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1

Wear and failure mechanisms of multilayered PVD TiN\\/TaN coated tools when milling austenitic stainless steel  

Microsoft Academic Search

As compared to today's single layered coatings, multilayered PVD coatings offer improved mechanical and tribological properties. This work reports on milling austenitic stainless steel with cemented carbide tools coated with multilayered coatings. The purpose was to increase the understanding of wear and failure mechanisms during milling of austenitic stainless steel. Multilayered PVD TiN\\/TaN coatings deposited on cemented carbide substrates are

M Nordin; R Sundström; T. I Selinder; S Hogmark

2000-01-01

2

Corrosion and tribocorrosion behaviour of cermet and cermet\\/nanoscale multilayer CrN\\/NbN coatings  

Microsoft Academic Search

The corrosion and tribocorrosion behaviour of thermally sprayed coatings and thermally sprayed\\/nanoscale multilayer CrN\\/NbN coatings deposited on steel specimens has been studied in 3.5% NaCl solutions. The thermally sprayed coatings are bulk HVOF deposits with nominal composition WC–12Co and Cr3C2–37WC–18Me, while the nanoscale multilayer deposit, topping the thermally sprayed ones, is a CrN\\/NbN coating, obtained by PVD magnetron sputtering technique.

C. Monticelli; A. Balbo; F. Zucchi

2010-01-01

3

Rolling-sliding, scuffing and tribocorrosion behaviour of PVD multilayer coatings for gears application  

Microsoft Academic Search

Purpose – The aim of this work is the study the tribological behaviour and tribocorrosion resistance of newly developed multilayer PVD coatings Cr\\/CrN and CrN\\/ZrCN applied on nitrided F1272 steel for gear applications. Design\\/methodology\\/approach – Tribological characterization has been completed by several tribological tests performed under ball-on-disc configuration, extreme pressure tests to determine the maximum load before the films failure

Raquel Bayón; Cristina Zubizarreta; Roman Nevshupa; Juan Carlos Rodriguez; Xana Fernández; Unai Ruiz de Gopegui; Amaya Igartua

2011-01-01

4

Metallic multilayers at the nanoscale  

SciTech Connect

The development of multilayer structures has been driven by a wide range of commercial applications requiring enhanced material behaviors. Innovations in physical vapor deposition technologies, in particular magnetron sputtering, have enabled the synthesis of metallic-based structures with nanoscaled layer dimensions as small as one-to-two monolayers. Parameters used in the deposition process are paramount to the Formation of these small layer dimensions and the stability of the structure. Therefore, optimization of the desired material properties must be related to assessment of the actual microstructure. Characterization techniques as x-ray diffraction and high resolution microscopy are useful to reveal the interface and layer structure-whether ordered or disordered crystalline, amorphous, compositionally abrupt or graded, and/or lattice strained Techniques for the synthesis of metallic multilayers with subnanometric layers will be reviewed with applications based on enhancing material behaviors as reflectivity and magnetic anisotropy but with emphasis on experimental studies of mechanical properties.

Jankowski, A.F.

1994-11-01

5

Characterisation of tribocorrosion behaviour of multilayer PVD coatings.  

PubMed

The effect of repassivation on tribocorrosion behaviour of two multilayer coatings of different structures is studied experimentally by measuring the variation of instantaneous open-circuit potential during friction. One coating consists of alternating Cr and CrN layers, while another consists of alternated layers of CrN and ZrN. Analysis of the results showed that friction force, i.e. the rate of the mechanical energy supplied to the material in the contact zone, has no direct influence on the tribocorrosion behaviour; however, the wear rate does strongly influence the tribocorrosion. A simple phenomenological model of repassivation of the multilayer coating is developed assuming "surface coverage" approach. This model establishes the relationship between the rate of mechanical activation of material by friction and the behaviour of the open-circuit potential. PMID:20204333

Bayón, R; Nevshupa, R; Zubizarreta, C; Ruiz de Gopegui, U; Barriga, J; Igartua, A

2010-03-05

6

Characterisation of tribocorrosion behaviour of multilayer PVD coatings  

Microsoft Academic Search

The effect of repassivation on tribocorrosion behaviour of two multilayer coatings of different structures is studied experimentally\\u000a by measuring the variation of instantaneous open-circuit potential during friction. One coating consists of alternating Cr\\u000a and CrN layers, while another consists of alternated layers of CrN and ZrN. Analysis of the results showed that friction force,\\u000a i.e. the rate of the mechanical

R. Bayón; R. Nevshupa; C. Zubizarreta; U. Ruiz de Gopegui; J. Barriga; A. Igartua

2010-01-01

7

Effect of layer thickness on thermal properties of multilayer thin films produced by PVD  

Microsoft Academic Search

Cr\\/CrN\\/CrAlN, CrN\\/CrAlN and Cr\\/CrN thin layers were deposited by PVD (Physical Vapor Deposition). The multilayers were obtained from the combined deposition of different layers Cr, CrN and CrAlN thick films on on AISI4140 steel and silicon substrates at 200°C, and evaluated with respect to fundamental properties such as structure and thermal properties. Cr, CrN and CrAlN single layers were also

B. Tlili; C. Nouveau; M. J. Walock; M. Nasri; T. Ghrib

8

Deposition, characterization and machining performance of multilayer PVD coatings on cemented carbide cutting tools  

Microsoft Academic Search

CrN\\/TiN and TiN\\/AlTiN multilayer coatings with different periods were deposited on cemented carbide cutting tools in an industrial-size cathodic arc evaporation device. Nanolayer coatings were particularly studied and the influence of the superlattice period on mechanical behaviors have been investigated. Mechanical properties were first correlated to the period of multilayer and nanolayer coatings. Machining performance of coated cutting tools were

C Ducros; V Benevent; F Sanchette

2003-01-01

9

Synthesis and characterization of multilayered TiC\\/TiB 2 coatings deposited by ion beam assisted, electron beam–physical vapor deposition (EB–PVD)  

Microsoft Academic Search

Polycrystalline 4 ?m and 14 ?m thick multilayer TiB2\\/TiC coatings with varying number of total layers (2–20) were deposited by ion beam assisted, electron beam–physical vapor deposition (IBA, EB–PVD) on WC–6wt.%Co–0.3wt.%TaC substrates. The average Vicker's hardness numbers were found to increase with increasing total number of layers and ranged from 3215 VHN0.050 to 3726 VHN0.050 and 3294 VHN0.050 to 3991

Douglas E. Wolfe; Jogender Singh; Krishnan Narasimhan

2003-01-01

10

Strengthening mechanism of metallic nanoscale multilayer with negative enthalpy of mixing  

NASA Astrophysics Data System (ADS)

Unlike sharp interfaces usually formed in multilayer thin films with positive enthalpy of mixing, intermixing at interface due to negative enthalpy of mixing can reduce the effectiveness of the interface as dislocation motion barrier and thus weaken the hardness/strength of the multilayer thin film. Through first-principles calculations, however, we find that the large negative enthalpy of mixing may lead to negative interface energy and thus the formation of intermetallic compounds in the interface. The resulting intermetallic compounds may have much higher shear moduli than those of the constituent metals, which can make positive contribution to the hardness enhancement of the nanoscale multilayer thin film.

Kong, Yi; Shen, Luming

2011-10-01

11

Effects of surface and interface energies on the bending behavior of nanoscale multilayered beams  

NASA Astrophysics Data System (ADS)

A modified continuum model of the nanoscale multilayered beams is established by incorporating surface and interface energies. Through the principle of minimum potential energy, the governing equations and boundary conditions are obtained. The closed-form solutions are presented and the overall Young's modulus of the beam is studied. The surface and interface energies are found to have a major influence on the bending behavior and the overall Young's modulus of the beam. The effect of surface and interface energies on the overall Young's modulus depends on the boundary condition of the beam, the values of the surface/interface elasticity constants and the initial surface/interface energy of the system. The results can be used to guide the determinations of the surface/interface elasticity properties and the initial surface/interface energies of the nanoscale multilayered materials through nanoscale beam bending experiments.

Wang, K. F.; Wang, B. L.

2013-12-01

12

Bilayer period dependence of CrN/CrAlN nanoscale multilayer thin films  

NASA Astrophysics Data System (ADS)

CrN/CrAlN nanoscale multilayer thin films with a bilayer period (?) ranging from 4.4 to 44.1 nm were deposited on Si wafers (100) by closed field unbalanced magnetron sputtering (CFUBMS). The ? of the layers was controlled by the rotation speed of the substrate holder. The coatings were characterized by high resolution X-ray diffraction and field emission transmission electron microscopy. The CrN/CrAlN nanoscale multilayer thin films exhibited a CrN (200) and AlN (200) crystalline orientation. Nano-indentation testing revealed a hardness ranging from 37 to 46 GPa according to the bilayer period. The highest hardness was obtained with a bilayer period of 5.5 nm due to the high resistance to plastic deformation.

Kim, Youn J.; Byun, Tae J.; Han, Jeon G.

2009-02-01

13

Bilayer period dependence of CrN\\/CrAlN nanoscale multilayer thin films  

Microsoft Academic Search

CrN\\/CrAlN nanoscale multilayer thin films with a bilayer period (lambda) ranging from 4.4 to 44.1 nm were deposited on Si wafers (100) by closed field unbalanced magnetron sputtering (CFUBMS). The lambda of the layers was controlled by the rotation speed of the substrate holder. The coatings were characterized by high resolution X-ray diffraction and field emission transmission electron microscopy. The

Youn J. Kim; Tae J. Byun; Jeon G. Han

2009-01-01

14

Bilayer period dependence of CrN\\/CrAlN nanoscale multilayer thin films  

Microsoft Academic Search

CrN\\/CrAlN nanoscale multilayer thin films with a bilayer period (?) ranging from 4.4 to 44.1 nm were deposited on Si wafers (100) by closed field unbalanced magnetron sputtering (CFUBMS). The ? of the layers was controlled by the rotation speed of the substrate holder. The coatings were characterized by high resolution X-ray diffraction and field emission transmission electron microscopy. The CrN\\/CrAlN

Youn J. Kim; Tae J. Byun; Jeon G. Han

2009-01-01

15

Residual stress characterization of Al/SiC nanoscale multilayers using X-ray  

SciTech Connect

Nanolayered composites are used in a variety of applications such as wear resistant coatings, thermal barrier coatings, optical and magnetic thin films, and biological coatings. Residual stresses produced in these materials during processing play an important role in controlling their microstructure and properties. In this paper, we have studied the residual stresses in model metal-ceramic Al/SiC nanoscale multilayers produced by physical vapor deposition (magnetron sputtering). X-ray synchrotron radiation was used to measure stresses in the multilayers using the sin{sup 2} {Psi} technique. The stresses were evaluated as a function of layer thicknesses of Al and SiC and also as a function of the number of layers. The stress state of Al in the multilayer was largely compressive, compared to single layer Al stresses. This is attributed to a peening mechanism due to bombardment of the Al layers by SiC and Ar neutrals during deposition. The stress evolution was numerically modeled by a simplified peening process to qualitatively explain the Al thickness-dependent residual stresses.

Singh, DRP [Arizona State University; Deng, X. [Arizona State University; Chawla, N. [Arizona State University; Bai, J. [Brookhaven National Laboratory (BNL); Hubbard, Camden R [ORNL; Tang, G [University of New Mexico, Albuquerque; Shen, Y-L [University of New Mexico, Albuquerque

2010-01-01

16

Quantitative x-ray phase imaging at the nanoscale by multilayer Laue lenses  

PubMed Central

For scanning x-ray microscopy, many attempts have been made to image the phase contrast based on a concept of the beam being deflected by a specimen, the so-called differential phase contrast imaging (DPC). Despite the successful demonstration in a number of representative cases at moderate spatial resolutions, these methods suffer from various limitations that preclude applications of DPC for ultra-high spatial resolution imaging, where the emerging wave field from the focusing optic tends to be significantly more complicated. In this work, we propose a highly robust and generic approach based on a Fourier-shift fitting process and demonstrate quantitative phase imaging of a solid oxide fuel cell (SOFC) anode by multilayer Laue lenses (MLLs). The high sensitivity of the phase to structural and compositional variations makes our technique extremely powerful in correlating the electrode performance with its buried nanoscale interfacial structures that may be invisible to the absorption and fluorescence contrasts.

Yan, Hanfei; Chu, Yong S.; Maser, Jorg; Nazaretski, Evgeny; Kim, Jungdae; Kang, Hyon Chol; Lombardo, Jeffrey J.; Chiu, Wilson K. S.

2013-01-01

17

Deformation mechanisms, size effects, and strain hardening in nanoscale metallic multilayers under nanoindentation  

NASA Astrophysics Data System (ADS)

The strain hardening and the related surface pile-up phenomena in CuNi, CuNb and CuNiNb nanoscale multilayered metallic (NMM) composites are investigated using atomistic simulations of nanoindentation on such multilayers with varying individual layer thickness. Using empirical load-stress and displacement-strain relations, the obtained load-depth curves were converted to hardness-strain curves which was then fitted using power law. It is found that the extent of surface pile-up is inversely related to the hardening exponent of the NMMs. Two deformations mechanisms which control the surface pile phenomenon are discovered and discussed. Furthermore, from the stress-strain data, it is found that interfaces and their types play a major role in strain hardening; the strain hardening rate increases with strain when incoherent interfaces are present. The relationship between the hardening parameters and the interfacial dislocation density as well as the relationship between interfacial density and length scales, such as layer thickness and indentation depth, are analyzed, and it is found that the hardness in these NMM has strong inverse power law dependence on the layer thickness.

Shao, S.; Zbib, H. M.; Mastorakos, I. N.; Bahr, D. F.

2012-08-01

18

X-ray diffraction analysis of the residual stress state in PVD TiN\\/CrN multilayer coatings deposited on tool steel  

Microsoft Academic Search

Thin multilayer films, especially nitrides of transition metal, exhibit hardness enhancements that are significantly higher than those predicted by the rule of mixtures. In this study, TiN\\/CrN multilayers, consisting of alternating nanometer-scale TiN and CrN layers, were deposited by arc evaporation technique on M2 steel. Different period thicknesses ? have been prepared: 10, 20, 40 and 60 nm. A recent

C. Mendibide; P. Steyer; C. Esnouf; P. Goudeau; D. Thiaudière; M. Gailhanou; J. Fontaine

2005-01-01

19

Performance of nano-structured multilayer PVD coating TiAlN\\/VN in dry high speed milling of aerospace aluminium 7010-T7651  

Microsoft Academic Search

A low-friction and wear resistant TiAlN\\/VN multilayer coating with TiAlN\\/VN bilayer thickness 3 nm has been grown by using the combined cathodic arc etching and unbalanced magnetron sputtering deposition on high speed steel tools for dry cutting of aluminium alloys. In this paper, in-lab and industrial high speed milling tests have been performed on an aerospace aluminium alloy 7010-T7651. The

Q. Luo; G. Robinson; M. Pittman; M. Howarth; W.-M. Sim; M. R. Stalley; H. Leitner; R. Ebner; D. Caliskanoglu; P. Eh. Hovsepian

2005-01-01

20

Multilayered graphene in K(a)-band: nanoscale coating for aerospace applications.  

PubMed

We report on the experimental study of electromagnetic (EM) properties of multilayered graphene in K(a)-band synthesized by catalytic chemical vapor deposition (CVD) process in between nanometrically thin Cu catalyst film and dielectric (SiO2) substrate. The quality of the produced multilayered graphene samples was monitored by Raman spectroscopy. The thickness of graphene films was controlled by atomic force microscopy (AFM) and was found to be a few nanometers (up to 5 nm). We discovered, that the fabricated graphene, being only some thousandth of skin depth, provided remarkably high EM shielding efficiency caused by absorption losses at the level of 35-43% of incident power. Being highly conductive at room temperature, multilayer graphene emerges as a promising material for manufacturing ultrathin microwave coatings to be used in aerospace applications. PMID:23882850

Kuzhir, P; Volynets, N; Maksimenko, S; Kaplas, T; Svirko, Yu

2013-08-01

21

Improvements on the wear resistance of high thermal conductivity Cu alloys using an electroless Ni–P coating prior to PVD deposition  

Microsoft Academic Search

An attempt to improve the load support for hard PVD coatings on soft Cu alloys has been made by using a medium phosphorous content electroless Ni–P coating prior to PVD deposition, envisaging the application of these coating\\/substrate systems in plastic injection moulding. Several PVD coatings, including TiN, CrN, CrAlN, multilayered CrAlN, WC–C, multilayered CrAlN\\/WC–C were deposited onto an Ampcoloy 940 Cu

J. C. Avelar-Batista; E. Spain; M. Letch; J. Housden; R. Beechey

2006-01-01

22

Deformation and material removal in a nanoscale multi-layer thin film solar panel using nanoscratch  

Microsoft Academic Search

Amorphous Si thin film solar panels are multi-layer structures consisting of nanometric layers of hard and brittle materials. The deformation and material removal characteristics of the panel cross-section were investigated using nano-mechanical testing. Nanoindentation and nanoscratching were performed using indenters of various geometries at a range of loads. Atomic force microscopy and electron microscopy were used to study the resulting

Taro Sumitomo; Han Huang; Libo Zhou

2011-01-01

23

Resonance analysis of multi-layered graphene sheets used as nanoscale resonators  

Microsoft Academic Search

A stacked plate model for the vibration of multi-layered graphene sheets (MLGSs), in which the van der Waals (vdW) interaction between layers is described by an explicit formula, is presented. Explicit formulae are derived for predicting the natural frequencies of double- and triple-layered graphene sheets, and they clearly indicate the effect of vdW interaction on the natural frequencies. The natural

X. Q. He; S. Kitipornchai; K. M. Liew

2005-01-01

24

Resonance analysis of multi-layered graphene sheets used as nanoscale resonators  

Microsoft Academic Search

A stacked plate model for the vibration of multi-layered graphene sheets (MLGSs), in which the van der Waals (vdW) interaction between layers is described by an explicit formula, is presented. Explicit formulae are derived for predicting the natural frequencies of double-and triple-layered graphene sheets, and they clearly indicate the effect of vdW interaction on the natural frequencies. The natural frequencies

X Q He; S Kitipornchai; K M Liew

2005-01-01

25

Nanoscale steel-brass multilayer laminates made by cold rolling: Microstructure and tensile properties  

SciTech Connect

The thrust of this study is to fabricate steel-brass multilayer laminates with layer thicknesses in the nanometer range and to evaluate their mechanical properties. Repeated cold rolling of multilayer stacks was adopted to produce the laminates, because the relative simplicity and the low-cost nature of this process can allow the scaling-up of the technique to the level of commercial-scale production. This work is a continuation of a previous study, in which steel-brass laminates with layer thicknesses in the micrometer range were fabricated for the first time and their tensile properties were evaluated. The present work, however, emphasizes making multilayers with layer thicknesses in the nanometer range and evaluating their mechanical properties. The dependence of strength and ductility on the layer spacing in the nanometer range, is highlighted. It is shown that strength levels comparable to quenched and tempered low alloy steels can be achieved in the laminates by rolling down to the low end of nanometer range. The relevant strengthening mechanisms are also discussed.

Kavarana, F.H.; Ravichandran, K.S.; Sahay, S.S.

2000-05-10

26

Microstructure and mechanical properties of aluminum/aluminum-scandium metallic multilayers: Deformation mechanisms at the nanoscale  

NASA Astrophysics Data System (ADS)

Multilayer thin film structures with layer dimensions in the nanometer length scale have proven to be some of the strongest synthetic materials ever produced, and in the system studied here, record hardnesses for aluminum-based materials have been observed. This work discusses the fabrication, characterization and mechanical response of a unique system constructed from aluminum and scandium. Thin film deposition techniques have been used to create high-quality polycrystalline multilayered films consisting of Al layers (6--100 nm thick) separated by thin (0.5--5 nm) layers of Al3Sc. In bulk form, the Al 3Sc phase has the L12 crystal structure and is extraordinarily stable. The crystal lattice of Al3Sc is only slightly larger than that of pure Al, and therefore tends to form a coherent interface with Al. Thus, these multilayer films provide a simple ideal system for study, where interpretation of hardness results is simplified by the presence of coherent interfaces, and where the principal barrier to dislocation motion is an anti-phase boundary (APB) that must be formed in the Al3Sc in order to pass dislocations through the intermetallic phase. Microstructural characterization was performed by transmission electron microscopy and x-ray diffraction and the mechanical strength of the Al/Al 3Sc multilayers was tested by nanoindentation. The influence of the substrate on measured properties was significant and an improved method for determining film hardness is discussed. Overall, large increases in hardness were observed with decreasing aluminum layer thickness in the Al/Al3 Sc multilayers. These results were analyzed in detail and several simple mechanisms were proposed to account for the behavior. Primarily, the hardness values obtained were considered in terms of the motion of single dislocations that are constrained by layers of Al3Sc. Models of forces on dislocations, including the effect of forming an anti-phase boundary (APB) in the Al 3Sc, predicted that the thickness of Al3Sc plays an important role in determining the strengthening response and determines if dislocations are confined to a single aluminum layer, or if they cut across several layers.

Phillips, Mark Andrew

27

Mechanics of nanoscale metallic multilayers: from atomic-scale to micro-scale  

SciTech Connect

Layered composites of Cu/Nb with incoherent interfaces achieve very high strength levels. Interfaces play a crucial role in materials strength by acting as barriers to slip. Atomistic models of Cu/Nb bilayers are used to explore the origins of this resistance. The models clearly show that dislocations near an interface experience an attraction toward the interface. This attraction is caused by shear of the interface induced by the stress field of the dislocation. More importantly, atomistic simulations also reveal that interfacial dislocations easily move in interfaces by both glide and climb. Integrating these findings into a micro-scale model, we develop a three-dimensional crystal elastic-plastic model to describe the mechanical behavior of nanoscale metallic multi layers.

Wang, Jian [Los Alamos National Laboratory; Hoagland, Richard G [Los Alamos National Laboratory; Misra, Amit [Los Alamos National Laboratory

2008-01-01

28

Study of s-polarized photonic bandgap structure in three component optical fibonacci multilayers composed of nanoscale materials  

Microsoft Academic Search

In this communication dispersion relation, reflection and transmission coefficient for quasiperiodic optical multilayers arranged according to the three-component Fibonacci rule is derived using transfer matrix method. In this work Fibonacci multilayers using three different photonic band gap (PBG) materials is designed and its photonic band gap structure is presented. Also, a detailed calculation for allowed and forbidden frequency bands for

R. K. Mishra; P. C. Pandey

2009-01-01

29

Structure and corrosion properties of PVD Cr-N coatings  

NASA Astrophysics Data System (ADS)

PVD Cr-N coatings produced by physical vapor deposition (PVD) are increasingly used for mechanical and tribological applications in various industrial sectors. These coatings are particularly attractive for their excellent corrosion resistance, which further enhances the lifetime and service quality of coated components. PVD Cr-N coated steels in an aqueous solution are usually corroded by galvanic attack via through-coating ``permeable'' defects (e.g., pores). Therefore, the corrosion performance of Cr-N coated steel is determined by a number of variables of the coating properties and corrosive environment. These variables include: (i) surface continuity and uniformity; (ii) through-coating porosity; (iii) film density and chemical stability; (iv) growth stresses; (v) interfacial and intermediate layers; (vi) coating thickness; (vii) coating composition; and (viii) substrate properties. In this article, PVD Cr-N coatings were prepared, by electron-beam PVD and sputter deposition, with different compositions, thicknesses, and surface roughnesses, by changing the N2 flow rate, applying multilayering techniques and changing the substrate finish prior to coating. The microstructure of such coatings is investigated by various analytical techniques such as glancing angle x-ray diffraction and scanning electron microscopy, which are also correlated with the corrosion performance of the coated steel. Both dc polarization and ac impedance spectroscopy were employed to investigate the corrosion resistance of Cr-N coated steel in a 0.5N NaCl solution. It has been found that the N2 flow rate during reactive deposition strongly determines the microstructure of Cr-N coatings (due to the changing nitrogen content in the film) and can thus affect the corrosion resistance of coated systems. The surface finish of the steel substrate also affects the uniformity and coverage of PVD coatings; grooves and inclusions on the original substrate can raise the susceptibility of coated systems to crevice corrosion. Increased coating thickness can also greatly reduce the incidence of through-coating porosity such that the improvement in corrosion performance of thicker Cr-N coatings is significant.

Liu, C.; Bi, Q.; Ziegele, H.; Leyland, A.; Matthews, A.

2002-05-01

30

Optical multilayers with an amorphous fluoropolymer  

SciTech Connect

Multilayered coatings were made by physical vapor deposition (PVD) of a perfluorinated amorphous polymer, Teflon AF2400, together with other optical materials. A high reflector at 1064 run was made with ZnS and AF2400. An all-organic 1064-nm reflector was made from AF2400 and polyethylene. Oxide (HfO{sub 2}, SiO{sub 2}) compatibility was also tested. Each multilayer system adhered to itself. The multilayers were influenced by coating stress and unintentional temperature rises during PVD deposition.

Chow, R.; Loomis, G.E.; Lindsey, E.F.

1994-07-01

31

Femtosecond Single-Shot Imaging of Nanoscale Ferromagnetic Order in Co/Pd Multilayers using Resonant X-ray Holography  

SciTech Connect

We present the first single-shot images of ferromagnetic, nanoscale spin order taken with femtosecond x-ray pulses. X-ray-induced electron and spin dynamics can be outrun with pulses shorter than 80 fs in the investigated fluence regime, and no permanent aftereffects in the samples are observed below a fluence of 25 mJ/cm{sup 2}. Employing resonant spatially-muliplexed x-ray holography results in a low imaging threshold of 5 mJ/cm{sup 2}. Our results open new ways to combine ultrafast laser spectroscopy with sequential snapshot imaging on a single sample, generating a movie of excited state dynamics.

Wang, Tianhan; Zhu, Diling; Benny Wu,; Graves, Catherine; Schaffert, Stefan; Rander, Torbjorn; Muller, leonard; Vodungbo, Boris; Baumier, Cedric; Bernstein, David P.; Brauer, Bjorn; Cros, Vincent; Jong, Sanne de; Delaunay, Renaud; Fognini, Andreas; Kukreja, Roopali; Lee, Sooheyong; Lopez-Flores, Victor; Mohanty, Jyoti; Pfau, Bastian; Popescu, 5 Horia

2012-05-15

32

Tool Life and Surface Integrity When Machining Inconel 718 With PVD- and CVD-Coated Tools  

Microsoft Academic Search

Test results show that when machining nickel-based Inconel 718 alloy under the cutting conditions investigated, the multilayer PVD-coated carbide grades gave the best performance in terms of tool life. This was due to their higher hardness, toughness, abrasion resistance, good heat transmission behavior of the multiple (TiN\\/TiCN\\/TiN) coatings as well as thicker coating layer (relative to the single-coated grade). The

E. O. Ezugwu; Z. M. Wang; C. I. Okeke

1999-01-01

33

Characterization of Nanoscale Transformations in Polyelectrolyte Multilayers Fabricated from Plasmid DNA Using Laser Scanning Confocal Microscopy in Combination with Atomic Force Microscopy  

PubMed Central

Laser scanning confocal microscopy (LSCM) and atomic force microscopy (AFM) were used to characterize changes in nanoscale structure that occur when ultrathin polyelectrolyte multilayers (PEMs) are incubated in aqueous media. The PEMs investigated here were fabricated by the deposition of alternating layers of plasmid DNA and a hydrolytically degradable polyamine onto a precursor film composed of alternating layers of linear poly(ethylene imine) (LPEI) and sodium poly(styrene sulfonate) (SPS). Past studies of these materials in the context of gene delivery revealed transformations from a morphology that is smooth and uniform to one characterized by the formation of nanometer-scale particulate structures. We demonstrate that in-plane registration of LSCM and AFM images acquired from the same locations of films fabricated using fluorescently labeled polyelectrolytes allows the spatial distribution of individual polyelectrolyte species to be determined relative to the locations of topographic features that form during this transformation. Our results suggest that this physical transformation leads to a morphology consisting of a relatively less disturbed portion of film composed of polyamine and DNA juxtaposed over an array of particulate structures composed predominantly of LPEI and SPS. Characterization by scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) microanalysis provides additional support for this interpretation. The combination of these different microscopy techniques provides insight into the structures and dynamics of these multicomponent thin films that cannot be achieved using any one method alone, and that could prove useful for the further development of these assemblies as platforms for the surface-mediated delivery of DNA.

Fredin, Nathaniel J.; Flessner, Ryan M.; Jewell, Christopher M.; Bechler, Shane L.; Buck, Maren E.; Lynn, David M.

2010-01-01

34

Ignition properties of multilayer nanoscale reactive foils and the properties of metal-ceramic joints made with the same  

NASA Astrophysics Data System (ADS)

A novel method for joining metals and ceramics using an Al-(Ni-7V) reactive multilayer foil as a heat source was studied. The components in the joint are first pre-wet or pre-metallized with a solder or braze before the reactive foil is placed between them and reacted, melting the solder or braze. On cooling, a solid joint is formed. It was shown using a SiC-Ti joint system that for a given joint system, there is are critical values for the foil's heat of reaction and total heat below which the braze in the joint will not melt, with foil heat of reaction having more of an impact than total heat. Experimental results from Al-Al and Al2O3-Al2O3 joint systems showed that the interface between the solder and the joint component can play a critical role in determining joint strength. Experimental results and numerical predictions using Al-Al2O3 and Al-glass joint systems showed that the elastic strain energy (ESE) and residual stress in a metal-ceramic reactive foil have two sources: The bending, caused by the uneven thermal profile across each joint component created by the reacting foil, that the joint components undergo while the solder or braze is molten and which is locked in when the solder or braze solidifies, and uneven average thermal contraction between the two components. The distribution of elastic strain energy and stress in a reactive foil joint is determined by the thermal diffusivities and coefficients of thermal expansion of the two joint components. The ignition requirements of reactive foils were investigated using two experimental methods, an electric pulse and mechanical stab detonation, and a numerical simulation of the electric pulse ignition method. Experimental results and numerical predictions showed that increasing foil bilayer or increasing intermixed layer thickness will make a foil more difficult to ignite. An estimated energy density of 1GJ/m3 was found experimentally to be an upper limit of the minimum energy density required for ignition of a 1:1 molar ratio Al-(Ni-7V) reactive foil with 50nm bilayers and a 2.25nm intermixed layer thickness. An autoignition temperature of approximately 419K was found using both experimental results and numerical predictions, both of which accounted for heat spreading during an ignition attempt.

Spey, Stephen John, Jr.

35

Cr and Zr\\/Cr nitride CAE-PVD coated aluminum bipolar plates for polymer electrolyte membrane fuel cells  

Microsoft Academic Search

In this work, two nitride coatings deposited on aluminum-based bipolar plates via cathodic arc evaporation physical vapor deposition (CAE-PVD) have been evaluated using two different techniques. The coating materials, a multi-layer chromium-zirconium nitride (ZrN–CrN) and a monolayer chromium nitride (CrN) have been exposed to electrochemical polarization tests for corrosion resistance simulating the typical environment in the anode and cathode sides

José Barranco; Félix Barreras; Antonio Lozano; Ana M. Lopez; Vicente Roda; Jesús Martin; Mario Maza; Gonzalo G. Fuentes; Eluxka Almandoz

2010-01-01

36

The effects of rapid thermal annealing on the electrical, optical, and structural properties of Nb:TiO2 multilayer electrodes with an inserted nanoscale Ag layer for organic solar cells  

NASA Astrophysics Data System (ADS)

We investigated the effects of rapid thermal annealing (RTA) on the electrical, optical, structural, interfacial, and surface properties of Nb:TiO2 (NTO)-Ag-NTO multilayer electrodes inserting a nanoscale Ag layer for application in organic solar cells (OSCs). Up to an annealing temperature of 500 °C, the resistivity and optical transmittance of the NTO-Ag-NTO electrodes were stably maintained due to the absence of Ag outdiffusion. The effective activation of the Nb in the NTO layer led to a slight decrease in the resistivity and an increase in the band gap caused by the Burstein-Moss effect. However, increasing the RTA temperature above 600 °C resulted in degradation of the NTO-Ag-NTO multilayer electrode due to severe Ag diffusion. Based on the synchrotron x-ray scattering and x-ray photoelectron spectroscopy analyses results, the electrical properties of the NTO-Ag-NTO electrodes are correlated with the microstructure and interfacial diffusion of each layer. In addition, it was found that the performance of the OSC was critically dependent on the RTA temperature of the NTO-Ag-NTO electrodes even though the as-deposited NTO-Ag-NTO electrode had a fairly low resistivity. This indicates that the activation of Nb dopants in the top NTO layer plays an important role in the extraction of carriers from the organic layer to the anode (NTO-Ag-NTO) electrode.

Park, Jun-Hyuk; Choi, Yoon-Young; Kim, Han-Ki; Lee, Hyun Hwi; Na, Seok-In

2010-10-01

37

PVD TBC experience on GE aircraft engines  

NASA Astrophysics Data System (ADS)

The higher performance levels of modern gas turbine engines present significant challenges in the reli-ability of materials in the turbine. The increased engine temperatures required to achieve the higher per-formance levels reduce the strength of the materials used in the turbine sections of the engine. Various forms of thermal barrier coatings have been used for many years to increase the reliability of gas turbine engine components. Recent experience with the physical vapor deposition process using ceramic material has demonstrated success in extending the service life of turbine blades and nozzles. Engine test results of turbine components with a 125 ?m (0.005 in.) PVD TBC have demonstrated component operating tem-peratures of 56 to 83 °C (100 to 150 °F) lower than non-PVD TBC components. Engine testing has also revealed that TBCs are susceptible to high angle particle impact damage. Sand particles and other engine debris impact the TBC surface at the leading edge of airfoils and fracture the PVD columns. As the impacting continues, the TBC erodes in local areas. Analysis of the eroded areas has shown a slight increase in temperature over a fully coated area ; however, a significant temperature reduc-tion was realized over an airfoil without TBC.

Maricocchi, A.; Bartz, A.; Wortman, D.

1997-06-01

38

Enhanced coercivity in thermally processed (Nd,Dy)(Fe,Co,Nb,B){sub 5.5}/{alpha}-Fe nanoscale multilayer magnets  

SciTech Connect

Structural and magnetic properties of laminated (Nd,Dy)(Fe,Co,Nb,B){sub 5.5}/Fe nanocomposites are investigated. Normally, the addition of the soft phase to the hard phase enhances the remanence but deteriorates the permanent-magnet performance of the material by reducing the coercivity. In the present system, the coercivity increases to 1608 kA/m (20.2 kOe) in thermally processed Nd-Dy-Fe-Co-Nb-B(15 nm)/Fe(4 nm) multilayered nanocomposites, which is higher than that of the single-layer hard-magnetic film. The abnormally high coercivity is achieved by annealing at relatively high temperature, which breaks the laminated structure of the as-deposited multilayer. A likely physical explanation of the enhanced coercivity is the introduction of the domain-wall pinning sites that counteract the inevitable decrease of the nucleation field.

Liu, W.; Li, X.Z.; Liu, J.P.; Sun, X.K.; Chen, C.L.; Skomski, R.; Zhang, Z.D.; Sellmyer, D.J. [Shenyang National Laboratory for Materials Science, Institute of Metal Research, and International Centre for Materials Physics, Chinese Academy of Science, Shenyang 110016 (China); Center for Materials Research and Analysis, University of Nebraska, Lincoln, Nebraska 68588 (United States); Department of Physics, University of Texas at Arlington, Arlington, Texas 76019 (United States); Shenyang National Laboratory for Materials Science, Institute of Metal Research, and International Centre for Materials Physics, Chinese Academy of Science, Shenyang 110016 (China); Center for Materials Research and Analysis, University of Nebraska, Lincoln, Nebraska 68588 (United States); Shenyang National Laboratory for Materials Science, Institute of Metal Research, and International Centre for Materials Physics, Chinese Academy of Science, Shenyang 110016 (China); Center for Materials Research and Analysis, University of Nebraska, Lincoln, Nebraska 68588 (United States)

2005-05-15

39

The effect of (Ti+Al):V ratio on the structure and oxidation behaviour of TiAlN\\/VN nano-scale multilayer coatings  

Microsoft Academic Search

Nano-scaled multilayered TiAlN\\/VN coatings have been grown on stainless steel and M2 high speed steel substrates at UB=?85 V in an industrial, four target, Hauzer HTC 1000 coater using combined cathodic steered arc etching\\/unbalanced magnetron sputtering. X-ray diffraction (XRD) has been used to investigate the effects of process parameters (Target Power) on texture evolution (using texture parameter T*), development of

D. B Lewis; S Creasey; Z Zhou; J. J Forsyth; A. P Ehiasarian; P. Eh Hovsepian; Q Luo; W. M Rainforth; W.-D Münz

2004-01-01

40

Tribological properties of unbalanced magnetron sputtered nano-scale multilayer coatings TiAlN\\/VN and TiAlCrYN deposited on plasma nitrided steels  

Microsoft Academic Search

Unbalanced magnetron sputtered multilayer coatings TiAlN\\/VN and TiAlCrYN grown on pulse plasma nitriding pre-treated low alloy steel P20 have been characterised by using X-ray diffraction (XRD), scanning electron microscope (SEM), micro-indentation, scratch and pin-on-disc wear tests. A 160-?m-thick nitrided case was formed on the steel surface containing a pure Fe3N and Fe4N compound layer and showing hardness up to 8.5

Q. Luo; P. Eh. Hovsepian; D. B. Lewis; W.-D. Münz; Y. N. Kok; J. Cockrem; M. Bolton; A. Farinotti

2005-01-01

41

Magnetism of rare-earth--transition-metal nanoscale multilayers. I. Experiments on Dy/Co, Dy/Fe, and Tb/Fe  

SciTech Connect

Experimental investigations of magnetic and structural properties for rare-earth--transition-metal (RE-TM) compositionally modulated films (CMF) are presented in this paper. In particular, {ital A}{sup RE}/{ital B}{sup TM} including {ital A}{sup RE}=Dy and Tb and {ital B}{sup TM}=Fe, Co, and Ni, are studied. The layer thickness and temperature dependence of magnetic properties, which can be interpreted in terms of the antiferromagnetic coupling of RE and TM moments and their atomic distributions, are reported. These {ital A}{sup RE}/{ital B}{sup TM} CMF with nanoscale layer thicknesses exhibit perpendicular magnetic anisotropy (PMA) and the range of the layer thickness required for PMA is determined. The origin of PMA is also discussed.

Shan, Z.S.; Sellmyer, D.J. (Behlen Laboratory of Physics, University of Nebraska-Lincoln, Lincoln, NE (USA) Center for Materials Research Analysis, University of Nebraska-Lincoln, Lincoln, NE (USA))

1990-12-01

42

On the structure and oxidation mechanisms in nanoscale hard coatings  

NASA Astrophysics Data System (ADS)

Thin-film structures consisting of alternating nanoscale multilayers show substantial hardness increases compared with monolithic coatings of the constituent materials. Coatings, such as TiAlN/VN are deposited using PVD with individual coating bi-layer thickness of ~3nm. Since TiAlN and VN are isostructural and mutually soluble, mixing of the two layers during deposition is expected, which will inevitably affect properties. Energy filtered TEM using a field emission gun source allowed important information on layer structure, but failed to reveal details <1nm. Spherical aberration corrected scanning transmission electron microscopy (STEM) allowed the composition of individual atomic columns to be probed, which yielded a good match between experiment and numerical models of the layer mixing. For high speed machining operations, the oxidation behaviour of coatings becomes an important consideration. Static oxidation of TiAlN/VN films was studied in the range 550-700oC, and characterised by high temperature in-situ XRD and STEM/EDX/EELS of selected surface cross-sections. Oxidation of the TiAlN/VN coating started at >=550°C with the VN being the first component to oxidise. At temperatures >600°C, a duplex oxide structure was formed, with several phases observed, including V2O5, TiO2 and AlVO4, with V2O5 being the dominant oxide at the outer layer at 638°C. These coatings exhibit low friction in dry sliding which is believed to arise from the inherently low friction of V2O5. Focused ion beam studies of wear tests at 630°C confirmed that the contact surface comprised small (~50nm), equiaxed and largely agglomerated V2O5 crystals, confirming the hypothesis.

Rainforth, W. Mark; Zhou, Z.

2006-02-01

43

Cutting properties of the Al 2O 3 + SiC (w) based tool ceramic reinforced with the PVD and CVD wear resistant coatings  

Microsoft Academic Search

The paper presents investigation results of tribological properties of the coatings deposited with the PVD and CVD techniques on cutting inserts made from the Al2O3+SiC(w) oxide tool ceramic. Tests were carried out on the multipoint inserts made from the Al2O3+SiC(w) oxide ceramics, uncoated and coated with gradient, mono-, multilayer and multicomponent hard wear resistant coatings composed of TiN, TiCN, TiAlN,

M. Sokovi?; J. Miku?a; L. A. Dobrza?ski; J. Kopa?; L. Kose?; P. Panjan; J. Madejski; A. Piech

2005-01-01

44

Generation and performance of localised surface plasmons utilising nano-scale structured multi-layered thin films deposited upon D-shaped optical fiber  

NASA Astrophysics Data System (ADS)

A new generation of surface plasmonic optical fibre sensors is fabricated using multiple coatings deposited on a lapped section of a single mode fibre. Post-deposition UV laser irradiation using a phase mask produces a nano-scaled surface relief grating structure, resembling nano-wires. The overall length of the individual corrugations is approximately 14 ?m with an average full width half maximum of 100 nm. Evidence is presented to show that these surface structures result from material compaction created by the silicon dioxide and germanium layers in the multi-layered coating and the surface topology is capable of supporting localised surface plasmons. The coating compaction induces a strain gradient into the D-shaped optical fibre that generates an asymmetric periodic refractive index profile which enhances the coupling of the light from the core of the fibre to plasmons on the surface of the coating. Experimental data are presented that show changes in spectral characteristics after UV processing and that the performance of the sensors increases from that of their pre-UV irradiation state. The enhanced performance is illustrated with regards to change in external refractive index and demonstrates high spectral sensitivities in gaseous and aqueous index regimes ranging up to 4000 nm/RIU for wavelength and 800 dB/RIU for intensity. The devices generate surface plasmons over a very large wavelength range, (visible to 2 ?m) depending on the polarization state of the illuminating light.

Allsop, T.; Neal, R.; Mou, C.; Dvorak, M.; Rozhin, A.; Kalli, K.; Webb, D. J.

2013-09-01

45

Performance evaluation of PVdF gel polymer electrolytes  

Microsoft Academic Search

A series of gel polymer electrolytes containing PVdF as homo polymer, a mixture of 1:1 Ethylene Carbonate (EC) : Propylene\\u000a Carbonate (PC) as plasticizer and lithium-bistrifluoromethane sulphone imide [imide — LiN (CF3SO2)2] has been developed. Amounts of polymer (PVdF), plasticizer and the imide lithium salt have been varied as a function of\\u000a their weight ratio composition in this regard. Dimensionally

P. Periasamy; K. Tatsumi; N. Kalaiselvi; M. Shikano; T. Fiyieda; Y. Saito; T. Sakai; M. Mizukata; A. Kajinami; S. Deki

2002-01-01

46

PS-PVD Process for Coating Aircraft Engine Components  

NASA Video Gallery

This short video shows a process that NASA's Glenn Research Center is developing that can deposit very thin and smooth layers of coating on ceramic matrix composite materials for use as aircraft engine turbine components. The process, called "Plasma Spray-Physical Vapor Deposition," or PS-PVD, can apply coatings that withstand up to 2700 degrees Fahrenheit, improving engine thermal efficiency and reducing fuel burn. › Watch 'Intro to PS-PVD Process'

Christopher O

2013-03-06

47

Nanoscale Wicking  

Microsoft Academic Search

A wick is a bundle of fibers that by capillary attraction draws up to be burned a steady supply of the oil in lamps. In textile research, wicking is the process by which liquids are transported across or along fibers by capillary action (of relevance to perspiration). A similar phenomenon was recently discovered in our lab with mats of nanoscale

Jijie Zhou; Elijah Sansom; Mory Gharib; Flavio Noca

2003-01-01

48

EDITORIAL: Nanoscale metrology Nanoscale metrology  

Microsoft Academic Search

Instrumentation and measurement techniques at the nanoscale play a crucial role not only in extending our knowledge of the properties of matter and processes in nanosciences, but also in addressing new measurement needs in process control and quality assurance in industry. Micro- and nanotechnologies are now facing a growing demand for quantitative measurements to support the reliability, safety and competitiveness

G. B. Picotto; L. Koenders; G. Wilkening

2009-01-01

49

Evaporation rate and composition monitoring of electron beam PVD processes  

SciTech Connect

Lawrence Livermore National Laboratory (LLNL) is developing sensor and control technology to improve the quality and range of applicability of electron beam PVD. The approach being developed uses tunable lasers to measure, the density and composition of the vapor plume. This paper reviews the principles of operation of laser based sensors and discusses data from experiments in which titanium and niobium are co-vaporized. Laser data agreed well with deposited film compositions and spatial variations in deposited film cross sections. Laser based vapor monitoring appears to have broad applicability and has the potential to extend the use of high rate electron beam PVD.

Anklam, T.M.; Berzins, L.V.; Braun, D.G.; Haynam, C.; Meier, T.; McClelland, M.A.

1995-03-01

50

Nanoscale potentiometry  

PubMed Central

Potentiometric sensors share unique characteristics that set them apart from other electrochemical sensors. Potentiometric nanoelectrodes have been reported and successfully used for many decades, and we review these developments. Current research chiefly focuses on nanoscale films at the outer or the inner side of the membrane, with outer layers for increasing biocompatibility, expanding the sensor response, or improving the limit of detection (LOD). Inner layers are mainly used for stabilizing the response and eliminating inner aqueous contacts or undesired nanoscale layers of water. We also discuss the ultimate detectability of ions with such sensors and the power of coupling the ultra-low LODs of ion-selective electrodes with nanoparticle labels to give attractive bioassays that can compete with state-of-the-art electrochemical detection.

Bakker, Eric; Pretsch, Erno

2008-01-01

51

Programmable nanoscale domain patterns in multilayers  

Microsoft Academic Search

The pattern formation in systems with multiple layers of adsorbate molecules is studied. We consider the presence of two types of molecules in each layer, which are characterized by different dipole moments. The patterns are characterized by the non-uniform distribution of the two molecules. A phase field model is developed to simulate the molecular motion and patterning under the combined

Wei Lu; David Salac

2005-01-01

52

Nanoscale Wicking  

NASA Astrophysics Data System (ADS)

A wick is a bundle of fibers that by capillary attraction draws up to be burned a steady supply of the oil in lamps. In textile research, wicking is the process by which liquids are transported across or along fibers by capillary action (of relevance to perspiration). A similar phenomenon was recently discovered in our lab with mats of nanoscale fibers. A droplet containing a surfactant solution was placed on top of a well-aligned mat of carbon nanotubes: wicking was then observed as a film of liquid propagating within the nanocarpet, such as a stain or drop absorbed into a textile fabric. The nanoscale wicking process in carbon nano-arrays offers a simple and enabling technology for the processing (transport, mixing, filtering) of picoliters of fluids without any need for confinement (nanochannel) or bulky driving pressure apparatus. In this work, nanoscale wicking properties are quantified as a function of surfactant activity and carbon nanoarray geometry. The biomolecular sieving capability of the nanotube arrays is also put to test by the addition of biomolecules, while using the wicking process as the fluid driving force.

Zhou, Jijie; Sansom, Elijah; Gharib, Mory; Noca, Flavio

2003-11-01

53

Experimental Methods of Assessment of PVD Coatings Properties  

Microsoft Academic Search

The paper investigates the properties of thin coatings deposited by Physical Vapour Deposition (PVD) technology. This is a modern technology of depositing thin coatings onto the surface of machine parts. Technological procedures of deposition of thin coatings undergo constant improvement. At the same time, new types of coatings are developed. These developments necessitate evaluation of structure, composition and properties of

Mária HAGAROVÁ

2007-01-01

54

Enhancing corrosion resistance of PVD-coated tools  

Microsoft Academic Search

It is known that conventional PVD coatings like TiN and CrN offer a limited corrosion resistance due to their intrinsic porosity, that locally exposes the substrate. In the manufacturing of cutting, forming and plastic molding tools this fact restricts, in some cases, the option of steels that present a high hardness after heat treatment, but have a low corrosion resistance:

P. K Vencovsky; R Sanchez; J. R. T Branco; M Galvano

1998-01-01

55

Antimicrobial titanium\\/silver PVD coatings on titanium  

Microsoft Academic Search

BACKGROUND: Biofilm formation and deep infection of endoprostheses is a recurrent complication in implant surgery. Post-operative infections may be overcome by adjusting antimicrobial properties of the implant surface prior to implantation. In this work we described the development of an antimicrobial titanium\\/silver hard coating via the physical vapor deposition (PVD) process. METHODS: Coatings with a thickness of approximately 2 ?m

Andrea Ewald; Susanne K Glückermann; Roger Thull; Uwe Gbureck

2006-01-01

56

Nanoscale flexoelectricity.  

PubMed

Electromechanical effects are ubiquitous in biological and materials systems. Understanding the fundamentals of these coupling phenomena is critical to devising next-generation electromechanical transducers. Piezoelectricity has been studied in detail, in both the bulk and at mesoscopic scales. Recently, an increasing amount of attention has been paid to flexoelectricity: electrical polarization induced by a strain gradient. While piezoelectricity requires crystalline structures with no inversion symmetry, flexoelectricity does not carry this requirement, since the effect is caused by inhomogeneous strains. Flexoelectricity explains many interesting electromechanical behaviors in hard crystalline materials and underpins core mechanoelectric transduction phenomena in soft biomaterials. Most excitingly, flexoelectricity is a size-dependent effect which becomes more significant in nanoscale systems. With increasing interest in nanoscale and nano-bio hybrid materials, flexoelectricity will continue to gain prominence. This Review summarizes work in this area. First, methods to amplify or manipulate the flexoelectric effect to enhance material properties will be investigated, particularly at nanometer scales. Next, the nature and history of these effects in soft biomaterials will be explored. Finally, some theoretical interpretations for the effect will be presented. Overall, flexoelectricity represents an exciting phenomenon which is expected to become more considerable as materials continue to shrink. PMID:23293034

Nguyen, Thanh D; Mao, Sheng; Yeh, Yao-Wen; Purohit, Prashant K; McAlpine, Michael C

2013-01-06

57

Nanoscale Proteomics  

SciTech Connect

This paper describes efforts to develop a liquid chromatography (LC)/mass spectrometry (MS) technology for ultra-sensitive proteomics studies, i.e. nanoscale proteomics. The approach combines high-efficiency nano-scale LC with advanced MS, including high sensitivity and high resolution Fourier transform ion cyclotron resonance (FTICR) MS, to perform both single-stage MS and tandem MS (MS/MS) proteomic analyses. The technology developed enables large-scale protein identification from nanogram size proteomic samples and characterization of more abundant proteins from sub-picogram size complex samples. Protein identification in such studies using MS is feasible from <75 zeptomole of a protein, and the average proteome measurement throughput is >200 proteins/h and ~3 h/sample. Higher throughput (>1000 proteins/h) and more sensitive detection limits can be obtained using a “accurate mass and time” tag approach developed at our laboratory. These capabilities lay the foundation for studies from single or limited numbers of cells.

Shen, Yufeng; Tolic, Nikola; Masselon, Christophe D.; Pasa-Tolic, Liljiana; Camp, David G.; Anderson, Gordon A.; Smith, Richard D.; Lipton, Mary S.

2004-02-01

58

Nanoscale surface chemistry  

PubMed Central

We report evidence in several experiments for nanometer-size effects in surface chemistry. The evidence concerns bimetallic systems, monolayer films of Pt or Pd on W(111) surfaces. Pyramidal facets with {211} faces are formed on annealing on physical monolayer of Pt, Pd on a W(111) substrate, and facet sizes increase with annealing temperature. We used synchrotron radiation-based soft x-ray photoemission to show that monolayer films of Pt, Pd, on W “float” on the outer surface, whereas multilayer films form alloys on annealing. Acetylene reactions over bimetallic planar and faceted Pd/W surfaces exhibit size effects on the nanometer scale, that is, thermal desorption spectra of reactively formed benzene and ethylene (after acetylene adsorption) change systematically with facet size. In the second case, the decomposition of C2H2 over planar and faceted Ir(210) surfaces also exhibits structure sensitivity; temperature programmed desorption of H2 from C2H2 dissociation depends on the nanoscale surface structure. Finally, we have characterized interactions of Cu with the highly ordered S(4 × 4)/W(111) surface. The substrate is a sulfur-induced nanoscale reconstruction of W(111) with (4 × 4) periodicity, having broad planar terraces (?30 nm in width). Fractional monolayers of vapor-deposited Cu grow as threedimensional clusters on the S(4 × 4) surface over a wide coverage range. At low Cu coverage (? 0.1 ML), Cu nanoclusters nucleate preferentially at characteristic 3-fold hollow sites; we find a clear energetic preference for one type of site over others, and evidence for self-limiting growth of nanoclusters.

Madey, Theodore E.; Pelhos, Kalman; Wu, Qifei; Barnes, Robin; Ermanoski, Ivan; Chen, Wenhua; Kolodziej, Jacek J.; Rowe, John E.

2002-01-01

59

Thermal conduction in graphene and graphene multilayers  

Microsoft Academic Search

There has been increasing interest in thermal conductivity of materials motivated by the heat removal issues in electronics and by the need of fundamental science to understand heat conduction at nanoscale [1, 2, 3]. This dissertation reports the results of the experimental investigation of heat conduction in graphene and graphene multilayers. Graphene is a planar single sheet of sp2-bonded carbon

Suchismita Ghosh

2009-01-01

60

Structure of gradient coatings deposited by CAE-PVD techniques  

Microsoft Academic Search

Purpose: The main aim of this research was investigation of the gradient and multicomponent coatings structure deposited by cathode arc evaporation physical vapor deposition (CAE-PVD) on a SiAlON substrate. Design\\/methodology\\/approach: The structure of investigated coatings was characterized by scanning and transmission electron microscopy. Chemical composition was determined by energy dispersive spectroscopy (EDS) method. Investigation of surface roughness was done. Findings:

L. A. Dobrza?ski a; M. Staszuk; J. Konieczny; J. Lel?tko b

61

EDITORIAL: Nanoscale metrology Nanoscale metrology  

NASA Astrophysics Data System (ADS)

This special issue of Measurement Science and Technology presents selected contributions from the NanoScale 2010 seminar held in Brno, Czech Republic. It was the 5th Seminar on Nanoscale Calibration Standards and Methods and the 9th Seminar on Quantitative Microscopy (the first being held in 1995). The seminar was jointly organized with the Czech Metrology Institute (CMI) and the Nanometrology Group of the Technical Committee-Length of EURAMET. There were two workshops that were integrated into NanoScale 2010: first a workshop presenting the results obtained in NANOTRACE, a European Metrology Research Project (EMRP) on displacement-measuring optical interferometers, and second a workshop about the European metrology landscape in nanometrology related to thin films, scanning probe microscopy and critical dimension. The aim of this workshop was to bring together developers, applicants and metrologists working in this field of nanometrology and to discuss future needs. For more information see www.co-nanomet.eu. The articles in this special issue of Measurement Science and Technology cover some novel scientific results. This issue can serve also as a representative selection of topics that are currently being investigated in the field of European and world-wide nanometrology. Besides traditional topics of dimensional metrology, like development of novel interferometers or laser stabilization techniques, some novel interesting trends in the field of nanometrology are observed. As metrology generally reflects the needs of scientific and industrial research, many research topics addressed refer to current trends in nanotechnology, too, focusing on traceability and improved measurement accuracy in this field. While historically the most studied standards in nanometrology were related to simple geometric structures like step heights or 1D or 2D gratings, now we are facing tasks to measure 3D structures and many unforeseen questions arising from interesting physical properties of nanoparticles, nanotubes, quantum dots and similar fascinating objects. Currently there is a high level of interest in characterization of nanoparticles since they are increasingly encountered in science, technology, life sciences and even everyday life. Quantitative characterization of nanoparticles has been the subject of many discussions and some recent work over the last couple of years, and both scanning probe microscopy and scanning or transmission electron microscopy characterization of nanoparticles are presented here. There is also a continuous need for improvement of scanning probe microscopy that is a basic tool for nanometrology. Increasing thermal stability, scanning speed and tip stability, improving traceability and reducing uncertainty are all areas being addressed. As scanning probe microscopy is essentially based on force measurements in the nano- and piconewton range, we take notice of large developments, both theoretical and experimental, in the field of traceable measurements of nanoscale forces. This will greatly increase the understanding and quantification of many basic phenomena in scanning probe microscopy. Finally, we observe that high resolution techniques for acquiring more than just morphology are slowly shifting from purely qualitative tools to well defined quantitative methods. Lack of simple and reliable chemical identification in scanning probe microscopy is compensated by many other local probing methods seen in commercial microscopes, like scanning thermal microscopy or the Kelvin probe technique. All these methods still require underpinning with theoretical and experimental work before they can become traceable analytical methods; however, the increased interest in the metrology community gives rise to optimism in this field. The production of this issue involved considerable effort from many contributors. We would like to thank all the authors for their contributions, the referees for their time spent reviewing the contributions and their valuable comments, and the whole Editorial Board of Measurement Science and Tec

Klapetek, P.; Koenders, L.

2011-09-01

62

EDITORIAL: Nanoscale metrology Nanoscale metrology  

NASA Astrophysics Data System (ADS)

Instrumentation and measurement techniques at the nanoscale play a crucial role not only in extending our knowledge of the properties of matter and processes in nanosciences, but also in addressing new measurement needs in process control and quality assurance in industry. Micro- and nanotechnologies are now facing a growing demand for quantitative measurements to support the reliability, safety and competitiveness of products and services. Quantitative measurements presuppose reliable and stable instruments and measurement procedures as well as suitable calibration artefacts to ensure the quality of measurements and traceability to standards. This special issue of Measurement Science and Technology presents selected contributions from the Nanoscale 2008 seminar held at the Istituto Nazionale di Ricerca Metrologica (INRIM), Torino, in September 2008. This was the 4th Seminar on Nanoscale Calibration Standards and Methods and the 8th Seminar on Quantitative Microscopy (the first being held in 1995). The seminar was jointly organized by the Nanometrology Group within EUROMET (The European Collaboration in Measurement Standards), the German Nanotechnology Competence Centre 'Ultraprecise Surface Figuring' (CC-UPOB), the Physikalisch-Technische Bundesanstalt (PTB) and INRIM. A special event during the seminar was the 'knighting' of Günter Wilkening from PTB, Braunschweig, Germany, as the 1st Knight of Dimensional Nanometrology. Günter Wilkening received the NanoKnight Award for his outstanding work in the field of dimensional nanometrology over the last 20 years. The contributions in this special issue deal with the developments and improvements of instrumentation and measurement methods for scanning force microscopy (SFM), electron and optical microscopy, high-resolution interferometry, calibration of instruments and new standards, new facilities and applications including critical dimension (CD) measurements on small and medium structures and nanoparticle characterization. The papers in the first part report on new or improved instrumentation, details of developments of metrology SFM, improvements to SFM, probes and scanning methods in the direction of nanoscale coordinate measuring machines and true 3D measurements as well as of progress of a 2D encoder based on a regular crystalline lattice. To ensure traceability to the SI unit of length many highly sophisticated instruments are equipped with laser interferometers to measure small displacements in the nanometre range very accurately. Improving these techniques is still a challenge and therefore new interferometric techniques are considered in several papers as well as improved sensors for nanodisplacement measurements or the development of a deep UV microscope for micro- and nanostructures. The tactile measurement of small structures also calls for a better control of forces in the nano- and piconewton range. A nanoforce facility, based on a disk-pendulum with electrostatic stiffness reduction and electrostatic force compensation, is presented for the measurement of small forces. In the second part the contributions are related to calibration and correction strategies and standards such as the development of test objects based on 3D silicon structures, and of samples with irregular surface profiles, and their use for calibration. The shape of the tip and its influence on measurements is still a contentious issue and addressed in several papers: use of nanospheres for tip characterization, a geometrical approach for reconstruction errors by tactile probing. Molecular dynamical calculations, classical as well as ab initio (based on density functional theory), are used to discuss effects of tip-sample relaxation on the topography and to have a better base from which to estimate uncertainties in measurements of small particles or features. Some papers report about measurements of air refractivity fluctuations by phase modulation interferometry, angle-scale traceability by laser diffractometry, and an error separation method. The development of 3D surface roughness measurem

Picotto, G. B.; Koenders, L.; Wilkening, G.

2009-08-01

63

Macroscale vs. Nanoscale  

NSDL National Science Digital Library

In this colorful, interactive object, learners examine how materials on the nanoscale compare with those on the macroscale. The focus is on the difference between macroscale and nanoscale gold in both color and melting point.

2010-11-23

64

Multilayer Tube.  

National Technical Information Service (NTIS)

The multilayer tube, including external concrete shell connected by adhesive with the inner core of cast stone is distinguished by the fact that to increase the strength, and the core is made with longitudinal prestressed reinforcement placed uniformly al...

A. E. Shumurnov B. N. Ulyanov V. S. Panasyuk Z. M. Burdenkova

1973-01-01

65

Formation of CdSe/CdTe quantum dots in multilayer thin films using PVD method  

NASA Astrophysics Data System (ADS)

Nanocrystals of CdSe have been produced in CdTe hetrostructure layer by thermal evaporation method. Structural studies were done by X-ray diffractometer. Quantum confinement effect of CdSe/CdTe nanocrystals was analysed from optical studies. Bulk CdSe has a bandgap energy of 1.756eV that can be shifted to larger values by reducing the crystal size to dimensions smaller than the Bohr radius of the exciton. Experimentally measured band gap shifts with respect to the bulk value for quantum dot thin films are compared with the predictions of the effective mass approximation model (i.e., Brus model) and Quantum mechanical model. Size of the crystallites calculated from both the models was found to agree with each other.

Kumar, M. Melvin David; Devadason, Suganthi; Rajesh, S.

2012-06-01

66

Nanoscale thermal probing  

PubMed Central

Nanoscale novel devices have raised the demand for nanoscale thermal characterization that is critical for evaluating the device performance and durability. Achieving nanoscale spatial resolution and high accuracy in temperature measurement is very challenging due to the limitation of measurement pathways. In this review, we discuss four methodologies currently developed in nanoscale surface imaging and temperature measurement. To overcome the restriction of the conventional methods, the scanning thermal microscopy technique is widely used. From the perspective of measuring target, the optical feature size method can be applied by using either Raman or fluorescence thermometry. The near-field optical method that measures nanoscale temperature by focusing the optical field to a nano-sized region provides a non-contact and non-destructive way for nanoscale thermal probing. Although the resistance thermometry based on nano-sized thermal sensors is possible for nanoscale thermal probing, significant effort is still needed to reduce the size of the current sensors by using advanced fabrication techniques. At the same time, the development of nanoscale imaging techniques, such as fluorescence imaging, provides a great potential solution to resolve the nanoscale thermal probing problem.

Yue, Yanan; Wang, Xinwei

2012-01-01

67

Hierarchical adaptive nanostructured PVD coatings for extreme tribological applications: the quest for nonequilibrium states and emergent behavior  

NASA Astrophysics Data System (ADS)

Adaptive wear-resistant coatings produced by physical vapor deposition (PVD) are a relatively new generation of coatings which are attracting attention in the development of nanostructured materials for extreme tribological applications. An excellent example of such extreme operating conditions is high performance machining of hard-to-cut materials. The adaptive characteristics of such coatings develop fully during interaction with the severe environment. Modern adaptive coatings could be regarded as hierarchical surface-engineered nanostructural materials. They exhibit dynamic hierarchy on two major structural scales: (a) nanoscale surface layers of protective tribofilms generated during friction and (b) an underlying nano/microscaled layer. The tribofilms are responsible for some critical nanoscale effects that strongly impact the wear resistance of adaptive coatings. A new direction in nanomaterial research is discussed: compositional and microstructural optimization of the dynamically regenerating nanoscaled tribofilms on the surface of the adaptive coatings during friction. In this review we demonstrate the correlation between the microstructure, physical, chemical and micromechanical properties of hard coatings in their dynamic interaction (adaptation) with environment and the involvement of complex natural processes associated with self-organization during friction. Major physical, chemical and mechanical characteristics of the adaptive coating, which play a significant role in its operating properties, such as enhanced mass transfer, and the ability of the layer to provide dissipation and accumulation of frictional energy during operation are presented as well. Strategies for adaptive nanostructural coating design that enhance beneficial natural processes are outlined. The coatings exhibit emergent behavior during operation when their improved features work as a whole. In this way, as higher-ordered systems, they achieve multifunctionality and high wear resistance under extreme tribological conditions.

Fox-Rabinovich, German S.; Yamamoto, Kenji; Beake, Ben D.; Gershman, Iosif S.; Kovalev, Anatoly I.; Veldhuis, Stephen C.; Aguirre, Myriam H.; Dosbaeva, Goulnara; Endrino, Jose L.

2012-08-01

68

Mechanical behaviour of PVD- and CVD-coated hard metals under cyclic loads  

Microsoft Academic Search

The aim of this work is to investigate the influence of different coating processes and layer systems on the mechanical properties of hard metals. A WC–(Ti,Ta,Nb,W)C–Co hard metal was coated by PVD (physical vapour deposition) and HTCVD (high temperature chemical vapour deposition). The PVD coating consisted of 3 ?m TiN and the CVD coatings of 9 ?m TiN-Ti(C,N)-TiN. The mechanical

P Schlund; P Kindermann; H.-G Sockel; U Schleinkofer; W Heinrich; K Görting

1999-01-01

69

Electrospun PVdF-based fibrous polymer electrolytes for lithium ion polymer batteries  

Microsoft Academic Search

This paper discusses the preparation of microporous fibrous membranes from PVdF solutions with different polymer contents, using the electrospinning technique. Electrospun PVdF-based fibrous membranes with average fiber diameters (AFD's) of 0.45–1.38?m have an apparent porosity and a mean pore size (MPS) of 80–89% and 1.1–4.3?m, respectively. They exhibited a high uptake of the electrolyte solution (320–350%) and a high ionic

Jeong Rae Kim; Sung Won Choi; Seong Mu Jo; Wha Seop Lee; Byung Chul Kim

2004-01-01

70

The influence of humidity on the fretting behaviour of PVD TiN coatings  

Microsoft Academic Search

The influence of the relative humidity (RH) in ambient air on the friction and wear behaviour of PVD TiN coatings subjected to contact vibrations against corundum and bearing steel (100Cr6) counterbodies has been investigated. The fretting experiments were performed in the gross-slip regime on TiN coatings produced by three different PVD processes. The results indicate two basic friction characteristics. At

H. Mohrbacher; B. Blanpain; J.-P. Celis; J. R. Roos

1995-01-01

71

PVD coating for optical applications on temperature-resistant thermoplastics  

NASA Astrophysics Data System (ADS)

The performance of the high temperature resistant polymers Pleximid, APEC and Ultrason as substrate materials in plasma-assisted physical vapor deposition processes was studied and compared with well-known thermoplastics for optical applications. Different effects of UV irradiation and plasma exposure on the polymers' optical features, surface energy and adhesion properties for oxide layers, typically used for interference multilayer coatings, are shown.

Munzert, Peter; Schulz, Ulrike; Kaiser, Norbert

2004-02-01

72

Nanoscale construction with DNA  

NASA Astrophysics Data System (ADS)

The programmability of DNA makes it an attractive material for constructing intricate nanoscale shapes. One method for creating these structures is DNA origami, in which a multiple-kilobase single-stranded ``scaffold'' is folded into a custom nanoscale shape by interacting with hundreds of short oligonucleotide ``staple'' strands. I will talk about our efforts to realize demand-meeting applications of this method, including our recent development of nanoscale devices to mimic cell-signaling stimulation carried out by our own immune systems.

Douglas, Shawn

2013-03-01

73

Role of PvdQ in Pseudomonas aeruginosa virulence under iron-limiting conditions.  

PubMed

PvdQ, an acylase from Pseudomonas aeruginosa PAO1, has been shown to have at least two functions. It can act as a quorum quencher due to its ability to degrade long-chain N-acylhomoserine lactones (AHLs), e.g. 3-oxo-C12-HSL, leading to a decrease in virulence factors. In addition, PvdQ is involved in iron homeostasis by playing a role in the biosynthesis of pyoverdine, the major siderophore of P. aeruginosa. In accordance with earlier studies on RNA level, we could show at the protein level that PvdQ is only expressed when iron is present at very low concentrations. We therefore set out to investigate the two functions of PvdQ under iron-limiting conditions. Gene deletion of pvdQ does not affect growth of P. aeruginosa but abrogates pyoverdine production, and results in an accumulation of 3-oxo-C12-HSL. Phenotypic analyses of our DeltapvdQ mutant at low iron concentrations revealed that this mutant is impaired in swarming motility and biofilm formation. Additionally, a plant and a Caenorhabditis elegans infection model demonstrated that the deletion of pvdQ resulted in reduced virulence. None of the phenotypes in the present study could be linked to the presence or absence of AHLs. These results clearly indicate that under iron-limiting conditions PvdQ plays a major role in swarming motility, in biofilm development and in infection that is more likely to be linked to the pyoverdine pathway rather than the LasI/LasR/3-oxo-C12-HSL quorum-sensing circuit. PMID:19778968

Nadal Jimenez, Pol; Koch, Gudrun; Papaioannou, Evelina; Wahjudi, Mariana; Krzeslak, Joanna; Coenye, Tom; Cool, Robbert H; Quax, Wim J

2009-09-24

74

Nanoscale Transport Optimization.  

National Technical Information Service (NTIS)

A generalized modeling tool has been created that facilitates virtual design of active material systems utilizing nanoscale transport. The construct is bio-mimetic in that the stochastic nature of biological transport proteins is utilized as the basis for...

L. M. Weiland

2008-01-01

75

Corrosion properties of nitride, oxide and multilayer coatings on stainless steel and titanium-based substrates  

NASA Astrophysics Data System (ADS)

A comparative analysis is made of the parameters of oxide, nitride and multilayer coatings, such as TiN, deposited by means of Arc-PVD, oxide Al2O3 films deposited by magnetron sputtering (MS), and of multilayer TiN/Al2O3 on stainless steel (1H18N9) and a titanium-based material (Ti4Al6V). The corrosion examinations of anodic polarization by potentiodynamic method, Tafel and Stern curves and also impedance method at NaCl and SBF solutions were presented. The best corrosion resistance characteristics are exhibited by TiN/Al2O3 multilayer coatings on both stainless steel and titanium substrates.

Zykova, A.; Safonov, V.; Walkowich, J.; Rogowska, R.; Yakovin, S.

2010-04-01

76

Pyoverdine-Mediated Iron Uptake in Pseudomonas aeruginosa: the Tat System Is Required for PvdN but Not for FpvA Transport  

Microsoft Academic Search

Under iron-limiting conditions, Pseudomonas aeruginosa PAO1 secretes a fluorescent siderophore called pyoverdine (Pvd). After chelating iron, this ferric siderophore is transported back into the cells via the outer membrane receptor FpvA. The Pvd-dependent iron uptake pathway requires several essential genes involved in both the synthesis of Pvd and the uptake of ferric Pvd inside the cell. A previous study describing

R. Voulhoux; A. Filloux; I. J. Schalk

2006-01-01

77

Integrated arc suppression unit for defect reduction in PVD applications  

NASA Astrophysics Data System (ADS)

Arcing between the target and plasma during PVD deposition causes substantial damage to the target and splats and other contamination on the deposited films. Arc-related damages and defects are frequently encountered in microelectronics manufacturing and contributes largely to reduced wafer yields. Arcing is caused largely by the charge buildup at the contaminated sites on the target surface that contains either nonconducting inclusions or nodules. Arc suppression is a key issue for defect reduction, yield improvement and for reliable high quality metallization. An Integrated Arc Suppression Unit (IASU) has been designed for Endura HP PVDTM sputtering sources. The integrated design reduces cable length from unit to source and reduces electrical energy stored in the cable. Active arc handling mode, proactive arc prevention mode, and passive by-pass arc counting mode are incorporated into the same unit. The active mode is designed to quickly respond to chamber conditions, like a large chamber voltage drop, that signals a arc. The self run mode is designed to proactively prevent arc formation by pulsing and reversing target voltage at 50 kHz. The design of the IASU, also called mini small package arc repression circuit--low energy unit (mini Sparc-le), has been optimized for various DC magnetron sources, plasma stability, chamber impedance, power matching, CE MARK test, and power dissipation. Process characterization with Ti, TiN and Al sputtering indicates that the unit has little adverse impact on film properties. Mini Sparc-le unit has been shown here to significantly reduce splats occurrence in Al sputtering. Marathon test of the unit with Ti/TiN test demonstrated the unit's reliability and its ability to reduce sensitivity of defects to target characteristics.

Li, Xiangbing; Narasimhan, Murali K.; Pavate, Vikram; Loo, David; Rosenblum, Steve; Trubell, Larry; Scholl, Richard; Seamons, Scott; Hagerty, Chris; Ramaswami, Sesh

1997-09-01

78

Nanotube TiO 2 composite PVdF\\/LiPF 6 solid membranes  

Microsoft Academic Search

Nano-tube TiO2 enhances ion conductivity of poly (vinyldene fluoride) (PVdF)\\/LiPF6 polymer electrolyte. Complexation structure and the lithium ion conductivity of the composite are examined. The X-ray photoelectron spectroscopy (XPS) C1s and F1s spin–orbital splitting photoelectrons spectrum of pure PVdF change enormously with the addition of the lithium salt and nano-tube TiO2. The results are consistent with a structure that the

Chin-Yeh Chiang; M. Jaipal Reddy; Peter P. Chu

2004-01-01

79

Characterization of Mo/Si multilayer growth on stepped topographies  

SciTech Connect

Mo/Si multilayer mirrors with nanoscale bilayer thicknesses have been deposited on stepped substrate topographies, using various deposition angles. The multilayer morphology at the stepedge region was studied by cross section transmission electron microscopy. A transition from a continuous- to columnar layer morphology is observed near the step-edge, as a function of the local angle of incidence of the deposition flux. Taking into account the corresponding kinetics and anisotropy in layer growth, a continuum model has been developed to give a detailed description of the height profiles of the individual continuous layers. Complementary optical characterization of the multilayer system using a microscope operating in the extreme ultraviolet wavelength range, revealed that the influence of the step-edge on the planar multilayer structure is restricted to a region within 300 nm from the step-edge.

Boogaard, A. J. R. vcan den; Louis, E.; Zoethout, E.; Goldberg, K. A.; Bijkerk, F.

2011-08-31

80

Processing, microstructure and mechanical behavior of nanocomposite multilayers  

NASA Astrophysics Data System (ADS)

Nanoscale multilayer coatings have high potential for numerous engineering applications because they can combine different properties from individual components. At present, scale effects on the mechanical behavior of multilayers are not well understood. Three multilayer systems, namely Al/Al 2O3, Ti/TiN, and Cr/a-C, have been synthesized by using a dual-gun e-beam physical vapor deposition, to investigate the relationship between the nature of components, their microstructures, and mechanical behavior. The deposited Al and Ti nanolayers were found to have polycrystalline fcc and hcp structure, respectively, the Cr and TiN layers had fine columnar bcc and fcc structure, respectively, and the Al2O3 and C layers were amorphous. Nanoscale effects were observed in all three systems with the metal layer thickness affecting significantly the mechanical behavior. The hardness response of the present systems can be described as a function of the metal layer thickness by a Hall-Petch relationship. A critical Al layer thickness of 40 nm, below which there was no further hardness enhancement, was found for the Al/Al2O3 multilayers. The critical Al layer thickness could be predicted by previous theoretical models. A hardness increase was observed down to a Ti layer thickness of 5 nm for the Ti/TiN system. The strengthening of the Ti/TiN multilayers was consistent with the macroyield maps based on a confined layer slip model. Hardness in the Cr/ a-C system showed a continuous increase down to a Cr layer thickness of 20 nm. The fracture toughness of the ceramic was significantly improved by introducing a metal/ceramic multilayered structure. The wear behavior of the present multilayers was mainly controlled by the ceramic phase. The Cr/ a-C multilayers achieved a low friction coefficient (˜0.1) and low wear rate (˜10-5 mm3/N m).

Qi, Zuqiang

81

Magnetic multilayers on nanospheres.  

NASA Astrophysics Data System (ADS)

In modern magnetic recording materials the `superparamagnetic effect' [1] has become increasingly important as new magnetic hard disk drive products are designed for higher storage densities. In this regard, nanoparticle media [2], where two-dimensional arrays of monodisperse nanoparticles with high magnetic anisotropy are used, is assumed to be the ideal future magnetic recording material. In this presentation a novel magnetic gradient nanomaterial, which has been created by depositing Co/Pd multilayers onto two-dimensional arrays of self-assembled nanoparticles [3] will be introduced. The magnetic nanostructures formed on top of the particles are in a magnetically exchange-isolated quasi-single-domain state. This nanoscale system is quite distinct from the classical geometries: Neither extrinsic properties nor the intrinsic properties are uniform in space. The film is extended over a wide region of the sphere and thus shows substantial curvature. The film thickness varies and so do the intrinsic magnetic properties most notable the magneto-crystalline anisotropy, which is a key factor affecting the fundamental nature of the reversal process. The specific magnetic characteristics of such a gradient nanomaterial and in particular its impact on the reversal mechanism will be discussed. Angle-dependent reversal studies were performed for different particle sizes and the experimental results were interpreted using micromagnetic simulations. The simulations account for the angular dependence of the hysteresis loops and provide a detailed picture of how the local magnetization evolves during reversal, offering new opportunities in the functionalization of magnetic nanostructures for storage applications. [1] A. Moser et al., J. Phys. D: Appl. Phys. 35, (2002) R157. [2] S. Sun et al., Science 87, (2000) 1989. [3] M. Albrecht et al., Nature Mater. 4, (2005) 203.

Albrecht, Manfred

2006-03-01

82

Thermal stability of sputtered Cu/304 stainless steel multilayer films  

NASA Astrophysics Data System (ADS)

We report on the thermal stability of sputter-deposited Cu/304 stainless steel nanoscale multilayer films. For individual layer thickness of approximately 70 nm, the layered morphology was stable up to 600 °C with no significant change in the hardness. The stainless steel layer had a duplex bcc+fcc structure that was also preserved in annealed films. After annealing at temperatures of 650 °C or higher, the hardness of these multilayer films decreased from 4.75 to 3.4 GPa due to morphological evolution from layers to equiaxed grains and coarsening of the nanolayers.

Zhang, X.; Schulze, R. K.; Wang, H.; Misra, A.

2007-06-01

83

Electrical Properties of Gamma Irradiated PVdF Based Polymer Electrolytes  

SciTech Connect

The effect of different doses of {gamma}-irradiation on the conductivity of PVdF-LiPF{sub 6} solid polymer electrolyte (SPE) was investigated at room temperature. The dielectric constant and loss are seen to increase with increasing radiation doses.

Ayoub, N.; Amin, Y. M.; Arof, A. K. [Physics Department, University of Malaya, 50603 Kuala Lumpur (Malaysia)

2010-07-07

84

Nanoscale thermal transport  

Microsoft Academic Search

Rapid progress in the synthesis and processing of materials with structure on nanometer length scales has created a demand for greater scientific understanding of thermal transport in nanoscale devices, individual nanostructures, and nanostructured materials. This review emphasizes developments in experiment, theory, and computation that have occurred in the past ten years and summarizes the present status of the field. Interfaces

David G. Cahill; Wayne K. Ford; Kenneth E. Goodson; Gerald D. Mahan; Arun Majumdar; Humphrey J. Maris; Roberto Merlin; Simon R. Phillpot

2003-01-01

85

Dielectrophoresis at the nanoscale.  

PubMed

Dielectrophoresis has become a powerful tool for manipulation of various materials, such as metal and semiconducting particles, DNA molecules, nanowires and graphene. This short review is intended to provide the reader with an overview of the recent advances of application of dielectrophoresis at the nanoscale. PMID:21800329

Kuzyk, Anton

2011-07-29

86

Nanoscale Magnetic Structure of Ferromagnet/Antiferromagnet Manganite Multilayers  

SciTech Connect

We use polarized neutron reflectometry and dc magnetometry to obtain a comprehensive picture of the magnetic structure of a series of La{sub 2/3}Sr{sub 1/3}MnO{sub 3}/Pr{sub 2/3}Ca{sub 1/3}MnO{sub 3} (LSMO/PCMO) superlattices, with varying thickness of the antiferromagnetic (AFM) PCMO layers (0{<=}t{sub A}{<=}7.6 nm). While LSMO presents a few magnetically frustrated monolayers at the interfaces with PCMO, in the latter a magnetic contribution due to ferromagnetic (FM) inclusions within the AFM matrix is maximized at t{sub A}{approx}3 nm. This enhancement of FM moment occurs at the matching between layer thickness and cluster size, implying the possibility of tuning phase separation by imposing appropriate geometrical constraints which favor the accommodation of FM nanoclusters within the ''non-FM'' material.

Niebieskikwiat, D. [Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States); Colegio de Ciencias e Ingenieria, Universidad San Francisco de Quito, Quito (Ecuador); Hueso, L. E. [Department of Materials Science, University of Cambridge, Cambridge CB2 3QZ (United Kingdom); Department of Physics and Astronomy, University of Leeds, Leeds LS2 9JT (United Kingdom); Borchers, J. A. [NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); Mathur, N. D. [Department of Materials Science, University of Cambridge, Cambridge CB2 3QZ (United Kingdom); Salamon, M. B. [Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States)

2007-12-14

87

Tunable nanoscale graphene magnetometers.  

PubMed

The detection of magnetic fields with nanoscale resolution is a fundamental challenge for scanning probe magnetometry, biosensing, and magnetic storage. Current technologies based on giant magnetoresistance and tunneling magnetoresistance are limited at small sizes by thermal magnetic noise and spin-torque instability. These limitations do not affect Hall sensors consisting of high mobility semiconductors or metal thin films, but the loss of magnetic flux throughout the sensor's thickness greatly limits spatial resolution and sensitivity. Here we demonstrate graphene extraordinary magnetoresistance devices that combine the Hall effect and enhanced geometric magnetoresistance, yielding sensitivities rivaling that of state of the art sensors but do so with subnanometer sense layer thickness at the sensor surface. Back-gating provides the ability to control sensor characteristics, which can mitigate both inherent variations in material properties and fabrication-induced device-to-device variability that is unavoidable at the nanoscale. PMID:20030395

Pisana, Simone; Braganca, Patrick M; Marinero, Ernesto E; Gurney, Bruce A

2010-01-01

88

Excitons in nanoscale systems.  

PubMed

Nanoscale systems are forecast to be a means of integrating desirable attributes of molecular and bulk regimes into easily processed materials. Notable examples include plastic light-emitting devices and organic solar cells, the operation of which hinge on the formation of electronic excited states, excitons, in complex nanostructured materials. The spectroscopy of nanoscale materials reveals details of their collective excited states, characterized by atoms or molecules working together to capture and redistribute excitation. What is special about excitons in nanometre-sized materials? Here we present a cross-disciplinary review of the essential characteristics of excitons in nanoscience. Topics covered include confinement effects, localization versus delocalization, exciton binding energy, exchange interactions and exciton fine structure, exciton-vibration coupling and dynamics of excitons. Important examples are presented in a commentary that overviews the present understanding of excitons in quantum dots, conjugated polymers, carbon nanotubes and photosynthetic light-harvesting antenna complexes. PMID:16946728

Scholes, Gregory D; Rumbles, Garry

2006-09-01

89

DNA in Nanoscale Electronics  

NASA Astrophysics Data System (ADS)

DNA, the quintessential molecule of life, possesses a number of attractive properties for use in nanoscale circuits. Charge transport (CT) through DNA itself is of both fundamental and practical interest. Fundamentally, DNA has a unique configuration of ?-stacked bases in a well ordered, double helical structure. Given its unparalleled importance to life processes and its arrangement of conjugated subunits, DNA has been a compelling target of conductivity studies. In addition, further understanding of DNA CT will elucidate the biological implications of this process and advance its use in sensing technologies. We have investigated the fundamentals of DNA CT by measuring the electrochemistry of DNA monolayers under biologically-relevant conditions. We have uncovered both fundamental kinetic parameters to distinguish between competing models of operation as well as the practical implications of DNA CT for sensing. Furthermore, we are leveraging our studies of DNA conductivity for the manufacture of nanoscale circuits. We are investigating the electrical properties and self-assembly of DNA nanowires containing artificial base pair surrogates, which can be prepared through low cost and high throughput automated DNA synthesis. This unique and economically viable approach will establish a new paradigm for the scalable manufacture of nanoscale semiconductor devices.

Slinker, Jason

2012-10-01

90

Study on the role of PVD TiN coating in improving the performance of electroplated monolayer superabrasive wheel  

Microsoft Academic Search

The monolayer grinding wheels, coated with a physical vapour deposited (PVD) coating (viz. TiN, HfN, TiN+ZrN etc.), have been reported to outperform their uncoated counterparts as claimed in some patented literatures. The present work aims at exploring the mechanism how PVD TiN augments the performance of nickel electroplated monolayer superabrasive wheels. This study also includes the effect of negative substrate

D. Bhaduri; A. K. Chattopadhyay

2010-01-01

91

Nano-impact test on a TiAlN PVD coating and correlation between experimental and FEM results  

Microsoft Academic Search

Nano-impact test on PVD coatings is an efficient method for investigating film failure mechanisms. During this test, the coating is subjected to repetitive impacts by a diamond indenter, inducing high local deformations and stresses into the film material, which may lead to coating failure.In the paper, coated specimens with a TiAlN PVD film were investigated by nano-impact tests. The nano-impacts

K.-D. Bouzakis; S. Gerardis; G. Skordaris; E. Bouzakis

92

Preparation of porous, chemically cross-linked, PVdF-based gel polymer electrolytes for rechargeable lithium batteries  

Microsoft Academic Search

This study reports the development of a new system of porous, chemically cross-linked, gel polymer electrolytes based on poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF–HFP) copolymer as a polymer matrix, polyethylene glycol (PEG) as a plasticizer, and polyethylene glycol dimethacrylate (PEGDMA) as a chemical cross-linking oligomer. The electrolytes are prepared by a combination of controlled evaporation and thermal polymerization of PEGDMA. PVdF–HFP\\/PEG\\/PEGDMA gel polymer

C. L Cheng; C. C Wan; Y. Y Wang

2004-01-01

93

Enhancement of the punch pin durability induced by the PVD coating in production process of the automotive inner pipe  

Microsoft Academic Search

This experimental studies were carried out in order to understand the effects of the PVD coating and the UNSM treatment of\\u000a HSS55 (high speed steel 55) during the production of the automotive inner pipe by the plastic deformation of S45C. The field\\u000a test and the SEM images revealed that the PVD coating is necessary in spite of the high compressive

Chang-Min Suh; Sang-Yeob Oh; Young-Sik Pyun

2010-01-01

94

Rechargeable lithium battery employing a new ambient temperature hybrid polymer electrolyte based on PVK+PVdF–HFP (copolymer)  

Microsoft Academic Search

We describe here for the first time, our recent success in developing an ambient temperature Li+ conducting solid polymer electrolyte (SPE) using the concept of polymer alloying upon blending two thermoplastic polymers such as poly(vinylidene) fluoride-hexafluoropropylene (PVdF–HFP-copolymer) and poly(N-vinylcarbazole), PVK and achieved the room temperature electrolytic conductivity (?i) of 0.7×10?3S\\/cm for a typical composition of PVdF–HFP copolymer\\/PVK blend mixed with

M. S. Michael; S. R. S. Prabaharan

2004-01-01

95

Pseudomonas aeruginosa pvdQ gene prevents Caco-2 cells from obstruction of quorum-sensing signal.  

PubMed

Quorum sensing (QS) system plays an important role in bacterial pathopoiesis of incurable Pseudomonas aeruginosa infection, which strongly warrants new strategies for absence of curative treatment to date. Latest investigations show that pvdQ gene of P. aeruginosa can attenuate the pathopoiesis of the bacteria by encoding acylase enzyme and hydrolyze N-(3-oxododecanoyl)-Homoserine Lactone (3O-oxo-C(12)-HSL), the key signal molecule of QS system. This study tries to resist the pathogenicity of P. aeruginosa by transfecting human intestinal epithelial Caco-2 cells with pvdQ gene. We found that 3O-oxo-C(12)-HSL was decreased in the supernatant of cells transfected with pvdQ gene. Moreover, the result of flow cytometry showed that the 3O-oxo-C(12)-HSL evoked apoptosis rate of Caco-2 cells was inhibited when the cells were transfected with pvdQ gene. In contrast, the control result displayed increased Caco-2 cells' apoptosis rate after stimulation of 3O-oxo-C(12)-HSL without protection of pvdQ gene. In conclusion, we successfully protect mammalian cells Caco-2 from injure of QS signal molecule 3O-oxo-C(12)-HSL through imputing pvdQ gene, which may suggest a new therapeutic strategy for P. aeruginosa infection. PMID:20490497

Ye, Lu; Li, Gaopeng; Li, Hongtao; Wang, Lili; Mao, Yan; Xie, Xuhua; Xia, Chao; Chen, Jia; Song, Jianxin

2010-05-19

96

Nanoscale ear drum: Graphene based nanoscale sensors  

NASA Astrophysics Data System (ADS)

The difficulty in determining the mass of a sample increases as its size diminishes. At the nanoscale, there are no direct methods for resolving the mass of single molecules or nanoparticles and so more sophisticated approaches based on electromechanical phenomena are required. More importantly, one demands that such nanoelectromechanical techniques could provide not only information about the mass of the target molecules but also about their geometrical properties. In this sense, we report a theoretical study that illustrates in detail how graphene membranes can operate as nanoelectromechanical mass-sensor devices. Wide graphene sheets were exposed to different types and amounts of molecules and molecular dynamic simulations were employed to treat these doping processes statistically. We demonstrate that the mass variation effect and information about the graphene-molecule interactions can be inferred through dynamical response functions. Our results confirm the potential use of graphene as a mass detector device with remarkable precision in estimating variations in mass at the molecular scale and other physical properties of the dopants.

Avdoshenko, Stas M.; Gomes da Rocha, Claudia; Cuniberti, Gianaurelio

2012-05-01

97

Microstructures and mechanical properties of sputtered Cu/Cr multilayers  

SciTech Connect

The microstructures and mechanical properties of Cu/Cr multilayers prepared by sputtering onto {l_brace}100{r_brace} Si substrates at room temperature are presented. The films exhibit columnar grain microstructures with nanoscale grain sizes. The interfaces are planar and abrupt with no intermixing, as expected from the phase diagram. The multilayers tend to adopt a Kurdjumov-Sachs (KS) orientation relationship: {l_brace}110{r_brace}Cr // {l_brace}111{r_brace}Cu, <111>Cr // <110>Cu. The hardness of the multilayered structures, as measured by nanoindentation, increase with decreasing layer thickness for layer thicknesses ranging from 200 nm to 50 nm, whereas for lower thicknesses the hardness of the multilayers is independent of the layer thickness. Dislocation-based models are used to interpret the variation of hardness with layer periodicity. The possible effects of factors such as grain size within the layers, density and composition of films and residual stress in the multilayers are highlighted. Comparisons are made to the mechanical properties of sputtered polycrystalline Cu/Nb multilayers which, like Cu/Cr, exhibit sharp fcc/bcc interfaces with no intermixing and a KS orientation relationship, but have a small shear modulus mismatch.

Misra, A.; Kung, H.; Mitchell, T.E.; Jervis, T.R.; Nastasi, M.

1998-03-01

98

The effect of PVD coatings on the wear behaviour of magnesium alloys  

SciTech Connect

In this study, AlN/TiN was coated on magnesium alloys using physical vapour deposition (PVD) technique of DC magnetron sputtering, and the influence of the coating on the wear behaviour of the alloys was examined. A physical vapour deposition system for coating processes, a reciprocating wear system for wear tests, a universal hardness equipment for hardness measurement, a X-ray diffractometer (XRD) for compositional analysis of the coating, and a scanning electron microscopy (SEM) for surface examinations were used. It was determined that the wear resistance of the magnesium alloys can be increased by PVD coatings. However, small structural defects which could arise from the coating process or substrate were observed in the coating layers.

Altun, Hikmet [Department of Mechanical Engineering, Ataturk University, 25240, Erzurum (Turkey)], E-mail: haltun@atauni.edu.tr; Sen, Sadri [Department of Mechanical Engineering, Ataturk University, 25240, Erzurum (Turkey)

2007-10-15

99

Stereometry specification of anodised and PVD coated surface of aluminium alloy  

Microsoft Academic Search

Purpose: The aim of the work is to present the influence of casting method and anodic treatment parameters on properties, thickness and structure of an anodic layer with (PVD) physical vapour deposition method achieved TiN layer formed on aluminum casting alloys. Design\\/methodology\\/approach: Investigations were carried out on the laser profile measurement gauge MicroProf from company FRT, abrasive wear test was

J. Konieczny; K. Labisz; J. Wieczorek; L. A. Dobrzañski

100

Experiments and modelling of combined PVD and CVD processes using a hollow cathode arc discharge plasma  

Microsoft Academic Search

A plasma-based deposition method was developed which allows the formation of non-metallic coatings with a graded metal interlayer to improve the substrate adhesion of the non-metallic coating. For this a plasma-enhanced PVD process was combined with a CVD process using a hollow cathode arc discharge plasma produced from a LaB6 cathode as thermal electron emitter. In the present experiments layers

H Bolt; A Buuron; F Koch; M Noethe

1998-01-01

101

Investigation of Ti and Cr based PVD coatings deposited onto HSS Co 5 twist drills  

NASA Astrophysics Data System (ADS)

Cr and Ti based coatings on HSS Co 5 substrates and drills were deposited by two PVD techniques.We obtained high hardness of about 35 GPa and good Mercedes adhesion up to HF1 grade.The Pin-on-disc test showed coefficient of friction from 0.48 to 0.87.Wear as the coating volume loss was calculated after the Pin-on-disc testing.Wear of coated and uncoated drills was tested in drilling hole operations.

Kottfer, D.; Ferdinandy, M.; Kaczmarek, L.; Ma?ková, I.; Be?o, J.

2013-10-01

102

PVD Coating of Mg–AZ31 by Thin Layer of Al and Al–Si  

Microsoft Academic Search

Although magnesium alloys have the advantage of high specific strength, they have poor atmospheric corrosion resistance. An\\u000a important method of improving the corrosion resistance is by applying a coating layer. In this work, the physical vapor deposition\\u000a (PVD) technique is used for coating a magnesium (Mg) AZ31 sheet substrate with a thin layer of high purity aluminum (Al) and\\u000a Al–12.6%

Mohamed A. Taha; Nahed A. El-Mahallawy; Rawia M. Hammouda; Sherif I. Nassef

2010-01-01

103

Galvanic corrosion properties of differently PVD-treated magnesium die cast alloy AZ91  

Microsoft Academic Search

Different types of PVD coatings and plasma treatments were applied for the surface treatment of magnesium die cast alloy AZ91 specimens. The different types of surface treatment were all developed by the authors and the fundamental properties are described elsewhere. The coating systems were:•9 ?m CrN hard coating•3 ?m TiN coating•0.5 ?m plasma anodisation layer and 3 ?m Al2O3 coatingThe

H. Hoche; C. Blawert; E. Broszeit; C. Berger

2005-01-01

104

Computational Materials Science and Surface Engineering The computer simulation of internal stresses on the PVD coatings  

Microsoft Academic Search

Purpose: The general topic of this paper is the computer simulation with the use of finite element method for determining the internal stresses in coatings Ti+TiN, Ti+Ti(CxN1-x) i Ti+TiC obtained in the magnetron PVD process on the sintered high-speed steel of the ASP 30 in different temperatures of 460, 500 and 540°C Design\\/methodology\\/approach: Modelling of stresses was performed with the

A. ?liwa; L. A. Dobrza?ski; W. Sitek

105

Particle Defect Reduction in the Endura Titanium Nitride PVD Sputter System  

SciTech Connect

Particles are inevitably generated in physical vapor deposition (PVD) systems due to the delamination of deposited films on various process chamber parts and shielding. Non-collimated (blanket) and collimated PVD Titanium Nitride (TiN) deposition processes are used for metal ARC (anti-reflective coating) and underlayers, and for the "contact liner" deposition steps (TiN adhesion layers before plug formation). Probe yield analysis and SRAM bit failure analysis, using conventional failure analysis, have shown that particles at these process steps can have a significant impact on wafer yields. In many typical semiconductor wafer fabs, particles generated by TiN film deposition rank consistently at or near the top of the defect pareto. This paper summarizes the results of defect reduction experiments conducted on an Applied Materials Endura Physical Vapor Deposition (PVD) system and various off-line experiments examining film and adhesion characteristics. It includes the results of film adhesion and shield temperature control experiments aimed at reducing defect levels. Key fidings, particle reduction results, and recommended defect reduction measures are presented. The reduction in particles not only can improve yields, but also result in substantial cost savings through the extension of chamber kit end-of-life (EOL).

Louis, Mark D.; Ohlhausen, Tony; Peebles, Diane; Specner, Roger; Whitehair, Hal

1999-06-24

106

Controlling Wear on Nanoscale  

NASA Astrophysics Data System (ADS)

One definition of wear in a tribological sense is that it is the progressive loss of mass from the operating surface of a body as a result of relative motion with another surface. Generally, tribology may be defined as the study of friction wear and lubrication, but in comparison with friction forces or lubrication methods, very little work has been done on the extremely important area of wear and surface damage. For systems consisting of common materials (metals, polymers, ceramics), there are at least four main mechanisms by which wear and surface damage can occur between solids in relative motion: abrasive-, adhesive-, chemical-, corrosive-, or fatigue-wear mechanisms. The occurrence of such different wear mechanisms involves the fundamental mechanics of molecular and supra-molecular scale. As a consequence, the understanding of surface properties on nanoscale level should be generated to also have a satisfactory knowledge of materials response on macrometer scale. Investigation of the fundamental characteristics of wear at the nanoscale is complicated by some factors and forces that acting on such scale level have not yet been addressed in the tribology of macro-systems. Since these forces are sensitive to the environment and surface condition of the specimens, it is quite difficult to determine them accurately. Further, quantification of wear is not straightforward since the amount of wear is often too small to be detected by surface-sensitive instruments. Nanowear measurements have been object of rapid development of precise measuring tools following to the introduction of scanning-probe microscopy (SPM) family. The advent of SPM family opened a new unique opportunity to study wear mechanisms on nanoscale, making possible to simulate one single asperity surface sliding on the other one and controlling many physical parameters during the contact dynamics. Further, SPM made possible to a have a direct connection between experimental data and theoretical models.

D'Acunto, Mario

107

Nanotribology and Nanoscale Friction  

SciTech Connect

Tribology is the science and technology of contacting solid surfaces in relative motion, including the study of lubricants, lubrication, friction, wear, and bearings. It is estimated that friction and wear cost the U.S. economy 6% of the gross national product (Persson, 2000). For example, 5% of the total energy generated in an automobile engine is lost to frictional resistance. The study of nanoscale friction has a technological impact in reducing energy loss in machines, in microelectromechanical systems (MEMS), and in the development of durable, low-friction surfaces and ultra-thin lubrication films.

Guo, Yi [Stevens Institute of Technology, Hoboken, New Jersey; Qu, Zhihua [University of Central Florida, Orlando; Braiman, Yehuda [ORNL; Zhang, Zhenyu [ORNL; Barhen, Jacob [ORNL

2008-01-01

108

Simulations of Metallic Nanoscale Structures  

Microsoft Academic Search

Density-functional-theory calculations can be used to understand and predict materials properties based on their nanoscale composition and structure. In combination with efficient search algorithms DFT can furthermore be applied in the nanoscale design of optimized materials. The first part of the talk will focus on two different types of nanostructures with an interesting interplay between chemical activity and conducting states.

Karsten W. Jacobsen

2003-01-01

109

Hybrid diffusive/PVD treatments to improve the tribological resistance of Ti-6Al-4V.  

PubMed

Titanium alloys are nowadays used for a wide range of biomedical applications thanks to their combination of high mechanical resistance, high corrosion resistance and biocompatibility. Nevertheless, the applicability of titanium alloys is sometimes limited due to their low microhardness and tribological resistance. Thus the titanium alloys cannot be successfully applied to prosthetic joint couplings. A wide range of surface treatments, in particular PVD coatings such as CrN and TiN, have been used in order to improve the tribological behaviour of titanium alloys. However, the low microhardness of the titanium substrate often results in coating failure due to cracks and delamination. For this reason, hybrid technologies based on diffusive treatments and subsequent PVD coatings may improve the overall coating resistance. In this work, conventional PVD coatings of CrN or TiCN, deposited on Titanium Grade 5, were characterized and then combined with a standard thermal diffusive nitriding treatment in order to improve the tribological resistance of the titanium alloys and avoid coating delamination. The different treatments were studied by means of scanning electron microscopy both on the sample surface and in cross-section. In-depth composition profiles were obtained using glow discharge optical emission spectrometry (GDOES) and localized energy dispersive X-ray diffraction on linear scan-lines. The microhardness and adhesion properties of the different treatments were evaluated using Vickers microhardness tests at different load conditions. The indentations were observed by means of SEM in order to evaluate delaminated areas and the crack's shape and density. The tribological behaviour of the different treatments was tested in dry conditions and in solution, in alternate pin-on-flat configuration, with a frequency of 0.5 Hz. After testing, the surface was investigated by means of stylus profilometry and SEM both on the surface and in cross-section. The standalone PVD coatings show a limited tribological resistance due to the low hardness of the substrate, which results in fractures and delamination. The combination of a diffusive process and a subsequent PVD coating shows a stronger effect in improving the tribological resistance of the substrate. PMID:24092178

Marin, E; Offoiach, R; Lanzutti, A; Regis, M; Fusi, S; Fedrizzi, L

2013-01-01

110

Nanoscale Optoelectronic Photosynthetic Devices  

NASA Astrophysics Data System (ADS)

This presentation provides an overview and recent progress in the Oak Ridge National Laboratory research program in molecular electronics and green plant photosynthesis. The photosynthetic reaction center is a nanoscale molecular diode and photovoltaic device. The key thrust of our research program is the construction of molecular electronic devices from these nanoscale structures. Progress in this multidisciplinary research program has been demonstrated by direct electrical contact of emergent electrons with the Photosystem I (PS I) reaction center by nanoparticle precipitation. Demonstration of stable diode properties of isolated reaction centers combined with the ability to orient PS I by self-assembly on a planar surface, makes this structure a good building block for 2-D and potentially 3-D devices. Metallization of isolated PS I does not alter their fundamental photophysical properties and they can be bonded to metal surfaces. We report here the first measurement of photovoltage from single PS I reaction centers. Working at the Cornell University National Nanofabrication Facility, we have constructed sets of dissimilar metal electrodes separated by distances as small as 6 nm. We plan to use these structures to make electrical contact to both ends of oriented PSI reaction centers and thereby realize biomolecular logic circuits. Potential applications of PSI reaction centers for optoelectronic applications as well as molecular logic device construction will be discussed.

Greenbaum, Elias; Lee, Ida; Guillorn, Michael; Lee, James W.; Simpson, Michael L.

2001-03-01

111

Photoresponsive nanoscale columnar transistors  

PubMed Central

This study reports a general methodology for making stable high-performance photosensitive field effect transistors (FET) from self-assembled columns of polycyclic aromatic hydrocarbons by using single-walled carbon nanotubes (SWNTs) as point contacts. In particular, the molecules used in this work are liquid crystalline materials of tetra(dodecyloxy)hexabenzocoronenes (HBCs) that are able to self-organize into columnar nanostructures with a diameter similar to that of SWNTs and then form nanoscale columnar transistors. To rule out potential artifacts, 2 different structural approaches were used to construct devices. One approach is to coat thin films of HBCs onto the devices with the SWNT–metal junctions protected by hydrogensilsesquioxane resin (HSQ), and the other is to place a droplet of HBC exactly on the nanogaps of SWNT electrodes. Both types of devices showed typical FET behaviors, indicating that SWNT–molecule–SWNT nanojunctions are responsible for the electrical characteristics of the devices. After thermally annealing the devices, HBC molecules assembled into columnar structures and formed more efficacious transistors with increased current modulation and higher gate efficiency. More interestingly, when the devices were exposed to visible light, photocurrents with an on/off ratio of >3 orders of magnitude were observed. This study demonstrates that stimuli-responsive nanoscale transistors have the potential applications in ultrasensitive devices for environmental sensing and solar energy harvesting.

Guo, Xuefeng; Xiao, Shengxiong; Myers, Matthew; Miao, Qian; Steigerwald, Michael L.; Nuckolls, Colin

2009-01-01

112

Nanoscale relaxation oscillator  

DOEpatents

A nanoscale oscillation device is disclosed, wherein two nanoscale droplets are altered in size by mass transport, then contact each other and merge through surface tension. The device may also comprise a channel having an actuator responsive to mechanical oscillation caused by expansion and contraction of the droplets. It further has a structure for delivering atoms between droplets, wherein the droplets are nanoparticles. Provided are a first particle and a second particle on the channel member, both being made of a chargeable material, the second particle contacting the actuator portion; and electrodes connected to the channel member for delivering a potential gradient across the channel and traversing the first and second particles. The particles are spaced apart a specified distance so that atoms from one particle are delivered to the other particle by mass transport in response to the potential (e.g. voltage potential) and the first and second particles are liquid and touch at a predetermined point of growth, thereby causing merging of the second particle into the first particle by surface tension forces and reverse movement of the actuator. In a preferred embodiment, the channel comprises a carbon nanotube and the droplets comprise metal nanoparticles, e.g. indium, which is readily made liquid.

Zettl, Alexander K. (Kensington, CA); Regan, Brian C. (Los Angeles, CA); Aloni, Shaul (Albany, CA)

2009-04-07

113

Simulating nanoscale semiconductor devices.  

SciTech Connect

The next generation of electronic devices will be developed at the nanoscale and molecular level, where quantum mechanical effects are observed. These effects must be accounted for in the design process for such small devices. One prototypical nanoscale semiconductor device under investigation is a resonant tunneling diode (RTD). Scientists are hopeful the quantum tunneling effects present in an RTD can be exploited to induce and sustain THz frequency current oscillations. To simulate the electron transport within the RTD, the Wigner-Poisson equations are used. These equations describe the time evolution of the electrons distribution within the device. In this paper, this model and a parameter study using this model will be presented. The parameter study involves calculating the steady-state current output from the RTD as a function of an applied voltage drop across the RTD and also calculating the stability of that solution. To implement the parameter study, the computational model was connected to LOCA (Library of Continuation Algorithms), a part of Sandia National Laboratories parallel solver project, Trilinos. Numerical results will be presented.

Salinger, Andrew Gerhard; Zhao, P. (North Carolina State University, Raleigh, NC); Woolard, D. L. (U. S. Army Research Laboratory, NC); Kelley, C. Tim (North Carolina State University, Raleigh, NC); Lasater, Matthew S. (North Carolina State University, Raleigh, NC)

2005-03-01

114

Single Shot Nanoscale Magnetic Imaging at the Linac Coherent Light Source  

Microsoft Academic Search

One of the major challenges of modern magnetism research is the manipulation and control of the magnetization on ultrafast timescales. Using the unprecedented brightness of the Linac Coherent Light Source (LCLS), we have been able to image the nanoscale magnetic worm domain structures in [Co\\/Pd] multilayer systems with a single x-ray pulse through x-ray Fourier transform holography on the Co

Benny Wu; Tianhan Wang; Catherine Graves; Diling Zhu; William Schlotter; Joshua Turner; Joachim Stohr; Andreas Scherz

2011-01-01

115

Netlike knitting of polyelectrolyte multilayers on honeycomb-patterned substrate.  

PubMed

The pH-amplified exponential growth layer-by-layer (LBL) self-assembly process was directly performed on honeycomb-patterned substrate for achievement of "guided patterning" of polyelectrolyte multilayers. Polyethylenimine (PEI) and poly(acrylic acid) (PAA) were used as polyanions, and their pH were carefully tuned to achieve pH-enhanced exponential growth. Guided by underlying hexagonally patterned islandlike poly(dimethylsiloxane) (PDMS) arrays, the diffusive polyelectrolytes rapidly interweaved into linear, multilayered structures distributed along the grooves between the patterned protuberate and formed a regular network of multilayered film with uniform mesh size. Netlike "knitting" of polyelectrolyte multilayers on honeycomb-patterned substrate has been realized by following this procedure. Superhydrophobic surfaces could be readily obtained after several bilayers of LBL assembly (with thermal cross-linking and surface fluorination by chemical vapor deposition), indicating that successful fabrication of functional micro- and nanoscale hierarchical structures can be achieved. Both high- and low-adhesion superhydrophobic surfaces ("petal effect" and "lotus effect") can be obtained with different bilayers of assembly, proving that different levels of nano- to microstructural hierarchy can be realized using this method. Furthermore, we were able to get topographically asymmetric, free-standing, polyelectrolyte multilayer films in the case that we performed more than eight bilayers of assembly. This research reported template-directed LBL patterning assembly for the first time. It provides a beneficial exploration for the surface patterning technique for the LBL assembly process. PMID:20684559

Sun, Wei; Shen, Liyan; Wang, Jiaming; Fu, Ke; Ji, Jian

2010-09-01

116

A Nanoscale Tale  

NASA Astrophysics Data System (ADS)

Experimentalists constantly seek to overcome technical limitations. This is especially true in the world of biophysics, where the drive to study molecular targets such as ion channels, a type of membrane transport protein, has resulted in methodological breakthroughs that have merited the Nobel Prize (Hodgkin and Huxley, 1963; Neher and Sakmann, 1991). In this presentation I will explain how nanoscale phenomena that are essential for sensory perception underlie the ability of dancers, gymnasts, and musicians to excel at their artistic endeavors. I will describe how our investigations of sensory mechanotransduction and the quest for improved signal amplification inspired a scientific journey that has culminated in an exciting new line of collaborative NIH-funded research with nanomaterials (quantum dots). I will conclude with a general discussion of how training in physics offers an ideal foundation for interdisciplinary research in health related fields, such as those that deal with neuroscience and disorders of the nervous system.

Serrano, Elba

2008-10-01

117

Rational Design of a Transition State Analogue with Picomolar Affinity for Pseudomonas aeruginosa PvdQ, a Siderophore Biosynthetic Enzyme.  

PubMed

The Pseudomonas aeruginosa enzyme PvdQ can process different substrates involved in quorum-sensing or in siderophore biosynthesis. Substrate selectivity was evaluated using steady-state kinetic constants for hydrolysis of N-acyl-homoserine lactones (HSLs) and p-nitrophenyl fatty acid esters. PvdQ prefers substrates with alkyl chains between 12 and 14 carbons long that do not bear a 3-oxo substitution and is revealed here to have a relatively high specificity constant for selected N-acyl-HSLs (kcat/KM = 10(5) to 10(6) M(-1) s(-1)). However, endogenous P. aeruginosa N-acyl-HSLs are ?100-fold disfavored, supporting the conclusion that PvdQ was not primarily evolved to regulate endogenous quorum-sensing. PvdQ plays an essential biosynthetic role for the siderophore pyoverdine, on which P. aeruginosa depends for growth in iron-limited environments. A series of alkylboronate inhibitors was found to be reversible, competitive, and extremely potent (Ki ? 190 pM). A 1.8 Å X-ray structure shows that 1-tridecylboronic acid forms a monocovalent bond with the N-terminal ?-chain Ser residue in the PvdQ heterodimer, mimicking a reaction transition state. This boronic acid inhibits growth of P. aeruginosa in iron-limited media, reproducing the phenotype of a genetic pvdQ disruption, although co-administration of an efflux pump inhibitor is required to maintain growth inhibition. These findings support the strategy of designing boron-based inhibitors of siderophore biosynthetic enzymes to control P. aeruginosa infections. PMID:23883096

Clevenger, Kenneth D; Wu, Rui; Er, Joyce A V; Liu, Dali; Fast, Walter

2013-08-06

118

Vacuum Mechanisms of Nanoscale Precision  

Microsoft Academic Search

The principles of design of vacuum mechanims of nanoscale precision are presented. Physical basics of the mechanisms nanoscale\\u000a precision are discussed. Vacuum multicoordinate drives and manipulators are also shown.\\u000a \\u000a The analysis of vacuum technological equipment and vacuum research equipment shows that the most strict requirements for the\\u000a object transference are in electron beam micro lithography equipment. For example, electron beam

E. A. Deulin; V. P. Mikhailov; Yu. V. Panfilov; R. A. Nevshupa

119

Interfacial effects in multilayers  

SciTech Connect

Interfacial structure and the atomic interactions between atoms at interfaces in multilayers or nano-laminates have significant impact on the physical properties of these materials. A technique for the experimental evaluation of interfacial structure and interfacial structure effects is presented and compared to experiment. In this paper the impact of interfacial structure on the performance of x-ray, soft x-ray and extreme ultra-violet multilayer optic structures is emphasized. The paper is concluded with summary of these results and an assessment of their implications relative to multilayer development and the study of buried interfaces in solids in general.

Barbee, T.W., Jr.

1998-04-01

120

Friction laws at the nanoscale.  

PubMed

Macroscopic laws of friction do not generally apply to nanoscale contacts. Although continuum mechanics models have been predicted to break down at the nanoscale, they continue to be applied for lack of a better theory. An understanding of how friction force depends on applied load and contact area at these scales is essential for the design of miniaturized devices with optimal mechanical performance. Here we use large-scale molecular dynamics simulations with realistic force fields to establish friction laws in dry nanoscale contacts. We show that friction force depends linearly on the number of atoms that chemically interact across the contact. By defining the contact area as being proportional to this number of interacting atoms, we show that the macroscopically observed linear relationship between friction force and contact area can be extended to the nanoscale. Our model predicts that as the adhesion between the contacting surfaces is reduced, a transition takes place from nonlinear to linear dependence of friction force on load. This transition is consistent with the results of several nanoscale friction experiments. We demonstrate that the breakdown of continuum mechanics can be understood as a result of the rough (multi-asperity) nature of the contact, and show that roughness theories of friction can be applied at the nanoscale. PMID:19242472

Mo, Yifei; Turner, Kevin T; Szlufarska, Izabela

2009-02-26

121

Influence of the PVdF binder on the stability of LiCoO 2 electrodes  

Microsoft Academic Search

We report herein on the effect of the PVdF binder on the stability of composite LiCoO2 electrodes at elevated temperatures in 1M LiPF6 EC\\/EMC solutions at open circuit conditions. The structure and morphology of composite LiCoO2 electrodes with different combinations of electrode components (LiCoO2 active material, PVdF binder, carbon black and current collector) were evaluated by Raman spectroscopy, X-ray diffraction

E. Markevich; G. Salitra; D. Aurbach

2005-01-01

122

Wedged multilayer Laue lens  

SciTech Connect

A multilayer Laue lens (MLL) is an x-ray focusing optic fabricated from a multilayer structure consisting of thousands of layers of two different materials produced by thin-film deposition. The sequence of layer thicknesses is controlled to satisfy the Fresnel zone plate law and the multilayer is sectioned to form the optic. An improved MLL geometry can be created by growing each layer with an in-plane thickness gradient to form a wedge, so that every interface makes the correct angle with the incident beam for symmetric Bragg diffraction. The ultimate hard x-ray focusing performance of a wedged MLL has been predicted to be significantly better than that of a nonwedged MLL, giving subnanometer resolution with high efficiency. Here, we describe a method to deposit the multilayer structure needed for an ideal wedged MLL and report our initial deposition results to produce these structures.

Conley, Ray; Liu Chian; Qian Jun; Kewish, Cameron M.; Macrander, Albert T. [X-ray Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Yan Hanfei; Maser, Joerg [X-ray Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Center for Nanoscale Materials, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Kang, Hyon Chol; Stephenson, G. Brian [Center for Nanoscale Materials, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States)

2008-05-15

123

Wedged multilayer Laue Lens.  

SciTech Connect

A multilayer Laue lens (MLL) is an x-ray focusing optic fabricated from a multilayer structure consisting of thousands of layers of two different materials produced by thin-film deposition. The sequence of layer thicknesses is controlled to satisfy the Fresnel zone plate law and the multilayer is sectioned to form the optic. An improved MLL geometry can be created by growing each layer with an in-plane thickness gradient to form a wedge, so that every interface makes the correct angle with the incident beam for symmetric Bragg diffraction. The ultimate hard x-ray focusing performance of a wedged MLL has been predicted to be significantly better than that of a nonwedged MLL, giving subnanometer resolution with high efficiency. Here, we describe a method to deposit the multilayer structure needed for an ideal wedged MLL and report our initial deposition results to produce these structures.

Conley, R.; Liu, C.; Qian, J.; Kewish, C. M.; Macrander, A. T.; Yan, H.; Kang, H. C.; Maser, J.; Stephenson, G. B.

2008-05-01

124

Multilayer Optical Learning Networks,  

National Technical Information Service (NTIS)

A new approach to learning in a multilayer optical neural network based on holographically interconnected nonlinear devices is presented. The proposed network can learn the interconnections that form a distributed representation of a desired pattern trans...

K. Wagner D. Psaltis

1987-01-01

125

Nanoscale Torsional Optomechanics  

NASA Astrophysics Data System (ADS)

Torsional resonators, which can be designed to measure torques with high sensitivity, have been an effective tool to study magnetism, gravity, and various material and optical properties. Taking advantage of improved micro-fabrication techniques, these torque sensors are now pushing the limit in terms of size - scaling all the way down to the nanoscale regime - and therefore must be equipped with sensitive mechanical transduction schemes. Here we present a method for measuring torques as little as 4 x10^20 Nm, using optomechanics. Recently optomechanics has been revealed as a reliable method for mechanical transduction, with higher sensitivity than previously possible. This sensitivity of the optomechanical system comes from the evanescent coupling between a high quality factor optical resonator and the mechanical device, and is fully integratable on a chip using the silicon-on-insulator platform. We present our first generation torsional optomechanics, using a dimpled optical fiber system for measurement, with a calibrated sensitivity down to 7 fm/?Hz. This torsional optomechanical platform will now serve as a basis for further experiments to explore new physics and technology, in particular quantum resonators at low temperatures.

Kim, Paul H.; Doolin, Callum; Hauer, Bradley D.; MacDonald, Allison J. R.; Freeman, Mark R.; Barclay, Paul E.; Davis, John P.

2013-03-01

126

Thermometry at the nanoscale  

NASA Astrophysics Data System (ADS)

Non-invasive precise thermometers working at the nanoscale with high spatial resolution, where the conventional methods are ineffective, have emerged over the last couple of years as a very active field of research. This has been strongly stimulated by the numerous challenging requests arising from nanotechnology and biomedicine. This critical review offers a general overview of recent examples of luminescent and non-luminescent thermometers working at nanometric scale. Luminescent thermometers encompass organic dyes, QDs and Ln3+ions as thermal probes, as well as more complex thermometric systems formed by polymer and organic-inorganic hybrid matrices encapsulating these emitting centres. Non-luminescent thermometers comprise of scanning thermal microscopy, nanolithography thermometry, carbon nanotube thermometry and biomaterials thermometry. Emphasis has been put on ratiometric examples reporting spatial resolution lower than 1 micron, as, for instance, intracellular thermometers based on organic dyes, thermoresponsive polymers, mesoporous silica NPs, QDs, and Ln3+-based up-converting NPs and ?-diketonate complexes. Finally, we discuss the challenges and opportunities in the development for highly sensitive ratiometric thermometers operating at the physiological temperature range with submicron spatial resolution.

Brites, Carlos D. S.; Lima, Patricia P.; Silva, Nuno J. O.; Millán, Angel; Amaral, Vitor S.; Palacio, Fernando; Carlos, Luís D.

2012-07-01

127

A channelless, multilayer router  

SciTech Connect

We have implemented a channel-less, gridless, multilayer router as part of the Magic IC layout system. The router is designed to handle new routing problems associated with emerging technologies such as Wafer Scale Integration and multilayered metal processes. Three features distinguish this router: rectilinear Steiner trees with floating segments, a routing scheduler, and a corner-stitched database. 7 refs., 2 figs., 4 tabs.

Lunow, R.E.

1988-03-15

128

Influence of EB-PVD TBC Microstructure on Thermal Barrier Coating System Performance Under Cyclic Conditions  

SciTech Connect

The lifetimes of electron beam physical vapor deposited (EB-PVD) thermal barrier coating systems (TBCs) with three different microstructures of the Y2O3-stabilized ZrO, YSZ) ceramic top layer were investigated in lh thermal cycles at 1100 and 1150°C in flowing oxygen. Single crystal alloys CMSX-4 and Rene N5 that had been coated with an EB-PVD NiCoCrAlY bond coat were chosen as substrate materials. At 1150°C all samples failed after 80-100, lh cycles, predominantly at the bond coat/alumina interface after cooling down from test temperature. The alumina scale remained adherent to the YSZ after spallation. Despite the different YSZ microstructures no clear tendency regarding differences in spallation behavior were observed at 1150°C. At 1100°C the minimum lifetime was 750 , lh cycles for CMSX-4, whereas the first Rene N5 specimen failed after 1750, lh cycles. The longest TBC lifetime on CMSX-4 substrates was 1250, lh cycles, whereas the respective Rene N5 specimens have not yet failed after 2300, lh cycles. The failure mode at 1100°C was identical to that at 115O?C, i.e. the TBC spalled off the surface exposing bare metal after cooling. Even though not all specimens have failed to date, the available results at 1100°C suggested that both, the substrate alloy chemistry and the YSZ microstructure significantly affect the spallation resistance of the TBC.

Leyens, C.; Pint, B.A.; Schulz, U.; Wright, I.G.

1999-04-12

129

Adsorption-transport modeling of anions through PVD membrane in the presence of the screen phenomenon  

NASA Astrophysics Data System (ADS)

A mathematical model for transport and adsorption of chloride and sulphate ions through PVD membrane is presented at two pressures; 8 and 15 bar and 40 °C. The PVD membrane is negatively charged. Saturated brine containing NaCl with the concentration higher than 97% was challenged with the membrane as the feed. Other available ions in the solution were Fe 2+, Ca 2+, Mg 2+ and SO 42-. The screen effect of the cations on the membrane surface charge facilitates the passage of the anions through the membrane without any noticeable electrostatic repulsion. Hermia blocking laws combined with experimental results indicate that the internal pore closure of the membrane by anions and cake deposition on the membrane surface by cations are the separation mechanisms. The transmission of anions through the membrane may be predicted with a simple transport equation (convection and diffusion) combined with an adsorption isotherm. Both Langmuir and Freundlich adsorption isotherms were employed due to the simplicity and validity in liquid systems. The isotherm's parameters were determined at 10 bar during the unsteady state filtration. Under this condition, the permeate flux and concentration varied sharply due to adsorption. Finally, the model was compared with the experimental rejection data. An acceptable agreement around 95% at 8 bar and 92% at 15 bar was observed between theoretical model and experimental data.

Madaeni, S. S.; Salehi, E.

2009-01-01

130

Ensuring the adhesion and cohesion strength of PVD (TiAl)N and TiN coatings  

NASA Astrophysics Data System (ADS)

The fracture of PVD coatings as a result of bulging and cohesion cracking is shown to be controlled by creating a discrete coating surface topography. For longitudinal compression, the discrete region size is calculated using the theory of stability of elastic systems; under tensile stresses, the coating region size is chosen on the basis of the calculated crack step.

Soroka, E. B.; Klimenko, S. A.; Kopeikina, M. Yu.

2011-04-01

131

Cutting performance and wear characteristics of PVD coated and uncoated carbide tools in face milling Inconel 718 aerospace alloy  

Microsoft Academic Search

In this paper, cutting performance and failure characteristics of two PVD TiN coated and an uncoated tungsten carbide grades with identical geometry are presented. Face-milling tests of Inconel 718 superalloy were performed to investigate the effect of cutting speed and feed rate on tools performance under wet conditions. Tools were thoroughly examined under SEM at two stages in order to

A Jawaid; S Koksal; S Sharif

2001-01-01

132

Applications of multilayer optics  

NASA Astrophysics Data System (ADS)

Recent development of multilayer mirror and its applications in extreme ultraviolet (EUV), soft X-ray ranges in China was reviewed in this paper. Three types of multilayer mirrors were developed with special performance for dense plasma diagnostics, EUV astronomical observation. Firstly, dual-periodic W/B4C multilayer mirror was designed for Kirkpatrick-Baez (K-B) microscopy working at TiK? line (4.75 keV), which is highly reflective both at hard X-ray (CuK? line at 8.05 keV) and soft X-ray (4.75 keV). Using this mirror, the K-B system can be aligned conveniently in air using hard X-ray instead of in vacuum. The second mirror is aperiodic Mg/SiC multilayer, also a bi-functional mirror with high reflectivity for He-II emission line (30.4 nm) but suppressing He-I emission line (58.4 nm) in astronomy observation, which will replace the traditional combination of periodic multilayer and the fragile film filter. This will be more safe in satellite launching. The third mirror is Mo/Si periodic multilayer, depositing on a parabolic substrate with diameter of 230 mm, which is designed for EUV telescope for imaging of solar corona by selecting Fe-XII emission (19.5 nm). The uniformity of lateral layer thickness distribution is within ±0.3% along the diameter of mirror, measured by X-ray reflectometry. The measured peak reflectivity is 42% at the wavelength of 19.5 nm. All these multilayer mirrors were prepared by using magnetron sputtering system in our group.

Wang, Zhanshan; Zhu, Jingtao; Mu, Baozhong; Zhang, Zhong; Wang, Fengli; Xu, Jing; Li, Wenbin; Chen, Lingyan

2010-11-01

133

Chemical Reaction Dynamics in Nanoscale Environments.  

National Technical Information Service (NTIS)

The major focus of the research in this program is the study of the behavior of molecular systems confined in nanoscale environments. The goal is to develop a theoretical framework for predicting how chemical reactions occur in nanoscale environments. To ...

E. M. Goldfield H. B. Schlegel W. L. Hase

2006-01-01

134

Properties of nano-multilayered hard coatings deposited by a new hybrid coating process: Combined cathodic arc and unbalanced magnetron sputtering  

Microsoft Academic Search

Nano-scale multilayered coatings of (Ti,Al)N\\/SiN, (Ti,Al)N\\/WN, and CrN\\/BCN were deposited by a new hybrid coating process that combined cathodic arc and unbalanced magnetron sputtering (UBM). Cross-sectional transmission electron microscopy (TEM) analysis of the coatings deposited by the hybrid process revealed that these coatings had a multilayer structure in that layers deposited by the arc source and the sputter source were

Kenji Yamamoto; Susumu Kujime; Kazuki Takahara

2005-01-01

135

A Simplified Multilayer Circuit Board.  

National Technical Information Service (NTIS)

A multilayer printed circuit board is disclosed having appropriate ground and voltage planes. The multi-layer printed circuit board includes a mounting plane, a plurality of dielectric sheets stacked upon the mounting plane, a plurality of conductive shee...

B. W. Patz

1980-01-01

136

Fluctuations in nanoscale magnetoelectronics devices  

NASA Astrophysics Data System (ADS)

We analyze the quantum and thermal fluctuations in a magnetic nanoparticle that can be used as a component in magnetoelectronic devices and compare their influences on the basic modes of device operation at the nanoscale level. Within the framework of the effective Landau free energy constructed using a spin density functional approximation, we study the interplay between quantum and thermal fluctuations in different quantum numbers as the temperature and dimension of the particle are varied. Both theoretical and simulation results are presented for quantifying the quantum and thermal fluctuations. While quantum fluctuations hamper further miniaturization of today's electronic devices, our results suggest that the dominant factors affecting magnetoelectronic nanoscale devices are thermal fluctuations.

Fan, Yabin; Ovchinnikov, Igor V.; Jiang, Wanjun; Schwartz, Robert N.; Wang, Kang L.

2012-11-01

137

Thermoelectric effects in nanoscale junctions.  

PubMed

Despite its intrinsic nonequilibrium origin, thermoelectricity in nanoscale systems is usually described within a static scattering approach which disregards the dynamical interaction with the thermal baths that maintain energy flow. Using the theory of open quantum systems, we show instead that unexpected properties, such as a resonant structure and large sign sensitivity, emerge if the nonequilibrium nature of this problem is considered. Our approach also allows us to define and study a local temperature, which shows hot spots and oscillations along the system according to the coupling of the latter to the electrodes. This demonstrates that Fourier's lawa paradigm of statistical mechanicsis generally violated in nanoscale junctions. PMID:19072125

Dubi, Yonatan; Di Ventra, Massimiliano

2009-01-01

138

Nanoscale inhomogeneities in thermoresponsive polymers.  

PubMed

This article highlights the occurrence and nature of nanoscale inhomogeneities in thermoresponsive polymers and focuses on different experimental techniques for their observation and characterization. Such inhomogeneities can be regarded as nanoscopic domains of collapsed polymer segments (or of a small number of unimers), which provide a nonpolar, hydrophobic interior. Continuous wave (CW) electron paramagnetic resonance (EPR) spectroscopy on amphiphilic reporter molecules (spin probes) as an intrinsically local technique is particularly emphasized. In combination with different ensemble-averaging methods, it provides a holistic understanding of the often inhomogeneous nanoscale processes during the temperature-induced collapse of a thermoresponsive polymer. PMID:23169221

Kurzbach, Dennis; Junk, Matthias J N; Hinderberger, Dariush

2012-11-21

139

Unconventional Patterning at the Nanoscale  

NSDL National Science Digital Library

A team of students and professors at Northwestern University created this course as a how-to guide to many basic nanoscale patterning procedures. It is a video lab manual that will give students training in soft lithography, for example, molding. Students will also be able to synthesize, characterize, and create nanoscale devices using common, cheap materials, and some typical chemicals. Along with each procedural video, there are also tutorials to explain the meaning and purpose of each experiment. This is a valuable website for institutions that want to introduce nanopatterning to their students, but have limited resources to do so. Computers must have Quick Time installed on them before viewing these videos.

Odom, Teri W.; Viswanathan, M.; Babayan, Y.

2012-04-12

140

Molecular and Nanoscale Computing and Technology  

Microsoft Academic Search

In this chapter, we have presented an overview of various nanoscale and molecular computing architectures. We have given a brief tutorial on various existing nanoscale and molecular devices. These include molecular switches, resonant tunnel diodes, tunnel diodes, single electron transistors, carbon nanotube field-effect transistors, quantum dots, and spin systems. We have next discussed a set of nanoscale computing modules, such

Mary M. Eshaghian-Wilner; Amar H. Flood; Alex Khitun; J. Fraser Stoddart; Kang Wang

141

Nanoscale eletromechanical behavior  

NASA Astrophysics Data System (ADS)

In this dissertation, we try to address some of the questions which arise while understanding the electromechanical behavior at the nanoscale. (1) Metals exhibit a size-dependent hardening when subjected to indentation. Mechanisms for this phenomenon have been intensely researched in recent times. Does such a size-effect also exist in the electromechanical behavior of ferroelectrics? If yes, what are the operative mechanisms? Experiments on BaTiO3 indeed suggest an elastic electromechanical size-effect. We argue, through theoretical calculations and differential experiments on another non-ferroelectric piezoelectric (Quartz), that the phenomenon of flexoelectricity (as opposed to dislocation activity) is most likely responsible for our observations. (2) Using a combination of a theoretical framework and atomistic calculations, we highlight the concept of surface piezoelectricity that can be used to interpret the piezoelectricity of nanostructures. Focusing on three specific material systems (ZnO, SrTiO3 and BaTiO3), we discuss the renormalization of apparent piezoelectric behavior at small scales. In a rather interesting interplay of symmetry and surface effects, we show that nanostructures of certain non-piezoelectric materials may also exhibit piezoelectric behavior. For the case of ZnO, using a comparison with first principles calculations, we also comment on the fidelity of the widely-used core-shell interatomic potentials to capture non-bulk electro-mechanical response. (3) Building entire devices with multiple components on single nanowires will lead to the ultimate miniaturization promised by nanotechnology. The capacitance measured from a single coaxial nanowire capacitor Cu-Cu2O-C device corresponds to ˜294microF/cm2, which considerably exceeds previously reported values for metal-insulator-metal micro-capacitors and is nearly fifty times larger than what is predicted by classical electrostatics. Our quantum mechanical calculations indicate that this unusually high capacitance value is attributed to negative quantum capacitance of the dielectric-metal interface. Also, we argue through first principle calculations on Graphene-Boron Nitrate-Graphene capacitors that quantum capacitance plays a key role in decreasing the total effective capacitance.

Gharbi, Mohamed

142

Design and Synthesis of Bimetallic Electrocatalyst with Multilayered Pt-Skin Surfaces  

SciTech Connect

Advancement in heterogeneous catalysis relies on the capability of altering material structures at the nanoscale, and that is particularly important for the development of highly active electrocatalysts with uncompromised durability. Here, we report the design and synthesis of a Pt-bimetallic catalyst with multilayered Pt-skin surface, which shows superior electrocatalytic performance for the oxygen reduction reaction (ORR). This novel structure was first established on thin film extended surfaces with tailored composition profiles and then implemented in nanocatalysts by organic solution synthesis. Electrochemical studies for the ORR demonstrated that after prolonged exposure to reaction conditions, the Pt-bimetallic catalyst with multilayered Pt-skin surface exhibited an improvement factor of more than 1 order of magnitude in activity versus conventional Pt catalysts. The substantially enhanced catalytic activity and durability indicate great potential for improving the material properties by fine-tuning of the nanoscale architecture.

Wang, Chao [Argonne National Laboratory (ANL); Chi, Miaofang [ORNL; Li, Dongguo [Argonne National Laboratory (ANL); Strmcnik, Dusan [Argonne National Laboratory (ANL); Van der Vliet, Dennis [Argonne National Laboratory (ANL); Wang, Guofeng [Indiana University and Purdue University; Komanicky, Vladimir [Argonne National Laboratory (ANL); Chang, Kee-Chul [Argonne National Laboratory (ANL); Paulikas, Arvydas [Argonne National Laboratory (ANL); Tripkovic, Dusan [Argonne National Laboratory (ANL); Pearson, John [Argonne National Laboratory (ANL); More, Karren Leslie [ORNL; Markovic, Nenad [Argonne National Laboratory (ANL); Stamenkovic, Vojislav [Argonne National Laboratory (ANL)

2011-01-01

143

Design and synthesis of bimetallic electrocatalyst with multilayered Pt-skin surfaces.  

SciTech Connect

Advancement in heterogeneous catalysis relies on the capability of altering material structures at the nanoscale, and that is particularly important for the development of highly active electrocatalysts with uncompromised durability. Here, we report the design and synthesis of a Pt-bimetallic catalyst with multilayered Pt-skin surface, which shows superior electrocatalytic performance for the oxygen reduction reaction (ORR). This novel structure was first established on thin film extended surfaces with tailored composition profiles and then implemented in nanocatalysts by organic solution synthesis. Electrochemical studies for the ORR demonstrated that after prolonged exposure to reaction conditions, the Pt-bimetallic catalyst with multilayered Pt-skin surface exhibited an improvement factor of more than 1 order of magnitude in activity versus conventional Pt catalysts. The substantially enhanced catalytic activity and durability indicate great potential for improving the material properties by fine-tuning of the nanoscale architecture.

Wang, C.; Chi, M.; Li, D.; Strmcnik, D.; van der Vliet, D.; Wang, G.; Komanicky, V.; Chang, K.-C.; Paulikas, A. P.; Tripkovic, D.; Pearson, J.; More, K. L.; Markovic, N. M.; Stamenkovic, V. R. (Materials Science Division); (ORNL.); (Univ. of Pittsburgh)

2011-01-01

144

Magnetic multilayer interface anisotropy  

NASA Astrophysics Data System (ADS)

Ni/Mo and Ni/V multilayer magnetic anisotropy has been investigated as a function of Ni layer thickness, frequency and temperature. Variable frequency ferromagnetic resonance (FMR) measurements show, for the first time, significant frequency dependence associated with the multilayer magnetic anisotropy. The thickness dependence allows one to extract the interface contribution from the total anisotropy. Temperature dependent FMR (9 GHz) and room temperature magnetization indicate that strain between Ni and the non-magnetic layers is contributing significantly to the source of the interface anisotropy and the state of the interfacial magnetization. In order to examine the interface properties of other transition metal multilayer systems, investigations on Fe/Cu are underway and CoCr/Ag is being proposed. ESR measurements have been reported on Gd substituted YBaCuO superconductors and a novel quasi-equilibrium method has been developed to determine quickly and precisely the transition temperature.

Pechan, M. J.

145

Magnetic multilayer interface anisotropy  

SciTech Connect

Ni/Mo and Ni/V multilayer magnetic anisotropy has been investigated as a function of Ni layer thickness, frequency and temperature. Variable frequency ferromagnetic resonance (FMR) measurements show, for the first time, significant frequency dependence associated with the multilayer magnetic anisotropy. The thickness dependence allows one to extract the interface contribution from the total anisotropy. Temperature dependent FMR (9 GHz) and room temperature magnetization indicate that strain between Ni and the non-magnetic layers is contributing significantly to the source of the interface anisotropy and the state of the interfacial magnetization. In order to examine the interface properties of other transition metal multilayer systems, investigations on Fe/Cu are underway and CoCr/Ag is being proposed. ESR measurements have been reported on Gd substituted YBaCuO superconductors and a novel quasi-equilibrium method has been developed to determine quickly and precisely the ransition temperature.

Pechan, M.J.

1992-01-01

146

Physicochemical studies of PVdF-HFP-based polymer-ionic liquid composite electrolytes  

NASA Astrophysics Data System (ADS)

Polymer-ionic liquid composite electrolytes based on poly (vinylidenefluoride-co-hexafluoropropylene) (PVdF-HFP) and room temperature ionic liquid: 2,3-dimethyl-1-octylimidazolium hexafluorophosphate (DMOImPF6) have been synthesized and studied. The addition of dimethylacetamide (DMA) and propylene carbonate (PC), both with high dielectric constant and low viscosity, to polymer electrolytes has been found to result in an enhancement of conductivity by one order of magnitude. Composite polymer electrolytes containing ionic liquid have been found to be thermally stable upto 300°C. Motional narrowing observed in the variation of line width of 1H and 19F NMR peaks with temperature suggests that both cations and anions are mobile in these electrolytes.

Lalia, Boor Singh; Yamada, K.; Hundal, M. S.; Park, Jin-Soo; Park, Gu-Gon; Lee, Won-Yong; Kim, Chang-Soo; Sekhon, S. S.

2009-08-01

147

Nanogrinding of multi-layered thin film amorphous Si solar panels  

Microsoft Academic Search

Nanogrinding was performed on the cross-sections of amorphous Si thin film solar panels, which are nanoscale multi-layer structures consisting of hard and brittle materials. The deformed structures of the panel cross-sectional surfaces after grinding were investigated using electron and atomic force microscopy. The nanogrinding results were compared with those obtained from polishing and nanoscratching, demonstrating that the three processes had

Taro Sumitomo; Han Huang; Libo Zhou; Jun Shimizu

2011-01-01

148

Multilayer lactate oxidase shells on colloidal carriers as engines for nanosensors  

Microsoft Academic Search

Self-assembly methods are being studied for construction of nanoscale chemical sensors employing coimmobilized enzymes and indicator dyes. This paper describes the assembly of the catalytic enzyme lactate oxidase in multilayer films on colloidal templates via layer-by-layer self-assembly, which is a step toward achieving nanoengineered biosensors. The architecture of the resulting films was characterized using quartz crystal microbalance and zeta potential

Erich W. Stein; Michael J. McShane

2003-01-01

149

Multilayer Ferromagnetic Thin Films.  

NASA Astrophysics Data System (ADS)

Available from UMI in association with The British Library. Requires signed TDF. In recent years artificial multilayer thin films have attracted considerable interest, since it is hoped that these new materials will exhibit novel and interesting as well as useful electrical, magnetic and mechanical properties. For example, multilayer ferromagnetic thin films with perpendicular anisotropy are currently of greatest interest as vertical magnetic recording media. In addition, for ultrathin layers (i.e. several atomic layers), new materials with new structural and magnetic properties are expected. In this study, ultrathin multilayer ferromagnetic thin films have been investigated. They have been fabricated by a dual sputtering system with revolving substrate. This apparatus provided the flexibility necessary to produce samples with individual layer thicknesses ranging from 0.05 nm to several nm. The multilayers were prepared by sequential deposition if ferromagnetic cobalt and non-magnetic Al, Cr, Zr or W films onto different types of substrates. The experimental and analytical techniques used to investigate the structural characteristics of these multilayer systems included Rutherford Backscattering, Transmission Electron Microscopy, and large and small X -ray diffraction. The magnetic properties have been measured, analyzed and correlated with the structural properties. For example, the reduced symmetry, surface anisotropy, and strains developed at the interfaces strongly affect the magnetic properties of the samples. An interesting phenomenon observed in these films is the formation of amorphous phases when the layers are reduced to a few atomic distances in thickness. This is the case for the Co/W and Co/Zr systems, where the multilayer is amorphous when the layers are thin, and then changes to a polycrystalline form when the layers become thicker. The magnetic measurements for all systems show that the magnetic properties are strongly dependent on the cobalt layer thickness. An interesting result for Co/W and CO/Cr multilayers is the development of perpendicular anisotropy with decreasing layer thickness (in both systems, the magnetization in the perpendicular direction becomes easier as the layer thickness and the periodicity of the multilayer decreases).

Babkair, Saeed Salem

150

Computational Spectroscopy for Nanoscale Photovoltaics  

NASA Astrophysics Data System (ADS)

Nanoscale photovoltaic (PV) systems employ nanomaterial interfaces to dissociate bound excitons formed upon sunlight absorption. This mechanism results in a correlated electron, hole, and exciton interface dynamics whose accurate determination is challenging both theoretically and experimentally. In this talk, I will discuss approaches available to compute and combine relevant spectroscopic quantities to predict efficient nanoscale PV systems. Further, I will present our recent work on two novel families of nanoscale PV devices based on: 1) Nanocarbon materials, achieving 1.3% efficiency, tunable infra-red optical absorption, and superior photostability compared to organic solar cells 2) Two-dimensional monolayer semiconductors such as Graphene-BN and MoS2, capable of absorbing a significant fraction of sunlight within just 10nm, and showing tunable absorption, band offsets, and power conversion efficiency (PCE).[4pt] In closing, I will discuss the errors and necessary accuracy in predicting PCE from first-principles calculations, and propose a suitable figure of merit to quantify absorption solar-matchedness to be used in large-scale searches of nanoscale PV materials.

Bernardi, Marco

2013-03-01

151

Sensing at the nanoscale.  

PubMed

The merits of nanostructures in sensing may seem obvious, yet playing these attributes to their maximum advantage can be a work of genius. As fast as sensing technology is improving, expectations are growing, with demands for cheaper devices with higher sensitivities and an ever increasing range of functionalities and compatibilities. At the same time tough scientific challenges like low power operation, noise and low selectivity are keeping researchers busy. This special issue on sensing at the nanoscale with guest editor Christofer Hierold from ETH Zurich features some of the latest developments in sensing research pushing at the limits of current capabilities. Cheap and easy fabrication is a top priority. Among the most popular nanomaterials in sensing are ZnO nanowires and in this issue Dario Zappa and colleagues at Brescia University in Italy simplify an already cheap and efficient synthesis method, demonstrating ZnO nanowire fabrication directly onto silicon substrates [1]. Meanwhile Nicolae Barson and colleagues in Germany point out the advantages of flame spray pyrolysis fabrication in a topical review [2] and, maximizing on existing resources, researchers in Denmark and Taiwan report cantilever sensing using a US$20 commercial DVD-ROM optical pickup unit as the readout source [3]. The sensor is designed to detect physiological concentrations of soluble urokinase plasminogen activator receptor, a protein associated with inflammation due to HIV, cancer and other infectious diseases. With their extreme properties carbon nanostructures feature prominently in the issue, including the demonstration of a versatile and flexible carbon nanotube strain sensor [4] and a graphene charge sensor with sensitivities of the order of 1.3 × 10(-3) e Hz(-1/2) [5]. The issue of patterning for sensing devices is also tackled by researchers in the US who demonstrate a novel approach for multicomponent pattering metal/metal oxide nanoparticles on graphene [6]. Changes in electrical properties are an important indicator for sensing. In search of a better understanding of these systems Zhang et al from Southern Illinois University inspect the role of Joule heating, exothermal reactions and heat dissipation in gas sensing using nanowires [7]. The mechanisms behind electrical chemical sensors are also further scrutinized in a kinetics study by Joan Ramon Morante from the University of Barcelona in Spain. 'In spite of the growing commercial success many basic issues remain still open and under discussion limiting the broad use of this technology,' he explains. He discusses surface chemical reaction kinetics and the experimental results for different representative gas molecules to gain an insight into the chemical to electrical transduction mechanisms taking place [8]. Perhaps one of the most persistent targets in sensing research is increasing the sensitivity. Gauging environmental health issues around the commercial use of nanomaterials places high demands on low-level detection and spurred a collaboration of researchers in the UK, Croatia and Canada to look into the use of particle-impact voltammetry for detecting nanoparticles in environmental media [9]. At the University of Illinois Urbana-Champaign in the US, researchers have applied wave transform analysis techniques to the oscillations of an atomic force microscopy cantilever and tailored a time-frequency-domain filter to identify the region of highest vibrational energy [10]. The approach allows them to improve the signal to noise ratio by a factor 32 on current high-performance devices. In addition, researchers in Korea report how doping NiO nanofibres can improve the sensitivity to a number of gases, including ethanol, where the response was enhanced by as much as a factor of 217.86 [11]. Biomedicine is one of the largest industries for the application of nanotechnology in sensing. Demonstrating the state of the art, researchers in China use silicon wafers decorated with gold nanoparticles for label-free detection of DNA at concentrations as low as 1-10 fM, a se

Demming, Anna; Hierold, Christofer

2013-10-10

152

Sensing at the nanoscale  

NASA Astrophysics Data System (ADS)

The merits of nanostructures in sensing may seem obvious, yet playing these attributes to their maximum advantage can be a work of genius. As fast as sensing technology is improving, expectations are growing, with demands for cheaper devices with higher sensitivities and an ever increasing range of functionalities and compatibilities. At the same time tough scientific challenges like low power operation, noise and low selectivity are keeping researchers busy. This special issue on sensing at the nanoscale with guest editor Christofer Hierold from ETH Zurich features some of the latest developments in sensing research pushing at the limits of current capabilities. Cheap and easy fabrication is a top priority. Among the most popular nanomaterials in sensing are ZnO nanowires and in this issue Dario Zappa and colleagues at Brescia University in Italy simplify an already cheap and efficient synthesis method, demonstrating ZnO nanowire fabrication directly onto silicon substrates [1]. Meanwhile Nicolae Barson and colleagues in Germany point out the advantages of flame spray pyrolysis fabrication in a topical review [2] and, maximizing on existing resources, researchers in Denmark and Taiwan report cantilever sensing using a US20 commercial DVD-ROM optical pickup unit as the readout source [3]. The sensor is designed to detect physiological concentrations of soluble urokinase plasminogen activator receptor, a protein associated with inflammation due to HIV, cancer and other infectious diseases. With their extreme properties carbon nanostructures feature prominently in the issue, including the demonstration of a versatile and flexible carbon nanotube strain sensor [4] and a graphene charge sensor with sensitivities of the order of 1.3 × 10?3 e Hz?1/2 [5]. The issue of patterning for sensing devices is also tackled by researchers in the US who demonstrate a novel approach for multicomponent pattering metal/metal oxide nanoparticles on graphene [6]. Changes in electrical properties are an important indicator for sensing. In search of a better understanding of these systems Zhang et al from Southern Illinois University inspect the role of Joule heating, exothermal reactions and heat dissipation in gas sensing using nanowires [7]. The mechanisms behind electrical chemical sensors are also further scrutinized in a kinetics study by Joan Ramon Morante from the University of Barcelona in Spain. 'In spite of the growing commercial success many basic issues remain still open and under discussion limiting the broad use of this technology,' he explains. He discusses surface chemical reaction kinetics and the experimental results for different representative gas molecules to gain an insight into the chemical to electrical transduction mechanisms taking place [8]. Perhaps one of the most persistent targets in sensing research is increasing the sensitivity. Gauging environmental health issues around the commercial use of nanomaterials places high demands on low-level detection and spurred a collaboration of researchers in the UK, Croatia and Canada to look into the use of particle-impact voltammetry for detecting nanoparticles in environmental media [9]. At the University of Illinois Urbana-Champaign in the US, researchers have applied wave transform analysis techniques to the oscillations of an atomic force microscopy cantilever and tailored a time–frequency-domain filter to identify the region of highest vibrational energy [10]. The approach allows them to improve the signal to noise ratio by a factor 32 on current high-performance devices. In addition, researchers in Korea report how doping NiO nanofibres can improve the sensitivity to a number of gases, including ethanol, where the response was enhanced by as much as a factor of 217.86 [11]. Biomedicine is one of the largest industries for the application of nanotechnology in sensing. Demonstrating the state of the art, researchers in China use silicon wafers decorated with gold nanoparticles for label-free detection of DNA at concentrations as low as 1–10 fM, a sensitivity comp

Demming, Anna; Hierold, Christofer

2013-11-01

153

Graphene multilayers as hyperbolic metamaterials  

NASA Astrophysics Data System (ADS)

Graphene and multilayer graphene systems show promise for numerous electronic and optical applications in part due to the extraordinary tunability of graphene via gate voltage. We discuss the optical properties of electrically decoupled multilayer graphene systems. These can be described by the reflection and transmission coefficients, which we calculate using a transfer matrix approach. This point of view allows an explicit comparison between graphene multilayers and metal/dielectric multilayer metamaterials. In particular, we will compare multilayer graphene systems to hyperbolic metamaterials which have extreme anisotropy in the effective dielectric constant: ?x=?y<0 and ?z>0.

Dasilva, Ashley; MacDonald, Allan

2013-03-01

154

Characterization of an endoprotease (PrpL) encoded by a PvdS-regulated gene in Pseudomonas aeruginosa.  

PubMed

The expression of many virulence factors in Pseudomonas aeruginosa is dependent upon environmental conditions, including iron levels, oxygen, temperature, and osmolarity. The virulence of P. aeruginosa PAO1 is influenced by the iron- and oxygen-regulated gene encoding the alternative sigma factor PvdS, which is regulated through the ferric uptake regulator (Fur). We observed that overexpression of PvdS in strain PAO1 and a DeltapvdS::Gm mutant resulted in increased pyoverdine production and proteolytic activity compared to when PvdS was not overexpressed. To identify additional PvdS-regulated genes, we compared extracellular protein profiles from PAO1 and the DeltapvdS::Gm mutant grown under iron-deficient conditions. A protein present in culture supernatants from PAO1 but not in supernatants from DeltapvdS::Gm was investigated. Amino acid sequence analysis and examination of the genomic database of PAO1 revealed that the N terminus of this 27-kDa protein is identical to that of protease IV of P. aeruginosa strain PA103-29 and is homologous to an endoprotease produced by Lysobacter enzymogenes. In this study, the gene encoding an endoprotease was cloned from PAO1 and designated prpL (PvdS-regulated endoprotease, lysyl class). All (n = 41) but one of the strains of P. aeruginosa, including clinical and environmental isolates, examined carry prpL. Moreover, PrpL production among these strains was highly variable. Analysis of RNase protection assays identified the transcription initiation site of prpL and confirmed that its transcription is iron dependent. In the DeltapvdS::Gm mutant, the level of prpL transcription was iron independent and decreased relative to the level in PAO1. Furthermore, transcription of prpL was independent of PtxR, a PvdS-regulated protein. Finally, PrpL cleaves casein, lactoferrin, transferrin, elastin, and decorin and contributes to PAO1's ability to persist in a rat chronic pulmonary infection model . PMID:11500408

Wilderman, P J; Vasil, A I; Johnson, Z; Wilson, M J; Cunliffe, H E; Lamont, I L; Vasil, M L

2001-09-01

155

Multilayer Extender Board.  

National Technical Information Service (NTIS)

A multilayer printed circuit extender board of the printed wire type adapted for use as a replacement for a typical prior art, double-sided, single layer extender board of the printed wire type which has an upper surface with a plurality of printed wires ...

M. E. Hilliard

1980-01-01

156

Multilayer thermal insulation tests  

Microsoft Academic Search

The main purpose of this work is to make experimental measurements of the effective emittance of Multilayer Thermal Insulation (MLI) constructed from Brazilian materials. The emissivities obtained are compared with theoretical and literary references. Heat is carefully calculated and a study of the resulting uncertainties made. The results obtained are encouraging and it is possible to produce and furnish the

Marcia Barbosa H. Mantelli

1988-01-01

157

Local Feedback Multilayered Networks  

Microsoft Academic Search

In this paper, we investigate the capabilities of local feedback multilayered networks, a particular class of recurrent networks, in which feedback connections are only allowed from neurons to themselves. In this class, learning can be accomplished by an algorithm that is local in both space and time. We describe the limits and properties of these networks and give some insights

Paolo Frasconi; Marco Gori; Giovanni Soda

1992-01-01

158

Magnetic multilayer interface anisotropy  

SciTech Connect

Ni/Mo and Ni/V multilayer magnetic anisotropy has been investigated as a function of Ni layer thickness, frequency and temperature. Variable frequency ferromagnetic resonance (FMR) measurements show, for the first time, significant frequency dependence associated with the multilayer magnetic anisotropy. The thickness dependence allows one to extract the interface contribution from the total anisotropy. Temperature dependent FMR (9 GHz) and room temperature magnetization indicate that strain between Ni and the non-magnetic layers is contributing significantly to the source of the interface anisotropy and the state of the interfacial magnetization. In order to examine the interface properties of other transition metal multilayer systems, investigations on Fe/Cu are underway and CoCr/Ag is being proposed. ESR measurements have been reported on Gd substituted YBaCuO superconductors and a novel quasi-equilibrium method has been developed to determine quickly and precisely the transition temperature. During the next project period the P.I. proposes to (1) extend the variable frequency FMR measurements to low temperature, where extremely large interface anisotropies are known to obtain in Ni/Mo and Ni/V and are proposed to exist in Ni/W; (2) obtain accurate dc anisotropies via a novel, variable temperature torque magnetometer currently under construction; (3) expand upon his initial findings in Fe/Cu multilayer investigations; (4) begin anisotropy investigations on Co/Ag and CoCr/Ag multilayers where the easy magnetization direction depends upon the Cr concentration; (4) make and characterize Bi based superconductors according to resistivity, thermal conductivity and thermoelectric power and construct YBaCuO based superconducting loop-gap'' resonators for use in his magnetic resonance work.

Pechan, M.J.

1990-01-01

159

Magnetic multilayer interface anisotropy  

SciTech Connect

Ni/Mo and Ni/V multilayer magnetic anisotropy has been investigated as a function of Ni layer thickness, frequency and temperature. Variable frequency ferromagnetic resonance (FMR) measurements show, for the first time, significant frequency dependence associated with the multilayer magnetic anisotropy. The thickness dependence allows one to extract the interface contribution from the total anisotropy. Temperature dependant FMR (9 GHz) and room temperature magnetization indicate that strain between Ni and the non-magnetic layers if contributing significantly to the source of the interface anisotropy and the state of the interfacial magnetization. In order to examine the interface properties of other transition metal multilayer systems, investigations on Fe/Cu are underway and CoCr/Ag is being proposed. ESR measurements have been reported on Gd substituted YBaCuO superconductors and a novel quasi-equilibrium method has been developed to determine quickly and precisely the transition temperature. During the next project the P.I. proposes to (1) extend the variable frequency FMR measurements to low temperature, where extremely large interface anisotropies are known to obtain in Ni/Mo and Ni/V and are proposed to exist in Ni/W; (2) obtain accurate dc anisotropies via a novel, variable temperature torque magnetometer currently under construction; (3) expand upon his initial findings in Fe/Cu multilayer investigations; (4) begin anisotropy investigations on Co/Ag and CoCr/Ag multilayers where the easy magnetization direction depends upon the Cr concentration; (4) make and characterize Bi based superconductors according to resistivity, thermal conductivity and thermoelectric power and construct YBaCuO based superconducting loop-gap'' resonators for use in his magnetic resonance work. 2 figs.

Pechan, M.J.

1991-01-01

160

Construction of redox-active multilayer film for electrochemically controlled release.  

PubMed

An electrochemically controlled drug release from a redox-active multilayer film is reported. The multilayer film is fabricated by alternate assembly of the electrochemical redox-active micelles and DNA. The buildup of multilayer films is monitored by spectroscopic ellipsometry, UV-vis spectroscopy, and fluorescence spectroscopy. A ferrocene-modified poly (ethyleneimine) (PEI-Fc) is used to form a hydrophobic ferrocene core and hydrophilic PEI shell micelle, showing the electrochemical redox-active properties. Hydrophobic pyrene (Py) molecules are then incorporated into the micelles. The PEI-Fc@Py micelles are assembled into the (PEI-Fc@Py/DNA) multilayer film by layer-by-layer assembly. Thanks to ferrocene groups with the properties of the hydrophilic-to-hydrophobic switch based on the electrical potential trigger, pyrene molecules can be control released from the multilayer film. The electrochemically controlled release of pyrene is investigated and confirmed by electrochemical quartz crystal microbalance and electrochemistry workstation. The (PEI-Fc@drug/DNA) multilayer film may have potential applications in the field of biomedical and nanoscale devices. PMID:23906288

Sun, Yi-xin; Ren, Ke-feng; Zhao, Yi-xiu; Liu, Xiang-sheng; Chang, Guo-xun; Ji, Jian

2013-08-19

161

Three-dimensional, flexible nanoscale field-effect transistors as localized bioprobes.  

PubMed

Nanoelectronic devices offer substantial potential for interrogating biological systems, although nearly all work has focused on planar device designs. We have overcome this limitation through synthetic integration of a nanoscale field-effect transistor (nanoFET) device at the tip of an acute-angle kinked silicon nanowire, where nanoscale connections are made by the arms of the kinked nanostructure, and remote multilayer interconnects allow three-dimensional (3D) probe presentation. The acute-angle probe geometry was designed and synthesized by controlling cis versus trans crystal conformations between adjacent kinks, and the nanoFET was localized through modulation doping. 3D nanoFET probes exhibited conductance and sensitivity in aqueous solution, independent of large mechanical deflections, and demonstrated high pH sensitivity. Additionally, 3D nanoprobes modified with phospholipid bilayers can enter single cells to allow robust recording of intracellular potentials. PMID:20705858

Tian, Bozhi; Cohen-Karni, Tzahi; Qing, Quan; Duan, Xiaojie; Xie, Ping; Lieber, Charles M

2010-08-13

162

Three-dimensional, Flexible Nanoscale Field Effect Transistors as Localized Bioprobes  

PubMed Central

Nanoelectronic devices offer substantial potential for interrogating biological systems, although nearly all work has focused on planar device designs. We have overcome this limitation through synthetic integration of a nanoscale field effect transistor (nanoFET) device at the tip of an acute-angle kinked silicon nanowire, where nanoscale connections are made by the arms of the kinked nanostructure and remote multilayer interconnects allow three-dimensional (3D) probe presentation. The acute-angle probe geometry was designed and synthesized by controlling cis versus trans crystal conformations between adjacent kinks, and the nanoFET was localized through modulation doping. 3D nanoFET probes exhibited conductance and sensitivity in aqueous solution independent of large mechanical deflections, and demonstrated high pH sensitivity. Additionally, 3D nanoprobes modified with phospholipid bilayers can enter single cells to allow robust recording of intracellular potentials.

Tian, Bozhi; Cohen-Karni, Tzahi; Qing, Quan; Duan, Xiaojie; Xie, Ping; Lieber, Charles M.

2011-01-01

163

Characterization of Plasma Nitrided and PVD-TiN Duplex Treated Armco Iron and En40B Steel by Nanoindentation  

Microsoft Academic Search

The nanoindentation test has been applied to evaluate the mechanical properties such as hardness, elastic moduli and deformation behaviors of Fe4N iron nitride layers produced on Armco iron and En40B steel by plasma nitriding, and PVD-TiN coatings deposited on En40B with or without prior plasma nitriding treatment. Results showed that the Fe4N layer produced on En40B exhibits higher hardness than

S. Zheng; Y. Sun; A. Bloyce; T. Bell

1995-01-01

164

Impact testing of duplex and non-duplex (Ti,Al)N and Cr–N PVD coatings  

Microsoft Academic Search

An impact test has been used to evaluate the impact resistance of duplex (i.e. pre-nitrided) and non-duplex PVD (Ti,Al)N and Cr–N coatings. The impact tests were carried out using a cyclic loading system developed at the University of Hull. Two different balls (tungsten carbide and hardened SAE 52100 steel) were used as impact bodies. After the test, samples were observed

J. C. A Batista; C Godoy; A Matthews

2003-01-01

165

Evaluation of interface degradation during cyclic oxidation of EB-PVD thermal barrier coatings and correlation with TGO luminescence  

Microsoft Academic Search

The typical degradation mechanism of EB-PVD thermal barrier coatings (TBCs) that occurs during cyclic furnace testing of a commercial 7YSZ coating on a single-crystal nickel-base superalloy is analyzed. The mechanism includes local separation of the ceramic top coat from the thermally grown oxide (TGO), growth of the separated regions along the coating–substrate interface, and, upon reaching a critical size, large-scale

V. K. Tolpygo; D. R. Clarke; K. S. Murphy

2004-01-01

166

Tribocorrosion testing of stainless steel (SS) and PVD coated SS using a modified scanning reference electrode technique  

Microsoft Academic Search

A conventional scanning reference electrode technique (SRET) has been modified to provide a novel method for characterising the real-time localised tribocorrosion behaviour of uncoated and physical vapour deposition (PVD) coated samples. The modification was carried out based upon the principle of a ball-on-cylinder contact. Here a sliding probe, in this case a changeable alumina ball, is positioned diametrically opposite a

Y. N. Kok; R. Akid; P. Eh. Hovsepian

2005-01-01

167

Correlation between thermal properties and aluminum fractions in CrAlN layers deposited by PVD technique  

Microsoft Academic Search

The CrAlN coatings are a good alternative to conventional CrN coatings especially for high temperature oxidation-resistance applications. Different CrAlN coatings were deposited on silicon (100) by PVD (Physical vapor deposition) technique from two targets (chromium and aluminum) in a reactive nitrogen atmosphere at aluminum applied negative voltage (?300, ?500, ?700 and ?900V). The composition, structural, mechanical and thermal properties of

B. Tlili; N. Mustapha; C. Nouveau; Y. Benlatreche; G. Guillemot; M. Lambertin

2010-01-01

168

Impact wear resistance of plasma diffusion treated and duplex treated\\/PVD-coated Ti–6Al–4V alloy  

Microsoft Academic Search

In this paper dynamic ball-on-plate impact wear testing is utilised to gauge the intrinsic fatigue strength of the surface of triode plasma diffusion treated, single-layered TiN-, CrAlN-, and WC\\/C-coated and duplex diffusion treated\\/PVD-coated Ti–6Al–4V. The test is used to assess the resistance of surfaces to dynamic, high-cycle loading caused by the repeated impact of a cemented carbide ball. The subsequent

G. Cassar; S. Banfield; J. C. Avelar-Batista Wilson; J. Housden; A. Matthews; A. Leyland

169

EXTERNAL ASSISTANCE FOR FOOD PRODUCTION TO LDCs \\/ L'AIDE EXTERIEURE A LA PRODUCTION ALIMENTAIRE AUX PVD  

Microsoft Academic Search

Un examen rapide de l'aide à la production alimentaire durant la période 1975-1980 paraît intéressant en raison de la perspective d'une réduction de l'aide extérieure aux pays en voie de développement (PVD). L'aide à la production alimentaire est passée de 3,3 milliards de dollars en 1975 à 8,0-8,5 milliards en 1980, soit une augmentation en termes réels de près de

Martha Aida Eid

1981-01-01

170

Memory effects in nanoscale systems  

NASA Astrophysics Data System (ADS)

Memory emerges quite naturally in systems of nanoscale dimensions: the change of state of electrons and ions is not instantaneous if probed at specific time scales, and it generally depends on the past dynamics. This means that the resistive, capacitive and/or inductive properties of these systems generally show interesting time-dependent (memory) features when subject to time-dependent perturbations. In other words, nanoscale systems behave as a combination of (or simply as) memristors, memcapacitors or meminductors, namely circuit elements whose resistance, capacitance and inductance, respectively, depend on the past states through which the system has evolved. After an introduction to the theory and properties of memristors, memcapacitors and meminductors, I will discuss several memory phenomena in nanostructures associated to charge, ion and spin dynamics and their far-reaching applications ranging from information storage to computation to biologically-inspired systems. Work supported in part by NSF, NIH, and DOE.

di Ventra, Massimiliano

2011-03-01

171

Systems engineering at the nanoscale  

NASA Astrophysics Data System (ADS)

Nanomaterials have provided some of the greatest leaps in technology over the past twenty years, but their relatively early stage of maturity presents challenges for their incorporation into engineered systems. Perhaps even more challenging is the fact that the underlying physics at the nanoscale often run counter to our physical intuition. The current state of nanotechnology today includes nanoscale materials and devices developed to function as components of systems, as well as theoretical visions for "nanosystems," which are systems in which all components are based on nanotechnology. Although examples will be given to show that nanomaterials have indeed matured into applications in medical, space, and military systems, no complete nanosystem has yet been realized. This discussion will therefore focus on systems in which nanotechnology plays a central role. Using self-assembled magnetic artificial cilia as an example, we will discuss how systems engineering concepts apply to nanotechnology.

Benkoski, Jason J.; Breidenich, Jennifer L.; Wei, Michael C.; Clatterbaughi, Guy V.; Keng, Pei Yuin; Pyun, Jeffrey

2012-05-01

172

Blending effect of poly (ethyl methacrylate) on lithium bis(perfluoroethanesulfonyl) imide-ferroceramic PVdF-HFP composite  

NASA Astrophysics Data System (ADS)

PEMA as a supportive host matrix is physically blended in five different proportions with PVdF-HFP based system containing LiBETI as a electrolyte, EC / DMC mixture in 1:1 v/v ratio as a plasticizer and BaTiO3 as a filler for improving ionic conductivity is attempted. The A.C impedance, DSC, and FTIR studies are carried out. The ionic conductivity measurements on these Polymer Blend Nano Composites(PBNC) showed that blending improved ionic conductivity, and enhancement in magnitude is observed for 22.5% PEMA blended PVdF-HFP (7.5 wt%) system with 7.5% BaTiO3. The DSC showed PEMA interaction with PVDF causing reorientation of VDF crystals and resulting conformational changes showed variations in melting endotherms, are observed. FTIR studies identified PEMA interaction with plasticizer and PVdF-HFP through the change in the C-F stretching and C=O Carbonyl bond.

Vickraman, P.; Jayaraman, R.; Purushothaman, K.

2013-06-01

173

Microstructural analyses and wear behavior of the cemented carbide tools after laser surface treatment and PVD coating  

NASA Astrophysics Data System (ADS)

Adhesion is one of the most important characteristics of coating on cutting tools. Poor coating adhesion on the tool favors fragmentation and release of hard abrasive particles between the tool and the workpiece. These particles interact with the surfaces of the tool, accelerating its wear and decreasing tool life. One possible solution is the use of laser texturing prior to coating in order to achieve a desired surface topography with enhanced adhesion properties. In the texturing, a high-frequency short-pulse laser changes surface characteristics, generating resolidified material and selective vaporization. This work evaluated the effectiveness of laser texturing in improving the substrate-coating adhesion of PVD coated cemented carbide tools. To this end, the substrates were textured with a Nd:YAG laser, in four different intensities, and then coated with a PVD TiAlN film. To ascertain the effectiveness of laser texturing, Rockwell C indentation and turning experiments were performed on both textured tools and conventional unlasered tools. The PVD coated laser-textured tool showed better performance in the indentation and turning tests than the standard tools. A comparative evaluation of tool wear mechanisms indicated that texturing did not change the wear mechanisms, but altered their importance to tool wear. The anchoring provided by the higher roughness of the textured surface increased the adhesion of the coating on the substrate, thus increasing tool life. Additionally, the chemical modification of the carbide grains due to the laser heating might be responsible for an enhanced adhesion between coating and substrate.

Neves, Davi; Diniz, Anselmo Eduardo; Lima, Milton Sérgio Fernandes

2013-10-01

174

The effect of thermal aging on the thermal conductivity of plasma sprayed and EB-PVD thermal barrier coatings  

SciTech Connect

Thermal barrier coatings (TBCs) applied to the hot gas components of turbine engines lead to enhanced fuel efficiency and component reliability. Understanding the mechanisms which control the thermal transport behavior of the TBCs is of primary importance. Electron beam-physical vapor deposition (EV-PVD) and air plasma spraying (APS) are the two most commonly used coating techniques. These techniques produce coatings with unique microstructures which control their performance and stability. The density of the APS coatings was controlled by varying the spray parameters. The low density APS yttria-partially stabilized zirconia (yttria-PSZ) coatings yielded a thermal conductivity that is lower than both the high density APS coatings and the EB-PVD coatings. The thermal aging of both fully and partially stabilized zirconia are compared. The thermal conductivity of the coatings permanently increases upon exposure to high temperatures. These increases are attributed to microstructural changes within the coatings. This increase in thermal conductivity can be modeled using a relationship which depends on both the temperature and time of exposure. Although the EB-PVD coatings are less susceptible to thermal aging effects, results suggest that they typically have a higher thermal conductivity than APS coatings before thermal aging. The increases in thermal conductivity due to thermal aging for plasma sprayed partially stabilized zirconia have been found to be less than for plasma sprayed fully stabilized zirconia coatings.

Dinwiddie, R.B.; Beecher, S.C.; Porter, W.D. [Oak Ridge National Lab., TN (United States); Nagaraj, B.A. [General Electric Co., Cincinnati, OH (United States). Aircraft Engine Group

1996-05-01

175

Nanoscale Science and Engineering Center  

NSDL National Science Digital Library

With support from the National Science Foundation, the Nanoscale Science and Engineering Center (NSEC) brings together researchers from Harvard University, the Massachusetts Institute of Technology, the University of California, Santa Barbara and the Museum of Science in Boston with participation by Delft University of Technology (Netherlands), the University of Basel (Switzerland), the University of Tokyo (Japan), and Brookhaven, Oak Ridge and Sandia National Laboratories "to construct novel electronic and magnetic devices with nanoscale sizes and understand their behavior, including quantum phenomena." The Center's main activities include research, education, and public outreach. The website lists the group's overlapping interdisciplinary research areas as Synthesis and Growth of Nanoscale Structures; Imaging Electrons inside Nanostructures; and Spins and Charges in Coherent Electronics. The links section provides information on NCES nanotechnology educational activities as well as other online resources and information on upcoming conferences in nanotechnology. The Highlights section provides just an overview of recently published research, but some of the websites for individual participants include articles and conference papers. The Annual Report also reviews recent activities and research from NSEC.

176

The domain formation in Fe/Ni/Fe nanoscale magnetic antidot arrays  

NASA Astrophysics Data System (ADS)

In this paper we report the superconducting quantum interference device (SQUID) and magnetic force microscope (MFM) measurements of magnetic multilayer nanoscale antidot samples. The systems used consist of Fe(60 A?)/Ni(90 A?)/Fe(60 A?) (FeNiFe) multilayer antidots with hexagonal lattice fabricated on nanochannel glass (NCG) substrates with antidot diameters of 260, 362, 530, and 800 nm. The results indicate that the domain structure is commensurate with the holes due to the pinning effect of the antidots. This pinning effect is inversely proportional to the diameter of the antidots. The field dependent MFM data show that the hexagonal antidot lattice induces a weak anisotropy with the magnetic easy axis along the nearest neighbor direction. The unit cell in the antidot arrays could be used for data storage.

Cheng, Ruihua; Rosenberg, A.; McIlroy, D. N.; Holman, Z.; Zhang, D.; Kranov, Y.

2012-03-01

177

Multilayer optical learning networks.  

PubMed

A new approach to learning in a multilayer optical neural network based on holographically interconnected nonlinear devices is presented. The proposed network can learn the interconnections that form a distributed representation of a desired pattern transformation operation. The interconnections are formed in an adaptive and self-aligning fashioias volume holographic gratings in photorefractive crystals. Parallel arrays of globally space-integrated inner products diffracted by the interconnecting hologram illuminate arrays of nonlinear Fabry-Perot etalons for fast thresholding of the transformed patterns. A phase conjugated reference wave interferes with a backward propagating error signal to form holographic interference patterns which are time integrated in the volume of a photorefractive crystal to modify slowly and learn the appropriate self-aligning interconnections. This multilayer system performs an approximate implementation of the backpropagation learning procedure in a massively parallel high-speed nonlinear optical network. PMID:20523485

Wagner, K; Psaltis, D

1987-12-01

178

Multilayer ceramic capacitors  

Microsoft Academic Search

Significant advances have been achieved in the manufacturing technology of high volumetric multilayer ceramic capacitors (MLCs) comprised of hundreds of dielectric layers less than 3 ?m in thickness. A capacitor consists of a BaTiO3-based X7R ceramic and nickel internal electrodes. The effects of acceptor and donor dopants on reliability have been studied extensively, and a reliable 10 ?F MLC has

Yukio Sakabe

1997-01-01

179

Multilayer thermal insulation tests  

NASA Astrophysics Data System (ADS)

The main purpose of this work is to make experimental measurements of the effective emittance of Multilayer Thermal Insulation (MLI) constructed from Brazilian materials. The emissivities obtained are compared with theoretical and literary references. Heat is carefully calculated and a study of the resulting uncertainties made. The results obtained are encouraging and it is possible to produce and furnish the neceassary thermal blankets for Brazilian satellites. New materials are sought and additional MLI configurations will be tested.

Mantelli, Marcia Barbosa H.

1988-02-01

180

Theory of magnetoresistance in multilayers  

SciTech Connect

Recently it has been found that metallic multilayer films exhibit novel phenomena, particularly giant magnetoresistance in Fe/Cr, Co/Cu, Co/Cu/NiFe/Cu, and other multilayers. In this review, the authors explicate the theory of the giant magnetoresistance effect, placing emphasis on its mechanism and dependence on the constituent materials of multilayers. Some relations between the giant magnetoresistance, the electrical resistivity of the magnetic alloys, and the anisotropic magnetoresistance are also discussed.

Inoue, J.; Maekawa, S. (Nagoya Univ. (Japan))

1993-06-01

181

Nanolithography using nanoscale ridge apertures  

NASA Astrophysics Data System (ADS)

There is a continuous effort to develop techniques for nanoscale feature definition below the diffraction limit. Nanolithography has been a key technique because of its precision and cost effective. A sub-wavelength hole in an opaque screen can be used to provide a small light source with the optical resolution beyond the diffraction limit in the near field. However, a nanometer-sized hole in circular or square shapes is plagued by low transmission and poor contrast. This drawback limits the nanoscale apertures from being employed in nanolithography applications. Ridge apertures in C, H and bowtie shapes, on the other hand, have been numerically and experimentally demonstrated to show the ability of achieving both enhanced light transmission and sub-wavelength optical resolution down to nanometer domain benefiting from the existence of waveguide propagation mode confined in the gap between the ridges. In this report, the detailed field distributions in contact nanolithography are analyzed using finite difference time domain (FDTD) simulations. It was found that the high imaging contrast, which is necessary for successful lithography, is achieved close to the mask exit plane and decays quickly with the increase of the distance from the mask exit plane. Simulations are also performed for comparable regular shaped apertures and different shape bowtie apertures. Design rules are proposed to optimize the bowtie aperture for producing a sub-wavelength, high transmission field with high imaging contrast. High resolution contact nanolithography was carried on a home constructed lithography setup. It has been experimentally demonstrated that nanoscale bowtie and C apertures can be used for contact lithography to achieve nanometer scale resolution due to its intrinsic advantages of achieving enhanced optical transmission and concentrating light far beyond the diffraction limit. It also has shown the advantages of bowtie and C apertures over conventional apertures in both transmission enhancement and nanoscale light concentration. Lithographic holes as small as 40 nm x 50 nm and 50 nm x 60 nm for bowtie and C apertures, respectively, has been achieved. To study the properties of nanoscale bowtie apertures, a home-made near-field scanning optical microscope (NSOM) is developed. AFM images of standard calibration samples are used to calibrate the piezoelectric stage and topography resolution. NSOM results of bowtie apertures are also presented to study their transmission enhancement and field localization. Near-field scanning optical microscopy (NSOM) probe integrated with nanometer scale bowtie aperture for enhanced optical transmission is demonstrated. The bowtie-shape aperture allows waveguide propagating mode in the bowtie gap region, which enables simultaneous nanoscale optical resolution and enhanced optical transmission. These unique optical characteristics of bowtie aperture are demonstrated by measuring optical near fields produced by apertures in metal film. It is shown that bowtie aperture probes have one order of magnitude increase in transmission over probes with a regular shape aperture. The imaging results using bowtie aperture are in agreement with those obtained from numerical calculations. Spectroscopic measurements of transmitted field through bowtie shaped nanoscale apertures in visible wavelength region were used to further calibrate the aperture. Resonance in these apertures and its relation with the aperture geometry are investigated. The near-field spectral response is also investigated using Finite Difference Time Domain (FDTD) computation and compared with the spectroscopic measurements. The dependences of the peak wavelength and peak amplitude on the geometry of the bowtie aperture are illustrated. Design rules are proposed to optimize the bowtie aperture for producing a sub-wavelength, high transmission field.

Wang, Liang

182

Quantifying dissipative contributions in nanoscale interactions.  

PubMed

Imaging with nanoscale resolution has become routine practice with the use of scanning probe techniques. Nevertheless, quantification of material properties and processes has been hampered by the complexity of the tip-surface interaction and the dependency of the dynamics on operational parameters. Here, we propose a framework for the quantification of the coefficients of viscoelasticity, surface energy, surface energy hysteresis and elastic modulus. Quantification of these parameters at the nanoscale will provide a firm ground to the understanding and modelling of tribology and nanoscale sciences with true nanoscale resolution. PMID:22159043

Santos, Sergio; Gadelrab, Karim R; Souier, Tewfik; Stefancich, Marco; Chiesa, Matteo

2011-12-13

183

Apparatus and Method of Interconnecting Nanoscale Programmable Logic Array Clusters.  

National Technical Information Service (NTIS)

An apparatus and methods for interconnecting a plurality of nanoscale programmable logic array (PLA) clusters are disclosed. The apparatus allows PLA clusters to be built at nanoscale dimensions, signal restoration to occur at the nanoscale, and interconn...

A. DeHon

2005-01-01

184

Surface properties of Mo-implanted PVD TiN coatings using MEVVA source  

NASA Astrophysics Data System (ADS)

To further improve the tribological properties of TiN coatings used on mechanical parts, Mo ions were implanted into PVD TiN coatings with Metal Vapor Vacuum Arc (MEVVA) source at the implantation dose as high as 1 × 1018 ions/cm2. Surface morphology, microstructures, and nano-hardness of TiN coatings were investigated by optical profilometer, X-ray diffraction (XRD), X-ray photoelectron spectroscope (XPS), and Nano Indenter System. The tribological properties were investigated on a ball-on-disk friction and wear tester. The XRD results demonstrated that the diffraction peak of Ti2N appeared in the Mo-implanted TiN coatings. However, there was obvious decrease of nano-hardness due to the soft Molybdenum phase and its oxides. It was approved that Mo-implanted TiN coatings could greatly improve their tribological properties and that the implantation at dose of 1 × 1018 ions/cm2 could result in much lower friction coefficient. The existence of soft molybdenum, lubricious molybdenum oxides and titanium oxides resulted in the remarkable reducing of the friction coefficient of TiN coatings with Mo-implantation.

Tian, Bin; Yue, Wen; Fu, Zhiqiang; Gu, Yanhong; Wang, Chengbiao; Liu, Jiajun

2013-09-01

185

Characterization of Surface Properties and Microstructure of PVD-TiN Films Using Mevva Ion Implantation  

NASA Astrophysics Data System (ADS)

The PVD-TiN film was implanted with titanium ions and the improvement in surface wear resistance was investigated. Ti ion implantation was done using a metal vapor vacuum arc (MEVVA) ion source with an implantation dose of 2 × 1016 ions/cm2 and at an extraction voltage of 48 kV. The wear characteristics of the implanted zone was measured and compared to the performance of the unimplanted zone by a pin-on-disc apparatus and an optical interference microscope. The structure of the implanted zone and unimplanted one was observed by X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). A dynamic TRIM called TRIDYN was used to calculate the concentration depth profile of implanted Ti in TiN to investigate the profile of multi-charge state ions. The results showed that the improved wear resistance of the TiN film was mainly due to the presence of nano-order TiN crystal grains after Ti ion implantation.

Yang, J. H.; Cheng, M. F.; Luo, X. D.; Zhang, T. H.

186

The effects of length scale on the deformation behavior of metallic multilayers-Part II : modeling /.  

SciTech Connect

The experimental observations described in a companion presentation of the same title by Misra et al. highlight that unique, non-bulk rolling textures are achieved in nanoscale multilayered thin films. Specifically, Cu/Nb multilayers deposited with an initial Kudjumov-Sachs orientation relation between Cu and Nb grains and with an initial individual layer thickness of 75nm preserve that relation during rolling. In contrast, samples with micron-scale individual layer thickness do not. To help understand this layer-dependent response, a crystal plasticity model is presented in which the Cu and Nb phases respond by slip on {l_brace}111{r_brace}/<110> systems in the fcc Cu case, and {l_brace}110{r_brace} / <111 > systems in the bcc Nb phase. Grains within each layered phase are required to plastically deform by a reduction in thickness and corresponding elongation in the rolling direction, with zero plastic strain along the transverse axis. The model also adopts the observation for nano-scale multilayers that the Kudjumov-Sachs orientation relation is preserved; in particular, the e 1 11> Cu and e1 10> Nb directions remain parallel to the interface normal during rolling. The crystal plasticity model then furnishes the minimum plastic work to deform a grain, as a function of grain orientation. For Cu grains, the plastic work is invariant of grain orientation, provided the critical resolved shear stress is uniform on all fcc slip systems. However, the corresponding plastic work in Nb grains is very dependent on grain orientation and has a strong minimum. This large anisotropy serves as a driving force for Nb grains to rotate around their <110> interface normal, toward the minimum. The resulting prediction for rolling texture in Nb layers agrees well with experimental observations in nanoscale Cu/Nb multilayers.

Misra, A. (Amit); Hirth, John Price,; Anderson, P. M. (Peter M.)

2002-01-01

187

Young's Equation at the Nanoscale.  

PubMed

In 1805, Thomas Young was the first to propose an equation to predict the value of the equilibrium contact angle of a liquid on a solid. Today, the force exerted by a liquid on a solid, such as a flat plate or fiber, is routinely used to assess this angle. Moreover, it has recently become possible to study wetting at the nanoscale using an atomic force microscope. Here, we report the use of molecular-dynamics simulations to investigate the force distribution along a 15 nm fiber dipped into a liquid meniscus. We find very good agreement between the measured force and that predicted by Young's equation. PMID:24033049

Seveno, David; Blake, Terence D; De Coninck, Joël

2013-08-27

188

Young's Equation at the Nanoscale  

NASA Astrophysics Data System (ADS)

In 1805, Thomas Young was the first to propose an equation to predict the value of the equilibrium contact angle of a liquid on a solid. Today, the force exerted by a liquid on a solid, such as a flat plate or fiber, is routinely used to assess this angle. Moreover, it has recently become possible to study wetting at the nanoscale using an atomic force microscope. Here, we report the use of molecular-dynamics simulations to investigate the force distribution along a 15 nm fiber dipped into a liquid meniscus. We find very good agreement between the measured force and that predicted by Young’s equation.

Seveno, David; Blake, Terence D.; De Coninck, Joël

2013-08-01

189

Process for manufacturing multilayer capacitors  

DOEpatents

The invention is directed to a method of manufacture of multilayer electrical components, especially capacitors, and components made by such a method. High capacitance dielectric materials and low cost metallizations layered with such dielectrics may be fabricated as multilayer electrical components by sintering the metallizations and the dielectrics during the fabrication process by application of microwave radiation.

Lauf, Robert J. (Oak Ridge, TN); Holcombe, Cressie E. (Knoxville, TN); Dykes, Norman L. (Oak Ridge, TN)

1996-01-01

190

Process for manufacturing multilayer capacitors  

DOEpatents

The invention is directed to a method of manufacture of multilayer electrical components, especially capacitors, and components made by such a method. High capacitance dielectric materials and low cost metallizations layered with such dielectrics may be fabricated as multilayer electrical components by sintering the metallizations and the dielectrics during the fabrication process by application of microwave radiation. 4 figs.

Lauf, R.J.; Holcombe, C.E.; Dykes, N.L.

1996-01-02

191

Nanoscale molecular-switch crossbar circuits  

Microsoft Academic Search

Molecular electronics offer an alternative pathway to construct nanoscale circuits in which the critical dimension is naturally associated with molecular sizes. We describe the fabrication and testing of nanoscale molecular-electronic circuits that comprise a molecular monolayer of [2]rotaxanes sandwiched between metal nanowires to form an 8 × 8 crossbar within a 1 µm2 area. The resistance at each cross point

Yong Chen; Gun-Young Jung; Douglas A. A. Ohlberg; Xuema Li; Duncan R. Stewart; Jan O. Jeppesen; Kent A. Nielsen; J. Fraser Stoddart; R. Stanley Williams

2003-01-01

192

Random laser spectroscopy for nanoscale perturbation sensing  

Microsoft Academic Search

We report a spectroscopic method using coherent random lasers for a simple, yet nanoscale, sensing approach. Unique spectral properties of coherent random laser emission can be detectably altered when introducing nanoscale perturbations to a simple nanocomposite film that consists of dielectric nanospheres and laser-dye-doped polymer to serve as a transducer. Random lasing action provides a means to amplify subtle perturbations

Qinghai Song; Shumin Xiao; Zhengbin Xu; Vladimir M. Shalaev; Young L. Kim

2010-01-01

193

Deformation of metallic glass thin films and multilayers  

NASA Astrophysics Data System (ADS)

Amorphous metals are the ultimate nanostructure for mechanical strength. Their macroscopic ductility can be limited, however, by the formation of shear bands. If these materials are to be used in structural applications, the formation of shear bands must be understood and ultimately controlled. The mechanical properties of sputtered thin films of amorphous Pd0.77Si0.23 (a-PdSi) were studied using tensile testing. By depositing thin films of metallic glass on compliant substrates, fracture of the composite specimens was avoided. This testing technique allowed, for the first time, measurement of homogeneous flow and homogeneous deformation-induced softening at room temperature in this material. The stress-strain behavior and formation of shear bands does not depend on sample size, strain rate (over a range of 10 -5 to 8 x 10-5 sec-1 ), or film adhesion. By geometrically confining thin films of metallic glass with layers of a crystalline metal, the formation of shear steps at the interface is counteracted elastically, and the formation of shear bands is suppressed. A Cu/a-PdSi/Cu trilayer exhibited a yield strength of 1180 MPa, a flow stress of 1680 MPa, and a plastic strain of 13% without fracture. Multilayers of crystalline Cu and a-PdSi were deformed to large strains by cold rolling and bending. Transmission electron microscopy showed the layered structure remained intact and that no shear bands formed. In rolled Cu/Nb multilayers extensive grain rotation about the transverse direction occurs on micron-scale Cu grains. This grain rotation is reduced in nanoscale Cu/a-PdSi multilayers presumably due to a change in the distribution of dislocations in the Cu grains. The strength of the crystalline/amorphous multilayers was modeled with confined layer slip, in which deformation occurs by the motion of threading dislocations in the thin crystalline layers.

Donohue, Alex

194

Improvement of the tribological behaviour of PVD nanostratified TiN\\/CrN coatings — An explanation  

Microsoft Academic Search

A hard TiN\\/CrN multilayered coating, consisting of alternating nanometer scale TiN and CrN layers (bilayer period of 40 nm), was deposited by arc evaporation process on M2 tool steel. Monolayered TiN and CrN are also deposited in the same conditions, and used as references. In order to get a better understanding of the tribological behaviour of coated parts, two types of

C. Mendibide; P. Steyer; J. Fontaine; P. Goudeau

2006-01-01

195

Evaluation of TiN\\/AlN nano-multilayer coatings on drills used for micro-drilling  

Microsoft Academic Search

As it is well known, some materials with nano-scale size show analomous properties that are rather different from the bulk state. In this study, a new sputtering system was utilized to grow a group of TiN\\/AlN nano-multilayer films with various periods through controlling the deposition conditions. The aim of this study was mainly focused on the relationship between the period

S. H. Yao

2005-01-01

196

Superstatistics in nanoscale electrochemical systems  

PubMed Central

Stochastic electrochemical reaction steps on nanosized electrodes are non-Markovian when externally driven by an applied voltage. We show that, compared to the Markovian case (when external driving is absent), nanoscale electrochemical systems obey a superstatistics characterized by a superposition of Tsallis’ q indices. The distribution of Tsallis’ q indices along stochastic trajectories can be calculated from the electrochemical master equation and normal distributions from Boltzmann–Gibbs thermostatistics are recovered in the thermodynamic limit (the infinite electrode size limit). Although on the nanoscale the external control makes intricate correlations between the microstates, in the superstatistical frame one can still address the microstates as if they were uncorrelated. The resulting superstatistical entropic form is additive in this frame and Tsallis’ indices have on the time-average values , which is, indeed, an example of a superstatistical system where no ad hoc distribution has to be assumed for the fluctuations; rather, the distribution is directly calculated from a mesoscopic master equation without freely adjustable parameters.

Garcia-Morales, Vladimir; Krischer, Katharina

2011-01-01

197

Motion control at the nanoscale.  

PubMed

Synthetic nanoscale motors represent a major step in the development of practical nanomachines. This Review summarizes recent progress towards controlling the movement of fuel-driven nanomotors and discusses the challenges and opportunities associated with the achievement of such nanoscale motion control. Regulating the movement of artificial nanomotors often follows nature's elegant and remarkable approach for motion control. Such on-demand control of the movement of artificial nanomotors is essential for performing various tasks and diverse applications. These applications require precise control of the nanomotor direction as well as temporal and spatial regulation of the motor speed. Different approaches for controlling the motion of catalytic nanomotors have been developed recently, including magnetic guidance, thermally driven acceleration, an electrochemical switch, and chemical stimuli (including control of the fuel concentration). Such ability to control the directionality of artificial nanomotors and to regulate their speed offers considerable promise for designing powerful nanomachines capable of operating independently and meeting a wide variety of future technological needs. PMID:20013944

Wang, Joseph; Manesh, Kalayil Manian

2010-02-01

198

Center for Nanoscale Systems (CNS)  

NSDL National Science Digital Library

The Center for Nanoscale Systems (CNS) is a part of Harvard University's Faculty of Arts and Sciences (FAS). Their scientific focus is on how nanoscale components can be integrated into large and complex interacting systems. Studying very small structures and how their behavior differs from macroscopic objects is only part of the story. We also must investigate how systems emerge, how they can be built, and how they behave. CNS is a member of the National Science FoundationâÂÂs National Nanotechnology Infrastructure Network (NNIN) initiative to create a national network of world-class facilities available to all researchers. Through our CNS/NNIN User Program, our facilities are available for use by researchers not just at Harvard, but by any academic or non-academic researchers in the country. We welcome and encourage researchers from Harvard and beyond to take a look at the many facilities that CNS has to offer to assist in your research goals. CNS has the tools and knowledgeable technical staff ready to assist in making your project a success. Nanotechnology is a new and constantly evolving area of study. As a result, there is a lot of new and constantly updated information contained in the pages of our website. Whether you are a CNS facility user, principal investigator, potential user, or interested in nanotechnology on any level, we invite you to take a tour of our website.

2008-12-08

199

Magnetic metallic multilayers  

SciTech Connect

Utilizing self-consistent Hartree-Fock calculations, several aspects of multilayers and interfaces are explored: enhancement and reduction of the local magnetic moments, magnetic coupling at the interfaces, magnetic arrangements within each film and among non-neighboring films, global symmetry of the systems, frustration, orientation of the various moments with respect to an outside applied field, and magnetic-field induced transitions. Magnetoresistance of ferromagnetic-normal-metal multilayers is found by solving the Boltzmann equation. Results explain the giant negative magnetoresistance encountered in these systems when an initial antiparallel arrangement is changed into a parallel configuration by an external magnetic field. The calculation depends on (1) geometric parameters (thicknesses of layers), (2) intrinsic metal parameters (number of conduction electrons, magnetization, and effective masses in layers), (3) bulk sample properties (conductivity relaxation times), (4) interface scattering properties (diffuse scattering versus potential scattering at the interfaces, and (5) outer surface scattering properties (specular versus diffuse surface scattering). It is found that a large negative magnetoresistance requires considerable asymmetry in interface scattering for the two spin orientations. Features of the interfaces that may produce an asymmetrical spin-dependent scattering are studied: varying interfacial geometric random roughness with no lateral coherence, correlated (quasi-periodic) roughness, and varying chemical composition of the interfaces. The interplay between these aspects of the interfaces may enhance or suppress the magnetoresistance, depending on whether it increases or decreases the asymmetry in the spin-dependent scattering of the conduction electrons.

Hood, R.Q.

1994-04-01

200

Lipid multilayer gratings.  

PubMed

The interaction of electromagnetic waves with matter can be controlled by structuring the matter on the scale of the wavelength of light, and various photonic components have been made by structuring materials using top-down or bottom-up approaches. Dip-pen nanolithography is a scanning-probe-based fabrication technique that can be used to deposit materials on surfaces with high resolution and, when carried out in parallel, with high throughput. Here, we show that lyotropic optical diffraction gratings--composed of biofunctional lipid multilayers with controllable heights between approximately 5 and 100 nm--can be fabricated by lipid dip-pen nanolithography. Multiple materials can be simultaneously written into arbitrary patterns on pre-structured surfaces to generate complex structures and devices, allowing nanostructures to be interfaced by combinations of top-down and bottom-up fabrication methods. We also show that fluid and biocompatible lipid multilayer gratings allow label-free and specific detection of lipid-protein interactions in solution. This biosensing capability takes advantage of the adhesion properties of the phospholipid superstructures and the changes in the size and shape of the grating elements that take place in response to analyte binding. PMID:20190751

Lenhert, Steven; Brinkmann, Falko; Laue, Thomas; Walheim, Stefan; Vannahme, Christoph; Klinkhammer, Soenke; Xu, Miao; Sekula, Sylwia; Mappes, Timo; Schimmel, Thomas; Fuchs, Harald

2010-02-28

201

Ultrahard Multilayer Coatings  

SciTech Connect

We have developed a new multilayer a-tC material that is thick stress-free, adherent, low friction, and with hardness and stiffness near that of diamond. The new a-tC material is deposited by J pulsed-laser deposition (PLD) at room temperature, and fully stress-relieved by a short thermal anneal at 600°C. A thick multilayer is built up by repeated deposition and annealing steps. We measured 88 GPa hardness, 1100 GPa Young's modulus, and 0.1 friction coefficient (under high load). Significantly, these results are all well within the range reported for crystalline diamond. In fact, this material, if considered separate from crystalline diamond, is the 2nd hardest material known to man. Stress-free a-tC also has important advantages over thin film diamond; namely, it is smooth, processed at lower temperature, and can be grown on a much broader range of substrates. This breakthrough will enable a host of applications that we are actively pursuing in MEMs, sensors, LIGA, etc.

Chrzan, D.C.; Dugger, M.; Follstaedt, D.M.; Friedman, Lawrence H.; Friedmann, T.A.; Knapp, J.A.; McCarty, K.F.; Medlin, D.L.; Mirkarimi, P.B.; Missert, N.; Newcomer, P.P.; Sullivan, J.P.; Tallant, D.R.

1999-05-01

202

Screening in multilayer graphene  

NASA Astrophysics Data System (ADS)

In this paper, we study the static polarization in ABC-stacked multilayer graphene. Since the density of states diverges for these systems if the number of layers exceeds three, screening effects are expected to be important. In the random phase approximation, screening can be included through the polarization. We derive an analytical integral expression for the polarization in both the full-band model and an effective two-band model. Numerical evaluation of these integrals is very time consuming in the full-band model. Hence, for ABC-stacked trilayer graphene, we use the two-band model to calculate the low momentum part of the polarization. The results for the two-band model are universal, i.e., independent of doping. The high momentum part is linear and is determined by calculating two points, such that we can determine the slope. For ABC stacked trilayer graphene, the slope is given by three times the monolayer value. We compare our results to previous ones in the literature and discuss the similarities and discrepancies. Our results can be used to include screening in ABC-stacked multilayer systems in a way that all the characteristics of the polarization function are included. The numerical results for the polarization of trilayer graphene are used to sketch the screened potential.

van Gelderen, Ralph; Olsen, Richard; Smith, C. Morais

2013-09-01

203

Ultrasonic Linear Motor Using Multilayer Piezoelectric Actuators  

Microsoft Academic Search

In order to lower operating voltage and improve the lifetime of an ultrasonic linear motor, we have developed an ultrasonic oscillator with multilayer piezoelectric actuators. Multilayer piezoelectric actuators are operable at low voltage. However, the tensile strength of the multilayer piezoelectric actuator is small. Therefore, the multilayer piezoelectric actuators are build within an elastic body to lower the tensile stress

Tomoki Funakubo; Toshiharu Tsubata; Yoshihisa Taniguchi; Kazuhiro Kumei; Takanao Fujimura; Chikara Abe

1995-01-01

204

Nanoscale  

NSDL National Science Digital Library

Nanotechnology continues to be a field of inquiry that is growing quickly, and this new online peer reviewed journal is a most welcome addition. The journal is published monthly as a collaborative venture between RSC Publishing and the National Center for Nanoscience and Technology (NCNST) in Beijing, China. Some of the topics covered in the journal include nanoelectronics, molecular nanoscience, and nanomedicine. The first issues was released in September 2009, and visitors can read through pieces like "How safe are carbon nanotubes?" and "Mechanised nanoparticles for drug delivery". On the journal's site, visitors can browse through the archive, sign up for their RSS feed, and also read over the author guidelines. Finally they can also use some of their online "Tools" to send along a link to the journal to a friend or colleague.

2009-10-19

205

Nanoscale  

NSDL National Science Digital Library

Nanotechnology continues to be a field of inquiry that is growing quickly, and this new online peer reviewed journal is a most welcome addition. The journal is published monthly as a collaborative venture between RSC Publishing and the National Center for Nanoscience and Technology (NCNST) in Beijing, China. Some of the topics covered in the journal include nanoelectronics, molecular nanoscience, and nanomedicine. The first issues was released in September 2009, and visitors can read through pieces like "How safe are carbon nanotubes?" and "Mechanised nanoparticles for drug delivery". On the journal's site, visitors can browse through the archive, sign up for their RSS feed, and also read over the author guidelines. Finally they can also use some of their online "Tools" to send along a link to the journal to a friend or colleague.

206

Composition, structure and properties of gradient thermal barrier coatings (TBCs) produced by electron beam physical vapor deposition (EB-PVD)  

Microsoft Academic Search

Gradient thermal barrier coatings (TBCs) along with the bond coat were produced by one and the same technological cycle using electron beam physical vapor deposition (EB-PVD) of an MCrAlY ingot, then of an Al–Al2O3–ZrO2(Y2O3) tablet (pressed multicomponent powder mixture) and finally of a ZrO2–7 wt.% Y2O3 ceramic ingot. At the evaporation temperature used, vapor pressures of the tablet components decrease

M Movchan; Yu Rudoy

1998-01-01

207

Effects of heat treatment on mechanical properties of ODS nickel-based superalloy sheets prepared by EB-PVD  

Microsoft Academic Search

A Y2O3 dispersion strengthened nickel-based superalloy sheet (0.15 mm thick) was prepared by electron beam physical vapor deposition\\u000a (EB-PVD) technology. Different heat treatments were used to improve the mechanical properties of the alloy sheet. Differential\\u000a thermal analysis (DTA) was used to examine the thermal stability of the as-deposited sheet. Element contents, phase composition\\u000a and microstructure investigations on as-deposited and heat

Song Chen; Shoujiang Qu; Jun Liang; Jiecai Han

2011-01-01

208

New liquid crystal-embedded PVdF- co -HFP-based polymer electrolytes for dye-sensitized solar cell applications  

Microsoft Academic Search

Liquid crystal (LC; E7 and\\/or ML-0249)-embedded, poly(vinylidenefluoride-co-hexafluoropropylene) (PVdF-co-HFP)-based, polymer electrolytes were prepared for use in dye-sensitized solar cells (DSSCs). The electrolytes contained\\u000a 1-methyl-3-propylimidazolium iodide (PMII), tetrabutylammonium iodide (TBAI), and iodine (I\\u000a 2), which participate in theI\\u000a 3\\u000a ? \\/I\\u000a ? redox couple. The incorporation of photochemically stable PVdF-co-HFP in the DSSCs created a stable polymer electrolyte that resisted leakage and

G. Vijayakumar; Meyoung Jin Lee; Myungkwan Song; Sung-Ho Jin; Jae Wook Lee; Chan Woo Lee; Yeong-Soon Gal; Hyo Jin Shim; Yongku Kang; Gi-Won Lee; Kyungkon Kim; Nam-Gyu Park; Suhkmann Kim

2009-01-01

209

An Enhanced Fuzzy Multilayer Perceptron  

Microsoft Academic Search

\\u000a Error back-propagation algorithm of the multilayer perceptron may result in local-minima because of the insufficient nodes\\u000a in the hidden layer, inadequate momentum set-up, and initial weights. In this paper, we proposed the fuzzy multilayer perceptron\\u000a which is composed of the ART1 and the fuzzy neural network. The proposed fuzzy multilayer perceptron using the self-generation\\u000a method applies not only the ART1

Kwang-baek Kim; Choong Shik Park

2004-01-01

210

Giant transverse optical forces in nanoscale slot waveguides of hyperbolic metamaterials.  

PubMed

Here we demonstrate that giant transverse optical forces can be generated in nanoscale slot waveguides of hyperbolic metamaterials, with more than two orders of magnitude stronger compared to the force created in conventional silicon slot waveguides, due to the nanoscale optical field enhancement and the extreme optical energy compression within the air slot region. Both numerical simulation and analytical treatment are carried out to study the dependence of the optical forces on the waveguide geometries and the metamaterial permittivity tensors, including the attractive optical forces for the symmetric modes and the repulsive optical forces for the anti-symmetric modes. The significantly enhanced transverse optical forces result from the strong optical mode coupling strength between two metamaterial waveguides, which can be explained with an explicit relation derived from the coupled mode theory. Moreover, the calculation on realistic metal-dielectric multilayer structures indicates that the predicted giant optical forces are achievable in experiments, which will open the door for various optomechanical applications in nanoscale, such as optical nanoelectromechanical systems, optical sensors and actuators. PMID:23037385

He, Yingran; He, Sailing; Gao, Jie; Yang, Xiaodong

2012-09-24

211

Preformed nanoscale ferromagnetism in manganites  

NASA Astrophysics Data System (ADS)

In order to clarify the electronic phase separation consisting of distinct ferromagnetic (FM) metallic and charge-ordered (CO) insulating phases in the colossal magnetoresistive (La, Pr, Ca)MnO3, we have carefully examined the electronic inhomogeneities by Lorentz microscopy, combined with conventional magnetic studies. We discovered the presence of an intermediate FM state characterized by the emergence of nanoscale (10-20 nm) magnetic regions (magnetic nano-droplets) in the intermediate temperature window above the FM transition temperature. The magnetic nano-droplets in fact precede the onset of ferromagnetic long-range order. It is also found that this intermediate state with magnetic nano-droplets is intimately coupled with the presence of the short-range CO regions.

Horibe, Y.; Mori, S.; Asaka, T.; Matsui, Y.; Sharma, P. A.; Koo, T. Y.; Guha, S.; Chen, C. H.; Cheong, S.-W.

2012-12-01

212

Reactions inside nanoscale protein cages  

NASA Astrophysics Data System (ADS)

Chemical reactions are traditionally carried out in bulk solution, but in nature confined spaces, like cell organelles, are used to obtain control in time and space of conversion. One way of studying these reactions in confinement is the development and use of small reaction vessels dispersed in solution, such as vesicles and micelles. The utilization of protein cages as reaction vessels is a relatively new field and very promising as these capsules are inherently monodisperse, in that way providing uniform reaction conditions, and are readily accessible to both chemical and genetic modifications. In this review, we aim to give an overview of the different kinds of nanoscale protein cages that have been employed as confined reaction spaces.

Bode, Saskia A.; Minten, Inge J.; Nolte, Roeland J. M.; Cornelissen, Jeroen J. L. M.

2011-06-01

213

Mapping Elasticity at the Nanoscale  

NASA Astrophysics Data System (ADS)

In the last few years Atomic Force Acoustic Microscopy has been developed to investigate the elastic response of materials at the nanoscale ^[1],[2]. We have extended this technique to the real-time mapping of nanomechanical properties of material surfaces. This mapping allows us to investigate the local variation of elastic properties with nanometer resolution and to reduce the uncertainties that arise from single measurements. Quantitative measurements are acquired by first performing an accurate calibration of the elastic properties of the Atomic Force Microscope’s probes with respect to single crystal reference materials. A wide variety of surfaces with different mechanical properties have been investigated to illustrate the applicability of this technique. ^[1] U. Rabe et al., Surf. Interface Anal. 33 , 65 (2002)^[2] D.C. Hurley et al., J. Appl. Phys. 94, 2347 (2003)

Stan, Gheorghe; Price, William

2006-03-01

214

Multilayer optical dielectric coating  

DOEpatents

A highly damage resistant, multilayer, optical reflective coating includes alternating layers of doped and undoped dielectric material. The doping levels are low enough that there are no distinct interfaces between the doped and undoped layers so that the coating has properties nearly identical to the undoped material. The coating is fabricated at high temperature with plasma-assisted chemical vapor deposition techniques to eliminate defects, reduce energy-absorption sites, and maintain proper chemical stoichiometry. A number of differently-doped layer pairs, each layer having a thickness equal to one-quarter of a predetermined wavelength in the material are combined to form a narrowband reflective coating for a predetermined wavelength. Broadband reflectors are made by using a number of narrowband reflectors, each covering a portion of the broadband.

Emmett, John L. (Pleasanton, CA)

1990-01-01

215

Fiber damage during the consolidation of PVD Ti-6Al-4V coated NEXTEL 610{trademark} alumina fibers  

SciTech Connect

Titanium matrix composites reinforced with sol-gel synthesized {alpha}-alumina fiber tows have attracted interest as a potentially low cost continuous fiber reinforced metal matrix composite system. The authors have conducted a detailed investigation of fiber damage during high temperature consolidation of PVD Ti-6Al-4V metallized sol-gel alumina fiber tows. Using both hot isostatic pressing and interrupted vacuum hot press consolidation cycles, the two principal mechanisms of fiber damage have been experimentally identified to be microbending/fracture and fiber matrix reaction. A time dependent micromechanics model incorporating the evolving geometry and mechanical properties of both the fibers and matrix has been formulated to simulate the fiber bending/failure mechanism in a representative unit cell and explore the effect of fiber strength loss due to reaction with the matrix. This model has been used to design a process cycle that minimizes damage by exploiting the enhanced superplastic deformation of the initially nanocrystalline PVD Ti-6Al-4V matrix.

Warren, J.; Elzey, D.M.; Wadley, H.N.G. [Univ. of Virginia, Charlottesville, VA (United States). Dept. of Materials Science and Engineering

1995-10-01

216

Development and evaluation of two PVD-coated ?-titanium orthodontic archwires for fluoride-induced corrosion protection.  

PubMed

The present research was aimed at developing surface coatings on ? titanium orthodontic archwires capable of protection against fluoride-induced corrosion. Cathodic arc physical vapor deposition PVD (CA-PVD) and magnetron sputtering were utilized to deposit thin films of titanium aluminium nitride (TiAlN) and tungsten carbide/carbon (WC/C) coatings on ? titanium orthodontic archwires. Uncoated and coated specimens were immersed in a high fluoride ion concentration mouth rinse, following a specially designed cycle simulating daily use. All specimens thus obtained were subjected to critical evaluation of parameters such as electrochemical corrosion behaviour, surface analysis, mechanical testing, microstructure, element release, and toxicology. The results confirm previous research that ? titanium archwires undergo a degradation process when in contact with fluoride mouth rinses. The study confirmed the superior nature of the TiAlN coating, evident as many fewer changes in properties after fluoride treatment when compared with the WC/C coating. Thus, coating with TiAlN is recommended in order to reduce the corrosive effects of fluorides on ? titanium orthodontic archwires. PMID:21111072

Krishnan, Vinod; Krishnan, Anand; Remya, R; Ravikumar, K K; Nair, S Asha; Shibli, S M A; Varma, H K; Sukumaran, K; Kumar, K Jyothindra

2010-11-24

217

Multilayer Superinsulation Development and Testing.  

National Technical Information Service (NTIS)

For the measurement of the thermal conductance of multilayer superinsulation blankets a flat, guarded-hot-plate calorimeter was developed and manufactured. The physical arrangement of the calorimeter, the range of operating temperature and the method of m...

E. Klippel H. Langer

1974-01-01

218

Multilayer coatings on flexible substrates  

Microsoft Academic Search

Thin-film optical and non-optical multilayer coatings are deposited onto flexible substrates using a vacuum web coater developed at Pacific Northwest Laboratory. The coater`s primary application is rapid prototyping of multilayer (1) polymer coatings, (2) polymer\\/metal coatings, (3) ceramic\\/metal coatings, and (4) hybrid polymer, ceramic, and metal coatings. The coater is fully automated and incorporates polymer evaporation and extrusion heads, high-rate

P. M. Martin; J. D. Affinito; M. E. Gross; C. A. Coronado; W. D. Bennett; D. C. Stewart

1995-01-01

219

Artificial multilayers and nanomagnetic materials.  

PubMed

The author has been actively engaged in research on nanomagnetic materials for about 50 years. Nanomagnetic materials are comprised of ferromagnetic systems for which the size and shape are controlled on a nanometer scale. Typical examples are ultrafine particles, ultrathin films, multilayered films and nano-patterned films. In this article, the following four areas of the author's studies are described.(1) Mössbauer spectroscopic studies of nanomagnetic materials and interface magnetism.(2) Preparation and characterization of metallic multilayers with artificial superstructures.(3) Giant magnetoresistance (GMR) effect in magnetic multilayers.(4) Novel properties of nanostructured ferromagnetic thin films (dots and wires).A subject of particular interest in the author's research was the artificially prepared multilayers consisting of metallic elements. The motivation to initiate the multilayer investigation is described and the physical properties observed in the artificial multilayers are introduced. The author's research was initially in the field of pure physical science and gradually extended into applied science. His achievements are highly regarded not only from the fundamental point of view but also from the technological viewpoint. PMID:23391605

Shinjo, Teruya

2013-01-01

220

Nanoscale effects of antibiotics on P. aeruginosa  

Microsoft Academic Search

Studying living bacteria at the nanoscale, in their native liquid environment opens an unexplored landscape. We focus on Pseudomonas aeruginosa and demonstrate how the cell wall is biophysically affected at the nanoscale by two reference antibiotics (ticarcillin, tobramycin). The elasticity of the cells drops dramatically after treatment (from 263+\\/-70 kPa to 50+\\/-18 and 24+\\/-4 kPa respectively on ticarcillin and tobramycin

Cecile Formosa; Marion Grare; Raphaël E. Duval; Etienne Dague

221

Shear piezoelectricity in bone at the nanoscale  

NASA Astrophysics Data System (ADS)

Recent demonstration of shear piezoelectricity in an isolated collagen fibril, which is the origin of piezoelectricity in bone, necessitates investigation of shear piezoelectric behavior in bone at the nanoscale. Using high resolution lateral piezoresponse force microcopy (PFM), shear piezoelectricity in a cortical bone sample was studied at the nanoscale. Subfibrillar structure of individual collagen fibrils with a periodicity of 60-70 nm were revealed in PFM map, indicating the direct contribution of collagen fibrils to the shear piezoelectricity of bone.

Minary-Jolandan, Majid; Yu, Min-Feng

2010-10-01

222

Science and Technology at the Nanoscale  

NSDL National Science Digital Library

Northwestern University offers this graduate course on nanoscience to introduce students to the field. Taught by Professor Teri Odom, this course presents students with contemporary issues in nanoscience and nanotechnology as well as provide training on advanced nanoscale instrumentation. The website includes PDF lecture slideshows that provide more detailed information on subjects such as scanning probe microscopy, nanofabrication, and nanoscale electronics and photonics. This would be a good resource for teachers who want to incorporate nanoscience into their pre-existing chemistry classes.

Odom, Teri W.

2012-04-12

223

Spin-reorientation transition in Co/Pt multilayers on nanospheres  

SciTech Connect

Co/Pt multilayers have been deposited onto self-assembled arrays of spherical particles. The radial film thickness variation changes both the magnitude and direction of the magnetic anisotropy within a single cap. By adjusting the thickness of the Co layers, we produced caps that exhibit a reorientation of the magnetization from in plane at the center toward out of plane at the rim within a distance of less than 100 nm. The domain configuration and its reversal behavior in applied magnetic fields were studied with high spatial resolution scanning transmission x-ray microscopy, providing quantitative insight into nanoscale magnetism.

Eimueller, T. [Junior Research Group Magnetic Microscopy, Experimental Physics, University of Bochum, D-44780 Bochum (Germany); Ulbrich, T. C.; Guhr, I. L. [Department of Physics, University of Konstanz, D-78457 Konstanz (Germany); Amaladass, E. [Max-Planck-Institute for Metals Research, Heisenbergstrasse 3, D-70569 Stuttgart (Germany); Tyliszczak, T. [Advanced Light Source (ALS), LBNL, 1 Cyclotron Road, Berkeley, California 94720 (United States); Albrecht, M. [Institute of Physics, Chemnitz University of Technology, D-09107 Chemnitz (Germany)

2008-04-01

224

Duplex Treatment of Tools and Components: Previous or Subsequent Electron Beam Hardening of Thermochemically-Treated and PVD Hard-Coated Steels for Tools and Components  

Microsoft Academic Search

The tribological properties of tools and components are improved by wear resistant coatings deposited by thermochemical processing (nitriding, nitrocarburizing) or physical vapor deposition (PVD) technologies. The properties gradient between the very hard and brittle layer and the soft, ductile, but hardenable matrix material can be significantly improved by previous or subsequent electron beam hardening (EBH). The hardness of matrix material

Gundis Sacher; Rolf Zenker; Heinz-Joachim Spies

2009-01-01

225

Development of a rule-based software system for the fabrication of a contoured EB-PVD TBC on a PW4000 second-stage blade  

NASA Astrophysics Data System (ADS)

A rule-based software system capable of predicting the manufacturing process parameters required to apply any reasonable contoured electron beam physical vapor deposition (EB-PVD) thermal barrier coating (TBC) to a gas turbine blade has been developed and tested. This system is based upon an experimentally verified TBC thickness prediction model for ytria partially stabilized zirconia (YPSZ) TBCs applied using EB-PVD. The following three goals were set at the outset of the work and have been accomplished. First, an experimentally verified model capable of predicting TBC coating thickness as a function of position in the EB-PVD coater was created. Nearly seventeen hundred flat samples, seven twelve inch long cylinders, and four PW4000 gas turbine blades were coated and analyzed during the verification of the model. The correlation coefficients between the improved model and the experimental data ranged between 0.8 and 0.95. Second, a model was developed that was proven capable of predicting the effects of vapor shadowing and angular rotation on TBC coating thickness on a PW4000 turbine blade. Third, the model was run to populate a knowledge base for the rule-based software system. The system and its graphical user interface are designed to allow a coating engineer to select the EB-PVD process parameters that best fit the designer's requested TBC profile.

Weir, William Charles Stuart

2002-09-01

226

Nanoscale Architectures for Energy Applications  

NASA Astrophysics Data System (ADS)

In my group, we have developed a number of different potential architecture systems for gaining insights into energy storage and photovoltaics. In one manifestation of our efforts, generating a heterojunction comprising nanotubes and nanocrystals, externally bound and connected, has been significant. The unique, innovative, and important aspect of this particular nanoscale architecture is that it takes advantage of the tunability, in terms of size, shape, and chemistry, of nanotubes and nanocrystals, to create a sharp junction interface, whose properties are inherently manipulable, tailorable, and hence, predictable. For example, the electrical resistance of nanotube-nanoparticle networks is dependent on the nanoscale junctions that exist between these constituent nanomaterials as well as on microscale and macroscale connectivity. Thus, rational design of these nanomaterials is critical to a fundamental understanding of charge transport in single molecules and the determination of their conductance. Results on these systems can therefore be used to increase understanding of intrinsic factors affecting carrier mobility, such as electronic structure, carrier trapping, and delocalization. In a second manifestation, three-dimensional, dendritic micron- scale spheres of alkali metal hydrogen titanate 1D nanostructures (i.e.: nanowires and nanotubes) have been generated using a modified hydrothermal technique in the presence of hydrogen peroxide and an alkali metal hydroxide solution. Sea-urchin-like assemblies of these 1D nanostructures have been transformed into their hydrogen titanate analogues by neutralization as well as into their corresponding semiconducting, anatase titania nanostructured counterparts through a moderate high-temperature annealing dehydration process without destroying the 3D hierarchical structural motif. The as-prepared hollow spheres of titanate and titania 1D nanostructures have overall diameters, ranging from 0.8 ?m to 1.2 ?m, while the interior of these aggregates are vacuous with a diameter range of 100 to 200 nm. We have demonstrated that these assemblies are useful for example as active photocatalysts for the degradation of synthetic Procion Red dye under UV light illumination. In a third set of experiments, a size- and shape-dependent morphological transformation was demonstrated during the hydrothermal soft chemical transformation, in neutral solution, of titanate nanostructures into their anatase titania counterparts. Our results indicate that as-synthesized titania nanostructures possessed higher photocatalytic activity than the commercial titania precursors from whence they were derived.

Wong, Stanislaus

2009-03-01

227

Structural transitions in nanoscale systems  

NASA Astrophysics Data System (ADS)

In this work I investigate three different materials: nanoscale carbon systems, ferrofluid systems, and molecular-electronic devices. In particular, my study is focused on the theoretical understanding of structural changes and the associated electronic, mechanical, and magnetic properties of these materials. To study the equilibrium packing of fullerenes in carbon nanotube peapods optimization techniques were applied. In agreement with experimental measurements, my results for nanotubes containing fullerenes with 60--84 atoms indicate that the axial separation between the fullerenes is smaller than in the bulk crystal. The reduction of the inter-fullerene distance and also the structural relaxation of fullerenes result from a large internal pressure within the peapods. This naturally induced "static" pressure may qualify nanotubes as nanoscale autoclaves for chemical reactions. Combining total energy calculations with a search of phase space, I investigated the microscopic fusion mechanism of C60 fullerenes. I show that the (2+2) cycloaddition reaction, a necessary precursor for fullerene fusion, can be accelerated inside a nanotube. Fusion occurs along the minimum energy path as a finite sequence of Stone-Wales (SW) transformations. A detailed analysis of the transition states shows that Stone-Wales transformations are multi-step processes. I propose a new microscopic mechanism to explain the unusually fast fusion process of carbon nanotubes. The detailed pathway for two adjacent (5, 5) nanotubes to gradually merge into a (10, 10) tube, and the transition states have been identified. The propagation of the fused region is energetically favorable and proceeds in a morphology reminiscent of a Y-junction via a so called zipper mechanism, involving only SW bond rearrangements with low activation barriers. Using density functional theory, the equilibrium structure, stability, and electronic properties of nanostructured, hydrogen terminated diamond fragments have been studied. Such diamondoids can enter spontaneously into carbon nanotubes where polymerization of diamondoids is favourable. I studied the equilibrium structure of large but finite aggregates of magnetic dipoles, modeling a colloidal suspension of magnetite particles in a ferrofluid. With increasing system size, the structural motif evolves from chains and rings to multi-chain and multi-ring assemblies. These structural changes depend on external parameters and result from a competition between various energy terms, which can be described analytically within a continuum approximation. (Abstract shortened by UMI.)

Yoon, Mina

228

Quantitative nanoscale metrology study of Cu/SiO{sub 2} interconnect technology using transmission x-ray microscopy  

SciTech Connect

This letter describes quantitative nondestructive measurements of multilayer submicron Cu/SiO{sub 2} interconnect structures such as Cu lines, vias, and W lines with lateral dimensions down to 300 nm and electromigration defect structures using scanning transmission x-ray microscopy employing a 0.2 {mu}m x-ray beam. Typical measurement accuracies are {<=}60 nm for widths and lengths and {<=}10% in height. The high-resolution and nondestructive nature of this technique provide a very powerful probe of physical properties of nanoscale and submicron materials and structures.

Su, X.; Stagarescu, C.; Xu, G.; Eastman, D. E.; McNulty, I.; Frigo, S. P.; Wang, Yuxin; Retsch, Cornelia C.; Noyan, I. C.; Hu, C.-K.

2000-11-20

229

Imaging cells at the nanoscale.  

PubMed

Recently developed super-resolution techniques in optical microscopy have pushed the length scale at which cellular structure can be observed down to tens of nanometres. A wide array of methods have been described that fall under the umbrella term of super-resolution microscopy and each of these methods has different requirements for acquisition speed, experimental complexity, fluorophore requirements and post-processing of data. For example, experimental complexity can be decreased by using a standard widefield microscope for acquisition, but this requires substantial processing of the data to extract the super-resolution information. These powerful techniques are bringing new insights into the nanoscale structure of sub-cellular assemblies such as podosomes, which are an ideal system to observe with super-resolution microscopy as the structures are relatively thin and they form and dissociate over a period of several minutes. Here we discuss the major classes of super-resolution microscopy techniques, and demonstrate their relative performance by imaging podosomes. PMID:23688552

Cox, Susan; Jones, Gareth E

2013-05-18

230

Nanoscale imaging in DNA nanotechnology.  

PubMed

DNA nanotechnology has developed powerful techniques for the construction of precisely defined molecular structures and machines, and nanoscale imaging methods have always been crucial for their experimental characterization. While initially atomic force microscopy (AFM) was the most widely employed imaging method for DNA-based molecular structures, in recent years a variety of other techniques were adopted by researchers in the field, namely electron microscopy (EM), super-resolution fluorescence microscopy, and high-speed AFM. EM is now typically applied for the characterization of compact nanoobjects and three-dimensional (3D) origami structures, as it offers better resolution than AFM and can be used for 3D reconstruction from single-particle analysis. While the small size of DNA nanostructures had previously precluded the application of fluorescence microscopic methods, the development of super-resolution microscopy now facilities the application of fast and powerful optical methods also in DNA nanotechnology. In particular, the observation of dynamical processes associated with DNA nanoassemblies-e.g., molecular walkers and machines-requires imaging techniques that are both fast and allow observation under native conditions. Here single-molecule fluorescence techniques and high-speed AFM are beginning to play an increasingly important role. PMID:22114058

Jungmann, Ralf; Scheible, Max; Simmel, Friedrich C

2011-11-23

231

Proximity effects of superconducting multilayer film  

SciTech Connect

The proximity effects of superconducting multilayer films composed of different metals are considered. The relationship between the critical temperature of a superconducting multilayer film with strong heterogeneity and its geometric structure is given.

Xueyu, C.; Daole, Y.

1984-07-01

232

Electrical Transport in Metallic Magnetic Multilayers.  

National Technical Information Service (NTIS)

This thesis contains a theoretical study of electrical transport in metallic magnetic multilayers. The resistance of magnetic multilayers drops sharply when the magnetizations of adjacent magnetic layers are aligned by applying an external magnetic field....

C. M. Schep

1997-01-01

233

Deformation Mechanisms in Metallic Multilayers  

NASA Astrophysics Data System (ADS)

Metallic multilayered thin films often display enhanced mechanical behavior, relative to bulk materials, when the bilayer repeat length is reduced below about 10 nm. This behavior can be understood in a general way as resulting from the effects of the high density of interfaces characteristic of multilayers. The most common method of investigating the plastic deformation properties of multilayered thin films involves measuring the hardness using low-load indentation methods. A variety of microplasticity models have been presented to explain the dependence of the hardness on the bilayer repeat length. Several of these models assume that the film is an "ideal" multilayer involving single component layers and a rectangular wave composition profile. However, in many cases the multialyers deviate from this ideal structure. For example, in films such as Cu-Ni, where the layers display mutual solid solubility, the composition profile can be sinusoidal. In this case, the hardness will depend on the composition modulation amplitude as well as the modulation wavelength. Results from experimental and theoretical investigations of the deformation behavior of multilayered films will be critically reviewed. A discussion will be given concerning various possible interfacial hardening mechanisms and how these strengthening effects depend on the bilayer repeat length. The influence of microstructural features such as compositionally diffuse interfaces and phases owing to interfacial reactions will also be presented.

Cammarata, Robert

1998-03-01

234

Replication of a multilayer supermirror  

NASA Astrophysics Data System (ADS)

In the fabrication of the x-ray reflector using the replication method, Au was thought as the only material which can be used as the surface of reflector. However, if we could use the Pt or Ir, these has higher electron density than Au, as the surface, we can obtain higher reflectivity especially in the hard x-ray band. Furthermore, direct replication of the multilayer is very useful for the high reflectivity and mass-production process. We used the Au replica foil as the substrate of the multilayer. However, the epoxy layer of the replica foil was easily damaged by the heat during the deposition. This is a serious problem for the mass-production process, since we must take a long time to deposit the multilayer to keep the high reflectivity. We studied the direct replication of the multilayer, and successes to obtain the reflectivity as high as original one. Furthermore, we keep the trying to improve the quality of the reflector as flight quality. We will report the results and feature prospects of the replication of the multilayer and its application to the hard x-ray telescope.

Furuzawa, Akihiro; Yamashita, Koujun; Kunieda, Hideyo; Tawara, Yuzuru; Tamura, Keisuke; Haga, Kazutoshi; Nakamura, Norihiko; Nakajo, Norio; Takata, Harumi; Okajima, Takashi; Ogasaka, Yasushi; Lodha, Gyanendra S.; Namba, Yoshiharu

1998-11-01

235

PVD Cu trench-fill by viscous flow at high temperatures  

NASA Astrophysics Data System (ADS)

The scaling of integrated circuits has led to new challenges in Cu interconnect fabrication. It is getting difficult to fill narrow trenches, e.g. 20 nm wide, by Cu electroplating. In this work, a high temperature PVD Cu viscous flow trench fill process was explored to overcome the difficulties of filling narrow and high aspect ratio trenches. We have tested and found TaN and MoN to be good barriers, and Ru a good wetting surface for Cu. The three metals, Ta, Mo and Ru, are thus suitable for use as a thin liner to provide adhesion between the filled Cu and the dielectrics. We have therefore studied and compared Cu viscous flow trench filling on Ru, Mo and Ta liners. Cross-sectional TEM was employed to examine the trench fill profiles under different viscous flow conditions. We have found that a continuous Cu seed deposited at room temperature was essential to allow successful Cu viscous flow. The liner material's effect on Cu seed agglomeration was thus critical. It was shown that viscous flow on a Ru liner with a continuous Cu seed can fill narrow trenches (300 nm wide) at a high aspect ratio (a/r = 5), and produce maximized Cu grain size without post-fill annealing. A thicker Cu seed is required on the Mo liner for a successful viscous fill. However, on a Ta liner, because of poor Cu wetting, it is difficult to maintain a continuous Cu seed coverage at high temperatures, and the viscous fill was unsuccessful. To fill ultra-narrow (? 48 nm wide) and high aspect ratio (a/r ? 4) trenches, a lower deposition rate was needed. Agglomeration of the whole Cu fill at high temperatures is a key issue, which still remains to be overcome. Computer simulations of the viscous flow trench fill process were carried out, taking into account the effects of incoming flux divergence and Cu seed coverage. Our simulations indicated that a successful viscous trench fill relies on a continuous Cu seed coverage and a high surface mobility. Viscous flow is not sensitive to the incoming flux parameters. The use of Cu-alloy seeds is needed to alleviate electromigration in future interconnects. We have thus evaluated viscous fill of Cu on different Cu-alloy seeds (Cu-3 at.%Au, Cu-3 at.%Mn and Cu-3 at.%Al) in narrow trenches. The Cu-3 at.%Au alloy seed was found to facilitate a complete fill in 300 nm wide trenches with an aspect ratio of 3 on a Ta liner. For Cu-3 at.%Mn and Cu-3 at.%Al alloy seeds, solute segregation and oxidation were found to impede the viscous fill process. RBS measurements have confirmed extensive solute segregation in these two alloys at 400°C.

Wu, Zhiyuan

236

Sectioning of multilayers to make a multilayer Laue lens  

SciTech Connect

We report a process to fabricate multilayer Laue lenses (MLL's) by sectioning and thinning multilayer films. This method can produce a linear zone plate structure with a very large ratio of zone depth to width (e.g., >1000), orders of magnitude larger than can be attained with photolithography. Consequently, MLL's are advantageous for efficient nanofocusing of hard x rays. MLL structures prepared by the technique reported here have been tested at an x-ray energy of 19.5 keV, and a diffraction-limited performance was observed. The present article reports the fabrication techniques that were used to make the MLL's.

Kang, Hyon Chol; Stephenson, G. Brian; Liu Chian; Conley, Ray; Khachatryan, Ruben; Wieczorek, Michael; Macrander, Albert T.; Yan Hanfei; Maser, Joerg; Hiller, Jon; Koritala, Rachel [Center for Nanoscale Materials and Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); X-ray Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Center for Nanoscale Materials and X-ray Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States)

2007-04-15

237

Sectioning of multilayers to make a multilayer Laue lens  

NASA Astrophysics Data System (ADS)

We report a process to fabricate multilayer Laue lenses (MLL's) by sectioning and thinning multilayer films. This method can produce a linear zone plate structure with a very large ratio of zone depth to width (e.g., >1000), orders of magnitude larger than can be attained with photolithography. Consequently, MLL's are advantageous for efficient nanofocusing of hard x rays. MLL structures prepared by the technique reported here have been tested at an x-ray energy of 19.5 keV, and a diffraction-limited performance was observed. The present article reports the fabrication techniques that were used to make the MLL's.

Kang, Hyon Chol; Stephenson, G. Brian; Liu, Chian; Conley, Ray; Khachatryan, Ruben; Wieczorek, Michael; Macrander, Albert T.; Yan, Hanfei; Maser, Jörg; Hiller, Jon; Koritala, Rachel

2007-04-01

238

Localized modes in defective multilayer structures  

Microsoft Academic Search

In this paper, we investigate the localized surface modes in a defective multilayer structure. We show that the defective multilayer structure can support two different kinds of localized modes, depending on the position and the thickness of the defect layer. In one kind, the modes are localized at the interface between the multilayer structure and a homogeneous medium (the so-called

S. Roshan Entezar; A. Namdar

2009-01-01

239

Design method for multilayer interference filters  

Microsoft Academic Search

In this paper expressions for the transmittance and the reflectance of a system consisting of a spacer surrounded by two multilayer stacks are presented. These expressions provide a general approach for the design of multilayer coatings. High- and low-transmittance bands and a narrowband in the transmittance spectrum of multilayer stacks with unequal designed wavelengths are reported.

G. Castagno; F. Demichelis; E. Minetti-Mezzetti

1980-01-01

240

Digitally Encoded Exchange Biased Multilayers  

NASA Astrophysics Data System (ADS)

There is a high interest in magnetic multilayers for applications in biotechnology. Exchange biased systems are promising candidates for substituting magnetic beads in more complex applications that require each tag to carry digitally encoded information. We have studied the coercivity and exchange bias of Co/PdMn and CoFe/PdMn samples deposited by dc magnetron sputtering as a function of the materials thickness. We also have fabricated a multilayer comprised of four Co/PdMn bilayers that can be encoded in 16 different states, which are stable at zero applied field, thereby enabling the magnetic tag to store 4 bits of information.

Barbagallo, M.; van Belle, F.; Ionescu, A.; Bland, J. A. C.

2008-06-01

241

Nanoscale assemblies and their biomedical applications.  

PubMed

Nanoscale assemblies are a unique class of materials, which can be synthesized from inorganic, polymeric or biological building blocks. The multitude of applications of this class of materials ranges from solar and electrical to uses in food, cosmetics and medicine. In this review, we initially highlight characteristic features of polymeric nanoscale assemblies as well as those built from biological units (lipids, nucleic acids and proteins). We give special consideration to protein nanoassemblies found in nature such as ferritin protein cages, bacterial microcompartments and vaults found in eukaryotic cells and designed protein nanoassemblies, such as peptide nanofibres and peptide nanotubes. Next, we focus on biomedical applications of these nanoscale assemblies, such as cell targeting, drug delivery, bioimaging and vaccine development. In the vaccine development section, we report in more detail the use of virus-like particles and self-assembling polypeptide nanoparticles as new vaccine delivery platforms. PMID:23303217

Doll, Tais A P F; Raman, Senthilkumar; Dey, Raja; Burkhard, Peter

2013-01-09

242

Bridge-enhanced nanoscale impedance microscopy  

NASA Astrophysics Data System (ADS)

A conductive atomic force microscopy (cAFM) technique has been developed that is capable of quantitatively measuring the magnitude and phase of alternating current flow through the tip/sample junction with a five order of magnitude improvement in sensitivity. Bridge-enhanced nanoscale impedance microscopy (BE-NIM) uses a tunable resistor/capacitor bridge circuit to null the spurious contribution to the tip/sample current caused by fringe capacitance between the cAFM cantilever and the sample. As a proof of principle, BE-NIM is used to characterize an array of electron-beam lithographically patterned metal-oxide-semiconductor capacitors and compared directly to conventional nanoscale impedance microscopy. In addition, BE-NIM is applied to a multiwalled carbon nanotube/poly(m-phenylenevinylene-co-2,5-dioctyloxy-p-phenylenevinylene) nanocomposite material, on which the alternating current behavior of individual nanoscale conductive pathways is quantitatively probed.

Pingree, L. S. C.; Hersam, M. C.

2005-12-01

243

Quantum-enhanced performance of nanoscale thermoelectrics  

NASA Astrophysics Data System (ADS)

In a recent paper, we predicted that the linear thermoelectric response of a nanoscale junction is strongly enhanced by quantum interference in the vicinity of a transmission node.footnotetextJ. P. Bergfield and C. A. Stafford, Nano Letters 9, 3072 (2009). In this talk, we use our nonequilibrium many-body transport theoryfootnotetextJ. P. Bergfield and C. A.Stafford, Phys. Rev. B 79, 245125 (2009) to investigate the performance of thermoelectric devices based on single-molecule junctions, determining the thermodynamic efficiency and power at finite bias. By comparing the linear and nonlinear device characteristics, the applicability of the dimensionless thermoelectric figure-of-merit ZT to predict device performance at the nanoscale is tested. Finally, we report on a class of high-impedance nanoscale devices which possess additional quantum-enhancement, and exhibit high thermodynamic efficiency and ZT>10 limited only by the coherence length.

Bergfield, Justin; Stafford, Charles

2010-03-01

244

Image quality of figured multilayered optics  

SciTech Connect

The reflectivity and resolution of a multilayer structure is strongly affected by the roughness at the interfaces between two successive layers and by the amount that the constituent materials will diffuse into one another at the interfaces. Performance is also affected by the variations in individual layer thicknesses and by inhomogeneities in the materials. These deviations from the ideal multilayer will also affect the quality of the image from a figured multilayer optical element. The theory used to model the effects of non-ideal multilayers on the image quality of figured optics will be discussed. The relationship between image quality and multilayer structure quality will be illustrated with several examples.

Peterson, B.G.; Knight, L.V.; Pew, H.K.

1985-01-01

245

Biologically templated organic polymers with nanoscale order  

PubMed Central

Methods for the construction of ordered nanoscale arrays have been implicated in fields ranging from separation technologies to microelectronics. Yet, despite the plethora of nanoscale structures assembled in nature that use a templating strategy, chemists have been unable to replicate this success. A technology is reported for templated organic polymers composed of filamentous bacteriophage-polyacrylamide biomacromolecules that self-assemble into highly ordered helical bundles displaying hexagonal close packing. The results align with a previously reported mathematical prediction for the close packing of flexible tubes. This biopolymeric assembly can be viewed as a magnification of the inherent microscopic chirality and helicity present in individual phage particles at the macroscale level.

Willis, Bert; Eubanks, Lisa M.; Wood, Malcolm R.; Janda, Kim D.; Dickerson, Tobin J.; Lerner, Richard A.

2008-01-01

246

Field Induced Evolution of Nanoscale Structures in Relaxor PLZT Ceramics  

Microsoft Academic Search

The kinetics of the nanoscale structures under application of bipolar and unipolar ac field was investigated by recording of the switching charge in wide temperature and field range in hot-pressed relaxor PLZT ceramics. Original analysis of the switching charge data was based on the consideration of the field induced transformation as an evolution of the nanoscale domain structure with nanoscale

V. Y. A. SHUR; E. L. Rumyantsev; G. G. Lomakin; O. V. Yakutova; D. V. Pelegov; A. Sternberg; M. Kosec

2005-01-01

247

Carbon nanotube-based nanoscale ad hoc networks  

Microsoft Academic Search

Recent developments in nanoscale electronics allow current wireless technologies to function in nanoscale environments. Especially due to their incredible electrical and electromagnetic properties, carbon nanotubes are promising physical phenomenon that are used for the realization of a nanoscale communication paradigm. This provides a very large set of new promising applications such as collaborative disease detection with communicating in-vivo nanosensor nodes

Baris Atakan; Ozgur B. Akan

2010-01-01

248

Advantages of using PVD two-step titanium nitride barrier process and the impact of residual by-products from tungsten film deposition on process integration due to non-uniformity of the tungsten film  

Microsoft Academic Search

Device aspect ratios and dimensions at the contact and via levels for old and new technologies are driving PVD\\/WCVD-based metallization to its full limit at STMicroelectronics PF1 (Phoenix) site. Contact and via structures, while not posing the same rigorous dimensional problems or high aspect ratios, still suffer from problems associated with PVD sputtering of titanium (Ti) and titanium nitride (TiN)

2002-01-01

249

Polarization-dependent MAD holography: Nanoscale Magnetic Imaging of Nonperiodic Objects  

NASA Astrophysics Data System (ADS)

We present a novel approach to the nanoscale imaging of nonperiodic magnetic structures by introducing x-ray polarization dependence to the multiple wavelength anomalous diffraction (MAD) phasing technique. Essential phase information can be extracted from the differences between coherent scattering patterns recorded at different x-ray wavelengths (on- or off-resonance) and polarizations. Combined with an iterative phase retrieval algorithm, the magnetization distribution can be reconstructed. Using left and right circularly polarized x-rays near the Co L3 edge, we successfully imaged the perpendicular magnetic worm domains of a Co/Pd multilayer sample within a 3 micron circular aperture. The absence of reference apertures and a resolution that is, in principle, only limited by the wavelength render this method attractive for polarization-dependent and element-specific studies in magnetism, correlated materials and polymer research. This research is supported by the U.S. Department of Energy, Office of Basic Energy Science.

Wang, Tianhan; Zhu, Diling; Wu, Benny; Hellwig, Olav; Stohr, Joachim; Scherz, Andreas

2010-03-01

250

Porous silicon multilayer optical waveguides  

Microsoft Academic Search

Optical waveguiding is demonstrated in porous silicon multilayers. Depth variations in porosity, and therefore refractive index, are achieved by switching between high and low current densities during the anodic etch process. Planar waveguiding has been demonstrated at ? = 1.28 ?m. The wavelength range has been extended to the visible (? = 0.6328 ?m) by oxidising the samples to produce

A. Loni; L. T Canham; M. G Berger; R Arens-Fischer; H Munder; H Luth; H. F Arrand; T. M Benson

1996-01-01

251

Multilayer photoelectrodes and photovoltaic cells  

SciTech Connect

A corrosion-resistant, multilayer photoelectrode for use in a photoelectrochemical cell and a process for producing said photoelectrode by preparing an effective layer of an insulator material containing aliovalent dopant ions on a base semiconductor and depositing a layer of conducting material on said layer of insulating material.

Howe, A.T.

1985-01-08

252

Multilayer photoelectrodes utilizing exotic materials  

SciTech Connect

A corrosion-resistant, multilayer photoelectrode for use in a photoelectrochemical cell and a process for producing said photoelectrode by preparing an effective layer of an insulator material on a base semiconductor and depositing a layer of conducting material on said layer of insulating material.

Howe, A. T.

1985-06-04

253

Ultra-thin Multilayer Capacitors.  

National Technical Information Service (NTIS)

The fabrication of ultra-thin lanthanum-doped lead zirconium titanate (PLZT) multilayer ceramic capacitors (MLCCs) using a high-power pulsed ion beam was studied. The deposition experiments were conducted on the RHEPP-1 facility at Sandia National Laborat...

T. C. Monson T. J. Renk

2009-01-01

254

Multilayer printed wiring board lamination  

SciTech Connect

The relationship of delamination resistance of multilayer PWBs made from GF material to manufacturing process variables was investigated. A unique quantitative test method developed during this project shows that delamination resistance is highly sensitive to material conditioning, to innerlayer surface treatment, and to post-lamination storage conditions, but is relatively insensitive to cure cycle variations.

Lula, J.W.

1980-06-01

255

Multilayer insulation for spacecraft applications  

Microsoft Academic Search

Multilayer Insulation (MLI) blankets provide a lightweight insulation system with a high thermal resistance in vacuum. MLI blankets are utilized to reduce heat loss from a spacecraft to the cold space, or to prevent excessive heating of the surroundings from an internal component with heat dissipation. MLI blankets consist of a number of highly reflecting radiation shields interspaced with a

Che-Shing Kang

1999-01-01

256

Multilayer X-ray optics  

SciTech Connect

The principles, state of the art, and problems of multilayer X-ray optics are analysed. Among its applications, the projection X-ray lithography and mirrors for a repetitively pulsed capillary-discharge X-ray laser are considered. (special issue devoted to the 80th anniversary of academician n g basov's birth)

Vinogradov, Aleksandr V [P.N. Lebedev Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)

2002-12-31

257

Multilayer High-Gradient Insulators  

SciTech Connect

Multilayer High-Gradient Insulators are vacuum insulating structures composed of thin, alternating layers of dielectric and metal. They are currently being developed for application to high-current accelerators and related pulsed power systems. This paper describes some of the High-Gradient Insulator research currently being conducted at Lawrence Livermore National Laboratory.

Harris, J R

2006-08-16

258

Study of nano-scale diffusion in thin films and multilayers  

Microsoft Academic Search

It is shown that x-ray reflectivity and x-ray fluorescence under standing wave conditions can be used to study atomic diffusion\\u000a with an accuracy of a fraction of a nanometer. Both the techniques can be made isotope selective by making use of nuclear\\u000a resonance scattering from a Mössbauer active isotope. The techniques have been used to study self-diffusion of Fe in

Ajay Gupta; Sujoy Chakravarty; Parasmani Rajput; Mukul Gupta; Rudolf Rüffer

2008-01-01

259

Study of nano-scale diffusion in thin films and multilayers  

Microsoft Academic Search

It is shown that x-ray reflectivity and x-ray fluorescence under standing wave conditions can be used to study atomic diffusion\\u000a with an accuracy of a fraction of a nanometer. Both the techniques can be made isotope selective by making use of nuclear\\u000a resonance scattering from a Mössbauer active isotope. The techniques have been used to study self-diffusion of Fe in

Ajay Gupta; Sujoy Chakravarty; Parasmani Rajput; Mukul Gupta; Rudolf Rüffer

260

Multilayer polypeptide nanoscale coatings incorporating IL12 for the prevention of biomedical device-associated infections  

Microsoft Academic Search

Biomedical device-associated infection is one of the most common and problematic complications faced by millions of patients worldwide. The current antibiotic therapy strategies face challenges, the most serious of which is antibiotic resistance. Studies have shown that the systemic level of interleukin 12 (IL-12) decreases following major injuries resulting in decreased cell-mediated immune response. Here we report the development of

Bingyun Li; Bingbing Jiang; Brandon M. Boyce; Brock A. Lindsey

2009-01-01

261

Understanding nanoscale damage at a crack tip of multilayered metallic composites  

Microsoft Academic Search

Through quantitative focused ion beam cross-sectional characterization technique, we directly observed shear displacement in a range from several nanometers to a few tens of nanometers occurring in the plastic deformation zone ahead of a crack tip in nanolayered Cu\\/Ta composite subjected to tensile load. As a result, shear-mode fracture of the Cu\\/Ta laminate composite was eventually caused. A theoretical analysis

X. F. Zhu; Y. P. Li; G. P. Zhang; J. Tan; Y. Liu

2008-01-01

262

Understanding nanoscale damage at a crack tip of multilayered metallic composites  

NASA Astrophysics Data System (ADS)

Through quantitative focused ion beam cross-sectional characterization technique, we directly observed shear displacement in a range from several nanometers to a few tens of nanometers occurring in the plastic deformation zone ahead of a crack tip in nanolayered Cu/Ta composite subjected to tensile load. As a result, shear-mode fracture of the Cu/Ta laminate composite was eventually caused. A theoretical analysis of the interface barrier strength of nanolayered metallic composites here and reported in literature finds a critical individual layer thickness below which the nature of fracture of the nanolayered composites tends to be shearing failure.

Zhu, X. F.; Li, Y. P.; Zhang, G. P.; Tan, J.; Liu, Y.

2008-04-01

263

Passing stiffness anisotropy in multilayers and its effects on nanoscale surface self-organization  

Microsoft Academic Search

A binary monolayer adsorbed on a solid surface can separate into distinct phases that further self-assemble into various two-dimensional patterns. The surface stresses in the two phases are different, causing an elastic field in the substrate. The self-organization minimizes the combined free energy of mixing, phase boundary, and elasticity. One can obtain diverse patterns by using substrates with various crystalline

Y. F. Gao

2003-01-01

264

A benchtop method for the fabrication and patterning of nanoscale structures on polymers.  

PubMed

A benchtop method for the facile production of nanoscale metal structures on polymers is demonstrated. This approach allows for the design and patterning of a wide range of metallic structures on inexpensive polymer surfaces, affording the fabrication of nanoscaled platforms for use in the design of sensors, actuators, and disposable electronic and photonic devices. Numerous structures, from simple nanowires to multilayered metallic gratings, are demonstrated, with sizes ranging from microns to the nanoscale. The process involves molding a malleable metal film deposited on a rigid substrate such as mica, by the compression of a plastic polymer stamp with the desired pattern against the metal film. While under compression, an etchant is then used to modify the metal. Upon separation of the stamp from the support, micro- to nanoscaled metallic structures are found on the stamp and/or on the substrate. The sizes of the structures formed depend on the sizes of the features on the stamp but can be fine-tuned by about 4-fold through variations in both pressure and duration of etching. Also, depending on the processing, multiple dimension metallic structures can be obtained simultaneously in a single stamping procedure. The metallic structures formed on the stamp can also be subsequently transferred to another surface allowing for the construction of multilayered materials such as band gap gratings or the application of electrical contacts. Using this approach, fabrication of both simple and complex micro- to nanoscaled structures can be accomplished by most any researcher as even the grating structure of commercial compact disks may be used as stamps, eliminating the requirement of expensive lithographic processes to form simple structures. PMID:14719962

Helt, James M; Drain, Charles M; Batteas, James D

2004-01-21

265

Transport phenomena in nanoscale systems  

NASA Astrophysics Data System (ADS)

In this dissertation we discuss two general problems: transport of ballistic particles in systems with rough boundaries and the interference effect of bulk and boundary scattering processes. We derived a perturbative transport equation for ballistic particles in thin films with random rough walls for both quasiclassical and quantized motion across the film. The unusual non-diagonal structure of the effective scattering operator makes the transport equation different from the standard Waldmann-Snider equation when the distance between quantized levels for the motion across the film is comparable to the wall-induced perturbation. We calculate the magnitude of this anomaly for degenerate particles and Gaussian correlations of the surface inhomogeneities. Outside the quantum resonance domain we derived a simple, universal surface collision operator. This operator contains all relevant information on statistical and geometrical characteristics of weak roughness and can be used as a general boundary condition on the corrugated surfaces. We apply this operator to a variety of systems including films and channels with rough walls, particles adsorbed on or bound to rough substrates, multilayer systems with randomly corrugated interfaces, etc. The main emphasis is on quantization of motion between the walls, though the quasiclassical limit is considered as well. The diffusion and conductivity coefficients, localization length, and other transport parameters are expressed analytically via the correlation functions of surface corrugation. We analyze the interference processes between bulk and surface scattering. The effective collision time for scattering by random bulk and surface inhomogeneities, and the transport relaxation time are calculated beyond the Matthiessen's rule. The diagrammatic expansion includes second order diagrams for boundary scattering and full summation of bulk processes. The effective collision time is expressed via the bulk collision time and statistical parameters of the surface inhomogeneities. Calculation of the effective transport relaxation time requires the knowledge of the irreducible vertex function for the impurity scattering. In the case of a short-range impurity potential transport coefficients and transport relaxation time depend only on observable parameters: the bulk collision time, the bulk transport relaxation time, and parameters of the surface roughness.

Stepaniants, Armen Boris

266

High performance EUV multilayer optics  

NASA Astrophysics Data System (ADS)

The demand for enhanced optical resolution in order to structure and observe ever smaller details has pushed optics development in recent years. There is increasing interest in optical components for the extreme ultraviolet (EUV) spectral region mainly as a result of the production of more powerful electronic circuits with the aid of projection lithography. Due to absorption at wavelengths below 100 nm the penetration depth of EUV radiation into matter is only a few nano-meters. Hence, reflective optics must be used for imaging and light collection such as EUV multilayer mirrors which consist of alternating thin films with different refractive indices. This basic idea can be compared to the classic, high reflective ?/4 systems: the constructive interference of all beams reflected at the film interfaces. At Fraunhofer IOF Jena multilayer optics development cover the full range between the soft X-rays around 2 nm wave-length and the vacuum ultraviolet. However, the paper will focus on multilayer optics for EUV lithography applications at 13.5 nm. Besides the development of high-reflective multilayers with enhanced thermal and radiation stability using interface engineering and optimized capping layers collector and imaging optics for diverse applications in the EUV spectral range have been realized. The deposition of EUV collector mirrors for high-power laser produced plasma (LPP) sources is discussed. The paper summarizes recent progress and the present knowledge in preparation and characterization of multilayer optics for the EUV spectral range with regard to maximum optical performance, minimization of structure imperfections, reduc-tion of residual stresses as well as enhanced thermal and radiation stability.

Kaiser, Norbert; Yulin, Sergiy; Perske, Marco; Feigl, Torsten

2008-09-01

267

Embossing of nanoscale features and environments  

Microsoft Academic Search

A process has been developed whereby nanoscale features can be easily and uniformly transferred into a thermoplastic with the use of embossing. Masters for the embossing procedure are made using electron beam lithography, dry etching and electroplating and with these dies features as small as 60nm have been produced in the polymer cellulose acetate. In addition, it is shown that

B. G. Casey; W. Monaghan; C. D. W. Wilkinson

1997-01-01

268

Enhanced nanoscale friction on fluorinated graphene.  

PubMed

Atomically thin graphene is an ideal model system for studying nanoscale friction due to its intrinsic two-dimensional (2D) anisotropy. Furthermore, modulating its tribological properties could be an important milestone for graphene-based micro- and nanomechanical devices. Here, we report unexpectedly enhanced nanoscale friction on chemically modified graphene and a relevant theoretical analysis associated with flexural phonons. Ultrahigh vacuum friction force microscopy measurements show that nanoscale friction on the graphene surface increases by a factor of 6 after fluorination of the surface, while the adhesion force is slightly reduced. Density functional theory calculations show that the out-of-plane bending stiffness of graphene increases up to 4-fold after fluorination. Thus, the less compliant F-graphene exhibits more friction. This indicates that the mechanics of tip-to-graphene nanoscale friction would be characteristically different from that of conventional solid-on-solid contact and would be dominated by the out-of-plane bending stiffness of the chemically modified graphene. We propose that damping via flexural phonons could be a main source for frictional energy dissipation in 2D systems such as graphene. PMID:22720882

Kwon, Sangku; Ko, Jae-Hyeon; Jeon, Ki-Joon; Kim, Yong-Hyun; Park, Jeong Young

2012-06-25

269

Implementation of perception and action at nanoscale  

Microsoft Academic Search

Real time combination of nanosensors and nanoactuators with virtual reality environment and multisensorial interfaces enable us to efficiently act and perceive at nanoscale. Advanced manipulation of nanoobjects and new strategies for scientific education are the key motivations. We have no existing intuitive representation of the nanoworld ruled by laws foreign to our experience. A central challenge is then the construction

Sylvain Marlière; Jean-loup Florens; Florence Marchi; Annie Luciani; Joel Chevrier

2008-01-01

270

Benchtop Nanoscale Patterning Using Soft Lithography  

ERIC Educational Resources Information Center

|This paper outlines several benchtop nanoscale patterning experiments that can be incorporated into undergraduate laboratories or advanced high school chemistry curricula. The experiments, supplemented by an online video lab manual, are based on soft lithographic techniques such as replica molding, micro-molding in capillaries, and micro-contact…

Meenakshi, Viswanathan; Babayan, Yelizaveta; Odom, Teri W.

2007-01-01

271

Traceable nanoscale measurement at NML-SIRIM  

NASA Astrophysics Data System (ADS)

The role of national metrology institute (NMI) has always been very crucial in national technology development. One of the key activities of the NMI is to provide traceable measurement in all parameters under the International System of Units (SI). Dimensional measurement where size and shape are two important features investigated, is one of the important area covered by NMIs. To support the national technology development, particularly in manufacturing sectors and emerging technology such nanotechnology, the National Metrology Laboratory, SIRIM Berhad (NML-SIRIM), has embarked on a project to equip Malaysia with state-of-the-art nanoscale measurement facility with the aims of providing traceability of measurement at nanoscale. This paper will look into some of the results from current activities at NML-SIRIM related to measurement at nanoscale particularly on application of atomic force microscope (AFM) and laser based sensor in dimensional measurement. Step height standards of different sizes were measured using AFM and laser-based sensors. These probes are integrated into a long-range nanoscale measuring machine traceable to the international definition of the meter thus ensuring their traceability. Consistency of results obtained by these two methods will be discussed and presented. Factors affecting their measurements as well as their related uncertainty of measurements will also be presented.

Dahlan, Ahmad M.; Abdul Hapip, A. I.

2012-06-01

272

Synthesis, dynamics and photophysics of nanoscale systems  

Microsoft Academic Search

The emerging field of nanotechnology, which spans diverse areas such as nanoelectronics, medicine, chemical and pharmaceutical industries, biotechnology and computation, focuses on the development of devices whose improved performance is based on the utilization of self-assembled nanoscale components exhibiting unique properties owing to their miniaturized dimensions. The first phase in the conception of such multifunctional devices based on integrated technologies

Tihana Mirkovic

2009-01-01

273

Fats, Oils, & Colors of a Nanoscale Material  

ERIC Educational Resources Information Center

Phase changes and intermolecular forces are important physical science concepts but are not always easy to present in an active learning format. This article presents several interactive activities in which students plot the melting points of some fatty acids and explore the effect that the nanoscale size and shape of molecules have on the…

Lisensky, George C.; Horoszewski, Dana; Gentry, Kenneth L.; Zenner, Greta M.; Crone, Wendy C .

2006-01-01

274

Traceable nanoscale measurement at NML-SIRIM  

SciTech Connect

The role of national metrology institute (NMI) has always been very crucial in national technology development. One of the key activities of the NMI is to provide traceable measurement in all parameters under the International System of Units (SI). Dimensional measurement where size and shape are two important features investigated, is one of the important area covered by NMIs. To support the national technology development, particularly in manufacturing sectors and emerging technology such nanotechnology, the National Metrology Laboratory, SIRIM Berhad (NML-SIRIM), has embarked on a project to equip Malaysia with state-of-the-art nanoscale measurement facility with the aims of providing traceability of measurement at nanoscale. This paper will look into some of the results from current activities at NML-SIRIM related to measurement at nanoscale particularly on application of atomic force microscope (AFM) and laser based sensor in dimensional measurement. Step height standards of different sizes were measured using AFM and laser-based sensors. These probes are integrated into a long-range nanoscale measuring machine traceable to the international definition of the meter thus ensuring their traceability. Consistency of results obtained by these two methods will be discussed and presented. Factors affecting their measurements as well as their related uncertainty of measurements will also be presented.

Dahlan, Ahmad M.; Abdul Hapip, A. I. [National Metrology Laboratory SIRIM Berhad (NML-SIRIM), Lot PT 4803, Bandar Baru Salak Tinggi, 43900 Sepang (Malaysia)

2012-06-29

275

Scanning tunnelling microscopy of novel nanoscale materials  

Microsoft Academic Search

This dissertation is divided into three main parts. The first section describes an low temperature, ultra high vacuum (UHV) scanning tunnelling microscope (STM) system designed and built mainly by Phil Collins, a former Zettl group student, and Masa Ishigami. The system was designed specifically for investigating electronic properties of nanoscale materials. The second section discusses scanning tunnelling microscopy experiments on

Masahiro Ishigami

2004-01-01

276

Fats, Oils, & Colors of a Nanoscale Material  

ERIC Educational Resources Information Center

|Phase changes and intermolecular forces are important physical science concepts but are not always easy to present in an active learning format. This article presents several interactive activities in which students plot the melting points of some fatty acids and explore the effect that the nanoscale size and shape of molecules have on the…

Lisensky, George C.; Horoszewski, Dana; Gentry, Kenneth L.; Zenner, Greta M.; Crone, Wendy C .

2006-01-01

277

Microscale abrasive wear testing of duplex and non-duplex (single-layered) PVD (Ti,Al)N, TiN and Cr–N coatings  

Microsoft Academic Search

A micro-scale abrasive wear test, based on ball-cratering, has been used to evaluate the wear resistance of duplex and non-duplex (Ti,Al)N, TiN and Cr–N coatings. The term duplex is used here when plasma nitriding is followed by PVD coating. Coatings without the plasma nitriding stage are termed single-layered. Coating properties were evaluated by surface profilometry, hardness and scratch testing. All

J. C. A Batista; C. Godoy; A. Matthews

2002-01-01

278

Corrosion and erosion performance of HVOF\\/TiAlN PVD coatings and candidate materials for high pressure gate valve application  

Microsoft Academic Search

The main objective of this paper is to study the slurry erosion and corrosion behavior of WC10Co4Cr, Armcore ‘M’ Stellite 6 and 12 HVOF coatings, TiAlN PVD coating, selected steels, such as X20Cr13, 17Cr–4Ni pH steel and Ti6Al4V titanium alloy alongwith conventional hard weld deposits of Stellite 6 and 21. The slurry erosion studies were carried out at 60° angle

B. S. Mann; Vivek Arya; A. K. Maiti; M. U. B. Rao; Pankaj Joshi

2006-01-01

279

SUBSIDIZED INTEREST RATES AND RESTRICTED AGRICULTURAL CREDIT IN LDCs \\/ LES TAUX D'INTERET SUBVENTIONNES ET LA RESTRICTION DU CREDIT AGRICOLE DANS LES PVD  

Microsoft Academic Search

Le rôle du secteur agricole dans l'economie des PVD est aujourd'hui un fait acquis et de ce fait les gouvernements de ces pays ont tous entamé des programmes de devéloppement agricole. Parmi ces programmes il y a aussi des programmes de crédit agricole public à l'agriculture de subsistance visant à éliminer les contraintes les plus graves qui empèchent le devéloppement

François Kamajou

1980-01-01

280

High temperature wear resistance of (TiAl)N PVD coating on untreated and gas nitrided AISI H13 steel with different heat treatments  

Microsoft Academic Search

The wear resistance of a PVD (Ti0.7Al0.3)N coating deposited on an as-received and gas nitrided AISI H13 has been examined by using ball-on-disc tests at room temperature and at 600°C. In order to determine the influence of a previous heat treatment on this type of steel on the wear resistance of the (Ti0.7Al0.3)N coating, two commercial heat treatments were employed

R. Rodríguez-Baracaldo; J. A. Benito; E. S. Puchi-Cabrera; M. H. Staia

2007-01-01

281

Designing a Multicellular Organotypic 3D Liver Model with a Detachable, Nanoscale Polymeric Space of Disse.  

PubMed

The design of in vitro models that mimic the stratified multicellular hepatic microenvironment continues to be challenging. Although several in vitro hepatic cultures have been shown to exhibit liver functions, their physiological relevance is limited due to significant deviation from in vivo cellular composition. We report the assembly of a novel three-dimensional (3D) organotypic liver model incorporating three different cell types (hepatocytes, liver sinusoidal endothelial cells, and Kupffer cells) and a polymeric interface that mimics the Space of Disse. The nanoscale interface is detachable, optically transparent, derived from self-assembled polyelectrolyte multilayers, and exhibits a Young's modulus similar to in vivo values for liver tissue. Only the 3D liver models simultaneously maintain hepatic phenotype and elicit proliferation, while achieving cellular ratios found in vivo. The nanoscale detachable polymeric interfaces can be modulated to mimic basement membranes that exhibit a wide range of physical properties. This facile approach offers a versatile new avenue in the assembly of engineered tissues. These results demonstrate the ability of the tri-cellular 3D cultures to serve as an organotypic hepatic model that elicits proliferation and maintenance of phenotype and in vivo-like cellular ratios. PMID:23556413

Larkin, Adam L; Rodrigues, Richard R; Murali, T M; Rajagopalan, Padmavathy

2013-06-22

282

Multilayer X-ray optics at CHESS.  

PubMed

Almost half of the X-ray beamlines at the Cornell High Energy Synchrotron Source (CHESS) are based on multilayer optics. ;Traditional' multilayers with an energy resolution of DeltaE/E approximately 2% are routinely used to deliver X-ray flux enhanced by a factor of 10(2) in comparison with standard Si(111) optics. Sagittal-focusing multilayers with fixed radius provide an additional factor of 10 gain in flux density. High-resolution multilayer optics with DeltaE/E approximately 0.2% are now routinely used by MacCHESS crystallographers. New wide-bandpass multilayers with DeltaE/E = 5% and 10% have been designed and tested for potential applications in macromolecular crystallography. Small d-spacing multilayers with d < or = 20 A have been successfully used to extend the energy range of multilayer optics. Analysis of the main characteristics of the Mo/B4C and W/B4C small d-spacing multilayer optics shows enhancement in their performance at higher energies. Chemical vapour deposited SiC, with a bulk thermal conductivity of a factor of two higher than that of silicon, has been successfully introduced as a substrate material for multilayer optics. Characteristics of different types of multilayer optics at CHESS beamlines and their applications in a variety of scattering, diffraction and imaging techniques are discussed. PMID:16495620

Kazimirov, Alexander; Smilgies, Detlef M; Shen, Qun; Xiao, Xianghui; Hao, Quan; Fontes, Ernest; Bilderback, Donald H; Gruner, Sol M; Platonov, Yuriy; Martynov, Vladimir V

2006-02-17

283

[Standardized testing of bone implant surfaces with an osteoblast cell culture cyste. III. PVD hard coatings and Ti6Al4V].  

PubMed

The effect of titanium-based PVD coatings and a titanium alloy on the proliferation and differentiation of osteoblasts was investigated using a standardised cell culture system. Human fetal osteoblasts (hFOB 1.19) were cultured on titanium-niobium-nitride ([Ti,Nb]N), titanium-niobium-oxy-nitride coatings ([Ti,Nb]ON) and titanium-aluminium-vanadium alloy (Ti6Al4V) for 17 days. Cell culture polystyrene (PS) was used as reference. For the assessment of proliferation, the numbers and viability of the cells were determined, while alkaline phosphatase activity, collagen I and osteocalcin synthesis served as differentiation parameters. On the basis of the cell culture experiments, a cytotoxic effect of the materials can be excluded. In comparison with the other test surfaces, [Ti,Nb]N showed greater cell proliferation. The [Ti,Nb]N coating was associated with the highest level of osteocalcin production, while all other differentiation parameters were identical on all three surfaces. The test system described reveals the influence of PVD coatings on the osteoblast differentiation cycle. The higher oxygen content of the [Ti,Nb]ON surface does not appear to have any positive impact on cell proliferation. The excellent biocompatibility of the PVD coatings is confirmed by in vivo findings. The possible use of these materials in the fields of osteosynthesis and articular surfaces is still under discussion. PMID:11194641

Steinert, A; Hendrich, C; Merklein, F; Rader, C P; Schütze, N; Thull, R; Eulert, J

2000-12-01

284

Thermal conduction in graphene and graphene multilayers  

NASA Astrophysics Data System (ADS)

There has been increasing interest in thermal conductivity of materials motivated by the heat removal issues in electronics and by the need of fundamental science to understand heat conduction at nanoscale [1, 2, 3]. This dissertation reports the results of the experimental investigation of heat conduction in graphene and graphene multilayers. Graphene is a planar single sheet of sp2-bonded carbon atoms arranged in honeycomb lattice. It reveals many unique properties, including the extraordinarily high carrier mobility. In order to measure the thermal conductivity of graphene we developed an original non-contact technique based on micro-Raman spectroscopy. The samples for this study were prepared by mechanical exfoliation and suspended across trenches in Si/SiO2 substrates. The number of atomic planes was determined by deconvolution of the Raman 2D band. The suspended graphene flakes attached to the heat sinks were heated by the laser light focused in the middle. The Raman G peak's temperature sensitivity allowed us to monitor the local temperature change produced by the variation of the excitation laser power. A special calibration procedure was developed to determine the fraction of power absorbed by graphene. Our measurements revealed that single-layer graphene has an extremely high room-temperature thermal conductivity in the range 3800-5300 W/mK depending on the flake size and quality. It was also found that most of the heat near room temperature is transferred by acoustic phonons rather than electrons. Theoretical studies of the phonon thermal conduction in graphene, which included detail treatment of the Umklapp scattering, are in agreement with our experiments. The measurements were also extended to few-layer graphene. It was shown that the thermal conductivity reduces with the increasing number of layers approaching the bulk graphite limit. To validate the measurement technique we investigated the thermal conductivity of the polycrystalline graphene films and reduced graphene oxide films deposited on polyethylene terephthalate substrates. In this case we obtained much smaller values of thermal conductivity, which was explained by the strong acoustic phonon scattering on the grain boundaries. Obtained results are important for electronic applications of graphene and may lead to new methods of thermal management of nanoelectronic chips.

Ghosh, Suchismita

285

Interactions between glide dislocations and parallel interfacial dislocations in nanoscale strained layers  

SciTech Connect

Plastic deformation in nanoscale multilayered structures is thought to proceed by the successive propagation of single dislocation loops at the interfaces. Based on this view, we simulate the effect of predeposited interfacial dislocation on the stress (channeling stress) needed to propagate a new loop parallel to existing loops. Single interfacial dislocations as well as finite parallel arrays are considered in the computation. When the gliding dislocation and the predeposited interfacial array have collinear Burgers vectors, the channeling stress increases monotonically as the density of dislocations in the array increases. In the case when their Burgers vectors are inclined at 60 deg. , a regime of perfect plasticity is observed which can be traced back to an instability in the flow stress arising from the interaction between the glide dislocation and a single interfacial dislocation dipole. This interaction leads to a tendency for dislocations of alternating Burgers vectors to propagate during deformation leading to nonuniform arrays. Inclusion of these parallel interactions in the analysis improves the strength predictions as compared with the measured strength of a Cu-Ni multilayered system in the regime where isolated glide dislocation motion controls flow, but does not help to explain the observed strength saturation when the individual layer thickness is in the few nanometer range.

Akasheh, F.; Zbib, H. M.; Hirth, J. P.; Hoagland, R. G.; Misra, A. [School of Mechanical and Materials Engineering, Washington State University, Pullman, Washington 99164-2920 (United States); MST Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2007-08-01

286

Low thermal conductivity in nanoscale layered materials synthesized by the method of modulated elemental reactants  

NASA Astrophysics Data System (ADS)

We report the room-temperature, cross-plane thermal conductivities, and longitudinal speeds of sound of multilayer films [(TiTe2)3(Bi2Te3)x(TiTe2)3(Sb2Te3)y]i (x=1-5, y=1-5) and misfit-layer dichalcogenide films [(PbSe)m(TSe2)n]i (T=W or Mo, m=1-5, and n=1-5) synthesized by the modulated elemental reactants method. The thermal conductivities of these nanoscale layered materials fall below the predicted minimum thermal conductivity of the component compounds: two times lower than the minimum thermal conductivity of Bi2Te3 for multilayer [(TiTe2)3(Bi2Te3)x(TiTe2)3(Sb2Te3)y]i films and five to six times lower than the minimum thermal conductivity of PbSe for misfit-layer dichalcogenides [(PbSe)m(TSe2)n]i. We attribute the low thermal conductivities to the anisotropic bonding of the layered crystals and orientational disorder in the stacking of layered crystals along the direction perpendicular to the surface.

Chiritescu, Catalin; Cahill, David G.; Heideman, Colby; Lin, Qiyin; Mortensen, Clay; Nguyen, Ngoc T.; Johnson, David; Rostek, Raimar; Böttner, Harald

2008-08-01

287

High performance multilayered nano-crystalline silicon/silicon-oxide light-emitting diodes on glass substrates  

NASA Astrophysics Data System (ADS)

A low-temperature hydrogenation-assisted sequential deposition and crystallization technique is reported for the preparation of nano-scale silicon quantum dots suitable for light-emitting applications. Radio-frequency plasma-enhanced deposition was used to realize multiple layers of nano-crystalline silicon while reactive ion etching was employed to create nano-scale features. The physical characteristics of the films prepared using different plasma conditions were investigated using scanning electron microscopy, transmission electron microscopy, room temperature photoluminescence and infrared spectroscopy. The formation of multilayered structures improved the photon-emission properties as observed by photoluminescence and a thin layer of silicon oxy-nitride was then used for electrical isolation between adjacent silicon layers. The preparation of light-emitting diodes directly on glass substrates has been demonstrated and the electroluminescence spectrum has been measured.

Darbari, S.; Shahmohammadi, M.; Mortazavi, M.; Mohajerzadeh, S.; Abdi, Y.; Robertson, M.; Morrison, T.

2011-09-01

288

Wideband filters employing multilayer gratings  

Microsoft Academic Search

Multilayer surfaces, consisting of stacked inductive and capacitive strips or grids, have been used to design wideband filters in the 5-40 GHz range, with rapid transitions between reflection and transmission. For singly polarized applications, transmission bandwidths of 70-100 percent and edge transition ratios of 1.1-1.3 are realizable at 45 TM incidence using 4-8 layers of capacitive and inductive strips. Factors

P. W. B. Au; E. A. Parker; R. J. Langley

1993-01-01

289

Fe/Au Multilayers: Structure and Magnetoresistance  

SciTech Connect

We have measured the magnetoresistance (MR) in two sets of Fe/Au multilayers, with varying (1) Fe layer thickness, t{sub Fe} = 3-10 nm, and (2) Au layer thickness t{sub Au} = 5-15 nm, grown on Si substrates by sputtering. The multilayer interface structure and magnetic properties were studied by polarized neutron reflectometry (PNR). The study was undertaken to understand the correlation between structure of these multilayers and their magneto-transport properties.

Singh, Surendra; Basu, Saibal; Bhattacharya, D. [Solid State Physics Division, Bhabha Atomic Research Center, Mumbai 400085 (India); Prajapat, C. L. [Technical Physics Division, Bhabha Atomic Research Center, Mumbai 400085 (India); Gupta, M. [UGC-DAE Consortium for Scientific Research, University Campus, Khandwa Road, Indore 452 017 (India)

2011-07-15

290

Multilayer piezoelectric devices based on PZT  

Microsoft Academic Search

A PZT 53\\/47 was obtained by a modified chemical route. Small-particle-size powders were allowed to obtain high solid content, non-aqueous slips with Newtonian behaviour. The use of both the tape-casting technique and the common multilayer ceramic fabrication process led to a high-density multilayer ceramic body without cracks or delaminations, and a homogeneous microstructure. The architecture of multilayer piezoelectrics has an

E. Nieto; J. F. Fernandez; C. Moure; P. Duran

1996-01-01

291

Molybdenum-ruthenium\\/beryllium multilayer coatings  

Microsoft Academic Search

A newly developed beryllium-based multilayer system consisting of polycrystalline Be and amorphous MoRu layers is presented. The multilayer exhibits many remarkable properties: reflectivity as high as 69.3% at a wavelength of 11.4 nm (achieved with 50 bilayers giving a bandwidth of 0.35 nm), near-zero intrinsic stress, and excellent smoothing properties. As compared with Mo\\/Si multilayers at 13.4 nm, the shorter

Sasa. Bajt; Sasa

2000-01-01

292

Multilayered Transducers Using Polyurea Film  

NASA Astrophysics Data System (ADS)

We have been investigating ultrasonic transducers using a polyurea piezoelectric material, which is fabricated by vapor deposition. To enhance the transducer performance, a multilayered configuration is studied in this work. First, the fabrication and transducer design of the multilayered structure are described. A special twin-vacuum chamber is used for laminating the polyurea layers and aluminum electrodes alternately without breaking vacuum. We fabricate two- and four-layered transducers with 1.5 ?m polyurea films. The calculation results show that the force factor and electromechanical coupling coefficient increase as the number of layers increases. Second, to evaluate the transducer performance, we measure the electromechanical coupling factors and electric admittances. The coupling coefficients also increase as the number of layers increases at the resonant frequencies of about 30, 65, and 100 MHz. The pulse/echo measurements are conducted to determine the transmission and receiving characteristics using a reflector. The results of the experiment show that the voltage amplitudes of the received signal increase because of multilayer lamination.

Nakazawa, Marie; Tabaru, Masaya; Nakamura, Kentaro; Ueha, Sadayuki; Maezawa, Akihiro

2007-07-01

293

Ultra-thin multilayer capacitors.  

SciTech Connect

The fabrication of ultra-thin lanthanum-doped lead zirconium titanate (PLZT) multilayer ceramic capacitors (MLCCs) using a high-power pulsed ion beam was studied. The deposition experiments were conducted on the RHEPP-1 facility at Sandia National Laboratories. The goal of this work was to increase the energy density of ceramic capacitors through the formation of a multilayer device with excellent materials properties, dielectric constant, and standoff voltage. For successful device construction, there are a number of challenging requirements including achieving correct stoichiometric and crystallographic composition of the deposited PLZT, as well as the creation of a defect free homogenous film. This report details some success in satisfying these requirements, although 900 C temperatures were necessary for PLZT perovskite phase formation. These temperatures were applied to a previously deposited multi-layer film which was then post-annealed to this temperature. The film exhibited mechanical distress attributable to differences in the coefficient of thermal expansion (CTE) of the various layers. This caused significant defects in the deposited films that led to shorts across devices. A follow-on single layer deposition without post-anneal produced smooth layers with good interface behavior, but without the perovskite phase formation. These issues will need to be addressed in order for ion beam deposited MLCCs to become a viable technology. It is possible that future in-situ heating during deposition may address both the CTE issue, and result in lowered processing temperatures, which in turn could raise the probability of successful MLCC formation.

Renk, Timothy Jerome; Monson, Todd C.

2009-06-01

294

Experimental performances of implanted lamellar X-ray multilayer grating. Comparison with conventional etched multilayer grating  

Microsoft Academic Search

An original way is given to perform X-ray diffractive optics based on local intermixing with energetic ions. The valleys of the conventional X-ray multilayer grating are replaced by mixed multilayer parts with low reflectivity. This new structure obtained by ion implantation instead of etching is called implanted multilayer grating. In this paper we report on diffraction measurements of implanted and

H. Trambly; B. Vidal; L. Roux

1998-01-01

295

Molecular Modeling of Dendrimers for Nanoscale Applications  

SciTech Connect

Dendrimers are well defined, highly branched macromolecules that radiate from a central core and are synthesized through a stepwise, repetitive reaction sequence that guarantees complete shells for each generation, leading to polymers that are monodisperse. The synthetic procedures developed for dendrimer preparation permit nearly complete control over the critical molecular design parameters, such as size, shape, surface/interior chemistry, flexibility, and topology. Recent results suggest that dendritic polymers may provide the key to developing a reliable and economical fabrication and manufacturing route to functional nanoscale materials that would have unique properties (electronic, optical, opto-electronic, magnetic, chemical, or biological). In turn, these could be used in designing new nanoscale devices. In this paper, we determine the 3D molecular structure of various dendrimers with continuous configurational Boltzmann biased direct Monte Carlo method and study their energetic and structural properties using molecular dynamics after annealing these molecular representations.

Cagin, Tahir; Wang, Guofeng; Martin, Ryan; Breen, Nicholas; Goddard, William

2000-06-01

296

Programmed assembly of nanoscale structures using peptoids.  

SciTech Connect

Sequence-specific polymers are the basis of the most promising approaches to bottom-up programmed assembly of nanoscale materials. Examples include artificial peptides and nucleic acids. Another class is oligo(N-functional glycine)s, also known as peptoids, which permit greater sidegroup diversity and conformational control, and can be easier to synthesize and purify. We have developed a set of peptoids that can be used to make inorganic nanoparticles more compatible with biological sequence-specific polymers so that they can be incorporated into nucleic acid or other biologically based nanostructures. Peptoids offer degrees of modularity, versatility, and predictability that equal or exceed other sequence-specific polymers, allowing for rational design of oligomers for a specific purpose. This degree of control will be essential to the development of arbitrarily designed nanoscale structures.

Ren, Jianhua (University of the Pacific, Stockton, CA); Russell, Scott (California State University, Stanislaus, Turlock, CA); Morishetti, Kiran (University of the Pacific, Stockton, CA); Robinson, David B.; Zuckermann, Ronald N. (Lawrence Berkeley National Laboratory, Berkeley, CA); Buffleben, George M.; Hjelm, Rex P. (Los Alamos National Laboratory, Los Alamos, NM); Kent, Michael Stuart (Sandia National Laboratories, Albuquerque, NM)

2011-02-01

297

TryEngineering: Exploring at the Nanoscale  

NSDL National Science Digital Library

This is a lesson plan that explores how nanotechnology has impacted the world. It was developed to help students visualize just how tiny a nanometer is and how scientists work to apply principles of nanotechnology. In hands-on activities, students evaluate and compare the surface areas at the macroscopic and nanoscale level. Links are provided to images of nanoscale objects produced by scanning electron microscopy (SEM). In the culminating activity, learners prepare a mock proposal for funding a nanotechnology application of their choosing. The lesson includes objectives and learner outcomes, problem sets, student guides, recommended reading, illustrated procedures, worksheets, and background information about the engineering connections. This collection is part of TryEngineering.org, a website maintained by the Institute of Electrical and Electronics Engineers (IEEE).

298

Microscopic current dynamics in nanoscale junctions  

NASA Astrophysics Data System (ADS)

So far, transport properties of nanoscale contacts have been studied mostly within the static scattering approach. The electron dynamics and the transient behavior of current flow, however, remain poorly understood. We present a numerical study of microscopic current flow dynamics in nanoscale quantum point contacts. We employ an approach that combines a microcanonical picture of transport with time-dependent density-functional theory. We carry out atomic and jellium model calculations to show that the time evolution of the current flow exhibits several noteworthy features, such as nonlaminarity and edge flow. We attribute these features to the interaction of the electron fluid with the ionic lattice, to the existence of pressure gradients in the fluid, and to the transient dynamical formation of surface charges at the nanocontact-electrode interfaces. Our results suggest that quantum transport systems exhibit hydrodynamical characteristics, which resemble those of a classical liquid.

Sai, Na; Bushong, Neil; Hatcher, Ryan; di Ventra, Massimiliano

2007-03-01

299

Basic research interests in nanoscale radiation sensing  

NASA Astrophysics Data System (ADS)

Identification of the presence of radioactive materials is important for both defense and environmental concerns. Nanoscience may enable improved understanding of energy storage or transfer processes that can be exploited for indicators. For example, nanoscale materials that emit spectral signatures in the presence of ionizing radiation or nuclear particles, when incorporated in other widely used materials or objects, would assist in locating and securing radiological or nuclear materials.

Shipbaugh, Calvin

2012-05-01

300

The weird world of the nanoscale  

Microsoft Academic Search

Objects or structures which have at least one important dimension in the range 0.5 to perhaps 20 nm may be considered to be in the nano-scale domain. These sizes lie far below the 800 nm or so that can be resolved with an optical microscope, and are closer in size to the 0.3 nm diameter of individual atoms. Nanotechnology, which

Mike Cortie

2007-01-01

301

Preface: Charge transport in nanoscale junctions  

Microsoft Academic Search

Understanding the fundamentals of nanoscale charge transfer is pivotal for designing future nano-electronic devices. Such devices could be based on individual or groups of molecular bridges, nanotubes, nanoparticles, biomolecules and other 'active' components, mimicking wire, diode and transistor functions. These have operated in various environments including vacuum, air and condensed matter, in two- or three-electrode configurations, at ultra-low and room

Tim Albrecht; Alexei Kornyshev; Thomas Bjørnholm

2008-01-01

302

Design of a nanoscale silicon laser  

Microsoft Academic Search

The recent observation of optical gain from silicon nanocrystals embedded in SiO2 opens an opportunity to develop a nanoscale silicon-based laser. However, the challenge remains to design and develop a laser architecture using CMOS-compatible materials. In this paper we present two designs for a waveguide laser in which silicon nanocrystals embedded in SiO2 are used as the optical gain media.

S. L. Jaiswal; J. T. Simpson; S. P. Withrow; C. W. White; P. M. Norris

2003-01-01

303

Design of a nanoscale silicon laser  

Microsoft Academic Search

.   The recent observation of optical gain from silicon nanocrystals embedded in SiO2 opens an opportunity to develop a nanoscale silicon-based laser. However, the challenge remains to design and develop a laser\\u000a architecture using CMOS-compatible materials. In this paper we present two designs for a waveguide laser in which silicon\\u000a nanocrystals embedded in SiO2 are used as the optical gain

S. L. Jaiswal; J. T. Simpson; S. P. Withrow; C. W. White; P. M. Norris

2003-01-01

304

Nanoscale Solute Partitioning in Bulk Metallic Glasses  

SciTech Connect

Devitrification of bulk metallic glass leads to a novel microstructure, with high-density nanoscale crystalline precipitates evenly distributed in a glassy matrix. Significant chemical segregation is revealed at unprecedented detail by atom-probe tomography. This level of detail is crucial for understanding the interference peaks observed in small-angle X-ray and neutron scattering experiments, an unsolved mistery for over a decade.

Yang, Ling [ORNL; Miller, Michael K [ORNL; Liu, Chain T [ORNL; Stoica, Alexandru Dan [ORNL; Shi, Donglu [University of Cincinnati

2009-01-01

305

Self-healing at the nanoscale  

Microsoft Academic Search

The design of self-healing materials is a very important but challenging topic in nanotechnology. Self-healing strategies, also inspired by natural processes, allow the fabrication of auto-repairing systems, and in recent years, materials engineering at the nanoscale has allowed further advances in this emerging field. In this mini review, we recall some interesting self-healing systems found in natural processes and others

Vincenzo Amendola; Moreno Meneghetti

2009-01-01

306

Nanoacoustics: probing acoustic waves on the nanoscale  

Microsoft Academic Search

Two scanning acoustic probe microscopy (SAPM) techniques have been developed for the nanoscale analysis of the interaction of acoustic modes on the surface of a solid. The scanning acoustic force microscope (SAFM) and the scanning acoustic tunneling microscope (SATM) are extensions to the scanning probe microscopy world utilizing the non-linearity of the respective interaction-distance curves in order to detect high-frequency

Thorsten Hesjedal

2003-01-01

307

Nanoscale oxidation of silicon microring resonators  

Microsoft Academic Search

* Email: smookherjea@ucsd.edu Abstract: The resonance frequency of a silicon microring was permanently blue-shifted with 1.2 GHz resolution over more than 350 GHz, a full free-spectral-range, by electrochemically changing the waveguide core (silicon) to the cladding (silicon dioxide) material. ?2011 Optical Society of America Silicon microring devices are sensitively affected by nanoscale disorder, e.g., few nanometer variations in the width

Yiran Shen; Shayan Mookherjea

2011-01-01

308

Center for Nanoscale Science and Technology  

NSDL National Science Digital Library

The Center for Nanoscale Science and Technology consists of a Research Program and the Nanofab, a shared-use facility providing economical access to state-of-the-art nanofabrication and nano-measurement tools. The CNST Nanofab is now available for use by non-NIST users. See "What we do", to the left, for a description of CNST and its Research Program as well as the CNST Nanofab and its use policies.

2010-05-18

309

Nanoscale Materials Modification for Device Applications  

Microsoft Academic Search

This chapter considers device applications of ion beams that involve nanoscale modification of materials. It is necessarily\\u000a selective and does not include broad classes of applications such as ion beam assisted deposition of thin films or tribological\\u000a modification of surfaces for improved wear, corrosion resistance or biocompatibility. Instead it aims to illustrate the diversity\\u000a of ion beam applications by providing

Robert G. Elliman

310

Micro and nano-scale robotics  

Microsoft Academic Search

Micro- and nano-scale robotics has become a new emerging area of systems and controls area. These miniature robots have unique advantages such as accessing to unprecedented and small areas, increased flexibility, functionality and robustness, and being low cost, many (swarms), adaptive and distributed. The locomotion and manipulation dynamics of these robots are dominated by micro\\/nano-scale forces and the scaling effects.

Metin Sitti

2004-01-01

311

Molecular dynamics simulation of nanoscale liquid flows  

Microsoft Academic Search

Molecular dynamics (MD) simulation is a powerful tool to investigate the nanoscale fluid flow. In this article, we review\\u000a the methods and the applications of MD simulation in liquid flows in nanochannels. For pressure-driven flows, we focus on\\u000a the fundamental research and the rationality of the model hypotheses. For electrokinetic-driven flows and the thermal-driven\\u000a flows, we concentrate on the principle

Yuxiu LiJinliang XuDongqing Li; Jinliang Xu; Dongqing Li

2010-01-01

312

Nanoscale hybrid protein\\/polymer functionalized materials  

Microsoft Academic Search

Block copolymer-based membrane technology represents a versatile class of nanoscale materials in which biomolecules, such as membrane proteins, can be reconstituted. Our work has demonstrated the fabrication of large-area, protein- enhanced membranes that possess significant performance improvements in protein functionality. Among its many advantages over conventional lipid-based membrane systems, block copolymers can mimic natural cell biomembrane environments in a single

Dean Ho; Ben Chu; Hyeseung Lee; Carlo D. Montemagno

2004-01-01

313

A unique approach to accurately measure thickness in thick multilayers.  

PubMed

X-ray optics called multilayer Laue lenses (MLLs) provide a promising path to focusing hard X-rays with high focusing efficiency at a resolution between 5?nm and 20?nm. MLLs consist of thousands of depth-graded thin layers. The thickness of each layer obeys the linear zone plate law. X-ray beamline tests have been performed on magnetron sputter-deposited WSi(2)/Si MLLs at the Advanced Photon Source/Center for Nanoscale Materials 26-ID nanoprobe beamline. However, it is still very challenging to accurately grow each layer at the designed thickness during deposition; errors introduced during thickness measurements of thousands of layers lead to inaccurate MLL structures. Here, a new metrology approach that can accurately measure thickness by introducing regular marks on the cross section of thousands of layers using a focused ion beam is reported. This new measurement method is compared with a previous method. More accurate results are obtained using the new measurement approach. PMID:22514179

Shi, Bing; Hiller, Jon M; Liu, Yuzi; Liu, Chian; Qian, Jun; Gades, Lisa; Wieczorek, Michael J; Marander, Albert T; Maser, Jorg; Assoufid, Lahsen

2012-03-20

314

Treatment of chlorinated organic contaminants with nanoscale bimetallic particles  

Microsoft Academic Search

Nanoscale bimetallic particles (Pd\\/Fe, Pd\\/Zn, Pt\\/Fe, Ni\\/Fe) have been synthesized in the laboratory for treatment of chlorinated organic pollutants. Specific surface areas of the nanoscale particles are tens of times larger than those of commercially available microscale metal particles. Rapid and complete dechlorination of several chlorinated organic solvents and chlorinated aromatic compounds was achieved by using the nanoscale bimetallic particles.

Wei-xian Zhang; Chuan-Bao Wang; Hsing-Lung Lien

1998-01-01

315

Nanoscale Science and Engineering: A Priority Investment for NSF  

NSF Publications Database

... Researchers Developing Novel Method to Synthesize Semiconductor Nanowires Nanoscale Polymer Yields ... for selective drug delivery; catalysts for synthesizing specialized chemicals; and new types of ...

316

High-efficiency multilayer dielectric diffraction gratings  

Microsoft Academic Search

The design and performance of a new type of high-efficiency diffraction grating for use in either transmission or reflection are described. The gratings are produced in a multilayer dielectric coating deposited upon optically flat substrates. By proper design of the multilayer stack and grating structure, a diffraction efficiency in excess of 96% for polarized light in the {ital m}=-1 order

M. D. Perry; R. D. Boyd; J. A. Britten; D. Decker; B. W. Shore; C. Shannon; E. Shults

1995-01-01

317

Advanced multilayer x-ray optics.  

National Technical Information Service (NTIS)

Multilayer optics for the x-ray, soft x-ray and extreme ultra violet is a rapidly expanding and maturing field. A large part of the effort in this field is directed to improving the quality of multilayer structures by developing a better understanding of ...

T. W. Barbee

1990-01-01

318

LCA of biodegradable multilayer film from biopolymers  

Microsoft Academic Search

Multilayer films exhibit excellent properties for food packaging. However, existing products are not biodegradable. Conventional plastics, manufactured from fossil fuels, not only consume non-renewable and finite resources, but also impact heavily on waste disposal. A new multilayer film has been developed in the Multibio Project for the production of food packaging. In this paper, the environmental impacts of this new

Daniel Garraín; Rosario Vidal; Pilar Martínez; Vicente Franco; David Cebrián-Tarrasón

319

An electrode analysis for multilayer ceramic actuators  

Microsoft Academic Search

Electroelastic field concentrations ahead of electrodes in multilayer piezoelectric actuators are examined. By considering a representative unit in real multilayer actuators, the problem is formulated directly in terms of the electric potential between the electrode tips, results in a hyper-singular integral equation in which the unknown function is the electric potential. The analysis model is validated by comparison with a

Bao-Lin Wang; Yiu-Wing Mai

2005-01-01

320

Perpendicular giant magnetoresistance of magnetic multilayers  

Microsoft Academic Search

The theoretical and experimental studies of the giant magnetoresistance effect in metallic magnetic multilayers with measuring current perpendicular to the interface planes are reviewed. Theoretical formalisms of electronic transport in the inhomogeneous electron gas are critically compared with emphasis on the perpendicular magnetoresistance in multilayers. The effects of interface roughness, potential steps at the interfaces, and realistic band structures are

Martin A. M. Gijs; Gerrit E. W. Bauer

1997-01-01

321

Polyimide-glass multilayer printed wiring boards  

Microsoft Academic Search

Multilayer printed wiring boards (PWBs) from a polyimide\\/glass reinforced copper clad laminate and prepreg were manufactured. A lamination cycle and innerlayer copper surface treatment that gave satisfactory delamination resistance at soldering temperatures were developed. When compared to similar epoxy\\/glass multilayer PWBs, the polyimide PWBs had higher thermal stability, greater resistance to raised lands, fewer plating voids, less outgassing, and adhesion

J. W. Lula

1984-01-01

322

Coherent multilayer crystals and method of making  

DOEpatents

A new material is described consisting of a coherent multilayer crystal of two or more elements where each layer is composed of a single element. Each layer may vary in thickness from about 2 A to 2500 A. The multilayer crystals are prepared by sputter deposition under conditions which slow the sputtered atoms to near substrate temperatures before they contact the substrate.

Schuller, I.K.; Falco, C.M.

1980-10-30

323

Geometrical setting for the classification of multilayers  

Microsoft Academic Search

We elaborate on the consequences of the factorization of the transfer matrix of any lossless multilayer in terms of three basic matrices of simple interpretation. By considering the bilinear transformation that this transfer matrix induces in the complex plane, we introduce the concept of multilayer transfer function and study its properties in the unit disk. In this geometrical setting, our

Juan J. Monzón; Teresa Yonte; Luis L. Sánchez-Soto

2002-01-01

324

Subatomic accuracy in EUVL multilayer coatings  

NASA Astrophysics Data System (ADS)

Reported is the production of multilayer EUV coatings on 25000 mm2 large mirror substrates using e-beam based deposition. The accuracy achieved over the full area and the full multilayer stack amounts to an added figure error of 0.02 nm, i.e. in the sub-atomic distance range, thus meeting the future requirements on EUV coating technology.

Zoethout, Erwin; Suter, P.; van de Kruijs, R. W.; Yakshin, Andrey E.; Louis, Eric; Bijkerk, Fred; Enkisch, H.; Muellender, Stefan

2004-05-01

325

Electronic structure of multilayer graphene  

NASA Astrophysics Data System (ADS)

The single-particle low-energy Hamiltonian of bilayer graphene describes chiral quasiparticles with a dominantly parabolic dispersion exhibiting Berry phase 2?. This chiral Hamiltonian produces a doubly-degenerate zero-energy Landau level incorporating two different orbital states with the same energy. Taking into account spin and valley degeneracies, the zero-energy Landau level in a bilayer is eightfold degenerate, as compared to the fourfold degeneracy of other bilayer states and the fourfold degeneracy of all levels in a monolayer. Such levels can be split by interlayer asymmetry, due to the presence of an external gate or doping, or by interaction effects. This talk will describe the electronic behavior of multilayer graphene, focusing on three, four and five layers. The goal will be to identify features that are distinct from those observed in monolayers and bilayers, and to highlight effects - such as level splitting and crossing - that can be explained either within the single-particle picture or that require an understanding of electronic interactions. For example, the low-energy Hamiltonian of ABA-stacked multilayer graphene may be partially diagonalized into an approximate block-diagonal form, with each diagonal block contributing parabolic bands except for an additional block describing Dirac-like bands with a linear dispersion in a multilayer with an odd number of layers. By taking into account the symmetry of the crystal structure, it is possible to fully include the band parameters and to analyze their effect on the block-diagonal Hamiltonian. Next-nearest-layer couplings are shown to be particularly important in determining the low-energy spectrum and the phase diagram of the quantum Hall conductivity by causing energy shifts, level anti-crossings, and valley splitting of the low-lying Landau levels. [4pt] This work was done in collaboration with Mikito Koshino of the Department of Physics, Tohoku University, Sendai 980-8578, Japan.

McCann, Edward

2012-02-01

326

Figure correction of multilayer coated optics  

DOEpatents

A process is provided for producing near-perfect optical surfaces, for EUV and soft-x-ray optics. The method involves polishing or otherwise figuring the multilayer coating that has been deposited on an optical substrate, in order to correct for errors in the figure of the substrate and coating. A method such as ion-beam milling is used to remove material from the multilayer coating by an amount that varies in a specified way across the substrate. The phase of the EUV light that is reflected from the multilayer will be affected by the amount of multilayer material removed, but this effect will be reduced by a factor of 1-n as compared with height variations of the substrate, where n is the average refractive index of the multilayer.

Chapman; Henry N. (Livermore, CA), Taylor; John S. (Livermore, CA)

2010-02-16

327

Large Capacitance Multilayer Ceramic Capacitor  

Microsoft Academic Search

Large capacitance multilayer ceramic capacitors were made using a ceramic dieletric in the binary system Pb(Fe2\\/3Wl\\/3)O3-Pb(Fel\\/2Nbl\\/2)O3. The new capacitors used silver alloy as an internal electrode, reducing the capacitor cost significantly. It was then possible to make economical 10 µF ~ 400 µF muitilayer ceramic capacitors. Typical electrical properties of the new capacitors are listed below: Size 4.5 cm3Capacitance at

H. Takamizawa; K. Utsumi; M. Yonezawa; T. Ohno

1981-01-01

328

Fabrication of multilayer ferroelectric films  

Microsoft Academic Search

Multilayers of strontium bismuth tantalate (Sr0.9Bi2.2Ta2O9, SBT) with bismuth titanate (Bi4Ti3O12, BT), and SBT and strontium bismuth niobate (Sr0.9Bi2.2Nb2O9, SBN) with BT were prepared by chemical solution deposition (CSD). The CSD solutions were a mixture of strontium, tantalum, niobium and titanium butoxyethoxides and bismuth ethylhexanoate dissolved in butoxyethanol. SBT films were fabricated and annealed at 800°C for 60 min. Generally,

Deborah A. Neumayer; Peter R. Duncombe; Robert B. Laibowitz; Thomas Shaw; Lisa Berndt; C. T. Black; Alfred Grill

1999-01-01

329

C. elegans bicd-1, homolog of the Drosophila dynein accessory factor Bicaudal D, regulates the branching of PVD sensory neuron dendrites  

PubMed Central

The establishment of cell type-specific dendritic arborization patterns is a key phase in the assembly of neuronal circuitry that facilitates the integration and processing of synaptic and sensory input. Although studies in Drosophila and vertebrate systems have identified a variety of factors that regulate dendrite branch formation, the molecular mechanisms that control this process remain poorly defined. Here, we introduce the use of the Caenorhabditis elegans PVD neurons, a pair of putative nociceptors that elaborate complex dendritic arbors, as a tractable model for conducting high-throughput RNAi screens aimed at identifying key regulators of dendritic branch formation. By carrying out two separate RNAi screens, a small-scale candidate-based screen and a large-scale screen of the ?3000 genes on chromosome IV, we retrieved 11 genes that either promote or suppress the formation of PVD-associated dendrites. We present a detailed functional characterization of one of the genes, bicd-1, which encodes a microtubule-associated protein previously shown to modulate the transport of mRNAs and organelles in a variety of organisms. Specifically, we describe a novel role for bicd-1 in regulating dendrite branch formation and show that bicd-1 is likely to be expressed, and primarily required, in PVD neurons to control dendritic branching. We also present evidence that bicd-1 operates in a conserved pathway with dhc-1 and unc-116, components of the dynein minus-end-directed and kinesin-1 plus-end-directed microtubule-based motor complexes, respectively, and interacts genetically with the repulsive guidance receptor unc-5.

Aguirre-Chen, Cristina; Bulow, Hannes E.; Kaprielian, Zaven

2011-01-01

330

Advanced process control and novel test methods for PVD silicon and elastomeric silicone coatings utilized on ion implant disks, heatsinks and selected platens  

SciTech Connect

Coatings play multiple key roles in the proper functioning of mature and current ion implanters. Batch and serial implanters require strategic control of elemental and particulate contamination which often includes scrutiny of the silicon surface coatings encountering direct beam contact. Elastomeric Silicone Coatings must accommodate wafer loading and unloading as well as direct backside contact during implant plus must maintain rigid elemental and particulate specifications. The semiconductor industry has had a significant and continuous effort to obtain ultra-pure silicon coatings with sustained process performance and long life. Low particles and reduced elemental levels for silicon coatings are a major requirement for process engineers, OEM manufacturers, and second source suppliers. Relevant data will be presented. Some emphasis and detail will be placed on the structure and characteristics of a relatively new PVD Silicon Coating process that is very dense and homogeneous. Wear rate under typical ion beam test conditions will be discussed. The PVD Silicon Coating that will be presented here is used on disk shields, wafer handling fingers/fences, exclusion zones of heat sinks, beam dumps and other beamline components. Older, legacy implanters can now provide extended process capability using this new generation PVD silicon - even on implanter systems that were shipped long before the advent of silicon coating for contamination control. Low particles and reduced elemental levels are critical performance criteria for the silicone elastomers used on disk heatsinks and serial implanter platens. Novel evaluation techniques and custom engineered tools are used to investigate the surface interaction characteristics of multiple Elastomeric Silicone Coatings currently in use by the industry - specifically, friction and perpendicular stiction. These parameters are presented as methods to investigate the critical wafer load and unload function. Unique tools and test methods have been developed that deliver accurate and repeatable data, which will be described.

Springer, J.; Allen, B.; Wriggins, W.; Kuzbyt, R.; Sinclair, R. [Core Systems, 1050 Kifer Road Sunnyvale, CA 94086 (United States); FI Silicon, 1050 Kifer Road Sunnyvale, CA 94086 (United States); Core Systems, 1050 Kifer Road Sunnyvale, CA 94086 (United States)

2012-11-06

331

Polyelectrolyte Multilayers in Tissue Engineering  

PubMed Central

The layer-by-layer assembly of sequentially adsorbed, alternating polyelectrolytes has become increasingly important over the past two decades. The ease and versatility in assembling polyelectrolyte multilayers (PEMs) has resulted in numerous wide ranging applications of these materials. More recently, PEMs are being used in biological applications ranging from biomaterials, tissue engineering, regenerative medicine, and drug delivery. The ability to manipulate the chemical, physical, surface, and topographical properties of these multilayer architectures by simply changing the pH, ionic strength, thickness, and postassembly modifications render them highly suitable to probe the effects of external stimuli on cellular responsiveness. In the field of regenerative medicine, the ability to sequester growth factors and to tether peptides to PEMs has been exploited to direct the lineage of progenitor cells and to subsequently maintain a desired phenotype. Additional novel applications include the use of PEMs in the assembly of three-dimensional layered architectures and as coatings for individual cells to deliver tunable payloads of drugs or bioactive molecules. This review focuses on literature related to the modulation of chemical and physical properties of PEMs for tissue engineering applications and recent research efforts in maintaining and directing cellular phenotype in stem cell differentiation.

Detzel, Christopher J.; Larkin, Adam L.

2011-01-01

332

Method to adjust multilayer film stress induced deformation of optics  

Microsoft Academic Search

Stress compensating systems that reduces\\/compensates stress in a multilayer without loss in reflectivity, while reducing total film thickness compared to the earlier buffer-layer approach. The stress free multilayer systems contain multilayer systems with two different material combinations of opposite stress, where both systems give good reflectivity at the design wavelengths. The main advantage of the multilayer system design is that

Eberhard A. Spiller; Paul B. Mirkarimi; Claude Montcalm; Sasa Bajt; James A. Folta

2000-01-01

333

Numerical studies of multilayer gratings using the method of eigenvectors  

Microsoft Academic Search

The method of eigenvectors has been adapted for numerical studies of lamellar multilayer gratings with a partially etched multilayer stack (phase multilayer gratings). Unlike the existing modal and differential methods, this method can be applied to thick multilayer gratings with a small grating period, and also to the case of grazing incidence of radiation. For the case of soft X-rays,

V. I. Erofeev; N. V. Kovalenko

1998-01-01

334

An X-ray grazing incidence phase multilayer grating  

Microsoft Academic Search

An X-ray grazing incidence phase multilayer grating, representing a thin grating placed on a multilayer mirror, is proposed. A high efficiency of grating diffraction can be obtained by the possibility of changing the phase shift of the wave diffracted from the multilayer under the Bragg and total external reflection conditions. A grazing incidence phase multilayer grating consisting of Pt grating

V. A. Chernov; N. V. Kovalenko; S. V. Mytnichenko

2001-01-01

335

EDITORIAL: Light Control at the Nanoscale  

NASA Astrophysics Data System (ADS)

It is customary to denote as 'nano-systems' entities whose size varies between 1 and 100 nm. Such systems span an immense variety of structures, ranging from large molecules, quantum dots, and nanowires, to viruses. Their existence is based on, and accompanied by, an amazing abundance of phenomena, depending on a huge number of parameters, all of which can in principle be used for nanoscale control. One of the most potent means of controlling nano-systems is light: it can serve as a tool for the addressing, preparation, stabilization and excitation of nano-systems. Design of light control scenarios is based on the laser techniques of coherent and optimal control at wavelengths and time sequencing most appropriate to the nano-systems, or on more traditional, incoherent forms of light-matter interactions. This special issue of Journal of Physics B: Atomic, Molecular and Optical Physics (J. Phys. B) devoted to the subject of light control at the nanoscale contains a collection of articles that cover several key areas in this fast-growing field. These include: preparation and manipulation of nano-systems by light, nanoscale plasmonics and spintronics, Bose-Einstein condensation and excitation of novel molecular and crystalline systems. We have grouped the papers according to these general areas. The guest editors gratefully acknowledge the help of the staff of J. Phys. B, especially that of Alice Malhador from the editorial team, and Adrian Corrigan from production, in preparing this issue, and Professor Jan-Michel Rost, the Editor-in-Chief, for his support of this project.

Kral, Petr; Shapiro, Moshe

2007-06-01

336

Dustiness of fine and nanoscale powders.  

PubMed

Dustiness may be defined as the propensity of a powder to form airborne dust by a prescribed mechanical stimulus; dustiness testing is typically intended to replicate mechanisms of dust generation encountered in workplaces. A novel dustiness testing device, developed for pharmaceutical application, was evaluated in the dustiness investigation of 27 fine and nanoscale powders. The device efficiently dispersed small (mg) quantities of a wide variety of fine and nanoscale powders, into a small sampling chamber. Measurements consisted of gravimetrically determined total and respirable dustiness. The following materials were studied: single and multiwalled carbon nanotubes, carbon nanofibers, and carbon blacks; fumed oxides of titanium, aluminum, silicon, and cerium; metallic nanoparticles (nickel, cobalt, manganese, and silver) silicon carbide, Arizona road dust; nanoclays; and lithium titanate. Both the total and respirable dustiness spanned two orders of magnitude (0.3-37.9% and 0.1-31.8% of the predispersed test powders, respectively). For many powders, a significant respirable dustiness was observed. For most powders studied, the respirable dustiness accounted for approximately one-third of the total dustiness. It is believed that this relationship holds for many fine and nanoscale test powders (i.e. those primarily selected for this study), but may not hold for coarse powders. Neither total nor respirable dustiness was found to be correlated with BET surface area, therefore dustiness is not determined by primary particle size. For a subset of test powders, aerodynamic particle size distributions by number were measured (with an electrical low-pressure impactor and an aerodynamic particle sizer). Particle size modes ranged from approximately 300 nm to several micrometers, but no modes below 100 nm, were observed. It is therefore unlikely that these materials would exhibit a substantial sub-100 nm particle contribution in a workplace. PMID:23065675

Evans, Douglas E; Turkevich, Leonid A; Roettgers, Cynthia T; Deye, Gregory J; Baron, Paul A

2012-10-12

337

Scanning tunnelling microscopy of novel nanoscale materials  

NASA Astrophysics Data System (ADS)

This dissertation is divided into three main parts. The first section describes an low temperature, ultra high vacuum (UHV) scanning tunnelling microscope (STM) system designed and built mainly by Phil Collins, a former Zettl group student, and Masa Ishigami. The system was designed specifically for investigating electronic properties of nanoscale materials. The second section discusses scanning tunnelling microscopy experiments on three novel nanoscale materials. Results of tunnelling microscopy and spectroscopy on endohedral fullerenes (Sc3N C80) are addressed in Chapter 3. Air-sensitivity of electronic properties of carbon nanotubes was discovered using a room temperature environmental STM and the description of the experiment is located in Chapter 4. Chapter 4 also discusses a novel integrated experimental/theoretical technique developed in collaboration with the Louie and Cohen theory groups for analyzing the STM images of defects on carbon nanotubes and nanoscale materials. In Chapter 5, the results on boron nitride nanotubes (BNNTs) are reported. Under relatively intense electric fields in the tunnelling junctions, BNNTs exhibited the signs of the so-called Giant Stark Effect which significantly reduces the band gap of BNNTs. The third section is focused on the results of synthesis experiments. The simplified synthesis technique suitable for an inexpensive, 100% duty cycle production for multi-walled carbon nanotubes is described in Chapter 6. Attempts to purify C36 in bulk quantities are discussed in Chapter 7. Chapter 8 details the design of the sample holder for air-sensitive samples for magnetic measurements using a Quantum Design magnetometer. The magnetic properties of a potassium-pyridine complex are presented in Chapter 9.

Ishigami, Masahiro

338

Nanoscale growth twins in sputtered metal films  

SciTech Connect

We review recent studies on the mechanical properties of sputtered Cu and 330 stainless steel films with {l_brace}1 1 1{r_brace} nanoscale growth twins preferentially oriented perpendicular to growth direction. The mechanisms of formation of growth twins during sputtering and the deformation mechanisms that enable usually high strengths in nanotwinned structures are highlighted. Growth twins in sputtered films possess good thermal stability at elevated temperature, providing an approach to extend the application of high strength nanostructured metals to higher temperatures.

Misra, Amit [Los Alamos National Laboratory; Anderoglu, Osman [Los Alamos National Laboratory; Hoagland, Richard G [Los Alamos National Laboratory; Zhang, X [TEXAS A& M

2008-01-01

339

Nanoscale organic light-emitting diodes.  

PubMed

This study reports the fabrication and characterization of nanoscale organic light-emitting diodes (nano-OLEDs) based on poly[2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylene vinylene] (MEH-PPV). The nano-OLEDs were fabricated by spin casting MEH-PPV into cylindrical nanoholes lithographically patterned into silicon nitride. The electroluminescence (EL) spectrum of MEH-PPV was similar to its photoluminescence spectrum, confirming radiative decay from the same excited state. Device characteristics in the form of current density and EL versus applied electric field are presented and compared with those of a large-scale OLED. PMID:16351200

Yamamoto, Hiromichi; Wilkinson, John; Long, James P; Bussman, Konrad; Christodoulides, Joseph A; Kafafi, Zakya H

2005-12-01

340

Synthesis, dynamics and photophysics of nanoscale systems  

NASA Astrophysics Data System (ADS)

The emerging field of nanotechnology, which spans diverse areas such as nanoelectronics, medicine, chemical and pharmaceutical industries, biotechnology and computation, focuses on the development of devices whose improved performance is based on the utilization of self-assembled nanoscale components exhibiting unique properties owing to their miniaturized dimensions. The first phase in the conception of such multifunctional devices based on integrated technologies requires the study of basic principles behind the functional mechanism of nanoscale components, which could originate from individual nanoobjects or result as a collective behaviour of miniaturized unit structures. The comprehensive studies presented in this thesis encompass the mechanical, dynamical and photophysical aspects of three nanoscale systems. A newly developed europium sulfide nanocrystalline material is introduced. Advances in synthetic methods allowed for shape control of surface-functionalized EuS nanocrystals and the fabrication of multifunctional EuS-CdSe hybrid particles, whose unique structural and optical properties hold promise as useful attributes of integrated materials in developing technologies. A comprehensive study based on a new class of multifunctional nanomaterials, derived from the basic unit of barcoded metal nanorods is presented. Their chemical composition affords them the ability to undergo autonomous motion in the presence of a suitable fuel. The nature of their chemically powered self-propulsion locomotion was investigated, and plausible mechanisms for various motility modes were presented. Furthermore functionalization of striped metallic nanorods has been realized through the incorporation of chemically controlled flexible hinges displaying bendable properties. The structural aspect of the light harvesting machinery of a photosynthetic cryptophyte alga, Rhodomonas CS24, and the mobility of the antenna protein, PE545, in vivo were investigated. Information obtained through a combination of steady-state and time-resolved spectroscopy in conjunction with quantum chemical calculations aided in the elucidation of the dynamics and the mechanism of light harvesting in the multichromophoric phycobiliprotein phycocyanin PC645 in vitro. Investigation of the light-harvesting efficiency and optimization of energy transfer with respect to the structural organization of light-harvesting chromophores on the nanoscale, can provide us with fundamental information necessary for the development of synthetic light-harvesting devices capable of mimicking the efficiency of the natural system.

Mirkovic, Tihana

341

Parallel optical nanolithography using nanoscale bowtie apertures  

NASA Astrophysics Data System (ADS)

Over the past two decades various branches of science and engineering have developed techniques for producing nanoscopic light sources for different applications such as imaging, detection and fabrication. These areas include near-field scanning optical microscopy (NSOM), surface-enhanced Raman scattering and detection (SERS), plasmonics and so on. In particular nanolithography techniques have been developed to produce feature sizes in the sub-100 nm length scales. These processes include variations of standard photolithography process to achieve high resolution, optical fiber-based near-field lithography, surface plasmon assisted nanolithography, interference optical lithography and so on. This work presents a study of the viability of using nanoscale bowtie apertures for nanolithography. Bowtie apertures exhibit a unique property of supporting a propagating TE10 mode at wavelengths of light in the visible and near-UV regimes. The energy of this mode is concentrated in the gap region of the aperture and thus these apertures have the potential to produce high intensity nanoscale light spots that can be used for nano-patterning applications. We demonstrate this capability of nanoscale bowtie apertures by patterning photoresist to obtain resolution less than 100 nm. Initially we present the results from static lithography experiments and show that the ridge apertures of different shapes -- C, H and bowtie produce holes in the photoresist of dimensions around 50-60 nm. Subsequently we address the issues involved in using these apertures for nano directwriting. We show that chromium thin-films offer a viable solution to produce high quality metal films of surface roughness less than 1 nm over an area of 25 mum2. This is indeed important to achieve intimate contact between the apertures and the photoresist surface. We also explain ways to decrease friction between the mask and photoresist surfaces during nano direct-writing. In addition, to decrease the contact force needed to bring an array of bowtie apertures into intimate contact with the photoresist surface we present an optical interference based alignment system that aligns the mask and photoresist surfaces to within 0.1 mrad of parallelism. In this work we show that bowtie apertures can be used to produce patterns in the photoresist of dimensions in the order of 85-90 nm. We also demonstrate parallel optical nanolithography using an array of bowtie apertures that opens up the possibility of using arrays of bowtie apertures to produce a large number of nanoscale light spots for parallel nano-manufacturing.

Uppuluri, Sreemanth M. V.

342

Energy dissipation in a dynamic nanoscale contact  

NASA Astrophysics Data System (ADS)

The size of an atomic force microscope tip can vary rapidly during interaction with a surface but this is typically overlooked. Here, we treat the tip radius as a dynamic variable. Comparison with nanoscission of DNA molecules shows that the pressure in the nanoscale contact cannot increase without bound, rather the tip gradually blunts as the energy in the cantilever is increased. We develop a method to stabilize the tip and then reliably calculate the effective area of interaction and dissipation of eV/atom in situ. Tip radius typically stabilizes around 20-30 nm and keeps the maximum pressure below ~1 GPa.

Santos, Sergio; Thomson, Neil H.

2011-01-01

343

Nanoscale plasmon waveguide including cavity resonator.  

PubMed

The propagation and filtering of surface plasmon polaritons in metal-insulator-metal nanosandwiches are investigated by using finite-difference time domain simulation. We study the optical transmission of a nanoscale waveguide coupled to a cavity situated either in the vicinity or in the interior of the waveguide. Depending on whether the cavity is inside or at the side of the waveguide, the transmission spectrum displays respectively peaks or dips which occur at the same frequencies. We study the dip and peak frequencies in the transmission spectrum as a function of the geometrical parameters of the cavity and the thickness of the metallic gap separating the guide from the cavity. PMID:21832343

Noual, A; Pennec, Y; Akjouj, A; Djafari-Rouhani, B; Dobrzynski, L

2009-08-17

344

Graphene: nanoscale processing and recent applications  

NASA Astrophysics Data System (ADS)

One of the most interesting features of graphene is the rich physics set up by the various nanostructures it may adopt. The planar structure of graphene makes this material ideal for patterning at the nanoscale. The breathtakingly fast evolution of research on graphene growth and preparation methods has made possible the preparation of samples with arbitrary sizes. Available sample production techniques, combined with the right patterning tools, can be used to tailor the graphene sheet into functional nanostructures, even whole electronic circuits. This paper is a review of the existing graphene patterning techniques and potential applications of related lithographic methods.

Biró, László P.; Nemes-Incze, Péter; Lambin, Philippe

2012-03-01

345

Nanoscale optical reinforcement for enhanced reversible holography.  

PubMed

We demonstrate a nanoscale optical reinforcement concept for reversible holographic recording. The bone-muscle-like mechanism enables enhancement of holographic grating formation due to the collective alignment of liquid crystal (LC) molecules nearby photo-reconfigurable polymer backbones. The LC fluidity facilitates the ease of polymer chain transformation during the holographic recording while the polymer network stabilizes the LC collective orientation and the consequential optical enhancement after the recording. As such, the holographic recording possesses both long-term persistence and real-time rewritability. PMID:22330546

Wu, Pengfei; Sun, Sam Qunhui; Baig, Sarfaraz; Wang, Michael R

2012-01-30

346

The evolution of nanoscale quantum effects in semiconductor physics  

Microsoft Academic Search

In the early twentieth century, encounters with physical phenomena which require detailed analyses in nanoscale, such as electron motion, prompted the advent of quantum mechanics, since Newtonian mechanics could not possibly provide an adequate explanation for them. Electron tunneling through nanoscale barriers is the most direct consequence of the law of quantum mechanics, for which the Esaki tunnel diode gave

Leo Esaki

1999-01-01

347

Tg and Cure of a Polycyanurate at the Nanoscale  

Microsoft Academic Search

Nanoscale constraint is known to have a significant impact on the thermal properties of materials. Although thermosetting resins have been cured in the presence of nanoparticles and nanotubes, cure of thermosetting resins under the well defined nanoscale constraints imposed by controlled pore glass (CPG) or similar matrices has not been previously documented. In this work, we investigate the isothermal curing

Sindee Simon; Qingxiu Li

2008-01-01

348

Quantifying Nanoscale Order in Amorphous Materials via Fluctuation Electron Microscopy  

ERIC Educational Resources Information Center

|Fluctuation electron microscopy (FEM) has been used to study the nanoscale order in various amorphous materials. The method is explicitly sensitive to 3- and 4-body atomic correlation functions in amorphous materials; this is sufficient to establish the existence of structural order on the nanoscale, even when the radial distribution function…

Bogle, Stephanie Nicole

2009-01-01

349

Size Effect Down to Nanoscales: Function over Strength  

Microsoft Academic Search

Exceptional physical and biochemical functions of matter and devices become predominant when size down to nanoscale, although strength of solids may also have strong size effects. The emerging of the molecular physical mechanics as the theoretical fundamental of the new interdisciplinary fields is discussed to meet the requirement of development in science and technology. New examples in nanoscale tribology, thermal

WANLIN GUO; YUFENG GUO

350

Programmable Resistance Switching in Nanoscale Two-Terminal Devices  

Microsoft Academic Search

We show that in nanoscale two-terminal resistive switches the resistance switching can be dominated by the formation of a single conductive filament. The probabilistic filament formation process strongly affects the device operation principle, and can be programmed to facilitate new functionalities such as multibit switching with partially formed filaments. In addition, the nanoscale switches exhibit excellent performance metrics making them

Sung Hyun Jo; Kuk-Hwan Kim; Wei Lu

2009-01-01

351

Essential physics of carrier transport in nanoscale MOSFETs  

Microsoft Academic Search

The device physics of nanoscale MOSFETs is explored by numerical simulations of a model transistor. The physics of charge control, source velocity saturation due to thermal injection, and scattering in ultrasmall devices are examined. The results show that the essential physics of nanoscale MOSFETs can be understood in terms of a conceptually simple scattering model

Mark Lundstrom; Zhibin Ren

2002-01-01

352

Energy Bounds for Fault-Tolerant Nanoscale Designs  

Microsoft Academic Search

The problem of determining lower bounds for the energy cost of a given nanoscale design is addressed via a complexity theory-based approach. This paper provides a theoretical framework that is able to assess the trade-offs existing in nanoscale designs between the amount of redundancy needed for a given level of resilience to errors and the associated energy cost. Circuit size,

Diana Marculescu

2005-01-01

353

Terbium-Based Extreme Ultraviolet Multilayers  

SciTech Connect

We have fabricated periodic multilayers that comprise either Si/Tb or SiC/Tb bilayers, designed to operate as narrowband reflective coatings near 60 nm wavelength in the extreme ultraviolet (EUV). We find peak reflectance values in excess of 20% near normal incidence. The spectral bandpass of the best Si/Tb multilayer was measured to be 6.5 nm full width at half-maximum (FWHM), while SiC/Tb multilayers have a more broad response, of order 9.4 nm FWHM. Transmission electron microscopy analysis of Si/Tb multilayers reveals polycrystalline Tb layers, amorphous Si layers, and relatively large asymmetric amorphous interlayers. Thermal annealing experiments indicate excellent stability to 100 C (1 h) for Si/Tb. These new multilayer coatings have the potential for use in normal incidence instrumentation in a region of the EUV where efficient narrowband multilayers have not been available until now. In particular, reflective Si/Tb multilayers can be used for solar physics applications where the coatings can be tuned to important emission lines such as O V near 63.0 nm and Mg X near 61.0 nm.

Windt,D.; Seely, J.; Kjornrattanawich, B.; Uspenskii, Y.

2005-01-01

354

Scanning Coherent X-ray Diffraction Imaging of Pinned GdFe Magnetic Multilayers  

NASA Astrophysics Data System (ADS)

Crucial to understanding fundamental physics puzzles such as colossal magnetoresistance and developing future technologies for magnetic data storage is an understanding of the nanoscale behavior of magnetism. We study Gd/Fe multilayers exhibiting ordered stripes due to perpendicular magnetic anisotropy (PMA) that are pinned by artificial Au patterns. Using element sensitivity and depth resolution of Coherent X-ray Diffraction Imaging (CXDI), we investigate the magnetic domain structure, observing the role of disorder in the formation and stability of the magnetic domains. We recorded coherent diffraction data by scanning overlapping regions on the sample using linearly polarized light both on and off the Gd M5 resonant edge These diffraction patterns are then numerically inverted using ptychographic iterative algorithms to give a high resolution map of the Au structure and the ferromagnetic domain configuration as we scan through the magnetization hysteresis loop.

Dietze, Sebastian; Marsh, Moses; Tripathi, Ashish; Uhlir, Vojtech; Fullerton, Eric; Vine, David; McNulty, Ian; Shpyrko, Oleg

2012-02-01

355

Enhanced performance of EUV multilayer coatings  

NASA Astrophysics Data System (ADS)

Reported is a summary of the development of EUV Mo/Si multilayer coating technology. Though the results are developed for application in Extreme Ultraviolet Lithography, they are of a broader relevance including optics for astronomy. The coating process used consists of electron beam evaporation in combination with low energy ion beam smoothening. The radiation hardness of these coatings is discussed and methods to reduce the multilayer induced substrate stress. The reflectance of the coatings, which are covered with a special protective capping layer, is typically around 65%, while the non correctable figure error added by the full multilayer stack is controlled to better than 15 picometer.

Louis, E.; Yakshin, A. E.; Zoethout, E.; van de Kruijs, R. W. E.; Nedelcu, I.; van der Westen, S. A.; Tsarfati, T.; Bijkerk, F.; Enkisch, H.; Müllender, S.; Wolschrijn, B.; Mertens, B.

2005-08-01

356

Poroelasticity of Cartilage at the Nanoscale  

PubMed Central

Atomic-force-microscopy-based oscillatory loading was used in conjunction with finite element modeling to quantify and predict the frequency-dependent mechanical properties of the superficial zone of young bovine articular cartilage at deformation amplitudes, ?, of ?15 nm; i.e., at macromolecular length scales. Using a spherical probe tip (R ? 12.5 ?m), the magnitude of the dynamic complex indentation modulus, |E?|, and phase angle, ?, between the force and tip displacement sinusoids, were measured in the frequency range f ? 0.2–130 Hz at an offset indentation depth of ?0 ? 3 ?m. The experimentally measured |E?| and ? corresponded well with that predicted by a fibril-reinforced poroelastic model over a three-decade frequency range. The peak frequency of phase angle, fpeak, was observed to scale linearly with the inverse square of the contact distance between probe tip and cartilage, 1/d2, as predicted by linear poroelasticity theory. The dynamic mechanical properties were observed to be independent of the deformation amplitude in the range ? = 7–50 nm. Hence, these results suggest that poroelasticity was the dominant mechanism underlying the frequency-dependent mechanical behavior observed at these nanoscale deformations. These findings enable ongoing investigations of the nanoscale progression of matrix pathology in tissue-level disease.

Nia, Hadi Tavakoli; Han, Lin; Li, Yang; Ortiz, Christine; Grodzinsky, Alan

2011-01-01

357

Transport and structure in nanoscale channels  

NASA Astrophysics Data System (ADS)

Driven by the rapidly advancing fields of nano- and biotechnology, there has been an explosion of interest in molecular transport and structure formation on small length scales. A canonical model for the transport of particles along one dimensional pathways in nanoscale channels is the Totally Asymmetric Simple Exclusion Process (TASEP). After introducing the standard TASEP, modifications of the TASEP designed to increase its utility in modeling biological transport processes are described. One variant of the TASEP is particularly suitable for modeling protein translation, and the results of using this variant to investigate the effects of slow-codons on the translation process are discussed. A related topic is the voltage-driven translocation of DNA hairpins through membrane-embedded nanopores. Motivated by recent experiments, a stochastic model is developed that couples the translocation and dehybridization of the DNA hairpin. This model is used to explore the behaviour of the mean translocation time of hairpins as a function of driving voltage, and two translocation mechanisms are identified and discussed. Finally, the adsorption and equilibrium structures of water in the interior of ion-bearing nanoscale pores are considered. The behaviour of water and ions under confinement is critical to the functioning of biological ion channels and nanoporous filters. Here, the adsorption isotherms of water are examined, and the layered structures formed by the confined water are described.

Lakatos, Gregory William

358

Channeling technique to make nanoscale ion beams  

NASA Astrophysics Data System (ADS)

Particle channeling in a bent crystal lattice has led to an efficient instrument for beam steering at accelerators [Biryukov et al., Crystal Channeling and its Application at High Energy Accelerators, Springer, Berlin, 1997], demonstrated from MeV to TeV energies. In particular, crystal focusing of high-energy protons to micron size has been demonstrated at IHEP with the results well in match with Lindhard (critical angle) prediction. Channeling in crystal microstructures has been proposed as a unique source of a microbeam of high-energy particles [Bellucci et al., Phys. Rev. ST Accel. Beams 6 (2003) 033502]. Channeling in nanostructures (single-wall and multi-wall nanotubes) offers the opportunities to produce ion beams on nanoscale. Particles channeled in a nanotube (with typical diameter of about 1 nm) are trapped in two dimensions and can be steered (deflected, focused) with the efficiency similar to that of crystal channeling or better. This technique has been a subject of computer simulations, with experimental efforts under way in several high-energy labs, including IHEP. We present the theoretical outlook for making channeling-based nanoscale ion beams and report the experience with crystal-focused microscale proton beams.

Biryukov, V. M.; Bellucci, S.; Guidi, V.

2005-04-01

359

Molecular dynamics studies on nanoscale gas transport  

NASA Astrophysics Data System (ADS)

Three-dimensional molecular dynamics (MD) simulations of nanoscale gas flows are studied to reveal surface effects. A smart wall model that drastically reduces the memory requirements of MD simulations for gas flows is introduced. The smart wall molecular dynamics (SWMD) represents three-dimensional FCC walls using only 74 wall Molecules. This structure is kept in the memory and utilized for each gas molecule surface collision. Using SWMD, fluid behavior within nano-scale confinements is studied for argon in dilute gas, dense gas, and liquid states. Equilibrium MD method is employed to resolve the density and stress variations within the static fluid. Normal stress calculations are based on the Irving-Kirkwood method, which divides the stress tensor into its kinetic and virial parts. The kinetic component recovers pressure based on the ideal gas law. The particle-particle virial increases with increased density, while the surface-particle virial develops due to the surface force field effects. Normal stresses within nano-scale confinements show anisotropy induced primarily by the surface force-field and local variations in the fluid density near the surfaces. For dilute and dense gas cases, surface-force field that extends typically 1nm from each wall induces anisotropic normal stress. For liquid case, this effect is further amplified by the density fluctuations that extend beyond the three field penetration region. Outside the wall force-field penetration and density fluctuation regions the normal stress becomes isotropic and recovers the thermodynamic pressure, provided that sufficiently large force cut-off distances are utilized in the computations. Next, non-equilibrium SWMD is utilized to investigate the surface-gas interaction effects on nanoscale shear-driven gas flows in the transition and free molecular flow regimes. For the specified surface properties and gas-surface pair interactions, density and stress profiles exhibit a universal behavior inside the wall force penetration region at different flow conditions. Shear stress results are utilized to calculate the tangential momentum accommodation coefficient (TMAC) between argon gas and FCC walls. The TMAC value is shown to he independent of the now properties and Knudsen number in all simulations. Velocity profiles show distinct deviations from the kinetic theory based solutions inside the wall force penetration depth, while they match the linearized Boltzmann equation solution outside these zones. Afterwards, surface effects are studied as a function of the surface-gas potential strength ratio (epsilon wf/epsilonff) for the shear driven argon gas flows in the early transition and tree molecular flow regimes. Results show that increased epsilonwf/epsilon ff results in increased gas density, leading towards monolayer adsorption on surfaces. The near wall velocity profile shows reduced gas slip, and eventually velocity stick with increased epsilonwf/epsilon ff. Similarly, using MD predicted shear stress values and kinetic theory, TMAC are calculated as a function of epsilonwf/epsilon ff and TMAC values are shown to be independent of the Knudsen number. Results indicate emergence of the wall force field penetration depth as an additional length scale for gas flows in nano-channels, breaking the dynamic similarity between rarefied and nano-scale gas flows solely based on the Knudsen and Mach numbers.

Barisik, Murat

360

Investigation on effect of weight ratios of PEG to BaTiO3 on PVdF-HFP nano composites for Li-ion batteries  

NASA Astrophysics Data System (ADS)

In the present study Polyethylene Glycol 2000(PEG2000)-Barium Titanate(BaTiO3) in five different weight ratios were physically blended to the plasticized PVdF-HFP/LIBETI matrix to study the ionic conductivity thermal, morphology and XRD properties was attempted. The ionic Conductivity observation show that 15:5wt% PEG:BaTiO3 only improved magnitude of conductivity 1.256×10-5 S/cm (Sample-V2) than 20:0(V1), 10:10(V3), 5:15(V4), 0:20(V5). The XRD profile show the suppression of ?-phase of PVdF and presence of BaTiO3, irrespective of increase/decrease in the mass gradient of PEG, and not supportive of the conductivity beyond V2 was noted. The TGA on PEG:BaTiO3 20:0(V1), 0:20(V5) and, 15:5(V2) it was observed that V1 underwent three stages of weight losses and V5 with single stage (over the sample V2) suggest that membrane not having more weight losses due to higher aggregation of filler was observed.

Vickraman, P.; Ravindran, D.

2013-06-01

361

Basic Formulae of XUV Multilayer Optics  

Microsoft Academic Search

The theory of multilayer optics relevant to the following fields of application is given: The choice of materials for efficient XUV reflectors, Obtainment of high spectral resolution, Construction of polarizers and collimators for XUV beams.

I. V. Kozhevnikov; A. V. Vinogradov

1987-01-01

362

Synthesis and evaluation of thermoelectric multilayer films  

SciTech Connect

The deposition of compositionally modulated (Bi{sub 1-x}Sb{sub x}){sub 2}(Te{sub 1-y}Se{sub y}){sub 3} thermoelectric multilayer films by magnetron sputtering has been demonstrated. Structures with a period of 140{Angstrom} are shown to be stable to interdiffusion at the high deposition temperatures necessary for growth of single layer crystalline films with ZT {gt} 0.5. These multilayers are of the correct dimension to exhibit the electronic properties of quantum well structures. Furthermore it is shown that the Seebeck coefficient of the films is not degraded by the presence of this multilayer structure. It may be possible to synthesize a multilayer thermoelectric material with enhanced ZT by maximizing the barrier height through optimization of the composition of the barrier.

Wagner, A.V.; Foreman, R.J.; Summers, L.J.; Barbee, T.W. Jr.; Farmer, J.C.

1996-03-21

363

Diffuse Multilayer Analysis Using a Multiflux Method.  

National Technical Information Service (NTIS)

The use of uniform material layers to form multilayer films forms the basis for an extensive coating technology. The transmissive and reflective properties of such structures are dominated by optical interference occurring among the layers. Comparatively ...

S. O. Sari

1985-01-01

364

Plasma etchback of multilayer printed wiring boards  

SciTech Connect

Removal of epoxy smear and glass fiber protrusions in multilayer printed wiring board holes was investigated. Gas plasma techniques, using a mixture of carbon tetrafluoride and oxygen, removed the eposies; however, the glass fibers were not affected.

Gentry, F.L.

1980-06-01

365

Fabrication and Properties of Multilayer Structures.  

National Technical Information Service (NTIS)

the goal of this program is to develop vapor desposition processes for application to integrated circuit technology, particularly multilayer applications. Its purpose is to investigate vapor deposition techniques that offer potential for synthesis of mate...

W. A. Tiller T. W. Barbee W. Dibble L. Nagel A. Savan

1981-01-01

366

Microwave sintering of multilayer ceramic capacitors.  

National Technical Information Service (NTIS)

Multilayer ceramic capacitors of several compositions (both Z5U and NPO types) were sintered in air in both conventional and microwave furnaces. Several casketing and insulation techniques were used to improve temperature uniformity and minimize dopant lo...

R. J. Lauf C. E. Holcombe C. Hamby

1992-01-01

367

Molybdenum-ruthenium/beryllium multilayer coatings  

SciTech Connect

A newly developed beryllium-based multilayer system consisting of polycrystalline Be and amorphous MoRu layers is presented. The multilayer exhibits many remarkable properties: reflectivity as high as 69.3% at a wavelength of 11.4 nm (achieved with 50 bilayers giving a bandwidth of 0.35 nm), near-zero intrinsic stress, and excellent smoothing properties. As compared with Mo/Si multilayers at 13.4 nm, the shorter wavelength of 11.4 nm is better matched to the spectral output of gas-jet laser produced plasma sources, allowing a much higher optical throughput of the extreme ultraviolet lithography (EUVL) tool. The properties of MoRu/Be are compared to other beryllium-based multilayers, which have been considered for reflective coatings for EUVL optics. (c) 2000 American Vacuum Society.

Bajt, Sasa [Information Science and Technology Program, Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)

2000-03-01

368

Pulsed laser irradiation of metal multilayers.  

SciTech Connect

Vapor-deposited, exothermic metal-metal multilayer foils are an ideal class of materials for detailed investigations of pulsed laser-ignited chemical reactions. Created in a pristine vacuum environment by sputter deposition, these high purity materials have well-defined reactant layer thicknesses between 1 and 1000 nm, minimal void density and intimate contact between layers. Provided that layer thicknesses are made small, some reactive metal-metal multilayer foils can be ignited at a point by laser irradiation and exhibit subsequent high-temperature, self-propagating synthesis. With this presentation, we describe the pulsed laser-induced ignition characteristics of a single multilayer system (equiatomic Al/Pt) that exhibits self-propagating synthesis. We show that the thresholds for ignition are dependent on (i) multilayer design and (ii) laser pulse duration. With regard to multilayer design effects on ignition, there is a large range of multilayer periodicity over which ignition threshold decreases as layer thicknesses are made small. We attribute this trend of decreased ignition threshold to reduced mass transport diffusion lengths required for rapid exothermic mixing. With regard to pulse duration effects, we have determined how ignition threshold of a single Al/Pt multilayer varies with pulse duration from 10{sup -2} to {approx} 10{sup -13} sec (wavelength and spot size are held constant). A higher laser fluence is required for ignition when using a single laser pulse {approx} 100 fs or 1 ps compared with nanosecond or microsecond exposure, and we attribute this, in part, to the effects of reactive material being ablated when using the shorter pulse durations. To further understand these trends and other pulsed laser-based processes, our discussion concludes with an analysis of the heat-affected depths in multilayers as a function of pulse duration.

Adams, David Price; McDonald, Joel Patrick

2010-11-01

369

Cylindrical x-ray multilayer monochromator  

Microsoft Academic Search

We have designed and built a cylindrical grazing incidence monochromator (mirror) for 1.54⫠CuKα x-rays. W\\/C multilayers were deposited onto thin sheets of mica and then bent into cylindrical shapes. The favorable properties of mica, including monolayer smoothness and malleability when used in very thin sheets, provide an ideal substrate material. X-ray diffraction measurements indicate a multilayer d spacing of

Peter C. Gabriele; Richard M. Bionta; Alan F. Jankowski

1989-01-01

370

Multilayer nanofilms as substrates for hepatocellular applications  

Microsoft Academic Search

Multilayer nanofilms, formed by the layer-by-layer (LbL) adsorption of positively and negatively charged polyelectrolytes, are promising substrates for tissue engineering. We investigate here the attachment and function of hepatic cells on multilayer films in terms of film composition, terminal layer, rigidity, charge, and presence of biofunctional species. Human hepatocellular carcinoma (HepG2) cells, adult rat hepatocytes (ARH), and human fetal hepatoblasts

Corinne R. Wittmer; Jennifer A. Phelps; Christin M. Lepus; William M. Saltzman; Martha J. Harding; Paul R. Van Tassel

2008-01-01

371

Self-organising multilayer topographic mappings  

Microsoft Academic Search

Minimization of distortion measures requires multilayer mappings to be topographic. The author shows this only for tree-like multilayer networks. He also shows how to modify the original topographic mapping learning algorithm to increase its convergence rate. A three-layer network can form linelike feature detectors which are just as good as those in a two-layer network. However, the author finds it

S. P. Luttrell

1988-01-01

372

High-efficiency multilayer dielectric diffraction gratings  

SciTech Connect

The design and performance of a new type of high-efficiency diffraction grating for use in either transmission or reflection are described. The gratings are produced in a multilayer dielectric coating deposited upon optically flat substrates. By proper design of the multilayer stack and grating structure, a diffraction efficiency in excess of 96% for polarized light in the {ital m}={minus}1 order in reflection has been achieved.

Perry, M.D.; Boyd, R.D.; Britten, J.A.; Decker, D.; Shore, B.W. [Lawrence Livermore National Laboratory, P.O. Box 808, L-493, Livermore, California 94550 (United States); Shannon, C.; Shults, E. [Hughes Electro-Optic Systems, 2000 East El Segundo Boulevard, El Segundo, California 90245 (United States)

1995-04-15

373

Multichannel bandpass filters utilizing multilayer photonic crystal.  

PubMed

We demonstrate multichannel optical bandpass filters utilizing alternating dielectric multilayers stacked on a patterned substrate. A microstructured Si/SiO(2) multilayer was formed by rf biased magnetron sputtering process on a fused silica substrate with surface gratings. The bandwidths of each filter channel were measured to be 50~175 nm in the near infrared region. Control of center wavelength and bandwidth by the grating pitch was verified. PMID:23595443

Ohtera, Yasuo; Yamada, Hirohito

2013-04-15

374

Polyimide-glass multilayer printed wiring boards  

NASA Astrophysics Data System (ADS)

Multilayer printed wiring boards (PWBs) from a polyimide/glass reinforced copper clad laminate and prepreg were manufactured. A lamination cycle and innerlayer copper surface treatment that gave satisfactory delamination resistance at soldering temperatures were developed. When compared to similar epoxy/glass multilayer PWBs, the polyimide PWBs had higher thermal stability, greater resistance to raised lands, fewer plating voids, less outgassing, and adhesion that was equivalent to urethane foam encapsulants.

Lula, J. W.

1984-07-01

375

PREFACE: Superconductivity in ultrathin films and nanoscale systems Superconductivity in ultrathin films and nanoscale systems  

NASA Astrophysics Data System (ADS)

The recent technological developments in the synthesis and characterization of high-quality nanostructures and developments in the theoretical techniques needed to model these materials, have motivated this focus section of Superconductor Science and Technology. Another motivation is the compelling evidence that all new superconducting materials, such as iron pnictides and chalcogenides, diborides (doped MgB2) and fullerides (alkali-doped C60 compounds), are heterostrucures at the atomic limit, such as the cuprates made of stacks of nanoscale superconducting layers intercalated by different atomic layers with nanoscale periodicity. Recently a great amount of interest has been shown in the role of lattice nano-architecture in controlling the fine details of Fermi surface topology. The experimental and theoretical study of superconductivity in the nanoscale started in the early 1960s, shortly after the discovery of the BCS theory. Thereafter there has been rapid progress both in experiments and the theoretical understanding of nanoscale superconductors. Experimentally, thin films, granular films, nanowires, nanotubes and single nanoparticles have all been explored. New quantum effects appear in the nanoscale related to multi-component condensates. Advances in the understanding of shape resonances or Fano resonances close to 2.5 Lifshitz transitions near a band edge in nanowires, 2D films and superlattices [1, 2] of these nanosized modules, provide the possibility of manipulating new quantum electronic states. Parity effects and shell effects in single, isolated nanoparticles have been reported by several groups. Theoretically, newer techniques based on solving Richardson's equation (an exact theory incorporating finite size effects to the BCS theory) numerically by path integral methods or solving the entire Bogoliubov-de Gennes equation in these limits have been attempted, which has improved our understanding of the mechanism of superconductivity in these confined systems. In addition, the role of thermodynamic fluctuations on superconducting properties has been extensively studied in the context of nanoparticles and nanowires both experimentally and theoretically. In the past decade, a lot of work has been initiated in the area of interface superconductivity where different techniques have been demonstrated to tune Tc. Although the progress in this field has deepened our understanding of nanoscale superconductors, there are several open and key questions which need to be addressed. Some of these are: (1) can superconductivity be enhanced and Tc increased in nanostructures with respect to the bulk limit and if so, how can it be controlled? (2) What are the theoretical and experimental limits for the enhancement and control of superconductivity? (3) Can the phenomena identified in conventional nanostructures shed light on phenomena in high Tc superconductors and vice versa? (4) How will the new fundamental physics of superconductivity at the nanoscale promote advances in nanotechnology applications and vice versa? The papers in this focus section reflect the advances made in this field, in particular in nanowires and nanofilms, but also attempt to answer some of the key open questions outlined above. The theoretical papers explore unconventional quantum phenomena such as the role of confinement in the dynamics of single Cooper pairs in isolated grains [1] and Fano resonances in superconducting gaps in multi-condensate superconductors near a 2.5 Lifshitz transition [2]. Here a new emerging class of quantum phenomena of fundamental physics appear at the Bose-BCS crossover in multi-condensate superconductors [2]. Nanosize effects can now be manipulated by controlling defects in layered oxides [3]. A new approach is provided by controlling the self-organization of oxygen interstitials in layered copper oxides that show an intrinsic nanoscale phase separation [4]. In this case a non-trivial distribution of superconducting nanograins appears to enhance the critical temperature [4]. This is a hot topic as in the past year many wo

Bianconi, Antonio; Bose, Sangita; Garcia-Garcia, Antonio Miguel

2012-12-01

376

Fine tuning of activity for nanoscale catalysts.  

SciTech Connect

Ability to tune the electronic and structural properties of nanocatalysts can potentially lead towards the superior catalytic enhancement that was reported for the Pt{sub 3}Ni(111)-skin surface. Here we report investigation of the extended well-defined surfaces of Pt and PtM alloys (M=Ni,Co,Fe,V,Ti,Re) as well as Pt(hkl) single crystalline surfaces for various catalytic reaction. The electrode surfaces were initially characterized in ultra-high vacuum by AES, LEIS and UPS before controlled transfer into electrochemical environment. Catalytic properties have been determined in three compartment electrochemical cell for oxygen reduction reaction (ORR) by rotational disk electrode technique. The single crystalline surfaces of Pt electrodes have been used to benchmark the activity range that could be expected on pure Pt electrodes. We have proposed that surface modifications induced by the second metal, and consequent catalytic enhancements could occur through the following effects: (1) Electronic effect, due to changes in the metallic d-band center position vs. Fermi level; and (2) Structural effect, which reflects relationship between atomic geometry, and/or surface chemistry, i.e., dissolution - surface roughening. It has been reported that Pt bimetallic alloys, could form surfaces with two different compositions. Due to surface segregation annealed surfaces can form the outermost Pt-skin surface layer, while the lightly sputtered surfaces have the bulk ratio of alloying components and form Pt-skeleton outermost layers as a result of dissolution of non-precious atoms. In principle, different near-surface compositions (Pt-skin, Pt-skeleton and polycrystalline Pt) have been found to have different electronic structures. Modification in Pt electronic properties alters adsorption/catalytic properties of corresponding materials. The most active systems for the electrochemical oxygen reduction reaction (ORR) are established to be the Pt-skin near-surface formation. The similar levels of catalytic enhancement have been established for corresponding nanoscale materials. In addition to electronic properties we have found how catalytic activity could be affected by the arrangement of surface defects on nanoscale surfaces. Ability to control surface and near surface catalyst properties enables fine tuning of catalytic activity and stability of nanoscale surfaces.

Strmcnik, D.; van derVliet, D.; Lucas, C.; Karapetrov, G.; Markovic, N.; Stamenkovic, V.; Materials Science Division

2008-01-01

377

Thermal spreading properties of nanoscale diamond tips on diamond\\/Si  

Microsoft Academic Search

A diamond heat spreader made of nanoscale diamond tips on a diamond\\/Si substrate has been fabricated by planar microwave plasma enhanced chemical vapor deposition. The nanoscale diamond tips are in a conelike shape, which are ~1 µm in height and their average diameter at the bottom is ~200 nm. The nanoscale diamond tips act as a nanoscale “fin structure”, which provide extended

M. Y. Chen; Y. K. Chih; J. Hwang; C. S. Kou; M. T. Chang; L. J. Chou

2008-01-01

378

Transformation of chlorinated methanes by nanoscale iron particles  

SciTech Connect

This paper examines the potential of using laboratory-synthesized nanoscale iron particles to transform chlorinated methanes. The iron particles have diameters on the order of 1--100 nm. Palladized iron particles were prepared by depositing palladium on the surface of iron. Batch experiments were conducted to compare reactions of chlorinated methanes with palladized nanoscale iron, nanoscale iron, and commercial grade iron particles. Rapid transformations of tetrachloromethane (CT) and trichloromethane (CF) were achieved with the palladized nanoscale iron particles. Typically 0.1 mM CT or CF was reduced below detection limits within 1 h. Methane and dichloromethane (DCM) were the major end products. Yields of methane and DCM from CT were 52% and 23%, respectively. Little degradation of DCM was observed within 72 h. With the nanoscale iron and commercial-grade iron particles, much slower reactions of chlorinated methanes were observed. Kinetic analyses indicated that the surface area-normalized rate coefficients k{sub SA} of the nanoscale iron and commercial grade iron particles were one to two orders of magnitude lower than those of the palladized nanoscale iron.

Lien, H.L.; Zhang, W.X.

1999-11-01

379

Magnetotransport and magnetization reversal of electrodeposited multilayer nanowires  

NASA Astrophysics Data System (ADS)

Electrodeposited magnetic multilayer nanowires are ideal materials to study nanoscale magnetism and the giant magnetoresistance (GMR) in the current-perpendicular-to-plane (CPP) geometry. This is because the diameter of each nanowire is uniform, the surface of the nanowire is smooth, and the thickness of both the magnetic and non-magnetic layers can be varied to either larger or smaller than the spin diffusion length which is an important parameter in magnetotransport study. In addition, the aspect ratio (layer-thickness/diameter) that is related to shape anisotropy can be varied for magnetization reversal study. There has been little understanding in the magnetization reversal mechanism of multilayer nanowires, which is complicated due to the dipolar interactions between magnetic layers in each nanowire and between nanowires. The objective of this work is to study the magnetization reversal mechanism of multilayer nanowires using a vibrating sample magnetometer (VSM), where various dipolar interactions are taken into account. Although multilayer nanowires are ideal for the study of the CPP-GMR effect, there remains technical difficulty in making an electrical contact with individual nanowires for the CPP-GMR measurements. In this work, a point-contact method using a conductive plunger tip was developed in-house, that enabled us to measure the CPP-GMR of selected multilayer nanowires in an array of vertically aligned nanowires in each sample. To examine the CPP-GMR and compare the results with theoretical models, the CPP-GMR data were systematically obtained from samples with various magnetic and non-magnetic layer thicknesses. It was found from VSM measurement that the magnetization reversal mode in electrodeposited CoNi/Cu multilayer nanowires depends on the shape and thickness of the CoNi layers where the mode in rod-shaped thick CoNi layers is different from that in disk-shaped thin CoNi layers. The reversal mode in coherent rotation or curling was determined by measuring the magnetic hysteresis loops under various directions of applied magnetic field, particularly comparing the measured coercivity data with those obtained from theoretical models. It was found that there is a transition for the magnetization reversal mode in rod-shaped CoNi layers from coherent rotation to curling with increasing angle between the field direction and the nanowires, while the reversal mode is of coherent rotation type for disk-shaped CoNi layers. When the thickness of the CoNi layers decreases to very thin regime, the layers eventually become discontinuous and form discrete islands that exhibit superparamagnetism. The layer thickness dependence of CPP-GMR was measured for CoNi/Cu multilayer nanowires and compared with the Valet-Fert model. There are both agreement and deviation between the experimental results and theoretical prediction. When both the Cu layer thickness tCu and CoNi layer thickness tCoNi are much smaller than the spin diffusion length l of the corresponding material, i.e. tCu<< lCu and tCoNi<< lCoNi, ( DeltaR/RAP)-1/2 varies linearly with tCu, where RAP and RP are the maximum resistance attained in the GMR measurement and the resistance at saturation under higher fields, and DeltaR is the difference between RAP and RP. The obtained result is in agreement with the Valet-Fert (V-F) model. It was also found that when t Cu<< lCu and 170 nm>> tCoNi>>lCoNi, (DeltaR/R P)-1 is proportional to tCoNi , in agreement with the V-F model. Analysis of the CPP-GMR parameters shows that the interfacial spin asymmetry coefficient gamma is much larger than the bulk spin asymmetry coefficient beta, indicating that the interfacial scattering is important for the CPP-GMR. However, there is a discrepancy between the experimental data and the V-F model when tCoNi is very small, probably due to formation of thin and discontinuous magnetic layers that exhibit superparamagnetism. There is also a disagreement between the experimental data and the model for tCoNi >170 nm, where the anisotropic magnetore

Tang, Xueti

380

Characterization of superconducting nanometric multilayer samples for superconducting rf applications: First evidence of magnetic screening effect  

NASA Astrophysics Data System (ADS)

The best rf bulk niobium accelerating cavities have nearly reached their ultimate limits at rf equatorial magnetic field H?200mT close to the thermodynamic critical field Hc. In 2006 Gurevich proposed to use nanoscale layers of superconducting materials with high values of Hc>HcNb for magnetic shielding of bulk niobium to increase the breakdown magnetic field of superconducting rf cavities. Depositing good quality layers inside a whole cavity is rather difficult, so as a first step, characterization of single layer coating and multilayers was conducted on high quality sputtered samples by applying the technique used for the preparation of superconducting electronics circuits. The samples were characterized by x-ray reflectivity, dc resistivity (PPMS), and dc magnetization (SQUID) measurements. Dc magnetization curves of a 250 nm thick Nb film have been measured, with and without a magnetron sputtered coating of a single or multiple stack of 15 nm MgO and 25 nm NbN layers. The Nb samples with/without the coating exhibit different behaviors and clearly show an enhancement of the magnetic penetration field. Because SQUID measurements are influenced by edge and shape effects, we propose to develop a specific local magnetic measurement of HC1 based on ac third harmonic analysis in order to reveal the true screening effect of multilayers.

Antoine, C. Z.; Berry, S.; Bouat, S.; Jacquot, J.-F.; Villegier, J.-C.; Lamura, G.; Gurevich, A.

2010-12-01

381

A manual nanoscale method for protein crystallization.  

PubMed

To overcome one of the major hurdles in three-dimensional crystal structure determination - the requirement for large quantities of purified material to grow crystals - crystallization methodologies have been developed that require only a total of 2-5 microl of a concentrated macromolecular solution to screen more than 100 conditions. These procedures employ a circular slide containing an array of 25 wells designed for crystallization setups in the nanolitre volume range. These 'crystallization slides' fit into the wells of standard crystallization trays. These nanoscale crystallization approaches have been used to reproducibly obtain well diffracting crystals of three proteins, two that are being actively studied (glycerol kinase and NADH peroxidase) and one test protein (lysozyme), using only 40-350 microg (0.04-0.35 mg) of proteins to screen 100 conditions. These nanolitre crystallization methods are easily adapted for the typical laboratory, without the requirement of robotics or expensive equipment. PMID:12876342

Yeh, Joanne I

2003-07-23

382

Preface: Charge transport in nanoscale junctions  

NASA Astrophysics Data System (ADS)

Understanding the fundamentals of nanoscale charge transfer is pivotal for designing future nano-electronic devices. Such devices could be based on individual or groups of molecular bridges, nanotubes, nanoparticles, biomolecules and other 'active' components, mimicking wire, diode and transistor functions. These have operated in various environments including vacuum, air and condensed matter, in two- or three-electrode configurations, at ultra-low and room temperatures. Interest in charge transport in ultra-small device components has a long history and can be dated back to Aviram and Ratner's letter in 1974 (Chem. Phys. Lett. 29 277-83). So why is there a necessity for a special issue on this subject? The area has reached some degree of maturity, and even subtle geometric effects in the nanojunction and noise features can now be resolved and rationalized based on existing theoretical concepts. One purpose of this special issue is thus to showcase various aspects of nanoscale and single-molecule charge transport from experimental and theoretical perspectives. The main principles have 'crystallized' in our minds, but there is still a long way to go before true single-molecule electronics can be implemented. Major obstacles include the stability of electronic nanojunctions, reliable operation at room temperature, speed of operation and, last but not least, integration into large networks. A gradual transition from traditional silicon-based electronics to devices involving a single (or a few) molecule(s) therefore appears to be more viable from technologic and economic perspectives than a 'quantum leap'. As research in this area progresses, new applications emerge, e.g. with a view to characterizing interfacial charge transfer at the single-molecule level in general. For example, electrochemical experiments with individual enzyme molecules demonstrate that catalytic processes can be studied with nanometre resolution, offering a route towards optimizing biosensors at the molecular level. Nanoscale charge transport experiments in ionic liquids extend the field to high temperatures and to systems with intriguing interfacial potential distributions. Other directions may include dye-sensitized solar cells, new sensor applications and diagnostic tools for the study of surface-bound single molecules. Another motivation for this special issue is thus to highlight activities across different research communities with nanoscale charge transport as a common denominator. This special issue gathers 27 articles by scientists from the United States, Germany, the UK, Denmark, Russia, France, Israel, Canada, Australia, Sweden, Switzerland, the Netherlands, Belgium and Singapore; it gives us a flavour of the current state-of-the-art of this diverse research area. While based on contributions from many renowned groups and institutions, it obviously cannot claim to represent all groups active in this very broad area. Moreover, a number of world-leading groups were unable to take part in this project within the allocated time limit. Nevertheless, we regard the current selection of papers to be representative enough for the reader to draw their own conclusions about the current status of the field. Each paper is original and has its own merit, as all papers in Journal of Physics: Condensed Matter special issues are subjected to the same scrutiny as regular contributions. The Guest Editors have deliberately not defined the specific subjects covered in this issue. These came out logically from the development of this area, for example: 'Traditional' solid state nanojunctions based on adsorbed layers, oxide films or nanowires sandwiched between two electrodes: effects of molecular structure (aromaticity, anchoring groups), symmetry, orientation, dynamics (noise patterns) and current-induced heating. Various 'physical effects': inelastic tunnelling and Coulomb blockade, polaron effects, switching modes, and negative differential resistance; the role of many particle excitations, new surface states in semiconductor electrodes, various mechanisms for

Albrecht, Tim; Kornyshev, Alexei; Bjørnholm, Thomas

2008-09-01

383

Self-healing at the nanoscale.  

PubMed

The design of self-healing materials is a very important but challenging topic in nanotechnology. Self-healing strategies, also inspired by natural processes, allow the fabrication of auto-repairing systems, and in recent years, materials engineering at the nanoscale has allowed further advances in this emerging field. In this mini review, we recall some interesting self-healing systems found in natural processes and others created by man-made activity with special emphasis on the role played in this field by nanostructures. Finally, the self-healing of gold nanoparticles during laser irradiation is considered in more detail since it is a rare example of a functional nanomaterial with self-repairing properties. PMID:20644863

Amendola, Vincenzo; Meneghetti, Moreno

2009-08-28

384

Nanoscale free-standing magnetoelectric heteropillars.  

PubMed

Nanocomposites with a film-on-substrate geometry usually suffer from a large clamping effect from the substrate, inhibiting the elastic-interaction-mediated "product" property such as the magnetoelectric response in piezoelectric-magnetostrictive systems. Here we report a self-assembling strategy to synthesize nanoscaled free-standing magnetoelectric heteropillars. The degree of clamping from the substrate has been greatly reduced, which is manifested by enhanced piezoelectricity and isotropic magnetic behaviors. A combination of techniques such as transmission electron microscopy, Raman spectroscopy and X-ray diffraction provide additional evidence of stress release in the as-prepared nanocomposite. Moreover, as a benefit of this unconstrained structure, we are able to observe a large magnetic-field-induced polarization change of up to 11.5% at room temperature, demonstrating its potential application in future magnetoelectronic devices at the nanoscale. PMID:23812091

Zhang, Jinxing; Fu, Houren; Lu, Wei; Dai, Jiyan; Chan, H L W

2013-08-01

385

Reduction of Thermal Conductivity by Nanoscale 3D Phononic Crystal  

PubMed Central

We studied how the period length and the mass ratio affect the thermal conductivity of isotopic nanoscale three-dimensional (3D) phononic crystal of Si. Simulation results by equilibrium molecular dynamics show isotopic nanoscale 3D phononic crystals can significantly reduce the thermal conductivity of bulk Si at high temperature (1000?K), which leads to a larger ZT than unity. The thermal conductivity decreases as the period length and mass ratio increases. The phonon dispersion curves show an obvious decrease of group velocities in 3D phononic crystals. The phonon's localization and band gap is also clearly observed in spectra of normalized inverse participation ratio in nanoscale 3D phononic crystal.

Yang, Lina; Yang, Nuo; Li, Baowen

2013-01-01

386

Nanoscale quantum dynamics and electrostatic coupling  

NASA Astrophysics Data System (ADS)

Physical nanoscale systems have been analyzed both from an electrostatic point of view and quantum mechanically with respect to quantum computation. We introduce an elaborate code for the efficient numerical simulation of nanoscale electrostatics via a higher-order relaxation algorithm with a large variety of boundary conditions which then is applied to a set of physically relevant problems. Great emphasis is put on screening effects as well as capacitive coupling between spatially separated conducting regions. Specifically, we analyze the depletion of a two-dimensional electron gas using different methods. The effect of surface charges due to the pinning of the Fermi level at a semiconductor surface is shown to play an important role in that it can shift the whole system characteristics, underlining the importance of chemical potentials and work functions. The capacitive coupling is further used to model the interactions in an interacting network of quantum dots, and the use of the capacitance formalism in the quantum mechanical context is explicitly justified. Quantum dot arrays are then analyzed on a general footing with respect to quantum computation and charge qubits based on an extended Hubbard Hamiltonian model. For systems with at most two operative electrons, general restrictions apply, introducing certain constraints on what realizations of this type of charge qubit may eventually look like. Furthermore, the interaction of the macroscopic world with the quantum dot network via quantum gates is discussed. Again, general arguments allow us to rule out certain scenarios of quantum gates. For example it turns out that capacitive coupling alone is not sufficient for full single qubit operation. Alternative ways are discussed, and finally, by using an external magnetic field and its resulting Aharonov-Bohm phases on the array, full single qubit operation based on charge is demonstrated.

Weichselbaum, Andreas

387

Synthetic nano-scale fibrous extracellular matrix.  

PubMed

Biodegradable polymers have been widely used as scaffolding materials to regenerate new tissues. To mimic natural extracellular matrix architecture, a novel highly porous structure, which is a three-dimensional interconnected fibrous network with a fiber diameter ranging from 50 to 500 nm, has been created from biodegradable aliphatic polyesters in this work. A porosity as high as 98.5% has been achieved. These nano-fibrous matrices were prepared from the polymer solutions by a procedure involving thermally induced gelation, solvent exchange, and freeze-drying. The effects of polymer concentration, thermal annealing, solvent exchange, and freezing temperature before freeze-drying on the nano-scale structures were studied. In general, at a high gelation temperature, a platelet-like structure was formed. At a low gelation temperature, the nano-fibrous structure was formed. Under the conditions for nano-fibrous matrix formation, the average fiber diameter (160-170 nm) did not change statistically with polymer concentration or gelation temperature. The porosity decreased with polymer concentration. The mechanical properties (Young's modulus and tensile strength) increased with polymer concentration. A surface-to-volume ratio of the nano-fibrous matrices was two to three orders of magnitude higher than those of fibrous nonwoven fabrics fabricated with the textile technology or foams fabricated with a particulate-leaching technique. This synthetic analogue of natural extracellular matrix combined the advantages of synthetic biodegradable polymers and the nano-scale architecture of extracellular matrix, and may provide a better environment for cell attachment and function. PMID:10357136

Ma, P X; Zhang, R

1999-07-01

388

Nanoscale phase separation in coated Ag nanoparticles  

NASA Astrophysics Data System (ADS)

In this paper we report the structural investigation of cysteine and glutathione capped Ag nanoparticles (NPs) by means of transmission electron microscopy (TEM), synchrotron X-ray diffraction (XRD) and pair distribution function (PDF) analysis. The combined use of these probes allowed us to observe the presence of two crystal structures in the coated AgNPs, i.e., the cubic and the hexagonal crystal structures of Ag. In particular, it was possible to demonstrate that the coated AgNPs are a nanoscale phase separated system where the two phases coexist within the single grain. In addition, the relative bulk amount of the fcc and hcp phases has been estimated and a possible correlation with the capping agent proposed.In this paper we report the structural investigation of cysteine and glutathione capped Ag nanoparticles (NPs) by means of transmission electron microscopy (TEM), synchrotron X-ray diffraction (XRD) and pair distribution function (PDF) analysis. The combined use of these probes allowed us to observe the presence of two crystal structures in the coated AgNPs, i.e., the cubic and the hexagonal crystal structures of Ag. In particular, it was possible to demonstrate that the coated AgNPs are a nanoscale phase separated system where the two phases coexist within the single grain. In addition, the relative bulk amount of the fcc and hcp phases has been estimated and a possible correlation with the capping agent proposed. Electronic supplementary information (ESI) available. See DOI: 10.1039/c1nr10832h

Diaz-Fernandez, Yuri Antonio; Pallavicini, Piersandro; Pasotti, Luca; Milanese, Chiara; Pellicer, Eva; Baró, Maria D.; Ren, Yang; Malavasi, Lorenzo

2011-10-01

389

Layer-by-layer assembly of {nanoclay-(sol-gel oxide)}n and {nanoclay-(oxide nanoparticle)}n multilayers: Synthesis and growth mechanisms  

NASA Astrophysics Data System (ADS)

Two new classes of all-inorganic nanostructured multilayers, {MMT x-(sol-gel oxide)}n and {MMTx-(oxide nanoparticle)} n, have been successfully synthesized for the first time. They were made by adapting a layer-by-layer (LbL) assembly method initially developed to synthesize polyelectrolyte-based multilayers. In most previous studies, this electrostatic-assisted LbL assembly method used polyelectrolytes/polymers as the "structural glue" to prepare multilayers. The synthesis of {MMTx-(sol-gel ZrO2)}n multilayers demonstrates for the first time the feasibility of making sol-gel oxide "glued" all-inorganic multilayers, thereby introducing an innovative nanoscale fabrication concept. The synthesis of {MMTx-(oxide nanoparticle)}n multilayers further illustrates the versatility of LbL assembly technique by achieving a second new type of all-inorganic multilayers with a novel "plate-ball" architecture. The feasibility of synthesizing other types of multilayer structures, including {MMTx-(ionic liquid)}n, {(carbon nanotube)-(sol-gel ZrO2)}n, and {polymer-(sol-gel ZrO2)} n, were also explored. Systematical investigations of the growth kinetics of {MMTx-(sol-gel ZrO2)}n multilayers reveal unique underlying mechanisms for electrostatic-assisted growth of sol-gel films and LbL assembly. The growth of the MMT and sol-gel ZrO2 layers is strongly coupled. For fresh aqueous ZrO2 precursors, the growth rates of sol-gel ZrO2 layers on MMT surfaces as functions of time and precursor concentration do not follow the standard mass transfer or interfacial reaction controlled kinetic models. Furthermore, the growth of the sol-gel oxide layers on MMT surfaces is self-limited to a maximum thickness of ˜50-60 nm. These observations suggest a surface-mediated growth of sol-gel 'oxide layers on MMT surfaces, one that is likely controlled by electrostatic interactions. These new findings significantly advance the general understanding of the LbL electrostatic assembly process. For the aged precursors, the growth mechanism differs; the growth of sol-gel oxide layers is controlled by hydrodynamics and follows the Landau-Levich model. For as-deposited multilayers, isothermal annealing at ˜400°C dehydrates them and removes the residue acetate groups without damaging the MMT nanoplatelets and the ordered layer structures. Nanomechanical measurements show that the elastic modulus of the multilayers can be intentionally tuned by changing the multilayer design and that significant porosity is present in the multilayers even after annealing. In addition, free-standing multilayers are successfully made via using sacrificial substrates, and the newly developed methodology for {MMTx-(sol-gel oxide)} n can be extended, using other metal oxides, e.g., SnO2, as the inorganic "glue." Potential applications of these new nanostructured multilayers are discussed.

Chen, Hao

390

Spin wave resonance and relaxation in microwave magnetic multilayer structures and devices  

NASA Astrophysics Data System (ADS)

The continuous and increasing demand for higher frequency magnetic microwave structures triggered a tremendous development in the field of magnetization dynamics over the past decade. In order to develop smaller and faster devices, more efforts are required to achieve a better understanding of the complex magnetization precessional dynamics, the magnetization anisotropy, and the sources of spin scattering at the nanoscale. This thesis presents measurements of magnetic precession and relaxation dynamics in multilayer ferromagnetic films of CoFe/PtMn/CoFe in both frequency and time domain. First, we conducted the ferromagnetic resonance (FMR) measurements for samples with the ferromagnetic CoFe layer thicknesses varying from 10 A to 500 A. The magnetic anisotropic parameters were determined by rotating the field aligned axis with respect to the spectral field in the configurations of both in-plane and out-of-plane. Moreover, we identified a high-order standing spin wave in our spectra and found a "critical angle" in the multilayer samples. We included an effective surface anisotropy field to describe our results. This allows us to determine the exchange interaction stiffness in the CoFe layers. Next, we performed pump-probe Magneto-Optical Kerr Effect experiments in the multilayer films. Three precession modes were observed in the Voigt geometry. The modes are assigned to the exchange-dominated spin wave excitations and the non-homogeneous dipole mode. We developed a comprehensive model of the magnetic eigenmodes and their coupling to light to gain accurate values of the exchange, bulk and surface anisotropy constants. The results are consistent with those from the FMR measurements. Finally, the measured resonance linewidths of CoFe/PtMn/CoFe films were analyzed by the thickness dependence of the CoFe layers. We discussed the contribution of the Gilbert damping, two magnon scattering, as well as surface and interface to the FMR linewidth and concluded the two magnon scattering plays the most important role in FMR linewidth broadening and reaffirmed the significance of surface effects for spin wave damping in these samples. The results of this thesis will lead to new insights into important magnetic properties of ferromagnetic films and therefore provide essential knowledge for optimizing the GHz response of the nanoscale magnetic elements and devices.

Wu, Cheng

391

Encapsulated tips for reliable nanoscale conduction in scanning probe technologies  

NASA Astrophysics Data System (ADS)

Nanoscale tip apexes of conducting cantilever probes are important enablers for several conducting probe technologies that require reliable long-term operation, while preserving the nanoscale integrity of the tip apex. In this paper, the concept of an encapsulated tip with a nanoscale conducting core is presented. A method to fabricate such tips on conducting silicon microcantilevers is described. Long-term conduction and wear reliability of these nanoscale tips are evaluated systematically, and their ability to operate for sliding distances greater than 2 m in conduction and 11 m in wear on amorphous carbon is demonstrated. These results are expected to have an impact on the future of conducting probe-based technologies such as probe-based nanometrology, data storage and nanolithography.

Bhaskaran, Harish; Sebastian, Abu; Drechsler, Ute; Despont, Michel

2009-03-01

392

Characterization, Processing, and Consolidation of Nanoscale Tungsten Powder.  

National Technical Information Service (NTIS)

Nanoscale tungsten powder was consolidated by the Plasma Pressure Compaction (P2C) method. The starting powder was first characterized to determine particle size, morphology, and presence of chemical impurities. The characterization data led to efforts to...

B. R. Klotz E. M. Klier F. R. Kellogg K. C. Cho R. J. Dowding

2009-01-01

393

Nanoscale Hard X-Ray Microscopy Methods for Materials Studies  

NASA Astrophysics Data System (ADS)

This review discusses recent progress in the development of hard X-ray microscopy techniques for materials characterization at the nanoscale. Although the utility of traditionally ensemble-based X-ray techniques in materials research has been widely recognized, the utility of X-ray techniques as a tool for local characterization of nanoscale materials properties has undergone rapid development in recent years. Owing to a confluence of improvements in synchrotron source brightness, focusing optics fabrication, detection, and data analysis, nanoscale X-ray imaging techniques have moved beyond proof-of-principle experiments to play a central role in synchrotron user programs worldwide with high-impact applications made to materials science questions. Here, we review the current state of synchrotron-based, hard X-ray nanoscale microscopy techniques-including 3D tomographic visualization, spectroscopic elemental and chemical mapping, microdiffraction-based structural analysis, and coherent methods for nanomaterials imaging-with particular emphasis on applications to materials research.

Holt, Martin; Harder, Ross; Winarski, Robert; Rose, Volker

2013-07-01

394

Cluster Dynamics: Laying the Foundations for Developing Nanoscale Materials.  

National Technical Information Service (NTIS)

The program which ended December 31, 2006 was directed towards: 1) developing approaches for the design of new nanoscale materials that can be tailored to have desired properties; 2) investigating electronic and reactive properties that will find applicat...

J. A. Castleman

2006-01-01

395

Neural Assembly Models Derived through Nano-Scale Measurements.  

National Technical Information Service (NTIS)

This report summarizes accomplishments of a three-year project focused on developing technical capabilities for measuring and modeling neuronal processes at the nanoscale. It was successfully demonstrated that nanoprobes could be engineered that were bioc...

C. Branda C. Warrender H. Fan J. C. Forsythe R. L. Schiek

2009-01-01

396

COST 288: Nanoscale and Ultrafast Photonics. Action Identification Data.  

National Technical Information Service (NTIS)

This is the final report of the Management Committee Meeting, COST (European Cooperation in the Field of Scientific and Technical Research) 288, Nanoscale and Ultrafast Photonics. The original aim of the action was to investigate sub-wavelength scale feat...

2008-01-01

397

Nanomaterial Case Study: Nanoscale Silver in Disinfectant Spray.  

National Technical Information Service (NTIS)

Nanoscale materials (nanomaterials) have been described as having at least one dimension on the order of approximately 1100 nanometers (nm) (NSTC, 2011). Although this size range is not universally accepted and continues to evolve, 100 nm is typically use...

2012-01-01

398

Moisture in multilayer ceramic capacitors  

NASA Astrophysics Data System (ADS)

When both precious metal electrode and base metal electrode (BME) capacitors were subjected to autoclave (120°C/100% RH) testing, it was found that the precious metal capacitors aged according to a well known aging mechanism (less than 3% from their starting values), but the BME capacitors degraded to below the -30% criterion at 500 hours of exposure. The reasons for this new failure mechanism are complex, and there were two theories that were hypothesized. The first was that there could be oxidation or corrosion of the nickel plates. The other hypothesis was that the loss of capacitance was due to molecular changes in the barium titanate. This thesis presents the evaluation of these hypotheses and the physics of the degradation mechanism. It is concluded by proof by elimination that there are molecular changes in the barium titanate. Furthermore, the continuous reduction in capacitor size makes the newer base metal electrode capacitors more vulnerable to moisture degradation than the older generation precious metal capacitors. In addition, standard humidity life testing, such as JESD-22 THB and HAST, will likely not uncover this problem. Therefore, poor reliability due to degradation of base metal electrode multilayer ceramic capacitors may catch manufacturers and consumers by surprise.

Donahoe, Daniel Noel

399

Ion-Irradiated Laterally Graded Ni/C Multilayers: A Combined X-ray Standing Wave and X-ray Reflectivity Analysis  

NASA Astrophysics Data System (ADS)

An X-ray standing wave (XSW) experimental facility was set up at the Rossendorf Beam Line (ROBL) at the European Synchrotron Radiation Facility (ESRF). Using this facility, the microstructures and ion-beam induced microstructural modifications of a nanoscale laterally graded Ni/C multilayer systems have been studied by the combined X-ray reflectivity (XRR) and XSW technique. The multilayer stack with 15 Ni/C layer pairs was fabricated on a glass substrate by ion beam sputtering. A 2 MeV Cu2+ ion beam was rastered on the samples to obtain uniformly irradiated strips with fluences from 1× 1014 to 7× 1014 ions/cm2. We have observed that X-ray reflectivity at the first order Bragg peak gradually increases due to increase in multilayer period in the virgin samples. The multilayer period has expanded and interfaces broadened due to ion irradiation. X-ray standing wave analysis indicates that, during deposition, a significant amount of Ni diffuses into C layers. Up to a certain fluence, we have observed that more and more Ni atoms are incorporated into C layers. At higher fluences, Ni is progressively segregated from the C layers. These mixing and demixing phenomena of Ni in C layers as a function of ion fluence have been explained in terms of two competitive processes including ballistic mixing and chemically guided atomic movements.

Dev, Bhupendra Nath; Roy, Sumalay; Bera, Sambhunath; Tawara, Yuzuru; Schell, Norbert; Grenzer, Jörg; Borany, Johannes von; Grötzschel, Rainer

2011-05-01

400

Nanoscale control of thermal transport via SiGe quantum dots  

NASA Astrophysics Data System (ADS)

A study of cross plane thermal transport in SiGe/Si quantum dot multilayers (QD ML) is presented. Recent advances in heteroepitaxial growth allowed the fabrication of nanostructures, initiating intriguing investigations into low dimensional physics. Previous reports on thermal transport demonstrated that nanostructuring can reduce the thermal conductivity of a material even below the amorphous limit. Yet, the fundamental reasons why nanostructuring reduces thermal conductivity in crystalline materials are not fully understood. In this work we investigate cross-plane thermal transport through SiGe QD ML grown by means of MBE on Si. Measurements of the thermal properties were carried out along with a detailed AFM, TEM and x-ray characterization. Our findings demonstrate that quantum dots provide a means to tailor the thermal conductivity to extremely low values, about 1 W/m K. The highly diffusive interfaces achieved in SiGe/Si systems may be relevant to the development of integrated miniaturized energy harvesting or thermal management devices, in view of the integrability of SiGe in novel nanoscale devices.

Pezzoli, F.; Chen, P.; Stoffel, M.; Deneke, C.; Rastelli, A.; Schmidt, O. G.; Malachias, A.; Jacquot, A.; Pernot, G.; Dilhaire, S.; Savic, I.; Mingo, N.

2010-03-01

401

Layer-dependent nanoscale electrical properties of graphene studied by conductive scanning probe microscopy  

NASA Astrophysics Data System (ADS)

The nanoscale electrical properties of single-layer graphene (SLG), bilayer graphene (BLG) and multilayer graphene (MLG) are studied by scanning capacitance microscopy (SCM) and electrostatic force microscopy (EFM). The quantum capacitance of graphene deduced from SCM results is found to increase with the layer number ( n) at the sample bias of 0 V but decreases with n at -3 V. Furthermore, the quantum capacitance increases very rapidly with the gate voltage for SLG, but this increase is much slowed down when n becomes greater. On the other hand, the magnitude of the EFM phase shift with respect to the SiO2 substrate increases with n at the sample bias of +2 V but decreases with n at -2 V. The difference in both quantum capacitance and EFM phase shift is significant between SLG and BLG but becomes much weaker between MLGs with a different n. The layer-dependent quantum capacitance behaviors of graphene could be attributed to their layer-dependent electronic structure as well as the layer-varied dependence on gate voltage, while the layer-dependent EFM phase shift is caused by not only the layer-dependent surface potential but also the layer-dependent capacitance derivation.

Zhao, Shihua; Lv, Yi; Yang, Xinju

2011-08-01

402

Layer-dependent nanoscale electrical properties of graphene studied by conductive scanning probe microscopy  

PubMed Central

The nanoscale electrical properties of single-layer graphene (SLG), bilayer graphene (BLG) and multilayer graphene (MLG) are studied by scanning capacitance microscopy (SCM) and electrostatic force microscopy (EFM). The quantum capacitance of graphene deduced from SCM results is found to increase with the layer number (n) at the sample bias of 0 V but decreases with n at -3 V. Furthermore, the quantum capacitance increases very rapidly with the gate voltage for SLG, but this increase is much slowed down when n becomes greater. On the other hand, the magnitude of the EFM phase shift with respect to the SiO2 substrate increases with n at the sample bias of +2 V but decreases with n at -2 V. The difference in both quantum capacitance and EFM phase shift is significant between SLG and BLG but becomes much weaker between MLGs with a different n. The layer-dependent quantum capacitance behaviors of graphene could be attributed to their layer-dependent electronic structure as well as the layer-varied dependence on gate voltage, while the layer-dependent EFM phase shift is caused by not only the layer-dependent surface potential but also the layer-dependent capacitance derivation.

2011-01-01

403

Nanoscale Volcanoes: Accretion of Matter at Ion-Sculpted Nanopores  

NASA Astrophysics Data System (ADS)

We demonstrate the formation of nanoscale volcanolike structures induced by ion-beam irradiation of nanoscale pores in freestanding silicon nitride membranes. Accreted matter is delivered to the volcanoes from micrometer distances along the surface. Volcano formation accompanies nanopore shrinking and depends on geometrical factors and the presence of a conducting layer on the membrane’s back surface. We argue that surface electric fields play an important role in accounting for the experimental observations.

Mitsui, Toshiyuki; Stein, Derek; Kim, Young-Rok; Hoogerheide, David; Golovchenko, J. A.

2006-01-01

404

A new method to produce nanoscale iron for nitrate removal  

Microsoft Academic Search

This article proposes a novel technology combining electrochemical and ultrasonic methods to produce nanoscale zero valent iron (NZVI). With platinum placed in the cathode and the presence of the dispersion agent, 0.2g\\/l cetylpyridinium chloride (CPC), a cation surfactant, in the solution, the nanoscale iron particle was successfully produced with diameter of 1–20 nm and specific surface area of 25.4m2\\/g. The

Shiao-Shing Chen; Hong-Der Hsu; Chi-Wang Li

2004-01-01

405

[Development of nano-scale genic carriers in biomedicine].  

PubMed

Nano biotechnology is a developing field of science and technology in the 21st century. The emergence of nanomaterials provides a new way for gene carriers. This paper demonstrates the advantages and types of nano-scale genic carriers and the methods for introducing it into the body, and reviewed the application of nano-scale genic carriers in gene therapy and in breeding. PMID:19558139

Wang, Qiong; Chen, Jie-Nan; Lu, Meng-Zhu; Liu, Bo-Bin

2009-04-01

406

Discrete Kernel Model for Simulation of Multilayered Aquifers.  

National Technical Information Service (NTIS)

The design and development of a special management oriented groundwater model for the simulation of multilayered aquifers are presented. Multilayered aquifers consist of water bearing aquifer layers separated by sufficiently permeable confining layers whi...

T. H. Illangasekare

1985-01-01

407

Advances in Low-Defect Multilayers for EUVL Mask Blanks.  

National Technical Information Service (NTIS)

Low-defect multilayer coatings are required to fabricate mask blanks for Extreme Ultraviolet Lithography (EUVL). The mask blanks consist of high reflectance EUV multilayers on low thermal expansion substrates. A defect density of 0.0025 printable defects/...

J. A. Folta J. C. Davidson C. C. Larson C. C. Walton P. A. Kearney

2002-01-01

408

Nanoscale tissue engineering: spatial control over cell-materials interactions.  

PubMed

Cells interact with the surrounding environment by making tens to hundreds of thousands of nanoscale interactions with extracellular signals and features. The goal of nanoscale tissue engineering is to harness these interactions through nanoscale biomaterials engineering in order to study and direct cellular behavior. Here, we review two- and three-dimensional (2- and 3D) nanoscale tissue engineering technologies, and provide a holistic overview of the field. Techniques that can control the average spacing and clustering of cell adhesion ligands are well established and have been highly successful in describing cell adhesion and migration in 2D. Extension of these engineering tools to 3D biomaterials has created many new hydrogel and nanofiber scaffold technologies that are being used to design in vitro experiments with more physiologically relevant conditions. Researchers are beginning to study complex cell functions in 3D. However, there is a need for biomaterials systems that provide fine control over the nanoscale presentation of bioactive ligands in 3D. Additionally, there is a need for 2- and 3D techniques that can control the nanoscale presentation of multiple bioactive ligands and that can control the temporal changes in the cellular microenvironment. PMID:21451238

Wheeldon, Ian; Farhadi, Arash; Bick, Alexander G; Jabbari, Esmaiel; Khademhosseini, Ali

2011-03-31

409

Multilayer thin film thermoelectrics produced by sputtering  

SciTech Connect

In this work we explore the possibility of achieving bulk electrical properties in single layer sputter deposited films grown epitaxially on (111) oriented BaF{sub 2} substrates. There are a number of sputter deposition parameters that can be varied in order to optimize the film quality. It is important to understand the effect of varying the deposition temperature, Ar sputtering gas pressure, and the substrate bias. We will consider only Bi and Bi{sub 0.86}Sb{sub 0.14} films in this paper. These materials were chosen since they have the same simple structure, two different band gaps and do not change significantly either in physical or electrical properties with small amounts of cross contamination. We will also present our work on multilayer thermoelectrics made of Bi and Bi{sub 0.86}Sb{sub 0.14} layers. There has been considerable interest in this multilayer structure in the literature. Theoretical calculations of the band structure and interface states of these multilayer structures have been made by Mustafaev and Agassi et al. respectively [6,7]. Experimentally Yoshida et al. have examined similar multilayer structures grown by MBE as well as Bi/Sb multilayer samples in which report an anomalous thermoelectric power [8].

Wagner, A.V.; Foreman, R.J.; Summers, L.J.; Barbee, T.W. Jr.; Farmer, J.C.

1995-06-19

410

High-resolution X-ray Multilayers  

SciTech Connect

Two new approaches are taken in multilayer fabrication to help bridge the gap in bandwidth between traditional multilayers (1 to 2%) and perfect crystals (0.01%). The first approach is based on creating many layers of low-contrast Al2O3/ B4C materials. The second approach is based on using multilayer structures with a small d-spacing using traditional W/B4C and Mo/B4C materials. With 8 keV x-rays on the Chess A2 beamline, we measured a bandwidth of 0.27% with a reflectivity of 40% and a Darwin width of 17 arc seconds from a 26 A d-spacing multilayer with 800 bi-layers of Al2O3/B4C using the low-contrast approach. On the other hand, the short period approach with a W/B4C multilayer and a 14.8 A d-spacing showed a resolution of 0.5 % and a reflectivity of 58.5%. Two more Mo/B4C samples with d-spacings of 15 A and 20 A showed energy resolutions of 0.25% and 0.52% with corresponding reflectivities of 39% and 66%. Thus we observe that both methods can produce useful x-ray optical components.

Martynov, V.V.; Platonov, Yu. [Osmic Inc., 1900 Taylor Rd., Auburn Hills, MI 48326 (United States); Kazimirov, A. [CHESS, Wilson Laboratory, Cornell University, Ithaca, NY 14853 (United States); Bilderback, D.H. [CHESS, Wilson Laboratory, Cornell University, Ithaca, NY 14853 (United States); School of Applied and Engineering, Clark Hall, Cornell University, Ithaca, NY 14853 (United States)

2004-05-12

411

Impact of ethylene carbonate on ion transport characteristics of PVdF-AgCF{sub 3}SO{sub 3} polymer electrolyte system  

SciTech Connect

The ionic transport in thin film plasticized polymer electrolytes based on polyvinylidene fluoride (PVdF) as the polymer host, silver triflate (AgCF{sub 3}SO{sub 3}) as salt and ethylene carbonate (EC) as plasticizer prepared by solution casting technique has been reported. Addition of silver triflate has resulted in an increase in the room temperature (298 K) electrical conductivity of the polymer from 10{sup -6} to 10{sup -5} S cm{sup -1} whereas incorporation of EC as the plasticizer has further enhanced the conductivity value by an order of magnitude to 10{sup -4} S cm{sup -1} owing to the possible decrease in crystallinity of the polymer matrix as revealed by the detailed temperature-dependent complex impedance, silver ionic transference number, Fourier transform infrared and X-ray diffraction measurements.

Austin Suthanthiraraj, S.; Joice Sheeba, D., E-mail: jsheebaj@sify.com [Department of Energy, University of Madras, Guindy Campus, Chennai 600025 (India); Joseph Paul, B., E-mail: joe_paul82@yahoo.co.in [Department of Energy, University of Madras, Guindy Campus, Chennai 600025 (India)

2009-07-01

412

Method to adjust multilayer film stress induced deformation of optics  

Microsoft Academic Search

A buffer-layer located between a substrate and a multilayer for counteracting stress in the multilayer is disclosed. Depositing a buffer-layer having a stress of sufficient magnitude and opposite in sign reduces or cancels out deformation in the substrate due to the stress in the multilayer. By providing a buffer-layer between the substrate and the multilayer, a tunable, near-zero net stress

P. B. Mirkarimi; C. Montcalm

2000-01-01

413

Multilayer reflective coatings for extreme-ultraviolet lithography  

Microsoft Academic Search

Multilayer mirror coatings which reflect extreme UV (EUV) radiation are a key enabling technology for EUV lithography. So\\/Si multilayers with reflectances of 67.5 percent at 13.4 nm are now routinely achieved and reflectances of 70.2 percent at 11.4 nm were obtained with Mo\\/Be multilayers. High reflectance is achieved with careful control of substrate quality, layer thicknesses, multilayer materials, interface quality,

Claude Montcalm; Sasa Bajt; Paul B. Mirkarimi; Eberhard A. Spiller; Frank J. Weber; James A. Folta

1998-01-01

414

Method to adjust multilayer film stress induced deformation of optics  

Microsoft Academic Search

A buffer-layer located between a substrate and a multilayer for counteracting stress in the multilayer. Depositing a buffer-layer having a stress of sufficient magnitude and opposite in sign reduces or cancels out deformation in the substrate due to the stress in the multilayer. By providing a buffer-layer between the substrate and the multilayer, a tunable, near-zero net stress results, and

Paul B. Mirkarimi; Claude Montcalm

2000-01-01

415

Development of EUV free-standing multilayer polarizers  

Microsoft Academic Search

Mo\\/Si transmission multilayers are studied theoretically for use as a polarizer at 80 eV. A multilayer of 99% polarization with a maximum transmittance of 8% was obtained by optimizing the thickness of Mo and Si. It is shown that the multilayer may be also used as a quarter-wave-plate. A new and reliable method of mounting free-standing multilayers is developed.

Weibing Hu; Masaki Yamamoto; Makoto Watanabe

1996-01-01

416

Development of EUV free-standing multilayer polarizers  

NASA Astrophysics Data System (ADS)

Mo/Si transmission multilayers are studied theoretically for use as a polarizer at 80 eV. A multilayer of 99% polarization with a maximum transmittance of 8% was obtained by optimizing the thickness of Mo and Si. It is shown that the multilayer may be also used as a quarter-wave-plate. A new and reliable method of mounting free-standing multilayers is developed.

Hu, Weibing; Yamamoto, Masaki; Watanabe, Makoto

1996-08-01

417

Recent advances in etched multilayer X-ray optics  

Microsoft Academic Search

We present the recent advances achieved in the Laboratoire de Chimie Physique of Université Paris6, in the field of the soft X-ray etched multilayer optics. Modellings and characterizations are given for the laminar multilayer amplitude gratings, the highly resolutive X-ray multilayer monochromators, the X-ray polychromators and the Bragg-Fresnel multilayer linear lenses. Nous présentons les récents progrès réalisés au Laboratoire de

J. M. André; A. Sammar; S. Bac; M. Ouahabi; M. Idir; G. Soullié; R. Barchewitz

1994-01-01

418

Nanoscale Reinforced, Polymer Derived Ceramic Matrix Coatings  

SciTech Connect

The goal of this project was to explore and develop a novel class of nanoscale reinforced ceramic coatings for high temperature (600-1000 C) corrosion protection of metallic components in a coal-fired environment. It was focused on developing coatings that are easy to process and low cost. The approach was to use high-yield preceramic polymers loaded with nano-size fillers. The complex interplay of the particles in the polymer, their role in controlling shrinkage and phase evolution during thermal treatment, resulting densification and microstructural evolution, mechanical properties and effectiveness as corrosion protection coatings were investigated. Fe-and Ni-based alloys currently used in coal-fired environments do not possess the requisite corrosion and oxidation resistance for next generation of advanced power systems. One example of this is the power plants that use ultra supercritical steam as the working fluid. The increase in thermal efficiency of the plant and decrease in pollutant emissions are only possible by changing the properties of steam from supercritical to ultra supercritical. However, the conditions, 650 C and 34.5 MPa, are too severe and result in higher rate of corrosion due to higher metal temperatures. Coating the metallic components with ceramics that are resistant to corrosion, oxidation and erosion, is an economical and immediate solution to this problem. Good high temperature corrosion protection ceramic coatings for metallic structures must have a set of properties that are difficult to achieve using established processing techniques. The required properties include ease of coating complex shapes, low processing temperatures, thermal expansion match with metallic structures and good mechanical and chemical properties. Nanoscale reinforced composite coatings in which the matrix is derived from preceramic polymers have the potential to meet these requirements. The research was focused on developing suitable material systems and processing techniques for these coatings. In addition, we investigated the effect of microstructure on the mechanical properties and oxidation protection ability of the coatings. Coatings were developed to provide oxidation protection to both ferritic and austentic alloys and Ni-based alloys. The coatings that we developed are based on low viscosity pre-ceramic polymers. Thus they can be easily applied to any shape by using a variety of techniques including dip-coating, spray-coating and painting. The polymers are loaded with a variety of nanoparticles. The nanoparticles have two primary roles: control of the final composition and phases (and hence the properties); and control of the shrinkage during thermal decomposition of the polymer. Thus the selection of the nanoparticles was the most critical aspect of this project. Based on the results of the processing studies, the performance of selected coatings in oxidizing conditions (both static and cyclic) was investigated.

Rajendra Bordia

2009-07-31

419

Multilayer mirrors and beam splitters for soft X-rays  

Microsoft Academic Search

X-ray transmission coefficients for perfect multilayers have been derived based upon the optics of thin films at large angles of incidence. The new transmission coefficient together with the previously given diffraction coefficient can now be used to characterize the optical properties of multilayers. Applications of flat multilayer as X-ray beam splitters, polarizers and normal incidence mirrors are also presented.

P. Lee

1982-01-01

420

Development of an EUV polarimeter with a transmission multilayer  

Microsoft Academic Search

We developed an EUV polarimeter consisting of a transmission multilayer and a back-illumination CCD. The transmission of the multilayer at an incident angle of45-deg depends on the polarization angle. We developed a polarimeter by using the transmission. Advantages of usage a transmission multilayer are as follows. 1) The mechanics is simple, because we do not need to move the detectors.

S. Kitamoto; H. Murakami; Y. Shishido; K. Saito; T. Watanabe; J. Kanai; E. Takenaka; K. Nagasaki; D. Takei; M. Morii

2009-01-01

421

Multilayer mirrors and filters for imaging the earth's inner magnetosphere  

Microsoft Academic Search

The requirements for imaging the inner magnetosphere in the light of 304-A He(+) emission are examined. The expected EUV emission spectrum of the inner magnetosphere is used to establish guidelines for the performance of the imager's multilayer mirrors and filters. The design of multilayer mirrors and the results of a computer search that determines the best multilayer mirror design for

Dean W. Schulze; Bill R. Sandel; A. L. Broadfoot

1993-01-01

422

Method of Eigenvectors for Numerical Studies of Multilayer Gratings  

Microsoft Academic Search

A new approach to numerical studies of lamellar multilayer gratings is developed. It stands out against the existing modal and differential methods by its applicability to thick multilayer gratings with a small grating period, and also to the case of grazing incidence of radiation. The diffraction properties of multilayer gratings are calculated for x rays with the angles of incidence

V. I. Erofeev; N. V. Kovalenko

1997-01-01

423

Sound Absorption Property of Multilayered Aluminum Foam Structure  

Microsoft Academic Search

The sound absorption property of a multilayered aluminum foam structure was investigated at present work. The absorption coefficients of the structure were measured by the transfer function method. Based on the equivalent fluid model, a theoretical model for the multilayered structure was presented. Compared with the experiment, the theoretical sound absorption coefficients of the multilayered structure were consistent with experimental

Xiaohong Zhang; Songling Wang; Haibin Li

2011-01-01

424

Multilayer mirrors and beam splitters for soft X-rays  

NASA Astrophysics Data System (ADS)

X-ray transmission coefficients for perfect multilayers have been derived based upon the optics of thin films at large angles of incidence. The new transmission coefficient together with the previously given diffraction coefficient can now be used to characterize the optical properties of multilayers. Applications of flat multilayer as X-ray beam splitters, polarizers and normal incidence mirrors are also presented.

Lee, P.

1982-10-01

425

Localized modes in defective multilayer structures  

SciTech Connect

In this paper, we investigate the localized surface modes in a defective multilayer structure. We show that the defective multilayer structure can support two different kinds of localized modes, depending on the position and the thickness of the defect layer. In one kind, the modes are localized at the interface between the multilayer structure and a homogeneous medium (the so-called surface modes). While, in the other one, the modes are localized at the defect layer (defect-localized modes). We reveal that in the presence of the defect layer, the dispersion curve of the surface modes are pushed to the lower (upper) edge of the photonic band gap when the homogeneous medium is a left-handed (right-handed) material. Therefore, the existence regions of the surface modes are restricted due to the defect layer. Moreover, the effect of defect on the energy flow velocity of the surface modes is discussed.

Roshan Entezar, S. [Physics Faculty, University of Tabriz, P.O. Box 5166614766, Tabriz (Iran, Islamic Republic of); Namdar, A. [Physics Faculty, University of Tabriz, P.O. Box 5166614766, Tabriz (Iran, Islamic Republic of); Department of Physics, Azarbaidjan University of Tarbiat Moallem, P.O. Box 5167618949, Tabriz (Iran, Islamic Republic of)

2009-07-15

426

High Spectral Resolution With Multilayer Gratings  

SciTech Connect

The improvement of spectral resolution brought about by the use of multilayer grating (MG) instead of multilayer mirror (MM) is analyzed. The spectrum of a complex sample containing various elements excited under electron irradiation is studied. This sample is a pellet made by pressing powders of Cu and compounds with Fe and F atoms. The MM is a Mo/B{sub 4}C periodic multilayer with a period of about 6 nm; for the MG a grating of 1 {mu}m period has been etched in the MM. It is shown that the MG can easily resolve the F Kalpha and Fe Lalpha emissions, separated by about 30 eV, whereas the MM is unable to give such a performance. A comparison with an EDS (SDD) detector is also given. It is also shown that the MG can improve the detection limit. Finally the role of the slit placed in front of the detector is discussed.

Andre, J.-M.; Le Guen, K.; Jonnard, P. [Laboratoire de Chimie Physique-Matiere et Rayonnement, Universite Pierre et Marie Curie, CNRS UMR 7614, 11 rue Pierre et Marie Curie, F-75231 Paris Cedex 05 (France)

2010-04-06

427

Coherence preservation of synchrotron beams by multilayers  

NASA Astrophysics Data System (ADS)

This work discusses the spatial coherence preservation and the uniformity of a synchrotron beam reflected from multilayer based x-ray optics. Experiments were carried out on the ESRF undulator beamline ID06 using direct imaging and the Talbot technique. Several W/B4C multilayers with differing d-spacings were studied with monochromatic light at various photon energies. To understand the respective influence of the underlying substrate and the multilayer coatings, measurements were made under total reflection, at different Bragg peaks, and on the bare substrates. In addition, samples with different substrate quality were compared. In the present study, both the degree of spatial coherence preservation and the visibility of characteristic line structures in the x-ray beam seem to be given by the properties of the underlying substrate.

Morawe, Ch; Barrett, R.; Friedrich, K.; Klünder, R.; Vivo, A.

2013-03-01

428

Optimized capping layers for EUV multilayers  

DOEpatents

A new capping multilayer structure for EUV-reflective Mo/Si multilayers consists of two layers: A top layer that protects the multilayer structure from the environment and a bottom layer that acts as a diffusion barrier between the top layer and the structure beneath. One embodiment combines a first layer of Ru with a second layer of B.sub.4 C. Another embodiment combines a first layer of Ru with a second layer of Mo. These embodiments have the additional advantage that the reflectivity is also enhanced. Ru has the best oxidation resistance of all materials investigated so far. B.sub.4 C is an excellent barrier against silicide formation while the silicide layer formed at the Si boundary is well controlled.

Bajt, Sasa (Livermore, CA); Folta, James A. (Livermore, CA); Spiller, Eberhard A. (Livermore, CA)

2004-08-24

429

Multilayers for high heat load synchrotron applications  

NASA Astrophysics Data System (ADS)

Multilayers are the optical elements of choice in any situation where flux rather than resolution is desired. They can be tailored to optimize either reflectivity at fixed or variable energy, or heat resistance, or bandpass, or harmonic rejection. The present state of the art of x-ray multilayers is presented, and the possible applications are reviewed, including the use of multilayers as soft x-ray polarizers, large-passband elements for hard x rays, and power filters. In the situation of very intense beams the increase of temperature can produce significant changes of reflectivity, which have been extensively studied at the microstructure level in some cases, such as W/C, W/Si, and Mo/Si. Existing and prospective solutions are detailed, including heat treatment prior to x-ray exposure, use of compound materials, efficient cooling, and modification of the electric field distribution by nonperiodic arrangements.

Ziegler, Eric

1995-02-01

430

High Spectral Resolution With Multilayer Gratings  

NASA Astrophysics Data System (ADS)

The improvement of spectral resolution brought about by the use of multilayer grating (MG) instead of multilayer mirror (MM) is analyzed. The spectrum of a complex sample containing various elements excited under electron irradiation is studied. This sample is a pellet made by pressing powders of Cu and compounds with Fe and F atoms. The MM is a Mo/B4C periodic multilayer with a period of about 6 nm; for the MG a grating of 1 ?m period has been etched in the MM. It is shown that the MG can easily resolve the F K? and Fe L? emissions, separated by about 30 eV, whereas the MM is unable to give such a performance. A comparison with an EDS (SDD) detector is also given. It is also shown that the MG can improve the detection limit. Finally the role of the slit placed in front of the detector is discussed.

André, J.-M.; Le Guen, K.; Jonnard, P.

2010-04-01

431

Yield Stress and Scaling of Polyelectrolyte Multilayer Modified Suspensions: Effect of Polyelectrolyte Conformation during Multilayer Assembly.  

PubMed

The yield stress of polyelectrolyte multilayer modified suspensions exhibits a surprising dependence on the polyelectrolyte conformation of multilayer films. The rheological data scale onto a universal master curve for each polyelectrolyte conformation as the particle volume fraction, ?, and the ionic strength of the background fluid, I, are varied. It is shown that rough films with highly coiled, brushy polyelectrolytes significantly enhance the yield stress. Moreover, via the ionic strength I of the background fluid, the dynamic yield stress of brushy polyelectrolyte multilayers can be finely adjusted over 2 decades. PMID:23952570

Hess, Andreas; Aksel, Nuri

2013-08-29

432

Hetero-twin formation during growth of nano-scale Al-TiN composites - experimental and DFT studies  

SciTech Connect

It is well known that high stacking fault energy metals such as Al do not form either growth twins or mechanical twins easily. Although mechanical twins in nanocrystalline Al have been observed under certain conditions, growth twins have never been observed. In this work, the authors report for the first time, through transmission electron microscopy (TEM), that Al layers, when deposited on TiN layers, tend to grow in a twin relationship to both the TiN layer and the underlying Al layer. The TiN layers assume the orientation of the Al layers below. Calculations using density functional theory (DFT) show that nitrogen termination in the {l_brace}111{r_brace} growth plane of the TiN layers favors the growth of twin oriented Al layers over these TiN layers. This finding provides a way to create a twin-modulated structure in Al with the inclusion of intermediate nm-scale layer of an ionic solid such as TiN. Al metal is resistant to twinning, as it has a high stacking fault energy (SFE) of > 150 mJ/m. Although twins have been observed in nano-scale grains of Al, and predicted by molecular dynamics (MD) simulations in conditions when the nanoscale grains are plastically deformed, no process or phenomenon has been reported yet in which the deposition of an intermediate layer of a different material phase causes the subsequent layer of Al to be deposited in the twin orientation. The authors show in this paper that it is possible to form Al layers in twin orientation to each other across polar TiN layers, if these are grown so that both the Al and TiN layers have a {l_brace}111{r_brace} surface as their growth front. Since the deposition of Al and TiN layers is used in the formation of diffusion barriers, and the mechanical properties of these nanoscale multilayers are also seen to be exceptional, it is important to investigate and understand their structure at the nanometer length scale, and thence to be able to control it. Moreover, these findings point out a method of introducing nano-scale twins in high SFE materials in general, and can potentially improve the properties of nano-layered materials.

Bhattacharyya, Dhriti [Los Alamos National Laboratory; Liu, Xiang - Yang [Los Alamos National Laboratory; Hoagland, Richard G [Los Alamos National Laboratory; Misra, Amit [Los Alamos National Laboratory; Genc, A [MSE, OSU; Fraser, H L [MSE, OSU

2009-01-01

433

Fabricating nanoscale DNA patterns with gold nanowires.  

PubMed

Surface patterns of single-stranded DNA (ssDNA) consisting of nanoscale lines as thin as 40 nm were fabricated on polymer substrates for nanotechnology and bioaffinity sensing applications. Large scale arrays (with areas up to 4 cm(2)) of ssDNA "nanolines" were created on streptavidin-coated polymer (PDMS) surfaces by transferring biotinylated ssDNA from a master pattern of gold nanowires attached to a glass substrate. The gold nano-wires were first formed on the glass substrate by the process of lithographically patterned nanowire electrodeposition (LPNE), and then "inked" with biotinylated ssDNA by hybridization adsorption to a thiol-modified ssDNA monolayer attached to the gold nanowires. The transferred ssDNA nanolines were capable of hybridizing with ssDNA from solution to form double-stranded DNA (dsDNA) patterns; a combination of fluorescence and atomic force microscopy (AFM) measurements were used to characterize the dsDNA nanoline arrays. To demonstrate the utility of these surfaces for biosensing, optical diffraction measurements of the hybridization adsorption of DNA-coated gold nanoparticles onto the ssDNA nanoline arrays were used to detect a specific target sequence of unlabeled ssDNA in solution. PMID:20337428

Chen, Yulin; Kung, Sheng-Chin; Taggart, David K; Halpern, Aaron R; Penner, Reginald M; Corn, Robert M

2010-04-15

434

Canopy Molecular Mobility in Nanoscale Ionic Materials  

NASA Astrophysics Data System (ADS)

Nanoscale ionic materials (NIMS) are useful organic-inorganic hybrids in which a core nanostructure is functionalized with a covalently attached corona and an ionically tethered bulky organic canopy. We have used NMR relaxation and pulsed-field gradient (PFG) diffusion experiments to measure the canopy dynamics of NIMS prepared solvent-free from 18-nm silica cores modified by an alkylsilane monolayer possessing terminal sulfonic acid functionality, paired with amine-terminated ethylene oxide/propylene oxide block copolymer canopy. Carbon NMR studies show that the block copolymer canopy is quite mobile both in the bulk and in the NIMS, and that the fast (ns) dynamics are insensitive to the presence of the silica nanoparticle. Canopy diffusion in the NIMS is slowed relative to the neat canopy, but not to the degree predicted from the diffusion of hard sphere particles. Canopy diffusion is not restricted to the surface of the nanoparticles and is unchanged by the addition of excess canopy. The data indicate that the liquid-like behavior in NIMS is due to rapid exchange of the block copolymer canopy between the ionically modified nanoparticles.

von Meerwall, E.; Jespersen, M. L.; Mirau, P. A.; Vaia, R. A.; Rodriguez, R.; Giannelis, E. P.

2010-04-01

435

Canopy Dynamics in a Nanoscale Ionic Material  

NASA Astrophysics Data System (ADS)

We have used nuclear magnetic resonance (NMR) relaxation and pulsed-gradient diffusion measurements to characterize molecular mobility in a set of nanoscale ionic materials (NIMS). 18 nm core silica nanoparticles were functionalized with a covalently attached alkyl silane monolayer corona followed by an ionically tethered bulky ethylene oxide/propylene oxide block copolymer canopy. NIMS are organic-inorganic hybrids exhibiting liquid-like character under ambient conditions in the absence of solvent and are of interest for a variety of applications. Our NMR studies show that the fast (ns) local dynamics of the block copolymer canopy are insensitive to the presence of the silica nanoparticles. Canopy diffusion in the NIMS is only modestly slowed relative to the neat copolymer. Not all canopy molecules are slowed equally due to crowding at the corona-coated nanoparticle surface, resulting in strongly bound fraction at the surface and weakly bound outer sphere capable of rapid exchange of canopy molecules between host particles. Electrostatic interactions with other ionic (Na^+) species alter the dynamics by decreasing the strongly-bound population.

von Meerwall, E.; Jespersen, M. L.; Mirau, P. A.; Vaia, R. A.; Fernandes, N. J.; Giannelis, E. P.

2011-10-01

436

Biogenic nanoscale colloids in wastewater effluents.  

PubMed

The size, surface area, metal complexation capacity, organic pollutant sorption potential, reactivity with disinfectants, and elevated nitrogen content of biogenic organic nanoscale material (BONM) can potentially affect aquatic environments. BONM in effluents from 11 full-scale wastewater treatment plants (WWTPs), which use a range of biological processes, were characterized in two ways. First, BONM was measured by hydrodynamic size-exclusion chromatography coupled with an online organic carbon and UV detector. Second, BONM was isolated from the wastewater using rotary evaporation and dialysis and then characterized by elemental analysis, transmission electron microscopy, and Fourier transform infrared spectroscopy. The wastewaters contained 6-10 mg/L of dissolved organic carbon (DOC). BONM accounted for 5%-50% of the DOC in wastewater effluent organic matter, and the largest size fraction (>10 kDa) of organic carbon correlated with the organic carbon content determined after rotary evaporation and dialysis. Membrane bioreactor WWTPs had the lowest fraction of BONM (<10% of the DOC), followed by conventional activated sludge (10% to 30% of the DOC), with other processes (e.g., trickling filters, aerated lagoons) containing larger BONM percentages. BONM had a lower carbon to nitrogen ratio (6.2 ± 1.7) compared with the literature values for humic or fulvic acids, exhibited chemical bonds that were indicative of amides and polysaccharides, and contained fibril entangled networks. This work has important implications for operations efficiency of WWTPs, including controlling membrane fouling and release of organic nitrogen into sensitive environments. PMID:20886826

Song, Guixue; Wang, Jun; Chiu, Chao-An; Westerhoff, Paul

2010-11-01

437

Primary thermometry with nanoscale tunnel junctions  

SciTech Connect

We have found current-voltage (I-V) and conductance (dI/dV) characteristics of arrays of nanoscale tunnel junctions between normal metal electrodes to exhibit suitable features for primary thermometry. The current through a uniform array depends on the ratio of the thermal energy k{sub B}T and the electrostatic charging energy E{sub c} of the islands between the junctions and is completely blocked by Coulomb repulsion at T=0 and at small voltages eV/2 {<=} Ec. In the opposite limit, k{sub B}T {much_gt} E{sub c}, the width of the conductance minimum scales linearly and universally with T and N, the number of tunnel junctions, and qualifies as a primary thermometer. The zero bias drop in the conductance is proportional to T{sup -1} and can be used as a secondary thermometer. We will show with Monte Carlo simulations how background charge and nonuniformities of the array will affect the thermometer.

Hirvi, K.P.; Kauppinen, J.P.; Paalanen, M.A.; Pekola, J.P. [Univ. of Jyvaskyla (Finland)

1995-10-01

438

A DNA-based nanoscale actuator  

NASA Astrophysics Data System (ADS)

A nanoscale molecular machine, an actuator, is presented, which can be switched between two distinct configurations, a relaxed ring-like state, and a straightened rod-like configuration [1]. This stretching motion can be used to push apart molecules over a distance of several nanometers. The machine consists of DNA, being a structural material as well as a substance driving and controlling the machine's motion. The ring-like structure is formed by two stiff double-stranded DNA regions connected by one short and one long single-stranded DNA section. The short section serves as a flexible hinge. A single-stranded "fuel" DNA molecule containing a base sequence complementary to the long single-stranded portion of the machine causes the stretching motion: Upon hybridization of the complementary DNA sequences, the actuator undergoes the transition to its rod-like state. This transition can be reversed by introducing another DNA strand completely complementary to the fuel strand. This strand peels the fuel strand off the machine via the branch migration process, leaving the actuator in its relaxed state. References: [1] F. C. Simmel and B. Yurke, submitted to Phys. Rev. Lett. (2000).

Simmel, Friedrich; Yurke, Bernard

2001-03-01

439

Dynamics of nanoscale droplets on moving surfaces.  

PubMed

We use molecular dynamics (MD) simulations to investigate the dynamic wetting of nanoscale water droplets on moving surfaces. The density and hydrogen bonding profiles along the direction normal to the surface are reported, and the width of the water depletion layer is evaluated first for droplets on three different static surfaces: silicon, graphite, and a fictitious superhydrophobic surface. The advancing and receding contact angles, and contact angle hysteresis, are then measured as a function of capillary number on smooth moving silicon and graphite surfaces. Our results for the silicon surface show that molecular displacements at the contact line are influenced greatly by interactions with the solid surface and partly by viscous dissipation effects induced through the movement of the surface. For the graphite surface, however, both the advancing and receding contact angles values are close to the static contact angle value and are independent of the capillary number; i.e., viscous dissipation effects are negligible. This finding is in contrast with the wetting dynamics of macroscale water droplets, which show significant dependence on the capillary number. PMID:23683083

Ritos, Konstantinos; Dongari, Nishanth; Borg, Matthew K; Zhang, Yonghao; Reese, Jason M

2013-05-28

440

Nanoscale analysis of structural synaptic plasticity  

PubMed Central

In the 1950’s, transmission electron microscopy was first used to reveal the diversity in synaptic structure and composition in the central nervous system [1;2]. Since then, visualization and reconstruction of serial thin sections have provided three-dimensional contexts in which to understand how synapses are modified with plasticity, learning, and sensory input [3–17]. Three-dimensional reconstruction from serial section electron microscopy (ssEM) has proven invaluable for the comprehensive analysis of structural synaptic plasticity. It has provided the needed nanometer resolution to localize and measure key subcellular structures, such as the postsynaptic density (PSD) and presynaptic vesicles which define a synapse, polyribosomes as sites of local protein synthesis, smooth endoplasmic reticulum (SER) for local regulation of calcium and trafficking of membrane proteins, endosomes for recycling, and fine astroglial processes at the perimeter of some synapses. Thus, ssEM is an essential tool for nanoscale analysis of the cell biological and anatomical modifications that underlie changes in synaptic strength. Here we discuss several important issues associated with interpreting the functional significance of structural synaptic plasticity, especially during long-term potentiation, a widely studied cellular model of learning and memory.

Bourne, Jennifer N.; Harris, Kristen M.

2011-01-01

441

Nanoscale photonics of structural transformations in Gallium  

NASA Astrophysics Data System (ADS)

We have found recently that Gallium, confined at an interface with silica, responds dramatically to low power optical excitation when held at temperatures close to its melting point (29.8°C). Intensities of just a few kW/cm2 can reversibly modulate the intensity (by up to 40%) and phase (by as much as several degrees) of reflected light as the result of a light-induced structural transition occurring in a layer of gallium of only a few nm thick. Here, we report that this concept - of achieving a nonlinearity via a light-induced transformation in a confined solid at a temperature close to a phase transition temperature - can also be applied to gallium nanoparticles. We present the transient all-optical switching characteristics of gallium nanoparticle films comprising particles, typically 80 nm in diameter, which were formed directly on the ends of optical fibers using a new light-assisted self-assembly technique. We also report, for the first time, that this light-induced structural transition in gallium confined at an interface with silica underlies a new mechanism for photoconductivity. In our opinion, the exploitation of the light-induced phase transition in gallium may be a means of enabling the development of nanoscale photonic devices.

Zheludev, Nikolay I.; Fedotov, V. A.; MacDonald, K. F.; Stevens, G. C.; Pochon, Sebastien C.; Woodford, M.

2002-09-01

442

Nanoscale buckling deformation in layered copolymer materials  

PubMed Central

In layered materials, a common mode of deformation involves buckling of the layers under tensile deformation in the direction perpendicular to the layers. The instability mechanism, which operates in elastic materials from geological to nanometer scales, involves the elastic contrast between different layers. In a regular stacking of “hard” and “soft” layers, the tensile stress is first accommodated by a large deformation of the soft layers. The inhibited Poisson contraction results in a compressive stress in the direction transverse to the tensile deformation axis. The hard layers sustain this transverse compression until buckling takes place and results in an undulated structure. Using molecular simulations, we demonstrate this scenario for a material made of triblock copolymers. The buckling deformation is observed to take place at the nanoscale, at a wavelength that depends on strain rate. In contrast to what is commonly assumed, the wavelength of the undulation is not determined by defects in the microstructure. Rather, it results from kinetic effects, with a competition between the rate of strain and the growth rate of the instability.

Makke, Ali; Perez, Michel; Lame, Olivier; Barrat, Jean-Louis

2012-01-01

443

Fabricating Nanoscale DNA Patterns with Gold Nanowires  

PubMed Central

Surface patterns of single-stranded DNA (ssDNA) consisting of nanoscale lines as thin as 40 nm were fabricated on polymer substrates for nanotechnology and bioaffinity sensing applications. Large scale arrays (with areas up to 4 cm2) of ssDNA “nanolines” were created on streptavidin-coated polymer (PDMS) surfaces by transferring biotinylated ssDNA from a master pattern of gold nanowires attached to a glass substrate. The gold nanowires were first formed on the glass substrate by the process of lithographically patterned nanowire electrodeposition (LPNE), and then “inked” with biotinylated ssDNA by hybridization adsorption to a thiol-modified ssDNA monolayer attached to the gold nanowires. The transferred ssDNA nanolines were capable of hybridizing with ssDNA from solution to form double-stranded DNA (dsDNA) patterns; a combination of fluorescence and AFM measurements were used to characterize the dsDNA nanoline arrays. To demonstrate the utility of these surfaces for biosensing, optical diffraction measurements of the hybridization adsorption of DNA-coated gold nanoparticles onto the ssDNA nanoline arrays were used to detect a specific target sequence of unlabeled ssDNA in solution.

Chen, Yulin; Kung, Sheng-Chin; Taggart, David K.; Halpern, Aaron R.; Penner, Reginald M.; Corn, Robert M.

2010-01-01

444

Nanoscale pore formation dynamics during aluminum anodization  

NASA Astrophysics Data System (ADS)

A theoretical analysis of nanoscale pore formation during anodization reveals its fundamental instability mechanism to be a field focusing phenomenon when perturbations on the minima of the two oxide interfaces are in phase. Lateral leakage of the layer potential at high wave number introduces a layer tension effect that balances the previous destabilizing effect to produce a long-wave instability and a selected pore separation that scales linearly with respect to voltage. At pH higher than 1.77, pores do not form due to a very thick barrier layer. A weakly nonlinear theory based on long-wave expansion of double free surface problem yields two coupled interface evolution equations that can be reduced to one without altering the dispersion relationship by assuming an equal and in-phase amplitude for the two interfaces. This interface evolution equation faithfully reproduces the initial pore ordering and their dynamics. A hodograph transformation technique is then used to determine the interior dimension of the well-developed pores in two dimensions. The ratio of pore diameter to pore separation is found to be a factor independent of voltage but varies with the pH of the electrolyte. Both the predicted pH range where pores are formed and the predicted pore dimensions are favorably compared to experimental data.

Thamida, Sunil Kumar; Chang, Hsueh-Chia

2002-03-01

445

Energy-harvesting at the Nanoscale  

NASA Astrophysics Data System (ADS)

Energy harvesting is the process by which energy is taken from the environment and transformed to provide power for electronics. Specifically, the conversion of thermal energy into electrical power, or thermoelectrics, can play a crucial role in future developments of alternative