, and wet etching. An ultrathin silver film is transformed into nanoholes for an etch mask in reactive ion etching after thermal annealing at a low temperature. Unlike conventional nanopillars, nanoholes exhibit high light transmittance with enhancement of ~4% over the full visible range as well as high mechanical hardness. Also, an antireflective glass lens is achieved by directly employing nanoholes on the lens surface. Glass nanoholes of highly enhanced optical and mechanical performance can be directly utilized for commercial glass lenses in various imaging and lighting applications.

Rapid growth of single-layer graphene on the insulating substrates by thermal CVD

Energy Technology Data Exchange (ETDEWEB)

Chen, C.Y. [Faculty of Materials Science and Engineering, Kunming University of Science and Technology, Kunming 650093 (China); Key Laboratory of Marine Materials and Related Technologies, Zhejiang Key Laboratory of Marine Materials and Protective Technologies, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Dai, D.; Chen, G.X.; Yu, J.H. [Key Laboratory of Marine Materials and Related Technologies, Zhejiang Key Laboratory of Marine Materials and Protective Technologies, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Nishimura, K. [Key Laboratory of Marine Materials and Related Technologies, Zhejiang Key Laboratory of Marine Materials and Protective Technologies, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Advanced Nano-processing Engineering Lab, Mechanical Systems Engineering, Kogakuin University (Japan); Lin, C.-T. [Key Laboratory of Marine Materials and Related Technologies, Zhejiang Key Laboratory of Marine Materials and Protective Technologies, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Jiang, N., E-mail: jiangnan@nimte.ac.cn [Key Laboratory of Marine Materials and Related Technologies, Zhejiang Key Laboratory of Marine Materials and Protective Technologies, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Zhan, Z.L., E-mail: zl_zhan@sohu.com [Faculty of Materials Science and Engineering, Kunming University of Science and Technology, Kunming 650093 (China)

2015-08-15

Highlights: • A rapid thermal CVD process has been developed to directly grow graphene on the insulating substrates. • The treating time consumed is ≈25% compared to conventional CVD procedure. • Single-layer and few-layer graphene can be formed on quartz and SiO{sub 2}/Si substrates, respectively. • The formation of thinner graphene at the interface is due to the fast precipitation rate of carbon atoms during cooling. - Abstract: The advance of CVD technique to directly grow graphene on the insulating substrates is particularly significant for further device fabrication. As graphene is catalytically grown on metal foils, the degradation of the sample properties is unavoidable during transfer of graphene on the dielectric layer. Moreover, shortening the treatment time as possible, while achieving single-layer growth of graphene, is worthy to be investigated for promoting the efficiency of mass production. Here we performed a rapid heating/cooling process to grow graphene films directly on the insulating substrates by thermal CVD. The treating time consumed is ≈25% compared to conventional CVD procedure. In addition, we found that high-quality, single-layer graphene can be formed on quartz, but on SiO{sub 2}/Si substrate only few-layer graphene can be obtained. The pronounced substrate effect is attributed to the different dewetting behavior of Ni films on the both substrates at 950 °C.

Broadband generation by multiple four-wave mixing process due to ASE Q-switching in high-power double-clad ytterbium-doped fiber amplifier

Science.gov (United States)

Chowdhury, Sourav D.; Shekhar, Nishant; Saha, Maitreyee; Sen, Ranjan; Pal, Mrinmay

2014-11-01

Broadband output from 1060nm to 1700nm and cascaded four-wave mixing generated red light pulsing is observed in a fiber amplifier set up consisting of a 5.5m double clad, double D shaped Ytterbium doped fiber, a single clad passive fiber for excess pump absorption and a splitter, both with and without a CW seed. Self-pulsing occurs from ASE due to passive Q-switching by saturable absorption effect of the active fiber and also depends on splice loss. The pulses generate broadband output by multiple four-wave mixing process with maximum broadening efficiency near 1300nm which is the zero dispersion wavelength for silica fiber. Pulses traveling both in forward and backward direction have enough peak power and energy to damage splice points and fiber components. When seeded the self-pulsing and broadband generation is often suppressed but again generate at increased pump powers.

Cracking in reinforced concrete structures due to imposed deformations

Energy Technology Data Exchange (ETDEWEB)

Nagy, A.

1997-04-01

This thesis is concerned with modeling of the cracking process in reinforced concrete due to imposed deformations. Cracking is investigated both at early ages, during hydration, and at mature age when the final properties of the concrete are reached. One of the most important material characteristics of the concrete at early ages, the Young`s modulus is determined by means of a dynamic method called the resonance frequency method. 40 refs

Ambiance-dependent agglomeration and surface-enhanced Raman spectroscopy response of self-assembled silver nanoparticles for plasmonic photovoltaic devices

Science.gov (United States)

Gwamuri, Jephias; Venkatesan, Ragavendran; Sadatgol, Mehdi; Mayandi, Jeyanthinath; Guney, Durdu O.; Pearce, Joshua M.

2017-07-01

The agglomeration/dewetting process of thin silver films provides a scalable method of obtaining self-assembled nanoparticles (SANPs) for plasmonics-based thin-film solar photovoltaic (PV) devices. We show the effect of annealing ambiance on silver SANP average size, particle/cluster finite shape, substrate area coverage/particle distribution, and how these physical parameters influence optical properties and surface-enhanced Raman scattering (SERS) responses of SANPs. Statistical analysis performed indicates that generally Ag SANPs processed in the presence of a gas (argon and nitrogen) ambiance tend to have smaller average size particles compared to those processed under vacuum. Optical properties are observed to be highly dependent on particle size, separation distance, and finite shape. The greatest SERS enhancement was observed for the argon-processed samples. There is a correlation between simulation and experimental data that indicate argon-processed AgNPs have a great potential to enhance light coupling when integrated to thin-film PV.

Novel self-organization mechanism in ultrathin liquid films: theory and experiment.

Science.gov (United States)

Trice, Justin; Favazza, Christopher; Thomas, Dennis; Garcia, Hernando; Kalyanaraman, Ramki; Sureshkumar, Radhakrishna

2008-07-04

When an ultrathin metal film of thickness h (h*, in contrast to the classical spinodal dewetting behavior where Lambda increases monotonically as h2. These predictions agree well with experimental observations for Co and Fe films on SiO2.

Changes to processes in estuaries and coastal waters due to intense multiple pressures - An introduction and synthesis

Science.gov (United States)

Mitchell, Steven B.; Jennerjahn, Tim C.; Vizzini, Salvatrice; Zhang, Weiguo

2015-04-01

From the 2013 ECSA conference 'Estuaries and Coastal Areas in Times of Intense Change' a theme emerged that has ended up being the focus of this Special Issue of Estuarine Coastal and Shelf Science, namely 'Changes to processes in estuaries and coastal waters due to intense multiple pressures'. Many parts of the world are continuing to experience unprecedented rates of economic growth, and those responsible for managing coastal and estuarine areas must respond accordingly. At the same time, global climate change and sea level rise are also continuing, placing new or more intense pressures on coastal areas that must be dealt with in ways that are as far as possible managed as a result of good scientific understanding. There are other pressures too, which depend on the system concerned. This article provides an overview of the papers contained within the Special Issue and provides a discussion of how these fit within the main theme of intense multiple stressors, considering how a balance can be achieved between the needs of various different stakeholders and interest groups, and the sustainability of the system concerned. We categorise the papers in four main groupings: (1) stressors related to sea level rise; (2) stressors related to changes in fresh water inputs; (3) stressors related to anthropogenic pollution; and (4) the use of indicators as a means of assessing the effects of stressors, and reflect on the fact that despite the diversity of different challenges and geographical regions involved many of the approaches and discussions contained within the Special Issue have strong similarities, leading to a set of overarching principles that should be considered when making recommendations on management strategies.

Hierarchical opal grating films prepared by slide coating of colloidal dispersions in binary liquid media.

Science.gov (United States)

Lee, Wonmok; Kim, Seulgi; Kim, Seulki; Kim, Jin-Ho; Lee, Hyunjung

2015-02-15

There are active researches on well ordered opal films due to their possible applications to various photonic devices. A recently developed slide coating method is capable of rapid fabrication of large area opal films from aqueous colloidal dispersion. In the current study, the slide coating of polystyrene colloidal dispersions in water/i-propanol (IPA) binary media is investigated. Under high IPA content in a dispersing medium, resulting opal film showed a deterioration of long range order, as well as a decreased film thickness due to dilution effect. From the binary liquid, the dried opal films exhibited the unprecedented topological groove patterns with varying periodic distances as a function of alcohol contents in the media. The groove patterns were consisted of the hierarchical structures of the terraced opal layers with periodic thickness variations. The origin of the groove patterns was attributed to a shear-induced periodic instability of colloidal concentration within a thin channel during the coating process which was directly converted to a groove patterns in a resulting opal film due to rapid evaporation of liquid. The groove periods of opal films were in the range of 50-500 μm, and the thickness differences between peak and valley of the groove were significantly large enough to be optically distinguishable, such that the coated films can be utilized as the optical grating film to disperse infra-red light. Utilizing a lowered hydrophilicity of water/IPA dispersant, an opal film could be successfully coated on a flexible Mylar film without significant dewetting problem. Copyright © 2014 Elsevier Inc. All rights reserved.

Ensuring due process in the IACUC and animal welfare setting: considerations in developing noncompliance policies and procedures for institutional animal care and use committees and institutional officials.

Science.gov (United States)

Hansen, Barbara C; Gografe, Sylvia; Pritt, Stacy; Jen, Kai-Lin Catherine; McWhirter, Camille A; Barman, Susan M; Comuzzie, Anthony; Greene, Molly; McNulty, Justin A; Michele, Daniel Eugene; Moaddab, Naz; Nelson, Randall J; Norris, Karen; Uray, Karen D; Banks, Ron; Westlund, Karin N; Yates, Bill J; Silverman, Jerald; Hansen, Kenneth D; Redman, Barbara

2017-10-01

Every institution that is involved in research with animals is expected to have in place policies and procedures for the management of allegations of noncompliance with the Animal Welfare Act and the U.S. Public Health Service Policy on the Humane Care and Use of Laboratory Animals. We present here a model set of recommendations for institutional animal care and use committees and institutional officials to ensure appropriate consideration of allegations of noncompliance with federal Animal Welfare Act regulations that carry a significant risk or specific threat to animal welfare. This guidance has 3 overarching aims: 1 ) protecting the welfare of research animals; 2 ) according fair treatment and due process to an individual accused of noncompliance; and 3 ) ensuring compliance with federal regulations. Through this guidance, the present work seeks to advance the cause of scientific integrity, animal welfare, and the public trust while recognizing and supporting the critical importance of animal research for the betterment of the health of both humans and animals.-Hansen, B. C., Gografe, S., Pritt, S., Jen, K.-L. C., McWhirter, C. A., Barman, S. M., Comuzzie, A., Greene, M., McNulty, J. A., Michele, D. E., Moaddab, N., Nelson, R. J., Norris, K., Uray, K. D., Banks, R., Westlund, K. N., Yates, B. J., Silverman, J., Hansen, K. D., Redman, B. Ensuring due process in the IACUC and animal welfare setting: considerations in developing noncompliance policies and procedures for institutional animal care and use committees and institutional officials. © FASEB.

Memory properties and charge effect study in Si nanocrystals by scanning capacitance microscopy and spectroscopy

Directory of Open Access Journals (Sweden)

Bassani Franck

2011-01-01

Full Text Available Abstract In this letter, isolated Si nanocrystal has been formed by dewetting process with a thin silicon dioxide layer on top. Scanning capacitance microscopy and spectroscopy were used to study the memory properties and charge effect in the Si nanocrystal in ambient temperature. The retention time of trapped charges injected by different direct current (DC bias were evaluated and compared. By ramp process, strong hysteresis window was observed. The DC spectra curve shift direction and distance was observed differently for quantitative measurements. Holes or electrons can be separately injected into these Si-ncs and the capacitance changes caused by these trapped charges can be easily detected by scanning capacitance microscopy/spectroscopy at the nanometer scale. This study is very useful for nanocrystal charge trap memory application.