Large area bulk superconductors

DOEpatents

Miller, Dean J.; Field, Michael B.

2002-01-01

A bulk superconductor having a thickness of not less than about 100 microns is carried by a polycrystalline textured substrate having misorientation angles at the surface thereof not greater than about 15.degree.; the bulk superconductor may have a thickness of not less than about 100 microns and a surface area of not less than about 50 cm.sup.2. The textured substrate may have a thickness not less than about 10 microns and misorientation angles at the surface thereof not greater than about 15.degree.. Also disclosed is a process of manufacturing the bulk superconductor and the polycrystalline biaxially textured substrate material.

Thick, low-stress films, and coated substrates formed therefrom, and methods for making same

DOEpatents

Henager, Jr., Charles H.; Knoll, Robert W.

1992-01-01

Stress-induced deformation, and the damage resulting therefrom, increases with film thickness. The overcoming of excessive stress by the use of the Si-Al-N film material of the present invention, permits the formation of thick films that are necessary for certain of the above described applications. The most likely use for the subject film materials, other than their specialized views as an optical film, is for microelectronic packaging of components on silicon substrates. In general, the subject films have excellent adherence to the underlying substrate, a high degree of hardness and durability, and are excellent insulators. Prior art elevated temperature deposition processes cannot meet the microelectronic packaging temperature formation constraints. The process of the present invention is conducted under non-elevated temperature conditions, typically 500.degree. C. or less.

Composite scintillator screen

DOEpatents

Zeman, Herbert D.

1994-01-01

A scintillator screen for an X-ray system includes a substrate of low-Z material and bodies of a high-Z material embedded within the substrate. By preselecting the size of the bodies embedded within the substrate, the spacial separation of the bodies and the thickness of the screen, the sensitivity of the screen to X-rays within a predetermined energy range can be predicted.

A phenomenological model of coating/substrate adhesion and interfacial bimetallic peeling stress in composite mirrors

NASA Technical Reports Server (NTRS)

Mcelroy, Paul M.; Lawson, Daniel D.

1990-01-01

Adhesion and interfacial stress between metal films and structural composite material substrates is discussed. A theoretical and conceptual basis for selecting coating materials for composite mirror substrates is described. A phenomenological model that interrelates cohesive tensile strength of thin film coatings and interfacial peeling stresses is presented. The model serves as a basis in determining gradiated materials response and compatibility of composite substrate and coating combinations. Parametric evaluation of material properties and geometrical factors such as coating thickness are used to determine the threshold stress levels for maintaining adhesion at the different interfaces.

Molecular beam epitaxy of large-area SnSe2 with monolayer thickness fluctuation

NASA Astrophysics Data System (ADS)

Park, Young Woon; Jerng, Sahng-Kyoon; Jeon, Jae Ho; Roy, Sanjib Baran; Akbar, Kamran; Kim, Jeong; Sim, Yumin; Seong, Maeng-Je; Kim, Jung Hwa; Lee, Zonghoon; Kim, Minju; Yi, Yeonjin; Kim, Jinwoo; Noh, Do Young; Chun, Seung-Hyun

2017-03-01

The interest in layered materials is largely based on the expectation that they will be beneficial for a variety of applications, from low-power-consuming, wearable electronics to energy harvesting. However, the properties of layered materials are highly dependent on thickness, and the difficulty of controlling thickness over a large area has been a bottleneck for commercial applications. Here, we report layer-by-layer growth of SnSe2, a layered semiconducting material, via van der Waals epitaxy. The films were fabricated on insulating mica substrates with substrate temperatures in the range of 210 °C-370 °C. The surface consists of a mixture of N and (N ± 1) layers, showing that the thickness of the film can be defined with monolayer accuracy (±0.6 nm). High-resolution transmission electron microscopy reveals a polycrystalline film with a grain size of ˜100 nm and clear Moiré patterns from overlapped grains with similar thickness. We also report field effect mobility values of 3.7 cm2 V-1 s-1 and 6.7 cm2 V-1 s-1 for 11 and 22 nm thick SnSe2, respectively. SnSe2 films with customizable thickness can provide valuable platforms for industry and academic researchers to fully exploit the potential of layered materials.

Thermoelectric material including conformal oxide layers and method of making the same using atomic layer deposition

DOEpatents

Cho, Jung Young; Ahn, Dongjoon; Salvador, James R.; Meisner, Gregory P.

2016-06-07

A thermoelectric material includes a substrate particle and a plurality of conformal oxide layers formed on the substrate particle. The plurality of conformal oxide layers has a total oxide layer thickness ranging from about 2 nm to about 20 nm. The thermoelectric material excludes oxide nanoparticles. A method of making the thermoelectric material is also disclosed herein.

Fabrication of fuel cell electrodes and other catalytic structures

DOEpatents

Smith, J.L.

1987-02-11

A porous layer of catalyst material suitable for use as an electrode in a molten carbonate fuel cell includes elongated pores substantially extending across the layer thickness. The catalyst layer is prepared by depositing particulate catalyst material into polymeric flocking on a substrate surface by a procedure such as tape casting. The loaded substrate is heated in a series of steps with rising temperatures to set the tape, thermally decompose the substrate with flocking and sinter bond the catalyst particles into a porous catalytic layer with elongated pores across its thickness. Employed as an electrode, the elongated pores provide distribution of reactant gas into contact with catalyst particles wetted by molten electrolyte. 1 fig.

Fabrication of catalytic electrodes for molten carbonate fuel cells

DOEpatents

Smith, James L.

1988-01-01

A porous layer of catalyst material suitable for use as an electrode in a molten carbonate fuel cell includes elongated pores substantially extending across the layer thickness. The catalyst layer is prepared by depositing particulate catalyst material into polymeric flocking on a substrate surface by a procedure such as tape casting. The loaded substrate is heated in a series of steps with rising temperatures to set the tape, thermally decompose the substrate with flocking and sinter bond the catalyst particles into a porous catalytic layer with elongated pores across its thickness. Employed as an electrode, the elongated pores provide distribution of reactant gas into contact with catalyst particles wetted by molten electrolyte.

The microwave properties of Ag(Ta0.8Nb0.2)O3 thick film interdigital capacitors on alumina substrates

NASA Astrophysics Data System (ADS)

Lee, Ku-Tak; Koh, Jung-Hyuk

2012-01-01

In this paper, we will introduce the microwave properties of Ag(Ta0.8Nb0.2)O3 thick film planar type interdigital capacitors fabricated on alumina substrates. The tailored paraelectric state of Ag(Ta,Nb)O3 allows the material to be regarded as a part of the family of microwave materials. As thick films formed in our experiment, Ag(Ta,Nb)O3 exhibited extremely low dielectric loss with relatively high dielectric permittivity. This low dielectric loss is a very important issue for microwave applications. Therefore, we investigated the microwave properties of Ag(Ta0.8Nb0.2)O3 thick film planar type interdigital capacitors. Ag(Ta0.8Nb0.2)O3 thick films were prepared by a screen-printing method on alumina substrates and were sintered at 1140 °C for 2 hrs. The XRD analysis results showed that the Ag(Ta0.8Nb0.2)O3 thick film has the perovskite structure. The frequency dependent dielectric permittivity showed that these Ag(Ta0.8Nb0.2)O3 thick film planar type interdigital capacitors have very weak frequency dispersions with low loss tangents in the microwave range.

Superconductivity devices: Commercial use of space

NASA Technical Reports Server (NTRS)

Haertling, Gene; Hsi, Chi-Shiung; Li, Guang

1992-01-01

High T sub C superconducting thick film were prepared by a screen printing process. Y-based (YBa2Cu3O(7-x) superconducting thick film were printed on 211/Al2O3, SNT/Al2O3, and YSZ substrates. Because of poor adhesion of the superconductor thick films to 211/Al2O3 and SNT/Al2O3 substrates, relatively low T sub C and J sub C values were obtained from the films printed on these substrates. Critical temperatures (T sub C) of YBa2Cu3O(7-x) thick films deposited on 211/Al2O3 and SNT/Al2O3 substrates were about 80 K. The critical current densities (J sub C) of these films were less than 2 A/sq cm. Higher T sub C and J sub C YBa2Cu3O(7-x) thick films were printed on YSZ substrates. A YBa2Cu3O(7-x) thick film with T sub C=86.4 and J sub C= 50.4 A/sq cm was prepared by printing the film on YSZ substrate and firing at 990 C for 10 minutes. Multiple-lead samples were also prepared on the YSZ substrates. The multiple-lead samples showed lower T sub C and/or J sub C values than those of the plain samples. The electrical properties of YBa2Cu3O(7-x) thick films were determined by the microstructures of the films. The YBa2Cu3O(7-x) thick films printed on the YSZ substrates, which had the best properties among the films printed on the three different kinds of substrates, had the highest density and the best particle interconnection. The YBa2Cu3O(7-x) thick films with preferred orientation in (001) direction were obtained on the YSZ substrates. Cracks, which retard the properties of the films, were found from the films deposited on the YSZ substrates. Currently, a MSZ (Magnesium Stabilized Zirconia) substrate, which had higher thermal expansion coefficient than the YSZ substrate, is used as substrate for the YBa2Cu3O(7-x) thick film in order to eliminate the cracks on the film. Bi-based superconductor thick films were printed on polycrystalline MgO and YSZ substrates. Interactions between BSCCO thick films and the YSZ substrates were observed. Various buffer layer materials were applied onto the substrates in order to avoid the interactions between the BSCCO thick films and the ZrO2-based substrates. So far, a BSCCO printed on MgO substrate with T Sub C=89K was obtained. The J sub C of the film was lower than 0.1 A/sq cm by reason of poor interconnectivity of the BSCCO particles.

Optical influence of the type of illuminant, substrates and thickness of ceramic materials.

PubMed

Volpato, Cláudia Angela Maziero; Monteiro, Sylvio; de Andrada, Mauro Caldeira; Fredel, Márcio Celso; Petter, Carlos Otávio

2009-01-01

The present study is an instrumental evaluation of the optical influence of the type of illuminant, substrate and different thickness on the color of dental ceramics. Thirty ceramic disks were prepared from IPS-Empress and IPS-Empress2 in three different thicknesses (1.5, 2.0 and 2.5mm). Disks made of composite resin; silver-palladium alloy and gold were used as substrates. The disks with a 1.5mm thickness were placed on a neutral gray photographic paper and measured with a spectrophotometer under three illuminants: daylight (D65), incandescent light (A) and fluorescent light (F6). All ceramic disks were combined with the substrate disks and a spectrophotometer was used to measure the coordinates of lightness (L*) and chromaticity (a* and b*). Two-way ANOVA (p<0.05) was used to analyze the combinations of ceramics, substrates and illuminants tested considering the coordinates of lightness (L*) and chromaticity (a* and b*), and also differences of color (DeltaE), lightness (DeltaL*), chromaticity values (Deltaa* and Deltab*). For the illuminants tested, the results present significant differences for coordinates of chromaticity a* and b*, suggesting a metamerism effect. In combination with the substrates, the results present statistical differences in all the tested conditions, especially where there is no ceramic substructure. The presence of discolored tooth remnants or metallic posts and cores can interfere with the desired aesthetic result, based on the selection of color aided by a single luminous source. Thus, the substrate color effect, thickness of the ceramic materials and type of illuminant are important factors to be considered during the clinical application of the ceramic systems.

Simple approach for high-contrast optical imaging and characterization of graphene-based sheets.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jung, I.; Pelton, M.; Piner, R.

2007-12-01

A simple optical method is presented for identifying and measuring the effective optical properties of nanometer-thick, graphene-based materials, based on the use of substrates consisting of a thin dielectric layer on silicon. High contrast between the graphene-based materials and the substrate is obtained by choosing appropriate optical properties and thickness of the dielectric layer. The effective refractive index and optical absorption coefficient of graphene oxide, thermally reduced graphene oxide, and graphene are obtained by comparing the predicted and measured contrasts.

Substrate independent approach for synthesis of graphene platelet networks.

PubMed

Shashurin, A; Fang, X; Zemlyanov, D; Keidar, M

2017-06-23

Graphene platelet networks (GPNs) comprised of randomly oriented graphene flakes two to three atomic layers thick are synthesized using a novel plasma-based approach. The approach uses a substrate capable of withstanding synthesis temperatures around 800 °C, but is fully independent of the substrate material. The synthesis occurs directly on the substrate surface without the necessity of any additional steps. GPNs were synthesized on various substrate materials including silicon (Si), thermally oxidized Si (SiO 2 ), molybdenum (Mo), nickel (Ni) and copper (Cu), nickel-chromium (NiCr) alloy and alumina ceramics (Al 2 O 3 ). The mismatch between the atomic structures of sp 2 honeycomb carbon networks and the substrate material is fully eliminated shortly after the synthesis initiation, namely when about 100 nm thick deposits are formed on the substrate. GPN structures synthesized on a substrate at a temperature of about 800 °C are significantly more porous in comparison to the much denser packed amorphous carbon deposits synthesized at lower temperatures. The method proposed here can potentially revolutionize the area of electrochemical energy storage by offering a single-step direct approach for the manufacture of graphene-based electrodes for non-Faradaic supercapacitors. Mass production can be achieved using this method if a roll-to-roll system is utilized.

Substrate independent approach for synthesis of graphene platelet networks

NASA Astrophysics Data System (ADS)

Shashurin, A.; Fang, X.; Zemlyanov, D.; Keidar, M.

2017-06-01

Graphene platelet networks (GPNs) comprised of randomly oriented graphene flakes two to three atomic layers thick are synthesized using a novel plasma-based approach. The approach uses a substrate capable of withstanding synthesis temperatures around 800 °C, but is fully independent of the substrate material. The synthesis occurs directly on the substrate surface without the necessity of any additional steps. GPNs were synthesized on various substrate materials including silicon (Si), thermally oxidized Si (SiO2), molybdenum (Mo), nickel (Ni) and copper (Cu), nickel-chromium (NiCr) alloy and alumina ceramics (Al2O3). The mismatch between the atomic structures of sp2 honeycomb carbon networks and the substrate material is fully eliminated shortly after the synthesis initiation, namely when about 100 nm thick deposits are formed on the substrate. GPN structures synthesized on a substrate at a temperature of about 800 °C are significantly more porous in comparison to the much denser packed amorphous carbon deposits synthesized at lower temperatures. The method proposed here can potentially revolutionize the area of electrochemical energy storage by offering a single-step direct approach for the manufacture of graphene-based electrodes for non-Faradaic supercapacitors. Mass production can be achieved using this method if a roll-to-roll system is utilized.

Versatile technique for assessing thickness of 2D layered materials by XPS

NASA Astrophysics Data System (ADS)

Zemlyanov, Dmitry Y.; Jespersen, Michael; Zakharov, Dmitry N.; Hu, Jianjun; Paul, Rajib; Kumar, Anurag; Pacley, Shanee; Glavin, Nicholas; Saenz, David; Smith, Kyle C.; Fisher, Timothy S.; Voevodin, Andrey A.

2018-03-01

X-ray photoelectron spectroscopy (XPS) has been utilized as a versatile method for thickness characterization of various two-dimensional (2D) films. Accurate thickness can be measured simultaneously while acquiring XPS data for chemical characterization of 2D films having thickness up to approximately 10 nm. For validating the developed technique, thicknesses of few-layer graphene (FLG), MoS2 and amorphous boron nitride (a-BN) layer, produced by microwave plasma chemical vapor deposition (MPCVD), plasma enhanced chemical vapor deposition (PECVD), and pulsed laser deposition (PLD) respectively, were accurately measured. The intensity ratio between photoemission peaks recorded for the films (C 1s, Mo 3d, B 1s) and the substrates (Cu 2p, Al 2p, Si 2p) is the primary input parameter for thickness calculation, in addition to the atomic densities of the substrate and the film, and the corresponding electron attenuation length (EAL). The XPS data was used with a proposed model for thickness calculations, which was verified by cross-sectional transmission electron microscope (TEM) measurement of thickness for all the films. The XPS method determines thickness values averaged over an analysis area which is orders of magnitude larger than the typical area in cross-sectional TEM imaging, hence provides an advanced approach for thickness measurement over large areas of 2D materials. The study confirms that the versatile XPS method allows rapid and reliable assessment of the 2D material thickness and this method can facilitate in tailoring growth conditions for producing very thin 2D materials effectively over a large area. Furthermore, the XPS measurement for a typical 2D material is non-destructive and does not require special sample preparation. Therefore, after XPS analysis, exactly the same sample can undergo further processing or utilization.

Versatile technique for assessing thickness of 2D layered materials by XPS

DOE PAGES

Zemlyanov, Dmitry Y.; Jespersen, Michael; Zakharov, Dmitry N.; ...

2018-02-07

X-ray photoelectron spectroscopy (XPS) has been utilized as a versatile method for thickness characterization of various two-dimensional (2D) films. Accurate thickness can be measured simultaneously while acquiring XPS data for chemical characterization of 2D films having thickness up to approximately 10 nm. For validating the developed technique, thicknesses of few-layer graphene (FLG), MoS 2 and amorphous boron nitride (a-BN) layer, produced by microwave plasma chemical vapor deposition (MPCVD), plasma enhanced chemical vapor deposition (PECVD), and pulsed laser deposition (PLD) respectively, were accurately measured. The intensity ratio between photoemission peaks recorded for the films (C 1s, Mo 3d, B 1s) andmore » the substrates (Cu 2p, Al 2p, Si 2p) is the primary input parameter for thickness calculation, in addition to the atomic densities of the substrate and the film, and the corresponding electron attenuation length (EAL). The XPS data was used with a proposed model for thickness calculations, which was verified by cross-sectional transmission electron microscope (TEM) measurement of thickness for all the films. The XPS method determines thickness values averaged over an analysis area which is orders of magnitude larger than the typical area in cross-sectional TEM imaging, hence provides an advanced approach for thickness measurement over large areas of 2D materials. The study confirms that the versatile XPS method allows rapid and reliable assessment of the 2D material thickness and this method can facilitate in tailoring growth conditions for producing very thin 2D materials effectively over a large area. Furthermore, the XPS measurement for a typical 2D material is non-destructive and does not require special sample preparation. Furthermore, after XPS analysis, exactly the same sample can undergo further processing or utilization.« less

Versatile technique for assessing thickness of 2D layered materials by XPS.

PubMed

Zemlyanov, Dmitry Y; Jespersen, Michael; Zakharov, Dmitry N; Hu, Jianjun; Paul, Rajib; Kumar, Anurag; Pacley, Shanee; Glavin, Nicholas; Saenz, David; Smith, Kyle C; Fisher, Timothy S; Voevodin, Andrey A

2018-03-16

X-ray photoelectron spectroscopy (XPS) has been utilized as a versatile method for thickness characterization of various two-dimensional (2D) films. Accurate thickness can be measured simultaneously while acquiring XPS data for chemical characterization of 2D films having thickness up to approximately 10 nm. For validating the developed technique, thicknesses of few-layer graphene (FLG), MoS 2 and amorphous boron nitride (a-BN) layer, produced by microwave plasma chemical vapor deposition (MPCVD), plasma enhanced chemical vapor deposition (PECVD), and pulsed laser deposition (PLD) respectively, were accurately measured. The intensity ratio between photoemission peaks recorded for the films (C 1s, Mo 3d, B 1s) and the substrates (Cu 2p, Al 2p, Si 2p) is the primary input parameter for thickness calculation, in addition to the atomic densities of the substrate and the film, and the corresponding electron attenuation length (EAL). The XPS data was used with a proposed model for thickness calculations, which was verified by cross-sectional transmission electron microscope (TEM) measurement of thickness for all the films. The XPS method determines thickness values averaged over an analysis area which is orders of magnitude larger than the typical area in cross-sectional TEM imaging, hence provides an advanced approach for thickness measurement over large areas of 2D materials. The study confirms that the versatile XPS method allows rapid and reliable assessment of the 2D material thickness and this method can facilitate in tailoring growth conditions for producing very thin 2D materials effectively over a large area. Furthermore, the XPS measurement for a typical 2D material is non-destructive and does not require special sample preparation. Therefore, after XPS analysis, exactly the same sample can undergo further processing or utilization.

Versatile technique for assessing thickness of 2D layered materials by XPS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zemlyanov, Dmitry Y.; Jespersen, Michael; Zakharov, Dmitry N.

X-ray photoelectron spectroscopy (XPS) has been utilized as a versatile method for thickness characterization of various two-dimensional (2D) films. Accurate thickness can be measured simultaneously while acquiring XPS data for chemical characterization of 2D films having thickness up to approximately 10 nm. For validating the developed technique, thicknesses of few-layer graphene (FLG), MoS 2 and amorphous boron nitride (a-BN) layer, produced by microwave plasma chemical vapor deposition (MPCVD), plasma enhanced chemical vapor deposition (PECVD), and pulsed laser deposition (PLD) respectively, were accurately measured. The intensity ratio between photoemission peaks recorded for the films (C 1s, Mo 3d, B 1s) andmore » the substrates (Cu 2p, Al 2p, Si 2p) is the primary input parameter for thickness calculation, in addition to the atomic densities of the substrate and the film, and the corresponding electron attenuation length (EAL). The XPS data was used with a proposed model for thickness calculations, which was verified by cross-sectional transmission electron microscope (TEM) measurement of thickness for all the films. The XPS method determines thickness values averaged over an analysis area which is orders of magnitude larger than the typical area in cross-sectional TEM imaging, hence provides an advanced approach for thickness measurement over large areas of 2D materials. The study confirms that the versatile XPS method allows rapid and reliable assessment of the 2D material thickness and this method can facilitate in tailoring growth conditions for producing very thin 2D materials effectively over a large area. Furthermore, the XPS measurement for a typical 2D material is non-destructive and does not require special sample preparation. Furthermore, after XPS analysis, exactly the same sample can undergo further processing or utilization.« less

Coating defect evaluation based on stimulated thermography

NASA Astrophysics Data System (ADS)

Palumbo, Davide; Tamborrino, Rosanna; Galietti, Umberto

2017-05-01

Thermal Barrier Coatings are used to protect the materials from severe temperature and chemical environments. In particular, these materials are used in the engineering fields where high temperatures, corrosive environments and high mechanical stress are required. Defects present between substrate material and coating, as detachments may cause the break of coating and the consequent possibility to exposure the substrate material to the environment conditions. The capability to detect the defect zones with non-destructive techniques could allow the maintenance of coated components with great advantages in terms of costs and prediction of fatigue life. In this work, two different heat sources and two different thermographic techniques have been used to detect the adhesion defects among the base material and the coating. Moreover, an empirical thermographic method has been developed to evaluate the thickness of the thermal coating and to discriminate between an unevenness of the thickness and a defect zone. The study has been conducted on circular steel specimens with simulated adhesion defect and on specimens prepared with different thicknesses of thermal barrier coating.

Degradation of Polymer-Coated Materials

DTIC Science & Technology

2013-10-01

Al and Al - Cu alloy metallizations about 800 nm thick were deposited on glass substrates and...accumulation under corrosion resistant organic coatings. Al and Al - Cu alloy metallizations about 800 nm thick were deposited on glass substrates and then...exposed to salt spray chamber for 16 days. Figure 1.4.10 Images of corrosion sites in Al - Cu thin film at “As deposited ” condition under

Metal-free magnetic conductor substrates for placement-immune antenna assemblies

DOEpatents

Eubanks, Travis Wayne; Loui, Hung; McDonald, Jacob Jeremiah

2015-09-29

A magnetic conductor substrate produced for mounting to an antenna includes a sheet of dielectric lattice material having a length, a width and a thickness that is less than the length and less than the width. Within the sheet of dielectric lattice material is disposed an array of dielectric elements.

Test results for electron beam charging of flexible insulators and composites. [solar array substrates, honeycomb panels, and thin dielectric films

NASA Technical Reports Server (NTRS)

Staskus, J. V.; Berkopec, F. D.

1979-01-01

Flexible solar-array substrates, graphite-fiber/epoxy - aluminum honeycomb panels, and thin dielectric films were exposed to monoenergetic electron beams ranging in energy from 2 to 20 keV in the Lewis Research Center's geomagnetic-substorm-environment simulation facility to determine surface potentials, dc currents, and surface discharges. The four solar-array substrate samples consisted of Kapton sheet reinforced with fabrics of woven glass or carbon fibers. They represented different construction techniques that might be used to reduce the charge accumulation on the array back surface. Five honeycomb-panel samples were tested, two of which were representative of Voyager antenna materials and had either conductive or nonconductive painted surfaces. A third sample was of Navstar solar-array substrate material. The other two samples were of materials proposed for use on Intelsat V. All the honeycomb-panel samples had graphite-fiber/epoxy composite face sheets. The thin dielectric films were 2.54-micrometer-thick Mylar and 7.62-micrometer-thick Kapton.

Flexible top-emitting OLEDs for lighting: bending limits

NASA Astrophysics Data System (ADS)

Schwamb, Philipp; Reusch, Thilo C.; Brabec, Christoph J.

2013-09-01

Flexible OLED light sources have great appeal due to new design options, being unbreakable and their low weight. Top-emitting OLED device architectures offer the broadest choice of substrate materials including metals which are robust, impermeable to humidity, and good thermal conductors making them promising candidates for flexible OLED device substrates. In this study, we investigate the bending limits of flexible top-emitting OLED lighting devices with transparent metal electrode and thin film encapsulation on a variety of both metal and plastic foils. The samples were subjected to concave and convex bending and inspected by different testing methods for the onset of breakdown for example visible defects and encapsulation failures. The critical failure modes were identified as rupture of the transparent thin metal top electrode and encapsulation for convex bending and buckling of the transparent metal top electrode for concave bending. We investigated influences from substrate material and thickness and top coating thickness. The substrate thickness is found to dominate bending limits as expected by neutral layer modeling. Coating shows strong improvements for all substrates. Bending radii <15mm are achieved for both convex and concave testing without damage to devices including their encapsulation.

Chemical vapor deposition reactor. [providing uniform film thickness

NASA Technical Reports Server (NTRS)

Chern, S. S.; Maserjian, J. (Inventor)

1977-01-01

An improved chemical vapor deposition reactor is characterized by a vapor deposition chamber configured to substantially eliminate non-uniformities in films deposited on substrates by control of gas flow and removing gas phase reaction materials from the chamber. Uniformity in the thickness of films is produced by having reactive gases injected through multiple jets which are placed at uniformally distributed locations. Gas phase reaction materials are removed through an exhaust chimney which is positioned above the centrally located, heated pad or platform on which substrates are placed. A baffle is situated above the heated platform below the mouth of the chimney to prevent downdraft dispersion and scattering of gas phase reactant materials.

Collective Cell Behavior in Mechanosensing of Substrate Thickness.

PubMed

Tusan, Camelia G; Man, Yu-Hin; Zarkoob, Hoda; Johnston, David A; Andriotis, Orestis G; Thurner, Philipp J; Yang, Shoufeng; Sander, Edward A; Gentleman, Eileen; Sengers, Bram G; Evans, Nicholas D

2018-06-05

Extracellular matrix stiffness has a profound effect on the behavior of many cell types. Adherent cells apply contractile forces to the material on which they adhere and sense the resistance of the material to deformation-its stiffness. This is dependent on both the elastic modulus and the thickness of the material, with the corollary that single cells are able to sense underlying stiff materials through soft hydrogel materials at low (<10 μm) thicknesses. Here, we hypothesized that cohesive colonies of cells exert more force and create more hydrogel deformation than single cells, therefore enabling them to mechanosense more deeply into underlying materials than single cells. To test this, we modulated the thickness of soft (1 kPa) elastic extracellular-matrix-functionalized polyacrylamide hydrogels adhered to glass substrates and allowed colonies of MG63 cells to form on their surfaces. Cell morphology and deformations of fluorescent fiducial-marker-labeled hydrogels were quantified by time-lapse fluorescence microscopy imaging. Single-cell spreading increased with respect to decreasing hydrogel thickness, with data fitting to an exponential model with half-maximal response at a thickness of 3.2 μm. By quantifying cell area within colonies of defined area, we similarly found that colony-cell spreading increased with decreasing hydrogel thickness but with a greater half-maximal response at 54 μm. Depth-sensing was dependent on Rho-associated protein kinase-mediated cellular contractility. Surface hydrogel deformations were significantly greater on thick hydrogels compared to thin hydrogels. In addition, deformations extended greater distances from the periphery of colonies on thick hydrogels compared to thin hydrogels. Our data suggest that by acting collectively, cells mechanosense rigid materials beneath elastic hydrogels at greater depths than individual cells. This raises the possibility that the collective action of cells in colonies or sheets may allow cells to sense structures of differing material properties at comparatively large distances. Copyright © 2018 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Acicular photomultiplier photocathode structure

DOEpatents

Craig, Richard A.; Bliss, Mary

2003-09-30

A method and apparatus for increasing the quantum efficiency of a photomultiplier tube by providing a photocathode with an increased surface-to-volume ratio. The photocathode includes a transparent substrate, upon one major side of which is formed one or more large aspect-ratio structures, such as needles, cones, fibers, prisms, or pyramids. The large aspect-ratio structures are at least partially composed of a photoelectron emitting material, i.e., a material that emits a photoelectron upon absorption of an optical photon. The large aspect-ratio structures may be substantially composed of the photoelectron emitting material (i.e., formed as such upon the surface of a relatively flat substrate) or be only partially composed of a photoelectron emitting material (i.e., the photoelectron emitting material is coated over large aspect-ratio structures formed from the substrate material itself.) The large aspect-ratio nature of the photocathode surface allows for an effective increase in the thickness of the photocathode relative the absorption of optical photons, thereby increasing the absorption rate of incident photons, without substantially increasing the effective thickness of the photocathode relative the escape incidence of the photoelectrons.

Interplay of screening and superconductivity in low-dimensional materials

NASA Astrophysics Data System (ADS)

Schönhoff, G.; Rösner, M.; Groenewald, R. E.; Haas, S.; Wehling, T. O.

2016-10-01

A quantitative description of Coulomb interactions is developed for two-dimensional superconducting materials, enabling us to compare intrinsic with external screening effects, such as those due to substrates. Using the example of a doped monolayer of MoS2 embedded in a tunable dielectric environment, we demonstrate that the influence of external screening is limited to a length scale, bounded from below by the effective thickness of the quasi-two-dimensional material and from above by its intrinsic screening length. As a consequence, it is found that unconventional Coulomb-driven superconductivity cannot be induced in MoS2 by tuning the substrate properties alone. Our calculations of the retarded Morel-Anderson Coulomb potential μ* reveal that the Coulomb interactions, renormalized by the reduced layer thickness and the substrate properties, can shift the onset of the electron-phonon driven superconducting phase in monolayer MoS2 but do not significantly affect the critical temperature at optimal doping.

Heteroepitaxy of orientation-patterned nonlinear optical materials

NASA Astrophysics Data System (ADS)

Tassev, Vladimir L.; Vangala, Shivashankar R.; Peterson, Rita D.; Snure, Michael

2018-03-01

We report some recent results on thick heteroepitaxial growth of GaP on GaAs substrates and on orientation-patterned (OP) GaAs templates conducted in a hot-wall horizontal quartz reactor for Hydride Vapor Phase Epitaxy. The growths on the plain substrates resulted in up to 500 μm thick GaP with smooth surface morphology (RMS < 1-2 nm) and high crystalline quality (FWHM = 100-150 arcsec), comparable to the quality of the related homoepitaxial growths of GaP on GaP. Up to 300 μm thick OPGaP quasi-phase matching structures with excellent domain fidelity were also heteroepitaxially grown with high reproducibility on OPGaAs templates in support of frequency conversion laser source development for the mid and longwave infrared. We studied the GaAsxP1-x ternary transition layer that forms between the growing film and the substrate. We also undertook steps to determine some important characteristics of heteroepitaxy such as thickness of the pseudomorphous growth and periodicity of the expected misfit dislocations. The formation of these and some other defects and their distribution within the layer thickness was also investigated. Samples were characterized by Nomarski optical microscopy, transmission optical measurements, transmission electron microscopy, scanning electron microscopy, atomic force microscopy, X-ray diffraction and energy dispersive X-ray spectroscopy. The focus was predominantly on the interface and, more precisely, on what influence the pre-growth surface treatment of the substrate has on the initial and the following stages of growth, as well on the mechanisms of the strain relaxation from the lattice and thermal mismatch between layer and substrate. The efforts to accommodate the growing film to the foreign substrate by engineering an intermediate buffer layer were extended to thick growths of GaAsxP1-x ternary with the idea to combine in one material the best of the nonlinear properties of GaP and GaAs that are strictly relevant to the pursued applications.

Spalling of a Thin Si Layer by Electrodeposit-Assisted Stripping

NASA Astrophysics Data System (ADS)

Kwon, Youngim; Yang, Changyol; Yoon, Sang-Hwa; Um, Han-Don; Lee, Jung-Ho; Yoo, Bongyoung

2013-11-01

A major goal in solar cell research is to reduce the cost of the final module. Reducing the thickness of the crystalline silicon substrate to several tens of micrometers can reduce material costs. In this work, we describe the electrodeposition of a Ni-P alloy, which induces high stress in the silicon substrate at room temperature. The induced stress enables lift-off of the thin-film silicon substrate. After lift-off of the thin Si film, the mother substrate can be reused, reducing material costs. Moreover, the low-temperature process expected to be improved Si substrate quality.

An Al₂O₃ Gating Substrate for the Greater Performance of Field Effect Transistors Based on Two-Dimensional Materials.

PubMed

Yang, Hang; Qin, Shiqiao; Zheng, Xiaoming; Wang, Guang; Tan, Yuan; Peng, Gang; Zhang, Xueao

2017-09-22

We fabricated 70 nm Al₂O₃ gated field effect transistors based on two-dimensional (2D) materials and characterized their optical and electrical properties. Studies show that the optical contrast of monolayer graphene on an Al₂O₃/Si substrate is superior to that on a traditional 300 nm SiO₂/Si substrate (2.4 times). Significantly, the transconductance of monolayer graphene transistors on the Al₂O₃/Si substrate shows an approximately 10-fold increase, due to a smaller dielectric thickness and a higher dielectric constant. Furthermore, this substrate is also suitable for other 2D materials, such as WS₂, and can enhance the transconductance remarkably by 61.3 times. These results demonstrate a new and ideal substrate for the fabrication of 2D materials-based electronic logic devices.

Thick-film nickel-metal-hydride battery based on porous ceramic substrates

NASA Astrophysics Data System (ADS)

Do, Jing-Shan; Yu, Sen-Hao; Cheng, Suh-Fen

Nickel-metal-hydride (Ni-MH) batteries are prepared with thick-film and thin-film technologies based on porous ceramic substrates. The porosity and the mean pore diameter of BP ceramic substrates prepared from the argils increases from 19.81% and 0.0432 μm to 29.81% and 0.224 μm, respectively, upon increasing the ethyl cellulose content in the BP argil from 0 to 0.79%. The pore diameter of Al 2O 3 substrates prepared from Al 2O 3 powder is mainly distributed in the range 0.01-0.5 μm. The distribution of the pore diameters of BP ceramic substrates lies in two ranges, namely: 0.04-2 μm and 10-300 μm. Using BP ceramic plates and Al 2O 3 plates as substrates to fabricate thick-film Ni-MH batteries, the optimal electroactive material utilization in the batteries is 77.0 and 71.1%, respectively. On increasing the screen-printing number for preparing the cathode (Ni(OH) 2) from 1 to 3, the discharge capacity of the thick-film battery increases from 0.2917 to 0.7875 mAh, and the utilization in the battery decreases from 71.0 to 53.0%.

Gauge Factor and Stretchability of Silicon-on-Polymer Strain Gauges

PubMed Central

Yang, Shixuan; Lu, Nanshu

2013-01-01

Strain gauges are widely applied to measure mechanical deformation of structures and specimens. While metallic foil gauges usually have a gauge factor slightly over 2, single crystalline silicon demonstrates intrinsic gauge factors as high as 200. Although silicon is an intrinsically stiff and brittle material, flexible and even stretchable strain gauges have been achieved by integrating thin silicon strips on soft and deformable polymer substrates. To achieve a fundamental understanding of the large variance in gauge factor and stretchability of reported flexible/stretchable silicon-on-polymer strain gauges, finite element and analytically models are established to reveal the effects of the length of the silicon strip, and the thickness and modulus of the polymer substrate. Analytical results for two limiting cases, i.e., infinitely thick substrate and infinitely long strip, have found good agreement with FEM results. We have discovered that strains in silicon resistor can vary by orders of magnitude with different substrate materials whereas strip length or substrate thickness only affects the strain level mildly. While the average strain in silicon reflects the gauge factor, the maximum strain in silicon governs the stretchability of the system. The tradeoff between gauge factor and stretchability of silicon-on-polymer strain gauges has been proposed and discussed. PMID:23881128

Process for manufacture of thick film hydrogen sensors

DOEpatents

Perdieu, Louisa H.

2000-09-09

A thick film process for producing hydrogen sensors capable of sensing down to a one percent concentration of hydrogen in carrier gasses such as argon, nitrogen, and air. The sensor is also suitable to detect hydrogen gas while immersed in transformer oil. The sensor includes a palladium resistance network thick film printed on a substrate, a portion of which network is coated with a protective hydrogen barrier. The process utilizes a sequence of printing of the requisite materials on a non-conductive substrate with firing temperatures at each step which are less than or equal to the temperature at the previous step.

Characterization and study of mechanical and tribological properties on titanium di oxide (TiO2) coated 304L stainless steel

NASA Astrophysics Data System (ADS)

Ghanaraja, S.; Ali, Syed Imran; Ravikumar, K. S.; Likith, P.

2018-04-01

In the present investigation Atmospheric Plasma Spraying (APS) method is selected for coating the materials on 304L Stainless Steel as a substrate material, also called as substrate of Thermal Barrier Coating (TBC) system developed in the present work. Commercially available Ni-Cr metal powder is selected for bond coat and TiO2 powder is selected for Top Coat. The thickness of bond coat is taken as 75 µm where as the top coat thickness is varied as 100 µm, 200 µm and 300 µm. In plasma sprayed coating more attention is given to obtain uniform thickness on the given substrate. The various surface texture parameters of each sample is tested, morphology and coating thickness of above TBC system are studied with the help of SEM and X-Ray Diffraction for phase analysis. Micro-hardness of each layer of coating is measured by using Vicker's diamond indentation and the abrasive wear resistance of each system has been investigated through Pin-on-disc test, at room temperature by using wear and friction tribometer. The coating system possesses good wear resistance and can be used in various applications.

An Al2O3 Gating Substrate for the Greater Performance of Field Effect Transistors Based on Two-Dimensional Materials

PubMed Central

Zheng, Xiaoming; Wang, Guang; Tan, Yuan; Zhang, Xueao

2017-01-01

We fabricated 70 nm Al2O3 gated field effect transistors based on two-dimensional (2D) materials and characterized their optical and electrical properties. Studies show that the optical contrast of monolayer graphene on an Al2O3/Si substrate is superior to that on a traditional 300 nm SiO2/Si substrate (2.4 times). Significantly, the transconductance of monolayer graphene transistors on the Al2O3/Si substrate shows an approximately 10-fold increase, due to a smaller dielectric thickness and a higher dielectric constant. Furthermore, this substrate is also suitable for other 2D materials, such as WS2, and can enhance the transconductance remarkably by 61.3 times. These results demonstrate a new and ideal substrate for the fabrication of 2D materials-based electronic logic devices. PMID:28937619

Growth and characterization of α and β-phase tungsten films on various substrates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Jeong-Seop; Cho, Jaehun; You, Chun-Yeol, E-mail: cyyou@inha.ac.kr

2016-03-15

The growth conditions of tungsten thin films were investigated using various substrates including Si, Si/SiO{sub 2}, GaAs, MgO, and Al{sub 2}O{sub 3}, and recipes were discovered for the optimal growth conditions of thick metastable β-phase tungsten films on Si, GaAs, and Al{sub 2}O{sub 3} substrates, which is an important material in spin orbit torque studies. For the Si/SiO{sub 2} substrate, the crystal phase of the tungsten films was different depending upon the tungsten film thickness, and the transport properties were found to dramatically change with the thickness owing to a change in phase from the α + β phase to the α-phase.more » It is shown that the crystal phase changes are associated with residual stress in the tungsten films and that the resistivity is closely related to the grain sizes.« less

Substrate induced changes in atomically thin 2-dimensional semiconductors: Fundamentals, engineering, and applications

NASA Astrophysics Data System (ADS)

Sun, Yinghui; Wang, Rongming; Liu, Kai

2017-03-01

Substrate has great influences on materials syntheses, properties, and applications. The influences are particularly crucial for atomically thin 2-dimensional (2D) semiconductors. Their thicknesses are less than 1 nm; however, the lateral sizes can reach up to several inches or more. Therefore, these materials must be placed onto a variety of substrates before subsequent post-processing techniques for final electronic or optoelectronic devices. Recent studies reveal that substrates have been employed as ways to modulate the optical, electrical, mechanical, and chemical properties of 2D semiconductors. In this review, we summarize recent progress upon the effects of substrates on properties of 2D semiconductors, mostly focused on 2D transition metal dichalcogenides, through viewpoints of both fundamental physics and device applications. First, we discuss various effects of substrates, including interface strain, charge transfer, dielectric screening, and optical interference. Second, we show the modulation of 2D semiconductors by substrate engineering, including novel substrates (patterned substrates, 2D-material substrates, etc.) and active substrates (phase transition materials, ferroelectric materials, flexible substrates, etc.). Last, we present prospectives and challenges in this research field. This review provides a comprehensive understanding of the substrate effects, and may inspire new ideas of novel 2D devices based on substrate engineering.

GaAsPN-based PIN solar cells MBE-grown on GaP substrates: toward the III-V/Si tandem solar cell

NASA Astrophysics Data System (ADS)

Da Silva, M.; Almosni, S.; Cornet, C.; Létoublon, A.; Levallois, C.; Rale, P.; Lombez, L.; Guillemoles, J.-F.; Durand, O.

2015-03-01

GaAsPN semiconductors are promising material for the elaboration of high efficiencies tandem solar cells on silicon substrates. GaAsPN diluted nitride alloy is studied as the top junction material due to its perfect lattice matching with the Si substrate and its ideal bandgap energy allowing a perfect current matching with the Si bottom cell. We review our recent progress in materials development of the GaAsPN alloy and our recent studies of some of the different building blocks toward the elaboration of a PIN solar cell. A lattice matched (with a GaP(001) substrate, as a first step toward the elaboration on a Si substrate) 1μm-thick GaAsPN alloy has been grown by MBE. After a post-growth annealing step, this alloy displays a strong absorption around 1.8-1.9 eV, and efficient photoluminescence at room temperature suitable for the elaboration of the targeted solar cell top junction. Early stage GaAsPN PIN solar cells prototypes have been grown on GaP (001) substrates, with 2 different absorber thicknesses (1μm and 0.3μm). The external quantum efficiencies and the I-V curves show that carriers have been extracted from the GaAsPN alloy absorbers, with an open-circuit voltage of 1.18 V, while displaying low short circuit currents meaning that the GaAsPN structural properties needs a further optimization. A better carrier extraction has been observed with the absorber displaying the smallest thickness, which is coherent with a low carriers diffusion length in our GaAsPN compound. Considering all the pathways for improvement, the efficiency obtained under AM1.5G is however promising.

Dust coatings on basaltic rocks and implications for thermal infrared spectroscopy of Mars

USGS Publications Warehouse

Johnson, J. R.; Christensen, P.R.; Lucey, P.G.

2002-01-01

Thin coatings of atmospherically deposited dust can mask the spectral characteristics of underlying surfaces on Mars from the visible to thermal infrared wavelengths, making identification of substrate and coating mineralogy difficult from lander and orbiter spectrometer data. To study the spectral effects of dust coatings, we acquired thermal emission and hemispherical reflectance spectra (5-25 μm; 2000-400 cm-1) of basaltic andesite coated with different thicknesses of air fall-deposited palagonitic soils, fine-grained ceramic clay powders, and terrestrial loess. The results show that thin coatings (10-20 μm) reduce the spectral contrast of the rock substrate substantially, consistent with previous work. This contrast reduction continues linearly with increasing coating thickness until a "saturation thickness" is reached, after which little further change is observed. The saturation thickness of the spectrally flat palagonite coatings is ~100-120 μm, whereas that for coatings with higher spectral contrast is only ~50-75 μm. Spectral differences among coated and uncoated samples correlate with measured coating thicknesses in a quadratic manner, whereas correlations with estimated surface area coverage are better fit by linear functions. Linear mixture modeling of coated samples using the rock substrate and coating materials as end-members is also consistent with their measured coating thicknesses and areal coverage. A comparison of ratios of Thermal Emission Spectrometer (TES) spectra of dark and bright intracrater and windstreak deposits associated with Radau crater suggests that the dark windstreak material may be coated with as much as 90% areal coverage of palagonitic dust. The data presented here also will help improve interpretations of upcoming mini-TES and Thermal Emission Imaging System (THEMIS) observations of coated Mars surface materials.

Antireflection coatings with SiOx-TiO2 multilayer structures

NASA Astrophysics Data System (ADS)

Lu, Jong-Hong; Luo, Jen-Wei; Chuang, Shiou-Ruei; Chen, Bo-Ying

2014-11-01

In this study, we used SiOx-TiO2 multilayer antireflective coatings to achieve optical average transmittances of 94.93 and 98.07% for one-sided and double-sided coatings on a glass substrate, respectively. A SiOx film was employed as the material with a low refractive index and a TiO2 film as the material with a high refractive index. Results showed that when any layer thickness of the SiOx-TiO2 nano-multilayer (NML) structure is much less than the wavelength of visible light, the SiOx-TiO2 thickness ratio can be used to adjust the optical refractive index of the entire NML film. In this study, we produced dense antireflective coatings of three layers (SiOx, TiO2, and SiOx-TiO2 NML/glass substrate) and four layers (SiOx, TiO2, SiOx, and TiO2/glass substrate) with film thicknesses and refractive indices controlled by reactive magnetron sputtering. Thermal treatment at 600 °C in an air atmosphere was also shown to reduce the absorption of visible light, resolving the issue of degraded transparency caused by increasing sputtering speed. The microhardness of the antireflective film was 8.44 GPa, similar to that of the glass substrate. Process window analysis demonstrated the feasibility of the antireflective coating process window from an engineering standpoint. The thickness of the film deviated by less than 10% from the ideal thickness, corresponding to a 98% transmittance range, and the simulation and experimental results were relatively consistent.

Radiative transfer modeling of dust-coated Pancam calibration target materials: Laboratory visible/near-infrared spectrogoniometry

USGS Publications Warehouse

Johnson, J. R.; Sohl-Dickstein, J.; Grundy, W.M.; Arvidson, R. E.; Bell, J.F.; Christensen, P.R.; Graff, T.; Guinness, E.A.; Kinch, K.; Morris, Robert; Shepard, M.K.

2006-01-01

Laboratory visible/near-infrared multispectral observations of Mars Exploration Rover Pancam calibration target materials coated with different thicknesses of Mars spectral analog dust were acquired under variable illumination geometries using the Bloomsburg University Goniometer. The data were fit with a two-layer radiative transfer model that combines a Hapke formulation for the dust with measured values of the substrate interpolated using a He-Torrance approach. We first determined the single-scattering albedo, phase function, opposition effect width, and amplitude for the dust using the entire data set (six coating thicknesses, three substrates, four wavelengths, and phase angles 3??-117??). The dust exhibited single-scattering albedo values similar to other Mars analog soils and to Mars Pathfinder dust and a dominantly forward scattering behavior whose scattering lobe became narrower at longer wavelengths. Opacity values for each dust thickness corresponded well to those predicted from the particles sizes of the Mars analog dust. We then restricted the number of substrates, dust thicknesses, and incidence angles input to the model. The results suggest that the dust properties are best characterized when using substrates whose reflectances are brighter and darker than those of the deposited dust and data that span a wide range of dust thicknesses. The model also determined the dust photometric properties relatively well despite limitations placed on the range of incidence angles. The model presented here will help determine the photometric properties of dust deposited on the MER rovers and to track the multiple episodes of dust deposition and erosion that have occurred at both landing sites. Copyright 2006 by the American Geophysical Union.

Apparatus for externally controlled closed-loop feedback digital epitaxy

DOEpatents

Eres, D.; Sharp, J.W.

1996-07-30

A method and apparatus for digital epitaxy are disclosed. The apparatus includes a pulsed gas delivery assembly that supplies gaseous material to a substrate to form an adsorption layer of the gaseous material on the substrate. Structure is provided for measuring the isothermal desorption spectrum of the growth surface to monitor the active sites which are available for adsorption. The vacuum chamber housing the substrate facilitates evacuation of the gaseous material from the area adjacent the substrate following exposure. In use, digital epitaxy is achieved by exposing a substrate to a pulse of gaseous material to form an adsorption layer of the material on the substrate. The active sites on the substrate are monitored during the formation of the adsorption layer to determine if all the active sites have been filled. Once the active sites have been filled on the growth surface of the substrate, the pulse of gaseous material is terminated. The unreacted portion of the gas pulse is evacuated by continuous pumping. Subsequently, a second pulse is applied when availability of active sites is determined by studying the isothermal desorption spectrum. These steps are repeated until a thin film of sufficient thickness is produced. 5 figs.

Apparatus for externally controlled closed-loop feedback digital epitaxy

DOEpatents

Eres, Djula; Sharp, Jeffrey W.

1996-01-01

A method and apparatus for digital epitaxy. The apparatus includes a pulsed gas delivery assembly that supplies gaseous material to a substrate to form an adsorption layer of the gaseous material on the substrate. Structure is provided for measuring the isothermal desorption spectrum of the growth surface to monitor the active sites which are available for adsorption. The vacuum chamber housing the substrate facilitates evacuation of the gaseous material from the area adjacent the substrate following exposure. In use, digital epitaxy is achieved by exposing a substrate to a pulse of gaseous material to form an adsorption layer of the material on the substrate. The active sites on the substrate are monitored during the formation of the adsorption layer to determine if all the active sites have been filled. Once the active sites have been filled on the growth surface of the substrate, the pulse of gaseous material is terminated. The unreacted portion of the gas pulse is evacuated by continuous pumping. Subsequently, a second pulse is applied when availability of active sites is determined by studying the isothermal desorption spectrum. These steps are repeated until a thin film of sufficient thickness is produced.

Method of digital epitaxy by externally controlled closed-loop feedback

DOEpatents

Eres, D.; Sharp, J.W.

1994-07-19

A method and apparatus for digital epitaxy are disclosed. The apparatus includes a pulsed gas delivery assembly that supplies gaseous material to a substrate to form an adsorption layer of the gaseous material on the substrate. Structure is provided for measuring the isothermal desorption spectrum of the growth surface to monitor the active sites which are available for adsorption. The vacuum chamber housing the substrate facilitates evacuation of the gaseous material from the area adjacent the substrate following exposure. In use, digital epitaxy is achieved by exposing a substrate to a pulse of gaseous material to form an adsorption layer of the material on the substrate. The active sites on the substrate are monitored during the formation of the adsorption layer to determine if all the active sites have been filled. Once the active sites have been filled on the growth surface of the substrate, the pulse of gaseous material is terminated. The unreacted portion of the gas pulse is evacuated by continuous pumping. Subsequently, a second pulse is applied when availability of active sites is determined by studying the isothermal desorption spectrum. These steps are repeated until a thin film of sufficient thickness is produced. 4 figs.

Method of digital epilaxy by externally controlled closed-loop feedback

DOEpatents

Eres, Djula; Sharp, Jeffrey W.

1994-01-01

A method and apparatus for digital epitaxy. The apparatus includes a pulsed gas delivery assembly that supplies gaseous material to a substrate to form an adsorption layer of the gaseous material on the substrate. Structure is provided for measuring the isothermal desorption spectrum of the growth surface to monitor the active sites which are available for adsorption. The vacuum chamber housing the substrate facilitates evacuation of the gaseous material from the area adjacent the substrate following exposure. In use, digital epitaxy is achieved by exposing a substrate to a pulse of gaseous material to form an adsorption layer of the material on the substrate. The active sites on the substrate are monitored during the formation of the adsorption layer to determine if all the active sites have been filled. Once the active sites have been filled on the growth surface of the substrate, the pulse of gaseous material is terminated. The unreacted portion of the gas pulse is evacuated by continuous pumping. Subsequently, a second pulse is applied when availability of active sites is determined by studying the isothermal desorption spectrum. These steps are repeated until a thin film of sufficient thickness is produced.

Thickness dependent properties of CMR Manganite thin films on lattice mismatched substrates: Distinguishing Strain and Interface Effects

NASA Astrophysics Data System (ADS)

Davidson, Anthony, III; Kolagani, Rajeswari; Bacharova, Ellisaveta; Yong, Grace; Smolyaninova, Vera; Schaefer, David; Mundle, Rajeh

2007-03-01

Epitaxial thin films of CMR manganite materials have been known to show thickness dependent electrical and magnetic properties on lattice mismatched substrates. Below a critical thickness, insulator-metal transition is suppressed. These effects have been largely attributed to the role of bi-axial lattice mismatch strain. Our recent results of epitaxial thin films of La0.67Ca0.33MnO3 (LCMO) on two substrates with varying degrees of compressive lattice mismatch indicate that, in addition to the effect of lattice mismatch strain, the thickness dependence of the properties are influenced by other factors possibly related to the nature of the film substrate interface and defects such as twin boundaries. We have compared the properties of LCMO films on (100) oriented LaAlO3 and (001) oriented NdCaAlO4 both of which induce compressive bi-axial strain. Interestingly, the suppression of the insulator-metal transition is less in films on NCAO which has a larger lattice mismatch. We will present results correlating the electrical and magneto transport properties with the structure and morphology of the films.

Role of geometric parameters in electrical measurements of insulating thin films deposited on a conductive substrate

NASA Astrophysics Data System (ADS)

Kumar, S.; Gerhardt, R. A.

2012-03-01

The effects of film thickness, electrode size and substrate thickness on the impedance parameters of alternating frequency dielectric measurements of insulating thin films deposited on conductive substrates were studied through parametric finite-element simulations. The quasi-static forms of Maxwell's electromagnetic equations in a time harmonic mode were solved using COMSOL Multiphysics® for several types of 2D models (linear and axisymmetric). The full 2D model deals with a configuration in which the impedance is measured between two surface electrodes on top of a film deposited on a conductive substrate. For the simplified 2D models, the conductive substrate is ignored and the two electrodes are placed on the top and bottom of the film. By comparing the full model and the simplified models, approximations and generalizations are deduced. For highly insulating films, such as the case of insulating SiO2 films on a conducting Si substrate, even the simplified models predict accurate capacitance values at all frequencies. However, the edge effects on the capacitance are found to be significant when the film thickness increases and/or the top electrode contact size decreases. The thickness of the substrate affects predominantly the resistive components of the dielectric response while having no significant effect on the capacitive components. Changing the electrode contact size or the film thickness determines the specific values of the measured resistance or capacitance while the material time constant remains the same, and thus this affects the frequency dependence that is able to be detected. This work highlights the importance of keeping in mind the film thickness and electrode contact size for the correct interpretation of the measured dielectric properties of micro/nanoscale structures that are often investigated using nanoscale capacitance measurements.

Bimorph material/structure designs for high sensitivity flexible surface acoustic wave temperature sensors.

PubMed

Tao, R; Hasan, S A; Wang, H Z; Zhou, J; Luo, J T; McHale, G; Gibson, D; Canyelles-Pericas, P; Cooke, M D; Wood, D; Liu, Y; Wu, Q; Ng, W P; Franke, T; Fu, Y Q

2018-06-13

A fundamental challenge for surface acoustic wave (SAW) temperature sensors is the detection of small temperature changes on non-planar, often curved, surfaces. In this work, we present a new design methodology for SAW devices based on flexible substrate and bimorph material/structures, which can maximize the temperature coefficient of frequency (TCF). We performed finite element analysis simulations and obtained theoretical TCF values for SAW sensors made of ZnO thin films (~5 μm thick) coated aluminum (Al) foil and Al plate substrates with thicknesses varied from 1 to 1600 μm. Based on the simulation results, SAW devices with selected Al foil or plate thicknesses were fabricated. The experimentally measured TCF values were in excellent agreements with the simulation results. A normalized wavelength parameter (e.g., the ratio between wavelength and sample thickness, λ/h) was applied to successfully describe changes in the TCF values, and the TCF readings of the ZnO/Al SAW devices showed dramatic increases when the normalized wavelength λ/h was larger than 1. Using this design approach, we obtained the highest reported TCF value of -760 ppm/K for a SAW device made of ZnO thin film coated on Al foils (50 μm thick), thereby enabling low cost temperature sensor applications to be realized on flexible substrates.

Method of manufacturing a heat pipe wick with structural enhancement

DOEpatents

Andraka, Charles E [Albuquerque, NM; Adkins, Douglas R [Albuquerque, NM; Moreno, James B [Albuquerque, NM; Rawlinson, K Scott [Albuquerque, NM; Showalter, Steven K [Albuquerque, NM; Moss, Timothy A [Albuquerque, NM

2006-10-24

Heat pipe wick structure wherein a stout sheet of perforated material overlays a high performance wick material such as stainless steel felt affixed to a substrate. The inventive structure provides a good flow path for working fluid while maintaining durability and structural stability independent of the structure (or lack of structure) associated with the wick material. In one described embodiment, a wick of randomly laid .about.8 micron thickness stainless steel fibers is sintered to a metal substrate and a perforated metal overlay.

Heat pipe wick with structural enhancement

DOEpatents

Andraka, Charles E.; Adkins, Douglas R.; Moreno, James B.; Rawlinson, K. Scott; Showalter, Steven K.; Moss, Timothy A.

2003-11-18

Heat pipe wick structure wherein a stout sheet of perforated material overlays a high performance wick material such as stainless steel felt affixed to a substrate. The inventive structure provides a good flow path for working fluid while maintaining durability and structural stability independent of the structure (or lack of structure) associated with the wick material. In one described embodiment, a wick of randomly laid .about.8 micron thickness stainless steel fibers is sintered to a metal substrate and a perforated metal overlay.

Method for fabricating an ultra-low expansion mask blank having a crystalline silicon layer

DOEpatents

Cardinale, Gregory F.

2002-01-01

A method for fabricating masks for extreme ultraviolet lithography (EUVL) using Ultra-Low Expansion (ULE) substrates and crystalline silicon. ULE substrates are required for the necessary thermal management in EUVL mask blanks, and defect detection and classification have been obtained using crystalline silicon substrate materials. Thus, this method provides the advantages for both the ULE substrate and the crystalline silicon in an Extreme Ultra-Violet (EUV) mask blank. The method is carried out by bonding a crystalline silicon wafer or member to a ULE wafer or substrate and thinning the silicon to produce a 5-10 .mu.m thick crystalline silicon layer on the surface of the ULE substrate. The thinning of the crystalline silicon may be carried out, for example, by chemical mechanical polishing and if necessary or desired, oxidizing the silicon followed by etching to the desired thickness of the silicon.

Room temperature impact deposition of ceramic by laser shock wave

NASA Astrophysics Data System (ADS)

Jinno, Kengo; Tsumori, Fujio

2018-06-01

In this paper, a direct fine patterning of ceramics at room temperature combining 2 kinds of laser microfabrication methods is proposed. The first method is called laser-induced forward transfer and the other is called laser shock imprinting. In the proposed method, a powder material is deposited by a laser shock wave; therefore, the process is applicable to a low-melting-point material, such as a polymer substrate. In the process, a carbon layer plays an important role in the ablation by laser irradiation to generate a shock wave. This shock wave gives high shock energy to the ceramic particles, and the particles would be deposited and solidified by high-speed collision with the substrate. In this study, we performed deposition experiments by changing the thickness of the carbon layer, laser energy, thickness of the alumina layer, and gap substrates. We compared the ceramic deposits after each experiment.

Laser-launched flyers with organic working fluids

NASA Astrophysics Data System (ADS)

Mulford, Roberta; Swift, Damian

2003-10-01

The TRIDENT laser has been used to launch flyers by depositing IR energy in a thin layer of material - the working fluid - sandwiched between the flyer and a transparent substrate. We have investigated the use of working fluids based on organics, chosen as they are quite efficient absorbers of IR energy and should also convert heat to mechanical work more efficiently than materials such as carbon. A thermodynamically complete equation of state was developed for one of the fluids investigated experimentally - a carbohydrate solution - by chemical equilibrium calculations using the CHEETAH program. Continuum mechanics simulations were made of the flyer launch process, modeling the effect of the laser as energy deposition in the working fluid, and taking into account the compression and recoil of the substrate. We compare the simulations with a range of experiments and demonstrate the optimization of substrate and fluid thickness for a given flyer thickness and speed.

Ultrathin (<1 μm) Substrate-Free Flexible Photodetector on Quantum Dot-Nanocellulose Paper

PubMed Central

Wu, Jingda; Lin, Lih Y.

2017-01-01

Conventional approaches to flexible optoelectronic devices typically require depositing the active materials on external substrates. This is mostly due to the weak bonding between individual molecules or nanocrystals in the active materials, which prevents sustaining a freestanding thin film. Herein we demonstrate an ultrathin freestanding ZnO quantum dot (QD) active layer with nanocellulose structuring, and its corresponding device fabrication method to achieve substrate-free flexible optoelectronic devices. The ultrathin ZnO QD-nanocellulose composite is obtained by hydrogel transfer printing and solvent-exchange processes to overcome the water capillary force which is detrimental to achieving freestanding thin films. We achieved an active nanocellulose paper with ~550 nm thickness, and >91% transparency in the visible wavelength range. The film retains the photoconductive and photoluminescent properties of ZnO QDs and is applied towards substrate-free Schottky photodetector applications. The device has an overall thickness of ~670 nm, which is the thinnest freestanding optoelectronic device to date, to the best of our knowledge, and functions as a self-powered visible-blind ultraviolet photodetector. This platform can be readily applied to other nano materials as well as other optoelectronic device applications. PMID:28266651

Patterned Growth of Carbon Nanotubes or Nanofibers

NASA Technical Reports Server (NTRS)

Delzeit, Lance D.

2004-01-01

A method and apparatus for the growth of carbon nanotubes or nanofibers in a desired pattern has been invented. The essence of the method is to grow the nanotubes or nanofibers by chemical vapor deposition (CVD) onto a patterned catalyst supported by a substrate. The figure schematically depicts salient aspects of the method and apparatus in a typical application. A substrate is placed in a chamber that contains both ion-beam sputtering and CVD equipment. The substrate can be made of any of a variety of materials that include several forms of silicon or carbon, and selected polymers, metals, ceramics, and even some natural minerals and similar materials. Optionally, the substrate is first coated with a noncatalytic metal layer (which could be a single layer or could comprise multiple different sublayers) by ion-beam sputtering. The choice of metal(s) and thickness(es) of the first layer (if any) and its sublayers (if any) depends on the chemical and electrical properties required for subsequent deposition of the catalyst and the subsequent CVD of the carbon nanotubes. A typical first-sublayer metal is Pt, Pd, Cr, Mo, Ti, W, or an alloy of two or more of these elements. A typical metal for the second sublayer or for an undivided first layer is Al at a thickness .1 nm or Ir at a thickness .5 nm. Proper choice of the metal for a second sublayer of a first layer makes it possible to use a catalyst that is chemically incompatible with the substrate. In the next step, a mask having holes in the desired pattern is placed over the coated substrate. The catalyst is then deposited on the coated substrate by ion-beam sputtering through the mask. Optionally, the catalyst could be deposited by a technique other than sputtering and/or patterned by use of photolithography, electron- beam lithography, or another suitable technique. The catalytic metal can be Fe, Co, Ni, or an alloy of two or more of these elements, deposited to a typical thickness in the range from 0.1 to 20 nm.

The Effect of Carrier Properties on the Ballistic Processing of Sn-0.7 Cu Thick Films

NASA Astrophysics Data System (ADS)

Hille, David M.

The need for metallic films has increased since the creation of electronic components. The continued miniaturization of systems and components has led to a greater demand for both thick and thin films, especially in the technology field. Computers, hand held devices, and solar cells are a few of the multitudes of uses for these films. This thesis investigates a novel additive manufacturing process known as Ballistic Manufacturing (BM), invented at the Advanced Materials Processing Lab (AMPL) at San Diego State University. Lead free solder (Tin (Sn)-0.7%Copper (Cu)) was chosen as the testing material due to its low melting temperature. The effects of varying thermal conductivity via the change in carrier material type, the effect of raising substrate temperature, and surface finish differences were investigated. An increase in thermal conductivity resulted in an increase in film thickness and decrease in cell size. As substrate temperature was raised, film thickness decreased, while cell size decreased. Surface finish provided a proof of concept to the transfer of substrate features to the resultant film surface. Evaluation of dendritic microstructures led to relative cooling rates reflective of changes in parameters. The mechanical behavior was also investigated using tensile tests to determine stress-stain relationships and measure elastic modulus. With the current work of this thesis, and previous work by Cavero and Stewart, Ballistic Manufacturing is proven to be an alternative method in the production of metallic films.

Masks For Deposition Of Aspherical Optical Surfaces

NASA Technical Reports Server (NTRS)

Rogers, John R.; Martin, John D.

1992-01-01

Masks of improved design developed for use in fabrication of aspherical, rotationally symmetrical surfaces of mirrors, lenses, and lens molds by evaporative deposition onto rotating substrates. In deposition chamber, source and mask aligned with axis of rotation of substrate. Mask shadows source of rotating substrate. Azimuthal opening (as function of radius) in mask proportional to desired thickness (as function of radius) to which material deposited on substrate. Combination of improved masks and modern coating chambers provides optical surfaces comparable or superior to those produced by conventional polishing, computer-controlled polishing, replication from polished molds, and diamond turning, at less cost in material, labor, and capital expense.

Applying a biodeposition layer to increase the bond of a repair mortar on a mortar substrate.

PubMed

Snoeck, D; Wang, J; Bentz, D P; De Belie, N

2018-02-01

One of the major concerns in infrastructure repair is a sufficient bond between the substrate and the repair material, especially for the long-term performance and durability of the repaired structure. In this study, the bond of the repair material on the mortar substrate is promoted via the biodeposition of a calcium carbonate layer by a ureolytic bacterium. X-ray diffraction and scanning electron microscopy were used to examine the interfaces between the repair material and the substrate, as well as the polymorph of the deposited calcium carbonate. The approximately 50 μm thick biodeposition film on the mortar surface mostly consisted of calcite and vaterite. Both the repair material and the substrate tended to show a good adherence to that layer. The bond, as assessed by slant shear specimen testing, was improved by the presence of the biodeposition layer. A further increase was found when engineering the substrate surface using a structured pattern layer of biodeposition.

Effect of layer thickness on the properties of nickel thermal sprayed steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nurisna, Zuhri, E-mail: zuhri-nurisna@yahoo.co.id; Triyono,, E-mail: triyonomesin@uns.ac.id; Muhayat, Nurul, E-mail: nurulmuhayat@staff.uns.ac.id

Thermal arc spray nickel coating is widely used for decorative and functional applications, by improving corrosion resistance, wear resistance, heat resistence or by modifying other properties of the coated materials. There are several properties have been studied. Layer thickness of nickel thermal sprayed steel may be make harder the substrate surface. In this study, the effect of layer thickness of nickel thermal sprayed steel has been investigated. The rectangular substrate specimens were coated by Ni–5 wt.% Al using wire arc spray method. The thickness of coating layers were in range from 0.4 to 1.0 mm. Different thickness of coating layers weremore » conducted to investigate their effect on hardness and morphology. The coating layer was examined by using microvickers and scanning electron microscope with EDX attachment. Generally, the hardness at the interface increased with increasing thickness of coating layers for all specimens due to higher heat input during spraying process. Morphology analysis result that during spraying process aluminum would react with surrounding oxygen and form aluminum oxide at outer surface of splat. Moreover, porosity was formed in coating layers. However, presence porosity is not related to thickness of coating material. The thicker coating layer resulted highesr of hardness and bond strength.« less

Impact of layer and substrate properties on the surface acoustic wave velocity in scandium doped aluminum nitride based SAW devices on sapphire

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gillinger, M., E-mail: manuel.gillinger@tuwien.ac.at; Knobloch, T.; Schneider, M.

2016-06-06

This paper investigates the performance of surface acoustic wave (SAW) devices consisting of reactively sputter deposited scandium doped aluminum nitride (Sc{sub x}Al{sub 1-x}N) thin films as piezoelectric layers on sapphire substrates for wireless sensor or for RF-MEMS applications. To investigate the influence of piezoelectric film thickness on the device properties, samples with thickness ranging from 500 nm up to 3000 nm are fabricated. S{sub 21} measurements and simulations demonstrate that the phase velocity is predominantly influenced by the mass density of the electrode material rather than by the thickness of the piezoelectric film. Additionally, the wave propagation direction is varied by rotatingmore » the interdigital transducer structures with respect to the crystal orientation of the substrate. The phase velocity is about 2.5% higher for a-direction compared to m-direction of the sapphire substrate, which is in excellent agreement with the difference in the anisotropic Young's modulus of the substrate corresponding to these directions.« less

Profilometry of thin films on rough substrates by Raman spectroscopy

PubMed Central

Ledinský, Martin; Paviet-Salomon, Bertrand; Vetushka, Aliaksei; Geissbühler, Jonas; Tomasi, Andrea; Despeisse, Matthieu; De Wolf , Stefaan; Ballif , Christophe; Fejfar, Antonín

2016-01-01

Thin, light-absorbing films attenuate the Raman signal of underlying substrates. In this article, we exploit this phenomenon to develop a contactless thickness profiling method for thin films deposited on rough substrates. We demonstrate this technique by probing profiles of thin amorphous silicon stripes deposited on rough crystalline silicon surfaces, which is a structure exploited in high-efficiency silicon heterojunction solar cells. Our spatially-resolved Raman measurements enable the thickness mapping of amorphous silicon over the whole active area of test solar cells with very high precision; the thickness detection limit is well below 1 nm and the spatial resolution is down to 500 nm, limited only by the optical resolution. We also discuss the wider applicability of this technique for the characterization of thin layers prepared on Raman/photoluminescence-active substrates, as well as its use for single-layer counting in multilayer 2D materials such as graphene, MoS2 and WS2. PMID:27922033

Direct laser metal deposition of WC/Co/Cr powder by means of the functionally graded materials strategy

NASA Astrophysics Data System (ADS)

Angelastro, A.; Campanelli, S. L.

2017-12-01

One of the many applications of direct laser metal deposition (DLMD) is the realization of multilayer thick coatings having particular mechanical characteristics, such as high hardness. The objective of this work was to obtain a thick, very hard and wear resistant coating, containing a high percentage of tungsten carbide (WC), on an AISI 304 stainless steel substrate. In order to achieve this result, a tungsten carbide-cobalt-chrome (WC/Co/Cr) powder was processed by the DLMD method. WC/Co/Cr is a composite widely used as a wear-resistant material for cutting tools, molds, coatings and other severe applications. Because of its high hardness, poor ductility and low thermal expansion coefficient, depositing this material directly on the stainless steel substrate is very difficult. In order to overcome this problem, the strategy of functionally graded materials (FGM) was used. Colmonoy 227-F nickel alloy was chosen for this purpose in order to generate a mixture with the WC/Co/Cr powder. Four different materials were deposited, layer by layer, by mixing Colmonoy 227-F with an increasing amount of WC/Co/Cr powders, until obtaining a thick surface coating with a maximum amount of WC of 77.4 wt%. For each powder mixture, a mathematical model was applied to calculate optimal values of translation speed and overlap percentages. A metallographic examination was performed in order to detect macro- and micro-structures of the different materials. Finally, Vickers micro-hardness was measured at various locations along the transverse section to appreciate the gradual increase of the FGM hardness, starting from the substrate and culminating at the top surface of the last deposited material.

Method for making thick and/or thin film

DOEpatents

Pham, Ai Quoc; Glass, Robert S.

2004-11-02

A method to make thick or thin films a very low cost. The method is generally similar to the conventional tape casting techniques while being more flexible and versatile. The invention involves preparing a slip (solution) of desired material and including solvents such as ethanol and an appropriate dispersant to prevent agglomeration. The slip is then sprayed on a substrate to be coated using an atomizer which spreads the slip in a fine mist. Upon hitting the substrate, the solvent evaporates, leaving a green tape containing the powder and other additives, whereafter the tape may be punctured, cut, and heated for the desired application. The tape thickness can vary from about 1 .mu.m upward.

Controlling the shapes of coated silicon substrates via magnetic fields, a progress report

NASA Astrophysics Data System (ADS)

Ulmer, Melville P.; Coppejans, Rocco; Buchholz, David B.; Cao, Jian; Wang, Xiaoli; Mercado, Alejandro M.; Qian, Jun; Assoufid, Lahsen; O'Donnell, Allison E.; Condron, Kyle S.; Harpt, Benjamin E.

2017-08-01

We describe our progress in developing a method for correcting residual figure errors in X-ray mirrors. The technology has applications to both synchrotron radiation beamlines and X-ray astronomy. Our concept is to develop mirrors that are on the order of a millimeter thick. A magnetic smart material (MSM) is deposited onto the mirror substrate (silicon) and coated with a magnetically hard material. The shape of the mirror can be controlled by applying an external magnetic field to the mirror. This causes the MSM to expand or contract, thereby applying a magnetostrictive stress to the mirror and changing its shape. The shape change is maintained after the field has been removed by the magnetic hard material, which retains part of the field and prevents the MSM from relaxing. Here we present the results of shaping 200 µm thick silicon (100) 14 × 2 mm cantilevers and 50 × 50 × 0.1 mm substrates. We demonstrate that not only can a sizable deflection be created, but it can also be retained for ˜ 60 hours.

Bio-inspired direct patterning functional nanothin microlines: controllable liquid transfer.

PubMed

Wang, Qianbin; Meng, Qingan; Wang, Pengwei; Liu, Huan; Jiang, Lei

2015-04-28

Developing a general and low-cost strategy that enables direct patterning of microlines with nanometer thickness from versatile liquid-phase functional materials and precise positioning of them on various substrates remains a challenge. Herein, with inspiration from the oriental wisdom to control ink transfer by Chinese brushes, we developed a facile and general writing strategy to directly pattern various functional microlines with homogeneous distribution and nanometer-scale thickness. It is demonstrated that the width and thickness of the microlines could be well-controlled by tuning the writing method, providing guidance for the adaptation of this technique to various systems. It is also shown that various functional liquid-phase materials, such as quantum dots, small molecules, polymers, and suspensions of nanoparticles, could directly write on the substrates with intrinsic physicochemical properties well-preserved. Moreover, this technique enabled direct patterning of liquid-phase materials on certain microdomains, even in multiple layered style, thus a microdomain localized chemical reaction and the patterned surface chemical modification were enabled. This bio-inspired direct writing device will shed light on the template-free printing of various functional micropatterns, as well as the integrated functional microdevices.

High-throughput characterization of film thickness in thin film materials libraries by digital holographic microscopy.

PubMed

Lai, Yiu Wai; Krause, Michael; Savan, Alan; Thienhaus, Sigurd; Koukourakis, Nektarios; Hofmann, Martin R; Ludwig, Alfred

2011-10-01

A high-throughput characterization technique based on digital holography for mapping film thickness in thin-film materials libraries was developed. Digital holographic microscopy is used for fully automatic measurements of the thickness of patterned films with nanometer resolution. The method has several significant advantages over conventional stylus profilometry: it is contactless and fast, substrate bending is compensated, and the experimental setup is simple. Patterned films prepared by different combinatorial thin-film approaches were characterized to investigate and demonstrate this method. The results show that this technique is valuable for the quick, reliable and high-throughput determination of the film thickness distribution in combinatorial materials research. Importantly, it can also be applied to thin films that have been structured by shadow masking.

Realistic absorption coefficient of ultrathin films

NASA Astrophysics Data System (ADS)

Cesaria, M.; Caricato, A. P.; Martino, M.

2012-10-01

Both a theoretical algorithm and an experimental procedure are discussed of a new route to determine the absorption/scattering properties of thin films deposited on transparent substrates. Notably, the non-measurable contribution of the film-substrate interface is inherently accounted for. While the experimental procedure exploits only measurable spectra combined according to a very simple algorithm, the theoretical derivation does not require numerical handling of the acquired spectra or any assumption on the film homogeneity and substrate thickness. The film absorption response is estimated by subtracting the measured absorption spectrum of the bare substrate from that of the film on the substrate structure but in a non-straightforward way. In fact, an assumption about the absorption profile of the overall structure is introduced and a corrective factor accounting for the relative film-to-substrate thickness. The method is tested on films of a well known material (ITO) as a function of the film structural quality and influence of the film-substrate interface, both deliberately changed by thickness tuning and doping. Results are found fully consistent with information obtained by standard optical analysis and band gap values reported in the literature. Additionally, comparison with a conventional method demonstrates that our route is generally more accurate even if particularly suited for very thin films.

Effect of thickness on optoelectrical properties of Nb-doped indium tin oxide thin films deposited by RF magnetron sputtering

NASA Astrophysics Data System (ADS)

Li, Shi-na; Ma, Rui-xin; Ma, Chun-hong; Li, Dong-ran; Xiao, Yu-qin; He, Liang-wei; Zhu, Hong-min

2013-05-01

Niobium-doped indium tin oxide (ITO:Nb) thin films are prepared on glass substrates with various film thicknesses by radio frequency (RF) magnetron sputtering from one piece of ceramic target material. The effects of thickness (60-360 nm) on the structural, electrical and optical properties of ITO: Nb films are investigated by means of X-ray diffraction (XRD), ultraviolet (UV)-visible spectroscopy, and electrical measurements. XRD patterns show the highly oriented (400) direction. The lowest resistivity of the films without any heat treatment is 3.1×10-4Ω·cm-1, and the resistivity decreases with the increase of substrate temperature. The highest Hall mobility and carrier concentration are 17.6 N·S and 1.36×1021 cm-3, respectively. Band gap energy of the films depends on substrate temperature, which varies from 3.48 eV to 3.62 eV.

Polymer-coated compliant receivers for intact laser-induced forward transfer of thin films: experimental results and modelling

NASA Astrophysics Data System (ADS)

Feinaeugle, Matthias; Horak, Peter; Sones, Collin L.; Lippert, Thomas; Eason, Rob W.

2014-09-01

In this study, we investigate both experimentally and numerically laser-induced forward transfer (LIFT) of thin films to determine the role of a thin polymer layer coating the receiver with the aim of modifying the rate of deceleration and reduction of material stress preventing intact material transfer. A numerical model of the impact phase during LIFT shows that such a layer reduces the modelled stress. The evolution of stress within the transferred deposit and the substrate as a function of the thickness of the polymer layer, the transfer velocity and the elastic properties of the polymer are evaluated. The functionality of the polymer layer is verified experimentally by LIFT printing intact 1- m-thick bismuth telluride films and polymeric light-emitting diode pads onto a layer of 12-m-thick polydimethylsiloxane and 50-nm-thick poly(3,4-ethylenedioxythiophene) blended with poly(styrenesulfonate) (PEDOT:PSS), respectively. Furthermore, it is demonstrated experimentally that the introduction of such a compliant layer improves adhesion between the deposit and its substrate.

Dual ion beam assisted deposition of biaxially textured template layers

DOEpatents

Groves, James R.; Arendt, Paul N.; Hammond, Robert H.

2005-05-31

The present invention is directed towards a process and apparatus for epitaxial deposition of a material, e.g., a layer of MgO, onto a substrate such as a flexible metal substrate, using dual ion beams for the ion beam assisted deposition whereby thick layers can be deposited without degradation of the desired properties by the material. The ability to deposit thicker layers without loss of properties provides a significantly broader deposition window for the process.

Process for the deposition of high temperature stress and oxidation resistant coatings on silicon-based substrates

DOEpatents

Sarin, V.K.

1991-07-30

A process is disclosed for depositing a high temperature stress and oxidation resistant coating on a silicon nitride- or silicon carbide-based substrate body. A gas mixture is passed over the substrate at about 900--1500 C and about 1 torr to about ambient pressure. The gas mixture includes one or more halide vapors with other suitable reactant gases. The partial pressure ratios, flow rates, and process times are sufficient to deposit a continuous, fully dense, adherent coating. The halide and other reactant gases are gradually varied during deposition so that the coating is a graded coating of at least two layers. Each layer is a graded layer changing in composition from the material over which it is deposited to the material of the layer and further to the material, if any, deposited thereon, so that no clearly defined compositional interfaces exist. The gases and their partial pressures are varied according to a predetermined time schedule and the halide and other reactant gases are selected so that the layers include (a) an adherent, continuous intermediate layer about 0.5-20 microns thick of an aluminum nitride or an aluminum oxynitride material, over and chemically bonded to the substrate body, and (b) an adherent, continuous first outer layer about 0.5-900 microns thick including an oxide of aluminum or zirconium over and chemically bonded to the intermediate layer.

Process for the deposition of high temperature stress and oxidation resistant coatings on silicon-based substrates

DOEpatents

Sarin, Vinod K.

1991-01-01

A process for depositing a high temperature stress and oxidation resistant coating on a silicon nitride- or silicon carbide-based substrate body. A gas mixture is passed over the substrate at about 900.degree.-1500.degree. C. and about 1 torr to about ambient pressure. The gas mixture includes one or more halide vapors with other suitable reactant gases. The partial pressure ratios, flow rates, and process times are sufficient to deposit a continuous, fully dense, adherent coating. The halide and other reactant gases are gradually varied during deposition so that the coating is a graded coating of at least two layers. Each layer is a graded layer changing in composition from the material over which it is deposited to the material of the layer and further to the material, if any, deposited thereon, so that no clearly defined compositional interfaces exist. The gases and their partial pressures are varied according to a predetermined time schedule and the halide and other reactant gases are selected so that the layers include (a) an adherent, continuous intermediate layer about 0.5-20 microns thick of an aluminum nitride or an aluminum oxynitride material, over and chemically bonded to the substrate body, and (b) an adherent, continuous first outer layer about 0.5-900 microns thick including an oxide of aluminum or zirconium over and chemically bonded to the intermediate layer.

Corrosion testing using isotopes

DOEpatents

Hohorst, Frederick A.

1995-12-05

A method for determining the corrosion behavior of a material with respect to a medium in contact with the material by: implanting a substantially chemically inert gas in a matrix so that corrosion experienced by the material causes the inert gas to enter the medium; placing the medium in contact with the material; and measuring the amount of inert gas which enters the medium. A test sample of a material whose resistance to corrosion by a medium is to be tested, composed of: a body of the material, which body has a surface to be contacted by the medium; and a substantially chemically inert gas implanted into the body to a depth below the surface. A test sample of a material whose resistance to corrosion by a medium is to be tested, composed of: a substrate of material which is easily corroded by the medium, the substrate having a surface; a substantially chemically inert gas implanted into the substrate; and a sheet of the material whose resistance to corrosion is to be tested, the sheet being disposed against the surface of the substrate and having a defined thickness.

High-temperature chemical stability of plasma-sprayed Ca{sub 0.5}Sr{sub 0.5}Zr{sub 4}P{sub 6}O{sub 24} coatings on Nicalon/SiC ceramic matrix composite and Ni-based superalloy substrates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, W.Y.; Cooley, K.M.; Joslin, D.L.

The potential application of Ca{sub 0.5}Sr{sub 0.5}Zr{sub 4}P{sub 6}O{sub 24} (CS50) as a corrosion-resistant coating material for Si-based ceramics and as a thermal barrier coating material for Ni-based superalloys was explored. A {approximately}200 {micro}m thick CS50 coating was prepared by air plasma spray with commercially available powder. A Nicalon/SiC ceramic matrix composite and a Ni-based superalloy coated with a {approximately}200 {micro}m thick metallic bond coat layer were used as substrate materials. Both the powder and coating contained ZrP{sub 2}O{sub 7} as an impurity phase, and the coating was highly porous as-deposited. The coating deposited on the Nicalon/SiC substrate was chemicallymore » stable upon exposure to air and Na{sub 2}SO{sub 4}/O{sub 2} atmospheres at 1,000 C for 100 h. In contrast, the coating sprayed onto the superalloy substrate significantly reacted with the bond coat surface after similar oxidation in air.« less

A quantitative method for photovoltaic encapsulation system optimization

NASA Technical Reports Server (NTRS)

Garcia, A., III; Minning, C. P.; Cuddihy, E. F.

1981-01-01

It is pointed out that the design of encapsulation systems for flat plate photovoltaic modules requires the fulfillment of conflicting design requirements. An investigation was conducted with the objective to find an approach which will make it possible to determine a system with optimum characteristics. The results of the thermal, optical, structural, and electrical isolation analyses performed in the investigation indicate the major factors in the design of terrestrial photovoltaic modules. For defect-free materials, minimum encapsulation thicknesses are determined primarily by structural considerations. Cell temperature is not strongly affected by encapsulant thickness or thermal conductivity. The emissivity of module surfaces exerts a significant influence on cell temperature. Encapsulants should be elastomeric, and ribs are required on substrate modules. Aluminum is unsuitable as a substrate material. Antireflection coating is required on cell surfaces.

Commercial production of QWIP wafers by molecular beam epitaxy

NASA Astrophysics Data System (ADS)

Fastenau, J. M.; Liu, W. K.; Fang, X. M.; Lubyshev, D. I.; Pelzel, R. I.; Yurasits, T. R.; Stewart, T. R.; Lee, J. H.; Li, S. S.; Tidrow, M. Z.

2001-06-01

As the performance of quantum well infrared photodetectors (QWIPs) and QWIP-based imaging systems continues to improve, their demand will undoubtedly grow. This points to the importance of a reliable commercial supplier of semiconductor QWIP material on three inch and, in the near future, four-inch substrates. Molecular beam epitaxy (MBE) is the preferred technique for growing the demanding QWIP structure, as tight control is required over the material composition and layer thickness. We report the current status of MBE-grown GaAs-based QWIP structures in a commercial production environment at IQE. Uniformity data and run-to-run reproducibility on both three-inch and four-inch GaAs substrates are quantified using alloy composition and QW thickness. Initial results on growth technology transfer to a multi-wafer MBE reactor are also presented. High-resolution X-ray diffraction measurements demonstrate GaAs QW thickness variations and AlGaAs barrier compositions changes to be less than 4% and 1% Al, respectively, across four-inch QWIP wafers from both single- and multiple-wafer MBE platforms.

Thin Film Phase Transition Materials Development Program

DTIC Science & Technology

1985-04-01

and ̂ from f are consistent with a real, positive film thickness d. These conditions are written IP( td /4) = 0, d > 0, (49) where IP denotes...surface of the substrate of the form . aAC(a) + bBD (a) >< cAB(a) + dCD(a) where (a) represents a phase adsorbed on the substrate surface, and the

Method of making coherent multilayer crystals

DOEpatents

Schuller, Ivan K.; Falco, Charles M.

1984-01-01

A new material 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 .ANG. to 2500 .ANG.. The multilayer crystals are prepared by sputter deposition under conditions which slow the sputtered atoms to near substrate temperatures before they contact the substrate.

Epitaxial Growth of Cubic Crystalline Semiconductor Alloys on Basal Plane of Trigonal or Hexagonal Crystal

NASA Technical Reports Server (NTRS)

Park, Yeonjoon (Inventor); Choi, Sang H. (Inventor); King, Glen C. (Inventor)

2011-01-01

Hetero-epitaxial semiconductor materials comprising cubic crystalline semiconductor alloys grown on the basal plane of trigonal and hexagonal substrates, in which misfit dislocations are reduced by approximate lattice matching of the cubic crystal structure to underlying trigonal or hexagonal substrate structure, enabling the development of alloyed semiconductor layers of greater thickness, resulting in a new class of semiconductor materials and corresponding devices, including improved hetero-bipolar and high-electron mobility transistors, and high-mobility thermoelectric devices.

Magnetic and structural characterization of ultra-thin Fe (222) films

NASA Astrophysics Data System (ADS)

Loving, Melissa G.; Brown, Emily E.; Rizzo, Nicholas D.; Ambrose, Thomas F.

2018-05-01

Varied thickness body centered cubic (BCC) ultrathin Fe films (10-50Å) have been sputter deposited onto Si (111) substrates. BCC Fe with the novel (222) texture was obtained by H- terminating the Si (111) starting substrate then immediately depositing the magnetic films. Structural results derived from grazing incidence x-ray diffraction and x-ray reflectivity confirm the crystallographic texture, film thickness, and interface roughness. Magnetic results indicate that Fe (222) exhibits soft magnetic switching (easy axis), high anisotropy (hard axis), which is maintained across the thickness range, and a positive magnetostriction (for the thicker film layers). The observed soft magnetic switching in this system makes it an ideal candidate for future magnetic memory development as well as other microelectronics applications that utilize magnetic materials.

FEM Modeling of In-Plane Stress Distribution in Thick Brittle Coatings/Films on Ductile Substrates Subjected to Tensile Stress to Determine Interfacial Strength.

PubMed

Wang, Kaishi; Zhang, Fangzhou; Bordia, Rajendra K

2018-03-27

The ceramic-metal interface is present in various material structures and devices that are vulnerable to failures, like cracking, which are typically due to their incompatible properties, e.g., thermal expansion mismatch. In failure of these multilayer systems, interfacial shear strength is a good measure of the robustness of interfaces, especially for planar films. There is a widely-used shear lag model and method by Agrawal and Raj to analyse and measure the interfacial shear strength of thin brittle film on ductile substrates. The use of this classical model for a type of polymer derived ceramic coatings (thickness ~18 μm) on steel substrate leads to high values of interfacial shear strength. Here, we present finite element simulations for such a coating system when it is subjected to in-plane tension. Results show that the in-plane stresses in the coating are non-uniform, i.e., varying across the thickness of the film. Therefore, they do not meet one of the basic assumptions of the classical model: uniform in-plane stress. Furthermore, effects of three significant parameters, film thickness, crack spacing, and Young's modulus, on the in-plane stress distribution have also been investigated. 'Thickness-averaged In-plane Stress' (TIS), a new failure criterion, is proposed for estimating the interfacial shear strength, which leads to a more realistic estimation of the tensile strength and interfacial shear strength of thick brittle films/coatings on ductile substrates.

FEM Modeling of In-Plane Stress Distribution in Thick Brittle Coatings/Films on Ductile Substrates Subjected to Tensile Stress to Determine Interfacial Strength

PubMed Central

Zhang, Fangzhou; Bordia, Rajendra K.

2018-01-01

The ceramic-metal interface is present in various material structures and devices that are vulnerable to failures, like cracking, which are typically due to their incompatible properties, e.g., thermal expansion mismatch. In failure of these multilayer systems, interfacial shear strength is a good measure of the robustness of interfaces, especially for planar films. There is a widely-used shear lag model and method by Agrawal and Raj to analyse and measure the interfacial shear strength of thin brittle film on ductile substrates. The use of this classical model for a type of polymer derived ceramic coatings (thickness ~18 μm) on steel substrate leads to high values of interfacial shear strength. Here, we present finite element simulations for such a coating system when it is subjected to in-plane tension. Results show that the in-plane stresses in the coating are non-uniform, i.e., varying across the thickness of the film. Therefore, they do not meet one of the basic assumptions of the classical model: uniform in-plane stress. Furthermore, effects of three significant parameters, film thickness, crack spacing, and Young’s modulus, on the in-plane stress distribution have also been investigated. ‘Thickness-averaged In-plane Stress’ (TIS), a new failure criterion, is proposed for estimating the interfacial shear strength, which leads to a more realistic estimation of the tensile strength and interfacial shear strength of thick brittle films/coatings on ductile substrates. PMID:29584647

Load-Bearing Biomedical Applications of Diamond-Like Carbon Coatings - Current Status

PubMed Central

Alakoski, Esa; Tiainen, Veli-Matti; Soininen, Antti; Konttinen, Yrjö T

2008-01-01

The current status of diamond-like carbon (DLC) coatings for biomedical applications is reviewed with emphasis on load-bearing coatings. Although diamond-like carbon coating materials have been studied for decades, no indisputably successful commercial biomedical applications for high load situations exist today. High internal stress, leading to insufficient adhesion of thick coatings, is the evident reason behind this delay of the break-through of DLC coatings for applications. Excellent adhesion of thick DLC coatings is of utmost importance for load-bearing applications. According to this review superior candidate material for articulating implants is thick and adherent DLC on both sliding surfaces. With the filtered pulsed arc discharge method, all the necessary requirements for the deposition of thick and adherent DLC are fulfilled, provided that the substrate material is selected properly. PMID:19478929

Mechanics of hard films on soft substrates

NASA Astrophysics Data System (ADS)

Lu, Nanshu

2009-12-01

Flexible electronics have been developed for various applications, including paper-like electronic readers, rollable solar cells, electronic skins etc., with the merits of light weight, low cost, large area, and ruggedness. The systems may be subject to one-time or repeated large deformation during manufacturing and application. Although organic materials can be highly deformable, currently they are not able to fulfill every electronic function. Therefore flexible electronic devices are usually made as organic/inorganic hybrids, with diverse materials, complex architecture, and micro features. While the polymer substrates can recover from large deformations, thin films of electronic materials such as metals, silicon, oxides, and nitrides fracture at small strains, usually less than a few percent. Mechanics of hard films on soft substrates hence holds the key to build high-performance and highly reliable flex circuits. This thesis investigates the deformability and failure mechanisms of thin films of metallic and ceramic materials supported by soft polymeric substrates through combined experimental, theoretical, and numerical methods. When subject to tension, micron-thick metal films with stable microstructure and strong interfacial adhesion to the substrate can be stretched beyond 50% without forming cracks. They eventually rupture by a ductile transgranular fracture which involves simultaneous necking and debonding. When metal films become nanometer-thick, intergranular fracture dominates the failure mode at elongations of only a few percent. Unannealed films show unstable microstructure at room temperature when subject to mechanical loading. In this case, films also rupture at small strains but by three concurrent mechanisms: deformation-induced grain growth, strain localization at large grains, and simultaneous debonding. In contrast to metal films, ceramic films rupture by brittle mechanisms. The only way to prevent rupture of ceramic films is to reduce the strain they are subject to. Instead of using blanket films that fail at strains less than i%, we have patterned ceramic films into a lattice of periodic, isolated islands. Failure modes such as channel cracking, debonding, and wrinkling have been identified. Island behaviors are controlled by factors such as island size, thickness, and elastic mismatch with the substrate. A very soft interlayer between the islands and the underlying polyimide substrate reduces strains in the islands by orders of magnitude. Using this approach, substrates with arrays of 200 x 200 mum2 large SiNx islands were stretched beyond 20% without cracking or debonding the islands. In summary, highly stretchable thin metal films and ceramic island arrays supported by polymer substrates have been achieved, along with mechanistic understandings of their deformation and failure mechanisms.

Material optimization of multi-layered enhanced nanostructures

NASA Astrophysics Data System (ADS)

Strobbia, Pietro

The employment of surface enhanced Raman scattering (SERS)-based sensing in real-world scenarios will offer numerous advantages over current optical sensors. Examples of these advantages are the intrinsic and simultaneous detection of multiple analytes, among many others. To achieve such a goal, SERS substrates with throughput and reproducibility comparable to commonly used fluorescence sensors have to be developed. To this end, our lab has discovered a multi-layer geometry, based on alternating films of a metal and a dielectric, that amplifies the SERS signal (multi-layer enhancement). The advantage of these multi-layered structures is to amplify the SERS signal exploiting layer-to-layer interactions in the volume of the structures, rather than on its surface. This strategy permits an amplification of the signal without modifying the surface characteristics of a substrate, and therefore conserving its reproducibility. Multi-layered structures can therefore be used to amplify the sensitivity and throughput of potentially any previously developed SERS sensor. In this thesis, these multi-layered structures were optimized and applied to different SERS substrates. The role of the dielectric spacer layer in the multi-layer enhancement was elucidated by fabricating spacers with different characteristics and studying their effect on the overall enhancement. Thickness, surface coverage and physical properties of the spacer were studied. Additionally, the multi-layered structures were applied to commercial SERS substrates and to isolated SERS probes. Studies on the dependence of the multi-layer enhancement on the thickness of the spacer demonstrated that the enhancement increases as a function of surface coverage at sub-monolayer thicknesses, due to the increasing multi-layer nature of the substrates. For fully coalescent spacers the enhancement decreases as a function of thickness, due to the loss of interaction between proximal metallic films. The influence of the physical properties of the spacer on the multi-layer enhancement were also studied. The trends in Schottky barrier height, interfacial potential and dielectric constant were isolated by using different materials as spacers (i.e., TiO2, HfO2, Ag 2O and Al2O3). The results show that the bulk dielectric constant of the material can be used to predict the relative magnitude of the multi-layer enhancement, with low dielectric constant materials performing more efficiently as spacers. Optimal spacer layers were found to be ultrathin coalescent films (ideally a monolayer) of low dielectric constant materials. Finally, multi-layered structures were observed to be employable to amplify SERS in drastically different substrate geometries. The multi-layered structures were applied to disposable commercial SERS substrates (i.e., Klarite). This project involved the regeneration of the used substrates, by stripping and redepositing the gold coating layer, and their amplification, by using the multi-layer geometry. The latter was observed to amplify the sensitivity of the substrates. Additionally, the multi-layered structures were applied to probes dispersed in solution. Such probes were observed to yield stronger SERS signal when optically trapped and to reduce the background signal. The application of the multi-layered structures on trapped probes, not only further amplified the SERS signal, but also increased the maximum number of applicable layers for the structures.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mahadevapuram, Nikhila; Mitra, Indranil; Sridhar, Shyam

Thin films of lamellar poly(styrene-b-methyl methacrylate) (PS-PMMA) block copolymers are widely investigated for surface patterning. These materials can generate dense arrays of nanoscale lines when the lamellar domains are oriented perpendicular to the substrate. To stabilize this preferred domain orientation, we tuned the substrate surface energy using oxidation of hydrophobic silane coatings. This simple approach is effective for a broad range of PS-PMMA film thicknesses when the oxidation time is optimized, which demonstrates that the substrate coating is energetically neutral with respect to PS and PMMA segments. The lamellar films are characterized by high densities of defects that exhibit amore » strong dependence on film thickness: in-plane topological defects disrupt the lateral order in ultrathin films, while lamellar domains in thick films can bend and tilt to large misorientation angles. As a result, the types and densities of these defects are similar to those observed with other classes of neutral substrate coatings, such as random copolymer brushes, which demonstrates that oxidized silanes can be used to control PS-PMMA self assembly in thin films.« less

Ordering of lamellar block copolymers on oxidized silane coatings

DOE PAGES

Mahadevapuram, Nikhila; Mitra, Indranil; Sridhar, Shyam; ...

2016-01-02

Thin films of lamellar poly(styrene-b-methyl methacrylate) (PS-PMMA) block copolymers are widely investigated for surface patterning. These materials can generate dense arrays of nanoscale lines when the lamellar domains are oriented perpendicular to the substrate. To stabilize this preferred domain orientation, we tuned the substrate surface energy using oxidation of hydrophobic silane coatings. This simple approach is effective for a broad range of PS-PMMA film thicknesses when the oxidation time is optimized, which demonstrates that the substrate coating is energetically neutral with respect to PS and PMMA segments. The lamellar films are characterized by high densities of defects that exhibit amore » strong dependence on film thickness: in-plane topological defects disrupt the lateral order in ultrathin films, while lamellar domains in thick films can bend and tilt to large misorientation angles. As a result, the types and densities of these defects are similar to those observed with other classes of neutral substrate coatings, such as random copolymer brushes, which demonstrates that oxidized silanes can be used to control PS-PMMA self assembly in thin films.« less

Mechanical behaviour of metallic thin films on polymeric substrates and the effect of ion beam assistance on crack propagation

DOE Office of Scientific and Technical Information (OSTI.GOV)

George, M.; Coupeau, C.; Colin, J.

2005-01-10

The mechanisms of crack propagation in metallic films on polymeric substrates have been studied through in situ atomic force microscopy observations of thin films under tensile stresses and finite element stress calculations. Two series of films - ones deposited with ion beam assistance, the others without - have been investigated. The observations and stress calculations show that ion beam assistance can change drastically the propagation of cracks in coated materials: by improving the adhesion film/substrate, it slows down the delamination process, but in the same time enhances the cracks growth in the thickness of the material.

Optical properties of sputtered aluminum on graphite/epoxy composite material

NASA Technical Reports Server (NTRS)

Witte, William G., Jr.; Teichman, Louis A.

1989-01-01

Solar absorptance, emittance, and coating thickness were measured for a range of coating thicknesses from about 400 A to 2500 A. The coatings were sputtered from an aluminum target onto 1-inch-diameter substrates of T300/5209 graphite/epoxy composite material with two different surface textures. Solar absorptance and emittance values for the specimens with the smooth surface finish were lower than those for the specimens with the rough surface finish. The ratio of solar absorptance to emittance was higher for the smooth specimens, increasing from 2 to 4 over the coating thickness range, than for the rough ones, which had a constant ratio of about 1. The solar absorptance and emittance values were dependent on the thickness of the sputtered coating.

Strong thin membrane structure for use as solar sail comprising substrate with reflective coating on one surface and an infra red emissivity increasing coating on the other surface

NASA Technical Reports Server (NTRS)

Frazer, Robert E. (Inventor)

1982-01-01

Production of strong lightweight membrane structure by applying a thin reflective coating such as aluminum to a rotating cylinder, applying a mesh material such as nylon over the aluminum coating, coating the mesh overlying the aluminum with a polymerizing material such as a para-xylylene monomer gas to polymerize as a film bound to the mesh and the aluminum, and applying an emissivity increasing material such as chromium and silicon monoxide to the polymer film to disperse such material colloidally into the growing polymer film, or applying such material to the final polymer film, and removing the resulting membrane structure from the cylinder. Alternatively, such membrane structure can be formed by etching a substrate in the form of an organic film such as a polyimide, or a metal foil, to remove material from the substrate and reduce its thickness, applying a thin reflective coating such as aluminum on one side of the substrate and applying an emissivity increasing coating such as chromium and silicon monoxide on the reverse side of the substrate.

Spectroscopic imaging ellipsometry for automated search of flakes of mono- and n-layers of 2D-materials

NASA Astrophysics Data System (ADS)

Funke, S.; Wurstbauer, U.; Miller, B.; Matković, A.; Green, A.; Diebold, A.; Röling, C.; Thiesen, P. H.

2017-11-01

Spectroscopic imaging ellipsometry (SIE) is used to localize and characterize flakes of conducting, semi-conducting and insulating 2D-materials. Although the research in the field of monolayers of 2D-materials increased the last years, it is still challenging to look for small flakes and distinguish between different layer numbers. Special substrates are used to enhance optical contrast for the conventional light microscopy (LM). In case when other functional support from the substrate is essential, an additional transfer step needs to be employed, bringing the drawbacks as contamination, cracking and wrinkling of the 2D materials. Furthermore it is time-consuming and not yet fully automatically to search for monolayers by contrast with the LM. Here we present a method, that is able to automatically localize regions with desired thicknesses, e.g. monolayers, of the different materials on arbitrary substrates.

Soft liquid phase adsorption for fabrication of organic semiconductor films on wettability patterned surfaces.

PubMed

Watanabe, Satoshi; Akiyoshi, Yuri; Matsumoto, Mutsuyoshi

2014-01-01

We report a soft liquid-phase adsorption (SLPA) technique for the fabrication of organic semiconductor films on wettability-patterned substrates using toluene/water emulsions. Wettability-patterned substrates were obtained by the UV-ozone treatment of self-assembled monolayers of silane coupling agents on glass plates using a metal mask. Organic semiconductor polymer films were formed selectively on the hydrophobic part of the wettability-patterned substrates. The thickness of the films fabricated by the SLPA technique is significantly larger than that of the films fabricated by dip-coating and spin-coating techniques. The film thickness can be controlled by adjusting the volume ratio of toluene to water, immersion angle, immersion temperature, and immersion time. The SLPA technique allows for the direct production of organic semiconductor films on wettability-patterned substrates with minimized material consumption and reduced number of fabrication steps.

Carbon-carbon mirrors for exoatmospheric and space applications

NASA Astrophysics Data System (ADS)

Krumweide, Duane E.; Wonacott, Gary D.; Woida, Patrick M.; Woida, Rigel Q.; Shih, Wei

2007-09-01

The cost and leadtime associated with beryllium has forced the MDA and other defense agencies to look for alternative materials with similar structural and thermal properties. The use of carbon-carbon material, specifically in optical components has been demonstrated analytically in prior SBIR work at San Diego Composites. Carbon-carbon material was chosen for its low in-plane and through-thickness CTE (athermal design), high specific stiffness, near-zero coefficient of moisture expansion, availability of material (specifically c-c honeycomb for lightweight substrates), and compatibility with silicon monoxide (SiO) and silicon dioxide (SiO II) coatings. Subsequent development work has produced shaped carbon-carbon sandwich substrates which have been ground, polished, coated and figured using traditional optical processing. Further development has also been done on machined monolithic carbon-carbon mirror substrates which have also been processed using standard optical finishing techniques.

Quantum Information Science Research and Technical Assessment Project

DTIC Science & Technology

2010-08-01

parameter space. This system incorporates heaters, deposition monitors, temperature sensors , and adjustable substrate holders and masks under high...thickness monitor; G = glass surfaces for transmission measurements; PD = photodiode; TC = thermocouple temperature sensors . Substrate Preparation...crystal due to the mass of material deposited on the crystal. By adjusting the distance of the sensor relative to the source and employing the ~1/R2

Coherent multilayer crystals and method of making

DOEpatents

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

1980-10-30

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.

Effects of substrate heating and post-deposition annealing on characteristics of thin MOCVD HfO2 films

NASA Astrophysics Data System (ADS)

Gopalan, Sundararaman; Ramesh, Sivaramakrishnan; Dutta, Shibesh; Virajit Garbhapu, Venkata

2018-02-01

It is well known that Hf-based dielectrics have replaced the traditional SiO2 and SiON as gate dielectric materials for conventional CMOS devices. By using thicker high-k materials such as HfO2 rather than ultra-thin SiO2, we can bring down leakage current densities in MOS devices to acceptable levels. HfO2 is also one of the potential candidates as a blocking dielectric for Flash memory applications for the same reason. In this study, effects of substrate heating and oxygen flow rate while depositing HfO2 thin films using CVD and effects of post deposition annealing on the physical and electrical characteristics of HfO2 thin films are presented. It was observed that substrate heating during deposition helps improve the density and electrical characteristics of the films. At higher substrate temperature, Vfb moved closer to zero and also resulted in significant reduction in hysteresis. Higher O2 flow rates may improve capacitance, but also results in slightly higher leakage. The effect of PDA depended on film thickness and O2 PDA improved characteristics only for thick films. For thinner films forming gas anneal resulted in better electrical characteristics.

Corrosion testing using isotopes

DOEpatents

Hohorst, F.A.

1995-12-05

A method is described for determining the corrosion behavior of a material with respect to a medium in contact with the material by: implanting a substantially chemically inert gas in a matrix so that corrosion experienced by the material causes the inert gas to enter the medium; placing the medium in contact with the material; and measuring the amount of inert gas which enters the medium. A test sample of a material whose resistance to corrosion by a medium is to be tested is described composed of: a body of the material, which body has a surface to be contacted by the medium; and a substantially chemically inert gas implanted into the body to a depth below the surface. A test sample of a material whose resistance to corrosion by a medium is to be tested is described composed of: a substrate of material which is easily corroded by the medium, the substrate having a surface; a substantially chemically inert gas implanted into the substrate; and a sheet of the material whose resistance to corrosion is to be tested, the sheet being disposed against the surface of the substrate and having a defined thickness. 3 figs.

Nuclear fuel element

DOEpatents

Armijo, Joseph S.; Coffin, Jr., Louis F.

1983-01-01

A nuclear fuel element for use in the core of a nuclear reactor is disclosed and has a composite cladding having a substrate and a metal barrier metallurgically bonded on the inside surface of the substrate so that the metal barrier forms a shield between the substrate and the nuclear fuel material held within the cladding. The metal barrier forms about 1 to about 30 percent of the thickness of the cladding and is comprised of a low neutron absorption metal of substantially pure zirconium. The metal barrier serves as a preferential reaction site for gaseous impurities and fission products and protects the substrate from contact and reaction with such impurities and fission products. The substrate of the composite cladding is selected from conventional cladding materials and preferably is a zirconium alloy. Methods of manufacturing the composite cladding are also disclosed.

Plasma spraying method for forming diamond and diamond-like coatings

DOEpatents

Holcombe, C.E.; Seals, R.D.; Price, R.E.

1997-06-03

A method and composition is disclosed for the deposition of a thick layer of diamond or diamond-like material. The method includes high temperature processing wherein a selected composition including at least glassy carbon is heated in a direct current plasma arc device to a selected temperature above the softening point, in an inert atmosphere, and is propelled to quickly quenched on a selected substrate. The softened or molten composition crystallizes on the substrate to form a thick deposition layer comprising at least a diamond or diamond-like material. The selected composition includes at least glassy carbon as a primary constituent and may include at least one secondary constituent. Preferably, the secondary constituents are selected from the group consisting of at least diamond powder, boron carbide (B{sub 4}C) powder and mixtures thereof. 9 figs.

Uniformity Masks Design Method Based on the Shadow Matrix for Coating Materials with Different Condensation Characteristics

PubMed Central

2013-01-01

An intuitionistic method is proposed to design shadow masks to achieve thickness profile control for evaporation coating processes. The proposed method is based on the concept of the shadow matrix, which is a matrix that contains coefficients that build quantitive relations between shape parameters of masks and shadow quantities of substrate directly. By using the shadow matrix, shape parameters of shadow masks could be derived simply by solving a matrix equation. Verification experiments were performed on a special case where coating materials have different condensation characteristics. By using the designed mask pair with complementary shapes, thickness uniformities of better than 98% are demonstrated for MgF2 (m = 1) and LaF3 (m = 0.5) simultaneously on a 280 mm diameter spherical substrate with the radius curvature of 200 mm. PMID:24227996

Method of Fabricating Schottky Barrier solar cell

NASA Technical Reports Server (NTRS)

Stirn, R. J.; Yeh, Y. C. M. (Inventor)

1982-01-01

On a thin substrate of low cost material with at least the top surface of the substrate being electrically conductive is deposited a thin layer of heavily doped n-type polycrystalline germanium, with crystalline sizes in the submicron range. A passivation layer may be deposited on the substrate to prevent migration of impurities into the polycrystalline germanium. The polycrystalline germanium is recrystallized to increase the crystal sizes in the germanium layer to not less than 5 micros to serve as a base layer on which a thin layer of gallium arsenide is vapor epitaxially grown to a selected thickness. A thermally-grown oxide layer of a thickness of several tens of angstroms is formed on the gallium arsenide layer. A metal layer, of not more about 100 angstroms thick, is deposited on the oxide layer, and a grid electrode is deposited to be in electrical contact with the top surface of the metal layer. An antireflection coating may be deposited on the exposed top surface of the metal layer.

Simple Refractometers for Index Measurements by Minimum Deviation Method from Far-ultraviolet to Near Infrared

NASA Technical Reports Server (NTRS)

Leviton, Douglas B.; Madison, Timothy J.; Petrone, Peter

1998-01-01

The focal shift of an optical filter used in non-collimated light depends directly on substrate thickness and index of refraction. The HST Advanced Camera for Surveys (ACS) requires a set of filters whose focal shifts are tightly matched. Knowing the index of refraction for substrate glasses allows precise substrate thicknesses to be specified. Two refractometers have been developed at the Goddard Space Flight Center (GSFC) to determine the indices of refraction of materials from which ACS filters are made. Modem imaging detectors for the near infrared, visible, and far ultraviolet spectral regions make these simple yet sophisticated refractometers possible. A new technology, high accuracy, angular encoder also developed at GSFC makes high precision index measurement possible in the vacuum ultraviolet.

Impact of substrate on structure and electrical properties in lead-based ferroelectric thin films

NASA Astrophysics Data System (ADS)

Valanoor, Nagarajan Venkatasubramanian

Current trends in semiconductor technology demand that ferroelectric materials be used in thin film form, rather than bulk, for integration and scaling purposes. An inevitable consequence of integration is substrate induced constraint and stress. Sources of this stress are the lattice and thermal mismatch between film and substrate, structural phase transformation which leads to spontaneous strains, and dislocation cores at the film substrate interface. In addition to classical stress relaxation mechanisms all highly tetragonal ferroelectrics relax internal stress via formation of polydomain (90° domains and not 180° domains) structures below the phase transformation, which brings about a change in the microstructure of the film. Hence it is possible to control the resultant microstructure by controlling the degree of polydomain relaxation. Obviously this affects the electrical and electro-mechanical properties and in turn the device performance. The goal of this research is to study this structure-property relationship of ferroelectric thin films where in the structure has been systematically modified by changing the substrate-induced effect. To investigate the effect of the substrate, epitaxial films of PbZr 0.2Ti0.8O3 were grown by pulsed laser deposition (PLD). Epitaxial films reduce the complexities introduced grain boundaries and multiple domain orientations. By systematically changing the thickness the spontaneous strain or c/a ratio can be varied. As a consequence polydomain formation varies as a function of film thickness. Thus this is an effective yet simple method to fully understand the impact of stress on structure-property inter-relationships. The theoretical background for these experiments is first laid out by a thermodynamic analysis of the polydomain formation. It leads to the construction of a domain stability map and indicates a presence of a critical thickness for polydomain formation. This is followed by an investigation of the impact of polydomain formation on quasi-static and dynamic polarization switching. To correlate the material microstructure to switching, an activation field, alpha, is introduced. It is shown theoretically that alpha ∝ (c/a-1)3.5 and a good experimental fit can be obtained. However it is observed that polydomain formation does not impact the electromechanical and dielectric response significantly. It is shown experimentally and theoretically that stress-induced polarization varies only by 10%. Therefore to study the impact of in plane stresses induced by substrate on piezoelectric and dielectric response we chose a "soft" relaxor ferroelectric (RFE) wherein the Curie temperature is close to room temperature. In this case even a small application of stress can change the properties significantly. The relaxor composition chosen was PbMg1/3Nb 2/3O3(90%)-PbTiO3(10%). By systematically changing the substrate and the thickness, stresses in the film the electromechanical constants is varied. High-resolution electron microscopy revealed a distinct change in the microstructure as a function of thickness, and a probable answer as to why thin films show inferior properties compared to bulk materials is proposed. The last part of this thesis focuses on the effect of micro stresses. Two examples are demonstrated where the mechanical forces of interaction between the film and substrate are manipulated on a very local scale. We show that by inducing stresses at local regions one can induce polydomains in film thinner than previously calculated critical thickness, while by removing constraint at local regions we can enhance the d33 co-efficient to values higher than those shown by bulk ceramics.

Optimisation and characterisation of tungsten thick coatings on copper based alloy substrates

NASA Astrophysics Data System (ADS)

Riccardi, B.; Montanari, R.; Casadei, M.; Costanza, G.; Filacchioni, G.; Moriani, A.

2006-06-01

Tungsten is a promising armour material for plasma facing components of nuclear fusion reactors because of its low sputter rate and favourable thermo-mechanical properties. Among all the techniques able to realise W armours, plasma spray looks particularly attractive owing to its simplicity and low cost. The present work concerns the optimisation of spraying parameters aimed at 4-5 mm thick W coating on copper-chromium-zirconium (Cu,Cr,Zr) alloy substrates. Characterisation of coatings was performed in order to assess microstructure, impurity content, density, tensile strength, adhesion strength, thermal conductivity and thermal expansion coefficient. The work performed has demonstrated the feasibility of thick W coatings on flat and curved geometries. These coatings appear as a reliable armour for medium heat flux plasma facing component.

High efficiency, low cost, thin film silicon solar cell design and method for making

DOEpatents

Sopori, Bhushan L.

2001-01-01

A semiconductor device having a substrate, a conductive intermediate layer deposited onto said substrate, wherein the intermediate layer serves as a back electrode, an optical reflector, and an interface for impurity gettering, and a semiconductor layer deposited onto said intermediate layer, wherein the semiconductor layer has a grain size at least as large as the layer thickness, and preferably about ten times the layer thickness. The device is formed by depositing a metal layer on a substrate, depositing a semiconductive material on the metal-coated substrate to produce a composite structure, and then optically processing the composite structure by illuminating it with infrared electromagnetic radiation according to a unique time-energy profile that first produces pits in the backside surface of the semiconductor material, then produces a thin, highly reflective, low resistivity alloy layer over the entire area of the interface between the semiconductor material and the metal layer, and finally produces a grain-enhanced semiconductor layer. The time-energy profile includes increasing the energy to a first energy level to initiate pit formation and create the desired pit size and density, then ramping up to a second energy level in which the entire device is heated to produce an interfacial melt, and finally reducing the energy to a third energy level and holding for a period of time to allow enhancement in the grain size of the semiconductor layer.

High efficiency low cost thin film silicon solar cell design and method for making

DOEpatents

Sopori, Bhushan L.

1999-01-01

A semiconductor device having a substrate, a conductive intermediate layer deposited onto said substrate, wherein the intermediate layer serves as a back electrode, an optical reflector, and an interface for impurity gettering, and a semiconductor layer deposited onto said intermediate layer, wherein the semiconductor layer has a grain size at least as large as the layer thickness, and preferably about ten times the layer thickness. The device is formed by depositing a metal layer on a substrate, depositing a semiconductive material on the metal-coated substrate to produce a composite structure, and then optically processing the composite structure by illuminating it with infrared electromagnetic radiation according to a unique time-energy profile that first produces pits in the backside surface of the semiconductor material, then produces a thin, highly reflective, low resistivity alloy layer over the entire area of the interface between the semiconductor material and the metal layer, and finally produces a grain-enhanced semiconductor layer. The time-energy profile includes increasing the energy to a first energy level to initiate pit formation and create the desired pit size and density, then ramping up to a second energy level in which the entire device is heated to produce an interfacial melt, and finally reducing the energy to a third energy level and holding for a period of time to allow enhancement in the grain size of the semiconductor layer.

Strong thin membrane structure. [solar sails

NASA Technical Reports Server (NTRS)

Frazer, R. E. (Inventor)

1979-01-01

A continuous process is described for producing strong lightweight structures for use as solar sails for spacecraft propulsion by radiation pressure. A thin reflective coating, such as aluminum, is applied to a rotating cylinder. A nylon mesh, applied over the aluminum coating, is then coated with a polymerizing material such as a para-xylylene monomer gas to polymerize as a film bound to the mesh and the aluminum. An emissivity increasing material such as chromium or silicon monoxide is applied to the polymer film to disperse such material colloidally into the growing polymer film, or to the final polymer film. The resulting membrane structure is then removed from the cylinder. Alternately, the membrane structure can be formed by etching a substrate in the form of an organic film such as a polymide, or a metal foil, to remove material from the substrate and reduce its thickness. A thin reflective coating (aluminum) is applied on one side of the substrate, and an emissivity increasing coating is applied on the reverse side of the substrate.

A Method to Predict the Thickness of Poorly-Bonded Material Along Spray and Spray-Layer Boundaries in Cold Spray Deposition

NASA Astrophysics Data System (ADS)

Li, Yangfan; Hamada, Yukitaka; Otobe, Katsunori; Ando, Teiichi

2017-02-01

Multi-traverse CS provides a unique means for the production of thick coatings and bulk materials from powders. However, the material along spray and spray-layer boundaries is often poorly bonded as it is laid by the leading and trailing peripheries of the spray that carry powder particles with insufficient kinetic energy. For the same reason, the splats in the very first layer deposited on the substrate may not be bonded well either. A mathematical spray model was developed based on an axisymmetric Gaussian mass flow rate distribution and a stepped deposition yield to predict the thickness of such poorly-bonded layers in multi-traverse CS deposition. The predicted thickness of poorly-bonded layers in a multi-traverse Cu coating falls in the range of experimental values. The model also predicts that the material that contains poorly bonded splats could exceed 20% of the total volume of the coating.

Thermal stress in flexible interdigital transducers with anisotropic electroactive cellulose substrates

NASA Astrophysics Data System (ADS)

Yoon, Sean J.; Kim, Jung Woong; Kim, Hyun Chan; Kang, Jinmo; Kim, Jaehwan

2017-12-01

Thermal stress in flexible interdigital transducers a reliability concern in the development of flexible devices, which may lead to interface delamination, stress voiding and plastic deformation. In this paper, a mathematical model is presented to investigate the effect of material selections on the thermal stress in interdigital transducers. We modified the linear relationships in the composite materials theory with the effect of high curvature, anisotropic substrate and small substrate thickness. We evaluated the thermal stresses of interdigital transducers, fabricated with various electrodes, insulators and substrate materials for the comparison. The results show that, among various insulators, organic polymer developed the highest stress level while oxide showed the lowest stress level. Aluminium shows a higher stress level and curvature as an electrode than gold. As substrate materials, polyimide and electroactive cellulose show similar stress levels except the opposite sign convention to each other. Polyimide shows positive curvatures while electroactive cellulose shows negative curvatures, which is attributed to the stress and thermal expansion state of the metal/insulator composite. The results show that the insulator is found to be responsible for the confinement across the metal lines while the substrate is responsible for the confinement along the metal lines.

Barrier layer for a MCrAlY basecoat superalloy combination

DOEpatents

Sabol, Stephen M.; Goedjen, John G.; Vance, Steven J.

2001-01-01

A turbine component contains a substrate (22) such as a superalloy, a basecoat (24) of the type MCrAlY, and a continuous barrier layer (28) between the substrate and basecoat, where the barrier layer (28) is made of an alloy of (Re, Ta, Ru, Os)X, where X can be Ni, Co or their mixture, where the barrier layer is at least 2 micrometers thick and substantially prevents materials from both the basecoat and substrate from migrating through it.

Finite Element Analysis of Multilayered and Functionally Gradient Tribological Coatings With Measured Material Properties (Preprint)

DTIC Science & Technology

2006-11-01

gradient coatings with diamond like carbon (DLC) coating on 440C stainless steel substrate were assumed as a series of perfectly bonded layers with...resistance and low friction. Ti1-xCx (0≤ x ≤1) gradient coatings with diamond like carbon (DLC) coating on 440C stainless steel substrate were...indenter tip was used for the FEA model. Each coating sample consists of 1 μm thick coating and 440C stainless steel substrate. The area function for

Thin-film magnetless Faraday rotators for compact heterogeneous integrated optical isolators

NASA Astrophysics Data System (ADS)

Karki, Dolendra; Stenger, Vincent; Pollick, Andrea; Levy, Miguel

2017-06-01

This report describes the fabrication, characterization, and transfer of ultra-compact thin-film magnetless Faraday rotators to silicon photonic substrates. Thin films of magnetization latching bismuth-substituted rare-earth iron garnets were produced from commercially available materials by mechanical lapping, dice polishing, and crystal-ion-slicing. Eleven- μ m -thick films were shown to retain the 45 ° Faraday rotation of the bulk material to within 2 ° at 1.55 μ m wavelength without re-poling. Anti-reflection coated films evince 0.09 dB insertion loses and better than -20 dB extinction ratios. Lower extinction ratios than the bulk are ascribed to multimode propagation. Significantly larger extinction ratios are predicted for single-mode waveguides. Faraday rotation, extinction ratios, and insertion loss tests on He-ion implanted slab waveguides of the same material yielded similar results. The work culminated with bond alignment and transfer of 7 μ m -thick crystal-ion-sliced 50 × 480 μ m 2 films onto silicon photonic substrates.

Large reflector antenna study

NASA Technical Reports Server (NTRS)

Christodoulou, C. G.

1986-01-01

In some applications, the wires used to construct the grids are plated over with highly conducting materials such as gold or silver. In those cases, depending on the frequency of operation, the coating may not be thick enough to prevent currents from flowing in the substrate. The conjugate gradient method, in conjunction with the fast Fourier transform is employed to solve the problem of scattering from such rectangular grids. An internal impedance is utilized to account for the effects of the substrate conductivity on the induced current densities. Calculated values of the reflection coefficient and induced currents from different coating thicknesses, angles of incidence and polarizations are presented and discussed.

Thermal and Electrical Characterization of Alumina Substrate for Microelectronic Applications

NASA Astrophysics Data System (ADS)

Ahmad, S.; Ibrahim, A.; Alias, R.; Shapee, S. M.; Ambak, Z.; Zakaria, S. Z.; Yahya, M. R.; Mat, A. F. A.

2010-03-01

This paper reports the effect of sintering temperature on thermal and electrical properties of alumina material as substrate for microelectronic devices. Alumina materials in the form of green sheet with 1 mm thickness were sintered at 1100° C, 1300° C and 1500° C for about 20 hours using heating and cooling rates of 2° C/min. The densities were measured using densitometer and the microstructures of the samples were analyzed using SEM micrographs. Meanwhile thermal and electrical properties of the samples were measured using flash method and impedance analyzer respectively. It was found that thermal conductivity and thermal diffusivity of the substrate increases as sintering temperature increases. It was found also that the dielectric constant of alumina substrate increases as the sintering temperature increases.

Flexible metal-semiconductor-metal device prototype on wafer-scale thick boron nitride layers grown by MOVPE.

PubMed

Li, Xin; Jordan, Matthew B; Ayari, Taha; Sundaram, Suresh; El Gmili, Youssef; Alam, Saiful; Alam, Muhbub; Patriarche, Gilles; Voss, Paul L; Paul Salvestrini, Jean; Ougazzaden, Abdallah

2017-04-11

Practical boron nitride (BN) detector applications will require uniform materials over large surface area and thick BN layers. To report important progress toward these technological requirements, 1~2.5 µm-thick BN layers were grown on 2-inch sapphire substrates by metal-organic vapor phase epitaxy (MOVPE). The structural and optical properties were carefully characterized and discussed. The thick layers exhibited strong band-edge absorption near 215 nm. A highly oriented two-dimensional h-BN structure was formed at the film/sapphire interface, which permitted an effective exfoliation of the thick BN film onto other adhesive supports. And this structure resulted in a metal-semiconductor-metal (MSM) device prototype fabricated on BN membrane delaminating from the substrate. MSM photodiode prototype showed low dark current of 2 nA under 100 V, and 100 ± 20% photoconductivity yield for deep UV light illumination. These wafer-scale MOVPE-grown thick BN layers present great potential for the development of deep UV photodetection applications, and even for flexible (opto-) electronics in the future.

The synthesis and characterization of xerogel silica films for interlayer dielectric applications

NASA Astrophysics Data System (ADS)

Chow, Loren Anton

1999-11-01

Lowering the dielectric constant, k, of the interlayer dielectric in microprocessors leads to a decrease in power consumption, crosstalk between interconnects and RC time delay. Because of its low density, porous silica, as derived from the sol-gel process, has been widely praised as having the lowest dielectric constant of all viable "low-k" materials. Presented in this work are the results of an investigation featuring the synthesis and characterization of xerogel silica films. Synthesized were xerogel films derived from a tetrafanctional precursor. Such a material was found to be brittle and given to cracking and delamination during curing. it was found, however, that organic modification of the xerogel film led to a compliant material that remained crack-free throughout the curing process. This "hybrid" material filled 0.35 mum trenches without voids, cracks or delamination. The dielectric constant was found to be extremely sensitive to moisture. Although the moisture content was lower than that detectable by Fourier-transform infrared spectroscopy, the dielectric constant in ambient conditions was 80% higher than a dry film. The voltage breakdown was 3.4 MV/cm and the leakage current during bias temperature stressing (at 200 V and 200°C) was negligibly low. There was a critical film thickness at which the film cracked. This critical film thickness was dependent on the elastic constants of the substrate and the film. Because the strain energy released by the cracking film is commensurate with the compliance of the substrate, cracks formed preferentially in the <100> directions; that is, the directions of lowest substrate modulus. The critical thickness for the <100> direction for the hybrid film cured at 500°C was found to be 1.10 mum. Furthermore, it was found that cracks from the xerogel penetrated into the Si substrate to a depth of 0.8 mum. Using substrates of different elastic constants, the biaxial modulus and the coefficient of thermal expansion were found to be respectively 56 GPa and 2.11 x 10-6/°C. With knowledge of the biaxial modulus, the depth of cracking into the Si substrate and an assumption on Poisson's ratio, the critical crack energy release rate of the film was found to be 1.8 J/m2.

Wavelength-selective thermal emitters using Si-rods on MgO

NASA Astrophysics Data System (ADS)

Suemitsu, Masahiro; Asano, Takashi; De Zoysa, Menaka; Noda, Susumu

2018-01-01

Supporting substrates for Si rod-type photonic crystals (PCs) are investigated for realizing highly wavelength-selective near-infrared thermal emitters. Three materials—SiO2, Al2O3, and MgO—are considered for their low infrared emission (transparency) and remarkable heat resistance. Theoretical calculations of the emissivity spectra of Si-rod PCs (rod height = 500 nm, rod diameter = 300 nm, and lattice constant = 600 nm) on 50 μm-thick supporting substrates at 1400 K indicate that the long-wavelength (>3 μm) emission power from the emitter using MgO is less than 1/10 of that of the other two materials. Fabrication of the Si-rod PCs on the 50 μm-thick MgO substrate requires the insertion of a thin (30 nm) HfO2 film between MgO and Si to improve the stability at high temperatures (>1400 K). Experimental results of the fabricated structure show that at 1400 K, the ratio of emissive power at wavelengths <1.8 μm to the total emissive power is 34% and that this can be increased to over 53% in an optimized rod-array structure with a 10 μm-thick MgO substrate.

Masking technique for coating thickness control on large and strongly curved aspherical optics.

PubMed

Sassolas, B; Flaminio, R; Franc, J; Michel, C; Montorio, J-L; Morgado, N; Pinard, L

2009-07-01

We discuss a method to control the coating thickness deposited onto large and strongly curved optics by ion beam sputtering. The technique uses an original design of the mask used to screen part of the sputtered materials. A first multielement mask is calculated from the measured two-dimensional coating thickness distribution. Then, by means of an iterative process, the final mask is designed. By using such a technique, it has been possible to deposit layers of tantalum pentoxide having a high thickness gradient onto a curved substrate 500 mm in diameter. Residual errors in the coating thickness profile are below 0.7%.

Plasma spraying method for forming diamond and diamond-like coatings

DOEpatents

Holcombe, Cressie E.; Seals, Roland D.; Price, R. Eugene

1997-01-01

A method and composition for the deposition of a thick layer (10) of diamond or diamond-like material. The method includes high temperature processing wherein a selected composition (12) including at least glassy carbon is heated in a direct current plasma arc device to a selected temperature above the softening point, in an inert atmosphere, and is propelled to quickly quenched on a selected substrate (20). The softened or molten composition (18) crystallizes on the substrate (20) to form a thick deposition layer (10) comprising at least a diamond or diamond-like material. The selected composition (12) includes at least glassy carbon as a primary constituent (14) and may include at least one secondary constituent (16). Preferably, the secondary constituents (16) are selected from the group consisting of at least diamond powder, boron carbide (B.sub.4 C) powder and mixtures thereof.

Three-dimensional architecture for solid state radiation detectors

DOEpatents

Parker, S.

1999-03-30

A radiation-damage resistant radiation detector is formed on a substrate formed of a material doped with a first conductivity type dopant. The detector includes at least one first electrode formed of first conductivity type dopant, and at least one second electrode that is spaced-apart from the first electrode and formed of a second conductivity type dopant. Each first and second electrode penetrates into the substrate from a substrate surface, and one or more electrodes may penetrate entirely through the substrate, that is traversing from one surface to the other surface. Particulate and/or electromagnetic radiation penetrating at least a surface of the substrate releases electrons and holes in substrate regions. Because the electrodes may be formed entirely through the substrate thickness, the released charges will be a relatively small distance from at least a portion of such an electrode, e.g., a distance less than the substrate thickness. The electrons and/or holes traverse the small distance and are collected by said electrodes, thus promoting rapid detection of the radiation. By providing one or more electrodes with a dopant profile radially graded in a direction parallel to a substrate surface, an electric field results that promotes rapid collection of released electrons and said holes. Monolithic combinations of such detectors may be fabricated including CMOS electronics to process radiation signals. 45 figs.

Three-dimensional architecture for solid state radiation detectors

DOEpatents

Parker, Sherwood

1999-01-01

A radiation-damage resistant radiation detector is formed on a substrate formed of a material doped with a first conductivity type dopant. The detector includes at least one first electrode formed of first conductivity type dopant, and at least one second electrode that is spaced-apart from the first electrode and formed of a second conductivity type dopant. Each first and second electrode penetrates into the substrate from a substrate surface, and one or more electrodes may penetrate entirely through the substrate, that is traversing from one surface to the other surface. Particulate and/or electromagnetic radiation penetrating at least a surface of the substrate releases electrons and holes in substrate regions. Because the electrodes may be formed entirely through the substrate thickness, the released charges will be a relatively small distance from at least a portion of such an electrode, e.g., a distance less than the substrate thickness. The electrons and/or holes traverse the small distance and are collected by said electrodes, thus promoting rapid detection of the radiation. By providing one or more electrodes with a dopant profile radially graded in a direction parallel to a substrate surface, an electric field results that promotes rapid collection of released electrons and said holes. Monolithic combinations of such detectors may be fabricated including CMOS electronics to process radiation signals.

Surface figure control for coated optics

DOEpatents

Ray-Chaudhuri, Avijit K.; Spence, Paul A.; Kanouff, Michael P.

2001-01-01

A pedestal optical substrate that simultaneously provides high substrate dynamic stiffness, provides low surface figure sensitivity to mechanical mounting hardware inputs, and constrains surface figure changes caused by optical coatings to be primarily spherical in nature. The pedestal optical substrate includes a disk-like optic or substrate section having a top surface that is coated, a disk-like base section that provides location at which the substrate can be mounted, and a connecting cylindrical section between the base and optics or substrate sections. The optic section has an optical section thickness.sup.2 /optical section diameter ratio of between about 5 to 10 mm, and a thickness variation between front and back surfaces of less than about 10%. The connecting cylindrical section may be attached via three spaced legs or members. However, the pedestal optical substrate can be manufactured from a solid piece of material to form a monolith, thus avoiding joints between the sections, or the disk-like base can be formed separately and connected to the connecting section. By way of example, the pedestal optical substrate may be utilized in the fabrication of optics for an extreme ultraviolet (EUV) lithography imaging system, or in any optical system requiring coated optics and substrates with reduced sensitivity to mechanical mounts.

Thermal Residual Stress in Environmental Barrier Coated Silicon Nitride - Modeled

NASA Technical Reports Server (NTRS)

Ali, Abdul-Aziz; Bhatt, Ramakrishna T.

2009-01-01

When exposed to combustion environments containing moisture both un-reinforced and fiber reinforced silicon based ceramic materials tend to undergo surface recession. To avoid surface recession environmental barrier coating systems are required. However, due to differences in the elastic and thermal properties of the substrate and the environmental barrier coating, thermal residual stresses can be generated in the coated substrate. Depending on their magnitude and nature thermal residual stresses can have significant influence on the strength and fracture behavior of coated substrates. To determine the maximum residual stresses developed during deposition of the coatings, a finite element model (FEM) was developed. Using this model, the thermal residual stresses were predicted in silicon nitride substrates coated with three environmental coating systems namely barium strontium aluminum silicate (BSAS), rare earth mono silicate (REMS) and earth mono di-silicate (REDS). A parametric study was also conducted to determine the influence of coating layer thickness and material parameters on thermal residual stress. Results indicate that z-direction stresses in all three systems are small and negligible, but maximum in-plane stresses can be significant depending on the composition of the constituent layer and the distance from the substrate. The BSAS and REDS systems show much lower thermal residual stresses than REMS system. Parametric analysis indicates that in each system, the thermal residual stresses can be decreased with decreasing the modulus and thickness of the coating.

Effect of substrate on the atomic structure and physical properties of thermoelectric Ca3Co4O9 thin films

NASA Astrophysics Data System (ADS)

Qiao, Q.; Gulec, A.; Paulauskas, T.; Kolesnik, S.; Dabrowski, B.; Ozdemir, M.; Boyraz, C.; Mazumdar, D.; Gupta, A.; Klie, R. F.

2011-08-01

The incommensurately layered cobalt oxide Ca3Co4O9 exhibits an unusually high Seebeck coefficient as a polycrystalline bulk material, making it ideally suited for many high temperature thermoelectric applications. In this paper, we investigate properties of Ca3Co4O9 thin films grown on cubic perovskite SrTiO3, LaAlO3, and (La0.3Sr0.7)(Al0.65Ta0.35)O3 substrates and on hexagonal Al2O3 (sapphire) substrates using the pulsed laser deposition technique. X-ray diffraction and transmission electron microscopy analysis indicate strain-free growth of films, irrespective of the substrate. However, depending on the lattice and symmetry mismatch, defect-free growth of the hexagonal CoO2 layer is stabilized only after a critical thickness and, in general, we observe the formation of a stable Ca2CoO3 buffer layer near the substrate-film interface. Beyond this critical thickness, a large concentration of CoO2 stacking faults is observed, possibly due to weak interlayer interaction in this layered material. We propose that these stacking faults have a significant impact on the Seebeck coefficient and we report higher values in thinner Ca3Co4O9 films due to additional phonon scattering sites, necessary for improved thermoelectric properties.

Effect of substrate on the atomic structure and physical properties of thermoelectric Ca₃Co₄O₉ thin films.

PubMed

Qiao, Q; Gulec, A; Paulauskas, T; Kolesnik, S; Dabrowski, B; Ozdemir, M; Boyraz, C; Mazumdar, D; Gupta, A; Klie, R F

2011-08-03

The incommensurately layered cobalt oxide Ca(3)Co(4)O(9) exhibits an unusually high Seebeck coefficient as a polycrystalline bulk material, making it ideally suited for many high temperature thermoelectric applications. In this paper, we investigate properties of Ca(3)Co(4)O(9) thin films grown on cubic perovskite SrTiO(3), LaAlO(3), and (La(0.3)Sr(0.7))(Al(0.65)Ta(0.35))O(3) substrates and on hexagonal Al(2)O(3) (sapphire) substrates using the pulsed laser deposition technique. X-ray diffraction and transmission electron microscopy analysis indicate strain-free growth of films, irrespective of the substrate. However, depending on the lattice and symmetry mismatch, defect-free growth of the hexagonal CoO(2) layer is stabilized only after a critical thickness and, in general, we observe the formation of a stable Ca(2)CoO(3) buffer layer near the substrate-film interface. Beyond this critical thickness, a large concentration of CoO(2) stacking faults is observed, possibly due to weak interlayer interaction in this layered material. We propose that these stacking faults have a significant impact on the Seebeck coefficient and we report higher values in thinner Ca(3)Co(4)O(9) films due to additional phonon scattering sites, necessary for improved thermoelectric properties.

Lower-Conductivity Ceramic Materials for Thermal-Barrier Coatings

NASA Technical Reports Server (NTRS)

Bansal, Narottam P.; Zhu, Dongming

2006-01-01

Doped pyrochlore oxides of a type described below are under consideration as alternative materials for high-temperature thermal-barrier coatings (TBCs). In comparison with partially-yttria-stabilized zirconia (YSZ), which is the state-of-the-art TBC material now in commercial use, these doped pyrochlore oxides exhibit lower thermal conductivities, which could be exploited to obtain the following advantages: For a given difference in temperature between an outer coating surface and the coating/substrate interface, the coating could be thinner. Reductions in coating thicknesses could translate to reductions in weight of hot-section components of turbine engines (e.g., combustor liners, blades, and vanes) to which TBCs are typically applied. For a given coating thickness, the difference in temperature between the outer coating surface and the coating/substrate interface could be greater. For turbine engines, this could translate to higher operating temperatures, with consequent increases in efficiency and reductions in polluting emissions. TBCs are needed because the temperatures in some turbine-engine hot sections exceed the maximum temperatures that the substrate materials (superalloys, Si-based ceramics, and others) can withstand. YSZ TBCs are applied to engine components as thin layers by plasma spraying or electron-beam physical vapor deposition. During operation at higher temperatures, YSZ layers undergo sintering, which increases their thermal conductivities and thereby renders them less effective as TBCs. Moreover, the sintered YSZ TBCs are less tolerant of stress and strain and, hence, are less durable.

Oxidation resistant slurry coating for carbon-based materials

NASA Technical Reports Server (NTRS)

Smialek, J. L.; Rybicki, G. C. (Inventor)

1985-01-01

An oxidation resistant coating is produced on carbon-base materials, and the same processing step effects an infiltration of the substrate with silicon containing material. The process comprises making a slurry of nickel and silicon powders in a nitrocellulose lacquer, spraying onto the graphite or carbon-carbon substrate, and sintering in vacuum to form a fused coating that wets and covers the surface as well as penetrates into the pores of the substrate. Optimum wetting and infiltration occurs in the range of Ni-60 w/o Si to Ni-90 w/o Si with deposited thicknesses of 25-100 mg/sq. cm. Sintering temperatures of about 1200 C to about 1400 C are used, depending on the melting point of the specific coating composition. The sintered coating results in Ni-Si intermetallic phases and SiC, both of which are highly oxidation resistant.

High Temperature Superconducting Thick Films

DOEpatents

Arendt, Paul N.; Foltyn, Stephen R.; Groves, James R.; Holesinger, Terry G.; Jia, Quanxi

2005-08-23

An article including a substrate, a layer of an inert oxide material upon the surface of the substrate, (generally the inert oxide material layer has a smooth surface, i.e., a RMS roughness of less than about 2 nm), a layer of an amorphous oxide or oxynitride material upon the inert oxide material layer, a layer of an oriented cubic oxide material having a rock-salt-like structure upon the amorphous oxide material layer is provided together with additional layers such as at least one layer of a buffer material upon the oriented cubic oxide material layer or a HTS top-layer of YBCO directly upon the oriented cubic oxide material layer. With a HTS top-layer of YBCO upon at least one layer of a buffer material in such an article, Jc's of 1.4×106 A/cm2 have been demonstrated with projected Ic's of 210 Amperes across a sample 1 cm wide.

Visible/near-infrared spectrogoniometric observations and modeling of dust-coated rocks

USGS Publications Warehouse

Johnson, J. R.; Grundy, W.M.; Shepard, M.K.

2004-01-01

Interpretations of visible/near-infrared reflectance spectra of Mars are often complicated by the effects of dust coatings that obscure the underlying materials of interest. The ability to separate the spectral reflectance signatures of coatings and substrates requires an understanding of how their individual and combined reflectance properties vary with phase angle. Toward this end, laboratory multispectral observations of rocks coated with different amounts of Mars analog dust were acquired under variable illumination and viewing geometries using the Bloomsburg University Goniometer (BUG). These bidirectional reflectance distribution function (BRDF) data were fit with a two-layer radiative transfer model, which replicated BUG observations of dust-coated basaltic andesite substrates relatively well. Derived single scattering albedo and phase function parameters for the dust were useful in testing the model's ability to derive the spectrum of a "blind" substrate (unknown to the modeler) coated with dust. Subsequent tests were run using subsets of the BUG data restricted by goniometric or coating thickness coverage. Using the entire data set provided the best constraints on model parameters, although some reductions in goniometric coverage could be tolerated without substantial degradation. Predictably, the most thinly coated samples provided the best information on the substrate, whereas the thickest coatings best replicated the dust. Dust zenith optical thickness values ???0.6-0.8 best constrain the substrate and coating simultaneously, particularly for large ranges of incidence or emission angles. The lack of sufficient angles can be offset by having a greater number and range of coatings thicknesses. Given few angles and thicknesses, few constraints can be placed concurrently on the spectral properties of the coating and substrate. ?? 2004 Elsevier Inc. All rights reserved.

Tunable Microwave Transversal Filters.

DTIC Science & Technology

1984-05-01

magnetostatic waves MSW propagating at microwave frequency in magnetically biased, liquid phase epitaxial films of yttrium iron garnet (YIG) grown on...25 uM-thick 3 mm-wide and 15 mm-long YIG film grown by liquid phase epitaxy On a 500 uM-thick ( ) gadolinium gallium garnet (GGG) substrate was used...obtained. The delay line material was prepared by growing YIG films on one inch diameter gallium gadolinium garnet (GGG) wafers using the liquid

Mechanical properties of thin-film materials evaluated from amplitude-dependent internal friction

NASA Astrophysics Data System (ADS)

Nishino, Yoichi

1999-09-01

A method is presented to evaluate the mechanical properties of thin-film materials from measurements of the amplitude-dependent internal friction. According to the constitutive equation, the internal friction in the film can be determined separately from measured damping of the film/substrate composite. The internal friction in aluminum films is dependent on the strain amplitude that is approximately two orders of magnitude higher than that for bulk aluminum. On the basis of the microplasticity theory, the amplitude-dependent internal friction in the film can be converted into the plastic strain as a function of effective stress on dislocation motion. The mechanical responses thus obtained for aluminum films show that the plastic strain of the order of 10-9 increases nonlinearly with increasing stress. These curves tend to shift to a higher stress with decreasing film thickness and also with decreasing temperature, both indicating a suppression of microplastic flow. The microflow stress at a constant level of the plastic strain varies inversely with the film thickness, provided the grain size is larger than the film thickness. The film thickness effect in the microplastic range can be well explained by the bowing of a dislocation segment whose ends are pinned at the film surface and at the film/substrate interface.

High efficiency low cost thin film silicon solar cell design and method for making

DOEpatents

Sopori, B.L.

1999-04-27

A semiconductor device is described having a substrate, a conductive intermediate layer deposited onto said substrate, wherein the intermediate layer serves as a back electrode, an optical reflector, and an interface for impurity gettering, and a semiconductor layer deposited onto said intermediate layer, wherein the semiconductor layer has a grain size at least as large as the layer thickness, and preferably about ten times the layer thickness. The device is formed by depositing a metal layer on a substrate, depositing a semiconductive material on the metal-coated substrate to produce a composite structure, and then optically processing the composite structure by illuminating it with infrared electromagnetic radiation according to a unique time-energy profile that first produces pits in the backside surface of the semiconductor material, then produces a thin, highly reflective, low resistivity alloy layer over the entire area of the interface between the semiconductor material and the metal layer, and finally produces a grain-enhanced semiconductor layer. The time-energy profile includes increasing the energy to a first energy level to initiate pit formation and create the desired pit size and density, then ramping up to a second energy level in which the entire device is heated to produce an interfacial melt, and finally reducing the energy to a third energy level and holding for a period of time to allow enhancement in the grain size of the semiconductor layer. 9 figs.

Antireflective coatings with adjustable refractive index and porosity synthesized by micelle-templated deposition of MgF2 sol particles.

PubMed

Bernsmeier, Denis; Polte, Jörg; Ortel, Erik; Krahl, Thoralf; Kemnitz, Erhard; Kraehnert, Ralph

2014-11-26

Minimizing efficiency losses caused by unwanted light reflection at the interface between lenses, optical instruments and solar cells with the surrounding medium requires antireflective coatings with adequate refractive index and coating thickness. We describe a new type of antireflective coating material with easily and independently tailorable refractive index and coating thickness based on the deposition of colloidal MgF2 nanoparticles. The material synthesis employs micelles of amphiphilic block copolymers as structure directing agent to introduce controlled mesoporosity into MgF2 film. The coatings thickness can be easily adjusted by the applied coating conditions. The coatings refractive index is determined by the materials porosity, which is controlled by the amount of employed pore template. The refractive index can be precisely tuned between 1.23 and 1.11, i.e., in a range that is not accessible to nonporous inorganic materials. Hence, zero reflectance conditions can be established for a wide range of substrate materials.

Printed circuit board impedance matching step for microwave (millimeter wave) devices

DOEpatents

Pao, Hsueh-Yuan; Aguirre, Jerardo; Sargis, Paul

2013-10-01

An impedance matching ground plane step, in conjunction with a quarter wave transformer section, in a printed circuit board provides a broadband microwave matching transition from board connectors or other elements that require thin substrates to thick substrate (>quarter wavelength) broadband microwave (millimeter wave) devices. A method of constructing microwave and other high frequency electrical circuits on a substrate of uniform thickness, where the circuit is formed of a plurality of interconnected elements of different impedances that individually require substrates of different thicknesses, by providing a substrate of uniform thickness that is a composite or multilayered substrate; and forming a pattern of intermediate ground planes or impedance matching steps interconnected by vias located under various parts of the circuit where components of different impedances are located so that each part of the circuit has a ground plane substrate thickness that is optimum while the entire circuit is formed on a substrate of uniform thickness.

Modeling Visible/Near-Infrared Photometric Properties of Dustfall on a Known Substrate

NASA Technical Reports Server (NTRS)

Sohl-Dickstein, J.; Johnson, J. R.; Grundy, W. M.; Guinness, E.; Graff, T.; Shepard, M. K.; Arvidson, R. E.; Bell, J. F., III; Christensen, P.; Morris, R.

2005-01-01

We present a comprehensive visible/near-infrared two-layer radiative transfer modeling study using laboratory spectra of variable dust thicknesses deposited on substrates with known photometric parameters. The masking effects of Martian airfall dust deposition on rocks, soils, and lander/rover components provides the incentive to improve two-layer models [1-3]. It is believed that the model presented will facilitate understanding of the spectral and compositional properties of both the dust layer and substrate material, and allow for better compensation for dust deposition.

Two-dimensional electron beam charging model for polymer films

NASA Technical Reports Server (NTRS)

Reeves, R. D.; Balmain, K. G.

1981-01-01

A two-dimensional model is developed to describe the charging of strips of thin polymer films above a grounded substrate exposed to a uniform mono-energetic electron beam. The study is motivated by the observed anomalous behavior of geosynchronous satellites, which has been attributed to differential charging of the satellite surfaces exposed to magnetospheric electrons. Surface and bulk electric fields are calcuated at steady state in order to identify regions of high electrical stress, with emphasis on behavior near the material's edge. The model is used to study the effects of some of the experimental parameters, notably beam energy, beam angle of incidence, beam current density, material thickness and material width. Also examined are the consequences of a central gap in the material and a discontinuity in the material thickness.

PVA with nopal dye as holographic recording material

NASA Astrophysics Data System (ADS)

Toxqui-López, S.; Olivares-Pérez, A.; Fuentes-Tapia, I.; Pinto-Iguanero, B.

2011-09-01

Cactus nopal dye is introduced into a polyvinyl alcohol matrix achieving a like brown appearance thick film, such that they can be used as a recording medium. This dye material provides excellent property as photosensitizer, i.e., easy handling, low cost and can be used in real time holographic recording applications. The experimental results show the diffraction efficiencies obtained by recording grating patterns induced by a He-Cd laser (442nm). For the samples, a thick film of polyvinyl alcohol and dye from cactus nopal was deposited by the gravity technique on a glass substrate. This mixture dries to form a photosensitive emulsion.

Microelectronic components and metallic oxide studies and applications

NASA Technical Reports Server (NTRS)

Williams, L., Jr.

1976-01-01

The project involved work in two basic areas: (1) Evaluation of commercial screen printable thick film conductors, resistors, thermistors and dielectrics as well as alumina substrates used in hybird microelectronics industries. Results of tests made on materials produced by seven companies are presented. (2) Experimental studies on metallic oxides of copper and vanadium, in an effort to determine their electrochemical properties in crystalline, powder mixtures and as screen printable thick films constituted the second phase of the research effort. Oxide investigations were aimed at finding possible applications of these materials as switching devices memory elements and sensors.

Enhanced off-resonance magnetoelectric response in laser annealed PZT thick film grown on magnetostrictive amorphous metal substrate

NASA Astrophysics Data System (ADS)

Palneedi, Haribabu; Maurya, Deepam; Kim, Gi-Yeop; Priya, Shashank; Kang, Suk-Joong L.; Kim, Kwang-Ho; Choi, Si-Young; Ryu, Jungho

2015-07-01

A highly dense, 4 μm-thick Pb(Zr,Ti)O3 (PZT) film is deposited on amorphous magnetostrictive Metglas foil (FeBSi) by granule spray in vacuum process at room temperature, followed by its localized annealing with a continuous-wave 560 nm ytterbium fiber laser radiation. This longer-wavelength laser radiation is able to anneal the whole of thick PZT film layer without any deteriorative effects, such as chemical reaction and/or atomic diffusion, at the interface and crystallization of amorphous Metglas substrate. Greatly enhanced dielectric and ferroelectric properties of the annealed PZT are attributed to its better crystallinity and grain growth induced by laser irradiation. As a result, a colossal off-resonance magnetoelectric (ME) voltage coefficient that is two orders of magnitude larger than previously reported output from PZT/Metglas film-composites is achieved. The present work addresses the problems involved in the fabrication of PZT/Metglas film-composites and opens up emerging possibilities in employing piezoelectric materials with low thermal budget substrates (suitable for integrated electronics) and designing laminate composites for ME based devices.

Influence of soft ferromagnetic substrate on magneto-elastic behavior in a superconducting coated conductor strip

NASA Astrophysics Data System (ADS)

He, An; Xue, Cun; Yong, Huadong; Zhou, Youhe

2013-11-01

Ferromagnetic materials will affect not only the electromagnetic response but also the mechanical behaviors of coated conductors. The influence of soft ferromagnetic substrate on magneto-elastic behavior in a superconductor/ferromagnetic (SC/FM) bilayer exposed to a transverse magnetic field is investigated theoretically. The ferromagnetic substrate is regarded as ideal soft magnets with high permeability and small magnetic hysteresis. Due to the composite structure of SC/FM hybrids, magneto-elastic behavior will be subjected to combined effect of equivalent force and flexural moment. Analytical expressions for internal stress and strain components are derived by virtue of a two-dimensional elasticity analysis. It is worth pointing out that the y component of strain has much larger positive value during field ascent, which may result in the delamitation at the interface. Irreversible magnetostrictive behaviors are observed both along x direction and along y direction. For the thickness dependence of magnetostriction, the flexural moment dominates when the SC thickness is small while the equivalent force plays a critical role at higher SC thickness.

Measurement of Thicknesses of High-κ Gate-Dielectric Films on Silicon by Angle-Resolved XPS

NASA Astrophysics Data System (ADS)

Powell, Cedric; Smekal, Werner; Werner, Wolfgang

2006-03-01

We report on the use of a new NIST database for the Simulation of Electron Spectra for Surface Analysis (SESSA) in measuring thicknesses of candidate high-κ gate-dielectric materials (HfO2, HfSiO4, ZrO2, and ZrSiO4) on silicon by angle-resolved XPS. For conventional measurements of film thicknesses, effective attenuation lengths (EALs) have been computed for these materials from SESSA as a function of film thickness and photoelectron emission angle (i.e., to simulate the effects of tilting the sample). These EALs are believed to be more accurate than similar EALs obtained from the transport approximation because realistic cross sections are used for both elastic and inelastic scattering in the film and substrate materials. We also present ``calibration curves'' showing calculated ratios of selected photoelectron intensities from thin films of HfO2 on Si with an intermediate SiO2 layer. These ratios provide a simple and convenient means of determining the thicknesses of SiO2 and HfO2 films for particular measurement conditions.

Effect of substrate roughness on the corrosion behaviour of the Al2O3/MA 956 system.

PubMed

García-Alonso, M C; Escudero, M L; González-Carrasco, J L; Chao, J

2000-01-01

This paper presents the influence of substrate roughness on the corrosion behaviour of the Al2O3/MA 956 system. An alumina layer of thickness 1-5 microm was generated of the MA956 alloy by thermal oxidation at 1100 degrees C using different exposure times. This Al2O3/MA 956 system with a polished substrate has shown excellent corrosion behaviour in a physiological fluid, due to the fact that the alpha-Al2O3 layer formed is dense, continuous and firmly adhered to the substrate, irrespective of the scale thickness. This good adherence allows it to withstand potentials above 1.7 V. Specimens with rough finish substrate and treatment times above 10 h present spallation of the alumina layer at the crests of the roughness profile. In this case a mixed corrosion behaviour between an alumina coated material and one with a passive layer is observed. In both types of specimens, rough and smooth, once the passivation layer is broken the repassivation capacity of the substrate is ensured due to the high chromium content of the alloy, under oxygenation conditions.

Electroless atomic layer deposition

DOEpatents

Robinson, David Bruce; Cappillino, Patrick J.; Sheridan, Leah B.; Stickney, John L.; Benson, David M.

2017-10-31

A method of electroless atomic layer deposition is described. The method electrolessly generates a layer of sacrificial material on a surface of a first material. The method adds doses of a solution of a second material to the substrate. The method performs a galvanic exchange reaction to oxidize away the layer of the sacrificial material and deposit a layer of the second material on the surface of the first material. The method can be repeated for a plurality of iterations in order to deposit a desired thickness of the second material on the surface of the first material.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Uribe, Fernando; Vianco, Paul Thomas; Zender, Gary L.

A study was performed that examined the microstructure and mechanical properties of 63Sn-37Pb (wt.%, Sn-Pb) solder joints made to thick film layers on low-temperature co-fired (LTCC) substrates. The thick film layers were combinations of the Dupont{trademark} 4596 (Au-Pt-Pd) conductor and Dupont{trademark} 5742 (Au) conductor, the latter having been deposited between the 4596 layer and LTCC substrate. Single (1x) and triple (3x) thicknesses of the 4596 layer were evaluated. Three footprint sizes were evaluated of the 5742 thick film. The solder joints exhibited excellent solderability of both the copper (Cu) lead and thick film surface. In all test sample configurations, themore » 5742 thick film prevented side wall cracking of the vias. The pull strengths were in the range of 3.4-4.0 lbs, which were only slightly lower than historical values for alumina (Al{sub 2}O{sub 3}) substrates. General (qualitative) observations: (a) The pull strength was maximized when the total number of thick film layers was between two and three. Fewer that two layers did not develop as strong of a bond at the thick film/LTCC interface; more than three layers and of increased footprint area, developed higher residual stresses at the thick film/LTCC interface and in the underlying LTCC material that weakened the joint. (b) Minimizing the area of the weaker 4596/LTCC interface (e.g., larger 5742 area) improved pull strength. Specific observations: (a) In the presence of vias and the need for the 3x 4596 thick film, the preferred 4596:5742 ratio was 1.0:0.5. (b) For those LTCC components that require the 3x 4596 layer, but do not have vias, it is preferred to refrain from using the 5742 layer. (c) In the absence of vias, the highest strength was realized with a 1x thick 5742 layer, a 1x thick 4596 layer, and a footprint ratio of 1.0:1.0.« less

Condensing Heat Exchanger with Hydrophilic Antimicrobial Coating

NASA Technical Reports Server (NTRS)

Thomas, Christopher M. (Inventor); Ma, Yonghui (Inventor)

2014-01-01

A multi-layer antimicrobial hydrophilic coating is applied to a substrate of anodized aluminum, although other materials may form the substrate. A silver layer is sputtered onto a thoroughly clean anodized surface of the aluminum to about 400 nm thickness. A layer of crosslinked, silicon-based macromolecular structure about 10 nm thickness overlies the silver layer, and the outermost surface of the layer of crosslinked, silicon-based macromolecular structure is hydroxide terminated to produce a hydrophilic surface with a water drop contact angle of less than 10.degree.. The coated substrate may be one of multiple fins in a condensing heat exchanger for use in the microgravity of space, which has narrow channels defined between angled fins such that the surface tension of condensed water moves water by capillary flow to a central location where it is pumped to storage. The antimicrobial coating prevents obstruction of the capillary passages.

Structural Evolution of Low-Molecular-Weight Poly(ethylene oxide)-block-polystyrene Diblock Copolymer Thin Film

PubMed Central

Huang, Xiaohua

2013-01-01

The structural evolution of low-molecular-weight poly(ethylene oxide)-block-polystyrene (PEO-b-PS) diblock copolymer thin film with various initial film thicknesses on silicon substrate under thermal annealing was investigated by atomic force microscopy, optical microscopy, and contact angle measurement. At film thickness below half of the interlamellar spacing of the diblock copolymer (6.2 nm), the entire silicon is covered by a polymer brush with PEO blocks anchored on the Si substrate due to the substrate-induced effect. When the film is thicker than 6.2 nm, a dense polymer brush which is equal to half of an interlamellar layer was formed on the silicon, while the excess material dewet this layer to form droplets. The droplet surface was rich with PS block and the PEO block crystallized inside the bigger droplet to form spherulite. PMID:24302862

Monolithic 20W 2GHz Transistor and Monolithic 5W 4GHz Transistor.

DTIC Science & Technology

1979-02-01

epitaxial material of better quality than has been obtained from outside vendors . Ini tial tests indicate that the intrinsic material grown in our...system exceeds 800~ —cm , which is at least twice the value required . Also , the correct substrate material will be used and the N buried layer will...be the correct resistivity and thickness. The N layer will also be deposited somewhat thinner than the exist- ing material to reduce the collector

Influence of substrate temperatures on the properties of GdF(3) thin films with quarter-wave thickness in the ultraviolet region.

PubMed

Jin, Jingcheng; Jin, Chunshui; Li, Chun; Deng, Wenyuan; Yao, Shun

2015-06-01

High-quality coatings of fluoride materials are in extraordinary demand for use in deep ultraviolet (DUV) lithography. Gadolinium fluoride (GdF₃) thin films were prepared by a thermal boat evaporation process at different substrate temperatures. GdF₃ thin film was set at quarter-wave thickness (∼27  nm) with regard to their common use in DUV/vacuum ultraviolet optical stacks; these thin films may significantly differ in nanostructural properties at corresponding depositing temperatures, which would crucially influence the performance of the multilayers. The measurement and analysis of optical, structural, and mechanical properties of GdF₃ thin films have been performed in a comprehensive characterization cycle. It was found that depositing GdF₃ thin films at relative higher temperature would form a rather dense, smooth, homogeneous structure within this film thickness scale.

Boron carbide coating deposition on tungsten and testing of tungsten layers and coating under intense plasma load

DOE Office of Scientific and Technical Information (OSTI.GOV)

Airapetov, A. A.; Begrambekov, L. B., E-mail: lbb@plasma.mephi.ru; Buzhinskiy, O. I.

2015-12-15

A device intended for boron carbide coating deposition and material testing under high heat loads is presented. A boron carbide coating 5 μm thick was deposited on the tungsten substrate. These samples were subjected to thermocycling loads in the temperature range of 400–1500°C. Tungsten layers deposited on tungsten substrates were tested in similar conditions. Results of the surface analysis are presented.

Deposition and Characterization of HVOF Thermal Sprayed Functionally Graded Coatings Deposited onto a Lightweight Material

NASA Astrophysics Data System (ADS)

Hasan, M.; Stokes, J.; Looney, L.; Hashmi, M. S. J.

2009-02-01

There is a significant interest in lightweight materials (like aluminum, magnesium, titanium, and so on) containing a wear resistance coating, in such industries as the automotive industry, to replace heavy components with lighter parts in order to decrease vehicle weight and increase fuel efficiency. Functionally graded coatings, in which the composition, microstructure, and/or properties vary gradually from the bond coat to the top coat, may be applied to lightweight materials, not only to decrease weight, but also to enhance components mechanical properties by ensuring gradual microstructural (changes) together with lower residual stress. In the current work, aluminum/tool-steel functionally graded coatings were deposited onto lightweight aluminum substrates. The graded coatings were then characterized in terms of residual stress and hardness. Results show that residual stress increased with an increase in deposition thickness and a decrease in number of layers. However, the hardness also increased with an increase in deposition thickness and decrease in number of layers. Therefore, an engineer must compromise between the hardness and stress values while designing a functionally graded coating-substrate system.

Material growth and characterization directed toward improving III-V heterojunction solar cells

NASA Technical Reports Server (NTRS)

Stefanakos, E. K.; Alexander, W. E.; Collis, W.; Abul-Fadl, A.

1979-01-01

In addition to the existing materials growth laboratory, the photolithographic facility and the device testing facility were completed. The majority of equipment for data acquisition, solar cell testing, materials growth and device characterization were received and are being put into operation. In the research part of the program, GaAs and GaA1As layers were grown reproducibly on GaAs substrates. These grown layers were characterized as to surface morphology, thickness and thickness uniformity. The liquid phase epitaxial growth process was used to fabricate p-n junctions in Ga(1-x)A1(x)As. Sequential deposition of two alloy layers was accomplished and detailed analysis of the effect of substrate quality and dopant on the GaA1As layer quality is presented. Finally, solar cell structures were formed by growing a thin p-GaA1As layer upon an epitaxial n-GaA1As layer. The energy gap corresponding to the long wavelength cutoff of the spectral response characteristic was 1.51-1.63 eV. Theoretical calculations of the spectral response were matched to the measured response.

Polymer nanomechanics: Separating the size effect from the substrate effect in nanoindentation

NASA Astrophysics Data System (ADS)

Li, Le; Encarnacao, Lucas M.; Brown, Keith A.

2017-01-01

While the moduli of thin polymer films are known to deviate dramatically from their bulk values, there is not a consensus regarding the nature of this size effect. In particular, indenting experiments appear to contradict results from both buckling experiments and molecular dynamics calculations. In this letter, we present a combined computational and experimental method for measuring the modulus of nanoindented soft films on rigid substrates that reconciles this discrepancy. Through extensive finite element simulation, we determine a correction to the Hertzian contact model that separates the substrate effect from the thickness-dependent modulus of the film. Interestingly, this correction only depends upon a dimensionless film thickness and the Poisson ratio of the film. To experimentally test this approach, we prepared poly(methyl methacrylate), polystyrene, and parylene films with thicknesses ranging from 20 to 300 nm and studied these films using atomic force microscope-based nanoindenting. Strikingly, when experiments were interpreted using the computationally derived substrate correction, sub-70 nm films were found to be softer than bulk, in agreement with buckling experiments and molecular dynamics studies. This correction can serve as a general method for unambiguously determining the size effect of thin polymer films and ultimately lead to the ability to quantitatively image the mechanical properties of heterogeneous materials such as composites.

Acoustic backing in 3-D integration of CMUT with front-end electronics.

PubMed

Berg, Sigrid; Rønnekleiv, Arne

2012-07-01

Capacitive micromachined ultrasonic transducers (CMUTs) have shown promising qualities for medical imaging. However, there are still some problems to be investigated, and some challenges to overcome. Acoustic backing is necessary to prevent SAWs excited in the surface of the silicon substrate from affecting the transmit pattern from the array. In addition, echoes resulting from bulk waves in the substrate must be removed. There is growing interest in integrating electronic circuits to do some of the beamforming directly below the transducer array. This may be easier to achieve for CMUTs than for traditional piezoelectric transducers. We will present simulations showing that the thickness of the silicon substrate and thicknesses and acoustic properties of the bonding material must be considered, especially when designing highfrequency transducers. Through simulations, we compare the acoustic properties of 3-D stacks bonded with three different bonding techniques; solid-liquid interdiffusion (SLID) bonding, direct fusion bonding, and anisotropic conductive adhesives (ACA). We look at a CMUT array with a center frequency of 30 MHz and three silicon wafers underneath, having a total silicon thickness of 100 μm. We find that fusion bonding is most beneficial if we want to prevent surface waves from damaging the array response, but SLID and ACA are also promising if bonding layer thicknesses can be reduced.

RFID and Memory Devices Fabricated Integrally on Substrates

NASA Technical Reports Server (NTRS)

Schramm, Harry F.

2004-01-01

Electronic identification devices containing radio-frequency identification (RFID) circuits and antennas would be fabricated integrally with the objects to be identified, according to a proposal. That is to say, the objects to be identified would serve as substrates for the deposition and patterning of the materials of the devices used to identify them, and each identification device would be bonded to the identified object at the molecular level. Vacuum arc vapor deposition (VAVD) is the NASA derived process for depositing layers of material on the substrate. This proposal stands in contrast to the current practice of fabricating RFID and/or memory devices as wafer-based, self-contained integrated-circuit chips that are subsequently embedded in or attached to plastic cards to make smart account-information cards and identification badges. If one relies on such a chip to store data on the history of an object to be tracked and the chip falls off or out of the object, then one loses both the historical data and the means to track the object and verify its identity electronically. Also, in contrast is the manufacturing philosophy in use today to make many memory devices. Today s methods involve many subtractive processes such as etching. This proposal only uses additive methods, building RFID and memory devices from the substrate up in thin layers. VAVD is capable of spraying silicon, copper, and other materials commonly used in electronic devices. The VAVD process sprays most metals and some ceramics. The material being sprayed has a very strong bond with the substrate, whether that substrate is metal, ceramic, or even wood, rock, glass, PVC, or paper. An object to be tagged with an identification device according to the proposal must be compatible with a vacuum deposition process. Temperature is seldom an issue as the substrate rarely reaches 150 F (66 C) during the deposition process. A portion of the surface of the object would be designated as a substrate for the deposition of the device. By use of a vacuum arc vapor deposition apparatus, a thin electrically insulating film would first be deposited on the substrate. Subsequent layers of materials would then be deposited and patterned by use of known integrated-circuit fabrication techniques. The total thickness of the deposited layers could be much less than the 100- m thickness of the thinnest state-of-the-art self-contained microchips. Such a thin deposit could be readily concealed by simply painting over it. Both large vacuum chambers for production runs and portable hand-held devices for in situ applications are available.

Optical characterization of thin nickel films on polymer substrates using reflectance difference spectroscopy

NASA Astrophysics Data System (ADS)

Rinnerbauer, V.; Schmidegg, K.; Hohage, M.; Sun, L. D.; Flores-Camacho, J. M.; Zeppenfeld, P.

2009-06-01

We have used reflectance difference spectroscopy (RDS) and its extension, azimuth-dependent RDS (ADRDS), to study the properties of sputtered and evaporated nickel films on biaxially oriented poly(ethylene terephtalate) (PET) films in a roll to roll web-coating process. From the full set of ADRDS spectra we extract and analyze both the intrinsic RDS spectra and the azimuthal orientation of the effective optical anisotropy of the samples. From the latter, contributions to the RDS spectra arising from the nickel layer and the PET substrate with different orientations of the optical eigenaxes can be inferred. We find an attenuation of the characteristic RDS signal of the PET substrate with increasing nickel film thickness which is in good agreement with the theoretical prediction. For film thicknesses above 20 nm another contribution to the RDS signal attributed to the optical anisotropy of the deposited nickel layers can be observed. Its strength depends on the deposition method, and is considerably larger for evaporated films than for sputtered ones. With increasing nickel film thickness, the azimuthal orientation of the sample anisotropy changes from the initial value of the PET substrate by about 20° toward the machine direction of the foil. We demonstrate that RDS is also a valuable tool for inline monitoring in the roll to roll process, as the attenuation of the RDS signal, under proper consideration of the orientation of the effective anisotropy, is a function of the film thickness and characteristic for the deposited material.

Influence of residual stress on the adhesion and surface morphology of PECVD-coated polypropylene

NASA Astrophysics Data System (ADS)

Jaritz, Montgomery; Hopmann, Christian; Behm, Henrik; Kirchheim, Dennis; Wilski, Stefan; Grochla, Dario; Banko, Lars; Ludwig, Alfred; Böke, Marc; Winter, Jörg; Bahre, Hendrik; Dahlmann, Rainer

2017-11-01

The properties of plasma-enhanced chemical vapour deposition (PECVD) coatings on polymer materials depend to some extent on the surface and material properties of the substrate. Here, isotactic polypropylene (PP) substrates are coated with silicon oxide (SiO x ) films. Plasmas for the deposition of SiO x are energetic and oxidative due to the high amount of oxygen in the gas mixture. Residual stress measurements using single Si cantilever stress sensors showed that these coatings contain high compressive stress. To investigate the influence of the plasma and the coatings, residual stress, silicon organic (SiOCH) coatings with different thicknesses between the PP and the SiO x coating are used as a means to protect the substrate from the oxidative SiO x coating process. Pull-off tests are performed to analyse differences in the adhesion of these coating systems. It could be shown that the adhesion of the PECVD coatings on PP depends on the coatings’ residual stress. In a PP/SiOCH/SiO x -multilayer system the residual stress can be significantly reduced by increasing the thickness of the SiOCH coating, resulting in enhanced adhesion.

Fluid management in roll-to-roll nanoimprint lithography

NASA Astrophysics Data System (ADS)

Jain, A.; Bonnecaze, R. T.

2013-06-01

The key process parameters of UV roll-to-roll nanoimprint lithography are identified from an analysis of the fluid, curing, and peeling dynamics. The process includes merging of droplets of imprint material, curing of the imprint material from a viscous liquid to elastic solid resist, and pattern replication and detachment of the resist from template. The time and distances on the web or rigid substrate over which these processes occur are determined as function of the physical properties of the uncured liquid, the cured solid, and the roller configuration. The upper convected Maxwell equation is used to model the viscoelastic liquid and to calculate the force on the substrate and the torque on the roller. The available exposure time is found to be the rate limiting parameter and it is O(√Rho /uo), where R is the radius of the roller, ho is minimum gap between the roller and web, and uo is the velocity of the web. The residual layer thickness of the resist should be larger than the gap between the roller and the substrate to ensure complete feature filling and optimal pattern replication. For lower residual layer thickness, the droplets may not merge to form a continuous film for pattern transfer.

Colloidal spray method for low cost thin coating deposition

DOEpatents

Pham, Ai-Quoc; Glass, Robert S.; Lee, Tae H.

2005-01-25

A dense or porous coating of material is deposited onto a substrate by forcing a colloidal suspension through an ultrasonic nebulizer and spraying a fine mist of particles in a carrier medium onto a sufficiently heated substrate. The spraying rate is essentially matched to the evaporation rate of the carrier liquid from the substrate to produce a coating that is uniformly distributed over the surface of the substrate. Following deposition to a sufficient coating thickness, a single sintering step may be used to produce a dense ceramic coating. Using this method, coatings ranging in thickness from about one to several hundred microns can be obtained. By using a plurality of compounds in the colloidal suspension, coatings of mixed composition can be obtained. By using a plurality of solutions and separate pumps and a single or multiple ultrasonic nebulizer(s), and varying the individual pumping rates and/or the concentrations of the solutions, a coating of mixed and discontinuously graded (e.g., stepped) or continuously graded layers may be obtained. This method is particularly useful for depositing ceramic coatings. Dense ceramic coating materials on porous substrates are useful in providing improved electrode performance in devices such as high power density solid oxide fuel cells. Dense ceramic coatings obtained by the invention are also useful for gas turbine blade coatings, sensors, steam electrolyzers, etc. The invention has general use in preparation of systems requiring durable and chemically resistant coatings, or coatings having other specific chemical or physical properties.

Colloidal spray method for low cost thin coating deposition

DOEpatents

Pham, Ai-Quoc; Glass, Robert S.; Lee, Tae H.

2002-01-01

A dense or porous coating of material is deposited onto a substrate by forcing a colloidal suspension through an ultrasonic nebulizer and spraying a fine mist of particles in a carrier medium onto a sufficiently heated substrate. The spraying rate is essentially matched to the evaporation rate of the carrier liquid from the substrate to produce a coating that is uniformly distributed over the surface of the substrate. Following deposition to a sufficient coating thickness, a single sintering step may be used to produce a dense ceramic coating. Using this method, coatings ranging in thickness from about one to several hundred microns can be obtained. By using a plurality of compounds in the colloidal suspension, coatings of mixed composition can be obtained. By using a plurality of solutions and separate pumps and a single or multiple ultrasonic nebulizer(s), and varying the individual pumping rates and/or the concentrations of the solutions, a coating of mixed and discontinuously graded (e.g., stepped) or continuously graded layers may be obtained. This method is particularly useful for depositing ceramic coatings. Dense ceramic coating materials on porous substrates are useful in providing improved electrode performance in devices such as high power density solid oxide fuel cells. Dense ceramic coatings obtained by the invention are also useful for gas turbine blade coatings, sensors, steam electrolyzers, etc. The invention has general use in preparation of systems requiring durable and chemically resistant coatings, or coatings having other specific chemical or physical properties.

Percolation effect in thick film superconductors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sali, R.; Harsanyi, G.

1994-12-31

A thick film superconductor paste has been developed to study the properties of granulated superconductor materials, to observe the percolation effect and to confirm the theory of the conducting mechanism in the superconducting thick films. This paste was also applied to make a superconducting planar transformer. Due to high T{sub c} and advantageous current density properties the base of the paste was chosen to be of Bi(Pb)SrCaCuO system. For contacts a conventional Ag/Pt paste was used. The critical temperature of the samples were between 110 K and 115 K depending on the printed layer thickness. The critical current density atmore » the boiling temperature of the liquid He- was between 200-300 A/cm{sup 2}. The R(T) and V(I) functions were measured with different parameters. The results of the measurements have confirmed the theory of conducting mechanism in the material. The percolation structure model has been built and described. As an application, a superconducting planar thick film transformer was planned and produced. Ten windings of the transformer were printed on one side of the alumina substrate and one winding was printed on the other side. The coupling between the two sides was possible through the substrate. The samples did not need special drying and firing parameters. After the preparation, the properties of the transformer were measured. The efficiency and the losses were determined. Finally, some fundamental advantages and problems of the process were discussed.« less

Percolation effect in thick film superconductors: Using a Bi(Pb)SrCaCuO based paste to prepare a superconducting planar transformer

NASA Technical Reports Server (NTRS)

Sali, Robert; Harsanyi, Gabor

1995-01-01

A thick film superconductor paste has been developed to study the properties of granulated superconductor materials, to observe the percolation effect and to confirm the theory of the conducting mechanism in the superconducting thick films. This paste was also applied to make a superconducting planar transformer. Due to the T(sub c) and advantageous current density properties the base of the past was chosen to be of Bi(Pb)SrCaCu) system. For contacts a conventional Ag/Pt paste was used. The critical temperature of the samples were between 110 K and 115 K depending on the printed layer thickness. The critical current density -at the boiling temperature of the liquid He- was between 200 - 300 A/sq cm. The R(T) and V(I) functions were measured with different parameters. The results of the measurements have confirmed the theory of conducting mechanism in the material. The percolation structure model has been built and described. As an application, a superconducting planar thick film transformer was planned and produced. Ten windings of the transformer were printed on one side of the alumina substrate and one winding was printed on the other side. The coupling between the two sides was possible through the substrate. The samples did not need special drying and firing parameters. After the preparation, the properties of the transformer were measured. The efficiency ans the losses were determined. Finally, some fundamental advantages and problems of the process were discussed.

Thick-film materials for silicon photovoltaic cell manufacture

NASA Technical Reports Server (NTRS)

Field, M. B.

1977-01-01

Thick film technology is applicable to three areas of silicon solar cell fabrication; metallization, junction formation, and coating for protection of screened ohmic contacts, particularly wrap around contacts, interconnection and environmental protection. Both material and process parameters were investigated. Printed ohmic contacts on n- and p-type silicon are very sensitive to the processing parameters of firing time, temperature, and atmosphere. Wrap around contacts are easily achieved by first printing and firing a dielectric over the edge and subsequently applying a low firing temperature conductor. Interconnection of cells into arrays can be achieved by printing and cofiring thick film metal pastes, soldering, or with heat curing conductive epoxies on low cost substrates. Printed (thick) film vitreous protection coatings do not yet offer sufficient optical uniformity and transparency for use on silicon. A sprayed, heat curable SiO2 based resin shows promise of providing both optical matching and environmental protection.

Effect of Sb thickness on the performance of bialkali-antimonide photocathodes

DOE PAGES

Mamun, Md Abdullah A.; Elmustafa, Abdelmageed A.; Hernandez-Garcia, Carlos; ...

2016-01-06

The alkali species Cs and K were codeposited using an effusion source, onto relatively thick layers of Sb (50 nm to ~7 μm) grown on GaAs and Ta substrates inside a vacuum chamber that was baked and not-vented, and also baked and vented with clean dry nitrogen but not rebaked. The characteristics of the Sb films, including sticking probability, surface roughness, grain size, and crystal properties were very different for these conditions, yet comparable values of photocathode yield [or quantum efficiency (QE)] at 284 V were obtained following codeposition of the alkali materials. Photocathodes manufactured with comparatively thick Sb layersmore » exhibited the highest QE and the best 1/e lifetime. As last, the authors speculate that the alkali codeposition enabled optimized stoichiometry for photocathodes manufactured using thick Sb layers, which could serve as a reservoir for the alkali materials.« less

Application of High-Throughput Seebeck Microprobe Measurements on Thermoelectric Half-Heusler Thin Film Combinatorial Material Libraries.

PubMed

Ziolkowski, Pawel; Wambach, Matthias; Ludwig, Alfred; Mueller, Eckhard

2018-01-08

In view of the variety and complexity of thermoelectric (TE) material systems, combinatorial approaches to materials development come to the fore for identifying new promising compounds. The success of this approach is related to the availability and reliability of high-throughput characterization methods for identifying interrelations between materials structures and properties within the composition spread libraries. A meaningful characterization starts with determination of the Seebeck coefficient as a major feature of TE materials. Its measurement, and hence the accuracy and detectability of promising material compositions, may be strongly affected by thermal and electrical measurement conditions. This work illustrates the interrelated effects of the substrate material, the layer thickness, and spatial property distributions of thin film composition spread libraries, which are studied experimentally by local thermopower scans by means of the Potential and Seebeck Microprobe (PSM). The study is complemented by numerical evaluation. Material libraries of the half-Heusler compound system Ti-Ni-Sn were deposited on selected substrates (Si, AlN, Al 2 O 3 ) by magnetron sputtering. Assuming homogeneous properties of a film, significant decrease of the detected thermopower S m can be expected on substrates with higher thermal conductivity, yielding an underestimation of materials thermopower between 15% and 50%, according to FEM (finite element methods) simulations. Thermally poor conducting substrates provide a better accuracy with thermopower underestimates lower than 8%, but suffer from a lower spatial resolution. According to FEM simulations, local scanning of sharp thermopower peaks on lowly conductive substrates is linked to an additional deviation of the measured thermopower of up to 70% compared to homogeneous films, which is 66% higher than for corresponding cases on substrates with higher thermal conductivity of this study.

Pair distribution functions of amorphous organic thin films from synchrotron X-ray scattering in transmission mode

DOE PAGES

Shi, Chenyang; Teerakapibal, Rattavut; Yu, Lian; ...

2017-07-10

Using high-brilliance high-energy synchrotron X-ray radiation, for the first time the total scattering of a thin organic glass film deposited on a strongly scattering inorganic substrate has been measured in transmission mode. The organic thin film was composed of the weakly scattering pharmaceutical substance indomethacin in the amorphous state. The film was 130 µm thick atop a borosilicate glass substrate of equal thickness. The atomic pair distribution function derived from the thin-film measurement is in excellent agreement with that from bulk measurements. This ability to measure the total scattering of amorphous organic thin films in transmission will enable accurate in situmore » structural studies for a wide range of materials.« less

Pair distribution functions of amorphous organic thin films from synchrotron X-ray scattering in transmission mode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shi, Chenyang; Teerakapibal, Rattavut; Yu, Lian

2017-07-10

Using high-brilliance high-energy synchrotron X-ray radiation, for the first time the total scattering of a thin organic glass film deposited on a strongly scattering inorganic substrate has been measured in transmission mode. The organic thin film was composed of the weakly scattering pharmaceutical substance indomethacin in the amorphous state. The film was 130 µm thick atop a borosilicate glass substrate of equal thickness. The atomic pair distribution function derived from the thin-film measurement is in excellent agreement with that from bulk measurements. This ability to measure the total scattering of amorphous organic thin films in transmission will enable accuratein situstructuralmore » studies for a wide range of materials.« less

Materiaux composites supraconducteurs

NASA Astrophysics Data System (ADS)

Kerjouan, Philippe; Boterel, Florence; Lostec, Jean; Bertot, Jean-Paul; Haussonne, Jean-Marie

1991-11-01

The new superconductor materials with a high critical current own a large importance as well in the electronic components or in the electrotechnical devices fields. The deposit of such materials with the thick films technology is to be more and more developped in the years to come. Therefore, we tried to realize such thick films screen printed on alumina, and composed mainly of the YBa2CU3O{7-δ} material. We first realized a composite material glass/YBa2CU3O{7-δ}, by analogy with the classical screen-printed inks where the glass ensures the bonding with the substrate. We thus realized different materials by using some different classes of glass. These materials owned a superconducting transition close to the one of the pure YBa2CU3O{7-δ} material. We made a slurry with the most significant composite materials and binders, and screen-printed them on an alumina substrate preliminary or not coated with a diffusion barrier layer. After firing, we studied the thick films adhesion, the alumina/glass/composite material interfaces, and their superconducting properties. Les nouveaux matériaux supraconducteurs à haute température critique ont potentiellement un rôle important à jouer dans le domaine de l'électronique et de l'électrotechnique. En particulier, le dépôt d'oxydes supraconducteurs sur divers types de substrats est une technologie amenée à se développer. Nous avons donc entrepris une étude dont l'objet est la réalisation de conducteurs sérigraphiés sur alumine et composés essentiellement du matériau YBa2CU3O{7-δ}. Nous avons tout d'abord cherché à réaliser un composite verre/YBa2CU3O{7-δ}, par analogie au principe de réalisation de couches conductrices sérigraphiées, le verre permettant d'obtenir une liaison physico-chimique avec le substrat. Une étude préliminaire a permis de réaliser divers matériaux composites massifs, utilisant différentes familles de verres. Ces matériaux massifs, se présentant sous la forme de barreaux de 2 × 2 mm de section, étaient supraconducteurs à une température pouvant être voisine de celle du matériau YBa2CU3O{7-δ} initial. Nous avons mis les plus significatifs de ces matériaux composites en suspension dans un liant organique nous permettant de les déposer en couches épaisses sur des substrats d'alumine recouverts ou non d'une première couche de verre. Nous avons étudié après cuisson l'adhérence des dépôts, les interfaces alumine/verre/composite, ainsi que les propriétés supraconductrices.

Litho-kinematic facies model for large landslide deposits in arid settings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yarnold, J.C.; Lombard, J.P.

1989-04-01

Reconnaissance field studies of six large landslide deposits in the S. Basin and Range suggest that a set of characteristic features is common to the deposits of large landslides in an arid setting. These include a coarse boulder cap, an upper massive zone, a lower disrupted zone, and a mixed zone overlying disturbed substrate. The upper massive zone is dominated by crackel breccia. This grades downward into a lower disrupted zone composed of a more matrix-rich breccia that is internally sheared, intruded by clastic dikes, and often contains a cataclasite layer at its base. An underlying discontinuous mixed zone ismore » composed of material from the overlying breccia mixed with material entrained from the underlying substrate. Bedding in the substrate sometimes displays folding and contortion that die out downward. The authors work suggests a spatial zonation of these characteristic features within many landslide deposits. In general, clastic dikes, the basal cataclasite, and folding in the substrate are observed mainly in distal parts of landslides. In most cases, total thickness, thickness of the basal disturbed and mixed zones, and the degree of internal shearing increase distally, whereas maximum clast size commonly decreases distally. Zonation of these features is interpreted to result from kinematics of emplacement that cause generally increased deformation in the distal regions of the landslide.« less

Fabrication of a Flexible Amperometric Glucose Sensor Using Additive Processes

PubMed Central

Du, Xiaosong; Durgan, Christopher J.; Matthews, David J.; Motley, Joshua R.; Tan, Xuebin; Pholsena, Kovit; Árnadóttir, Líney; Castle, Jessica R.; Jacobs, Peter G.; Cargill, Robert S.; Ward, W. Kenneth; Conley, John F.; Herman, Gregory S.

2015-01-01

This study details the use of printing and other additive processes to fabricate a novel amperometric glucose sensor. The sensor was fabricated using a Au coated 12.7 μm thick polyimide substrate as a starting material, where micro-contact printing, electrochemical plating, chloridization, electrohydrodynamic jet (e-jet) printing, and spin coating were used to pattern, deposit, chloridize, print, and coat functional materials, respectively. We have found that e-jet printing was effective for the deposition and patterning of glucose oxidase inks with lateral feature sizes between ~5 to 1000 μm in width, and that the glucose oxidase was still active after printing. The thickness of the permselective layer was optimized to obtain a linear response for glucose concentrations up to 32 mM and no response to acetaminophen, a common interfering compound, was observed. The use of such thin polyimide substrates allow wrapping of the sensors around catheters with high radius of curvature ~250 μm, where additive and microfabrication methods may allow significant cost reductions. PMID:26634186

Superheating in coated niobium

NASA Astrophysics Data System (ADS)

Junginger, T.; Wasserman, W.; Laxdal, R. E.

2017-12-01

Using muon spin rotation it is shown that the field of first flux penetration {H}{entry} in Nb is enhanced by about 30% if coated with an overlayer of Nb3Sn or MgB2. This is consistent with an increase from the lower critical magnetic field {H}{{c}1} up to the superheating field {H}{sh} of the Nb substrate. In the experiments presented here coatings of Nb3Sn and MgB2 with a thickness between 50 and 2000 nm have been tested. {H}{entry} does not depend on material or thickness. This suggests that the energy barrier at the boundary between the two materials prevents flux entry up to {H}{sh} of the substrate. A mechanism consistent with these findings is that the proximity effect recovers the stability of the energy barrier for flux penetration, which is suppressed by defects for uncoated samples. Additionally, a low temperature baked Nb sample has been tested. Here a 6% increase of {H}{entry} was found, also pushing {H}{entry} beyond {H}{{c}1}.

Design of laser-driven SiO2-YAG:Ce composite thick film: Facile synthesis, robust thermal performance, and application in solid-state laser lighting

NASA Astrophysics Data System (ADS)

Xu, Jian; Liu, Bingguo; Liu, Zhiwen; Gong, Yuxuan; Hu, Baofu; Wang, Jian; Li, Hui; Wang, Xinliang; Du, Baoli

2018-01-01

In recent times, there have been rapid advances in the solid-state laser lighting technology. Due to the large amounts of heat accumulated from the high flux laser radiation, color conversion materials used in solid-state laser lighting devices should possess high durability, high thermal conductivity, and low thermal quenching. The aim of this study is to develop a thermally robust SiO2-YAG:Ce composite thick film (CTF) for high-power solid-state laser lighting applications. Commercial colloidal silica which was used as the source of SiO2, played the roles of an adhesive, a filler, and a protecting agent. Compared to the YAG:Ce powder, the CTF exhibits remarkable thermal stability (11.3% intensity drop at 200 °C) and durability (4.5% intensity drop after 1000 h, at 85 °C and 85% humidity). Furthermore, the effects of the substrate material and the thickness of the CTF on the laser lighting performance were investigated in terms of their thermal quenching and luminescence saturation behaviors, respectively. The CTF with a thickness of 50 μm on a sapphire substrate does not show luminescence saturation, despite a high-power density of incident radiation i.e. 20 W/mm2. These results demonstrate the potential applicability of the CTF in solid-state laser lighting devices.

Influence of a silicon (Si14)-based coating substrate for biomaterials on fibroblast growth and human C5a.

PubMed

Hiebl, B; Hopperdietzel, C; Hünigen, H; Jung, F; Scharnagl, N

2013-01-01

Despite considerable efforts in biomaterial development there is still a lack on substrates for cardiovascular tissue engineering approaches which allow the establishment of a tight a functional endothelial layer on their surface to provide hemocompatibility. The study aimed to test the biocompatibility of a silicon (Si14)-based coating substrate (Supershine Medicare, Permanon) which was designed to resist temperatures from -40°C up to 300°C and which allows the use of established heat-inducing sterilization techniques respectively. By X-ray photoelectron spectroscopy it could be validated that this substrate is able to establish a 40-50 nm thick layer of silica, oxygen and carbon without including any further elements from the substrate on an exemplary selection of materials (silicone, soda-lime-silica glass, stainless steel). Analysis of the LDH-release, the cell activity/proliferation (MTS assay) and the cell phenotype after growing 3T3 cells with extracts of the coated materials did not indicate any signs of cytotoxicity. Additionally by measuring the C5a release after exposure of the coated materials with human serum it could be demonstrated, that the coating had no impact on the activation of the complement system. These results generally suggest the tested substrate as a promising candidate for the coating of materials which are aimed to be used in cardiovascular tissue engineering approaches.

Voltage control of magnetism in NiZn ferrite/mica/PMNPT heterostructure with giant tunability and narrow linewidth

NASA Astrophysics Data System (ADS)

Wang, Xinjun; Chen, Yunpeng; Chen, Huaihao; Gao, Yuan; He, Yifan; Li, Menghui; Lin, Hwaider; Sun, Neville; Sun, Nian

2018-05-01

Recently, large magnetoelectric coupling of a spinel/piezoelectric heterostructure has been reported. However, the linewidth of the spinel is very large due to lattice mismatch when ferrite is directly deposited on piezoelectric substrates. This indicates a large magnetic loss, which impedes the spinel/piezoelectric heterostructure from useful device applications. Mica is a well-known 2D material, which can be split manually layer by layer without the substrate clamping effect. In this report, NiZn ferrite was deposited on a mica substrate by a spin-spray deposition technique. Spin-spray deposition is a wet chemical synthesis technique involving several chemical reactions for generating high-quality crystalline spinel ferrite films with various compositions directly from an aqueous solution. The thickness of ferrite is 2 μm, and the linewidth of the ferromagnetic resonance (FMR) is 115 Oe which is suitable for RF/microwave devices. The large FMR field tuning of 605 Oe was observed in NiZn ferrite/mica/PMN-PT heterostructures with minimal substrate clamping effect by reducing the thickness of the mica substrate. These multiferroic heterostructures exhibiting combined giant magnetoelectric coupling and narrow ferromagnetic resonance linewidth offer great opportunities for flexible RF magnetic devices.

Process effects resulting from an increased BARC thickness

NASA Astrophysics Data System (ADS)

Eakin, Ronald J.; Detweiler, Shangting F.; Stagaman, Gregory J.; Tesauro, Mark R.; Spak, Mark A.; Dammel, Ralph R.

1997-07-01

Process improvements attributed to the use of bottom anti- reflective coatings (B.A.R.C.s) are well documented. As our experience with these materials improves, so does our understanding of additional optimization. Recent supplier experiments suggest an increase in the thickness of AZR BARLiTM (bottom anti-reflective layer i-line) solution to reduce photoresist swing curve ratios. Also, changes in thin film stack on common substrates can adversely affect the degree of photoresist reflective notching. It is therefore of extreme importance to determine optimum thickness(es) of a B.A.R.C. material to ensure maximum process potential. We document several process effects in the conversion of a SRAM test device (0.38 - 0.45 micrometers) from a 650 angstrom to a 2000 angstrom BARLiTM film thickness using conventional i-line photolithography. Critical dimension (CD) uniformity and depth of focus (DOF) are evaluated. Defect density between the two processes are compared before and after etch employing optical metrology and electrical test structures. Sensitivity of overlay as a function of BARLiTM film thickness is investigated as well.

Composition gradient, structure, stress, roughness and magnetic properties of 5-500 nm thin NiFe films obtained by electrodeposition

NASA Astrophysics Data System (ADS)

Gong, Jie; Riemer, Steve; Kautzky, Michael; Tabakovic, Ibro

2016-01-01

The composition gradients of 5-500 nm thin NiFe films on Cu and NiP substrates obtained by electrodeposition in stirred plating solutions at pH 3.0 on 8 in wafers were studied. It was found that the average elemental composition of the NiFe changes during electrodeposition with steep downturns of Fe-content, from 58 to 50 wt% Fe, in composition gradient zone near the substrate interface in the thickness range 5-250 nm depending on the electrode substrate (Cu and NiP). The increase of Fe-content in the composition gradient zone is accompanied by the increase of coercivity, Hc, magnetic flux saturation, Bs, saturation magnetostriction, λs, increase of dimensionless roughness, ρrms, and change of stress, σ. The coercivity (easy and hard axis) follows the Neel's relation Hc=ct-n (t is thickness and c is a constant). The mechanisms related to the change of coercivity of the NiFe films deposited on different substrates (Cu and NiP) are discussed in terms of material properties of these films.

Ultra-thin distributed Bragg reflectors via stacked single-crystal silicon nanomembranes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cho, Minkyu; Seo, Jung-Hun; Lee, Jaeseong

2015-05-04

In this paper, we report ultra-thin distributed Bragg reflectors (DBRs) via stacked single-crystal silicon (Si) nanomembranes (NMs). Mesh hole-free single-crystal Si NMs were released from a Si-on-insulator substrate and transferred to quartz and Si substrates. Thermal oxidation was applied to the transferred Si NM to form high-quality SiO{sub 2} and thus a Si/SiO{sub 2} pair with uniform and precisely controlled thicknesses. The Si/SiO{sub 2} layers, as smooth as epitaxial grown layers, minimize scattering loss at the interface and in between the layers. As a result, a reflection of 99.8% at the wavelength range from 1350 nm to 1650 nm can be measuredmore » from a 2.5-pair DBR on a quartz substrate and 3-pair DBR on a Si substrate with thickness of 0.87 μm and 1.14 μm, respectively. The high reflection, ultra-thin DBRs developed here, which can be applied to almost any devices and materials, holds potential for application in high performance optoelectronic devices and photonics applications.« less

Characterization of Zinc Oxide (ZnO) piezoelectric properties for Surface Acoustic Wave (SAW) device

NASA Astrophysics Data System (ADS)

Rosydi Zakaria, Mohd; Johari, Shazlina; Hafiz Ismail, Mohd; Hashim, Uda

2017-11-01

In fabricating Surface Acoustic Wave (SAW) biosensors device, the substrate is one of important factors that affected to performance device. there are many types of piezoelectric substrate in the markets and the cheapest is zinc Oxide substrate. Zinc Oxide (ZnO) with its unique properties can be used as piezoelectric substrate along with SAW devices for detection of DNA in this research. In this project, ZnO thin film is deposited onto silicon oxide substrate using electron beam evaporation (E-beam) and Sol-Gel technique. Different material structure is used to compare the roughness and best piezoelectric substrate of ZnO thin film. Two different structures of ZnO target which are pellet and granular are used for e-beam deposition and one sol-gel liquid were synthesize and compared. Parameter for thickness of ZnO e-beam deposition is fixed to a 0.1kÅ for both materials structure and sol-gel was coat using spin coat technique. After the process is done, samples are annealed at temperature of 500°C for 2 hours. The structural properties of effect of post annealing using different material structure of ZnO are studied using Atomic Force Microscopic (AFM) for surface morphology and X-ray Diffraction (XRD) for phase structure.

Enhanced off-resonance magnetoelectric response in laser annealed PZT thick film grown on magnetostrictive amorphous metal substrate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Palneedi, Haribabu; Functional Ceramics Group, Korea Institute of Materials Science; Maurya, Deepam

2015-07-06

A highly dense, 4 μm-thick Pb(Zr,Ti)O{sub 3} (PZT) film is deposited on amorphous magnetostrictive Metglas foil (FeBSi) by granule spray in vacuum process at room temperature, followed by its localized annealing with a continuous-wave 560 nm ytterbium fiber laser radiation. This longer-wavelength laser radiation is able to anneal the whole of thick PZT film layer without any deteriorative effects, such as chemical reaction and/or atomic diffusion, at the interface and crystallization of amorphous Metglas substrate. Greatly enhanced dielectric and ferroelectric properties of the annealed PZT are attributed to its better crystallinity and grain growth induced by laser irradiation. As a result, amore » colossal off-resonance magnetoelectric (ME) voltage coefficient that is two orders of magnitude larger than previously reported output from PZT/Metglas film-composites is achieved. The present work addresses the problems involved in the fabrication of PZT/Metglas film-composites and opens up emerging possibilities in employing piezoelectric materials with low thermal budget substrates (suitable for integrated electronics) and designing laminate composites for ME based devices.« less

NT-SiC (new-technology silicon carbide) : Φ 650mm optical space mirror substrate of high-strength reaction-sintered silicon carbide

NASA Astrophysics Data System (ADS)

Suyama, Shoko; Itoh, Yoshiyasu; Tsuno, Katsuhiko; Ohno, Kazuhiko

2005-08-01

Silicon carbide (SiC) is the most advantageous as the material of various telescope mirrors, because of high stiffness, low density, low coefficient of thermal expansion, high thermal conductivity and thermal stability. Newly developed high-strength reaction-sintered silicon carbide (NTSIC), which has two times higher strength than sintered SiC, is one of the most promising candidates for lightweight optical mirror substrate, because of fully dense, lightweight, small sintering shrinkage (+/-1 %), good shape capability and low processing temperature. In this study, 650mm in diameter mirror substrate of NTSIC was developed for space telescope applications. Three developed points describe below. The first point was to realize the lightweight to thin the thickness of green bodies. Ribs down to 3mm thickness can be obtained by strengthen the green body. The second point was to enlarge the mirror size. 650mm in diameter of mirror substrate can be fabricated with enlarging the diameter in order. The final point was to realize the homogeneity of mirror substrate. Some properties, such as density, bending strength, coefficient of thermal expansion, Young's modulus, Poisson's ratio, fracture toughness, were measured by the test pieces cutting from the fabricated mirror substrates.

Direct synthesis and characterization of optically transparent conformal zinc oxide nanocrystalline thin films by rapid thermal plasma CVD

NASA Astrophysics Data System (ADS)

Pedersen, Joachim D.; Esposito, Heather J.; Teh, Kwok Siong

2011-10-01

We report a rapid, self-catalyzed, solid precursor-based thermal plasma chemical vapor deposition process for depositing a conformal, nonporous, and optically transparent nanocrystalline ZnO thin film at 130 Torr (0.17 atm). Pure solid zinc is inductively heated and melted, followed by ionization by thermal induction argon/oxygen plasma to produce conformal, nonporous nanocrystalline ZnO films at a growth rate of up to 50 nm/min on amorphous and crystalline substrates including Si (100), fused quartz, glass, muscovite, c- and a-plane sapphire (Al2O3), gold, titanium, and polyimide. X-ray diffraction indicates the grains of as-deposited ZnO to be highly textured, with the fastest growth occurring along the c-axis. The individual grains are observed to be faceted by (103) planes which are the slowest growth planes. ZnO nanocrystalline films of nominal thicknesses of 200 nm are deposited at substrate temperatures of 330°C and 160°C on metal/ceramic substrates and polymer substrates, respectively. In addition, 20-nm- and 200-nm-thick films are also deposited on quartz substrates for optical characterization. At optical spectra above 375 nm, the measured optical transmittance of a 200-nm-thick ZnO film is greater than 80%, while that of a 20-nm-thick film is close to 100%. For a 200-nm-thick ZnO film with an average grain size of 100 nm, a four-point probe measurement shows electrical conductivity of up to 910 S/m. Annealing of 200-nm-thick ZnO films in 300 sccm pure argon at temperatures ranging from 750°C to 950°C (at homologous temperatures between 0.46 and 0.54) alters the textures and morphologies of the thin film. Based on scanning electron microscope images, higher annealing temperatures appear to restructure the ZnO nanocrystalline films to form nanorods of ZnO due to a combination of grain boundary diffusion and bulk diffusion. PACS: films and coatings, 81.15.-z; nanocrystalline materials, 81.07.Bc; II-VI semiconductors, 81.05.Dz.

Photonic devices on planar and curved substrates and methods for fabrication thereof

DOEpatents

Bartl, Michael H.; Barhoum, Moussa; Riassetto, David

2016-08-02

A versatile and rapid sol-gel technique for the fabrication of high quality one-dimensional photonic bandgap materials. For example, silica/titania multi-layer materials may be fabricated by a sol-gel chemistry route combined with dip-coating onto planar or curved substrate. A shock-cooling step immediately following the thin film heat-treatment process is introduced. This step was found important in the prevention of film crack formation--especially in silica/titania alternating stack materials with a high number of layers. The versatility of this sol-gel method is demonstrated by the fabrication of various Bragg stack-type materials with fine-tuned optical properties by tailoring the number and sequence of alternating layers, the film thickness and the effective refractive index of the deposited thin films. Measured optical properties show good agreement with theoretical simulations confirming the high quality of these sol-gel fabricated optical materials.

Seed layer effect on different properties and UV detection capability of hydrothermally grown ZnO nanorods over SiO2/p-Si substrate

NASA Astrophysics Data System (ADS)

Sannakashappanavar, Basavaraj S.; Byrareddy, C. R.; Kumar, Pesala Sudheer; Yadav, Aniruddh Bahadur

2018-05-01

Hydrothermally grown one dimensional ZnO nanostructures are among the most widely used semiconductor materials to build high-efficiency electronic devices for various applications. Few researchers have addressed the growth mechanism and effect of ZnO seed layer on different properties of ZnO nanorods grown by hydrothermal method, instead, no one has synthesized ZnO nanorod over SiO2/p-Si substrate. The aim of this study is to study the effect of ZnO seed layer and the growth mechanism of ZnO nanorods over SiO2/p-Si substrate. To achieve the goal, we have synthesized ZnO nanorods over different thickness ZnO seed layers by using the hydrothermal method on SiO2/p-Si substrate. The effects of c-plane area ratio were identified for the growth rate of c-plane, reaction rate constant and stagnant layer thickness also calculated by using a modified rate growth equation. We have identified maximum seed layer thickness for the growth of vertical ZnO nanorod. A step dislocation in the ZnO nanorods grown on 150and 200 nm thick seed layers was observed, the magnitude of Burges vector was calculated for this disorder. The seed layer and ZnO nanorods were characterized by AFM, XPS, UV-visible, XRD (X-ray diffraction, and SEM(scanning electron microscope). To justify the application of the grown ZnO nanorods Ti/Au was deposited over ZnO nanorods grown over all seed layers for the fabrication of photoconductor type UV detector.

Manufacturing Methods and Technology Engineering (MM&TE) Program for the Establishment of Production Techniques for High Density Thick Film Circuits Used in Crystal Oscillators. Volume I.

DTIC Science & Technology

1980-04-01

incorporate the high reliability ceramic-packaged quartz crystal resonator developed at ERADCOM, and utilize beam -leaded devices wherever possible...the form of a truncated cylinder. The rather complex module outline is best accomplished through the use of a precast potting shell filled with a low...crossover connections are achieved by means of thick-film dielectric material. Chip components attached to the metallized substrate complete the circuits

An Automated System for Accurately Tracking and Measuring Multiple Targets in Six Dimensions

DTIC Science & Technology

2001-08-01

diffracted with good efficiency. The deflection medium is a crystal material TeO2 . The power of the electrical signal is 2W. The corresponding diffraction...between 50 MHz and 100 MHz. The acoustooptical deflector used a birefregent TeO2 single crystal as the ultrasonic medium where the light deflection take...pair of glass substrates with sufficient thickness (> 1 mm). The thick glass plate reduces the spatial resolution of the fiberoptic plate. To reduce

Cracking of coated materials under transient thermal stresses

NASA Technical Reports Server (NTRS)

Rizk, A. A.; Erdogan, Fazil

1988-01-01

The crack problem for a relatively thin layer bonded to a very thick substrate under thermal shock conditions is considered. The effect of surface cooling rate is studied by assuming the temperature boundary condition to be a ramp function. Among the crack geometries considered are the edge crack in the coating layer, the broken layer, the edge crack going through the interface, the undercoat crack in the substrate and the embedded crack crossing the interface. The primary calculated quantity is the stress intensity factor at various singular points and the main variables are the relative sizes and locations of cracks, the time, and the duration of the cooling ramp. The problem is solved and rather extensive results are given for two material pairs, namely a stainless steel layer welded on a ferritic medium and a ceramic coating on a steel substrate.

Cracking of coated materials under transient thermal stresses

NASA Technical Reports Server (NTRS)

Rizk, A. A.; Erdogan, F.

1989-01-01

The crack problem for a relatively thin layer bonded to a very thick substrate under thermal shock conditions is considered. The effect of surface cooling rate is studied by assuming the temperature boundary condition to be a ramp function. Among the crack geometries considered are the edge crack in the coating layer, the broken layer, the edge crack going through the interface, the undercoat crack in the substrate and the embedded crack crossing the interface. The primary calculated quantity is the stress intensity factor at various singular points and the main variables are the relative sizes and locations of cracks, the time, and the duration of the cooling ramp. The problem is solved and rather extensive results are given for two material pairs, namely a stainless steel layer welded on a ferritic medium and a ceramic coating on a steel substrate.

Morphology and topography study of graphene synthesized from plant oil

NASA Astrophysics Data System (ADS)

Robaiah, M.; Rusop, M.; Abdullah, S.; Khusaimi, Z.; Azhan, H.; Laila, M. O.; Salifairus, M. J.; Asli, N. A.

2018-05-01

The graphene is material consists of bonded atom carbon atoms in sheet form one atom thick. The different types of carbon sources which are refined corn oil, palm oil and waste cooking palm oil were used as carbon feedstock to supply carbon atom for synthesizing graphene on the nickel substrate by thermal chemical vapour deposition. The substrate and carbon sources were placed in double zone furnaces. The carbon sources and the substrate were heated at 300 °C and 900 °C respectively. The both furnaces were switched off after synthesis time for cooling process finish. The formation of the graphene on the Ni surface appears due to segregation and precipitation of a high amount of carbon from the source material during the cooling process. FESEM, AFM, UV-VIS Spectroscopy and Raman Spectroscopy were used to characterize and synthesized graphene.

Experimental Investigation of Terminal Fans Prograding on a Salt Substrate: 3-d Physical Experiments

NASA Astrophysics Data System (ADS)

Chatmas, E.; Kim, W.

2015-12-01

Interactions between geologic features and a mobile substrate layer are present in several passive margin locations throughout the world. Deformation of a substrate layer is primarily due to differential loading of sediment and results in complexities within the morphology and subsequently the stratigraphic record. By using simplified scaled tank experiments, we investigated the relationship between substrate deformation and fan evolution in a fluvial-dump-wind-redistribution setting. In this system, sediment is being eroded from a mountain range and creating terminal fans; fluvial channels form off of the fan body and the deposited fluvial sediment is the source for an aeolian dune field. Several past experimental studies have focused on how deltas and dunes are affected on when deposited on a salt substrate, however terminal fans and channel formation off of fans have not been thoroughly investigated. The current experiments focused on which variables are the most significant in controlling fan growth, channel initiation and channel behavior on the salt substrate. Our experimental basin is 120 cm long, 60 cm wide and 30 cm tall. The materials used for a suite of five experiments involved a polymer polydimethylsiloxane (PDMS) as the deformable substrate analog and 100-μm quartz sand. By isolating certain variables such as substrate thickness, basin slope and sediment discharge we are able to see how terminal fans and channels are affected in different settings. The experimental results show that 1) increase in substrate thickness increased the amount of subsidence around the fan body, limiting sediment transport to channels off of the toe of the fan, 2) a higher basin slope increased the number of channels formed and increased sinuosity and width variations of channels over distance, and 3) a higher sediment discharge rate on a thin substrate allowed for the farthest downstream fan deposits. Preliminary results show that channel behavior and fan morphology is strongly dependent on substrate thickness and basin slope directly influences channel geometry. These findings will also be compared to the Mojave River Wash located in southern California off the San Bernardino Mountains near Zzyzx, CA to further understand the dynamics of terminal fans on a mobile substrate.

A modified thickness extensional disk transducer.

PubMed

Trolier, S E; Xu, Q C; Newnham, R E

1988-01-01

Photolithography and chemical etching were investigated as a means of patterning miniature piezoelectric devices. Using a processing procedure analogous to that utilized in the production of integrated circuitry, concentrated hydrochloric acid and a commercially available photoresist were used to fabricate a number of complex structures from soft lead zirconate titanate (PZT) substrates. Among the devices produced in this manner was a modified thickness-mode resonator etched to destroy the simple geometry responsible for radial vibrations. The resultant transducer demonstrated significantly smaller amplitudes for lateral resonances and a marked reduction in the effective planar coupling coefficient over the unaltered disk. The results indicate that photolithographic patterning is useful both for eliminating spurious resonances from transducers for medical imaging or nondestructive evaluation and for engineering low planar coupling coefficients into a variety of substrate materials.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mamun, Md Abdullah A., E-mail: mmamu001@odu.edu; Elmustafa, Abdelmageed A.; Hernandez-Garcia, Carlos

The alkali species Cs and K were codeposited using an effusion source, onto relatively thick layers of Sb (50 nm to ∼7 μm) grown on GaAs and Ta substrates inside a vacuum chamber that was baked and not-vented, and also baked and vented with clean dry nitrogen but not rebaked. The characteristics of the Sb films, including sticking probability, surface roughness, grain size, and crystal properties were very different for these conditions, yet comparable values of photocathode yield [or quantum efficiency (QE)] at 284 V were obtained following codeposition of the alkali materials. Photocathodes manufactured with comparatively thick Sb layers exhibited the highestmore » QE and the best 1/e lifetime. The authors speculate that the alkali codeposition enabled optimized stoichiometry for photocathodes manufactured using thick Sb layers, which could serve as a reservoir for the alkali materials.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mamun, Md Abdullah A.; Elmustafa, Abdelmageed A.; Hernandez-Garcia, Carlos

The alkali species Cs and K were codeposited using an effusion source, onto relatively thick layers of Sb (50 nm to ~7 μm) grown on GaAs and Ta substrates inside a vacuum chamber that was baked and not-vented, and also baked and vented with clean dry nitrogen but not rebaked. The characteristics of the Sb films, including sticking probability, surface roughness, grain size, and crystal properties were very different for these conditions, yet comparable values of photocathode yield [or quantum efficiency (QE)] at 284 V were obtained following codeposition of the alkali materials. Photocathodes manufactured with comparatively thick Sb layersmore » exhibited the highest QE and the best 1/e lifetime. As last, the authors speculate that the alkali codeposition enabled optimized stoichiometry for photocathodes manufactured using thick Sb layers, which could serve as a reservoir for the alkali materials.« less

Electrophoretic Deposition on Porous Non-Conductors

NASA Technical Reports Server (NTRS)

Compson, Charles; Besra, Laxmidhar; Liu, Meilin

2007-01-01

A method of electrophoretic deposition (EPD) on substrates that are porous and electrically non-conductive has been invented. Heretofore, in order to perform an EPD, it has been necessary to either (1) use a substrate material that is inherently electrically conductive or (2) subject a non-conductive substrate to a thermal and/or chemical treatment to render it conductive. In the present method, instead of relying on the electrical conductivity of the substrate, one ensures that the substrate is porous enough that when it is immersed in an EPD bath, the solvent penetrates throughout the thickness, thereby forming quasi-conductive paths through the substrate. By making it unnecessary to use a conductive substrate, this method simplifies the overall EPD process and makes new applications possible. The method is expected to be especially beneficial in enabling deposition of layers of ceramic and/or metal for chemical and electrochemical devices, notably including solid oxide fuel cells.

Vitreous carbon mask substrate for X-ray lithography

DOEpatents

Aigeldinger, Georg [Livermore, CA; Skala, Dawn M [Fremont, CA; Griffiths, Stewart K [Livermore, CA; Talin, Albert Alec [Livermore, CA; Losey, Matthew W [Livermore, CA; Yang, Chu-Yeu Peter [Dublin, CA

2009-10-27

The present invention is directed to the use of vitreous carbon as a substrate material for providing masks for X-ray lithography. The new substrate also enables a small thickness of the mask absorber used to pattern the resist, and this enables improved mask accuracy. An alternative embodiment comprised the use of vitreous carbon as a LIGA substrate wherein the VC wafer blank is etched in a reactive ion plasma after which an X-ray resist is bonded. This surface treatment provides a surface enabling good adhesion of the X-ray photoresist and subsequent nucleation and adhesion of the electrodeposited metal for LIGA mold-making while the VC substrate practically eliminates secondary radiation effects that lead to delamination of the X-ray resist form the substrate, the loss of isolated resist features, and the formation of a resist layer adjacent to the substrate that is insoluble in the developer.

Method for improving the performance of oxidizable ceramic materials in oxidizing environments

NASA Technical Reports Server (NTRS)

Nagaraj, Bangalore A. (Inventor)

2002-01-01

Improved adhesion of thermal barrier coatings to nonmetallic substrates using a dense layer of ceramic on an underlying nonmetallic substrate that includes at least one oxidizable component. The improved adhesion occurs because the application of the dense ceramic layer forms a diffusion barrier for oxygen. This diffusion barrier prevents the oxidizable component of the substrate from decomposing. The present invention applies ceramic by a process that deposits a relatively thick and dense ceramic layer on the underlying substrate. The formation of the dense layer of ceramic avoids the problem of void formation associated with ceramic formation by most prior art thermal decomposition processes. The formation of voids has been associated with premature spalling of thermal barrier layers and other protective layers applied to substrates.

Investigations on effects of the hole size to fix electrodes and interconnection lines in polydimethylsiloxane

NASA Astrophysics Data System (ADS)

Behkami, Saber; Frounchi, Javad; Ghaderi Pakdel, Firouz; Stieglitz, Thomas

2017-11-01

Translational research in bioelectronics medicine and neural implants often relies on established material assemblies made of silicone rubber (polydimethylsiloxane-PDMS) and precious metals. Longevity of the compound is of utmost importance for implantable devices in therapeutic and rehabilitation applications. Therefore, secure mechanical fixation can be used in addition to chemical bonding mechanisms to interlock PDMS substrate and insulation layers with metal sheets for interconnection lines and electrodes. One of the best ways to fix metal lines and electrodes in PDMS is to design holes in electrode rims to allow for direct interconnection between top to bottom layer silicone. Hence, the best layouts and sizes of holes (up to 6) which provide sufficient stability against lateral and vertical forces have been investigated with a variety of numbers of hole in line electrodes, which are simulated and fabricated with different layouts, sizes and materials. Best stability was obtained with radii of 100, 72 and 62 µm, respectively, and a single central hole in aluminum, platinum and MP35N foil line electrodes of 400  ×  500 µm2 size and of thickness 20 µm. The study showed that the best hole size which provides line electrode immobility (of thickness less than 30 µm) within a central hole is proportional to reverse value of Young’s Modulus of the material used. Thus, an array of line electrodes was designed and fabricated to study this effect. Experimental results were compared with simulation data. Subsequently, an approximation curve was generated as design rule to propose the best radius to fix line electrodes according to the material thickness between 10 and 200 µm using PDMS as substrate material.

Preparation and characterization of B4C coatings for advanced research light sources.

PubMed

Störmer, Michael; Siewert, Frank; Sinn, Harald

2016-01-01

X-ray optical elements are required for beam transport at the current and upcoming free-electron lasers and synchrotron sources. An X-ray mirror is a combination of a substrate and a coating. The demand for large mirrors with single layers consisting of light or heavy elements has increased during the last few decades; surface finishing technology is currently able to process mirror lengths up to 1 m with microroughness at the sub-nanometre level. Additionally, thin-film fabrication is able to deposit a suitable single-layer material, such as boron carbide (B4C), some tens of nanometres thick. After deposition, the mirror should provide excellent X-ray optical properties with respect to coating thickness errors, microroughness values and slope errors; thereby enabling the mirror to transport the X-ray beam with high reflectivity, high beam flux and an undistorted wavefront to an experimental station. At the European XFEL, the technical specifications of the future mirrors are extraordinarily challenging. The acceptable shape error of the mirrors is below 2 nm along the whole length of 1 m. At the Helmholtz-Zentrum Geesthacht (HZG), amorphous layers of boron carbide with thicknesses in the range 30-60 nm were fabricated using the HZG sputtering facility, which is able to cover areas up to 1500 mm long by 120 mm wide in one step using rectangular B4C sputtering targets. The available deposition area is suitable for the specified X-ray mirror dimensions of upcoming advanced research light sources such as the European XFEL. The coatings produced were investigated by means of X-ray reflectometry and interference microscopy. The experimental results for the B4C layers are discussed according to thickness uniformity, density, microroughness and thermal stability. The variation of layer thickness in the tangential and sagittal directions was investigated in order to estimate the achieved level of uniformity over the whole deposition area, which is considerably larger than the optical area of a mirror. A waisted mask was positioned during deposition between the sputtering source and substrate to improve the thickness uniformity; particularly to prevent the formation a convex film shape in the sagittal direction. Additionally the inclination of the substrate was varied to change the layer uniformity in order to optimize the position of the mirror quality deposited area during deposition. The level of mirror microroughness was investigated for different substrates before and after deposition of a single layer of B4C. The thermal stability of the B4C layers on the various substrate materials was investigated.

Preparation and characterization of B4C coatings for advanced research light sources

PubMed Central

Störmer, Michael; Siewert, Frank; Sinn, Harald

2016-01-01

X-ray optical elements are required for beam transport at the current and upcoming free-electron lasers and synchrotron sources. An X-ray mirror is a combination of a substrate and a coating. The demand for large mirrors with single layers consisting of light or heavy elements has increased during the last few decades; surface finishing technology is currently able to process mirror lengths up to 1 m with microroughness at the sub-nanometre level. Additionally, thin-film fabrication is able to deposit a suitable single-layer material, such as boron carbide (B4C), some tens of nanometres thick. After deposition, the mirror should provide excellent X-ray optical properties with respect to coating thickness errors, microroughness values and slope errors; thereby enabling the mirror to transport the X-ray beam with high reflectivity, high beam flux and an undistorted wavefront to an experimental station. At the European XFEL, the technical specifications of the future mirrors are extraordinarily challenging. The acceptable shape error of the mirrors is below 2 nm along the whole length of 1 m. At the Helmholtz-Zentrum Geesthacht (HZG), amorphous layers of boron carbide with thicknesses in the range 30–60 nm were fabricated using the HZG sputtering facility, which is able to cover areas up to 1500 mm long by 120 mm wide in one step using rectangular B4C sputtering targets. The available deposition area is suitable for the specified X-ray mirror dimensions of upcoming advanced research light sources such as the European XFEL. The coatings produced were investigated by means of X-ray reflectometry and interference microscopy. The experimental results for the B4C layers are discussed according to thickness uniformity, density, microroughness and thermal stability. The variation of layer thickness in the tangential and sagittal directions was investigated in order to estimate the achieved level of uniformity over the whole deposition area, which is considerably larger than the optical area of a mirror. A waisted mask was positioned during deposition between the sputtering source and substrate to improve the thickness uniformity; particularly to prevent the formation a convex film shape in the sagittal direction. Additionally the inclination of the substrate was varied to change the layer uniformity in order to optimize the position of the mirror quality deposited area during deposition. The level of mirror microroughness was investigated for different substrates before and after deposition of a single layer of B4C. The thermal stability of the B4C layers on the various substrate materials was investigated. PMID:26698045

Investigation of PDMS based bi-layer elasticity via interpretation of apparent Young's modulus.

PubMed

Sarrazin, Baptiste; Brossard, Rémy; Guenoun, Patrick; Malloggi, Florent

2016-02-21

As the need of new methods for the investigation of thin films on various kinds of substrates becomes greater, a novel approach based on AFM nanoindentation is explored. Substrates of polydimethylsiloxane (PDMS) coated by a layer of hard material are probed with an AFM tip in order to obtain the force profile as a function of the indentation. The equivalent elasticity of those composite systems is interpreted using a new numerical approach, the Coated Half-Space Indentation Model of Elastic Response (CHIMER), in order to extract the thicknesses of the upper layer. Two kinds of coating are investigated. First, chitosan films of known thicknesses between 30 and 200 nm were probed in order to test the model. A second type of samples is produced by oxygen plasma oxidation of the PDMS substrate, which results in the growth of a relatively homogeneous oxide layer. The local nature of this protocol enables measurements at long oxidation time, where the apparition of cracks prevents other kinds of measurements.

Method of fabricating germanium and gallium arsenide devices

NASA Technical Reports Server (NTRS)

Jhabvala, Murzban (Inventor)

1990-01-01

A method of semiconductor diode fabrication is disclosed which relies on the epitaxial growth of a precisely doped thickness layer of gallium arsenide or germanium on a semi-insulating or intrinsic substrate, respectively, of gallium arsenide or germanium by either molecular beam epitaxy (MBE) or by metal-organic chemical vapor deposition (MOCVD). The method involves: depositing a layer of doped or undoped silicon dioxide on a germanium or gallium arsenide wafer or substrate, selectively removing the silicon dioxide layer to define one or more surface regions for a device to be fabricated thereon, growing a matched epitaxial layer of doped germanium or gallium arsenide of an appropriate thickness using MBE or MOCVD techniques on both the silicon dioxide layer and the defined one or more regions; and etching the silicon dioxide and the epitaxial material on top of the silicon dioxide to leave a matched epitaxial layer of germanium or gallium arsenide on the germanium or gallium arsenide substrate, respectively, and upon which a field effect device can thereafter be formed.

Composite materials obtained by the ion-plasma sputtering of metal compound coatings on polymer films

NASA Astrophysics Data System (ADS)

Khlebnikov, Nikolai; Polyakov, Evgenii; Borisov, Sergei; Barashev, Nikolai; Biramov, Emir; Maltceva, Anastasia; Vereshchagin, Artem; Khartov, Stas; Voronin, Anton

2016-01-01

In this article, the principle and examples composite materials obtained by deposition of metal compound coatings on polymer film substrates by the ion-plasma sputtering method are presented. A synergistic effect is to obtain the materials with structural properties of the polymer substrate and the surface properties of the metal deposited coatings. The technology of sputtering of TiN coatings of various thicknesses on polyethylene terephthalate films is discussed. The obtained composites are characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), atomic force microscopy (AFM), and scanning tunneling microscopy (STM) is shown. The examples of application of this method, such as receiving nanocomposite track membranes and flexible transparent electrodes, are considered.

Advanced in-situ control for III-nitride RF power device epitaxy

NASA Astrophysics Data System (ADS)

Brunner, F.; Zettler, J.-T.; Weyers, M.

2018-04-01

In this contribution, the latest improvements regarding wafer temperature measurement on 4H-SiC substrates and, based on this, of film thickness and composition control of GaN and AlGaN layers in power electronic device structures are presented. Simultaneous pyrometry at different wavelengths (950 nm and 405 nm) reveal the advantages and limits of the different temperature measurement approaches. Near-UV pyrometry gives a very stable wafer temperature signal without oscillations during GaN growth since the semi-insulating 4H-SiC substrate material becomes opaque at temperatures above 550 °C at the wavelength of 405 nm. A flat wafer temperature profile across the 100 mm substrate diameter is demonstrated despite a convex wafer shape at AlGaN growth conditions. Based on the precise assignment of wafer temperature during MOVPE we were able to improve the accuracy of the high-temperature n-k database for the materials involved. Consequently, the measurement accuracy of all film thicknesses grown under fixed temperature conditions improved. Comparison of in situ and ex situ determined layer thicknessess indicate an unintended etching of the topmost layer during cool-down. The details and limitations of real-time composition analysis for lower Al-content AlGaN barrier layers during transistor device epitaxy are shown.

Controlled growth of vertically aligned carbon nanotubes on metal substrates

NASA Astrophysics Data System (ADS)

Gao, Zhaoli

Carbon nanotube (CNT) is a fascinating material with extraordinary electrical thermal and mechanical properties. Growing vertically aligned CNT (VACNT) arrays on metal substrates is an important step in bringing CNT into practical applications such as thermal interface materials (TIMs) and microelectrodes. However, the growth process is challenging due to the difficulties in preventing catalyst diffusion and controlling catalyst dewetting on metal substrates with physical surface heterogeneity. In this work, the catalyst diffusion mechanism and catalyst dewetting theory were studied for the controlled growth of VACNTs on metal substrates. The diffusion time of the catalyst, the diffusion coefficients for the catalyst in the substrate materials and the number density of catalyst nanoparticles after dewetting are identified as the key parameters, based on which three strategies are developed. Firstly, a fast-heating catalyst pretreatment strategy was used, aiming at preserving the amount of catalyst prior to CNT growth by reducing the catalyst diffusion time. The catalyst lifetime is extended from half an hour to one hour on a patterned Al thin film and a VACNT height of 106 mum, about twenty fold of that reported in the literature, was attained. Secondly, a diffusion barrier layer strategy is employed for a reduction of catalyst diffusion into the substrate materials. Enhancement of VACNT growth on Cu substrates was achieved by adopting a conformal Al2O 3 diffusion barrier layer fabricated by a specially designed atomic layer deposition (ALD) system. Lastly, a novel catalyst glancing angle deposition (GLAD) strategy is performed to manipulate the morphology of a relatively thick catalyst on metal substrates with physical surface heterogeneity, aiming to obtain uniform and dense catalyst nanoparticles after dewetting in the pretreatment process for enhanced VACNT growth. We are able to control the VACNT growth conditions on metal substrates in terms of their distribution, heights and alignments. Catalyst loss is controlled by the catalyst diffusion time and catalyst diffusion coefficients. A shorter catalyst diffusion time and smaller diffusion coefficient enhance VACNT growth on metals due to reduced catalyst loss during the pretreatment process. The dewetting behaviors of the thin film catalysts are influenced by the physical surface heterogeneity of the substrates which leads to non-uniform growth of VACNTs. The GLAD process facilitates the deposition of a relatively thick catalyst layer for the creation of dense and uniform catalyst nanoparticles. Applications of VACNT-metal structures in TIMs and microelectrodes are demonstrated. The VACNT-TIMs fabricated on Al alloy substrates have a typical thermal contact resistivity of 17.1 mm2˙K/W and their effective application in high-brightness LED thermal management was demonstrated. Electrochemical characterization was carried out on VACNT microelectrodes for the development of high resolution retinal prostheses and a satisfactory electrochemical property was again demonstrated.

Some material structural properties of SOI substrates produced by SDB technology

NASA Astrophysics Data System (ADS)

Hui, Li; Guo-Liang, Sun; Juan, Zhan; Qin-Yi, Tong

1987-10-01

SOI substrates have been produced by silicon direct bonding (SDB) technology. Thermal oxides ranging in thickness from native oxide to 1 μm or even more, on either or both wafers have been bonded successfully. The fracture strength of the SOI layer is 130-200 kg/cm 2 which is similar to the value of intrinsic bulk silicon. Dislocations have been shown to be concentrated on the backsides of the substrate and no additional defects have been developed within 80 μm of the Si-SiO 2 bonding area. Mobility and minority carrier lifetime similar to that of the original bulk silicon have been obtained after annealing.

ARPES Studies on the substrate effect on monolayer FeSe

NASA Astrophysics Data System (ADS)

Rebec, Slavko; Jia, Tao; Lee, James; Li, Wei; Zhang, Chaofan; Moore, Robert; Shen, Z. X.

For 2D films, interface interactions can play a critical role in determining the prevailing physics of the system. In the case of FeSe on SrTiO3, reducing the FeSe thickness to 1 monolayer (ML) from bulk leads to a significantly increased superconducting transition temperature (Tc). To fully utilize and maximize this approach to increasing Tc in FeSe and potentially apply it to other superconducting materials, the role which the substrate plays in this system must be understood. Here we present recent in-situ angle-resolved photo emission studies of the substrate effect on MBE grown 1 ML FeSe films.

Structure and mechanical properties of a two-layered material produced by the E-beam surfacing of Ta and Nb on the titanium base after multiple rolling

NASA Astrophysics Data System (ADS)

Bataev, V. A.; Golkovski, M. G.; Samoylenko, V. V.; Ruktuev, A. A.; Polyakov, I. A.; Kuksanov, N. K.

2018-04-01

The study has been conducted in line with the current approach to investigation of materials obtained by considerably deep surface alloying of the titanium substrate with Ta, Nb, and Zr. The thickness of the resulting alloyed layer was equal to 2 mm. The coating was formed through weld deposition of a powder with the use of a high-voltage electron beam in the air. It has been lately demonstrated that manufactured such a way alloyed layers possess corrosion resistance which is significantly higher than the resistance of titanium substrates. It has already been shown that such two-layered materials are weldable. The study objective is to investigate the feasibility of rolling for necking the sheets with the Ti-Ta-Nb anticorrosion coating with further fourfold decrease in their thickness. The research is also aimed at investigation of the material properties after rolling. Anticorrosion layers were formed both on CP-titanium and on VT14 (Ti-4Al-3Mo-1 V) durable titanium alloy. The results of chemical composition determination, structure examination, X-ray phase analysis and mechanical properties observations (including bending properties of the alloyed layers) are presented in the paper. The combination of welding, rolling, and bending enables the manufacture of corrosion-resistant vessels and process pipes which are made from the developed material and find technological application.

Life prediction and constitutive models for engine hot section anisotropic materials

NASA Technical Reports Server (NTRS)

Swanson, G. A.

1984-01-01

The development of directionally solidified and single crystal alloys is perhaps the most important recent advancement in hot section materials technology. The objective is to develop knowledge that enables the designer to improve anisotropic gas turbine parts to their full potential. Two single crystal alloys selected were PWA 1480 and Alloy 185. The coatings selected were an overlay coating, PWA 286, and an aluminide diffusion coating, PWA 273. The constitutive specimens were solid and cylindrical; the fatigue specimens were hollow and cylindrical. Two thicknesses of substrate are utilized. Specimens of both thickness (0.4 and 1.5 mm) will be coated and then tested for tensile, creep, and fatigue properties.

Control of Alq3 wetting layer thickness via substrate surface functionalization.

PubMed

Tsoi, Shufen; Szeto, Bryan; Fleischauer, Michael D; Veinot, Jonathan G C; Brett, Michael J

2007-06-05

The effects of substrate surface energy and vapor deposition rate on the initial growth of porous columnar tris(8-hydroxyquinoline)aluminum (Alq3) nanostructures were investigated. Alq3 nanostructures thermally evaporated onto as-supplied Si substrates bearing an oxide were observed to form a solid wetting layer, likely caused by an interfacial energy mismatch between the substrate and Alq3. Wetting layer thickness control is important for potential optoelectronic applications. A dramatic decrease in wetting layer thickness was achieved by depositing Alq3 onto alkyltrichlorosilane-derivatized Si/oxide substrates. Similar effects were noted with increasing deposition rates. These two effects enable tailoring of the wetting layer thickness.

Process development and monitoring in stripping of a highly transparent polymeric paint with ns-pulsed fiber laser

NASA Astrophysics Data System (ADS)

Jasim, Halah A.; Demir, Ali Gökhan; Previtali, Barbara; Taha, Ziad A.

2017-08-01

Laser paint removal was studied with ns-pulsed fiber laser on the combination of 20 μm-thick, white polymeric paint and Al alloy substrate. The response of paint to single pulse ablation was evaluated to measure the ablated zone dimensions. With this information, the effect of overlap, number of passes and pulse repetition rate was evaluated to investigate machining depth. Optical emission spectroscopy was used to investigate the machining behaviour as well as to propose monitoring strategies. The results showed that despite the high transparency of the paint, complete paint removal can be achieved with reduced substrate damage (Sa = 1.3 μm). The emission spectroscopy can be used to identify removal completion as well as the reach of substrate material. The observations were also used to explain a paint removal mechanism based on thermal expansion of the paint and mechanical action provided by the plasma expansion from the substrate material.

Photosensitive adhesive bonding process of magnetooptic waveguides with Si guiding layer for optical nonreciprocal devices

NASA Astrophysics Data System (ADS)

Choowitsakunlert, Salinee; Takagiwa, Kenji; Kobashigawa, Takuya; Hosoya, Nariaki; Silapunt, Rardchawadee; Yokoi, Hideki

2018-05-01

A photosensitive adhesive bonding process for a magnetooptic waveguide for an optical isolator employing a nonreciprocal guided-radiation mode conversion is investigated at 1.55 µm. The magnetooptic waveguide is a straight rib type, and it is fabricated by bonding the Si guiding layer to a magnetic garnet. In the fabrication process, an adhesive material is diluted to obtain a certain thickness before depositing on a silicon-on-insulator (SOI) substrate. The relationship between the percent dilution ratio and the thickness of the adhesive layer is considered. The smallest gap thickness is found to be 0.66 µm at a dilution ratio of 2%.

High Tc screen-printed YBa2Cu3O(7-x) films - Effect of the substrate material

NASA Astrophysics Data System (ADS)

Bansal, Narottam P.; Simons, Rainee N.; Farrell, D. E.

1988-08-01

Thick films of YBa2Cu3O(7-x) have been deposited on highly polished alumina, magnesia spinel, nickel aluminum titanate (Ni-Al-Ti), and barium tetratitanate (Ba-Ti) substrates by the screen printing technique. Properties of the films were found to be highly sensitive to the choice of the substrate material. The film on Ba-Ti turned green after firing, due to a reaction with the substrate and were insulating. A film on Ni-Al-Ti had a Tc (onset) of about 95 K and lost 90 percent of its resistance by about 75 K. However, even at 4 K it was not fully superconducting, possibly due to a reaction between the film and the substrate and interdiffusion of the reaction products. The film on alumina had Tc (onset) of about 96 K, Tc (zero) of about 66 K, and Delta Tc of about 10 K. The best film was obtained on spinel and had Tc (onset) of about 94 K, zero resistance at 81 K, and a transition width of about 7 K.

High Tc screen-printed YBa2Cu3O(7-x) films - Effect of the substrate material

NASA Technical Reports Server (NTRS)

Bansal, Narottam P.; Simons, Rainee N.; Farrell, D. E.

1988-01-01

Thick films of YBa2Cu3O(7-x) have been deposited on highly polished alumina, magnesia spinel, nickel aluminum titanate (Ni-Al-Ti), and barium tetratitanate (Ba-Ti) substrates by the screen printing technique. Properties of the films were found to be highly sensitive to the choice of the substrate material. The film on Ba-Ti turned green after firing, due to a reaction with the substrate and were insulating. A film on Ni-Al-Ti had a Tc (onset) of about 95 K and lost 90 percent of its resistance by about 75 K. However, even at 4 K it was not fully superconducting, possibly due to a reaction between the film and the substrate and interdiffusion of the reaction products. The film on alumina had Tc (onset) of about 96 K, Tc (zero) of about 66 K, and Delta Tc of about 10 K. The best film was obtained on spinel and had Tc (onset) of about 94 K, zero resistance at 81 K, and a transition width of about 7 K.

Increasing the critical thickness of InGaAs quantum wells using strain-relief technologies

NASA Astrophysics Data System (ADS)

Jones, Andrew Marquis

The advantages of optical communication through silica fiber have made long-distance electrical communication through copper wire obsolete. The two windows of operation for long-haul optical communication are centered around the wavelengths of 1.3 mum and 1.55 mum, which have minimal amounts of signal attenuation and dispersion. Benefits of optical communications within these windows include low system costs, high bandwidth, and high system reliability which have encouraged the development of emitters and receivers at these relatively long wavelengths. Long-wavelength semiconductor lasers are typically fabricated on InP substrates, but their performance suffers greatly with increases in operating temperature. Laser diodes on GaAs substrates are not as sensitive to operating temperature due to quantum-well active regions with relative deep potential barriers, but critical thickness limits the wavelength ceiling to 1.1 mum. Strain-relief technologies are currently being investigated to enable long-wavelength lasers with deeper potential wells leading to a corresponding increase in characteristic temperatures. Having a larger lattice constant than GaAs enables ternary InGaAs substrates to increase the 1.1-mum wavelength ceiling. Extending this ceiling to one of the optical communication windows could enable high-characteristic-temperature, long-wavelength lasers. Broad-area and buried-heterostructure lasers have demonstrated the potential of ternary substrates to increase characteristic temperatures and emission wavelengths. Wavelengths as long as 1.15 mum and characteristic temperatures as high as 145 K have been achieved. Reduced-area metalorganic chemical vapor deposition involves the deposition of strained materials on isolated islands. Due to the discontinuous nature of reduced-area epitaxy, strained materials are allowed to expand near the mesa edges, decreasing the overall strain in the structure. Laser diodes using this technology have been successfully fabricated, and evidence for partial relief of strain energy has been obtained. Compliant membranes enable strain relief by depositing on an ultra-thin semiconductor base. Unlike growth on typical thick substrates, expansion of the compliant membrane during strained-layer regrowth allows the membrane to accommodate most of the strain energy. Ternary InGaAs compliant films supported above a GaAs substrate with single AlGaAs pedestals have been utilized to fabricate long-wavelength (1.35 mum) InGaAs quantum wells on a GaAs substrate.

Colloidal CuInSe2 nanocrystals thin films of low surface roughness

NASA Astrophysics Data System (ADS)

de Kergommeaux, Antoine; Fiore, Angela; Faure-Vincent, Jérôme; Pron, Adam; Reiss, Peter

2013-03-01

Thin-film processing of colloidal semiconductor nanocrystals (NCs) is a prerequisite for their use in (opto-)electronic devices. The commonly used spin-coating is highly materials consuming as the overwhelming amount of deposited matter is ejected from the substrate during the spinning process. Also, the well-known dip-coating and drop-casting procedures present disadvantages in terms of the surface roughness and control of the film thickness. We show that the doctor blade technique is an efficient method for preparing nanocrystal films of controlled thickness and low surface roughness. In particular, by optimizing the deposition conditions, smooth and pinhole-free films of 11 nm CuInSe2 NCs have been obtained exhibiting a surface roughness of 13 nm root mean square (rms) for a 350 nm thick film, and less than 4 nm rms for a 75 nm thick film. Invited talk at the 6th International Workshop on Advanced Materials Science and Nanotechnology, 30 October-2 November 2012, Ha Long, Vietnam.

Coatings for FEL optics: preparation and characterization of B4C and Pt

PubMed Central

Störmer, Michael; Siewert, Frank; Horstmann, Christian; Buchheim, Jana; Gwalt, Grzegorz

2018-01-01

Large X-ray mirrors are required for beam transport at both present-day and future free-electron lasers (FELs) and synchrotron sources worldwide. The demand for large mirrors with lengths up to 1 m single layers consisting of light or heavy elements has increased during the last few decades. Accordingly, surface finishing technology is now able to produce large substrate lengths with micro-roughness on the sub-nanometer scale. At the Helmholtz-Zentrum Geesthacht (HZG), a 4.5 m-long sputtering facility enables us to deposit a desired single-layer material some tens of nanometers thick. For the European XFEL project, the shape error should be less than 2 nm over the whole 1 m X-ray mirror length to ensure the safe and efficient delivery of X-ray beams to the scientific instruments. The challenge is to achieve thin-film deposition on silicon substrates, benders and gratings without any change in mirror shape. Thin films of boron carbide and platinum with a thickness in the range 30–100 nm were manufactured using the HZG sputtering facility. This setup is able to cover areas of up to 1500 mm × 120 mm in one step using rectangular sputtering sources. The coatings produced were characterized using various thin-film methods. It was possible to improve the coating process to achieve a very high uniformity of the layer thickness. The movement of the substrate in front of the sputtering source has been optimized. A variation in B4C layer thickness below 1 nm (peak-to-valley) was achieved at a mean thickness of 51.8 nm over a deposition length of 1.5 m. In the case of Pt, reflectometry and micro-roughness measurements were performed. The uniformity in layer thickness was about 1 nm (peak-to-valley). The micro-roughness of the Pt layers showed no significant change in the coated state for layer thicknesses of 32 nm and 102 nm compared with the uncoated substrate state. The experimental results achieved will be discussed with regard to current restrictions and future developments. PMID:29271760

Coatings for FEL optics: preparation and characterization of B4C and Pt.

PubMed

Störmer, Michael; Siewert, Frank; Horstmann, Christian; Buchheim, Jana; Gwalt, Grzegorz

2018-01-01

Large X-ray mirrors are required for beam transport at both present-day and future free-electron lasers (FELs) and synchrotron sources worldwide. The demand for large mirrors with lengths up to 1 m single layers consisting of light or heavy elements has increased during the last few decades. Accordingly, surface finishing technology is now able to produce large substrate lengths with micro-roughness on the sub-nanometer scale. At the Helmholtz-Zentrum Geesthacht (HZG), a 4.5 m-long sputtering facility enables us to deposit a desired single-layer material some tens of nanometers thick. For the European XFEL project, the shape error should be less than 2 nm over the whole 1 m X-ray mirror length to ensure the safe and efficient delivery of X-ray beams to the scientific instruments. The challenge is to achieve thin-film deposition on silicon substrates, benders and gratings without any change in mirror shape. Thin films of boron carbide and platinum with a thickness in the range 30-100 nm were manufactured using the HZG sputtering facility. This setup is able to cover areas of up to 1500 mm × 120 mm in one step using rectangular sputtering sources. The coatings produced were characterized using various thin-film methods. It was possible to improve the coating process to achieve a very high uniformity of the layer thickness. The movement of the substrate in front of the sputtering source has been optimized. A variation in B 4 C layer thickness below 1 nm (peak-to-valley) was achieved at a mean thickness of 51.8 nm over a deposition length of 1.5 m. In the case of Pt, reflectometry and micro-roughness measurements were performed. The uniformity in layer thickness was about 1 nm (peak-to-valley). The micro-roughness of the Pt layers showed no significant change in the coated state for layer thicknesses of 32 nm and 102 nm compared with the uncoated substrate state. The experimental results achieved will be discussed with regard to current restrictions and future developments.

Genesis Contingency Planning and Mishap Recovery: The Sample Curation View

NASA Technical Reports Server (NTRS)

Stansbery, E. K.; Allton, J. H.; Allen, C. C.; McNamara, K. M.; Calaway, M.; Rodriques, M. C.

2007-01-01

Planning for sample preservation and curation was part of mission design from the beginning. One of the scientific objectives for Genesis included collecting samples of three regimes of the solar wind in addition to collecting bulk solar wind during the mission. Collectors were fabricated in different thicknesses for each regime of the solar wind and attached to separate frames exposed to the solar wind during specific periods of solar activity associated with each regime. The original plan to determine the solar regime sampled for specific collectors was to identify to which frame the collector was attached. However, the collectors were dislodged during the hard landing making identification by frame attachment impossible. Because regimes were also identified by thickness of the collector, the regime sampled is identified by measuring fragment thickness. A variety of collector materials and thin films applied to substrates were selected and qualified for flight. This diversity provided elemental measurement in more than one material, mitigating effects of diffusion rates and/or radiation damage. It also mitigated against different material and substrate strengths resulting in differing effects of the hard landing. For example, silicon crystal substrates broke into smaller fragments than sapphire-based substrates and diamond surfaces were more resilient to flying debris damage than gold. The primary responsibility of the curation team for recovery was process documentation. Contingency planning for the recovery phase expanded this responsibility to include not only equipment to document, but also gather, contain and identify samples from the landing area and the recovered spacecraft. The team developed contingency plans for various scenarios as part of mission planning that included topographic maps to aid in site recovery and identification of different modes of transport and purge capability depending on damage. A clean tent, set-up at Utah Test & Training Range to control the environment for processing the sample return capsule and cleanly installing a nitrogen purge to the canister, was used to control the environment for extracting collector fragments from the damaged canister and to document and package over 10,000 collector fragments.

Method for depositing high-quality microcrystalline semiconductor materials

DOEpatents

Guha, Subhendu [Bloomfield Hills, MI; Yang, Chi C [Troy, MI; Yan, Baojie [Rochester Hills, MI

2011-03-08

A process for the plasma deposition of a layer of a microcrystalline semiconductor material is carried out by energizing a process gas which includes a precursor of the semiconductor material and a diluent with electromagnetic energy so as to create a plasma therefrom. The plasma deposits a layer of the microcrystalline semiconductor material onto the substrate. The concentration of the diluent in the process gas is varied as a function of the thickness of the layer of microcrystalline semiconductor material which has been deposited. Also disclosed is the use of the process for the preparation of an N-I-P type photovoltaic device.

Tribology of bio-inspired nanowrinkled films on ultrasoft substrates.

PubMed

Lackner, Juergen M; Waldhauser, Wolfgang; Major, Lukasz; Teichert, Christian; Hartmann, Paul

2013-01-01

Biomimetic design of new materials uses nature as antetype, learning from billions of years of evolution. This work emphasizes the mechanical and tribological properties of skin, combining both hardness and wear resistance of its surface (the stratum corneum) with high elasticity of the bulk (epidermis, dermis, hypodermis). The key for combination of such opposite properties is wrinkling, being consequence of intrinsic stresses in the bulk (soft tissue): Tribological contact to counterparts below the stress threshold for tissue trauma occurs on the thick hard stratum corneum layer pads, while tensile loads smooth out wrinkles in between these pads. Similar mechanism offers high tribological resistance to hard films on soft, flexible polymers, which is shown for diamond-like carbon (DLC) and titanium nitride thin films on ultrasoft polyurethane and harder polycarbonate substrates. The choice of these two compared substrate materials will show that ultra-soft substrate materials are decisive for the distinct tribological material. Hierarchical wrinkled structures of films on these substrates are due to high intrinsic compressive stress, which evolves during high energetic film growth. Incremental relaxation of these stresses occurs by compound deformation of film and elastic substrate surface, appearing in hierarchical nano-wrinkles. Nano-wrinkled topographies enable high elastic deformability of thin hard films, while overstressing results in zigzag film fracture along larger hierarchical wrinkle structures. Tribologically, these fracture mechanisms are highly important for ploughing and sliding of sharp and flat counterparts on hard-coated ultra-soft substrates like polyurethane. Concentration of polyurethane deformation under the applied normal loads occurs below these zigzag cracks. Unloading closes these cracks again. Even cyclic testing do not lead to film delamination and retain low friction behavior, if the adhesion to the substrate is high and the initial friction coefficient of the film against the sliding counterpart low, e.g. found for DLC.

Tribology of bio-inspired nanowrinkled films on ultrasoft substrates

PubMed Central

Lackner, Juergen M.; Waldhauser, Wolfgang; Major, Lukasz; Teichert, Christian; Hartmann, Paul

2013-01-01

Biomimetic design of new materials uses nature as antetype, learning from billions of years of evolution. This work emphasizes the mechanical and tribological properties of skin, combining both hardness and wear resistance of its surface (the stratum corneum) with high elasticity of the bulk (epidermis, dermis, hypodermis). The key for combination of such opposite properties is wrinkling, being consequence of intrinsic stresses in the bulk (soft tissue): Tribological contact to counterparts below the stress threshold for tissue trauma occurs on the thick hard stratum corneum layer pads, while tensile loads smooth out wrinkles in between these pads. Similar mechanism offers high tribological resistance to hard films on soft, flexible polymers, which is shown for diamond-like carbon (DLC) and titanium nitride thin films on ultrasoft polyurethane and harder polycarbonate substrates. The choice of these two compared substrate materials will show that ultra-soft substrate materials are decisive for the distinct tribological material. Hierarchical wrinkled structures of films on these substrates are due to high intrinsic compressive stress, which evolves during high energetic film growth. Incremental relaxation of these stresses occurs by compound deformation of film and elastic substrate surface, appearing in hierarchical nano-wrinkles. Nano-wrinkled topographies enable high elastic deformability of thin hard films, while overstressing results in zigzag film fracture along larger hierarchical wrinkle structures. Tribologically, these fracture mechanisms are highly important for ploughing and sliding of sharp and flat counterparts on hard-coated ultra-soft substrates like polyurethane. Concentration of polyurethane deformation under the applied normal loads occurs below these zigzag cracks. Unloading closes these cracks again. Even cyclic testing do not lead to film delamination and retain low friction behavior, if the adhesion to the substrate is high and the initial friction coefficient of the film against the sliding counterpart low, e.g. found for DLC. PMID:24688710

Effect of substrate baking temperature on zinc sulfide and germanium thin films optical parameters

NASA Astrophysics Data System (ADS)

Liu, Fang; Gao, Jiaobo; Yang, Chongmin; Zhang, Jianfu; Liu, Yongqiang; Liu, Qinglong; Wang, Songlin; Mi, Gaoyuan; Wang, Huina

2016-10-01

ZnS and Ge are very normal optical thin film materials in Infrared wave. Studying the influence of different substrate baking temperature to refractive index and actual deposition rates is very important to promote optical thin film quality. In the same vacuum level, monitoring thickness and evaporation rate, we use hot evaporation to deposit ZnS thin film materials and use ion-assisted electron beam to deposit Ge thin film materials with different baking temperature. We measure the spectral transmittance with the spectrophotometer and calculate the actual deposition rates and the refractive index in different temperature. With the higher and higher temperature in a particular range, ZnS and Ge refractive index become higher and actual deposition rates become smaller. The refractive index of Ge film material change with baking temperature is more sensitive than ZnS. However, ZnS film actual deposition rates change with baking temperature is more sensitive than Ge.

Monolithic Silicon Microbolometer Materials for Uncooled Infrared Detectors

DTIC Science & Technology

2015-05-21

covered by an active sensing material, and G is the thermal conductance of the supporting legs. Another important figure of merit is the noise...have a low thermal conductance to maximize thermal isolation from the environment. The legs also have a thin film of metal which serve as...fabricated array, glass substrates (≈ 2 mm thick) were used due to their low thermal conductivity and therefore a lower ability to transport heat away

Effects of the type and thickness of ceramic, substrate, and cement on the optical color of a lithium disilicate ceramic.

PubMed

Pires, Laís A; Novais, Pollyanna M R; Araújo, Vinícius D; Pegoraro, Luiz F

2017-01-01

Reproducing the characteristics of natural teeth in ceramic crowns remains a complex and difficult process. The purpose of this in vitro study was to evaluate the effect of the substrate, cement, type, and thickness of the ceramic on the resulting color of a lithium disilicate ceramic. Forty ceramic disks were prepared from IPS e.max Press LT (low translucency) and HO (high opacity) in 2 different thicknesses (1.5 and 2 mm). The LT groups were composed of monolithic ceramic disks, and the HO groups were composed of disks fabricated with a 0.5-mm thickness combined with a 1- or 1.5-mm veneering ceramic thickness. Disks made of composite resin (R) and alloy (A) were used as substrate structures. The resin cement used was Variolink II. Color was measured with a spectrophotometer and expressed in CIELAB coordinates. Color differences (ΔE) were calculated. The data were analyzed with ANOVA and the Tukey HSD test (α=.05). When the ΔE of ceramic disks with both substrates, with and without cement, were compared, the lowest value (3) was obtained for ceramic HO with a 2-mm thickness/alloy substrate/without cement; the highest value (10) was obtained for ceramic LT with a1.5-mm thickness/alloy substrate/with cement. This difference was statistically significant. When the effect of cement on the ΔE of ceramics in both substrates was compared, the lowest value (1.1) occurred with ceramic HO with a 1.5-mm thickness/resin substrate, and the highest was observed for ceramic LT with a 1.5-mm thickness/alloy substrate (6.4). This difference was statistically significant. The substrate color, type and thickness of ceramic, and presence of the cement significantly influenced the resulting optical color. The ΔE values of cemented HO ceramics were lower than that of the LT ceramic. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Uniformly coated highly porous graphene/MnO2 foams for flexible asymmetric supercapacitors

NASA Astrophysics Data System (ADS)

Drieschner, Simon; von Seckendorff, Maximilian; del Corro, Elena; Wohlketzetter, Jörg; Blaschke, Benno M.; Stutzmann, Martin; Garrido, Jose A.

2018-06-01

Supercapacitors are called to play a prominent role in the newly emerging markets of electric vehicles, flexible displays and sensors, and wearable electronics. In order to compete with current battery technology, supercapacitors have to be designed with highly conductive current collectors exhibiting high surface area per unit volume and uniformly coated with pseudocapacitive materials, which is crucial to boost the energy density while maintaining a high power density. Here, we present a versatile technique to prepare thickness-controlled thin-film micro graphene foams (μGFs) with pores in the lower micrometer range grown by chemical vapor deposition which can be used as highly conductive current collectors in flexible supercapacitors. To fabricate the μGF, we use porous metallic catalytic substrates consisting of nickel/copper alloy synthesized on nickel foil by electrodeposition in an electrolytic solution. Changing the duration of the electrodeposition allows the control of the thickness of the metal foam, and thus of the μGF, ranging from a few micrometers to the millimeter scale. The resulting μGF with a thickness and pores in the micrometer regime exhibits high structural quality which leads to a very low intrinsic resistance of the devices. Transferred onto flexible substrates, we demonstrate a uniform coating of the μGFs with manganese oxide, a pseudocapacitively active material. Considering the porous structure and the thickness of the μGFs, square wave potential pulses are used to ensure uniform coverage by the oxide material boosting the volumetric and areal capacitance to 14 F cm‑3 and 0.16 F cm‑2. The μGF with a thickness and pores in the micrometer regime in combination with a coating technique tuned to the porosity of the μGF is of great relevance for the development of supercapacitors based on state-of-the-art graphene foams.

Uniformly coated highly porous graphene/MnO2 foams for flexible asymmetric supercapacitors.

PubMed

Drieschner, Simon; Seckendorff, Maximilian von; Corro, Elena Del; Wohlketzetter, Jörg; Blaschke, Benno M; Stutzmann, Martin; Garrido, Jose A

2018-06-01

Supercapacitors are called to play a prominent role in the newly emerging markets of electric vehicles, flexible displays and sensors, and wearable electronics. In order to compete with current battery technology, supercapacitors have to be designed with highly conductive current collectors exhibiting high surface area per unit volume and uniformly coated with pseudocapacitive materials, which is crucial to boost the energy density while maintaining a high power density. Here, we present a versatile technique to prepare thickness-controlled thin-film micro graphene foams (μGFs) with pores in the lower micrometer range grown by chemical vapor deposition which can be used as highly conductive current collectors in flexible supercapacitors. To fabricate the μGF, we use porous metallic catalytic substrates consisting of nickel/copper alloy synthesized on nickel foil by electrodeposition in an electrolytic solution. Changing the duration of the electrodeposition allows the control of the thickness of the metal foam, and thus of the μGF, ranging from a few micrometers to the millimeter scale. The resulting μGF with a thickness and pores in the micrometer regime exhibits high structural quality which leads to a very low intrinsic resistance of the devices. Transferred onto flexible substrates, we demonstrate a uniform coating of the μGFs with manganese oxide, a pseudocapacitively active material. Considering the porous structure and the thickness of the μGFs, square wave potential pulses are used to ensure uniform coverage by the oxide material boosting the volumetric and areal capacitance to 14 F cm -3 and 0.16 F cm -2 . The μGF with a thickness and pores in the micrometer regime in combination with a coating technique tuned to the porosity of the μGF is of great relevance for the development of supercapacitors based on state-of-the-art graphene foams.

Optical characterization of nanoporous AAO sensor substrate

NASA Astrophysics Data System (ADS)

Kassu, Aschalew; Farley, Carlton W.; Sharma, Anup

2014-05-01

Nanoporous anodic aluminum oxide (AAO) has been investigated as an ideal and cost-effective chemical and biosensing platform. In this paper, we report the optical properties of periodic 100 micron thick nanoporous anodic alumina membranes with uniform and high density cylindrical pores penetrating the entire thickness of the substrate, ranging in size from 18 nm to 150 nm in diameter and pore periods from 44 nm to 243 nm. The surface geometry of the top and bottom surface of each membrane is studied using atomic force microscopy. The optical properties including transmittance, reflectance, and absorbance spectra on both sides of each substrate are studied and found to be symmetrical. It is observed that, as the pore size increases, the peak resonance intensity in transmittance decreases and in absorbance increases. The effects of the pore sizes on the optical properties of the bare nanoporous membranes and the benefit of using arrays of nanohole arrays with varying hole size and periodicity as a chemical sensing platform is also discussed. To characterize the optical sensing technique, transmittance and reflectance measurements of various concentrations of a standard chemical adsorbed on the bare nanoporous substrates are investigated. The preliminary results presented here show variation in transmittance and reflectance spectra with the concentration of the chemical used or the amount of the material adsorbed on the surface of the substrate.

Nickel-Aluminum Layered Double Hydroxide Coating on the Surface of Conductive Substrates by Liquid Phase Deposition.

PubMed

Maki, Hideshi; Takigawa, Masashi; Mizuhata, Minoru

2015-08-12

The direct synthesis of the adhered Ni-Al LDH thin film onto the surface of electrically conductive substrates by the liquid phase deposition (LPD) reaction is carried out for the development of the positive electrode. The complexation and solution equilibria of the dissolved species in the LPD reaction have been clarified by a theoretical approach, and the LPD reaction conditions for the Ni-Al LDH depositions are shown to be optimized by controlling the fluoride ion concentration and the pH of the LPD reaction solutions. The yields of metal oxides and hydroxides by the LPD method are very sensitive to the supersaturation state of the hydroxide in the reaction solution. The surfaces of conductive substrates are completely covered by the minute mesh-like Ni-Al LDH thin film; furthermore, there is no gap between the surfaces of conductive substrates and the deposited Ni-Al LDH thin film. The active material layer thickness was able to be controlled within the range from 100 nm to 1 μm by the LPD reaction time. The high-crystallinity and the arbitrary-thickness thin films on the conductive substrate surface will be beneficial for the interface control of charge transfer reaction fields and the internal resistance reduction of various secondary batteries.

Magnetic anisotropy modulation of epitaxial Fe3O4 films on MgO substrates

NASA Astrophysics Data System (ADS)

Chichvarina, O.; Herng, T. S.; Xiao, W.; Hong, X.; Ding, J.

2015-05-01

Fe3O4 has been widely studied because of its great potential in spintronics and other applications. As a magnetic electrode, it is highly desired if magnetic anisotropy can be controlled. Here, we report the results from our systematic study on the magnetic properties of magnetite (Fe3O4) thin films epitaxially grown on various MgO substrates. Strikingly, we observed a prominent perpendicular magnetic anisotropy in Fe3O4 film deposited on MgO (111) substrate. When measured in out-of-plane direction, the film (40 nm thick) exhibits a well-defined square hysteresis loop with coercivity (Hc) above 1 kOe, while much lower coercivity was obtained in the in-plane orientation. In sharp contrast, the films deposited onto MgO (100) and MgO (110) substrates show in-plane magnetic anisotropy. These films exhibit a typical soft magnet characteristic—Hc lies within the range of 200-400 Oe. All the films showed a clear Verwey transition near 120 K—a characteristic of Fe3O4 material. In addition, a series of magnetoresistance (MR) measurements is performed and the MR results are in good agreement with the magnetic observations. The role of the substrate orientation and film thickness dependency is also investigated.

Enhanced light extraction from organic light-emitting devices using a sub-anode grid (Presentation Recording)

NASA Astrophysics Data System (ADS)

Qu, Yue; Slootsky, Michael; Forrest, Stephen

2015-10-01

We demonstrate a method for extracting waveguided light trapped in the organic and indium tin oxide layers of bottom emission organic light emitting devices (OLEDs) using a patterned planar grid layer (sub-anode grid) between the anode and the substrate. The scattering layer consists of two transparent materials with different refractive indices on a period sufficiently large to avoid diffraction and other unwanted wavelength-dependent effects. The position of the sub-anode grid outside of the OLED active region allows complete freedom in varying its dimensions and materials from which it is made without impacting the electrical characteristics of the device itself. Full wave electromagnetic simulation is used to study the efficiency dependence on refractive indices and geometric parameters of the grid. We show the fabrication process and characterization of OLEDs with two different grids: a buried sub-anode grid consisting of two dielectric materials, and an air sub-anode grid consisting of a dielectric material and gridline voids. Using a sub-anode grid, substrate plus air modes quantum efficiency of an OLED is enhanced from (33+/-2)% to (40+/-2)%, resulting in an increase in external quantum efficiency from (14+/-1)% to (18+/-1)%, with identical electrical characteristics to that of a conventional device. By varying the thickness of the electron transport layer (ETL) of sub-anode grid OLEDs, we find that all power launched into the waveguide modes is scattered into substrate. We also demonstrate a sub-anode grid combined with a thick ETL significantly reduces surface plasmon polaritons, and results in an increase in substrate plus air modes by a >50% compared with a conventional OLED. The wavelength, viewing angle and molecular orientational independence provided by this approach make this an attractive and general solution to the problem of extracting waveguided light and reducing plasmon losses in OLEDs.

Low-cost laser diode array

DOEpatents

Freitas, B.L.; Skidmore, J.A.

1999-06-01

A substrate is used to fabricate a low-cost laser diode array. A substrate is machined from an electrically insulative material that is thermally conductive, or two substrates can be bonded together in which the top substrate is electrically as well as thermally conductive. The substrate thickness is slightly longer than the cavity length, and the width of the groove is wide enough to contain a bar and spring (which secures the laser bar firmly along one face of the groove). The spring also provides electrical continuity from the backside of the bar to the adjacent metalization layer on the laser bar substrate. Arrays containing one or more bars can be formed by creating many grooves at various spacings. Along the groove, many bars can be adjoined at the edges to provide parallel electrical conduction. This architecture allows precise and predictable registration of an array of laser bars to a self-aligned microlens array at low cost. 19 figs.

Low-cost laser diode array

DOEpatents

Freitas, Barry L.; Skidmore, Jay A.

1999-01-01

A substrate is used to fabricate a low-cost laser diode array. A substrate is machined from an electrically insulative material that is thermally conductive, or two substrates can be bonded together in which the top substrate is electrically as well as thermally conductive. The substrate thickness is slightly longer than the cavity length, and the width of the groove is wide enough to contain a bar and spring (which secures the laser bar firmly along one face of the groove). The spring also provides electrical continuity from the backside of the bar to the adjacent metalization layer on the laser bar substrate. Arrays containing one or more bars can be formed by creating many grooves at various spacings. Along the groove, many bars can be adjoined at the edges to provide parallel electrical conduction. This architecture allows precise and predictable registration of an array of laser bars to a self-aligned microlens array at low cost.

Fabrication of solid oxide fuel cell by electrochemical vapor deposition

DOEpatents

Brian, Riley; Szreders, Bernard E.

1989-01-01

In a high temperature solid oxide fuel cell (SOFC), the deposition of an impervious high density thin layer of electrically conductive interconnector material, such as magnesium doped lanthanum chromite, and of an electrolyte material, such as yttria stabilized zirconia, onto a porous support/air electrode substrate surface is carried out at high temperatures (approximately 1100.degree.-1300.degree. C.) by a process of electrochemical vapor deposition. In this process, the mixed chlorides of the specific metals involved react in the gaseous state with water vapor resulting in the deposit of an impervious thin oxide layer on the support tube/air electrode substrate of between 20-50 microns in thickness. An internal heater, such as a heat pipe, is placed within the support tube/air electrode substrate and induces a uniform temperature profile therein so as to afford precise and uniform oxide deposition kinetics in an arrangement which is particularly adapted for large scale, commercial fabrication of SOFCs.

Seebeck coefficient of synthesized Titanium Dioxide thin film on FTO glass substrate

NASA Astrophysics Data System (ADS)

Usop, R.; Hamed, N. K. A.; Megat Hasnan, M. M. I.; Ikeda, H.; Sabri, M. F. M.; Ahmad, M. K.; Said, S. M.; Salleh, F.

2018-04-01

In order to fabricate a thermoelectric device on glass substrate for harvesting waste heat energy through house appliances, the Seebeck coefficient of translucent TiO2 thin film was investigated. The TiO2 thin film was synthesized by using hydrothermal method with F-SnO2 coated glass as substrate. From scanning electron microscopy analysis, the synthesized TiO2 thin film was found to be in nanometer-scale rod structure with a thickness of 4 µm. The Seebeck coefficient was measured in the temperature range of 300 – 400 K. The Seebeck coefficient is found to be in negative value which shows that synthesized film is an n-type semiconductor material, and is lower than the value of bulk-size material. This reduction in Seebeck coefficient of TiO2 thin film is likely due to the low dimensional effect and the difference of carrier concentration.

Modeling on the cathodoluminescence properties of the thin film phosphors for field emission flat panel displays

NASA Astrophysics Data System (ADS)

Cho, Kyu-Gong

2000-12-01

In order to investigate the effects of the film roughness with the fundamental luminance parameters of thin film phosphors, Y2 O3:Eu films with different thickness and roughness values were deposited on various substrate materials using a pulsed laser deposition technique under a controlled experimental procedure. The best luminous efficiency was observed from the Y2O3:Eu films on quartz substrates due to the smaller refractive index and low absorption characteristics of the quartz substrates which produce a larger amount of total internal reflection in the film and low loss of light intensity during the multiple internal reflections. The trapped light inside the film can escape the film more easily due to rougher film surface. The better epitaxial growth capability of the Y2O 3:Eu films with the LaAlO3 substrates resulted in higher luminous efficiency in the small surface roughness region. Higher luminous efficiency was observed in reflection mode than in transmission mode due to the contribution of diffusely scattered light at the air-film interface. A new theoretical model based on the diffraction scattering theory of light, the steady-state diffusion condition of carriers and the Kanaya-Okayama's electron- beam-solid interaction range satisfactorily explains all the experimental results mentioned above. The model also provides solid understandings on the cathodoluminescence properties of the thin film phosphors with the effects of other single or multiple luminance parameters. The parameters encountered for the model are surface roughness, electron-beam-solid interaction, surface recombination rate of carriers, charge carrier diffusion properties, multiple scattering at the interfaces (air- film, film-substrate, and substrate-air), optical properties of the material, film thickness, and substrate type. The model supplies a general solution in both qualitative and quantitative ways to estimate the luminance properties of the thin film phosphors and it can be utilized to optimize the thin film phosphor properties for the application of field emission flat panel displays.

Effects of the PPy layer thickness on Co-PPy composite films

NASA Astrophysics Data System (ADS)

Haciismailoglu, Murside

2015-11-01

Co-PPy composite films were electrodeposited on ITO substrate from two different solutions potentiostatically. Firstly, the PPy layers with the thicknesses changing from 20 to 5000 nm were produced on ITO. Then Co was electrodeposited on these PPy/ITO substrates with a charge density of 1000 mC cm-2. The electrochemical properties were investigated by the current density-time transients and the variation of the elapsed time for the Co deposition depending on the PPy layer thickness. X-ray photoelectron (XPS) spectra indicated the presence of both Co metal and its oxides on the surface. The weak reflections of the Co3O4, CoO and hcp Co were detected by the X-ray diffraction (XRD) technique. According to scanning electron microscopy (SEM) images, the thickness of the PPy layer strongly affects the Co nucleation. The composite films with the PPy layer thinner than 200 nm and thicker than 2000 nm have an isotropic magnetic behavior due to the symmetrical crystal field. The composite films with the PPy layer thicknesses between 200 and 2000 nm have an anisotropic magnetic behavior attributable to the deterioration of this symmetrical crystal field by the PPy bubbles on the surface. All films are hard magnetic material, since the coercivities are larger than 125 Oe.

Ultra-slim flexible glass for roll-to-roll electronic device fabrication

NASA Astrophysics Data System (ADS)

Garner, Sean; Glaesemann, Scott; Li, Xinghua

2014-08-01

As displays and electronics evolve to become lighter, thinner, and more flexible, the choice of substrate continues to be critical to their overall optimization. The substrate directly affects improvements in the designs, materials, fabrication processes, and performance of advanced electronics. With their inherent benefits such as surface quality, optical transmission, hermeticity, and thermal and dimensional stability, glass substrates enable high-quality and long-life devices. As substrate thicknesses are reduced below 200 μm, ultra-slim flexible glass continues to provide these inherent benefits to high-performance flexible electronics such as displays, touch sensors, photovoltaics, and lighting. In addition, the reduction in glass thickness also allows for new device designs and high-throughput, continuous manufacturing enabled by R2R processes. This paper provides an overview of ultra-slim flexible glass substrates and how they enable flexible electronic device optimization. Specific focus is put on flexible glass' mechanical reliability. For this, a combination of substrate design and process optimizations has been demonstrated that enables R2R device fabrication on flexible glass. Demonstrations of R2R flexible glass processes such as vacuum deposition, photolithography, laser patterning, screen printing, slot die coating, and lamination have been made. Compatibility with these key process steps has resulted in the first demonstration of a fully functional flexible glass device fabricated completely using R2R processes.

Theory of Liquid Film Growth and Wetting Instabilities on Graphene

NASA Astrophysics Data System (ADS)

Sengupta, Sanghita; Nichols, Nathan S.; Del Maestro, Adrian; Kotov, Valeri N.

2018-06-01

We investigate wetting phenomena near graphene within the Dzyaloshinskii-Lifshitz-Pitaevskii theory for light gases of hydrogen, helium, and nitrogen in three different geometries where graphene is either affixed to an insulating substrate, submerged or suspended. We find that the presence of graphene has a significant effect in all configurations. When placed on a substrate, the polarizability of graphene can increase the strength of the total van der Waals force by a factor of 2 near the surface, enhancing the propensity towards wetting. In a suspended geometry unique to two-dimensional materials, where graphene is able to wet on only one side, liquid film growth becomes arrested at a critical thickness, which may trigger surface instabilities and pattern formation analogous to spinodal dewetting. The existence of a mesoscopic critical film with a tunable thickness provides a platform for the study of a continuous wetting transition, as well as the engineering of custom liquid coatings. These phenomena are robust to some mechanical deformations and are also universally present in doped graphene and other two-dimensional materials, such as monolayer dichalcogenides.

Effects of Loading Frequency and Film Thickness on the Mechanical Behavior of Nanoscale TiN Film

NASA Astrophysics Data System (ADS)

Liu, Jin-na; Xu, Bin-shi; Wang, Hai-dou; Cui, Xiu-fang; Jin, Guo; Xing, Zhi-guo

2017-09-01

The mechanical properties of a nanoscale-thickness film material determine its reliability and service life. To achieve quantitative detection of film material mechanical performance based on nanoscale mechanical testing methods and to explore the influence of loading frequency of the cycle load on the fatigue test, a TiN film was prepared on monocrystalline silicon by magnetron sputtering. The microstructure of the nanoscale-thickness film material was characterized by using scanning electron microscopy and high-resolution transmission electron microscopy. The residual stress distribution of the thin film was obtained by using an electronic film stress tester. The hardness values and the fatigue behavior were measured by using a nanomechanical tester. Combined with finite element simulation, the paper analyzed the influence of the film thickness and loading frequency on the deformation, as well as the equivalent stress and strain. The results showed that the TiN film was a typical face-centered cubic structure with a large amount of amorphous. The residual compressive stress decreased gradually with increasing thin film thickness, and the influence of the substrate on the elastic modulus and hardness was also reduced. A greater load frequency would accelerate the dynamic fatigue damage that occurs in TiN films.

Bio-Inspired Bright Structurally Colored Colloidal Amorphous Array Enhanced by Controlling Thickness and Black Background.

PubMed

Iwata, Masanori; Teshima, Midori; Seki, Takahiro; Yoshioka, Shinya; Takeoka, Yukikazu

2017-07-01

Inspired by Steller's jay, which displays angle-independent structural colors, angle-independent structurally colored materials are created, which are composed of amorphous arrays of submicrometer-sized fine spherical silica colloidal particles. When the colloidal amorphous arrays are thick, they do not appear colorful but almost white. However, the saturation of the structural color can be increased by (i) appropriately controlling the thickness of the array and (ii) placing the black background substrate. This is similar in the case of the blue feather of Steller's jay. Based on the knowledge gained through the biomimicry of structural colored materials, colloidal amorphous arrays on the surface of a black particle as the core particle are also prepared as colorful photonic pigments. Moreover, a structural color on-off system is successfully built by controlling the background brightness of the colloidal amorphous arrays. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Direct grafting of anti-fouling polyglycerol layers to steel and other technically relevant materials.

PubMed

Weber, Theresa; Bechthold, Maren; Winkler, Tobias; Dauselt, John; Terfort, Andreas

2013-11-01

Direct grafting of hyperbranched polyglycerol (PG) layers onto the oxide surfaces of steel, aluminum, and silicon has been achieved through surface-initiated polymerization of 2-hydroxymethyloxirane (glycidol). Optimization of the deposition conditions led to a protocol that employed N-methyl-2-pyrrolidone (NMP) as the solvent and temperatures of 100 and 140 °C, depending on the substrate material. In all cases, a linear growth of the PG layers could be attained, which allows for control of film thickness by altering the reaction time. At layer thicknesses >5 nm, the PG layers completely suppressed the adhesion of albumin, fibrinogen, and globulin. These layers were also at least 90% bio-repulsive for two bacteria strains, E. coli and Acinetobacter baylyi, with further improvement being observed when the PG film thickness was increased to 17 nm (up to 99.9% bio-repulsivity on silicon). Copyright © 2013 Elsevier B.V. All rights reserved.

Optical properties of Pyromark 2500 coatings of variable thicknesses on a range of materials for concentrating solar thermal applications

NASA Astrophysics Data System (ADS)

Coventry, Joe; Burge, Patrick

2017-06-01

In this paper we present the results of solar absorptance measurements of four metallic substrate materials, either coated with Pyromark 2500 at various thicknesses, or uncoated and oxidised. Absorptance is measured prior to aging, and during and after aging at three elevated temperatures. In many cases, thin coatings perform as well, or better than thick coatings and do not appear to have a higher rate of failure. However, a thicker coating did show an advantage after aging at the highest temperature tested (850°C), and it is expected that with longer exposure, similar trends may emerge for the 600°C and 750°C aging cases. Another finding is that the two nickel-based alloys tested, Haynes 230 and Inconel 625, both formed an oxide with very good absorptance, although durability requires further testing.

Radiation pressure of light pulses and conservation of linear momentum in dispersive media.

PubMed

Scalora, Michael; D'Aguanno, Giuseppe; Mattiucci, Nadia; Bloemer, Mark J; Centini, Marco; Sibilia, Concita; Haus, Joseph W

2006-05-01

We derive an expression for the Minkowski momentum under conditions of dispersive susceptibility and permeability, and compare it to the Abraham momentum in order to test the principle of conservation of linear momentum when matter is present. We investigate cases when an incident pulse interacts with a variety of structures, including thick substrates, resonant, free-standing, micron-sized multilayer stacks, and negative index materials. In general, we find that for media only a few wavelengths thick the Minkowski and Abraham momentum densities yield similar results. For more extended media, including substrates and Bragg mirrors embedded inside thick dielectric substrates, our calculations show dramatic differences between the Minkowski and Abraham momenta. Without exception, in all cases investigated the instantaneous Lorentz force exerted on the medium is consistent only with the rate of change of the Abraham momentum. As a practical example, we use our model to predict that electromagnetic momentum and energy buildup inside a multilayer stack can lead to widely tunable accelerations that may easily reach and exceed 10(10) m/s(2) for a mass of 10(-5) g. Our results suggest that the physics of the photonic band edge and other similar finite structures may be used as a testing ground for basic electromagnetic phenomena such as momentum transfer to macroscopic media.

Zone compensated multilayer laue lens and apparatus and method of fabricating the same

DOEpatents

Conley, Raymond P.; Liu, Chian Qian; Macrander, Albert T.; Yan, Hanfei; Maser, Jorg; Kang, Hyon Chol; Stephenson, Gregory Brian

2015-07-14

A multilayer Laue Lens includes a compensation layer formed in between a first multilayer section and a second multilayer section. Each of the first and second multilayer sections includes a plurality of alternating layers made of a pair of different materials. Also, the thickness of layers of the first multilayer section is monotonically increased so that a layer adjacent the substrate has a minimum thickness, and the thickness of layers of the second multilayer section is monotonically decreased so that a layer adjacent the compensation layer has a maximum thickness. In particular, the compensation layer of the multilayer Laue lens has an in-plane thickness gradient laterally offset by 90.degree. as compared to other layers in the first and second multilayer sections, thereby eliminating the strict requirement of the placement error.

Hand-Held Units for Short-Range Wireless Biotelemetry

NASA Technical Reports Server (NTRS)

Miranda, Felix A.; Simons, Rainee N.

2008-01-01

Special-purpose hand-held radiotransceiver units have been proposed as means of short-range radio powering and interrogation of surgically implanted microelectromechanical sensors and actuators. These units are based partly on the same principles as those of the units described in "Printed Multi- Turn Loop Antennas for RF Biotelemetry" (LEW-17879-1), NASA Tech Briefs, Vol. 31, No. 6 (June 2007), page 48. Like the previously reported units, these units would make it unnecessary to have wire connections between the implanted devices and the external equipment used to activate and interrogate them. Like a unit of the previously reported type, a unit of the type now proposed would include a printed-circuit antenna on a dielectric substrate. The antenna circuitry would include integrated surface-mount inductors for impedance tuning. Circuits for processing the signals transmitted and received by the antenna would be included on the substrate. During operation, the unit would be positioned near (but not in electrical contact with) a human subject, in proximity to a microelectromechanical sensor or actuator that has been surgically implanted in the subject. It has been demonstrated that significant electromagnetic coupling with an implanted device could be established at a distance of as much as 4 in. (.10 cm). During operation in the interrogation mode, the antenna of the unit would receive a radio telemetry signal transmitted by the surgically implanted device. The antenna substrate would have dimensions of approximately 3.25 by 3.75 inches (approximately 8.3 by 9.5 cm). The substrate would have a thickness of the order of 30 mils (of the order of a somewhat less than a millimeter). The substrate would be made of low-radiofrequency- loss dielectric material that could be, for example, fused quartz, alumina, or any of a number of commercially available radio-frequency dielectric composite materials. The antenna conductors would typically be made of copper or a combination of chromium and gold. The choice of metal and the thickness of the metal layer(s) would depend on the choice of substrate material. For example, on a quartz or alumina substrate, one would typically use a layer of chromium 150 A thick and a layer of gold 2 m thick. The proposed units and the implanted devices that they would interrogate or activate would be inherently safe to use. They would operate at low radiated-power levels for short interrogation times (typically, milliseconds). Hence, there would be little local heating of tissues surrounding the implanted devices and little absorption of radio energy by such sensitive body parts as the eyes and the brain. Because the implanted devices would not depend on battery power and would be activated only during short interrogation intervals and would otherwise be in the goff h state most of the time, the useful lifetimes of the implanted devices would be greater than those of comparable battery-powered implanted devices. The compactness of the hand-held transceiver units would facilitate transport and storage and would facilitate self-diagnosis by patients able to handle the units while away from medical facilities.

Variation of superconducting transition temperature by proximity effect in NbN/FeN bilayers

NASA Astrophysics Data System (ADS)

Hwang, Tae-Jong; Kim, Dong-Ho

2017-09-01

We report on the proximity effect in superconductor/ferromagnet bilayers made of a new combination of NbN for the superconductor and FeN for the ferromagnet. The bilayers were prepared by reactive magnetron sputtering on a thermally oxidized Si substrate. For a constant NbN layer thickness, the superconducting transition temperatures of the bilayers exhibited a nonmonotonic dependence on the thickness of the FeN layer. The results were interpreted in terms of the proximity effect between the superconductor and ferromagnetic materials.

Microstrip Antenna Arrays on Multilayer LCP Substrates

NASA Technical Reports Server (NTRS)

Thompson, Dane; Bairavasubramanian, Ramanan; Wang, Guoan; Kingsley, Nickolas D.; Papapolymerou, Ioannis; Tenteris, Emmanouil M.; DeJean, Gerald; Li, RonglLin

2007-01-01

A research and development effort now underway is directed toward satisfying requirements for a new type of relatively inexpensive, lightweight, microwave antenna array and associated circuitry packaged in a thin, flexible sheet that can readily be mounted on a curved or flat rigid or semi-rigid surface. A representative package of this type consists of microwave antenna circuitry embedded in and/or on a multilayer liquid- crystal polymer (LCP) substrate. The circuitry typically includes an array of printed metal microstrip patch antenna elements and their feedlines on one or more of the LCP layer(s). The circuitry can also include such components as electrostatically actuated microelectromechanical systems (MEMS) switches for connecting and disconnecting antenna elements and feedlines. In addition, the circuitry can include switchable phase shifters described below. LCPs were chosen over other flexible substrate materials because they have properties that are especially attractive for high-performance microwave applications. These properties include low permittivity, low loss tangent, low water-absorption coefficient, and low cost. By means of heat treatments, their coefficients of thermal expansion can be tailored to make them more amenable to integration into packages that include other materials. The nature of the flexibility of LCPs is such that large LCP sheets containing antenna arrays can be rolled up, then later easily unrolled and deployed. Figure 1 depicts a prototype three- LCP-layer package containing two four-element, dual-polarization microstrip-patch arrays: one for a frequency of 14 GHz, the other for a frequency of 35 GHz. The 35-GHz patches are embedded on top surface of the middle [15-mil (approx.0.13-mm)-thick] LCP layer; the 14- GHz patches are placed on the top surface of the upper [9-mil (approx. 0.23-mm)-thick] LCP layer. The particular choice of LCP layer thicknesses was made on the basis of extensive analysis of the effects of the thicknesses on cross-polarization levels, bandwidth, and efficiency at each frequency.

Active constrained layer damping of geometrically nonlinear vibrations of functionally graded plates using piezoelectric fiber-reinforced composites

NASA Astrophysics Data System (ADS)

Panda, Satyajit; Ray, M. C.

2008-04-01

In this paper, a geometrically nonlinear dynamic analysis has been presented for functionally graded (FG) plates integrated with a patch of active constrained layer damping (ACLD) treatment and subjected to a temperature field. The constraining layer of the ACLD treatment is considered to be made of the piezoelectric fiber-reinforced composite (PFRC) material. The temperature field is assumed to be spatially uniform over the substrate plate surfaces and varied through the thickness of the host FG plates. The temperature-dependent material properties of the FG substrate plates are assumed to be graded in the thickness direction of the plates according to a power-law distribution while the Poisson's ratio is assumed to be a constant over the domain of the plate. The constrained viscoelastic layer of the ACLD treatment is modeled using the Golla-Hughes-McTavish (GHM) method. Based on the first-order shear deformation theory, a three-dimensional finite element model has been developed to model the open-loop and closed-loop nonlinear dynamics of the overall FG substrate plates under the thermal environment. The analysis suggests the potential use of the ACLD treatment with its constraining layer made of the PFRC material for active control of geometrically nonlinear vibrations of FG plates in the absence or the presence of the temperature gradient across the thickness of the plates. It is found that the ACLD treatment is more effective in controlling the geometrically nonlinear vibrations of FG plates than in controlling their linear vibrations. The analysis also reveals that the ACLD patch is more effective for controlling the nonlinear vibrations of FG plates when it is attached to the softest surface of the FG plates than when it is bonded to the stiffest surface of the plates. The effect of piezoelectric fiber orientation in the active constraining PFRC layer on the damping characteristics of the overall FG plates is also discussed.

Jet Fuel Thermal Stability Investigations Using Ellipsometry

NASA Technical Reports Server (NTRS)

Nash, Leigh; Vasu, Subith S.; Klettlinger, Jennifer Lindsey

2017-01-01

Jet fuels are typically used for endothermic cooling in practical engines where their thermal stability is very important. In this work the thermal stability of Sasol IPK (a synthetic jet fuel) with varying levels of naphthalene has been studied on stainless steel substrates using spectroscopic ellipsometry in the temperature range 385-400 K. Ellipsometry is an optical technique that measures the changes in a light beam’s polarization and intensity after it reflects off of a thin film to determine the film’s thickness and optical properties. All of the tubes used were rated as thermally unstable by the color standard portion of the Jet Fuel Thermal Oxidation Test, and this was confirmed by the deposit thicknesses observed using ellipsometry. A new amorphous model on a stainless steel substrate was used to model the data and obtain the results. It was observed that, as would be expected, increasing the temperature of the tube increased the overall deposit amount for a constant concentration of naphthalene. The repeatability of these measurements was assessed using multiple trials of the same fuel at 385 K. Lastly, the effect of increasing the naphthalene concentration in the fuel at a constant temperature was found to increase the deposit thickness.In conclusion, ellipsometry was used to investigate the thermal stability of jet fuels on stainless steel substrate. The effects of increasing temperature and addition of naphthalene on stainless steel tubes with Sasol IPK fuel were investigated. It was found, as expected, that increasing temperature lead to an increase in deposit thickness. It wasAmerican Institute of Aeronautics and Astronautics6also found that increasing amounts of naphthalene increased the maximum deposit thickness. The repeatability of these measurements was investigated using multiple tests at the same conditions. The present work provides as a better quantitative tool compared to the widely used JFTOT technique. Future work will expand on the fuel types, temperature, and substrate materials.

High-density optical disk readout using a blue laser diode and a transparent plastic substrate with 0.3-mm thickness

NASA Astrophysics Data System (ADS)

Park, Kyung-Chan; Lee, TaekSoo; Kim, Hyung-Nam; Jeong, SeongYun; Ahn, Seong-Keun; Kim, Jin-Yong; Lee, Jun-Seok; Kim, Ji-Byung; Lee, SeongWon; Lee, Dong C.; Asai, Ikuo

2000-09-01

We prepared and tested a disc that has a transparent plastic substrate of 0.3 mm thickness to confirm the readout capability using a blue laser diode. And the test results of injection molding for the plastic substrate of 0.3 mm thickness are shown.

2G HTS wires made on 30 μm thick Hastelloy substrate

NASA Astrophysics Data System (ADS)

Sundaram, A.; Zhang, Y.; Knoll, A. R.; Abraimov, D.; Brownsey, P.; Kasahara, M.; Carota, G. M.; Nakasaki, R.; Cameron, J. B.; Schwab, G.; Hope, L. V.; Schmidt, R. M.; Kuraseko, H.; Fukushima, T.; Hazelton, D. W.

2016-10-01

REBCO (RE = rare earth) based high temperature superconducting (HTS) wires are now being utilized for the development of electric and electromagnetic devices for various industrial, scientific and medical applications. In the last several years, the increasing efforts in using the so-called second generation (2G) HTS wires for some of the applications require a further increase in their engineering current density (J e). The applications are those typically related to high magnetic fields where the higher J e of a REBCO wire, in addition to its higher irreversibility fields and higher mechanical strength, is already a major advantage over other superconducting wires. An effective way to increase the J e is to decrease the total thickness of a wire, for which using a thinner substrate becomes an obvious and attractive approach. By using our IBAD-MOCVD (ion beam assisted deposition-metal organic chemical vapor deposition) technology we have successfully made 2G HTS wires using a Hastelloy® C276 substrate that is only 30 μm in thickness. By using this thinner substrate instead of the typical 50 μm thick substrate and with a same critical current (I c), the J e of a wire can be increased by 30% to 45% depending on the copper stabilizer thickness. In this paper, we report the fabrication and characterization of the 2G HTS wires made on the 30 μm thick Hastelloy® C276 substrate. It was shown that with the optimization in the processing protocol, the surface of the thinner Hastelloy® C276 substrate can be readily electropolished to the quality needed for the deposition of the buffer stack. Same in the architecture as that on the standard 50 μm thick substrate, the buffer stack made on the 30 μm thick substrate showed an in-plane texture with a Δϕ of around 6.7° in the LaMnO3 cap layer. Low-temperature in-field transport measurement results suggest that the wires on the thinner substrate had achieved equivalent superconducting performance, most importantly the I c, as those on the 50 μm thick substrate. It is expected the 2G HTS wires made on the 30 μm thick Hastelloy® C276 substrate, the thinnest and with the highest J e to date, will greatly benefit such applications as high field magnets and high current cables.

Antibacterial graphene oxide coatings on polymer substrate

NASA Astrophysics Data System (ADS)

Liu, Yiming; Wen, Jing; Gao, Yang; Li, Tianyang; Wang, Huifang; Yan, Hong; Niu, Baolong; Guo, Ruijie

2018-04-01

Graphene oxide (GO) was thought to be a promising antibacterial material. In this work, graphene oxide coatings on polymer substrate were prepared and the antibacterial activity against E. coli and S. aureus was investigated. It was demonstrated that the coatings exhibited stronger antibacterial activity against E. coli with thin membrane than S. aureus with thick membrane. Take into consideration the fact that the coatings presented smooth, sharp edges-free morphology and bonded parallelly to substrate, which was in mark contrast with their precursor GO nanosheets, oxidative stress mechanism was considered the main factor of antibacterial activity. The coatings, which are easy to recycle and have no inhalation risk, provide an alternative for application in antibacterial medical instruments.

Textile materials for the design of wearable antennas: a survey.

PubMed

Salvado, Rita; Loss, Caroline; Gonçalves, Ricardo; Pinho, Pedro

2012-11-15

In the broad context of Wireless Body Sensor Networks for healthcare and pervasive applications, the design of wearable antennas offers the possibility of ubiquitous monitoring, communication and energy harvesting and storage. Specific requirements for wearable antennas are a planar structure and flexible construction materials. Several properties of the materials influence the behaviour of the antenna. For instance, the bandwidth and the efficiency of a planar microstrip antenna are mainly determined by the permittivity and the thickness of the substrate. The use of textiles in wearable antennas requires the characterization of their properties. Specific electrical conductive textiles are available on the market and have been successfully used. Ordinary textile fabrics have been used as substrates. However, little information can be found on the electromagnetic properties of regular textiles. Therefore this paper is mainly focused on the analysis of the dielectric properties of normal fabrics. In general, textiles present a very low dielectric constant that reduces the surface wave losses and increases the impedance bandwidth of the antenna. However, textile materials are constantly exchanging water molecules with the surroundings, which affects their electromagnetic properties. In addition, textile fabrics are porous, anisotropic and compressible materials whose thickness and density might change with low pressures. Therefore it is important to know how these characteristics influence the behaviour of the antenna in order to minimize unwanted effects. This paper presents a survey of the key points for the design and development of textile antennas, from the choice of the textile materials to the framing of the antenna. An analysis of the textile materials that have been used is also presented.

Textile Materials for the Design of Wearable Antennas: A Survey

PubMed Central

Salvado, Rita; Loss, Caroline; Gonçalves, Ricardo; Pinho, Pedro

2012-01-01

In the broad context of Wireless Body Sensor Networks for healthcare and pervasive applications, the design of wearable antennas offers the possibility of ubiquitous monitoring, communication and energy harvesting and storage. Specific requirements for wearable antennas are a planar structure and flexible construction materials. Several properties of the materials influence the behaviour of the antenna. For instance, the bandwidth and the efficiency of a planar microstrip antenna are mainly determined by the permittivity and the thickness of the substrate. The use of textiles in wearable antennas requires the characterization of their properties. Specific electrical conductive textiles are available on the market and have been successfully used. Ordinary textile fabrics have been used as substrates. However, little information can be found on the electromagnetic properties of regular textiles. Therefore this paper is mainly focused on the analysis of the dielectric properties of normal fabrics. In general, textiles present a very low dielectric constant that reduces the surface wave losses and increases the impedance bandwidth of the antenna. However, textile materials are constantly exchanging water molecules with the surroundings, which affects their electromagnetic properties. In addition, textile fabrics are porous, anisotropic and compressible materials whose thickness and density might change with low pressures. Therefore it is important to know how these characteristics influence the behaviour of the antenna in order to minimize unwanted effects. This paper presents a survey of the key points for the design and development of textile antennas, from the choice of the textile materials to the framing of the antenna. An analysis of the textile materials that have been used is also presented. PMID:23202235

Determining confounding sensitivities in eddy current thin film measurements

NASA Astrophysics Data System (ADS)

Gros, Ethan; Udpa, Lalita; Smith, James A.; Wachs, Katelyn

2017-02-01

Eddy current (EC) techniques are widely used in industry to measure the thickness of non-conductive films on a metal substrate. This is done by using a system whereby a coil carrying a high-frequency alternating current is used to create an alternating magnetic field at the surface of the instrument's probe. When the probe is brought near a conductive surface, the alternating magnetic field will induce ECs in the conductor. The substrate characteristics and the distance of the probe from the substrate (the coating thickness) affect the magnitude of the ECs. The induced currents load the probe coil affecting the terminal impedance of the coil. The measured probe impedance is related to the lift off between coil and conductor as well as conductivity of the test sample. For a known conductivity sample, the probe impedance can be converted into an equivalent film thickness value. The EC measurement can be confounded by a number of measurement parameters. It was the goal of this research to determine which physical properties of the measurement set-up and sample can adversely affect the thickness measurement. The eddy-current testing was performed using a commercially available, hand-held eddy-current probe (ETA3.3H spring-loaded eddy probe running at 8 MHz) that comes with a stand to hold the probe. The stand holds the probe and adjusts the probe on the z-axis to help position the probe in the correct area as well as make precise measurements. The signal from the probe was sent to a hand-held readout, where the results are recorded directly in terms of liftoff or film thickness. Understanding the effect of certain factors on the measurements of film thickness, will help to evaluate how accurate the ETA3.3H spring-loaded eddy probe was at measuring film thickness under varying experimental conditions. This research studied the effects of a number of factors such as i) conductivity, ii) edge effect, iii) surface finish of base material and iv) cable condition.

NbN superconducting nanowire single-photon detector fabricated on MgF2 substrate

NASA Astrophysics Data System (ADS)

Wu, J. J.; You, L. X.; Zhang, L.; Zhang, W. J.; Li, H.; Liu, X. Y.; Zhou, H.; Wang, Z.; Xie, X. M.; Xu, Y. X.; Fang, W.; Tong, L. M.

2016-06-01

The performance of superconducting nanowire single-photon detectors (SNSPDs) relies on substrate materials. Magnesium fluoride (MgF2) exhibits outstanding optical properties, such as large optical transmission range and low refractive index (n = 1.38), making it an attractive substrate. We present the fabrication and the performance of SNSPDs made of a 4.5 nm thick NbN thin film deposited on MgF2 substrate for the wavelength of 1550 nm. The front-side illuminated SNSPDs without an optical cavity showed a maximal detection efficiency of 12.8% at a system dark count rate (DCR) of 100 Hz, while the backside illuminated SNSPDs with a SiO2/Au optical cavity atop displayed a maximal detection efficiency of 33% at a DCR of 100 Hz.

High spectral selectivity for solar absorbers using a monolayer transparent conductive oxide coated on a metal substrate

NASA Astrophysics Data System (ADS)

Shimizu, Makoto; Suzuki, Mari; Iguchi, Fumitada; Yugami, Hiroo

2017-05-01

A spectrally selective absorber composed of a monolayer transparent conductive oxide (TCO) coated on a metal substrate is investigated for use in solar systems operating at temperatures higher (>973 K) than the operation temperature of conventional systems ( ˜ 673 K). This method is different from the currently used solar-selective coating technologies, such as those using multilayered and cermet materials. The spectral selective absorption property can be attributed to the inherent optical property of TCO owing to the plasma frequency and interferences between the substrates. Since spectral selectivity can be achieved using monolayered materials, the effect of atomic diffusion occurring at each layer boundary in a multilayer or cermet coatings under high-temperature conditions can be reduced. In addition, since this property is attributed to the inherent property of TCO, the precise control of the layer thickness can be omitted if the layer is sufficiently thick (>0.5 μm). The optimum TCO properties, namely, carrier density and mobility, required for solar-selective absorbers are analyzed to determine the cutoff wavelength and emittance in the infrared range. A solar absorptance of 0.95 and hemispherical emittance of 0.10 at 973 K are needed for achieving the optimum TCO properties, i.e., a carrier density of 5.5 × 1020 cm-3 and mobility of 90 cm2 V-1 s-1 are required. Optical simulations indicate that the spectrally selective absorption weakly depends on the incident angle and film thickness. The thermal stability of the fabricated absorber treated at temperatures up to 973 K for 10 h is verified in vacuum by introducing a SiO2 interlayer, which plays an important role as a diffusion barrier.

Influence of viscoelastic property on laser-generated surface acoustic waves in coating-substrate systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun Hongxiang; Faculty of Science, Jiangsu University, Zhenjiang 212013; Zhang Shuyi

2011-04-01

Taking account of the viscoelasticity of materials, the pulsed laser generation of surface acoustic waves in coating-substrate systems has been investigated quantitatively by using the finite element method. The displacement spectra of the surface acoustic waves have been calculated in frequency domain for different coating-substrate systems, in which the viscoelastic properties of the coatings and substrates are considered separately. Meanwhile, the temporal displacement waveforms have been obtained by applying inverse fast Fourier transforms. The numerical results of the normal surface displacements are presented for different configurations: a single plate, a slow coating on a fast substrate, and a fast coatingmore » on a slow substrate. The influences of the viscoelastic properties of the coating and the substrate on the attenuation of the surface acoustic waves have been studied. In addition, the influence of the coating thickness on the attenuation of the surface acoustic waves has been also investigated in detail.« less

An Investigation into III-V Compounds to Reach 20% Efficiency with Minimum Cell Thickness in Ultrathin-Film Solar Cells

NASA Astrophysics Data System (ADS)

Haque, K. A. S. M. Ehteshamul; Galib, Md. Mehedi Hassan

2013-10-01

III-V single-junction solar cells have already achieved very high efficiency levels. However, their use in terrestrial applications is limited by the high fabrication cost. High-efficiency, ultrathin-film solar cells can effectively solve this problem, as their material requirement is minimum. This work presents a comparison among several III-V compounds that have high optical absorption capability as well as optimum bandgap (around 1.4 eV) for use as solar cell absorbers. The aim is to observe and compare the ability of these materials to reach a target efficiency level of 20% with minimum possible cell thickness. The solar cell considered has an n-type ZnSe window layer, an n-type Al0.1Ga0.9As emitter layer, and a p-type Ga0.5In0.5P back surface field (BSF) layer. Ge is used as the substrate. In the initial design, a p-type InP base was sandwiched between the emitter and the BSF layer, and the design parameters for the device were optimized by analyzing the simulation outcomes with ADEPT/F, a one-dimensional (1D) simulation tool. Then, the minimum cell thickness that achieves 20% efficiency was determined by observing the efficiency variation with cell thickness. Afterwards, the base material was changed to a few other selected III-V compounds, and for each case, the minimum cell thickness was determined in a similar manner. Finally, these cell thickness values were compared and analyzed to identify more effective base layer materials for III-V single-junction solar cells.

Microstructured polymer films by X-ray lithographic exposure and grafting

NASA Astrophysics Data System (ADS)

Gürsel, Selmiye A.; Padeste, Celestino; Solak, Harun H.; Scherer, Günther G.

2005-07-01

Recently we reported on a new technique to generate micro- and nanostructured polymer materials by the combination of selective irradiation of polymer substrates with X-rays and subsequent grafting of a second polymer. Here we focus on the spatially defined grafting throughout the thickness of poly(ethylene-alt-tetrafluoroethylene) (ETFE) and poly (tetrafluoroethylene-co-hexafluoropropylene) (FEP) films using X-ray irradiation through a metal mask, followed by grafting with styrene. Calculations of the transmission of X-rays through the polymer as a function of the wavelength have revealed that energy deposition within the substrate material, which should control the density of created radicals, can be selected in a wide range. Depending on the used wavelength the radicals are created either near the surface or in the bulk of the sample. First experiments demonstrated spatially defined grafting through a 100 μm thick ETFE film and 25 μm thick FEP film. The achieved graft level depends on the irradiation dose as well as on the grafting parameters such as concentration, temperature and time. The precision of structure definition within the film depends on the properties of the X-ray source, the metal mask and the grafting process. The presented process allows controlled grafting through fluoropolymer films with micrometer resolution and local modification of the properties of the films, such as ion conductivity, diffusion of specific molecules or optical properties.

Packaging Technologies for 500 C SiC Electronics and Sensors: Challenges in Material Science and Technology

NASA Technical Reports Server (NTRS)

Chen, Liang-Yu; Neudeck, Philip G.; Behelm, Glenn M.; Spry, David J.; Meredith, Roger D.; Hunter, Gary W.

2015-01-01

This paper presents ceramic substrates and thick-film metallization based packaging technologies in development for 500C silicon carbide (SiC) electronics and sensors. Prototype high temperature ceramic chip-level packages and printed circuit boards (PCBs) based on ceramic substrates of aluminum oxide (Al2O3) and aluminum nitride (AlN) have been designed and fabricated. These ceramic substrate-based chip-level packages with gold (Au) thick-film metallization have been electrically characterized at temperatures up to 550C. The 96 alumina packaging system composed of chip-level packages and PCBs has been successfully tested with high temperature SiC discrete transistor devices at 500C for over 10,000 hours. In addition to tests in a laboratory environment, a SiC junction field-effect-transistor (JFET) with a packaging system composed of a 96 alumina chip-level package and an alumina printed circuit board was tested on low earth orbit for eighteen months via a NASA International Space Station experiment. In addition to packaging systems for electronics, a spark-plug type sensor package based on this high temperature interconnection system for high temperature SiC capacitive pressure sensors was also developed and tested. In order to further significantly improve the performance of packaging system for higher packaging density, higher operation frequency, power rating, and even higher temperatures, some fundamental material challenges must be addressed. This presentation will discuss previous development and some of the challenges in material science (technology) to improve high temperature dielectrics for packaging applications.

Densified edge seals for fuel cell components

DOEpatents

DeCasperis, Anthony J.; Roethlein, Richard J.; Breault, Richard D.

1982-01-01

A porous fuel cell component, such as an electrode substrate, has a densified edge which forms an improved gas seal during operation when soaked with electrolyte. The edges are made from the same composition as the rest of the component and are made by compressing an increased thickness of this material along the edges during the fabrication process.

Why we need to look beyond the glass transition temperature to characterize the dynamics of thin supported polymer films.

PubMed

Zhang, Wengang; Douglas, Jack F; Starr, Francis W

2018-05-29

There is significant variation in the reported magnitude and even the sign of [Formula: see text] shifts in thin polymer films with nominally the same chemistry, film thickness, and supporting substrate. The implicit assumption is that methods used to estimate [Formula: see text] in bulk materials are relevant for inferring dynamic changes in thin films. To test the validity of this assumption, we perform molecular simulations of a coarse-grained polymer melt supported on an attractive substrate. As observed in many experiments, we find that [Formula: see text] based on thermodynamic criteria (temperature dependence of film height or enthalpy) decreases with decreasing film thickness, regardless of the polymer-substrate interaction strength ε. In contrast, we find that [Formula: see text] based on a dynamic criterion (relaxation of the dynamic structure factor) also decreases with decreasing thickness when ε is relatively weak, but [Formula: see text] increases when ε exceeds the polymer-polymer interaction strength. We show that these qualitatively different trends in [Formula: see text] reflect differing sensitivities to the mobility gradient across the film. Apparently, the slowly relaxing polymer segments in the substrate region make the largest contribution to the shift of [Formula: see text] in the dynamic measurement, but this part of the film contributes less to the thermodynamic estimate of [Formula: see text] Our results emphasize the limitations of using [Formula: see text] to infer changes in the dynamics of polymer thin films. However, we show that the thermodynamic and dynamic estimates of [Formula: see text] can be combined to predict local changes in [Formula: see text] near the substrate, providing a simple method to infer information about the mobility gradient.

Effect of substrate preheating temperature and coating thickness on residual stress in plasma sprayed hydroxyapatite coating

NASA Astrophysics Data System (ADS)

Tang, Dapei

2015-07-01

A thermal-mechanical coupling model was developed based on thermal-elastic- plastic theory according the special process of plasma spraying Hydroxyapatite (HA) coating upon Ti-6Al-4V substrate. On the one hand, the classical Fourier transient heat conduction equation was modified by introducing the effect item of deformation on temperature, on the other hand, the Johnson-Cook model, suitable for high temperature and high strain rate conditions, was used as constitutive equation after considering temperature softening effect, strain hardening effect and strain rate reinforcement effect. Based on the above coupling model, the residual stress field within the HA coating was simulated by using finite element method (FEM). Meanwhile, the substrate preheating temperature and coating thickness on the influence of residual stress components were calculated, respectively. The failure modes of coating were also preliminary analyzed. In addition, in order to verify the reliability of calculation, the material removal measurement technique was applied to determine the residual stress of HA coating near the interface. Some important conclusions are obtained.

High-Performance Ultrathin Organic-Inorganic Hybrid Silicon Solar Cells via Solution-Processed Interface Modification.

PubMed

Zhang, Jie; Zhang, Yinan; Song, Tao; Shen, Xinlei; Yu, Xuegong; Lee, Shuit-Tong; Sun, Baoquan; Jia, Baohua

2017-07-05

Organic-inorganic hybrid solar cells based on n-type crystalline silicon and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) exhibited promising efficiency along with a low-cost fabrication process. In this work, ultrathin flexible silicon substrates, with a thickness as low as tens of micrometers, were employed to fabricate hybrid solar cells to reduce the use of silicon materials. To improve the light-trapping ability, nanostructures were built on the thin silicon substrates by a metal-assisted chemical etching method (MACE). However, nanostructured silicon resulted in a large amount of surface-defect states, causing detrimental charge recombination. Here, the surface was smoothed by solution-processed chemical treatment to reduce the surface/volume ratio of nanostructured silicon. Surface-charge recombination was dramatically suppressed after surface modification with a chemical, associated with improved minority charge-carrier lifetime. As a result, a power conversion efficiency of 9.1% was achieved in the flexible hybrid silicon solar cells, with a substrate thickness as low as ∼14 μm, indicating that interface engineering was essential to improve the hybrid junction quality and photovoltaic characteristics of the hybrid devices.

SiGe derivatization by spontaneous reduction of aryl diazonium salts

NASA Astrophysics Data System (ADS)

Girard, A.; Geneste, F.; Coulon, N.; Cardinaud, C.; Mohammed-Brahim, T.

2013-10-01

Germanium semiconductors have interesting properties for FET-based biosensor applications since they possess high surface roughness allowing the immobilization of a high amount of receptors on a small surface area. Since SiGe combined low cost of Si and intrinsic properties of Ge with high mobility carriers, we focused the study on this particularly interesting material. The comparison of the efficiency of a functionalization process involving the spontaneous reduction of diazonium salts is studied on Si(1 0 0), SiGe and Ge semiconductors. XPS analysis of the functionalized surfaces reveals the presence of a covalent grafted layer on all the substrates that was confirmed by AFM. Interestingly, the modified Ge derivatives have still higher surface roughness after derivatization. To support the estimated thickness by XPS, a step measurement of the organic layers is done by AFM or by profilometer technique after a O2 plasma etching of the functionalized layer. This original method is well-adapted to measure the thickness of thin organic films on rough substrates such as germanium. The analyses show a higher chemical grafting on SiGe substrates compared with Si and Ge semiconductors.

Si Complies with GaN to Overcome Thermal Mismatches for the Heteroepitaxy of Thick GaN on Si.

PubMed

Tanaka, Atsunori; Choi, Woojin; Chen, Renjie; Dayeh, Shadi A

2017-10-01

Heteroepitaxial growth of lattice mismatched materials has advanced through the epitaxy of thin coherently strained layers, the strain sharing in virtual and nanoscale substrates, and the growth of thick films with intermediate strain-relaxed buffer layers. However, the thermal mismatch is not completely resolved in highly mismatched systems such as in GaN-on-Si. Here, geometrical effects and surface faceting to dilate thermal stresses at the surface of selectively grown epitaxial GaN layers on Si are exploited. The growth of thick (19 µm), crack-free, and pure GaN layers on Si with the lowest threading dislocation density of 1.1 × 10 7 cm -2 achieved to date in GaN-on-Si is demonstrated. With these advances, the first vertical GaN metal-insulator-semiconductor field-effect transistors on Si substrates with low leakage currents and high on/off ratios paving the way for a cost-effective high power device paradigm on an Si CMOS platform are demonstrated. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Microwave absorption studies of high T sub c superconductors and related materials 8; ESR of DPPH coated on BiSrCaCuO films fabricated on MgO (100) substrates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sugawara, K.; Tanaka, S.

1992-06-20

This paper reports that ESR of DPPH coated on Bi-Sr-Ca-Cu-O films fabricated on MgO (100) substrates by MOCVD have been studied for samples with different thicknesses, 1000 {Angstrom} and 100 {Angstrom}. Temperature dependence of the ESR peak-to-peak linewidth, {Delta}H{sub pp}, revealed that {Delta}H{sub pp} increases with film thickness. The Excess ESR linewidth, {delta}({Delta}H{sub pp}) was also analyzed in terms of (1 {minus} t{sup alpha}, with t = T/T{sub c}, giving for example {alpha} = 4 ={minus}1 for the 1000 {Angstrom} thick sample. The ESR lineshapes were distorted by rotating the samples in applied magnetic fields. Severe distortion was found formore » the 1000 {Angstrom} sample below about 30 K, but the distortion almost disappears at temperatures above 30 K. The applied magnetic field effects were also examined in both field-cooled and zero-field-cooled cases.« less

Wax transfer printing to enable robust barrier definition in devices based on non-standard porous materials

NASA Astrophysics Data System (ADS)

To, Anthony; Downs, Corey; Fu, Elain

2017-05-01

Wax printing has become a common method of fabricating channels in cellulose-based microfluidic devices. However, a limitation of wax printing is that it is restricted to relatively thin, smooth substrates that are compatible with processing by a commercial wax printer. In the current report, we describe a simple patterning method that extends the utility of wax printers for creating hydrophobic barriers on non-standard porous substrates via a process called wax transfer printing. We demonstrate the use of multiple wax transfer cycles to create well-defined, robust, and reproducible barriers in a thick cellulose substrate that is not compatible with feeding through a wax printer. We characterize the method for (i) wax spreading within the substrate as a function of heating time, (ii) the ability to create functional barriers in a substrate, and (iii) reproducibility in line width.

Optimization of solar cells for air mass zero operation and a study of solar cells at high temperatures

NASA Technical Reports Server (NTRS)

Hovel, H. J.; Vernon, S. M.

1982-01-01

The power to weight ratio of GaAs cells can be reduced by fabricating devices using thin GaAs films on low density substrate materials (silicon, glass, plastics). A graphoepitaxy technique was developed which uses fine geometric patterns in the substrate to affect growth. Initial substrates were processed by etching 25 microns deep grooves into 100 oriented wafers; fine-grained polycrystalline GaAs layers 25-50 microns thick were then deposited on these and recrystallization was performed, heating the substrates to above the GaAs melting point in ASH3 atmosphere, resulting in large grain regrowth oriented along the groove dimensions. Experiments with smaller groove depths and spacings were initially encouraging; single large GaAs grains would totally cover one and often two groove fields of 14 groove each spanning several hundred microns. Dielectric coatings on the grooved substrates were also used to modify the growth.

Colorless polyimide/organoclay nanocomposite substrates for flexible organic light-emitting devices.

PubMed

Kim, Jin-Hoe; Choi, Myeon-Chon; Kim, Hwajeong; Kim, Youngkyoo; Chang, Jin-Hae; Han, Mijeong; Kim, Il; Ha, Chang-Sik

2010-01-01

We report the preparation and application of indium tin oxide (ITO) coated fluorine-containing polyimide/organoclay nanocomposite substrate. Fluorine-containing polyimide/organoclay nanocomposite films were prepared through thermal imidization of poly(amic acid)/organoclay mixture films, whilst on which ITO thin films were coated on the films using a radio-frequency planar magnetron sputtering by varying the substrate temperature and the ITO thickness. Finally the ITO coated fluorine-containing polyimide/organoclay nanocomposite substrate was employed to make flexible organic light-emitting devices (OLED). Results showed that the lower sheet resistance was achieved when the substrate temperature was high and the ITO film was thick even though the optical transmittance was slightly lowered as the thickness increased. approximately 10 nm width ITO nanorods were found for all samples but the size of clusters with the nanorods was generally increased with the substrate temperature and the thickness. The flexible OLED made using the present substrate was quite stable even when the device was extremely bended.

Time-dependent areal mass density for disc-shaped substrates in a corona-activated flow stream at atmospheric pressure for argon/acetylene admixture

NASA Astrophysics Data System (ADS)

Xie, Shuzheng; Islam, Rokibul; Hussein, Bashir; Englund, Karl; Pedrow, Patrick

2015-09-01

In this research we use a 40-needle array energized with 60 Hz AC voltage in the range 5 to 15 kV RMS. Plasma processing takes place downstream from a grounded planar screen (the opposing electrode). The needle-to-screen gap is in the range 4 to 10 cm and its E-field generates weakly ionized plasma via streamers and back corona. Deposited material is plasma-polymerized acetylene. Substrates are potassium bromide, mica, wood, paper, and gold-covered solids. Substrate chemical species influence the efficiency with which the disc amasses plasma-polymerized material, at least until the substrate is fully covered with film. Early plasma-polymerization is accompanied by nucleation-site-dominated nodules but longer term deposition results in a film that fully covers the substrate. We will report on time-dependent areal mass density associated with run times in the range 5-60 minutes. Film thickness will be measured using instruments that include visible light microscopy, TEM, and SEM. Others in our research group are studying areal mass density for early times (1-5 minutes) when nodule growth (at nucleation sites) dominates the deposition process.

Yttria stabilized zirconia transparent films prepared by chemical vapor deposition

NASA Astrophysics Data System (ADS)

Yamane, Hisanori; Hirai, Toshio

1989-04-01

Yttria stabilized zirconia (YSZ) transparent films were prepared on quartz glass substrates at the temperature of 1375 K under atmospheric pressure using ZrCl 4, YCl 3 and O 2 gases as source materials. The growth rate of the film thickness was 1.5 to 2.0 μm/h. Cubic YSZ films were obtained at the value of x between 20 to 60, where x is defined by x( wt%) = YCl3×100/( YCl3+ ZrCl4). The lattice parameter of the cubic YSZ increased from 5.14 to 5.19 Å with the increase of x. Transparent films were obtained at the interval where the x value was between 20 to 45. The (100) plane of YSZ is oriented parallel to the surface of the substrate. For transparent film obtained at x = 29 (1.5 μm in thickness) the optical transmittance was 50-70% in the wavelength range of 250-800 nm.

Basic research challenges in crystalline silicon photovoltaics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Werner, J.H.

1995-08-01

Silicon is abundant, non-toxic and has an ideal band gap for photovoltaic energy conversion. Experimental world record cells of 24 % conversion efficiency with around 300 {mu}m thickness are only 4 % (absolute) efficiency points below the theoretical Auger recombination-limit of around 28 %. Compared with other photovoltaic materials, crystalline silicon has only very few disadvantages. The handicap of weak light absorbance may be mastered by clever optical designs. Single crystalline cells of only 48 {mu}m thickness showed 17.3 % efficiency even without backside reflectors. A technology of solar cells from polycrystalline Si films on foreign substrates arises at themore » horizon. However, the disadvantageous, strong activity of grain boundaries in Si could be an insurmountable hurdle for a cost-effective, terrestrial photovoltaics based on polycrystalline Si on foreign substrates. This talk discusses some basic research challenges related to a Si based photovoltaics.« less

Characterization of damage modes in dental ceramic bilayer structures.

PubMed

Deng, Yan; Lawn, Brian R; Lloyd, Isabel K

2002-01-01

Results of contact tests using spherical indenters on flat ceramic coating layers bonded to compliant substrates are reported for selected dental ceramics. Critical loads to produce various damage modes, cone cracking, and quasiplasticity at the top surfaces and radial cracking at the lower (inner) surfaces are measured as a function of ceramic-layer thickness. It is proposed that these damage modes, especially radial cracking, are directly relevant to the failure of all-ceramic dental crowns. The critical load data are analyzed with the use of explicit fracture-mechanics relations, expressible in terms of routinely measurable material parameters (elastic modulus, strength, toughness, hardness) and essential geometrical variables (layer thickness, contact radius). The utility of such analyses in the design of ceramic/substrate bilayer systems for optimal resistance to lifetime-threatening damage is discussed. Copyright 2002 Wiley Periodicals, Inc. J Biomed Mater Res (Appl Biomater) 63: 137--145, 2002; DOI 10.1002/jbm.10091

Capillary trapping of particles in thin-film flows

NASA Astrophysics Data System (ADS)

Dressaire, Emilie; Gomez, Michael; Colnet, Benedicte; Sauret, Alban

2017-11-01

When a thin layer of suspension flows over a substrate, some particles remain trapped on the solid surface. When the thickness of the liquid layer is comparable to the particle size, the particles deform the liquid interface, which leads to local interactions. These effects modify the transport of particles and the dynamics of the liquid films. Here, we characterize how capillary interactions affect the transport and deposition of non-Brownian particles moving in thin liquid films and the resulting loss of transported material. We focus on gravitational drainage flows, in which the film thickness becomes comparable to the particle size. Depending on the concentration of particles, we find that the drainage dynamics exhibits behavior that cannot be captured with a continuum model, due to the deposition of particles on the substrate. ANR-16-CE30-0009 & CNRS-PICS-07242 & ACS-PRF 55845-ND9.

Thickness-dependent electron–lattice equilibration in laser-excited thin bismuth films

DOE PAGES

Sokolowski-Tinten, K.; Li, R. K.; Reid, A. H.; ...

2015-11-19

Electron–phonon coupling processes determine electronic transport properties of materials and are responsible for the transfer of electronic excess energy to the lattice. With decreasing device dimensions an understanding of these processes in nanoscale materials is becoming increasingly important. We use time-resolved electron diffraction to directly study energy relaxation in thin bismuth films after optical excitation. Precise measurements of the transient Debye–Waller-effect for various film thicknesses and over an extended range of excitation fluences allow to separate different contributions to the incoherent lattice response. While phonon softening in the electronically excited state is responsible for an immediate increase of the r.m.s.more » atomic displacement within a few hundred fs, 'ordinary' electron–phonon coupling leads to subsequent heating of the material on a few ps time-scale. Moreover, the data reveal distinct changes in the energy transfer dynamics which becomes faster for stronger excitation and smaller film thickness, respectively. The latter effect is attributed to a cross-interfacial coupling of excited electrons to phonons in the substrate.« less

Spectral ellipsometry as a method for characterization of nanosized films with ferromagnetic layers

NASA Astrophysics Data System (ADS)

Hashim, H.; Singkh, S. P.; Panina, L. V.; Pudonin, F. A.; Sherstnev, I. A.; Podgornaya, S. V.; Shpetnyi, I. A.; Beklemisheva, A. V.

2017-11-01

Nanosized films with ferromagnetic layers are widely used in nanoelectronics, sensor systems and telecommunications. Their properties may strongly differ from those of bulk materials that is on account of interfaces, intermediate layers and diffusion. In the present work, spectral ellipsometry and magnetooptical methods are adapted for characterization of the optical parameters and magnetization processes in two- and three-layer Cr/NiFe, Al/NiFe and Cr(Al)/Ge/NiFe films onto a sitall substrate for various thicknesses of Cr and Al layers. At a layer thickness below 20 nm, the complex refractive coefficients depend pronouncedly on the thickness. In two-layer films, remagnetization changes weakly over a thickness of the top layer, but the coercive force in three-layer films increases by more than twice upon remagnetization, while increasing the top layer thickness from 4 to 20 nm.

A New NIST Database for the Simulation of Electron Spectra for Surface Analysis (SESSA): Application to Angle-Resolved X-ray Photoelectron Spectroscopy of HfO2, ZrO2, HfSiO4, and ZrSiO4 Films on Silicon

NASA Astrophysics Data System (ADS)

Powell, C. J.; Smekal, W.; Werner, W. S. M.

2005-09-01

We describe a new NIST database for the Simulation of Electron Spectra for Surface Analysis (SESSA). This database provides data for the many parameters needed in quantitative Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS). In addition, AES and XPS spectra can be simulated for layered samples. The simulated spectra, for layer compositions and thicknesses specified by the user, can be compared with measured spectra. The layer compositions and thicknesses can then be adjusted to find maximum consistency between simulated and measured spectra. In this way, AES and XPS can provide more detailed characterization of multilayer thin-film materials. We report on the use of SESSA for determining the thicknesses of HfO2, ZrO2, HfSiO4, and ZrSiO4 films on Si by angle-resolved XPS. Practical effective attenuation lengths (EALs) have been computed from SESSA as a function of film thickness and photoelectron emission angle (i.e., to simulate the effects of tilting the sample). These EALs have been compared with similar values obtained from the NIST Electron Effective-Attenuation-Length Database (SRD 82). Generally good agreement was found between corresponding EAL values, but there were differences for film thicknesses less than the inelastic mean free path of the photoelectrons in the overlayer film. These differences are due to a simplifying approximation in the algorithm used to compute EALs in SRD 82. SESSA, with realistic cross sections for elastic and inelastic scattering in the film and substrate materials, is believed to provide more accurate EALs than SRD 82 for thin-film thickness measurements, particularly in applications where the film and substrate have different electron-scattering properties.

A New NIST Database for the Simulation of Electron Spectra for Surface Analysis (SESSA): Application to Angle-Resolved X-ray Photoelectron Spectroscopy of HfO2, ZrO2, HfSiO4, and ZrSiO4 Films on Silicon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Powell, C.J.; Smekal, W.; Werner, W.S.M.

2005-09-09

We describe a new NIST database for the Simulation of Electron Spectra for Surface Analysis (SESSA). This database provides data for the many parameters needed in quantitative Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS). In addition, AES and XPS spectra can be simulated for layered samples. The simulated spectra, for layer compositions and thicknesses specified by the user, can be compared with measured spectra. The layer compositions and thicknesses can then be adjusted to find maximum consistency between simulated and measured spectra. In this way, AES and XPS can provide more detailed characterization of multilayer thin-film materials. Wemore » report on the use of SESSA for determining the thicknesses of HfO2, ZrO2, HfSiO4, and ZrSiO4 films on Si by angle-resolved XPS. Practical effective attenuation lengths (EALs) have been computed from SESSA as a function of film thickness and photoelectron emission angle (i.e., to simulate the effects of tilting the sample). These EALs have been compared with similar values obtained from the NIST Electron Effective-Attenuation-Length Database (SRD 82). Generally good agreement was found between corresponding EAL values, but there were differences for film thicknesses less than the inelastic mean free path of the photoelectrons in the overlayer film. These differences are due to a simplifying approximation in the algorithm used to compute EALs in SRD 82. SESSA, with realistic cross sections for elastic and inelastic scattering in the film and substrate materials, is believed to provide more accurate EALs than SRD 82 for thin-film thickness measurements, particularly in applications where the film and substrate have different electron-scattering properties.« less

Quasi-optic millimeter-wave device application of liquid crystal material by using porous PMMA matrix

NASA Astrophysics Data System (ADS)

Nose, T.; Watanabe, Y.; Kon, A.; Ito, R.; Honma, M.

2018-02-01

Recently, millimeter-waves (MMWs) have become indispensable for application in next-generation high-speed wireless communication i.e., 5G, in addition to conventional applications such as in automobile collision avoidance radars and airport security inspection systems. Some manageable devices to control MMW propagation will be necessary with the development of this new technology field. We believe that liquid crystal (LC) devices are one of the major candidates for such applications because it is known that LC materials are excellent electro-optic materials. However, as the wavelength of MMWs is extremely longer than the optics region, extremely thick LC layers are necessary if we choose the quasioptic approach to attain LC MMW control devices. Therefore, we adopt a PDLC structure to attain the extremely thick LC layers by using porous (polymethyl methacrylate) PMMA materials, which can be easily obtained using a solvent consisting of a mixture of ethanol/water and a little heating. In this work, we focus on Fresnel lens, which is an important quasi-optic device for MMW application, to introduce a tunable property by using LC materials. Here, we adopt the thin film deposition method to obtain a porous PMMA matrix with the aim of obtaining final composite structure based on the Fresnel substrate. First, the fundamental material properties of porous PMMA are investigated to control the microscopic porous structure. Then, the LC-MMW Fresnel lens substrate is prepared using a 3D printer, and the fundamental MMW focusing properties of the prototype composite Fresnel structure are investigated.

Maskless Lithography Using Negative Photoresist Material: Impact of UV Laser Intensity on the Cured Line Width

NASA Astrophysics Data System (ADS)

Mohammed, Mohammed Ziauddin; Mourad, Abdel-Hamid I.; Khashan, Saud A.

2018-06-01

The application of maskless lithography technique on negative photoresist material is investigated in this study. The equipment used in this work is designed and built especially for maskless lithography applications. The UV laser of 405 nm wavelength with 0.85 Numerical Aperture is selected for direct laser writing. All the samples are prepared on a glass substrate. Samples are tested at different UV laser intensities and different stage velocities in order to study the impact on patterned line width. Three cases of spin coated layers of thickness 90 μm, 40 μm, and 28 μm on the substrate are studied. The experimental results show that line width has a generally increasing trend with intensity. However, a decreasing trend was observed for increasing velocity. The overall performance shows that the mr-DWL material is suitable for direct laser writing systems.

Maskless Lithography Using Negative Photoresist Material: Impact of UV Laser Intensity on the Cured Line Width

NASA Astrophysics Data System (ADS)

Mohammed, Mohammed Ziauddin; Mourad, Abdel-Hamid I.; Khashan, Saud A.

2018-04-01

The application of maskless lithography technique on negative photoresist material is investigated in this study. The equipment used in this work is designed and built especially for maskless lithography applications. The UV laser of 405 nm wavelength with 0.85 Numerical Aperture is selected for direct laser writing. All the samples are prepared on a glass substrate. Samples are tested at different UV laser intensities and different stage velocities in order to study the impact on patterned line width. Three cases of spin coated layers of thickness 90 μm, 40 μm, and 28 μm on the substrate are studied. The experimental results show that line width has a generally increasing trend with intensity. However, a decreasing trend was observed for increasing velocity. The overall performance shows that the mr-DWL material is suitable for direct laser writing systems.

MBE Growth of HgCdTe on Large-Area Si and CdZnTe Wafers for SWIR, MWIR and LWIR Detection

NASA Astrophysics Data System (ADS)

Reddy, M.; Peterson, J. M.; Lofgreen, D. D.; Franklin, J. A.; Vang, T.; Smith, E. P. G.; Wehner, J. G. A.; Kasai, I.; Bangs, J. W.; Johnson, S. M.

2008-09-01

Molecular beam epitaxy (MBE) growth of HgCdTe on large-size Si (211) and CdZnTe (211)B substrates is critical to meet the demands of extremely uniform and highly functional third-generation infrared (IR) focal-panel arrays (FPAs). We have described here the importance of wafer maps of HgCdTe thickness, composition, and the macrodefects across the wafer not only to qualify material properties against design specifications but also to diagnose and classify the MBE-growth-related issues on large-area wafers. The paper presents HgCdTe growth with exceptionally uniform composition and thickness and record low macrodefect density on large Si wafers up to 6-in in diameter for the detection of short-wave (SW), mid-wave (MW), and long-wave (LW) IR radiation. We have also proposed a cost-effective approach to use the growth of HgCdTe on low-cost Si substrates to isolate the growth- and substrate-related problems that one occasionally comes across with the CdZnTe substrates and tune the growth parameters such as growth rate, cutoff wavelength ( λ cutoff) and doping parameters before proceeding with the growth on costly large-area CdZnTe substrates. In this way, we demonstrated HgCdTe growth on large CdZnTe substrates of size 7 cm × 7 cm with excellent uniformity and low macrodefect density.

Terahertz Bandpass Frequency Selective Surfaces on Glass Substrates Using a Wet Micromachining Process

NASA Astrophysics Data System (ADS)

Ramzan, Mehrab; Khan, Talha Masood; Bolat, Sami; Nebioglu, Mehmet Ali; Altan, Hakan; Okyay, Ali Kemal; Topalli, Kagan

2017-08-01

This paper presents terahertz (THz) frequency selective surfaces (FSS) implemented on glass substrate using standard microfabrication techniques. These FSS structures are designed for frequencies around 0.8 THz. A fabrication process is proposed where a 100-μm-thick glass substrate is formed through the HF etching of a standard 500-μm-thick low cost glass wafer. Using this fabrication process, three separate robust designs consisting of single-layer FSS are investigated using high-frequency structural simulator (HFSS). Based on the simulation results, the first design consists of a circular ring slot in a square metallic structure on top of a 100-μm-thick Pyrex glass substrate with 70% transmission bandwidth of approximately 0.07 THz, which remains nearly constant till 30° angle of incidence. The second design consists of a tripole structure on top of a 100-μm-thick Pyrex glass substrate with 65% transmission bandwidth of 0.035 THz, which remains nearly constant till 30° angle of incidence. The third structure consists of a triangular ring slot in a square metal on top of a 100-μm-thick Pyrex glass substrate with 70% transmission bandwidth of 0.051 THz, which remains nearly constant up to 20° angle of incidence. These designs show that the reflections from samples can be reduced compared to the conventional sample holders used in THz spectroscopy applications, by using single layer FSS structures manufactured through a relatively simple fabrication process. Practically, these structures are achieved on a fabricated 285-μm-thick glass substrate. Taking into account the losses and discrepancies in the substrate thickness, the measured results are in good agreement with the electromagnetic simulations.

X-ray Fluorescence Spectroscopy Study of Coating Thickness and Base Metal Composition

NASA Technical Reports Server (NTRS)

Rolin, T. D.; Leszczuk, Y.

2008-01-01

For electrical, electronic, and electromechanical (EEE) parts to be approved for space use, they must be able to meet safety standards approved by NASA. A fast, reliable, and precise method is needed to make sure these standards are met. Many EEE parts are coated in gold (Au) and nickel (Ni), and the thickness coating is crucial to a part s performance. A nondestructive method that is efficient in measuring coating thickness is x-ray fluorescence (XRF) spectroscopy. The XRF spectrometer is a machine designed to measure layer thickness and composition of single or multilayered samples. By understanding the limitations in the collection of the data by this method, accurate composition and thickness measurements can be obtained for samples with Au and Ni coatings. To understand the limitations of data found, measurements were taken with the XRF spectrometer and compared to true values of standard reference materials (SRM) that were National Institute of Standards and Technology (NIST) traceable. For every sample, six different parameters were varied to understand measurement error: coating/substrate combination, number of layers, counting interval, collimator size, coating thickness, and test area location. Each measurement was taken in accordance with standards set by the American Society for Testing and Materials (ASTM) International Standard B 568.

Thickness dependence of structural and piezoelectric properties of epitaxial Pb(Zr0.52Ti0.48)O3 films on Si and SrTiO3 substrates

NASA Astrophysics Data System (ADS)

Kim, D. M.; Eom, C. B.; Nagarajan, V.; Ouyang, J.; Ramesh, R.; Vaithyanathan, V.; Schlom, D. G.

2006-04-01

We report the structural and longitudinal piezoelectric responses (d33) of epitaxial Pb(Zr0.52Ti0.48)O3 (PZT) films on (001) SrTiO3 and Si substrates in the thickness range of 40nm -4μm. With increasing film thickness the tetragonality of PZT was reduced. The increase in d33 value with increasing film thicknesses was attributed to the reduction of substrate constraints and softening of PZT due to reduced tetragonality. The d33 values of PZT films on Si substrates (˜330pm/V) are higher than those on SrTiO3 substrates (˜200pm /V). The epitaxial PZT films on silicon will lead to the fabrication of high performance piezoelectric microelectromechanical devices.

Screen printed Y and Bi-based superconductors

NASA Technical Reports Server (NTRS)

Haertling, Gene H.; Hsi, Chi-Shiung

1992-01-01

High T(sub c) superconducting thick film was prepared by screen printing process. Y-based (YBa2Cu3O(7 - x)) superconducting thick films were printed on 211/Al2O3, SNT/Al2O3, and YSZ substrates. Because of poor adhesion of the superconducting thick films to 211/Al2O3 and SNT/Al2O3 substrates, relatively low T(sub c) and J(sub c) values were obtained from the films printed on these substrates. Critical temperatures of YBa2Cu3O(7 - x) thick films deposited on 211/Al2O3 and SNT/Al2O3 substrates were about 80 K. The critical current densities of these films were less than 2 A/cm(exp 2). Higher T(sub c) and J(sub c) films were printed on the YSZ substrates; T(sub c) = 86.4 K and J(sub c) = 50.4 A/cm(exp 2). Multiple lead samples were also prepared on the YSZ substrates. These showed lower T(sub c) and J(sub c) values than plain samples. The heat treatment conditions of the multiple lead samples are still under investigation. Bi-based superconductor thick films have been obtained so far. Improving the superconducting properties of the BSCCO screen printed thick films will be emphasized in future work.

Quantitative Raman spectrum and reliable thickness identification for atomic layers on insulating substrates.

PubMed

Li, Song-Lin; Miyazaki, Hisao; Song, Haisheng; Kuramochi, Hiromi; Nakaharai, Shu; Tsukagoshi, Kazuhito

2012-08-28

We demonstrate the possibility in quantifying the Raman intensities for both specimen and substrate layers in a common stacked experimental configuration and, consequently, propose a general and rapid thickness identification technique for atomic-scale layers on dielectric substrates. Unprecedentedly wide-range Raman data for atomically flat MoS(2) flakes are collected to compare with theoretical models. We reveal that all intensity features can be accurately captured when including optical interference effect. Surprisingly, we find that even freely suspended chalcogenide few-layer flakes have a stronger Raman response than that from the bulk phase. Importantly, despite the oscillating intensity of specimen spectrum versus thickness, the substrate weighted spectral intensity becomes monotonic. Combined with its sensitivity to specimen thickness, we suggest this quantity can be used to rapidly determine the accurate thickness for atomic layers.

A multiple reflection model for the investigation of infrared transmission of a graphene/substrate system

NASA Astrophysics Data System (ADS)

Zhang, Jie; Ding, Lan; Liang, Changneng; Xiao, Yiming; Xu, Wen

2017-11-01

We develop a multiple reflection model (MRM) for the examination of infrared transmission properties of a graphene/substrate system. The incident angle and the multiple reflection beams in the substrate with finite thickness are taken into consideration. The model can be applied to predict the optical responses of graphene/substrate systems or to extract the real part of the optical conductance of graphene from the experimental measurement. As an example, we calculate the relative transmittance of graphene/quartz and graphene/sapphire systems by using MRM and provide an experimental verification in the near-infrared range. The measured results show good agreement with the calculated ones. Our method can be easily extended to accurately and non-invasively identify the layer numbers of other 2D materials, and assess the quality of them.

High mobility back-gated InAs/GaSb double quantum well grown on GaSb substrate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nguyen, Binh-Minh, E-mail: mbnguyen@hrl.com, E-mail: MSokolich@hrl.com; Yi, Wei; Noah, Ramsey

2015-01-19

We report a backgated InAs/GaSb double quantum well device grown on GaSb substrate. The use of the native substrate allows for high materials quality with electron mobility in excess of 500 000 cm{sup 2}/Vs at sheet charge density of 8 × 10{sup 11} cm{sup −2} and approaching 100 000 cm{sup 2}/Vs near the charge neutrality point. Lattice matching between the quantum well structure and the substrate eliminates the need for a thick buffer, enabling large back gate capacitance and efficient coupling with the conduction channels in the quantum wells. As a result, quantum Hall effects are observed in both electron and hole regimes across the hybridizationmore » gap.« less

A 3D Lattice Modelling Study of Drying Shrinkage Damage in Concrete Repair Systems

PubMed Central

Luković, Mladena; Šavija, Branko; Schlangen, Erik; Ye, Guang; van Breugel, Klaas

2016-01-01

Differential shrinkage between repair material and concrete substrate is considered to be the main cause of premature failure of repair systems. The magnitude of induced stresses depends on many factors, for example the degree of restraint, moisture gradients caused by curing and drying conditions, type of repair material, etc. Numerical simulations combined with experimental observations can be of great use when determining the influence of these parameters on the performance of repair systems. In this work, a lattice type model was used to simulate first the moisture transport inside a repair system and then the resulting damage as a function of time. 3D simulations were performed, and damage patterns were qualitatively verified with experimental results and cracking tendencies in different brittle and ductile materials. The influence of substrate surface preparation, bond strength between the two materials, and thickness of the repair material were investigated. Benefits of using a specially tailored fibre reinforced material, namely strain hardening cementitious composite (SHCC), for controlling the damage development due to drying shrinkage in concrete repairs was also examined. PMID:28773696

A 3D Lattice Modelling Study of Drying Shrinkage Damage in Concrete Repair Systems.

PubMed

Luković, Mladena; Šavija, Branko; Schlangen, Erik; Ye, Guang; van Breugel, Klaas

2016-07-14

Differential shrinkage between repair material and concrete substrate is considered to be the main cause of premature failure of repair systems. The magnitude of induced stresses depends on many factors, for example the degree of restraint, moisture gradients caused by curing and drying conditions, type of repair material, etc. Numerical simulations combined with experimental observations can be of great use when determining the influence of these parameters on the performance of repair systems. In this work, a lattice type model was used to simulate first the moisture transport inside a repair system and then the resulting damage as a function of time. 3D simulations were performed, and damage patterns were qualitatively verified with experimental results and cracking tendencies in different brittle and ductile materials. The influence of substrate surface preparation, bond strength between the two materials, and thickness of the repair material were investigated. Benefits of using a specially tailored fibre reinforced material, namely strain hardening cementitious composite (SHCC), for controlling the damage development due to drying shrinkage in concrete repairs was also examined.

Transmissive metallic contact for amorphous silicon solar cells

DOEpatents

Madan, A.

1984-11-29

A transmissive metallic contact for amorphous silicon semiconductors includes a thin layer of metal, such as aluminum or other low work function metal, coated on the amorphous silicon with an antireflective layer coated on the metal. A transparent substrate, such as glass, is positioned on the light reflective layer. The metallic layer is preferably thin enough to transmit at least 50% of light incident thereon, yet thick enough to conduct electricity. The antireflection layer is preferably a transparent material that has a refractive index in the range of 1.8 to 2.2 and is approximately 550A to 600A thick.

Angular distribution of species in pulsed laser deposition of LaxCa1-xMnO3

NASA Astrophysics Data System (ADS)

Ojeda-G-P, Alejandro; Schneider, Christof W.; Döbeli, Max; Lippert, Thomas; Wokaun, Alexander

2015-05-01

The angular distribution of species from a La0.4Ca0.6MnO3 target irradiated with a 248 nm nanosecond pulsed laser was investigated by Rutherford backscattering spectrometry for four different Ar pressures. The film thickness angular distribution was also analyzed using profilometry. Depending on the background gas pressure, the target to substrate distance, and the angular location the film thickness and composition varies considerably. In particular the film composition could vary by up to 17% with respect to the composition of the target material.

Theoretical Study of the Oxidation Behavior of Precipitation Hardening Steel

NASA Astrophysics Data System (ADS)

Pistofidis, N.; Vourlias, G.; Psyllaki, P.; Chrissafis, K.

2010-01-01

The oxidation of precipitation hardening (PH) steels is a rather unexplored area. In the present work an attempt is made is made to estimate the kinetics of a PH steel. For this purpose specimens of the material under examination were isothermally heated at 850, 900 and 950° C for 15 hr. Kinetics was based on TGA results. During heating a thick scale is formed on the substrate surface, which is composed by different oxides. The layer close to the substrate is compact and as a result it impedes corrosion. The mathematical analysis of the collected data shows that the change of the mass of the substrate per unit area versus time is described by a parabolic law.

Reflectance of evaporated rhenium and tungsten films in the vacuum ultraviolet from 300 to 2000 A.

NASA Technical Reports Server (NTRS)

Cox, J. T.; Hass, G.; Ramsey, J. B.; Hunter, W. R.

1972-01-01

Discussion of the dependence of the reflectance of Re and W on the substrate temperature during deposition, film thickness, and aging during exposure to air. Re and W of 99.99% purity were evaporated with a 6-kW fine-focused electron gun and deposited on glass and fused quartz plates of various temperatures ranging from 40 to 500 C. With Re, films of highest reflectance were obtained by evaporation onto unheated substrates, whereas with W, heating of the substrate greatly increased the reflectance of the deposited films. For both metals, the reflectance losses during extended exposure to air remained rather small, indicating that the oxide films formed on both film materials at room temperature were very thin.

Dip coating process: Silicon sheet growth development for the large-area silicon sheet task of the low-cost silicon solar array project

NASA Technical Reports Server (NTRS)

Heaps, J. D.; Maciolek, R. B.; Harrison, W. B.; Wolner, H. A.; Hendrickson, G.; Nelson, L. D.

1976-01-01

To date, an experimental dip-coating facility was constructed. Using this facility, relatively thin (1 mm) mullite and alumina substrates were successfully dip-coated with 2.5 - 3.0 ohm-cm, p-type silicon with areas of approximately 20 sq cm. The thickness and grain size of these coatings are influenced by the temperature of the melt and the rate at which the substrate is pulled from the melt. One mullite substrate had dendrite-like crystallites of the order of 1 mm wide and 1 to 2 cm long. Their axes were aligned along the direction of pulling. A large variety of substrate materials were purchased or developed enabling the program to commence a substrate definition evaluation. Due to the insulating nature of the substrate, the bottom layer of the p-n junction may have to be made via the top surface. The feasibility of accomplishing this was demonstrated using single crystal wafers.

Development of low modulus material for use in ceramic gas path seal applications

NASA Technical Reports Server (NTRS)

Eaton, H. E.; Novak, R. C.

1981-01-01

Three candidate materials were examined: Brunsbond (R) Pad; plasma sprayed porous NiCrAlY; and plasma sprayed low modulus microcracked zirconia. Evaluation consisted of mechanical, thermophysical, and oxidation resistance testing along with optical microscopy and a feasibility demonstration of attaching the material to a suitable substrate. The goals of the program were the following: feasibility of fastening or depositing the low modulus system onto a broad range of substrate alloys; feasibility of depositing or forming the low modulus system to a thickness of 0.19 cm to 0.38 cm; potential to attain a modulus of elasticity in the range of 3.4 to 6.9 GPa (0.5 to 1.0 MSI), and an ultimate strength of 17.2 MPa (2.5 ksi); suitable thermal conductivity; and static oxidation life of at least 1000 hours at 1311 K. The results of the program indicate that all three systems offer attractive properties as a strain isolator material.

Material growth and characterization for solid state devices

NASA Technical Reports Server (NTRS)

Stefanakos, E. K.; Collis, W. J.; Abul-Fadl, A.; Iyer, S.

1984-01-01

Manganese was used as the dopant for p-type InGaAs layers grown on semi-insulating (Fe-doped) and n-type (Sn-doped) InP substrates. Optical, electrical (Hall) and SIMS measurements were used to characterize the layers. Mn-diffusion into the substrate (during the growth of In GaAs) was observed only when Fe-doped substrates were used. Quaternary layers of two compositions corresponding to wavelengths (energy gaps) of approximated 1.52 micrometers were successfully grown at a constant temperature of 640 C and InP was grown in the temperature range of 640 C to 655 C. A study of the effect of pulses on the growth velocity of InP indicated no significant change as long as the average applied current was kept constant. A system for depositing films of Al2O3 by the pyrolysis of aluminum isopropoxide was designed and built. Deposited layers on Si were characterized with an ellipsometer and exhibited indices of refraction between 1.582 and 1.622 for films on the order of 3000 A thick. Undoped and p-type (Mn-doped) InGaAs epitaxial layers were also grown on Fe-doped InP substrates through windows in sputtered SiO2 (3200 A thick) layers.

Next Generation Ceramic Substrate Fabricated at Room Temperature.

PubMed

Kim, Yuna; Ahn, Cheol-Woo; Choi, Jong-Jin; Ryu, Jungho; Kim, Jong-Woo; Yoon, Woon-Ha; Park, Dong-Soo; Yoon, Seog-Young; Ma, Byungjin; Hahn, Byung-Dong

2017-07-26

A ceramic substrate must not only have an excellent thermal performance but also be thin, since the electronic devices have to become thin and small in the electronics industry of the next generation. In this manuscript, a thin ceramic substrate (thickness: 30-70 µm) is reported for the next generation ceramic substrate. It is fabricated by a new process [granule spray in vacuum (GSV)] which is a room temperature process. For the thin ceramic substrates, AlN GSV films are deposited on Al substrates and their electric/thermal properties are compared to those of the commercial ceramic substrates. The thermal resistance is significantly reduced by using AlN GSV films instead of AlN bulk-ceramics in thermal management systems. It is due to the removal of a thermal interface material which has low thermal conductivity. In particular, the dielectric strengths of AlN GSV films are much higher than those of AlN bulk-ceramics which are commercialized, approximately 5 times. Therefore, it can be expected that this GSV film is a next generation substrate in thermal management systems for the high power application.

Method of forming densified edge seals for fuel cell components

DOEpatents

DeCasperis, Anthony J.; Roethlein, Richard J.; Breault, Richard D.

1981-01-01

A porous fuel cell component, such as an electrode substrate, has a densified edge which forms an improved gas seal during operation when soaked with electrolyte. The edges are made from the same composition as the rest of the component and are made by compressing an increased thickness of this material along the edges during the fabrication process.

Role of Near Substrate and Bulk Polymer Morphology on Out-of-Plane Space-Charge Limited Hole Mobility.

PubMed

Turner, Johnathan; Gadisa, Abay

2016-12-07

Charge transport is a central issue in all types of organic electronic devices. In organic films, charge transport is crucially limited by film microstructure and the nature of the substrate/organic interface interactions. In this report, we discuss the influence of active layer thickness on space-charge limited hole transport in pristine polymer and polymer/fullerene bulk heterojunction thin films (∼15-300 nm) in a diode structure. According to the results, the out-of-plane hole mobility in pristine polymers is sensitive to the degree of polymer chain aggregation. Blending the polymers with a fullerene molecule does not change the trend of hole mobility if the polymer tends to make an amorphous structure. However, employing an aggregating polymer in a bulk heterojunction blend gives rise to a marked difference in charge carrier transport behavior compared to the pristine polymer and this difference is sensitive to active layer thickness. In aggregating polymer films, the thickness-dependent interchain interaction was found to have direct impact on hole mobility. The thickness-dependent mobility trend was found to correspond well with the trend of fill factors of corresponding bulk heterojunction solar cells. This investigation has a vital implication for material design and the development of efficient organic electronic devices, including solar cells and light-emitting diodes.

Thermal Spray Applications in Electronics and Sensors: Past, Present, and Future

NASA Astrophysics Data System (ADS)

Sampath, Sanjay

2010-09-01

Thermal spray has enjoyed unprecedented growth and has emerged as an innovative and multifaceted deposition technology. Thermal spray coatings are crucial to the enhanced utilization of various engineering systems. Industries, in recognition of thermal spray's versatility and economics, have introduced it into manufacturing environments. The majority of modern thermal spray applications are "passive" protective coatings, and they rarely perform an electronic function. The ability to consolidate dissimilar material multilayers without substrate thermal loading has long been considered a virtue for thick-film electronics. However, the complexity of understanding/controlling materials functions especially those resulting from rapid solidification and layered assemblage has stymied expansion into electronics. That situation is changing: enhancements in process/material science are allowing reconsideration for novel electronic/sensor devices. This review critically examines past efforts in terms of materials functionality from a device perspective, along with ongoing/future concepts addressing the aforementioned deficiencies. The analysis points to intriguing future possibilities for thermal spray technology in the world of thick-film sensors.

Structural properties of impact ices accreted on aircraft structures

NASA Technical Reports Server (NTRS)

Scavuzzo, R. J.; Chu, M. L.

1987-01-01

The structural properties of ice accretions formed on aircraft surfaces are studied. The overall objectives are to measure basic structural properties of impact ices and to develop finite element analytical procedures for use in the design of all deicing systems. The Icing Research Tunnel (IRT) was used to produce simulated natural ice accretion over a wide range of icing conditions. Two different test apparatus were used to measure each of the three basic mechanical properties: tensile, shear, and peeling. Data was obtained on both adhesive shear strength of impact ices and peeling forces for various icing conditions. The influences of various icing parameters such as tunnel air temperature and velocity, icing cloud drop size, material substrate, surface temperature at ice/material interface, and ice thickness were studied. A finite element analysis of the shear test apparatus was developed in order to gain more insight in the evaluation of the test data. A comparison with other investigators was made. The result shows that the adhesive shear strength of impact ice typically varies between 40 and 50 psi, with peak strength reaching 120 psi and is not dependent on the kind of substrate used, the thickness of accreted ice, and tunnel temperature below 4 C.

Strain engineering of atomic and electronic structures of few-monolayer-thick GaN

NASA Astrophysics Data System (ADS)

Kolobov, A. V.; Fons, P.; Saito, Y.; Tominaga, J.; Hyot, B.; André, B.

2017-07-01

Two-dimensional (2D) semiconductors possess the potential to ultimately minimize the size of devices and concomitantly drastically reduce the corresponding energy consumption. In addition, materials in their atomic-scale limit often possess properties different from their bulk counterparts paving the way to conceptually novel devices. While graphene and 2D transition-metal dichalcogenides remain the most studied materials, significant interest also exists in the fabrication of atomically thin structures from traditionally 3D semiconductors such as GaN. While in the monolayer limit GaN possesses a graphenelike structure and an indirect band gap, it was recently demonstrated that few-layer GaN acquires a Haeckelite structure in the direction of growth with an effectively direct gap. In this work, we demonstrate the possibility of strain engineering of the atomic and electronic structure of few-monolayer-thick GaN structures, which opens new avenues for their practical application in flexible nanoelectronics and nano-optoelectronics. Our simulations further suggest that due to the weak van der Waals-like interaction between a substrate and an overlayer, the use of a MoS2 substrate may be a promising route to fabricate few-monolayer Haeckelite GaN experimentally.

Tunneling interferometry and measurement of the thickness of ultrathin metallic Pb(111) films

NASA Astrophysics Data System (ADS)

Ustavshchikov, S. S.; Putilov, A. V.; Aladyshkin, A. Yu.

2017-10-01

Spectra of the differential tunneling conductivity for ultrathin lead films grown on Si(111) 7 × 7 single crystals with a thickness of 9 to 50 ML have been studied by low-temperature scanning tunneling microscopy and spectroscopy. The presence of local maxima of the tunneling conductivity is characteristic of such systems. The energies of maxima of the differential conductivity are determined by the spectrum of quantum-confined states of electrons in a metallic layer and, consequently, the local thickness of the layer. It has been shown that features of the microstructure of substrates, such as steps of monatomic height, structural defects, and inclusions of other materials covered with a lead layer, can be visualized by bias-modulation scanning tunneling spectroscopy.

25th anniversary article: CVD polymers: a new paradigm for surface modification and device fabrication.

PubMed

Coclite, Anna Maria; Howden, Rachel M; Borrelli, David C; Petruczok, Christy D; Yang, Rong; Yagüe, Jose Luis; Ugur, Asli; Chen, Nan; Lee, Sunghwan; Jo, Won Jun; Liu, Andong; Wang, Xiaoxue; Gleason, Karen K

2013-10-11

Well-adhered, conformal, thin (<100 nm) coatings can easily be obtained by chemical vapor deposition (CVD) for a variety of technological applications. Room temperature modification with functional polymers can be achieved on virtually any substrate: organic, inorganic, rigid, flexible, planar, three-dimensional, dense, or porous. In CVD polymerization, the monomer(s) are delivered to the surface through the vapor phase and then undergo simultaneous polymerization and thin film formation. By eliminating the need to dissolve macromolecules, CVD enables insoluble polymers to be coated and prevents solvent damage to the substrate. CVD film growth proceeds from the substrate up, allowing for interfacial engineering, real-time monitoring, and thickness control. Initiated-CVD shows successful results in terms of rationally designed micro- and nanoengineered materials to control molecular interactions at material surfaces. The success of oxidative-CVD is mainly demonstrated for the deposition of organic conducting and semiconducting polymers. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Preferentially oriented, High temperature superconductors by seeding and a method for their preparation

DOEpatents

Lee, Dominic F.; Kroeger, Donald M.; Goyal, Amit

2001-01-01

A multi-domained bulk REBa.sub.2 Cu.sub.3 O.sub.x with low-angle domain boundaries which resembles a quasi-single domained material and a method for producing the same comprising arranging multiple seeds, which can be small single crystals, single domained melt-textured REBa.sub.2 Cu.sub.3 O.sub.x pieces, textured substrates comprised of grains with low misorientation angles, or thick film REBa.sub.2 Cu.sub.3 O.sub.x deposited on such textured substrate, such seeds being tailored for various REBa.sub.2 Cu.sub.3 O.sub.x compounds, in specific pattern and relative seed orientations on a superconductor precursor material which may be placed in contact with a porous substrate so as to reduce the amount of liquid phase in the melt. Because seeds can be arranged in virtually any pattern, high quality REBa.sub.2 Cu.sub.3 O.sub.x elements of virtually unlimited size and complex geometry can be fabricated.

Method for preparing preferentially oriented, high temperature superconductors using solution reagents

DOEpatents

Lee, Dominic F.; Kroeger, Donald M.; Goyal, Amit

2002-01-01

A multi-domained bulk REBa.sub.2 CU.sub.3 O.sub.x with low-angle domain boundaries which resemble a quasi-single domained material and a method for producing the same comprising arranging multiple seeds, which can be small single crystals, single domained melt-textured REBa.sub.2 CU.sub.3 O.sub.x pieces, textured substrates comprises of grains with low misorientation angles, or thick film REBa.sub.2 CU.sub.3 O.sub.x deposited on such textured substrate, such seeds being tailored for various REBa.sub.2 CU.sub.3 O.sub.x compounds, in specific pattern and relative seed orientations on a superconductor precursor material which may be placed in contact with a porous substrate so as to reduce the amount of liquid phase in the melt. Because seeds can be arranged in virtually any pattern, high quality REBa.sub.2 CU.sub.3 O.sub.x elements of virtually unlimited size and complex geometry can be fabricated.

Catalytic nanoporous membranes

DOEpatents

Pellin, Michael J [Naperville, IL; Hryn, John N [Naperville, IL; Elam, Jeffrey W [Elmhurst, IL

2009-12-01

A nanoporous catalytic membrane which displays several unique features including pores which can go through the entire thickness of the membrane. The membrane has a higher catalytic and product selectivity than conventional catalysts. Anodic aluminum oxide (AAO) membranes serve as the catalyst substrate. This substrate is then subjected to Atomic Layer Deposition (ALD), which allows the controlled narrowing of the pores from 40 nm to 10 nm in the substrate by deposition of a preparatory material. Subsequent deposition of a catalytic layer on the inner surfaces of the pores reduces pore sizes to less than 10 nm and allows for a higher degree of reaction selectivity. The small pore sizes allow control over which molecules enter the pores, and the flow-through feature can allow for partial oxidation of reactant species as opposed to complete oxidation. A nanoporous separation membrane, produced by ALD is also provided for use in gaseous and liquid separations. The membrane has a high flow rate of material with 100% selectivity.

Interfacial characteristics and determination of cohesive and adhesive strength of plasma-coated hydroxyapatite via nanoindentation and microscratch techniques.

PubMed

McManamon, Colm; de Silva, Johann P; Power, John; Ramirez-Garcia, Sonia; Morris, Michael A; Cross, Graham L W

2014-09-30

We investigate the chemical composition and mechanical properties of plasma-deposited hydroxyapatite on grit-blasted Ti-6Al-4V coupons as models of typical prosthetic hip implants. Nanoindentation is used to extract the mechanical properties of the hydroxyapatite (HA) coating and to evaluate the behavior of the material as a function of distance from the interface. A microscratch technique was used to determine parameters of cohesive and adhesive failure of the material that are critical in determining the functionality of these biomedical devices. This delamination method has not been studied in detail before and is usually considered to be unsuitable because of the thickness of the HA and the roughness of the substrate. However, through cross-section analysis of the scratch test, we can determine the point at which the HA delaminates from the substrate. It was concluded that spallation occurs locally, and there is no evidence of gross spallation, indicating that the coating is well adhered to the substrate.

Polyethylene-Carbon Nanotube Composite Film Deposited by Cold Spray Technique

NASA Astrophysics Data System (ADS)

Ata, Nobuhisa; Ohtake, Naoto; Akasaka, Hiroki

2017-10-01

Carbon nanotubes (CNTs) are high-performance materials because of their superior electrical conductivity, thermal conductivity, and self-lubrication, and they have been studied for application to polymer composite materials as fillers. However, the methods of fabricating polymer composites with CNTs, such as injection molding, are too complicated for industrial applications. We propose a simple cold spray (CS) technique to obtain a polymer composite of polyethylene (PE) and CNTs. The composite films were deposited by CS on polypropylene and nano-porous structured aluminum substrates. The maximum thickness of the composite film was approximately 1 mm. Peaks at G and D bands were observed in the Raman spectra of the films. Scanning electron microscopy images of the film surface revealed that PE particles were melted by the acceleration gas and CNTs were attached with melted PE. The PE particles solidified after contact with the substrate. These results indicate that PE-CNT composite films were successfully deposited on polypropylene and nano-porous structured aluminum substrates by CS.

Engineering light outcoupling in 2D materials.

PubMed

Lien, Der-Hsien; Kang, Jeong Seuk; Amani, Matin; Chen, Kevin; Tosun, Mahmut; Wang, Hsin-Ping; Roy, Tania; Eggleston, Michael S; Wu, Ming C; Dubey, Madan; Lee, Si-Chen; He, Jr-Hau; Javey, Ali

2015-02-11

When light is incident on 2D transition metal dichalcogenides (TMDCs), it engages in multiple reflections within underlying substrates, producing interferences that lead to enhancement or attenuation of the incoming and outgoing strength of light. Here, we report a simple method to engineer the light outcoupling in semiconducting TMDCs by modulating their dielectric surroundings. We show that by modulating the thicknesses of underlying substrates and capping layers, the interference caused by substrate can significantly enhance the light absorption and emission of WSe2, resulting in a ∼11 times increase in Raman signal and a ∼30 times increase in the photoluminescence (PL) intensity of WSe2. On the basis of the interference model, we also propose a strategy to control the photonic and optoelectronic properties of thin-layer WSe2. This work demonstrates the utilization of outcoupling engineering in 2D materials and offers a new route toward the realization of novel optoelectronic devices, such as 2D LEDs and solar cells.

Fabrication of solid oxide fuel cell by electrochemical vapor deposition

DOEpatents

Riley, B.; Szreders, B.E.

1988-04-26

In a high temperature solid oxide fuel cell (SOFC), the deposition of an impervious high density thin layer of electrically conductive interconnector material, such as magnesium doped lanthanum chromite, and of an electrolyte material, such as yttria stabilized zirconia, onto a porous support/air electrode substrate surface is carried out at high temperatures (/approximately/1100/degree/ /minus/ 1300/degree/C) by a process of electrochemical vapor deposition. In this process, the mixed chlorides of the specific metals involved react in the gaseous state with water vapor resulting in the deposit of an impervious thin oxide layer on the support tube/air electrode substrate of between 20--50 microns in thickness. An internal heater, such as a heat pipe, is placed within the support tube/air electrode substrate and induces a uniform temperature profile therein so as to afford precise and uniform oxide deposition kinetics in an arrangement which is particularly adapted for large scale, commercial fabrication of SOFCs.

Emittance and absorptance of the National Aeronautics and Space Administration ceramic thermal barrier coating. [for gas turbine engine components

NASA Technical Reports Server (NTRS)

Liebert, C. H.

1978-01-01

The spectral emittance of a NASA developed zirconia ceramic thermal barrier coating system, consisting of a metal substrate, a layer of Ni-Cr-Al-Y bond material and a layer of yttria-stabilized zirconia ceramic material, is analyzed. The emittance, needed for evaluation of radiant heat loads on cooled coated gas turbine components, was measured over a range of temperatures that would be typical of its use on such components. Emittance data were obtained with a spectrometer, a reflectometer and a radiation pyrometer at a single bond coating thickness of 0.010 cm and at a ceramic coating thickness of 0-0.076 cm. The data were transformed into the hemispherical total emittance and were correlated to the ceramic coating thickness and temperature using multiple-regression curve-fitting techniques. The system was found to be highly reflective, and, consequently, capable of significantly reducing radiation heat loads on cooled gas turbine engine components.

Method and system using power modulation and velocity modulation producing sputtered thin films with sub-angstrom thickness uniformity or custom thickness gradients

DOEpatents

Montcalm, Claude [Livermore, CA; Folta, James Allen [Livermore, CA; Walton, Christopher Charles [Berkeley, CA

2003-12-23

A method and system for determining a source flux modulation recipe for achieving a selected thickness profile of a film to be deposited (e.g., with highly uniform or highly accurate custom graded thickness) over a flat or curved substrate (such as concave or convex optics) by exposing the substrate to a vapor deposition source operated with time-varying flux distribution as a function of time. Preferably, the source is operated with time-varying power applied thereto during each sweep of the substrate to achieve the time-varying flux distribution as a function of time. Preferably, the method includes the steps of measuring the source flux distribution (using a test piece held stationary while exposed to the source with the source operated at each of a number of different applied power levels), calculating a set of predicted film thickness profiles, each film thickness profile assuming the measured flux distribution and a different one of a set of source flux modulation recipes, and determining from the predicted film thickness profiles a source flux modulation recipe which is adequate to achieve a predetermined thickness profile. Aspects of the invention include a computer-implemented method employing a graphical user interface to facilitate convenient selection of an optimal or nearly optimal source flux modulation recipe to achieve a desired thickness profile on a substrate. The method enables precise modulation of the deposition flux to which a substrate is exposed to provide a desired coating thickness distribution.

Substrate-Influenced Thermo-Mechanical Fatigue of Copper Metallizations: Limits of Stoney’s Equation

PubMed Central

Bigl, Stephan; Wurster, Stefan; Cordill, Megan J.

2017-01-01

Rapid progress in the reduction of substrate thickness for silicon-based microelectronics leads to a significant reduction of the device bending stiffness and the need to address its implication for the thermo-mechanical fatigue behavior of metallization layers. Results on 5 µm thick Cu films reveal a strong substrate thickness-dependent microstructural evolution. Substrates with hs = 323 and 220 µm showed that the Cu microstructure exhibits accelerated grain growth and surface roughening. Moreover, curvature-strain data indicates that Stoney’s simplified curvature-stress relation is not valid for thin substrates with regard to the expected strains, but can be addressed using more sophisticated plate bending theories. PMID:29120407

Method of accurate thickness measurement of boron carbide coating on copper foil

DOEpatents

Lacy, Jeffrey L.; Regmi, Murari

2017-11-07

A method is disclosed of measuring the thickness of a thin coating on a substrate comprising dissolving the coating and substrate in a reagent and using the post-dissolution concentration of the coating in the reagent to calculate an effective thickness of the coating. The preferred method includes measuring non-conducting films on flexible and rough substrates, but other kinds of thin films can be measure by matching a reliable film-substrate dissolution technique. One preferred method includes determining the thickness of Boron Carbide films deposited on copper foil. The preferred method uses a standard technique known as inductively coupled plasma optical emission spectroscopy (ICPOES) to measure boron concentration in a liquid sample prepared by dissolving boron carbide films and the Copper substrates, preferably using a chemical etch known as ceric ammonium nitrate (CAN). Measured boron concentration values can then be calculated.

An unstructured mathematical model for growth of Pleurotus ostreatus on lignocellulosic material in solid-state fermentation systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sarikaya, A.; Ladisch, M.R.

1997-01-01

Inedible plant material, generated in a Controlled Ecological Life Support System (CELSS), should be recycled preferably by bioregenerative methods that utilize enzymes or micro-organisms. This material consists of hemicellulose, cellulose, and lignin with the lignin fraction representing a recalcitrant component that is not readily treated by enzymatic methods. Consequently, the white-rot fungus, Pleurotus ostreatus, is attractive since it effectively degrades lignin and produces edible mushrooms. This work describes an unstructured model for the growth of P. ostreatus in a solid-state fermentation system using lignocellulosic plant materials from Brassica napus (rapeseed) as a substrate at three different particle sizes. A logisticmore » function model based on area was found to fit the surface growth of the mycelium on the solid substrate with respect to time, whereas a model based on diameter, alone, did not fit the data as well. The difference between the two measures of growth was also evident for mycelial growth in a bioreactor designed to facilitate a slow flowrate of air through the 1.5 cm thick mat of lignocellulosic biomass particles. The result is consistent with the concept of competition of the mycelium for the substrate that surrounds it, rather than just substrate that is immediately available to single cells. This approach provides a quantitative measure of P. ostreatus growth on lignocellulosic biomass in a solid-state fermentation system. The experimental data show that the best growth is obtained for the largest particles (1 cm) of the lignocellulosic substrate. 13 refs., 6 figs., 2 tabs.« less

Nanometer-Scale Epitaxial Strain Release in Perovskite Heterostructures Using 'SrAlOx' Sliding Buffer Layers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bell, Christopher

2011-08-11

We demonstrate the strain release of LaAlO{sub 3} epitaxial film on SrTiO{sub 3} (001) by inserting ultra-thin 'SrAlO{sub x}' buffer layers. Although SrAlO{sub x} is not a perovskite, nor stable as a single phase in bulk, epitaxy stabilizes the perovskite structure up to a thickness of 2 unit cells (uc). At a critical thickness of 3 uc of SrAlO{sub x}, the interlayer acts as a sliding buffer layer, and abruptly relieves the lattice mismatch between the LaAlO{sub 3} filmand the SrTiO{sub 3} substrate, while maintaining crystallinity. This technique may provide a general approach for strain relaxation of perovskite film farmore » below the thermodynamic critical thickness. A central issue in heteroepitaxial filmgrowth is the inevitable difference in lattice constants between the filmand substrate. Due to this lattice mismatch, thin film are subjected to microstructural strain, which can have a significan effect on the filmproperties. This challenge is especially prominent in the rapidly developing fiel of oxide electronics, where much interest is focused on incorporating the emergent physical properties of oxides in devices. Although strain can be used to great effect to engineer unusual ground states, it is often deleterious for bulk first-orde phase transitions, which are suppressed by the strain and symmetry constraints of the substrate. While there are some reports discussing the control of the lattice mismatch in oxides using thick buffer layers, the materials choice, lattice-tunable range, and control of misfit dislocations are still limited. In this Letter, we report the fabrication of strain-relaxed LaAlO{sub 3} (LAO) thin film on SrTiO{sub 3} (STO) (001) using very thin 'SrAlO{sub x}' (SAO) buffer layers. Whereas for 1 or 2 pseudo-perovskite unit cells (uc) of SAO, the subsequent LAO filmis strained to the substrate, at a critical thickness of 3 uc the SAO interlayer abruptly relieves the lattice mismatch between the LAO and the STO, although maintaining the relative crystalline orientation between the filmand the substrate. For 4 uc or greater, the perovskite epitaxial template is lost and the LAO filmis amorphous. These results suggest that metastable interlayers can be used for strain release on the nanometer scale.« less

Improvement in surface conditions of electroplated Fe-Pt thick-film magnets

NASA Astrophysics Data System (ADS)

Yanai, T.; Honda, J.; Hamamura, R.; Omagari, Y.; Yamada, H.; Fujita, N.; Takashima, K.; Nakano, M.; Fukunaga, H.

2018-05-01

Fe-Pt thick-films were electroplated on Ta, Ti, Co, Ni, and Cu plates (substrates) using a direct current, and the surface morphology, the magnetic properties, and the crystal structure of the films were evaluated. The films plated on the Co, Ni, and Cu substrates showed much smooth surface compared with those for the Ta and Ti ones, and we confirmed that the Cu plate was the most attractive substrate due to very small cracks after an annealing for L10 ordering. High coercivity (>800 kA/m) for the Cu substrate is almost the same as that for our previous study in which we employed the Ta substrate, and we found that the Cu plate is a hopeful substrate to improve the surface conditions of electroplated Fe-Pt thick-film magnets.

Epitaxial Growth of Cadmium Telluride Films on Silicon and Indium Antimonide Substrates Using a Closed Hot Wall Epitaxy System

NASA Astrophysics Data System (ADS)

Kuo, Tien-Chuan

For many applications, such as infrared detector and high speed devices, we need high quality cadmium telluride (CdTe) films. To fabricate CdTe films we are using a home -built Closed Hot Wall Epitaxy system (CHWE). This system consists of two growth chambers, preheat chamber, substrate exchange load lock and ultra-high vacuum system. It can exchange the substrates without disturbing the vacuum environment and prevents the source materials from contamination. Two different substrate materials, Si and InSb, are used in this work. Deposition parameters were varied in order to determine the growth condition for obtaining good quality CdTe films. The characteristics of the films were investigated by Scanning Electron Microscope, X-ray diffractormeter and Auger Electron Spectroscope. The electrical properties of Al/CdTe/InSb MIS diodes are also examined. Experimental results show that the quality of the CdTe films on these two substrates are functions of the source and substrate temperatures. The surface of CdTe films grown on Si substrate are rougher than CdTe films grown on InSb substrate. X -ray patterns show that the crystal orientations of the CdTe films are, (100) and (111), similar to those of the substrates under optimum growth conditions. The CdTe film are stoichiometric based on the results of Auger survey. Electrical measurement also indicates that CdTe films grown on InSb substrates have very high purity and are insulator. The induced stresses due to the differences of lattice constant and thermal expansion coefficient between CdTe films and substrates were observed in CdTe films. The critical thickness of CdTe films on InSb substrates are measured by X-ray diffraction to be 2.63 um.

Influence of enamel composite thickness on value, chroma and translucency of a high and a nonhigh refractive index resin composite.

PubMed

Ferraris, Federico; Diamantopoulou, Sofia; Acunzo, Raffaele; Alcidi, Renato

2014-01-01

To evaluate the influence of thickness on the optical properties of two enamel shade composites, one with a high refractive index and one traditional. A medium value enamel shade was selected from the resin composites Enamel Plus HRi (UE2) and Enamel Plus HFO (GE2). Enamel Plus HRi is a high refractive index composite. Samples were fabricated in five different thicknesses: 0.3, 0.5, 1, 1.5 and 2 mm. Three specimens per material and thickness were fabricated. Three measurements per sample, over white, black and dentin composite background were generated with a spectrophotometer (Spectroshade Micro, MHT). Value, chroma, translucency and color differences (ΔE) of the specimens were calculated. RESULTS were analyzed by the Pearson correlation test, ANOVA and a post-hoc Tukey test. Increasing the thickness of the enamel layers decreased the translucency and the chroma of the substrate for both materials tested. For HRi the increase of the thickness resulted in an increase of the value, whereas for HFO it resulted in a reduction of the value. The two composites showed a significant difference in value for each thickness, but not in translucency and chroma. Color difference between them was perceptible in layers equal or higher than 0.5 mm. The high refractive index enamel (HRi) composite exhibits different optical behavior compared to the traditional one (HFO). HRi enamel composite behaves more like natural enamel as by increasing the thickness of the enamel layer, the value also increases.

Effect of Substrate and Process Parameters on the Gas-Substrate Convective Heat Transfer Coefficient During Cold Spraying

NASA Astrophysics Data System (ADS)

Mahdavi, Amirhossein; McDonald, André

2018-02-01

The final quality of cold-sprayed coatings can be significantly influenced by gas-substrate heat exchange, due to the dependence of the deposition efficiency of the particles on the substrate temperature distribution. In this study, the effect of the air temperature and pressure, as process parameters, and surface roughness and thickness, as substrate parameters, on the convective heat transfer coefficient of the impinging air jet was investigated. A low-pressure cold spraying unit was used to generate a compressed air jet that impinged on a flat substrate. A comprehensive mathematical model was developed and coupled with experimental data to estimate the heat transfer coefficient and the surface temperature of the substrate. The effect of the air total temperature and pressure on the heat transfer coefficient was studied. It was found that increasing the total pressure would increase the Nusselt number of the impinging air jet, while total temperature of the air jet had negligible effect on the Nusslet number. It was further found that increasing the roughness of the substrate enhanced the heat exchange between the impinging air jet and the substrate. As a result, higher surface temperatures on the rough substrate were measured. The study of the effect of the substrate thickness on the heat transfer coefficient showed that the Nusselt number that was predicted by the model was independent of the thickness of the substrate. The surface temperature profile, however, decreased in increasing radial distances from the stagnation point of the impinging jet as the thickness of the substrate increased. The results of the current study were aimed to inform on the influence and effect of substrate and process parameters on the gas-substrate heat exchange and the surface temperature of the substrate on the final quality of cold-sprayed coatings.

Strain-Engineered Nanomembrane Substrates for Si/SiGe Heterostructures

NASA Astrophysics Data System (ADS)

Sookchoo, Pornsatit

For Group IV materials, including silicon, germanium, and their alloys, although they are most widely used in the electronics industry, the development of photonic devices is hindered by indirect band gaps and large lattice mismatches. Thus, any heterostructures involving Si and Ge (4.17% lattice mismatch) are subject to plastic relaxation by dislocation formation in the heterolayers. These defects make many devices impossible and at minimum degrade the performance of those that are possible. Fabrication using elastic strain engineering in Si/SiGe nanomembranes (NMs) is an approach that is showing promise to overcome this limitation. A key advantage of such NM substrates over conventional bulk substrates is that they are relaxed elastically and therefore free of dislocations that occur in the conventional fabrication of SiGe substrates, which are transferred to the epilayers and roughen film interfaces. In this thesis, I use the strain engineering of NMs or NM stacks to fabricate substrates for the epitaxial growth of many repeating units of Si/SiGe heterostructure, known as a 'superlattice', by the elastic strain sharing of a few periods of the repeating unit of Si/SiGe heterolayers or a Si/SiGe/Si tri-layer structure. In both cases, the process begins with the epitaxial growth of Si/SiGe heterolayers on silicon-on-insulator (SOI), where each layer thickness is designed to stay below its kinetic critical thickness for the formation of dislocations. The heterostructure NMs are then released by etching of the SiO2 sacrificial layer in hydrofluoric acid. The resulting freestanding NMs are elastically relaxed by the sharing of strain between the heterolayers. The NMs can be bonded in-place to their host substrate or transferred to another host substrate for the subsequent growth of many periods of superlattice film. The magnitude of strain sharing in these freestanding NMs is influenced by their layer thicknesses and layer compositions. As illustrated in this dissertation, strain-engineering of such NMs can provide the enabling basis for improved Group IV optoelectronic devices.

Interface doping of conjugated organic films by means of diffusion of atomic components from the surfaces of semiconductors and of metal oxides.

PubMed

Komolov, A S; Akhremtchik, S N; Lazneva, E F

2011-08-15

The paper reports the results on the interface formation of 5-10 nm thick conjugated layers of Cu-phthalocyanine (CuPc) with a number of solid surfaces: polycrystalline Au, (SiO(2))n-Si, ZnO(0 0 0 1), Si(1 0 0), Ge(1 1 1), CdS(0 0 0 1) and GaAs(1 0 0). The results were obtained using Auger electron spectroscopy (AES) and low-energy target current electron spectroscopy (TCS). The organic overlayers were thermally deposited in situ in UHV onto substrate surfaces. The island-like organic deposits were excluded from the analysis so that only uniform organic deposits were considered. In the cases of polycrystalline Au, Si(1 0 0) and Ge(1 1 1) substrates the AES peaks of the substrate material attenuated down to the zero noise level upon the increase of the CuPc film thickness of 8-10 nm. The peaks corresponding to oxygen atoms in the case of SiO(2) substrate, and to atoms from the ZnO, GaAs and CdS substrates were clearly registered in the AES spectra of the 8-10 nm thick CuPc deposits. The relative concentration of the substrate atomic components diffused into the film was different from their relative concentration at the pure substrate surface. The concentration of the substrate dopant atoms in the CuPc film was estimated as one atom per one CuPc molecule. Using the target current electron spectroscopy, it was shown that the substrate atoms admixed in the CuPc film account for the appearance of a new peak in the density of unoccupied electronic states. Formation of intermediate TCS spectra until the CuPc deposit reaches 2-3 nm was observed in the cases of GaAs(1 0 0), ZnO(0 0 0 1), Ge(1 1 1) surfaces. The intermediate spectra show a less pronounced peak structure different from the one typical for the CuPc films. It was suggested that the intermediate layer was formed by the CuPc molecules fully or partially decomposed due to the interaction with the relatively reactive semiconductor surfaces. Copyright © 2010 Elsevier B.V. All rights reserved.

Friction force microscopy: a simple technique for identifying graphene on rough substrates and mapping the orientation of graphene grains on copper

NASA Astrophysics Data System (ADS)

Marsden, A. J.; Phillips, M.; Wilson, N. R.

2013-06-01

At a single atom thick, it is challenging to distinguish graphene from its substrate using conventional techniques. In this paper we show that friction force microscopy (FFM) is a simple and quick technique for identifying graphene on a range of samples, from growth substrates to rough insulators. We show that FFM is particularly effective for characterizing graphene grown on copper where it can correlate the graphene growth to the three-dimensional surface topography. Atomic lattice stick-slip friction is readily resolved and enables the crystallographic orientation of the graphene to be mapped nondestructively, reproducibly and at high resolution. We expect FFM to be similarly effective for studying graphene growth on other metal/locally crystalline substrates, including SiC, and for studying growth of other two-dimensional materials such as molybdenum disulfide and hexagonal boron nitride.

Flexible microstrip antenna based on carbon nanotubes/(ethylene-octene copolymer) thin composite layer deposited on PET substrate

NASA Astrophysics Data System (ADS)

Matyas, J.; Olejnik, R.; Slobodian, P.

2017-12-01

A most of portable devices, such as mobile phones, tablets, uses antennas made of cupper. In this paper we demonstrate possible use of electrically conductive polymer composite material for such antenna application. Here we describe the method of preparation and properties of the carbon nanotubes (CNTs)/(ethylene-octene copolymer) as flexible microstrip antenna. Carbon nanotubes dispersion in (ethylene-octene copolymer) toluene solution was prepared by ultrasound finally coating PET substrate by method of dip-coating. Main advantages of PET substrate are low weight and also flexibility. The final size of flexible microstrip antenna was 5 x 50 mm with thickness of 0.48 mm (PET substrate 0.25 mm) with the weight of only 0.402 g. Antenna operates at three frequencies 1.66 GHz (-6.51 dB), 2.3 GHz (-13 dB) and 2.98 GHz (-33.59 dB).

High-field magnets using high-critical-temperature superconducting thin films

DOEpatents

Mitlitsky, F.; Hoard, R.W.

1994-05-10

High-field magnets fabricated from high-critical-temperature superconducting ceramic (HTSC) thin films which can generate fields greater than 4 Tesla are disclosed. The high-field magnets are made of stackable disk-shaped substrates coated with HTSC thin films, and involves maximizing the critical current density, superconducting film thickness, number of superconducting layers per substrate, substrate diameter, and number of substrates while minimizing substrate thickness. The HTSC thin films are deposited on one or both sides of the substrates in a spiral configuration with variable line widths to increase the field. 4 figures.

High-field magnets using high-critical-temperature superconducting thin films

DOEpatents

Mitlitsky, Fred; Hoard, Ronald W.

1994-01-01

High-field magnets fabricated from high-critical-temperature superconducting ceramic (HTSC) thin films which can generate fields greater than 4 Tesla. The high-field magnets are made of stackable disk-shaped substrates coated with HTSC thin films, and involves maximizing the critical current density, superconducting film thickness, number of superconducting layers per substrate, substrate diameter, and number of substrates while minimizing substrate thickness. The HTSC thin films are deposited on one or both sides of the substrates in a spiral configuration with variable line widths to increase the field.

Thickness sensing of hMSCs on collagen gel directs stem cell fate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Leong, Wen Shing; Tay, Chor Yong; Yu, Haiyang

Research highlights: {yields} hMSCs appeared to sense thin collagen gel (130 {mu}m) with higher effective modulus as compared to thick gel (1440 {mu}m). {yields} Control of collagen gel thickness can modulate cellular behavior, even stem cell fate (neuronal vs. Quiescent). {yields} Distinct cellular behavior of hMSCs on thin and thick collagen gel suggests long range interaction of hMSCs with collagen gel. -- Abstract: Mechanically compliant substrate provides crucial biomechanical cues for multipotent stem cells to regulate cellular fates such as differentiation, proliferation and maintenance of their phenotype. Effective modulus of which cells sense is not only determined by intrinsic mechanicalmore » properties of the substrate, but also the thickness of substrate. From our study, it was found that interference from underlying rigid support at hundreds of microns away could induce significant cellular response. Human mesenchymal stem cells (hMSCs) were cultured on compliant biological gel, collagen type I, of different thickness but identical ECM composition and local stiffness. The cells sensed the thin gel (130 {mu}m) as having a higher effective modulus than the thick gel (1440 {mu}m) and this was reflected in their changes in morphology, actin fibers structure, proliferation and tissue specific gene expression. Commitment into neuronal lineage was observed on the thin gel only. Conversely, the thick gel (1440 {mu}m) was found to act like a substrate with lower effective modulus that inhibited actin fiber polymerization. Stem cells on the thick substrate did not express tissue specific genes and remained at their quiescent state. This study highlighted the need to consider not only the local modulus but also the thickness of biopolymer gel coating during modulation of cellular responses.« less

Thermal Effusivity Determination of Metallic Films of Nanometric Thickness by the Electrical Micropulse Method

NASA Astrophysics Data System (ADS)

Lugo, J. M.; Oliva, A. I.

2017-02-01

The thermal effusivity of gold, aluminum, and copper thin films of nanometric thickness (20 nm to 200 nm) was investigated in terms of the films' thickness. The metallic thin films were deposited onto glass substrates by thermal evaporation, and the thermal effusivity was estimated by using experimental parameters such as the specific heat, thermal conductivity, and thermal diffusivity values obtained at room conditions. The specific heat, thermal conductivity, and thermal diffusivity values of the metallic thin films are determined with a methodology based on the behavior of the thermal profiles of the films when electrical pulses of few microseconds are applied at room conditions. For all the investigated materials, the thermal effusivity decreases with decreased thickness. The thermal effusivity values estimated by the presented methodology are consistent with other reported values obtained under vacuum conditions and more elaborated methodologies.

Template assisted strain tuning and phase stabilization in epitaxial BiFeO3 thin films

NASA Astrophysics Data System (ADS)

Saj Mohan M., M.; Ramadurai, Ranjith

2018-04-01

Strain engineering is a key to develop novel properties in functional materials. We report a strain mediated phase stabilization and epitaxial growth of bismuth ferrite(BiFeO3) thin films on LaAlO3 (LAO) substrates. The strain in the epitaxial layer is controlled by controlling the thickness of bottom electrode where the thickness of the BFO is kept constant. The thickness of La0.7Sr0.3MnO3(LSMO) template layer was optimized to grow completely strained tetragonal, tetragonal/rhombohedral mixed phase and fully relaxed rhombohedral phase of BFO layers. The results were confirmed with coupled-θ-2θ scan, and small area reciprocal space mapping. The piezoelectric d33 (˜ 45-48 pm/V) coefficient of the mixed phase was relatively larger than the strained tetragonal and relaxed rhombohedral phase for a given thickness.

High-voltage SPM oxidation of ZrN: materials for multiscale applications

NASA Astrophysics Data System (ADS)

Farkas, N.; Comer, J. R.; Zhang, G.; Evans, E. A.; Ramsier, R. D.; Dagata, J. A.

2005-02-01

Scanning probe microscope (SPM) oxidation was used to form zirconium oxide features on 200 nm thick ZrN films. The features exhibit rapid yet controlled growth kinetics, even in contact mode with 70 V dc applied between the probe tip and substrate. The features grown for times longer than 10 s are higher than 200 nm, and reach more than 1000 nm in height after 300 s. Long-time oxidation experiments and selective etching of the oxides and nitrides lead us to propose that as the oxidation reaches the silicon substrate, delamination occurs with the simultaneous formation of a thin layer of new material at the ZrN/Si interface. High-voltage oxide growth on ZrN is fast and sustainable, and the robust oxide features are promising candidates for multiscale (nanometre-to-micrometre) applications.

High-conductance low-voltage organic thin film transistor with locally rearranged poly(3-hexylthiophene) domain by current annealing on plastic substrate

NASA Astrophysics Data System (ADS)

Pei, Zingway; Tsai, Hsing-Wang; Lai, Hsin-Cheng

2016-02-01

The organic material based thin film transistors (TFTs) are attractive for flexible optoelectronics applications due to the ability of lager area fabrication by solution and low temperature process on plastic substrate. Recently, the research of organic TFT focus on low operation voltage and high output current to achieve a low power organic logic circuit for optoelectronic device,such as e-paper or OLED displayer. To obtain low voltage and high output current, high gate capacitance and high channel mobility are key factors. The well-arranged polymer chain by a high temperature postannealing, leading enhancement conductivity of polymer film was a general method. However, the thermal annealing applying heat for all device on the substrate and may not applicable to plastic substrate. Therefore, in this work, the low operation voltage and high output current of polymer TFTs was demonstrated by locally electrical bias annealing. The poly(styrene-comethyl methacrylate) (PS-r-PMMA) with ultra-thin thickness is used as gate dielectric that the thickness is controlled by thermal treatment after spin coated on organic electrode. In electrical bias-annealing process, the PS-r- PMMA is acted a heating layer. After electrical bias-annealing, the polymer TFTs obtain high channel mobility at low voltage that lead high output current by a locally annealing of P3HT film. In the future, the locally electrical biasannealing method could be applied on plastic substrate for flexible optoelectronic application.

Controlling the optical properties of monocrystalline 3C-SiC heteroepitaxially grown on silicon at low temperatures

NASA Astrophysics Data System (ADS)

Colston, Gerard; Myronov, Maksym

2017-11-01

Cubic silicon carbide (3C-SiC) offers an alternative wide bandgap semiconductor to conventional materials such as hexagonal silicon carbide (4H-SiC) or gallium nitride (GaN) for the detection of UV light and can offer a closely lattice matched virtual substrate for subsequent GaN heteroepitaxy. As 3C-SiC can be heteroepitaxially grown on silicon (Si) substrates its optical properties can be manipulated by controlling the thickness and doping concentrations. The optical properties of 3C-SiC epilayers have been characterized by measuring the transmission of light through suspended membranes. Decreasing the thickness of the 3C-SiC epilayers is shown to shift the absorbance edge to lower wavelengths, a result of the indirect bandgap nature of silicon carbide. This property, among others, can be exploited to fabricate very low-cost, tuneable 3C-SiC based UV photodetectors. This study investigates the effect of thickness and doping concentration on the optical properties of 3C-SiC epilayers grown at low temperatures by a standard Si based growth process. The results demonstrate the potential photonic applications of 3C-SiC and its heterogeneous integration into the Si industry.

Correlation of Critical Temperatures and Electrical Properties in Titanium Films

NASA Astrophysics Data System (ADS)

Gandini, C.; Lacquaniti, V.; Monticone, E.; Portesi, C.; Rajteri, M.; Rastello, M. L.; Pasca, E.; Ventura, G.

Recently transition-edge sensors (TES) have obtained an increasing interest as light detectors due to their high energy resolution and broadband response. Titanium (Ti), with transition temperature up to 0.5 K, is among the suitable materials for TES application. In this work we investigate Ti films obtained from two materials of different purity deposited by e-gun on silicon nitride. Films with different thickness and deposition substrate temperature have been measured. Critical temperatures, electrical resistivities and structural properties obtained from x-ray are related to each other.

Enhanced third harmonic generation from the epsilon-near-zero modes of ultrathin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Luk, Ting S.; De Ceglia, Domenico; Liu, Sheng

We demonstrate, through our experimentation, efficient third harmonic generation from an indium tin oxide nanofilm (λ/42 thick) on a glass substrate for a pump wavelength of 1.4 μm. A conversion efficiency of 3.3 × 10 -6 is achieved by exploiting the field enhancement properties of the epsilon-near-zero mode with an enhancement factor of 200. Furthermore, this nanoscale frequency conversion method is applicable to other plasmonic materials and reststrahlen materials in proximity of the longitudinal optical phonon frequencies.

Inhibition of linear absorption in opaque materials using phase-locked harmonic generation.

PubMed

Centini, Marco; Roppo, Vito; Fazio, Eugenio; Pettazzi, Federico; Sibilia, Concita; Haus, Joseph W; Foreman, John V; Akozbek, Neset; Bloemer, Mark J; Scalora, Michael

2008-09-12

We theoretically predict and experimentally demonstrate inhibition of linear absorption for phase and group velocity mismatched second- and third-harmonic generation in strongly absorbing materials, GaAs, in particular, at frequencies above the absorption edge. A 100-fs pump pulse tuned to 1300 nm generates 650 and 435 nm second- and third-harmonic pulses that propagate across a 450-microm-thick GaAs substrate without being absorbed. We attribute this to a phase-locking mechanism that causes the pump to trap the harmonics and to impress on them its dispersive properties.

Enhanced third harmonic generation from the epsilon-near-zero modes of ultrathin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Luk, Ting S., E-mail: tsluk@sandia.gov; Liu, Sheng; Campione, Salvatore

We experimentally demonstrate efficient third harmonic generation from an indium tin oxide nanofilm (λ/42 thick) on a glass substrate for a pump wavelength of 1.4 μm. A conversion efficiency of 3.3 × 10{sup −6} is achieved by exploiting the field enhancement properties of the epsilon-near-zero mode with an enhancement factor of 200. This nanoscale frequency conversion method is applicable to other plasmonic materials and reststrahlen materials in proximity of the longitudinal optical phonon frequencies.

Method for fabrication of crack-free ceramic dielectric films

DOEpatents

Ma, Beihai; Narayanan, Manoj; Balachandran, Uthamalingam; Chao, Sheng; Liu, Shanshan

2016-05-31

The invention provides a process for forming crack-free dielectric films on a substrate. The process comprises the application of a dielectric precursor layer of a thickness from about 0.3 .mu.m to about 1.0 .mu.m to a substrate. The deposition is followed by low temperature heat pretreatment, prepyrolysis, pyrolysis and crystallization step for each layer. The deposition, heat pretreatment, prepyrolysis, pyrolysis and crystallization are repeated until the dielectric film forms an overall thickness of from about 1.5 .mu.m to about 20.0 .mu.m and providing a final crystallization treatment to form a thick dielectric film. The process provides a thick crack-free dielectric film on a substrate, the dielectric forming a dense thick crack-free dielectric having an overall dielectric thickness of from about 1.5 .mu.m to about 20.0 .mu.m.

Method for fabrication of crack-free ceramic dielectric films

DOEpatents

Ma, Beihai; Balachandran, Uthamalingam; Chao, Sheng; Liu, Shanshan; Narayanan, Manoj

2014-02-11

The invention provides a process for forming crack-free dielectric films on a substrate. The process comprise the application of a dielectric precursor layer of a thickness from about 0.3 .mu.m to about 1.0 .mu.m to a substrate. The deposition is followed by low temperature heat pretreatment, prepyrolysis, pyrolysis and crystallization step for each layer. The deposition, heat pretreatment, prepyrolysis, pyrolysis and crystallization are repeated until the dielectric film forms an overall thickness of from about 1.5 .mu.m to about 20.0 .mu.m and providing a final crystallization treatment to form a thick dielectric film. Also provided was a thick crack-free dielectric film on a substrate, the dielectric forming a dense thick crack-free dielectric having an overall dielectric thickness of from about 1.5 .mu.m to about 20.0 .mu.m.

Thickness-dependent surface energies of few-layered arsenene and antimonene films in α and β phases

NASA Astrophysics Data System (ADS)

Zhao, N.; Zhu, Y. F.; Jiang, Q.

2018-07-01

Group V elemental few-layered materials with semiconducting electronic properties are emerging as promising 2D layered materials. Since the layered configurations need substrate for device fabrications, their surface energy values could decide their properties. Here, we have performed a systematic density functional theory (DFT) investigation on the surface energies of arsenene and antimonene films as the function of thickness. The results show that the surface energy of β phase increases with increased layered numbers and converges to a constant value at about five layers, while the surface energy of α phase is size-independent. Since the surface energies of both α and β phase are similar, there is the existence possibility of α phase. Those could give references for future manufacture of arsenene and antimonene nano-devices.

Development of RF sputtered chromium oxide coating for wear application

NASA Technical Reports Server (NTRS)

Bhushan, B.

1979-01-01

The radio frequency sputtering technique was used to deposite a hard refractory, chromium oxide coating on an Inconel X-750 foil 0.1 mm thick. Optimized sputtering parameters for a smooth and adherent coating were found to be as follows: target-to-substrate spacing, 41.3 mm; argon pressure, 5-10 mTorr; total power to the sputtering module, 400 W (voltage at the target, 1600 V), and a water-cooled substrate. The coating on the annealed foil was more adherent than that on the heat-treated foil. Substrate biasing during the sputter deposition of Cr2O3 adversely affected adherence by removing naturally occurring interfacial oxide layers. The deposited coatings were amorphous and oxygen deficient. Since amorphous materials are extremely hard, the structure was considered to be desirable.

Pattern interpolation in thin films of lamellar, symmetric copolymers on nano-patterned substrates

NASA Astrophysics Data System (ADS)

Detcheverry, Francois; Nagpal, Umang; Liu, Guoliang; Nealey, Paul; de Pablo, Juan

2009-03-01

A molecular model of block copolymer systems is used to conduct a systematic study of the morphologies that arise when thin films of symmetric, lamellar forming block copolymer materials are deposited on nanopatterned surfaces. Over 500 distinct cases are considered. It is found that, in general, three distinct morphologies can arise depending on the strength of the substrate-polymer interactions, the film thickness, and the period of the substrate pattern. The relative stability of those morphologies is determined by direct calculation of the free energy differences. The dynamic propensity of those morphologies to emerge is examined by careful analysis of simulated trajectories. The results of this systematic study are used to interpret recent experimental data for films of polystyrene-PMMA copolymers on chemically nanopatterned surfaces.

High performance x-ray anti-scatter grid

DOEpatents

Logan, Clinton M.

1995-01-01

An x-ray anti-scatter grid for x-ray imaging, particularly for screening mammography, and method for fabricating same, x-rays incident along a direct path pass through a grid composed of a plurality of parallel or crossed openings, microchannels, grooves, or slots etched in a substrate, such as silicon, having the walls of the microchannels or slots coated with a high opacity material, such as gold, while x-rays incident at angels with respect to the slots of the grid, arising from scatter, are blocked. The thickness of the substrate is dependent on the specific application of the grid, whereby a substrate of the grid for mammography would be thinner than one for chest radiology. Instead of coating the walls of the slots, such could be filed with an appropriate liquid, such as mercury.

Deposition of Lanthanum Strontium Cobalt Ferrite (LSCF) Using Suspension Plasma Spraying for Oxygen Transport Membrane Applications

NASA Astrophysics Data System (ADS)

Fan, E. S. C.; Kesler, O.

2015-08-01

Suspension plasma spray deposition was utilized to fabricate dense lanthanum strontium cobalt ferrite oxygen separation membranes (OSMs) on porous metal substrates for mechanical support. The as-sprayed membranes had negligible and/or reversible material decomposition. At the longer stand-off distance (80 mm), smooth and dense membranes could be manufactured using a plasma with power below approximately 81 kW. Moreover, a membrane of 55 μm was observed to have very low gas leakage rates desirable for OSM applications. This thickness could potentially be decreased further to improve oxygen diffusion by using metal substrates with finer surface pores.

Transmission and reflection studies of thin films in the vacuum ultraviolet

NASA Technical Reports Server (NTRS)

Peterson, Lennart R.

1989-01-01

Both the transmittance and reflectance of 2 mm thick MgF2 substrates and of thin films of BaF2, CaF2, LaF3, MgF2, Al2O3, HfO2, and SiO2 deposited on these substrates were measured for the wavelength range 120 nm to 230 nm. Results for BaF2, LaF2 and MgF2 show promise as being good materials from which interference filters can be made. The software and related hardware needed to take large amounts of data automatically in future measurements of the transmittance and reflectance was developed.

Preparation of c-axis perpendicularly oriented ultra-thin L10-FePt films on MgO and VN underlayers

NASA Astrophysics Data System (ADS)

Futamoto, Masaaki; Shimizu, Tomoki; Ohtake, Mitsuru

2018-05-01

Ultra-thin L10-FePt films of 2 nm average thickness are prepared on (001) oriented MgO and VN underlayers epitaxially grown on base substrate of SrTiO3(001) single crystal. Detailed cross-sectional structures are observed by high-resolution transmission electron microscopy. Continuous L10-FePt(001) thin films with very flat surface are prepared on VN(001) underlayer whereas the films prepared on MgO(001) underlayer consist of isolated L10-FePt(001) crystal islands. Presence of misfit dislocation and lattice bending in L10-FePt material is reducing the effective lattice mismatch with respect to the underlayer to be less than 0.5 %. Formation of very flat and continuous FePt layer on VN underlayer is due to the large surface energy of VN material where de-wetting of FePt material at high temperature annealing process is suppressed under a force balance between the surface and interface energies of FePt and VN materials. An employment of underlayer or substrate material with the lattice constant and the surface energy larger than those of L10-FePt is important for the preparation of very thin FePt epitaxial thin continuous film with the c-axis controlled to be perpendicular to the substrate surface.

Unsupported single-atom-thick copper oxide monolayers

NASA Astrophysics Data System (ADS)

Yin, Kuibo; Zhang, Yu-Yang; Zhou, Yilong; Sun, Litao; Chisholm, Matthew F.; Pantelides, Sokrates T.; Zhou, Wu

2017-03-01

Oxide monolayers may present unique opportunities because of the great diversity of properties of these materials in bulk form. However, reports on oxide monolayers are still limited. Here we report the formation of single-atom-thick copper oxide layers with a square lattice both in graphene pores and on graphene substrates using aberration-corrected scanning transmission electron microscopy. First-principles calculations find that CuO is energetically stable and its calculated lattice spacing matches well with the measured value. Furthermore, free-standing copper oxide monolayers are predicted to be semiconductors with band gaps ˜3 eV. The new wide-bandgap single-atom-thick copper oxide monolayers usher a new frontier to study the highly diverse family of two-dimensional oxides and explore their properties and their potential for new applications.

Method and system for producing sputtered thin films with sub-angstrom thickness uniformity or custom thickness gradients

DOEpatents

Folta, James A.; Montcalm, Claude; Walton, Christopher

2003-01-01

A method and system for producing a thin film with highly uniform (or highly accurate custom graded) thickness on a flat or graded substrate (such as concave or convex optics), by sweeping the substrate across a vapor deposition source with controlled (and generally, time-varying) velocity. In preferred embodiments, the method includes the steps of measuring the source flux distribution (using a test piece that is held stationary while exposed to the source), calculating a set of predicted film thickness profiles, each film thickness profile assuming the measured flux distribution and a different one of a set of sweep velocity modulation recipes, and determining from the predicted film thickness profiles a sweep velocity modulation recipe which is adequate to achieve a predetermined thickness profile. Aspects of the invention include a practical method of accurately measuring source flux distribution, and a computer-implemented method employing a graphical user interface to facilitate convenient selection of an optimal or nearly optimal sweep velocity modulation recipe to achieve a desired thickness profile on a substrate. Preferably, the computer implements an algorithm in which many sweep velocity function parameters (for example, the speed at which each substrate spins about its center as it sweeps across the source) can be varied or set to zero.

Electrical, structural and optical properties of tellurium thin films on silicon substrate

NASA Astrophysics Data System (ADS)

Arora, Swati; Vijay, Y. K.

2018-05-01

Tellurium (Te) thin films of various thicknesses (200nm, 275nm, 350nm & 500nm) were prepared on Silicon (Si) using thermal evaporation at vacuum of 10-5 torr. It is observed that the resistivity decreases exponentially with the Increases Temperature. A direct band gap between 0.368 eV to 0.395 eV is obtained at different temperatures with Four Probe Method which shows that when we increase the thickness of material the band gap will exponentially decreases. Samples were analysed through X-ray diffraction and atomic force microscopy to attain complete and reliable micro structural in order.

Transport in ultrathin gold films decorated with magnetic Gd atoms

NASA Astrophysics Data System (ADS)

Alemani, Micol; Helgren, Erik; Hugel, Addison; Hellman, Frances

2008-03-01

We have performed four-probe transport measurements of ultrathin Au films decorated with Gd ad-atoms. The samples were prepared by quench condensation, i.e., sequential evaporation on a cryogenically cooled substrate under UHV conditions while monitoring the film thickness and resistance. Electrically continuous Au films at thickness of about 2 mono-layers of material are grown on an amorphous Ge wetting layer. The quench condensation method provides a sensitive control on the sample growth process, allowing us to tune the morphological and electrical configuration of the system. The ultrathin gold films develop from an insulating to a metallic state as a function of film thickness. The temperature dependence of the Au conductivity for different thickness is studied. It evolves from hopping transport for the insulating films, to a ln T dependence for thicker films. For gold films in the insulating regime we found a decreasing resistance by adding Gd. This is in agreement with a decreasing tunneling barrier height between metallic atoms. The Gd magnetic moments are randomly oriented for isolated atoms. This magnetic disorder leads to scattering of the charge carriers and a reduced conductivity compared to nonmagnetic materials.

Die attach dimension and material on thermal conductivity study for high power COB LED

NASA Astrophysics Data System (ADS)

Sarukunaselan, K.; Ong, N. R.; Sauli, Z.; Mahmed, N.; Kirtsaeng, S.; Sakuntasathien, S.; Suppiah, S.; Alcain, J. B.; Retnasamy, V.

2017-09-01

High power LED began to gain popularity in the semiconductor market due to its efficiency and luminance. Nonetheless, along with the increased in efficiency, there was an increased in the junction temperature too. The alleviating junction temperature is undesirable since the performances and lifetime will be degraded over time. Therefore, it is crucial to solve this thermal problem by maximizing the heat dissipation to the ambience. Improvising the die attach (DA) layer would be the best option because this layer is sandwiched between the chip (heat source) and the substrate (channel to the ambient). In this paper, the impact of thickness and thermal conductivity onto the junction temperature and Von Mises stress is analyzed. Results obtained showed that the junction temperature is directly proportional to the thickness but the stress was inversely proportional to the thickness of the DA. The thermal conductivity of the materials did affect the junction temperature as there was not much changes once the thermal conductivity reached 20W/mK. However, no significant changes were observed on the Von Mises stress caused by the thermal conductivity. Material with the second highest thermal conductivity had the lowest stress, whereas the highest conductivity material had the highest stress value at 20 µm. Overall, silver sinter provided the best thermal dissipation compared to the other materials.

Role of Morphological Structure, Doping, and Coating of Different Materials in the Sensing Characteristics of Humidity Sensors

PubMed Central

Tripathy, Ashis; Pramanik, Sumit; Cho, Jongman; Santhosh, Jayasree; Osman, Noor Azuan Abu

2014-01-01

The humidity sensing characteristics of different sensing materials are important properties in order to monitor different products or events in a wide range of industrial sectors, research and development laboratories as well as daily life. The primary aim of this study is to compare the sensing characteristics, including impedance or resistance, capacitance, hysteresis, recovery and response times, and stability with respect to relative humidity, frequency, and temperature, of different materials. Various materials, including ceramics, semiconductors, and polymers, used for sensing relative humidity have been reviewed. Correlations of the different electrical characteristics of different doped sensor materials as the most unique feature of a material have been noted. The electrical properties of different sensor materials are found to change significantly with the morphological changes, doping concentration of different materials and film thickness of the substrate. Various applications and scopes are pointed out in the review article. We extensively reviewed almost all main kinds of relative humidity sensors and how their electrical characteristics vary with different doping concentrations, film thickness and basic sensing materials. Based on statistical tests, the zinc oxide-based sensing material is best for humidity sensor design since it shows extremely low hysteresis loss, minimum response and recovery times and excellent stability. PMID:25256110

Epitaxially grown BaM hexaferrite films having uniaxial axis in the film plane for self-biased devices

PubMed Central

Zhang, Xiaozhi; Meng, Siqin; Song, Dongsheng; Zhang, Yao; Yue, Zhenxing; Harris, Vincent G.

2017-01-01

Barium hexaferrite (BaM) films with in-plane c-axis orientation are promising and technically important materials for self-biased magnetic microwave devices. In this work, highly oriented BaM films with different thickness and an in-plane easy axis (c-axis) of magnetization were grown on a-plane single-crystal sapphire substrates by direct current magnetron sputtering. A procedure involving seed layers, layer-by-layer annealing was adopted to reduce the substrate-induced strains and allow for the growth of thick (~3.44 μm) films. The epitaxial growth of the BaM film on sapphire was revealed by high-resolution transmission electron microscopy with dislocations being observed at the film-substrate interface. The orientation was also verified by X-ray diffraction and more notably, polarized Raman scattering. The magnetic properties and ferromagnetic resonant frequencies were experimentally characterized by a vibrating sample magnetometry and a frequency-swept ferromagnetic resonant flip-chip technique, respectively. The micron-thick BaM films exhibited a large remanence ratio of 0.92 along in-plane easy axis and a small one of 0.09 for the in-plane hard axis loop measurement. The FMR frequency was 50.3 GHz at zero field and reached 57.9 GHz under a magnetic field of 3 kOe, indicating that the epitaxial BaM films with strong self-biased behaviors have good electromagnetic properties in millimeter-wave range. PMID:28276492

The influence of alloying on the phase formation sequence of ultra-thin nickel silicide films and on the inheritance of texture

NASA Astrophysics Data System (ADS)

Geenen, F. A.; Solano, E.; Jordan-Sweet, J.; Lavoie, C.; Mocuta, C.; Detavernier, C.

2018-05-01

The controlled formation of silicide materials is an ongoing challenge to facilitate the electrical contact of Si-based transistors. Due to the ongoing miniaturisation of the transistor, the silicide is trending to ever-thinner thickness's. The corresponding increase in surface-to-volume ratio emphasises the importance of low-energetic interfaces. Intriguingly, the thickness reduction of nickel silicides results in an abrupt change in phase sequence. This paper investigates the sequence of the silicides phases and their preferential orientation with respect to the Si(001) substrate, for both "thin" (i.e., 9 nm) and "ultra-thin" (i.e., 3 nm) Ni films. Furthermore, as the addition of ternary elements is often considered in order to tailor the silicides' properties, additives of Al, Co, and Pt are also included in this study. Our results show that the first silicide formed is epitaxial θ-Ni2Si, regardless of initial thickness or alloyed composition. The transformations towards subsequent silicides are changed through the additive elements, which can be understood through solubility arguments and classical nucleation theory. The crystalline alignment of the formed silicides with the substrate significantly differs through alloying. The observed textures of sequential silicides could be linked through texture inheritance. Our study illustrates the nucleation of a new phase drive to reduce the interfacial energy at the silicide-substrate interface as well as at the interface with the silicide which is being consumed for these sub-10 nm thin films.

Optical characterization of Jerusalem cross-shaped nanoaperture antenna arrays

NASA Astrophysics Data System (ADS)

Turkmen, Mustafa; Aslan, Ekin; Aslan, Erdem

2014-03-01

Recent advances in nanofabrication and computational electromagnetic design techniques have enabled the realization of metallic nanostructures in different shapes and sizes with adjustable resonance frequencies. To date, many metamaterial designs in various geometries with the used of different materials have been presented for the applications of surface plasmons, cloaking, biosensing, and frequency selective surfaces1-5. Surface plasmons which are collective electron oscillations on metal surfaces ensure that plasmonic nanoantennas can be used in many applications like biosensing at infrared (IR) and visible regions. The nanostructure that we introduce has a unit cell that consists of Jerusalem crossshaped nanoaperture on a gold layer, which is standing on suspended SiNx, Si or glass membranes. The proposed nanoaperture antenna array has a regular and stable spectral response. In this study, we present sensitivity of the resonance characteristics of Jerusalem cross-shaped nanoaperture antenna arrays to the changes in substrate parameters and metal thickness. We demonstrate that resonance frequency values can be adjusted by changing the thicknesses and types of the dielectric substrate and the metallic layer. Numerical calculations on spectral response of the nanoantenna array are performed by using Finite Difference Time Domain (FDTD) method6. The results of the simulations specify that resonance frequencies, the reflectance and transmittance values at resonances, and the band gap vary by the change of substrate parameters and metal thicknesses. These variations is a sign of that the proposed nanoantenna can be employed for sensing applications.

Epitaxially grown BaM hexaferrite films having uniaxial axis in the film plane for self-biased devices.

PubMed

Zhang, Xiaozhi; Meng, Siqin; Song, Dongsheng; Zhang, Yao; Yue, Zhenxing; Harris, Vincent G

2017-03-09

Barium hexaferrite (BaM) films with in-plane c-axis orientation are promising and technically important materials for self-biased magnetic microwave devices. In this work, highly oriented BaM films with different thickness and an in-plane easy axis (c-axis) of magnetization were grown on a-plane single-crystal sapphire substrates by direct current magnetron sputtering. A procedure involving seed layers, layer-by-layer annealing was adopted to reduce the substrate-induced strains and allow for the growth of thick (~3.44 μm) films. The epitaxial growth of the BaM film on sapphire was revealed by high-resolution transmission electron microscopy with dislocations being observed at the film-substrate interface. The orientation was also verified by X-ray diffraction and more notably, polarized Raman scattering. The magnetic properties and ferromagnetic resonant frequencies were experimentally characterized by a vibrating sample magnetometry and a frequency-swept ferromagnetic resonant flip-chip technique, respectively. The micron-thick BaM films exhibited a large remanence ratio of 0.92 along in-plane easy axis and a small one of 0.09 for the in-plane hard axis loop measurement. The FMR frequency was 50.3 GHz at zero field and reached 57.9 GHz under a magnetic field of 3 kOe, indicating that the epitaxial BaM films with strong self-biased behaviors have good electromagnetic properties in millimeter-wave range.

Distributed fiber optic sensor-enhanced detection and prediction of shrinkage-induced delamination of ultra-high-performance concrete overlay

NASA Astrophysics Data System (ADS)

Bao, Yi; Valipour, Mahdi; Meng, Weina; Khayat, Kamal H.; Chen, Genda

2017-08-01

This study develops a delamination detection system for smart ultra-high-performance concrete (UHPC) overlays using a fully distributed fiber optic sensor. Three 450 mm (length) × 200 mm (width) × 25 mm (thickness) UHPC overlays were cast over an existing 200 mm thick concrete substrate. The initiation and propagation of delamination due to early-age shrinkage of the UHPC overlay were detected as sudden increases and their extension in spatial distribution of shrinkage-induced strains measured from the sensor based on pulse pre-pump Brillouin optical time domain analysis. The distributed sensor is demonstrated effective in detecting delamination openings from microns to hundreds of microns. A three-dimensional finite element model with experimental material properties is proposed to understand the complete delamination process measured from the distributed sensor. The model is validated using the distributed sensor data. The finite element model with cohesive elements for the overlay-substrate interface can predict the complete delamination process.

Photon energy conversion by near-zero permittivity nonlinear materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Luk, Ting S.; Sinclair, Michael B.; Campione, Salvatore

Efficient harmonic light generation can be achieved with ultrathin films by coupling an incident pump wave to an epsilon-near-zero (ENZ) mode of the thin film. As an example, efficient third harmonic generation from an indium tin oxide nanofilm (.lamda./42 thick) on a glass substrate for a pump wavelength of 1.4 .mu.m was demonstrated. A conversion efficiency of 3.3.times.10.sup.-6 was achieved by exploiting the field enhancement properties of the ENZ mode with an enhancement factor of 200. This nanoscale frequency conversion method is applicable to other plasmonic materials and reststrahlen materials in proximity of the longitudinal optical phonon frequencies.

Characterization of Thin Walled Mo Tubing produced by FBCVD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Beaux, Miles Frank; Usov, Igor Olegovich

2016-01-21

The goal of this report is to delineate the results of material characterization performed on Mo tubing produced via the fluidized bed chemical vapor deposition (FBCVD) method. Scanning electron microscopy (SEM) imaging reveals that small randomly oriented grains are achieved in the Mo deposition, but do not persist throughout the entire thickness of the material. Energy dispersive spectroscopy (EDS) reveals the Mo tubes contain residual chlorine and oxygen. EDS measurements on the tube surfaces separated from glass and quartz substrates reveal substrate material adhered to this surface. X-ray diffraction (XRD) revealed the presence of carbon contaminant in the form ofmore » Mo 2C and oxygen in the form of MoO 2. Combustion infrared detection (CID) and inert gas fusion (IGF) performed at Luvak Inc. was used to quantify weight percentages of oxygen and carbon in the tubes produced. Hardness value of the FBCVD Mo was found to be comparable to low carbon arc cast molybdenum.« less

Carbon Nanotubes Blended Hydroxyapatite Ethanol Sensor

NASA Astrophysics Data System (ADS)

Anjum, S. R.; Khairnar, R. S.

2016-12-01

Nano crystals of Hydroxyapatite (HAp) were synthesized by a wet chemical precipitation method. The nano composite materials were developed by doping various weight concentrations of carbon nanotubes in HAp, followed by characterization using scanning electron microscopy, and X-ray diffraction. Thick films of these materials were prepared by using screen printing technique. The ethanol sensing properties of these nano crystals and nano composite films were investigated by two probe electrical method. The gas sensing features such as operating temperature, response and recovery time, maximum gas detection limit, etc. were studied, since these parameters are of prime importance for sensor. The results revealed that at room temperature, the composite materials exhibited improved sensing performance towards 100 ppm ethanol with fast response times. It also showed shorter recovery time with higher vapor uptake capacity. The ethanol adsorption processes on doped and undoped substrates can be explained by surface chemical reactions as well as providing the possible adsorption models. The novelty of this work lies in developing reusable sensor substrates for room temperature sensing.

Preferential orientation of NV defects in CVD diamond films grown on (113)-oriented substrates

NASA Astrophysics Data System (ADS)

Lesik, M.; Plays, T.; Tallaire, A.; Achard, J.; Brinza, O.; William, L.; Chipaux, M.; Toraille, L.; Debuisschert, T.; Gicquel, A.; Roch, J. F.; Jacques, V.

2015-06-01

Thick CVD diamond layers were successfully grown on (113)-oriented substrates. They exhibited smooth surface morphologies and a crystalline quality comparable to (100) electronic grade material, and much better than (111)-grown layers. High growth rates (15-50 {\\mu}m/h) were obtained while nitrogen doping could be achieved in a fairly wide range without seriously imparting crystalline quality. Electron spin resonance measurements were carried out to determine NV centers orientation and concluded that one specific orientation has an occurrence probability of 73 % when (100)-grown layers show an equal distribution in the 4 possible directions. A spin coherence time of around 270 {\\mu}s was measured which is equivalent to that reported for material with similar isotopic purity. Although a higher degree of preferential orientation was achieved with (111)-grown layers (almost 100 %), the ease of growth and post-processing of the (113) orientation make it a potentially useful material for magnetometry or other quantum mechanical applications.

X-ray lithography using holographic images

DOEpatents

Howells, M.S.; Jacobsen, C.

1997-03-18

Methods for forming X-ray images having 0.25 {micro}m minimum line widths on X-ray sensitive material are presented. A holographic image of a desired circuit pattern is projected onto a wafer or other image-receiving substrate to allow recording of the desired image in photoresist material. In one embodiment, the method uses on-axis transmission and provides a high flux X-ray source having modest monochromaticity and coherence requirements. A layer of light-sensitive photoresist material on a wafer with a selected surface is provided to receive the image(s). The hologram has variable optical thickness and variable associated optical phase angle and amplitude attenuation for transmission of the X-rays. A second embodiment uses off-axis holography. The wafer receives the holographic image by grazing incidence reflection from a hologram printed on a flat metal or other highly reflecting surface or substrate. In this second embodiment, an X-ray beam with a high degree of monochromaticity and spatial coherence is required. 15 figs.

X-ray lithography using holographic images

DOEpatents

Howells, Malcolm S.; Jacobsen, Chris

1997-01-01

Methods for forming X-ray images having 0.25 .mu.m minimum line widths on X-ray sensitive material are presented. A holgraphic image of a desired circuit pattern is projected onto a wafer or other image-receiving substrate to allow recording of the desired image in photoresist material. In one embodiment, the method uses on-axis transmission and provides a high flux X-ray source having modest monochromaticity and coherence requirements. A layer of light-sensitive photoresist material on a wafer with a selected surface is provided to receive the image(s). The hologram has variable optical thickness and variable associated optical phase angle and amplitude attenuation for transmission of the X-rays. A second embodiment uses off-axis holography. The wafer receives the holographic image by grazing incidence reflection from a hologram printed on a flat metal or other highly reflecting surface or substrate. In this second embodiment, an X-ray beam with a high degree of monochromaticity and spatial coherence is required.

Effect of substrate thickness on ejection of phenylalanine molecules adsorbed on free-standing graphene bombarded by 10 keV C60

NASA Astrophysics Data System (ADS)

Golunski, M.; Verkhoturov, S. V.; Verkhoturov, D. S.; Schweikert, E. A.; Postawa, Z.

2017-02-01

Molecular dynamics computer simulations have been employed to investigate the effect of substrate thickness on the ejection mechanism of phenylalanine molecules deposited on free-standing graphene. The system is bombarded from the graphene side by 10 keV C60 projectiles at normal incidence and the ejected particles are collected both in transmission and reflection directions. It has been found that the ejection mechanism depends on the substrate thickness. At thin substrates mostly organic fragments are ejected by direct collisions between projectile atoms and adsorbed molecules. At thicker substrates interaction between deforming topmost graphene sheet and adsorbed molecules becomes more important. As this process is gentle and directionally correlated, it leads predominantly to ejection of intact molecules. The implications of the results to a novel analytical approach in Secondary Ion Mass Spectrometry based on ultrathin free-standing graphene substrates and a transmission geometry are discussed.

AC calorimetry of H2O at pressures up to 9 GPa in diamond anvil cells

NASA Astrophysics Data System (ADS)

Geballe, Zachary M.; Struzhkin, Viktor V.

2017-06-01

If successfully developed, calorimetry at tens of GPa of pressure could help characterize phase transitions in materials such as high-pressure minerals, metals, and molecular solids. Here, we extend alternating-current calorimetry to 9 GPa and 300 K in a diamond anvil cell and use it to study phase transitions in H2O. In particular, water is loaded into the sample chambers of diamond-cells, along with thin metal heaters (1 μm-thick platinum or 20 nm-thick gold on a glass substrate) that drive high-frequency temperature oscillations (20 Hz to 600 kHz; 1 to 10 K). The heaters also act as thermometers via the third-harmonic technique, yielding calorimetric data on (1) heat conduction to the diamonds and (2) heat transport into substrate and sample. Using this method during temperature cycles from 300 to 200 K, we document melting, freezing, and proton ordering and disordering transitions of H2O at 0 to 9 GPa, and characterize changes in thermal conductivity and heat capacity across these transitions. The technique and analysis pave the way for calorimetry experiments on any non-metal at pressures up to ˜100 GPa, provided a thin layer (several μm-thick) of thermal insulation supports a metallic thin-film (tens of nm thick) Joule-heater attached to low contact resistance leads inside the sample chamber of a diamond-cell.

Substrate Oxide Layer Thickness Optimization for a Dual-Width Plasmonic Grating for Surface-Enhanced Raman Spectroscopy (SERS) Biosensor Applications

PubMed Central

Bauman, Stephen J.; Brawley, Zachary T.; Darweesh, Ahmad A.; Herzog, Joseph B.

2017-01-01

This work investigates a new design for a plasmonic SERS biosensor via computational electromagnetic models. It utilizes a dual-width plasmonic grating design, which has two different metallic widths per grating period. These types of plasmonic gratings have shown larger optical enhancement than standard single-width gratings. The new structures have additional increased enhancement when the spacing between the metal decreases to sub-10 nm dimensions. This work integrates an oxide layer to improve the enhancement even further by carefully studying the effects of the substrate oxide thickness on the enhancement and reports ideal substrate parameters. The combined effects of varying the substrate and the grating geometry are studied to fully optimize the device’s enhancement for SERS biosensing and other plasmonic applications. The work reports the ideal widths and substrate thickness for both a standard and a dual-width plasmonic grating SERS biosensor. The ideal geometry, comprising a dual-width grating structure atop an optimal SiO2 layer thickness, improves the enhancement by 800%, as compared to non-optimized structures with a single-width grating and a non-optimal oxide thickness. PMID:28665308

Vapor deposition on doublet airfoil substrates: Control of coating thickness and microstructure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rodgers, Theron M.; Zhao, Hengbei; Wadley, Haydn N. G., E-mail: haydn@virginia.edu

Gas jet assisted vapor deposition processes for depositing coatings are conducted at higher pressures than conventional physical vapor deposition methods, and have shown promise for coating complex shaped substrates including those with non-line-of-sight (NLS) regions on their surface. These regions typically receive vapor atoms at a lower rate and with a wider incident angular distribution than substrate regions in line-of-sight (LS) of the vapor source. To investigate the coating of such substrates, the thickness and microstructure variation along the inner (curved) surfaces of a model doublet airfoil containing both LS and NLS regions has been investigated. Results from atomistic simulationsmore » and experiments confirm that the coating's thickness is thinner in flux-shadowed regions than in other regions for all the coating processes investigated. They also indicated that the coatings columnar microstructure and pore volume fraction vary with surface location through the LS to NLS transition zone. A substrate rotation strategy for optimizing the thickness over the entire doublet airfoil surface was investigated, and led to the identification of a process that resulted in only small variation of coating thickness, columnar growth angle, and pore volume fraction on all doublet airfoil surfaces.« less

Method for fabrication of crack-free ceramic dielectric films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ma, Beihai; Narayanan, Manoj; Balachandran, Uthamalingam

The invention provides a process for forming crack-free dielectric films on a substrate. The process comprises the application of a dielectric precursor layer of a thickness from about 0.3 .mu.m to about 1.0 .mu.m to a substrate. The deposition is followed by low temperature heat pretreatment, prepyrolysis, pyrolysis and crystallization step for each layer. The deposition, heat pretreatment, prepyrolysis, pyrolysis and crystallization are repeated until the dielectric film forms an overall thickness of from about 1.5 .mu.m to about 20.0 .mu.m and providing a final crystallization treatment to form a thick dielectric film. The process provides a thick crack-free dielectricmore » film on a substrate, the dielectric forming a dense thick crack-free dielectric having an overall dielectric thickness of from about 1.5 .mu.m to about 20.0 .mu.m.« less

Thin Bioactive Zn Substituted Hydroxyapatite Coating Deposited on Ultrafine Grained Titanium Substrate: Structure Analysis

NASA Astrophysics Data System (ADS)

Prosolov, Konstantin A.; Belyavskaya, Olga A.; Muehle, Uwe; Sharkeev, Yurii P.

2018-02-01

Nanocrystalline Zn substituted hydroxyapatite coatings were deposited by radiofrequency magnetron sputtering on the surface of ultrafine-grained titanium substrates. Cross section transmission electron microscopy provided information about the morphology and texture of the thin film while in-column energy dispersive X-ray analysis confirmed the presence of Zn in the coating. The Zn substituted hydroxyapatite coating was formed by an equiaxed polycrystalline grain structure. Effect of substrate crystallinity on the structure of deposited coating is discussed. An amorphous TiO2 sublayer of 8 nm thickness was detected in the interface between the polycrystalline coating and the Ti substrate. Its appearance in the amorphous state is attributed to prior to deposition etching of the substrate and subsequent condensation of oxygen-containing species sputtered from the target. This layer contributes to the high coating-to-substrate adhesion. The major P-O vibrational modes of high intensity were detected by Raman spectroscopy. The Zn substituted hydroxyapatite could be a material of choice when antibacterial osteoconductive coating with a possibility of withstanding mechanical stress during implantation and service is needed.

Mobility Optimization in LaxBa1-xSnO3 Thin Films Deposited via High Pressure Oxygen Sputtering

NASA Astrophysics Data System (ADS)

Postiglione, William Michael

BaSnO3 (BSO) is one of the most promising semiconducting oxides currently being explored for use in future electronic applications. BSO possesses a unique combination of high room temperature mobility (even at very high carrier concentrations, > 1019 cm-3), wide band gap, and high temperature stability, making it a potentially useful material for myriad applications. Significant challenges remain however in optimizing the properties and processing of epitaxial BSO, a critical step towards industrial applications. In this study we investigate the viability of using high pressure oxygen sputtering to produce high mobility La-doped BSO thin films. In the first part of our investigation we synthesized, using solid state reaction, phase-pure stoichiometric polycrystalline 2% La-doped BaSnO 3 for use as a target material in our sputtering system. We verified the experimental bulk lattice constant, 4.117 A, to be in good agreement with literature values. Next, we set out to optimize the growth conditions for DC sputtering of La doped BaSnO3. We found that mobility for all our films increased monotonically with deposition temperature, suggesting the optimum temperature for deposition is > 900 °C and implicating a likely improvement in transport properties with post-growth thermal anneal. We then preformed systematic studies aimed at probing the effects of varying thickness and deposition rate to optimize the structural and electronic transport properties in unbuffered BSO films. In this report we demonstrate the ability to grow 2% La BSO thin films with an effective dopant activation of essentially 100%. Our films showed fully relaxed (bulk), out-of-plane lattice parameter values when deposited on LaAlO3, MgO, and (LaAlO3)0.3(Sr2 TaAlO6)0.7 substrates, and slightly expanded out-of-plane lattice parameters for films deposited on SrTiO3, GdScO3, and PrScO3 substrates. The surface roughness's of our films were measured via AFM, and determined to be on the nm scale or better. Specular XRD measurements confirmed highly crystalline films with narrow rocking curve FWHMs on the order of 0.05°. The optimum thickness found to maximize mobility was around 100 nm for films deposited at 8 A/min. These films exhibited room temperature mobilities in excess of 50 cm 2V-1s-1 at carrier concentrations 3 x 1020 cm-3 across 4 different substrate materials (LaAlO3, SrTiO3, GdScO3, and PrScO 3). Contrary to expectations, our findings showed no dependence of mobility on substrate mismatch, indicating that threading dislocations are either not the dominant scattering source, or that threading dislocation density in the films was constant regardless of the substrate. The highest mobility film achieved in this study, 70 cm2V -1s-1, was measured for a film grown at a considerably slower rate ( 2 A/min) and lower thickness ( 380 A). Said film was deposited on a PrScO3 (110) substrate, the most closely lattice matched substrate commercially available for BSO (-2.2% pseudo-cubic). This film showed a high out-of-plane lattice parameter from X-ray diffraction (aop = 4.158 A), suggesting a significantly strained film. This result highlights the possibility of sputtering coherent, fully strained, BSO films, far exceeding the theoretical critical thickness for misfit dislocation formation, on closely lattice matched substrates. Overall, this work validates the concept of high pressure oxygen sputtering to produce high mobility La-doped BSO films. The mobility values reported in this thesis are comparable to those found for films deposited via pulsed laser deposition in previous studies, and represent record values for sputter deposited BSO thin films.

Maskless deposition technique for the physical vapor deposition of thin film and multilayer coatings with subnanometer precision and accuracy

DOEpatents

Vernon, Stephen P.; Ceglio, Natale M.

2000-01-01

The invention is a method for the production of axially symmetric, graded and ungraded thickness thin film and multilayer coatings that avoids the use of apertures or masks to tailor the deposition profile. A motional averaging scheme permits the deposition of uniform thickness coatings independent of the substrate radius. Coating uniformity results from an exact cancellation of substrate radius dependent terms, which occurs when the substrate moves at constant velocity. If the substrate is allowed to accelerate over the source, arbitrary coating profiles can be generated through appropriate selection and control of the substrate center of mass equation of motion. The radial symmetry of the coating profile is an artifact produced by orbiting the substrate about its center of mass; other distributions are obtained by selecting another rotation axis. Consequently there is a direct mapping between the coating thickness and substrate equation of motion which can be used to tailor the coating profile without the use of masks and apertures.

High Temperature Pt/Alumina Co-Fired System for 500 C Electronic Packaging Applications

NASA Technical Reports Server (NTRS)

Chen, Liang-Yu; Neudeck, Philip G.; Spry, David J.; Beheim, Glenn M.; Hunter, Gary W.

2015-01-01

Gold thick-film metallization and 96 alumina substrate based prototype packaging system developed for 500C SiC electronics and sensors is briefly reviewed, the needs of improvement are discussed. A high temperature co-fired alumina material system based packaging system composed of 32-pin chip-level package and printed circuit board is discussed for packaging 500C SiC electronics and sensors.

Ferrite-Ferroelectric Heteroepitaxial Structures and Frequency Agile Multiferroic RF Components

DTIC Science & Technology

2012-11-27

crystal LPE YIG films -PZT. (2) Eutectic bonding techniques for ferrite-piezoelectric bilayer synthesis: Samples of YIG/PMN-PT and hexagonal ferrite...Materials: (1) Growth of ferrite films on piezoelectric substrates by electrophoretic deposition techniques: Studies focused on 1-10 u.m thick...polycrystalline YIG films on PZT. The strength of magneto-electric (ME) interactions measured over 1 -40 GHz was comparable to results for bilayers of single

Method of deposition by molecular beam epitaxy

DOEpatents

Chalmers, Scott A.; Killeen, Kevin P.; Lear, Kevin L.

1995-01-01

A method is described for reproducibly controlling layer thickness and varying layer composition in an MBE deposition process. In particular, the present invention includes epitaxially depositing a plurality of layers of material on a substrate with a plurality of growth cycles whereby the average of the instantaneous growth rates for each growth cycle and from one growth cycle to the next remains substantially constant as a function of time.

Method of deposition by molecular beam epitaxy

DOEpatents

Chalmers, S.A.; Killeen, K.P.; Lear, K.L.

1995-01-10

A method is described for reproducibly controlling layer thickness and varying layer composition in an MBE deposition process. In particular, the present invention includes epitaxially depositing a plurality of layers of material on a substrate with a plurality of growth cycles whereby the average of the instantaneous growth rates for each growth cycle and from one growth cycle to the next remains substantially constant as a function of time. 9 figures.

Growing Aligned Carbon Nanotubes for Interconnections in ICs

NASA Technical Reports Server (NTRS)

Li, Jun; Ye, Qi; Cassell, Alan; Ng, Hou Tee; Stevens, Ramsey; Han, Jie; Meyyappan, M.

2005-01-01

A process for growing multiwalled carbon nanotubes anchored at specified locations and aligned along specified directions has been invented. Typically, one would grow a number of the nanotubes oriented perpendicularly to a silicon integrated-circuit (IC) substrate, starting from (and anchored on) patterned catalytic spots on the substrate. Such arrays of perpendicular carbon nanotubes could be used as electrical interconnections between levels of multilevel ICs. The process (see Figure 1) begins with the formation of a layer, a few hundred nanometers thick, of a compatible electrically insulating material (e.g., SiO(x) or Si(y)N(z) on the silicon substrate. A patterned film of a suitable electrical conductor (Al, Mo, Cr, Ti, Ta, Pt, Ir, or doped Si), having a thickness between 1 nm and 2 m, is deposited on the insulating layer to form the IC conductor pattern. Next, a catalytic material (usually, Ni, Fe, or Co) is deposited to a thickness between 1 and 30 nm on the spots from which it is desired to grow carbon nanotubes. The carbon nanotubes are grown by plasma-enhanced chemical vapor deposition (PECVD). Unlike the matted and tangled carbon nanotubes grown by thermal CVD, the carbon nanotubes grown by PECVD are perpendicular and freestanding because an electric field perpendicular to the substrate is used in PECVD. Next, the free space between the carbon nanotubes is filled with SiO2 by means of CVD from tetraethylorthosilicate (TEOS), thereby forming an array of carbon nanotubes embedded in SiO2. Chemical mechanical polishing (CMP) is then performed to remove excess SiO2 and form a flat-top surface in which the outer ends of the carbon nanotubes are exposed. Optionally, depending on the application, metal lines to connect selected ends of carbon nanotubes may be deposited on the top surface. The top part of Figure 2 is a scanning electron micrograph (SEM) of carbon nanotubes grown, as described above, on catalytic spots of about 100 nm diameter patterned by electron-beam lithography. These and other nanotubes were found to have lengths ranging from 2 to 10 m and diameters ranging from 30 to 200 nm, the exact values of length depending on growth times and conditions and the exact values of diameter depending on the diameters and thicknesses of the catalyst spots. The bottom part of Figure 2 is an SEM of an embedded array of carbon nanotubes after CMP.

Thickness-dependent multiferroic behavior of BiFe0.75Cr0.25O3 films over Pt(111)/Ti/SiO2/Si substrate

NASA Astrophysics Data System (ADS)

William, R. V.; Sivaprakash, P.; Marikani, A.; Reddy, V. Raghavendra; Arumugam, S.

2018-02-01

We present here the experimental results of BiFe0.75Cr0.25O3 (BFCO) thin film deposited by sol-gel spin coating technique directly on Pt(111)/Ti/SiO2/Si substrate at different thicknesses. The crystal structure of BFCO has been investigated using X-ray diffraction which acts as a double perovskite structure with high crystallinity obtained at 400 °C. Further microscopic studies such as scanning electron microscope (SEM) with EDAX, transmission electron microscope (TEM) were also used in identifying the grain size and particle distribution over Pt (111) substrate. Atomic force microscopy (AFM) on the films at a different thickness (- 80 to - 250 nm) reveals that the surface roughness and other amplitude parameters increases with the increase in thickness signifying an increase of grain size with thickness. Increase in grain size and substrate clamping effect between the BFCO film and the substrate induces change in ferroelectric polarization and dielectric properties in relation to thickness effect. Similarly, decrease in magnetization from 9.241 emu/cm3 (- 80 nm) to 5.7791 emu/cm3 (- 250 nm) is attributed to the formation of anti-sites and anti-phase boundaries in the films. In addition, temperature dependence of magnetization reveals ferromagnetic super-exchange interaction of BFCO which is unlike the spin structure of antiferromagnetic BiFeO3.

Catalytic nanoporous membranes

DOEpatents

Pellin, Michael J; Hryn, John N; Elam, Jeffrey W

2013-08-27

A nanoporous catalytic membrane which displays several unique features Including pores which can go through the entire thickness of the membrane. The membrane has a higher catalytic and product selectivity than conventional catalysts. Anodic aluminum oxide (AAO) membranes serve as the catalyst substrate. This substrate is then subjected to Atomic Layer Deposition (ALD), which allows the controlled narrowing of the pores from 40 nm to 10 nm in the substrate by deposition of a preparatory material. Subsequent deposition of a catalytic layer on the inner surfaces of the pores reduces pore sizes to less than 10 nm and allows for a higher degree of reaction selectivity. The small pore sizes allow control over which molecules enter the pores, and the flow-through feature can allow for partial oxidation of reactant species as opposed to complete oxidation. A nanoporous separation membrane, produced by ALD is also provided for use in gaseous and liquid separations. The membrane has a high flow rate of material with 100% selectivity. Also provided is a method for producing a catalytic membrane having flow-through pores and discreet catalytic clusters adhering to the inside surfaces of the pores.

Graphene-immobilized flower-like Ni3S2 nanoflakes as a stable binder-free anode material for sodium-ion batteries

NASA Astrophysics Data System (ADS)

Han, Yu; Liu, Shuang-yu; Cui, Lei; Xu, Li; Xie, Jian; Xia, Xue-Ke; Hao, Wen-Kui; Wang, Bo; Li, Hui; Gao, Jie

2018-01-01

A binder-free Ni3S2 electrode was prepared directly on a graphene-coated Ni foam (G/Ni) substrate through surface sulfiding of substrate using thiourea as the sulfur source in this work. The Ni3S2 showed a flower-like morphology and was uniformly distributed on the G/Ni surface. The flower-like Ni3S2 was composed of cross-arrayed nanoflakes with a diameter and a thickness of 1-2 μm and 50 nm, respectively. The free space in the flowers and the thin feature of Ni3S2 buffered the volume changes and relieved mechanical strain during repeated cycling. The intimate contact with the Ni substrate and the fixing effect of graphene maintained the structural stability of the Ni3S2 electrode during cycling. The G/Ni-supported Ni3S2 maintained a reversible capacity of 250 mAh.g-1 after 100 cycles at 50 mA.g-1, demonstrating the good cycling stability as a result of the unique microstructure of this electrode material.

Development of Advanced Conformal Ablative TPS Fabricated from Rayon- and PAN-Based Carbon Felts

NASA Technical Reports Server (NTRS)

Gasch, Matthew; Stackpoole, Margaret; White, Susan; Boghozian, Tane

2016-01-01

The conformal ablative TPS first developed under NASA's Hypersonics Project in the early 2000's demonstrated very low through the thickness conductivity compared to state-ofthe- art PICA. However, in initial arcjet testing of Conformal-1, surface recession rates were 2x higher than PICA. Because commercial carbon felts are currently available as very thin substrates, this was a concern if conformal TPS were to be considered for a mission that required thicker material. Discussed in this paper are the results of the development of an Advanced Conformal TPS derived from thicker, higher density carbon felt. Two substrate systems were evaluated, the first material was a needled rayon-based carbon felt and the other a needled PAN-based carbon felt. Both substrates were impregnated with phenolic resin following the PICA/CPICA process to add a low density phenolic matrix to the system prior to aerothermal screening at the LaRC HyMETS facility and larger scale testing in the NASA ARC Interaction Heating Facility (IHF) at heating fluxes ranging from 250-1700 W/cm2.

The Accuracy of Al and Cu Film Thickness Determinations and the Implications for Electron Probe Microanalysis.

PubMed

Matthews, Mike B; Kearns, Stuart L; Buse, Ben

2018-04-01

The accuracy to which Cu and Al coatings can be determined, and the effect this has on the quantification of the substrate, is investigated. Cu and Al coatings of nominally 5, 10, 15, and 20 nm were sputter coated onto polished Bi using two configurations of coater: One with the film thickness monitor (FTM) sensor colocated with the samples, and one where the sensor is located to one side. The FTM thicknesses are compared against those calculated from measured Cu Lα and Al Kα k-ratios using PENEPMA, GMRFilm, and DTSA-II. Selected samples were also cross-sectioned using focused ion beam. Both systems produced repeatable coatings, the thickest coating being approximately four times the thinnest coating. The side-located FTM sensor indicated thicknesses less than half those of the software modeled results, propagating on to 70% errors in substrate quantification at 5 kV. The colocated FTM sensor produced errors in film thickness and substrate quantification of 10-20%. Over the range of film thicknesses and accelerating voltages modeled both the substrate and coating k-ratios can be approximated by linear trends as functions of film thickness. The Al films were found to have a reduced density of ~2 g/cm2.

Ultrathin Polymer Films, Patterned Arrays, and Microwells

NASA Astrophysics Data System (ADS)

Yan, Mingdi

2002-05-01

The ability to control and tailor the surface and interface properties of materials is important in microelectronics, cell growth control, and lab-on-a-chip devices. Modification of material surfaces with ultrathin polymer films is attractive due to the availability of a variety of polymers either commercially or by synthesis. We have developed two approaches to the attachment of ultrathin polymer films on solid substrates. In the first method, a silane-functionalized perfluorophenyl azide (PFPA-silane) was synthesized and used to covalently immobilize polymer thin films on silicon wafers. Silanization of the wafer surface with the PFPA-silane introduced a monolayer of azido groups which in turn covalently attached the polymer film by way of photochemically initiated insertion reactions. The thickness of the film could be adjusted by the type and the molecular weight of the polymer. The method is versatile due to the general C-H and/or N-H insertion reactions of crosslinker; and therefore, no specific reactive functional groups on the polymers are required. Using this method, a new type of microwell array was fabricated from covalently immobilized polymer thin films on flat substrates. The arrays were characterized with AFM, XPS, and TOF-SIMS. The second method describes the attachment of polymer thin films on solid substrates via UV irradiation. The procedure consisted of spin-coating a polymer film and irradiating the film with UV light. Following solvent extraction, a thin film remained. The thickness of the film, from a few to over a hundred nanometers, was controlled by varying solution concentration and the molecular weight of the polymer.

A sandwiched piezoelectric transducer with flex end-caps for energy harvesting in large force environments

NASA Astrophysics Data System (ADS)

Kuang, Yang; Daniels, Alice; Zhu, Meiling

2017-08-01

This paper presents a sandwiched piezoelectric transducer (SPT) for energy harvesting in large force environments with increased load capacity and electric power output. The SPT uses (1) flex end-caps to amplify the applied load force so as to increase its power output and (2) a sandwiched piezoelectric-substrate structure to reduce the stress concentration in the piezoelectric material so as to increase the load capacity. A coupled piezoelectric-circuit finite element model (CPC-FEM) was developed, which is able to directly predict the electric power output of the SPT connected to a load resistor. The CPC-FEM was used to study the effects of various parameters of the SPT on the performance to obtain an optimal design. These parameters included the substrate thickness, the end-cap material and thickness, the electrode length, the joint length, the end-cap internal angle and the PZT thickness. A prototype with optimised parameters was tested on a loading machine, and the experimental results were compared with simulation. A good agreement was observed between simulation and experiment. When subjected to a 1 kN 2 Hz sinusoidal force applied by the loading machine, the SPT produced an average power of 4.68 mW. The application of the SPT as a footwear energy harvester was demonstrated by fitting the SPT into a boot and performing the tests on a treadmill, and the SPT generated an average power of 2.5 mW at a walking speed of 4.8 km h-1.

Development and Implementation of Methods and Means for Achieving a Uniform Functional Coating Thickness

NASA Astrophysics Data System (ADS)

Shishlov, A. V.; Sagatelyan, G. R.; Shashurin, V. D.

2017-12-01

A mathematical model is proposed to calculate the growth rate of the thin-film coating thickness at various points in a flat substrate surface during planetary motion of the substrate, which makes it possible to calculate an expected coating thickness distribution. Proper software package is developed. The coefficients used for computer simulation are experimentally determined.

Dark-field image contrast in transmission scanning electron microscopy: Effects of substrate thickness and detector collection angle.

PubMed

Woehl, Taylor; Keller, Robert

2016-12-01

An annular dark field (ADF) detector was placed beneath a specimen in a field emission scanning electron microscope operated at 30kV to calibrate detector response to incident beam current, and to create transmission images of gold nanoparticles on silicon nitride (SiN) substrates of various thicknesses. Based on the linear response of the ADF detector diodes to beam current, we developed a method that allowed for direct determination of the percentage of that beam current forward scattered to the ADF detector from the sample, i.e. the transmitted electron (TE) yield. Collection angles for the ADF detector region were defined using a masking aperture above the detector and were systematically varied by changing the sample to detector distance. We found the contrast of the nanoparticles, relative to the SiN substrate, decreased monotonically with decreasing inner exclusion angle and increasing substrate thickness. We also performed Monte Carlo electron scattering simulations, which showed quantitative agreement with experimental contrast associated with the nanoparticles. Together, the experiments and Monte Carlo simulations revealed that the decrease in contrast with decreasing inner exclusion angle was due to a rapid increase in the TE yield of the low atomic number substrate. Nanoparticles imaged at low inner exclusion angles (<150mrad) and on thick substrates (>50nm) showed low image contrast in their centers surrounded by a bright high-contrast halo on their edges. This complex image contrast was predicted by Monte Carlo simulations, which we interpreted in terms of mixing of the nominally bright field (BF) and ADF electron signals. Our systematic investigation of inner exclusion angle and substrate thickness effects on ADF t-SEM imaging provides fundamental understanding of the contrast mechanisms for image formation, which in turn suggest practical limitations and optimal imaging conditions for different substrate thicknesses. Copyright © 2016. Published by Elsevier B.V.

Solution growth of NiO nanosheets supported on Ni foam as high-performance electrodes for supercapacitors

NASA Astrophysics Data System (ADS)

Yan, Hailong; Zhang, Deyang; Xu, Jinyou; Lu, Yang; Liu, Yunxin; Qiu, Kangwen; Zhang, Yihe; Luo, Yongsong

2014-08-01

Well-aligned nickel oxide (NiO) nanosheets with the thickness of a few nanometers supported on a flexible substrate (Ni foam) have been fabricated by a hydrothermal approach together with a post-annealing treatment. The three-dimensional NiO nanosheets were further used as electrode materials to fabricate supercapacitors, with high specific capacitance of 943.5, 791.2, 613.5, 480, and 457.5 F g-1 at current densities of 5, 10, 15, 20, and 25 A g-1, respectively. The NiO nanosheets combined well with the substrate. When the electrode material was bended, it can still retain 91.1% of the initial capacitance after 1,200 charging/discharging cycles. Compared with Co3O4 and NiO nanostructures, the specific capacitance of NiO nanosheets is much better. These characteristics suggest that NiO nanosheet electrodes are promising for energy storage application with high power demands.

Solution growth of NiO nanosheets supported on Ni foam as high-performance electrodes for supercapacitors.

PubMed

Yan, Hailong; Zhang, Deyang; Xu, Jinyou; Lu, Yang; Liu, Yunxin; Qiu, Kangwen; Zhang, Yihe; Luo, Yongsong

2014-01-01

Well-aligned nickel oxide (NiO) nanosheets with the thickness of a few nanometers supported on a flexible substrate (Ni foam) have been fabricated by a hydrothermal approach together with a post-annealing treatment. The three-dimensional NiO nanosheets were further used as electrode materials to fabricate supercapacitors, with high specific capacitance of 943.5, 791.2, 613.5, 480, and 457.5 F g(-1) at current densities of 5, 10, 15, 20, and 25 A g(-1), respectively. The NiO nanosheets combined well with the substrate. When the electrode material was bended, it can still retain 91.1% of the initial capacitance after 1,200 charging/discharging cycles. Compared with Co3O4 and NiO nanostructures, the specific capacitance of NiO nanosheets is much better. These characteristics suggest that NiO nanosheet electrodes are promising for energy storage application with high power demands.

Ablation Modeling of Ares-I Upper State Thermal Protection System Using Thermal Desktop

NASA Technical Reports Server (NTRS)

Sharp, John R.; Page, Arthur T.

2007-01-01

The thermal protection system (TPS) for the Ares-I Upper Stage will be based on Space Transportation System External Tank (ET) and Solid Rocket Booster (SRB) heritage materials. These TPS materials were qualified via hot gas testing that simulated ascent and re-entry aerothermodynamic convective heating environments. From this data, the recession rates due to ablation were characterized and used in thermal modeling for sizing the thickness required to maintain structural substrate temperatures. At Marshall Space Flight Center (MSFC), the in-house code ABL is currently used to predict TPS ablation and substrate temperatures as a FORTRAN application integrated within SINDA/G. This paper describes a comparison of the new ablation utility in Thermal Desktop and SINDA/FLUINT with the heritage ABL code and empirical test data which serves as the validation of the Thermal Desktop software for use on the design of the Ares-I Upper Stage project.

Effects of bias voltage on diamond like carbon coatings deposited using titanium isopropoxide (TIPOT) and acetylene/argon mixtures onto various substrate materials.

PubMed

Said, R; Ghumman, C A A; Teodoro, M N D; Ahmed, W; Abuazza, A; Gracio, J

2010-04-01

RF-PECVD was used to prepare amorphous of carbon (DLC) onto stainless steel 316 and glass substrates. The substrates were negatively biased at between 100 V to 400 V. Thin films of DLC have been deposited using C2H2 and titanium isopropoxide (TIPOT). Argon was used to generate the plasma in the PECVD system chamber. DEKTAK 8 surface stylus profilometer was used to measure the film thickness and the deposition rate was calculated. Micro Raman spectroscopy was employed to determine the chemical structure and bonding present in the films. Composition analysis of the samples was carried out using VGTOF SIMS (IX23LS) instrument. In addition, X-ray photoelectron spectroscopy (XPS) was used to analyze the composition and chemical state of the films. The wettability of the films was examined using the optical contact angle meter (CAM200) system. Two types of liquids with different polarities were used to study changes in the surface energy. The as-grown films were in the thickness range of 200-400 nm. Raman spectroscopy results showed that the I(D)/I(G) ratio decreased when the bias voltage on the stainless steel substrates was increased. This indicates an increase in the graphitic nature of the film deposited. In contrast, on the glass substrates the I(D)/I(G) ratio increased when the bias voltage was increased indicates a greater degree of diamond like character. Chemical composition determined using XPS showed the presence of carbon and oxygen in both samples on glass and stainless steel substrates. Both coatings the contact angle of the films decreased except for 400 V which showed a slight increase. The oxygen is thought to play an important role on the polar component of a-C.

Effects of Gel Thickness on Microscopic Indentation Measurements of Gel Modulus

PubMed Central

Long, Rong; Hall, Matthew S.; Wu, Mingming; Hui, Chung-Yuen

2011-01-01

In vitro, animal cells are mostly cultured on a gel substrate. It was recently shown that substrate stiffness affects cellular behaviors in a significant way, including adhesion, differentiation, and migration. Therefore, an accurate method is needed to characterize the modulus of the substrate. In situ microscopic measurements of the gel substrate modulus are based on Hertz contact mechanics, where Young's modulus is derived from the indentation force and displacement measurements. In Hertz theory, the substrate is modeled as a linear elastic half-space with an infinite depth, whereas in practice, the thickness of the substrate, h, can be comparable to the contact radius and other relevant dimensions such as the radius of the indenter or steel ball, R. As a result, measurements based on Hertz theory overestimate the Young's modulus. In this work, we discuss the limitations of Hertz theory and then modify it, taking into consideration the nonlinearity of the material and large deformation using a finite-element method. We present our results in a simple correction factor, ψ, the ratio of the corrected Young's modulus and the Hertz modulus in the parameter regime of δ/h ≤ min (0.6, R/h) and 0.3 ≤ R/h ≤ 12.7. The ψ factor depends on two dimensionless parameters, R/h and δ/h (where δ is the indentation depth), both of which are easily accessible to experiments. This correction factor agrees with experimental observations obtained with the use of polyacrylamide gel and a microsphere indentation method in the parameter range of 0.1 ≤ δ/h ≤ 0.4 and 0.3 ≤ R/h ≤ 6.2. The effect of adhesion on the use of Hertz theory for small indentation depth is also discussed. PMID:21806932

Aluminum alloy AA-6061 and RSA-6061 heat treatment for large mirror applications

NASA Astrophysics Data System (ADS)

Newswander, T.; Crowther, B.; Gubbels, G.; Senden, R.

2013-09-01

Aluminum mirrors and telescopes can be built to perform well if the material is processed correctly and can be relatively low cost and short schedule. However, the difficulty of making high quality aluminum telescopes increases as the size increases, starting with uniform heat treatment through the thickness of large mirror substrates. A risk reduction effort was started to build and test a ½ meter diameter super polished aluminum mirror. Material selection, the heat treatment process and stabilization are the first critical steps to building a successful mirror. In this study, large aluminum blanks of both conventional AA-6061 per AMS-A-22771 and RSA AA-6061 were built, heat treated and stress relieved. Both blanks were destructively tested with a cut through the thickness. Hardness measurements and tensile tests were completed. We present our results in this paper and make suggestions for modification of procedures and future work.

Analysis of space environment damage to solar cell assemblies from LDEF experiment A0171-GSFC test plate

NASA Technical Reports Server (NTRS)

Hill, David C.; Rose, M. Frank

1994-01-01

The results of the postflight analysis of the solar cell assemblies from the LDEF (Long Duration Exposure facility) experiment A0171 is provided in this NASA sponsored research project. The following data on this research are provided as follows: (1) solar cell description, including, substrate composition and thickness, crystal orientation, anti-reflective coating composition and thickness; (2) preflight characteristics of the solar cell assemblies with respect to current and voltage; and (3) post-flight characteristics of the solar cell assemblies with respect to voltage and current. These solar cell assemblies are part of the Goddard Space Flight Center test plate which was designed to test the space environment effects (radiation, atomic oxygen, thermal cycling, meteoroid and debris) on conductively coated solar cell coversheets, various electrical bond materials, solar cell performance, and other material properties where feasible.

Ultrathin and lightweight microwave absorbers made of mu-near-zero metamaterials

PubMed Central

Zhong, Shuomin; He, Sailing

2013-01-01

We present a theory of perfect absorption in a bilayer model composed of a mu-near-zero (MNZ) metamaterial (MM) absorbing layer on a metallic substrate. Our analytical solutions reveal that a MM layer with a large purely imaginary permeability and a moderate permittivity backed by a metallic plane has a zero reflection at normal incidence when the thickness is ultrathin. The impedance-mismatched metamaterial absorber (MA) can be 77.3% thinner than conventional impedance-matched MAs with the same material loss in order to get the same absorption. A microwave absorber using double-layered spiral MMs with a thickness of only about one percent of the operating wavelength is designed and realized. An absorption efficiency above 93% at 1.74 GHz is demonstrated experimentally at illumination angles up to 60 degrees. Our absorber is 98% lighter than traditional microwave absorbers made of natural materials working at the same frequencies. PMID:23803861

High performance x-ray anti-scatter grid

DOEpatents

Logan, C.M.

1995-05-23

Disclosed are an x-ray anti-scatter grid for x-ray imaging, particularly for screening mammography, and method for fabricating same, x-rays incident along a direct path pass through a grid composed of a plurality of parallel or crossed openings, microchannels, grooves, or slots etched in a substrate, such as silicon, having the walls of the microchannels or slots coated with a high opacity material, such as gold, while x-rays incident at angels with respect to the slots of the grid, arising from scatter, are blocked. The thickness of the substrate is dependent on the specific application of the grid, whereby a substrate of the grid for mammography would be thinner than one for chest radiology. Instead of coating the walls of the slots, such could be filed with an appropriate liquid, such as mercury. 4 Figs.

Fe Oxides on Ag Surfaces: Structure and Reactivity

DOE PAGES

Shipilin, M.; Lundgren, E.; Gustafson, J.; ...

2016-09-09

One layer thick iron oxide films are attractive from both applied and fundamental science perspectives. The structural and chemical properties of these systems can be tuned by changing the substrate, making them promising materials for heterogeneous catalysis. In the present work, we investigate the structure of FeO(111) monolayer films grown on Ag(100) and Ag(111) substrates by means of microscopy and diffraction techniques and compare it with the structure of FeO(111) grown on other substrates reported in literature. We also study the NO adsorption properties of FeO(111)/Ag(100) and FeO(111)/Ag(111) systems utilizing different spectroscopic techniques. Finally, we discuss similarities and differences inmore » the data obtained from adsorption experiments and compare it with previous results for FeO(111)/Pt(111).« less

Fe Oxides on Ag Surfaces: Structure and Reactivity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shipilin, M.; Lundgren, E.; Gustafson, J.

One layer thick iron oxide films are attractive from both applied and fundamental science perspectives. The structural and chemical properties of these systems can be tuned by changing the substrate, making them promising materials for heterogeneous catalysis. In the present work, we investigate the structure of FeO(111) monolayer films grown on Ag(100) and Ag(111) substrates by means of microscopy and diffraction techniques and compare it with the structure of FeO(111) grown on other substrates reported in literature. We also study the NO adsorption properties of FeO(111)/Ag(100) and FeO(111)/Ag(111) systems utilizing different spectroscopic techniques. Finally, we discuss similarities and differences inmore » the data obtained from adsorption experiments and compare it with previous results for FeO(111)/Pt(111).« less

Ion-/proton-conducting apparatus and method

DOEpatents

Yates, Matthew [Penfield, NY; Liu, Dongxia [Rochester, NY

2011-05-17

A c-axis-oriented HAP thin film synthesized by seeded growth on a palladium hydrogen membrane substrate. An exemplary synthetic process includes electrochemical seeding on the substrate, and secondary and tertiary hydrothermal treatments under conditions that favor growth along c-axes and a-axes in sequence. By adjusting corresponding synthetic conditions, an HAP this film can be grown to a controllable thickness with a dense coverage on the underlying substrate. The thin films have relatively high proton conductivity under hydrogen atmosphere and high temperature conditions. The c-axis oriented films may be integrated into fuel cells for application in the intermediate temperature range of 200-600.degree. C. The electrochemical-hydrothermal deposition technique may be applied to create other oriented crystal materials having optimized properties, useful for separations and catalysis as well as electronic and electrochemical applications, electrochemical membrane reactors, and in chemical sensors.

Development of a process for producing ribbon shaped filaments. [production of silicon carbide filaments

NASA Technical Reports Server (NTRS)

Debolt, H. E.; Krukonis, V. J.

1973-01-01

Silicon carbide (SiC) ribbon filaments were produced on a carbon ribbon substrate, about 1500 microns (60 mils) wide and 100 microns (4 mils) thick in lengths up to 2 meters (6 ft), and with tensile strengths up to 142 KN/cm sq (206 Ksi). During the course of the study, ribbon filaments of boron were also produced on the carbon ribbon substrate; the boron ribbon produced was extremely fragile. The tensile strength of the SiC ribbon was limited by large growths or flaws caused by anomalies at the substrate surface; these anomalies were either foreign dirt or substrate imperfections or both. Related work carried out on round 100 micron (4 mils) diameter SiC filaments on a 33 micron (1.3 mil) diameter, very smooth carbon monofilament substrate has shown that tensile strengths as high as 551 KN/cm sq (800 Ksi) are obtainable with the SiC-carbon round substrate combination, and indicates that if the ribbon substrate surface and ribbon deposition process can be improved similar strengths can be realizable. Cost analysis shows that 100 micron x 5-10 micron SiC ribbon can be very low cost reinforcement material.

Reflection/suppression coatings for 900 - 1200 A radiation

NASA Technical Reports Server (NTRS)

Edelstein, Jerry

1989-01-01

The design and performance of multiple-layer, selective-reflection, selective-suppression coatings for the 900 - 1200 A band are described. These coatings are designed to optimize both high reflectivity at a desirable wavelength and low reflectivity at an undesirable wavelength. The minimum structure for a selective coating consists of a thin metal or metal oxide layer (50 - 150 A thickness) over an aluminum substrate protected with a semi-transparent dielectric (100 - 1000 A thickness). Predicted coating performance is strongly effected by varying the layer combination and thickness. A graphical method of optimizing the coating layer structure is developed. Aluminum, silicon, their oxides, and gold have been investigated as coating layer materials. A very simple coating with a 1026 to 1216 A reflectivity ratio greater than 100 was fabricated. Such reflection/suppression coatings may be of great utility to spaceborne EUV spectrographs.

Characterization of SiGe thin films using a laboratory X-ray instrument

PubMed Central

Ulyanenkova, Tatjana; Myronov, Maksym; Benediktovitch, Andrei; Mikhalychev, Alexander; Halpin, John; Ulyanenkov, Alex

2013-01-01

The technique of reciprocal space mapping using X-rays is a recognized tool for the nondestructive characterization of epitaxial films. X-ray scattering from epitaxial Si0.4Ge0.6 films on Si(100) substrates using a laboratory X-ray source was investigated. It is shown that a laboratory source with a rotating anode makes it possible to investigate the material parameters of the super-thin 2–6 nm layers. For another set of partially relaxed layers, 50–200 nm thick, it is shown that from a high-resolution reciprocal space map, conditioned from diffuse scattering on dislocations, it is possible to determine quantitatively from the shape of a diffraction peak (possessing no thickness fringes) additional parameters such as misfit dislocation density and layer thickness as well as concentration and relaxation. PMID:24046495

Characterization of SiGe thin films using a laboratory X-ray instrument.

PubMed

Ulyanenkova, Tatjana; Myronov, Maksym; Benediktovitch, Andrei; Mikhalychev, Alexander; Halpin, John; Ulyanenkov, Alex

2013-08-01

The technique of reciprocal space mapping using X-rays is a recognized tool for the nondestructive characterization of epitaxial films. X-ray scattering from epitaxial Si 0.4 Ge 0.6 films on Si(100) substrates using a laboratory X-ray source was investigated. It is shown that a laboratory source with a rotating anode makes it possible to investigate the material parameters of the super-thin 2-6 nm layers. For another set of partially relaxed layers, 50-200 nm thick, it is shown that from a high-resolution reciprocal space map, conditioned from diffuse scattering on dislocations, it is possible to determine quantitatively from the shape of a diffraction peak (possessing no thickness fringes) additional parameters such as misfit dislocation density and layer thickness as well as concentration and relaxation.

Influence of C60 co-deposition on the growth kinetics of diindenoperylene-From rapid roughening to layer-by-layer growth in blended organic films

NASA Astrophysics Data System (ADS)

Lorch, C.; Novák, J.; Banerjee, R.; Weimer, S.; Dieterle, J.; Frank, C.; Hinderhofer, A.; Gerlach, A.; Carla, F.; Schreiber, F.

2017-02-01

We investigated the growth of the two phase-separating materials diindenoperylene (DIP) and buckminsterfullerene C60 with different mixing ratio in real-time and in situ by X-ray scattering experiments. We found that at room temperature, mixtures with an excess of DIP show a growth mode which is very close to the perfect layer-by-layer limit with DIP crystallites forming over the entire film thickness. An unexpected increase in the island size is observed for these mixtures as a function of film thickness. On the other hand, equimolar and C60 dominated mixtures grow with poor crystallinity but form very smooth films. Additionally, it is observed that higher substrate temperatures lead to an increase in the length scale of phase separation with film thickness.

Inkjet-based adaptive planarization (Conference Presentation)

NASA Astrophysics Data System (ADS)

Singhal, Shrawan; Grigas, Michelle M.; Khusnatdinov, Niyaz; Sreenivasan, Srinivasan V.

2017-03-01

Planarization is a critical unit step in the lithography process because it enables patterning of surfaces with versatile pattern density without compromising on the stringent planarity and depth-of-focus requirements. In addition to nanoscale pattern density variation, parasitics such as pre-existing wafer topography, can corrupt the desired process output after planarization. The topography of any surface can be classified in three broad categories, depending upon the amplitude and spatial wavelength of the same [1], [2]: (i) nominal shape, (ii) nanotopography and (iii) roughness. The nominal shape is given by the largest spatial wavelengths, typically < 20mm. For spatial length scales of 1-20mm, height variations at this spatial wavelength range are classified as nanotopography. Roughness usually has lower spatial wavelengths. While the nominal shape of a substrate surface is usually decided by the nature of wafer preparation and the tooling and chucking infrastructure used in the same, roughness is usually mitigated by standard polishing techniques. It is the intermediate nanotopography that is probably the most critical surface topography parameter. This is because most traditional polishing techniques cannot selectively address pre-existing substrate topography, without introducing a parasitic signature at the scale of nanotopography. Moreover, fields with pattern density variation typically also have length scales that are commensurate with nanotopography. It is thus instructive to summarize existing planarization technology to understand current limitations. Spin on Glass and Etch back is one technique used for micron scale device manufacturing [3]. As the name implies, a glass dielectric is spin-coated on the substrate followed by etching in a chemistry that ensures equal etching rates for both the sacrificial glass and the underlying film or substrate material. Photoresists may also be used instead of glass. However, the global planarity that can be achieved by this technique is limited. Also, planarization over a large isolated topographical feature has been studied for the reverse-tone Jet-and-Flash Imprint Lithography process, also known as JFIL-R [4]. This relies on surface tension and capillary effects to smoothen a spin-coated Si containing film that can be etched to obtain a smooth profile. To meet the stringent requirement of planarity in submicron device technologies Chemical Mechanical Planarization (CMP) is the most widely used planarization technology [5], [6]. It uses a combination of abrasive laden chemical slurry and a mechanical pad for achieving planar profiles. The biggest concern with CMP is the dependence of material removal rate on the pattern density of material, leading to the formation of a step between the high density and low-density. The step shows up as a long-range thickness variation in the planarized film, similar in scale to pre-existing substrate topography that should have been polished away. Preventive techniques like dummy fill and patterned resist can be used to reduce the variation in pattern density. These techniques increase the complexity of the planarization process and significantly limit the device design flexibility. Contact Planarization (CP) has also been reported as an alternative to the CMP processing [7], [8]. A substrate is spin coated with a photo curable material and pre baked to remove residual solvent. An ultra-flat surface or an optical flat is pressed on the spin-coated wafer. The material is forced to reflow. Pressure is used to spread out material evenly and achieve global planarization. The substrate is then exposed to UV radiation to harden the photo curable material. Although attractive, this process is not adaptive as it does not account for differences in surface topography of the wafer and the optical flat, nor can it address all the parasitics that arise during the process itself. The optical flat leads to undesirable planarization of even the substrate nominal shape and nanotopography, which corrupts the final film thickness profile. Hence, it becomes extremely difficult to eliminate this signature to a desirable extent without introducing other parasitic signatures. An example of this is shown in Figure 1. In this paper, a novel adaptive planarization process has been presented that potentially addresses the problems associated with planarization of varying pattern density, even in the presence of pre-existing substrate topography [9]. This process is called Inkjet-enabled Adaptive Planarization (IAP). The IAP process uses an inverse optimization scheme, built around a validated fluid mechanics-based forward model [10], that takes the pre-existing substrate topography and pattern layout as inputs. It then generates an inkjet drop pattern with a material distribution that is correlated with the desired planarization film profile. This allows a contiguous film to be formed with the desired thickness variation to cater to the topography and any parasitic signatures caused by the pattern layout. This film is formed by the coercing action of a compliant superstrate, which forces the drops to spread and merge and eliminates any bubble trapping. Then, the film is cured using blanket UV exposure and the superstrate separated to reveal the desired planarized film. The use of an inverse optimization algorithm allows substrate topography to be addressed adaptively. In other words, the algorithm can generate a drop pattern that does not disturb the pre-existing substrate topography substantially, but only caters to the pattern density variation. This process has potential advantages over other planarization techniques because of its adaptive nature. Hence, the IAP process can cater to substrates of varying topographies and pattern densities by changing the inkjetted material distribution, without any changes in hardware. The IAP process can also address pre-existing substrate topography selectively by conforming to the nominal shape while planarizing over the pattern layout. A schematic of the IAP process is shown in Figure 2. The goal of this paper is to present some preliminary results from the IAP process. A test pattern layout has been generated with the help of photolithography, and is shown in Figure 3. For the purpose of this trial, the nanoscale features have not been patterned, as it is expected that the planarization process will be blind to their presence. Thus, areas with nanoscale patterns have been patterned as a single feature of SiO2 with height equal to 100 nm. These features are adjacent to pattern-less areas, thus marking a drastic change in pattern density. As can be seen in Figure 4, the smallest length scale across which pattern density changes, is 70 microns. The goal of the IAP process is to be able to planarize this pattern with a film that conforms to pre-existing substrate topography. The targeted planarity of the film is 95% 3sigma, while the targeted film thickness at the tallest feature is less than 30 nm. In another trial, the inverse tone of the same layout will also be tested. This pattern has features of height equal to 100 nm where the previous pattern did not. The targeted metrics for the inverse layout are the same as the nominal layout.

The thickness effect of pre-deposited catalyst film on carbon nanotube growth by chemical vapor deposition

NASA Astrophysics Data System (ADS)

Wei, Y. Y.; Eres, Gyula; Lowndes, Douglas H.

2001-03-01

Chemical vapor deposition (CVD) of multi wall carbon nanotubes (MWCNTs) was realized on a substrate with a layer of iron film used as a catalyst. The catalyst film was pre-deposited in an electron-gun evaporator equipped with a movable shutter which partially blocks the beam during the evaporation process to produce a catalyst film with a continuously changing thickness from 0 to 60 nm. This technique creates a growth environment in which the film thickness is the only variable and eliminates sample-to-sample variations, enabling a systematic study of the thickness effect of the catalyst film on CNT growth. After the deposition of the catalyst film, the sample was immediately transferred into a CVD chamber where CNT growth was performed. Using Acetylene (C_2H_2) as a carbon-source gas, at the substrate temperature of around 700^oC, MWCNTs preferentially grow as a dense mat on the thin regions of the catalyst film. Moreover, beyond a certain critical film thickness no tubes were observed. The critical film thickness for CNT growth was found to increase with substrate temperature from 640^oC to 800^oC. There appears to be no strong correlation between the film thickness and the diameter of the tubes. At the substrate temperature of over 900^oC, the deposited carbon formed graphite sheets surrounding the catalyst particles and no CNTs were observed. A plot of the critical thickness of the catalyst film where CNTs start to grow as a function of the substrate temperature has obtained, which can be served as a reference for selecting the growth parameter in MWCNT growth. The significance of these experimental trends is discussed within the framework of the diffusion model for MWCNT growth.

TiO2 coatings via atomic layer deposition on polyurethane and polydimethylsiloxane substrates: Properties and effects on C. albicans growth and inactivation process

NASA Astrophysics Data System (ADS)

Pessoa, R. S.; dos Santos, V. P.; Cardoso, S. B.; Doria, A. C. O. C.; Figueira, F. R.; Rodrigues, B. V. M.; Testoni, G. E.; Fraga, M. A.; Marciano, F. R.; Lobo, A. O.; Maciel, H. S.

2017-11-01

Atomic layer deposition (ALD) surges as an attractive technology to deposit thin films on different substrates for many advanced biomedical applications. Herein titanium dioxide (TiO2) thin films were successful obtained on polyurethane (PU) and polydimethylsiloxane (PDMS) substrates using ALD. The effect of TiO2 films on Candida albicans growth and inactivation process were also systematic discussed. TiCl4 and H2O were used as precursors at 80 °C, while the reaction cycle number ranged from 500 to 2000. Several chemical, physical and physicochemical techniques were used to evaluate the growth kinetics, elemental composition, material structure, chemical bonds, contact angle, work of adhesion and surface morphology of the ALD TiO2 thin films grown on both substrates. For microbiological analyses, yeasts of standard strains of C. albicans were grown on non- and TiO2-coated substrates. Next, the antifungal and photocatalytic activities of the TiO2 were also investigated by counting the colony-forming units (CFU) before and after UV-light treatment. Chlorine-doped amorphous TiO2 films with varied thicknesses and Cl concentration ranging from 2 to 12% were obtained. In sum, the ALD TiO2 films suppressed the yeast-hyphal transition of C. albicans onto PU, however, a high adhesion of yeasts was observed. Conversely, for PDMS substrate, the yeast adhesion did not change, as observed in control. Comparatively to control, the TiO2-covered PDMS had a reduction in CFU up to 59.5% after UV treatment, while no modification was observed to TiO2-covered PU. These results pointed out that ALD chlorine-doped amorphous TiO2 films grown on biomedical polymeric surfaces may act as fungistatic materials. Furthermore, in case of contamination, these materials may also behave as antifungal materials under UV light exposure.

Large Reduction of Hot Spot Temperature in Graphene Electronic Devices with Heat-Spreading Hexagonal Boron Nitride.

PubMed

Choi, David; Poudel, Nirakar; Park, Saungeun; Akinwande, Deji; Cronin, Stephen B; Watanabe, Kenji; Taniguchi, Takashi; Yao, Zhen; Shi, Li

2018-04-04

Scanning thermal microscopy measurements reveal a significant thermal benefit of including a high thermal conductivity hexagonal boron nitride (h-BN) heat-spreading layer between graphene and either a SiO 2 /Si substrate or a 100 μm thick Corning flexible Willow glass (WG) substrate. At the same power density, an 80 nm thick h-BN layer on the silicon substrate can yield a factor of 2.2 reduction of the hot spot temperature, whereas a 35 nm thick h-BN layer on the WG substrate is sufficient to obtain a factor of 4.1 reduction. The larger effect of the h-BN heat spreader on WG than on SiO 2 /Si is attributed to a smaller effective heat transfer coefficient per unit area for three-dimensional heat conduction into the thick, low-thermal conductivity WG substrate than for one-dimensional heat conduction through the thin oxide layer on silicon. Consequently, the h-BN lateral heat-spreading length is much larger on WG than on SiO 2 /Si, resulting in a larger degree of temperature reduction.

Porous substrates filled with nanomaterials

DOEpatents

Worsley, Marcus A.; Baumann, Theodore F.; Satcher, Jr., Joe H.; Stadermann, Michael

2018-04-03

A composition comprising: at least one porous carbon monolith, such as a carbon aerogel, comprising internal pores, and at least one nanomaterial, such as carbon nanotubes, disposed uniformly throughout the internal pores. The nanomaterial can be disposed in the middle of the monolith. In addition, a method for making a monolithic solid with both high surface area and good bulk electrical conductivity is provided. A porous substrate having a thickness of 100 microns or more and comprising macropores throughout its thickness is prepared. At least one catalyst is deposited inside the porous substrate. Subsequently, chemical vapor deposition is used to uniformly deposit a nanomaterial in the macropores throughout the thickness of the porous substrate. Applications include electrical energy storage, such as batteries and capacitors, and hydrogen storage.

Porous substrates filled with nanomaterials

DOEpatents

Worsley, Marcus A.; Baumann, Theodore F.; Satcher, Jr., Joe H.; Stadermann, Michael

2014-08-19

A composition comprising: at least one porous carbon monolith, such as a carbon aerogel, comprising internal pores, and at least one nanomaterial, such as carbon nanotubes, disposed uniformly throughout the internal pores. The nanomaterial can be disposed in the middle of the monolith. In addition, a method for making a monolithic solid with both high surface area and good bulk electrical conductivity is provided. A porous substrate having a thickness of 100 microns or more and comprising macropores throughout its thickness is prepared. At least one catalyst is deposited inside the porous substrate. Subsequently, chemical vapor deposition is used to uniformly deposit a nanomaterial in the macropores throughout the thickness of the porous substrate. Applications include electrical energy storage, such as batteries and capacitors, and hydrogen storage.

Surface texturing of fluoropolymers

NASA Technical Reports Server (NTRS)

Banks, B. A.; Mirtich, M. J.; Sovey, J. S. (Inventor)

1982-01-01

A method is disclosed for improving surface texture for adhesive bonding, metal bonding, substrate plating, decal substrate preparation, and biomedical implant applications. The surface to be bonded is dusted in a controlled fashion to produce a disbursed layer of fine mesh particles which serve as masks. The surface texture is produced by impinging gas ions on the masked surface. The textured surface takes the form of pillars or cones. The bonding material, such as a liquid epoxy, flows between the pillars which results in a bond having increased strength. For bonding metals a thin film of metal is vapor or sputter deposited onto the textured surface. Electroplating or electroless plating is then used to increase the metal thickness in the desired amount.

Laser induced extraplanar propulsion for three-dimensional microfabrication

DOE Office of Scientific and Technical Information (OSTI.GOV)

Birnbaum, A. J.; Pique, A.

The laser induced extraplanar propulsion process is presented for the creation of controllable three-dimensional deformation of on-substrate components. It is demonstrated that the process is compatible with transparent substrates and ductile materials and is highly controllable in terms of the desired deformation via the adjustment of incident laser energy density. Copper films with thicknesses varying from 0.1-1 {mu}m are deformed over bending angles ranging from 0 deg. - 180 deg. A 355 nm laser at fluences ranging from 10-40 mJ/cm{sup 2} is used in conjunction with an indium-tin-oxide propulsion layer to demonstrate the process. Characterization is performed via electron andmore » laser confocal microscopy.« less

Porous Aluminum Oxide and Magnesium Oxide Films Using Organic Hydrogels as Structure Matrices

PubMed Central

Chen, Zimei

2018-01-01

We describe the synthesis of mesoporous Al2O3 and MgO layers on silicon wafer substrates by using poly(dimethylacrylamide) hydrogels as porogenic matrices. Hydrogel films are prepared by spreading the polymer through spin-coating, followed by photo-cross-linking and anchoring to the substrate surface. The metal oxides are obtained by swelling the hydrogels in the respective metal nitrate solutions and subsequent thermal conversion. Combustion of the hydrogel results in mesoporous metal oxide layers with thicknesses in the μm range and high specific surface areas up to 558 m2∙g−1. Materials are characterized by SEM, FIB ablation, EDX, and Kr physisorption porosimetry. PMID:29565802

Laser-Generated Rayleigh Waves Propagating in Transparent Viscoelastic Adhesive Coating/Metal Substrate Systems

NASA Astrophysics Data System (ADS)

Guan, Yi-jun; Sun, Hong-xiang; Yuan, Shou-qi; Zhang, Shu-yi; Ge, Yong

2016-10-01

We have established numerical models for simulating laser-generated Rayleigh waves in coating/substrate systems by a finite element method and investigated the propagation characteristics of Rayleigh waves in systems concerning the viscoelasticity and transparency of adhesive coatings. In this way, we have studied the influence of the mechanical properties of the coating, such as the elastic moduli, viscoelastic moduli, coating thickness, transparency, and coating material, on the propagation characteristics of the Rayleigh waves. The results show that the propagation characteristics of the Rayleigh waves can be divided into low- and high-frequency parts. The high-frequency propagation characteristics of the Rayleigh wave are closely related to the properties of the adhesive coating.

Method for thermally spraying crack-free mullite coatings on ceramic-based substrates

NASA Technical Reports Server (NTRS)

Spitsberg, Irene T. (Inventor); Wang, Hongyu (Inventor); Heidorn, Raymond W. (Inventor)

2001-01-01

A process for depositing a mullite coating on a silicon-based material, such as those used to form articles exposed to high temperatures and including the hostile thermal environment of a gas turbine engine. The process is generally to thermally spray a mullite powder to form a mullite layer on a substrate, in which the thermal spraying process is performed so that the mullite powder absorbs a sufficient low level of energy from the thermal source to prevent evaporation of silica from the mullite powder. Processing includes deposition parameter adjustments or annealing to maintain or reestablish phase equilibrium in the mullite layer, so that through-thickness cracks in the mullite layer are avoided.

Method for thermally spraying crack-free mullite coatings on ceramic-based substrates

NASA Technical Reports Server (NTRS)

Spitsberg, Irene T. (Inventor); Wang, Hongyu (Inventor); Heidorn, Raymond W. (Inventor)

2000-01-01

A process for depositing a mullite coating on a silicon-based material, such as those used to form articles exposed to high temperatures and including the hostile thermal environment of a gas turbine engine. The process is generally to thermally spray a mullite powder to form a mullite layer on a substrate, in which the thermal spraying process is performed so that the mullite powder absorbs a sufficient low level of energy from the thermal source to prevent evaporation of silica from the mullite powder. Processing includes deposition parameter adjustments or annealing to maintain or reestablish phase equilibrium in the mullite layer, so that through-thickness cracks in the mullite layer are avoided.

Normal incidence x-ray mirror for chemical microanalysis

DOEpatents

Carr, M.J.; Romig, A.D. Jr.

1987-08-05

An x-ray mirror for both electron column instruments and micro x-ray fluorescence instruments for making chemical, microanalysis comprises a non-planar mirror having, for example, a spherical reflecting surface for x-rays comprised of a predetermined number of alternating layers of high atomic number material and low atomic number material contiguously formed on a substrate and whose layers have a thickness which is a multiple of the wavelength being reflected. For electron column instruments, the wavelengths of interest lie above 1.5nm, while for x-ray fluorescence instruments, the range of interest is below 0.2nm. 4 figs.

Near-zero IR transmission of VO2 thin films deposited on Si substrate

NASA Astrophysics Data System (ADS)

Zhang, Chunzi; Koughia, Cyril; Li, Yuanshi; Cui, Xiaoyu; Ye, Fan; Shiri, Sheida; Sanayei, Mohsen; Wen, Shi-Jie; Yang, Qiaoqin; Kasap, Safa

2018-05-01

Vanadium dioxide (VO2) thin films of different thickness have been deposited on Si substrates by using DC magnetron sputtering. The effects of substrate pre-treatment by means of seeding (spin coating and ultrasonic bathing) and biasing on the structure and optical properties were investigated. Seeding results in a smaller grain size in the oxide film, whereas biasing results in square-textured crystals. VO2 thin films of 150 nm thick show a near-zero IR transmission in switched state. Especially, the 150 nm thick VO2 thin film with seeding treatment shows an enhanced switching efficiency.

Surface initiated atom transfer radical polymerization grafting of sodium styrene sulfonate from titanium and silicon substrates.

PubMed

Foster, Rami N; Keefe, Andrew J; Jiang, Shaoyi; Castner, David G

2013-11-01

This study investigates the grafting of poly-sodium styrene sulfonate (pNaSS) from trichlorosilane/10-undecen-1-yl 2-bromo-2-methylpropionate functionalized Si and Ti substrates by atom transfer radical polymerization (ATRP). The composition, molecular structure, thickness, and topography of the grafted pNaSS films were characterized with x-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), variable angle spectroscopic ellipsometry (VASE), and atomic force microscopy (AFM), respectively. XPS and ToF-SIMS results were consistent with the successful grafting of a thick and uniform pNaSS film on both substrates. VASE and AFM scratch tests showed the films were between 25 and 49 nm thick on Si, and between 13 and 35 nm thick on Ti. AFM determined root-mean-square roughness values were ∼2 nm on both Si and Ti substrates. Therefore, ATRP grafting is capable of producing relatively smooth, thick, and chemically homogeneous pNaSS films on Si and Ti substrates. These films will be used in subsequent studies to test the hypothesis that pNaSS-grafted Ti implants preferentially adsorb certain plasma proteins in an orientation and conformation that modulates the foreign body response and promotes formation of new bone.

Surface initiated atom transfer radical polymerization grafting of sodium styrene sulfonate from titanium and silicon substrates

PubMed Central

Foster, Rami N.; Keefe, Andrew J.; Jiang, Shaoyi; Castner, David G.

2013-01-01

This study investigates the grafting of poly-sodium styrene sulfonate (pNaSS) from trichlorosilane/10-undecen-1-yl 2-bromo-2-methylpropionate functionalized Si and Ti substrates by atom transfer radical polymerization (ATRP). The composition, molecular structure, thickness, and topography of the grafted pNaSS films were characterized with x-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), variable angle spectroscopic ellipsometry (VASE), and atomic force microscopy (AFM), respectively. XPS and ToF-SIMS results were consistent with the successful grafting of a thick and uniform pNaSS film on both substrates. VASE and AFM scratch tests showed the films were between 25 and 49 nm thick on Si, and between 13 and 35 nm thick on Ti. AFM determined root-mean-square roughness values were ∼2 nm on both Si and Ti substrates. Therefore, ATRP grafting is capable of producing relatively smooth, thick, and chemically homogeneous pNaSS films on Si and Ti substrates. These films will be used in subsequent studies to test the hypothesis that pNaSS-grafted Ti implants preferentially adsorb certain plasma proteins in an orientation and conformation that modulates the foreign body response and promotes formation of new bone. PMID:24482558

Bovine versus Porcine Acellular Dermal Matrix: A Comparison of Mechanical Properties.

PubMed

Adelman, David M; Selber, Jesse C; Butler, Charles E

2014-05-01

Porcine and bovine acellular dermal matrices (PADM and BADM, respectively) are the most commonly used biologic meshes for ventral hernia repair. A previous study suggests a higher rate of intraoperative device failures using PADM than BADM. We hypothesize that this difference is, in part, related to intrinsic mechanical properties of the matrix substrate and source material. The following study directly compares these 2 matrices to identify any potential differences in mechanical properties that may relate to clinical outcomes. Sections of PADM (Strattice; Lifecell, Branchburg, N.J.) and BADM (SurgiMend; TEI Biosciences, Boston, Mass.) were subjected to a series of biomechanical tests, including suture retention, tear strength, and uniaxial tensile strength. Results were collected and compared statistically. In all parameters, BADM exhibited a superior mechanical strength profile compared with PADM of similar thickness. Increased BADM thickness correlated with increased mechanical strength. In suture tear-through testing with steel wire, failure of the steel wire occurred in the 4-mm-thick BADM, whereas the matrix material failed in all other thicknesses of BADM and PADM. Before implantation, BADM is inherently stronger than PADM at equivalent thicknesses and considerably stronger at increased thicknesses. These results corroborate clinical data from a previous study in which PADM was associated with a higher intraoperative device failure rate. Although numerous properties of acellular dermal matrix contribute to clinical outcomes, surgeons should consider initial mechanical strength properties when choosing acellular dermal matrices for load-bearing applications such as hernia repair.

Ceramic capacitor exhibiting graceful failure by self-clearing, method for fabricating self-clearing capacitor

DOEpatents

Kaufman, David Y [Chicago, IL; Saha, Sanjib [Santa Clara, CA

2006-08-29

A short-resistant capacitor comprises an electrically conductive planar support substrate having a first thickness, a ceramic film deposited over the support substrate, thereby defining a ceramic surface; and a metallic film deposited over the ceramic surface, said film having a second thickness which is less than the first thickness and which is between 0.01 and 0.1 microns.

Enhanced adhesion by high energy bombardment

NASA Technical Reports Server (NTRS)

Griffith, Joseph E. (Inventor); Qiu, Yuanxun (Inventor); Tombrello, Thomas A. (Inventor)

1984-01-01

Films (12) of gold, copper, silicon nitride, or other materials are firmly bonded to insulator substrates (12) such as silica, a ferrite, or Teflon (polytetrafluorethylene) by irradiating the interface with high energy ions. Apparently, track forming processes in the electronic stopping region cause intermixing in a thin surface layer resulting in improved adhesion without excessive doping. Thick layers can be bonded by depositing or doping the interfacial surfaces with fissionable elements or alpha emitters.

Processing and Development of Nano-Scale HA Coatings for Biomedical Application

DTIC Science & Technology

2005-01-01

thickness of the film has been processed and tested as a more effective orthopedic/ dental implant coating. The present study aims to increase the service...life of an orthopedic/ dental implant by creating materials that form a strong, long lasting, bond with the Ti substrate as well as juxtaposed bone... dental replacement surgery may quickly return to a normal active lifestyle. Cross-sectional transmission electron microscopy analysis displayed that the

Large, Bright Wind Ripples

NASA Technical Reports Server (NTRS)

2003-01-01

MGS MOC Release No. MOC2-397, 20 June 2003

This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows large, relatively bright ripples of windblown sediment in the Sinus Sabaeus region south of Schiaparelli Basin. The surrounding substrate is thickly mantled by very dark material, possibly windblown silt that settled out of the atmosphere. The picture is located near 7.1oS, 343.7oW. Sunlight illuminates the scene from the left.

Transparent binary-thickness coatings on metal substrates that produce binary patterns of orthogonal elliptical polarization states in reflected light

NASA Astrophysics Data System (ADS)

Azzam, Rasheed M. A.; Angel, Wade W.

1992-12-01

A reflective division-of-wavefront polarizing beam splitter is described that uses a dual- thickness transparent thin-film coating on a metal substrate. A previous design that used a partially clad substrate at the principal angle of the metal [Azzam, JOSA A 5, 1576 (1988)] is replaced by a more general one in which the substrate is coated throughout and the film thickness alternates between two non-zero levels. The incident linear polarization azimuth is chosen near, but not restricted to, 45 degree(s) (measured from the plane of incidence), and the angle of incidence may be selected over a range of values. The design procedure, which uses the two-dimensional Newton-Raphson method, is applied to the SiO2-Au film- substrate system at 633 nm wavelength, as an example, and the characteristics of the various possible coatings are presented.

Quantitative fabrication, performance optimization and comparison of PEG and zwitterionic polymer antifouling coatings.

PubMed

Xing, Cheng-Mei; Meng, Fan-Ning; Quan, Miao; Ding, Kai; Dang, Yuan; Gong, Yong-Kuan

2017-09-01

A versatile fabrication and performance optimization strategy of PEG and zwitterionic polymer coatings is developed on the sensor chip of surface plasma resonance (SPR) instrument. A random copolymer bearing phosphorylcholine zwitterion and active ester side chains (PMEN) and carboxylic PEG coatings with comparable thicknesses were deposited on SPR sensor chips via amidation coupling on the precoated polydopamine (PDA) intermediate layer. The PMEN coating showed much stronger resistance to bovine serum albumin (BSA) adsorption than PEG coating at very thin thickness (∼1nm). However, the BSA resistant efficacy of PEG coating could exceed that of PMEN due to stronger steric repelling effect when the thickness increased to 1.5∼3.3nm. Interestingly, both the PEG and PMEN thick coatings (≈3.6nm) showed ultralow fouling by BSA and bovine plasma fibrinogen (Fg). Moreover, changes in the PEG end group from -OH to -COOH, protein adsorption amount could increase by 10-fold. Importantly, the optimized PMEN and PEG-OH coatings were easily duplicated on other substrates due to universal adhesion of the PDA layer, showed excellent resistance to platelet, bacteria and proteins, and no significant difference in the antifouling performances was observed. These detailed results can explain the reported discrepancy in performances between PEG and zwitterionic polymer coatings by thickness. This facile and substrate-independent coating strategy may benefit the design and manufacture of advanced antifouling biomedical devices and long circulating nanocarriers. Prevention of biofouling is one of the biggest challenges for all biomedical applications. However, it is very difficult to fabricate a highly hydrophilic antifouling coating on inert materials or large devices. In this study, PEG and zwitterion polymers, the most widely investigated polymers with best antifouling performance, are conveniently immobilized on different kinds of substrates from their aqueous solutions by precoating a polydopamine intermediate layer as the universal adhesive and readily re-modifiable surface. Importantly, the coating fabrication and antifouling performance can be monitored and optimized quantitatively by a surface plasma resonance (SPR) system. More significantly, the SPR on-line optimized coatings were successfully duplicated off-line on other substrates, and supported by their excellent antifouling properties. Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Thickness and angular dependent magnetic anisotropy of La0.67Sr0.33MnO3 thin films by Vectorial Magneto Optical Kerr Magnetometry

NASA Astrophysics Data System (ADS)

Chaluvadi, S. K.; Perna, P.; Ajejas, F.; Camarero, J.; Pautrat, A.; Flament, S.; Méchin, L.

2017-10-01

We investigate the in-plane magnetic anisotropy in La0.67Sr0.33MnO3 thin films grown on SrTiO3 (001) substrate using angular dependent room temperature Vectorial Magneto-Optical Kerr Magnetometry. The experimental data reveals that the magnetic anisotropy symmetry landscape significantly changes depending upon the strain and thickness. At low film thickness (12 and 25 nm) the dominant uniaxial anisotropy is due to interface effects, step edges due to mis-cut angle of SrTiO3 substrate. At intermediate thickness, the magnetic anisotropy presents a competition between magnetocrystalline (biaxial) and substrate step induced (uniaxial) anisotropy. Depending upon their relative strengths, a profound biaxial or uniaxial or mixed anisotropy is favoured. Above the critical thickness, magnetocrystalline anisotropy dominates all other effects and shows a biaxial anisotropy.

Thermally stable diamond brazing

DOEpatents

Radtke, Robert P [Kingwood, TX

2009-02-10

A cutting element and a method for forming a cutting element is described and shown. The cutting element includes a substrate, a TSP diamond layer, a metal interlayer between the substrate and the diamond layer, and a braze joint securing the diamond layer to the substrate. The thickness of the metal interlayer is determined according to a formula. The formula takes into account the thickness and modulus of elasticity of the metal interlayer and the thickness of the TSP diamond. This prevents the use of a too thin or too thick metal interlayer. A metal interlayer that is too thin is not capable of absorbing enough energy to prevent the TSP diamond from fracturing. A metal interlayer that is too thick may allow the TSP diamond to fracture by reason of bending stress. A coating may be provided between the TSP diamond layer and the metal interlayer. This coating serves as a thermal barrier and to control residual thermal stress.

Hypervelocity impacts into ice-topped layered targets: Investigating the effects of ice crust thickness and subsurface density on crater morphology

NASA Astrophysics Data System (ADS)

Harriss, Kathryn H.; Burchell, Mark J.

2017-07-01

Many bodies in the outer solar system are theorized to have an ice shell with a different subsurface material below, be it chondritic, regolith, or a subsurface ocean. This layering can have a significant influence on the morphology of impact craters. Accordingly, we have undertaken laboratory hypervelocity impact experiments on a range of multilayered targets, with interiors of water, sand, and basalt. Impact experiments were undertaken using impact speeds in the range of 0.8-5.3 km s-1, a 1.5 mm Al ball bearing projectile, and an impact incidence of 45°. The surface ice crust had a thickness between 5 and 50 mm, i.e., some 3-30 times the projectile diameter. The thickness of the ice crust as well as the nature of the subsurface layer (liquid, well consolidated, etc.) have a marked effect on the morphology of the resulting impact crater, with thicker ice producing a larger crater diameter (at a given impact velocity), and the crater diameter scaling with impact speed to the power 0.72 for semi-infinite ice, but with 0.37 for thin ice. The density of the subsurface material changes the structure of the crater, with flat crater floors if there is a dense, well-consolidated subsurface layer (basalt) or steep, narrow craters if there is a less cohesive subsurface (sand). The associated faulting in the ice surface is also dependent on ice thickness and the substrate material. We find that the ice layer (in impacts at 5 km s-1) is effectively semi-infinite if its thickness is more than 15.5 times the projectile diameter. Below this, the crater diameter is reduced by 4% for each reduction in ice layer thickness equal to the impactor diameter. Crater depth is also affected. In the ice thickness region, 7-15.5 times the projectile diameter, the crater shape in the ice is modified even when the subsurface layer is not penetrated. For ice thicknesses, <7 times the projectile diameter, the ice layer is breached, but the nature of the resulting crater depends heavily on the subsurface material. If the subsurface is noncohesive (loose) material, a crater forms in it. If it is dense, well-consolidated basalt, no crater forms in the exposed subsurface layer.

A nanometric cushion for enhancing scratch and wear resistance of hard films

PubMed Central

Gotlib-Vainshtein, Katya; Girshevitz, Olga; Barlam, David

2014-01-01

Summary Scratch resistance and friction are core properties which define the tribological characteristics of materials. Attempts to optimize these quantities at solid surfaces are the subject of intense technological interest. The capability to modulate these surface properties while preserving both the bulk properties of the materials and a well-defined, constant chemical composition of the surface is particularly attractive. We report herein the use of a soft, flexible underlayer to control the scratch resistance of oxide surfaces. Titania films of several nm thickness are coated onto substrates of silicon, kapton, polycarbonate, and polydimethylsiloxane (PDMS). The scratch resistance measured by scanning force microscopy is found to be substrate dependent, diminishing in the order PDMS, kapton/polycarbonate, Si/SiO2. Furthermore, when PDMS is applied as an intermediate layer between a harder substrate and titania, marked improvement in the scratch resistance is achieved. This is shown by quantitative wear tests for silicon or kapton, by coating these substrates with PDMS which is subsequently capped by a titania layer, resulting in enhanced scratch/wear resistance. The physical basis of this effect is explored by means of Finite Element Analysis, and we suggest a model for friction reduction based on the "cushioning effect” of a soft intermediate layer. PMID:25161836

Chemical Vapor Deposition Synthesis of Graphene-Based Materials and Chemical Modulation of Graphene Electronics

NASA Astrophysics Data System (ADS)

Yan, Zheng

Graphene, a two-dimensional sp2-bonded carbon material, has attracted enormous attention due to its excellent electrical, optical and mechanical properties. Recently developed chemical vapor deposition (CVD) methods could produce large-size and uniform polycrystalline graphene films, limited to gas carbon sources, metal catalyst substrates and degraded properties induced by grain boundaries. Meanwhile, pristine monolayer graphene exhibits a standard ambipolar behavior with a zero neutrality point in field-effect transistors (FETs), limiting its future electronic applications. This thesis starts with the investigation of CVD synthesis of pristine and N-doped graphene with controlled thickness using solid carbon sources on metal catalyst substrates (chapter 1), and then discusses the direct growth of bilayer graphene on insulating substrates, including SiO2, h-BN, Si3N4 and Al2O3, without needing further transfer-process (chapter 2). Chapter 3 discusses the synthesis of high-quality graphene single crystals and hexagonal onion-ring-like graphene domains, and also explores the basic growth mechanism of graphene on Cu substrates. To extend graphene's potential applications, both vertical and planar graphene-carbon nanotube hybrids are fabricated using CVD method and their interesting properties are investigated (chapter 4). Chapter 5 discusses how to use chemical methods to modulate graphene's electronic behaviors.

Visible light laser voltage probing on thinned substrates

DOEpatents

Beutler, Joshua; Clement, John Joseph; Miller, Mary A.; Stevens, Jeffrey; Cole, Jr., Edward I.

2017-03-21

The various technologies presented herein relate to utilizing visible light in conjunction with a thinned structure to enable characterization of operation of one or more features included in an integrated circuit (IC). Short wavelength illumination (e.g., visible light) is applied to thinned samples (e.g., ultra-thinned samples) to achieve a spatial resolution for laser voltage probing (LVP) analysis to be performed on smaller technology node silicon-on-insulator (SOI) and bulk devices. Thinning of a semiconductor material included in the IC (e.g., backside material) can be controlled such that the thinned semiconductor material has sufficient thickness to enable operation of one or more features comprising the IC during LVP investigation.

Method of Forming a Composite Coating with Particle Materials that are Readily Dispersed in a Sprayable Polyimide Solution

NASA Technical Reports Server (NTRS)

Tran, Sang Q. (Inventor)

1998-01-01

A method for creating a composite form of coating from a sprayable solution of soluble polyimides and particle materials that are uniformly dispersed within the solution is described. The coating is formed by adding a soluble polyimide to a solvent, then stirring particle materials into the solution. The composite solution is sprayed onto a substrate and heated in an oven for a period of time in order to partially remove the solvent. The process may be repeated until the desired thickness or characteristic of the coating is obtained. The polyimide is then heated to at least 495 F, so that it is no longer soluble.

Ion Diffusion-Directed Assembly Approach to Ultrafast Coating of Graphene Oxide Thick Multilayers.

PubMed

Zhao, Xiaoli; Gao, Weiwei; Yao, Weiquan; Jiang, Yanqiu; Xu, Zhen; Gao, Chao

2017-10-24

The layer-by-layer (LbL) assembly approach has been widely used to fabricate multilayer coatings on substrates with multiple cycles, whereas it is hard to access thick films efficiently. Here, we developed an ion diffusion-directed assembly (IDDA) strategy to rapidly make multilayer thick coatings in one step on arbitrary substrates. To achieve multifunctional coatings, graphene oxide (GO) and metallic ions were selected as the typical building blocks and diffusion director in IDDA, respectively. With diffusion of metallic ions from substrate to negatively charged GO dispersion spontaneously (i.e., from high-concentration region to low-concentration region), GO was assembled onto the substrate sheet-by-sheet via sol-gel transformation. Because metallic ions with size of subnanometers can diffuse directionally and freely in the aqueous dispersion, GO was coated on the substrate efficiently, giving rise to films with desired thickness up to 10 μm per cycle. The IDDA approach shows three main merits: (1) high efficiency with a μm-scale coating rate; (2) controllability over thickness and evenness; and (3) generality for substrates of plastics, metals and ceramics with any shapes and morphologies. With these merits, IDDA strategy was utilized in the efficient fabrication of functional graphene coatings that exhibit outstanding performance as supercapacitors, electromagnetic interference shielding textiles, and anticorrosion coatings. This IDDA approach can be extended to other building blocks including polymers and colloidal nanoparticles, promising for the scalable production and application of multifunctional coatings.

Thickness-dependent blue shift in the excitonic peak of conformally grown ZnO:Al on ion-beam fabricated self-organized Si ripples

DOE Office of Scientific and Technical Information (OSTI.GOV)

Basu, T.; Kumar, M.; Som, T., E-mail: tsom@iopb.res.in

2015-09-14

Al-doped ZnO (AZO) thin films of thicknesses 5,10, 15, 20, and 30 nm were deposited on 500 eV argon ion-beam fabricated nanoscale self-organized rippled-Si substrates at room temperature and are compared with similar films deposited on pristine-Si substrates (without ripples). It is observed that morphology of self-organized AZO films is driven by the underlying substrate morphology. For instance, for pristine-Si substrates, a granular morphology evolves for all AZO films. On the other hand, for rippled-Si substrates, morphologies having chain-like arrangement (anisotropic in nature) are observed up to a thickness of 20 nm, while a granular morphology evolves (isotropic in nature) for 30 nm-thick film.more » Photoluminescence studies reveal that excitonic peaks corresponding to 5–15 nm-thick AZO films, grown on rippled-Si templates, show a blue shift of 8 nm and 3 nm, respectively, whereas the peak shift is negligible for 20-nm thick film (with respect to their pristine counter parts). The observed blue shifts are substantiated by diffuse reflectance study and attributed to quantum confinement effect, associated with the size of the AZO grains and their spatial arrangements driven by the anisotropic morphology of underlying rippled-Si templates. The present findings will be useful for making tunable AZO-based light-emitting devices.« less

Wear of tin coating and Al-Si alloy substrate against carburized steel under mixed lubrication

NASA Astrophysics Data System (ADS)

Wang, Q.; Cheng, H. S.; Fine, M. E.

1994-04-01

Tin coatings on Al-Si alloys are widely used in the automotive industries. The soft tin coating and the harder substrate alloy form a tribological system with the advantages of low friction and reasonably high load-bearing capacity. Wear tests of tin coated Al-Si Z332 alloy in conformal contact against carburized 1016 steel have been carried out under mixed lubrications with SAE 10W30 oil to study the wear mechanisms. Two major wear mechanisms, uniform wear of the tin coating due to micro-plowing and spall pitting related to the substrate are found to contribute to the bearing material loss when the fluid lubrication film is relatively thick (Lambda about 1.6). Under conditions of thinner films (Lambda approximately = 0.8), some local coating debonding occurs. The pitting and local coating debounding are closely related to fracture in the substrate. The bonding between silicon and tin seems to be weaker than between aluminum and tin. During wear, oxidation occurs.

An investigation of Au/Ti multilayer thin-films: surface morphology, structure and interfacial/surface migration of constituents under applied thermal stress

NASA Astrophysics Data System (ADS)

Senevirathne, Indrajith; Kemble, Eric; Lavoie, John

2014-03-01

Multilayer thin films are ubiquitous in industry. Au/Ti/substrate is unique due to possible biological applications in proof of concept devices. Material used for substrates include borosilicate glass, and quartz. Typical Ti depositions on substrates give rise to Stanski-Krastonov (SK) like growth while Frank-van der Merwe (FM) like growth is preferred. Ti films with thickness of ~ 100nm were deposited onto varying substrates using a thermal evaporator. The additional Au layer is then deposited via magnetron sputter deposition at 100mtorr at low deposition rates (~ 1ML/min) onto the Ti thin film. These systems were annealed at varying temperatures and at different durations. Systems were investigated via AFM (Atomic Force Microscopy) probes to examine the surface morphology, and structure. Further, the ambient contamination and elemental distribution/diffusion at annealing was investigated via Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray spectroscopy (EDX). PASSHE FPDC Annual Grant (LOU # 2010-LHU-03)

Deposition of high quality YBa2Cu3O(7-delta) thin films over large areas by pulsed laser ablation with substrate scanning

NASA Technical Reports Server (NTRS)

Davis, M. F.; Wosik, J.; Forster, K.; Deshmukh, S. C.; Rampersad, H. R.

1991-01-01

The paper describes thin films deposited in a system where substrates are scanned over areas up to 3.5 x 3.5 cm through the stationary plume of an ablated material defined by an aperture. These YBCO films are deposited on LaAlO3 and SrTiO3 substrates with the thickness of 90 and 160 nm. Attention is focused on the main features of the deposition system: line focusing of the laser beam on the target; an aperture defining the area of the plume; computerized stepper motor-driven X-Y stage translating the heated sampler holder behind the plume-defining aperture in programmed patterns; and substrate mounting block with uniform heating at high temperatures over large areas. It is noted that the high degree of uniformity of the properties in each film batch illustrates that the technique of pulsed laser deposition can be applied to produce large YBCO films of high quality.

Dependence of anti-Stokes/Stokes intensity ratios on substrate optical properties for Brillouin light scattering from ultrathin iron films

NASA Astrophysics Data System (ADS)

Cochran, J. F.; From, M.; Heinrich, B.

1998-06-01

Brillouin light scattering experiments have been used to investigate the intensity of 5145 Å laser light backscattered from spin waves in 20 monolayer thick Fe(001) films. The experiments have shown that the ratio of frequency upshifted light intensity to frequency downshifted light intensity depends upon the material of the substrate used to support the iron films. For a fixed magnetic field and for a fixed angle of incidence of the laser light this intensity ratio is much larger for an iron film deposited on a sulphur passivated GaAs(001) substrate than for an iron film deposited on a Ag(001) substrate. The data have been compared with a calculation that takes into account multiple scattering of the optical waves in the iron film and in a protective gold overlayer. The observations are in qualitative agreement with the theory, except for angles of incidence greater than 60°.

Structure and corrosion behavior of sputter deposited cerium oxide based coatings with various thickness on Al 2024-T3 alloy substrates

NASA Astrophysics Data System (ADS)

Liu, Yuanyuan; Huang, Jiamu; Claypool, James B.; Castano, Carlos E.; O'Keefe, Matthew J.

2015-11-01

Cerium oxide based coatings from ∼100 to ∼1400 nm in thickness were deposited onto Al 2024-T3 alloy substrates by magnetron sputtering of a 99.99% pure CeO2 target. The crystallite size of CeO2 coatings increased from 15 nm to 46 nm as the coating thickness increased from ∼100 nm to ∼1400 nm. The inhomogeneous lattice strain increased from 0.36% to 0.91% for the ∼100 nm to ∼900 nm thick coatings and slightly decreased to 0.89% for the ∼1400 nm thick coating. The highest adhesion strength to Al alloy substrates was for the ∼210 nm thick coating, due to a continuous film coverage and low internal stress. Electrochemical measurements indicated that sputter deposited crystalline CeO2 coatings acted as physical barriers that provide good cathodic inhibition for Al alloys in saline solution. The ∼900 nm thick CeO2 coated sample had the best corrosion performance that increased the corrosion resistance by two orders magnitude and lowered the cathodic current density 30 times compared to bare Al 2024-T3 substrates. The reduced defects and exposed surface, along with suppressed charge mobility, likely accounts for the improved corrosion performance as coating thickness increased from ∼100 nm to ∼900 nm. The corrosion performance decreased for ∼1400 nm thick coatings due in part to an increase in coating defects and porosity along with a decrease in adhesion strength.

The macroscopic delamination of thin films from elastic substrates

PubMed Central

Vella, Dominic; Bico, José; Boudaoud, Arezki; Roman, Benoit; Reis, Pedro M.

2009-01-01

The wrinkling and delamination of stiff thin films adhered to a polymer substrate have important applications in “flexible electronics.” The resulting periodic structures, when used for circuitry, have remarkable mechanical properties because stretching or twisting of the substrate is mostly accommodated through bending of the film, which minimizes fatigue or fracture. To date, applications in this context have used substrate patterning to create an anisotropic substrate-film adhesion energy, thereby producing a controlled array of delamination “blisters.” However, even in the absence of such patterning, blisters appear spontaneously, with a characteristic size. Here, we perform well-controlled experiments at macroscopic scales to study what sets the dimensions of these blisters in terms of the material properties and explain our results by using a combination of scaling and analytical methods. Besides pointing to a method for determining the interfacial toughness, our analysis suggests a number of design guidelines for the thin films used in flexible electronic applications. Crucially, we show that, to avoid the possibility that delamination may cause fatigue damage, the thin film thickness must be greater than a critical value, which we determine. PMID:19556551

Error Analysis of Indirect Broadband Monitoring of Multilayer Optical Coatings using Computer Simulations

NASA Astrophysics Data System (ADS)

Semenov, Z. V.; Labusov, V. A.

2017-11-01

Results of studying the errors of indirect monitoring by means of computer simulations are reported. The monitoring method is based on measuring spectra of reflection from additional monitoring substrates in a wide spectral range. Special software (Deposition Control Simulator) is developed, which allows one to estimate the influence of the monitoring system parameters (noise of the photodetector array, operating spectral range of the spectrometer and errors of its calibration in terms of wavelengths, drift of the radiation source intensity, and errors in the refractive index of deposited materials) on the random and systematic errors of deposited layer thickness measurements. The direct and inverse problems of multilayer coatings are solved using the OptiReOpt library. Curves of the random and systematic errors of measurements of the deposited layer thickness as functions of the layer thickness are presented for various values of the system parameters. Recommendations are given on using the indirect monitoring method for the purpose of reducing the layer thickness measurement error.

Critical thickness ratio for buckled and wrinkled fruits and vegetables

NASA Astrophysics Data System (ADS)

Dai, Hui-Hui; Liu, Yang

2014-11-01

This work aims at establishing the geometrical constraint for buckled and wrinkled shapes by modeling a fruit/vegetable with exocarp and sarcocarp as a hyperelastic layer-substrate structure subjected to uniaxial compression. A careful analysis on the derived bifurcation condition leads to the finding of a critical thickness ratio which separates the buckling and wrinkling modes, and remarkably, which is independent of the material stiffnesses. More specifically, it is found that if the thickness ratio is smaller than this critical value a fruit/vegetable should be in a buckled shape (under a sufficient stress); if a fruit/vegetable is in a wrinkled shape the thickness ratio is always larger than this critical value. To verify the theoretical prediction, we consider four types of buckled fruits/vegetables and four types of wrinkled fruits/vegetables with three samples in each type. The geometrical parameters for the 24 samples are measured and it is found that indeed all the data fall into the theoretically predicted buckling or wrinkling domains.

Interface thermal conductance of van der Waals monolayers on amorphous substrates

NASA Astrophysics Data System (ADS)

Correa, Gabriela C.; Foss, Cameron J.; Aksamija, Zlatan

2017-03-01

Heterostructures based on atomic monolayers are emerging as leading materials for future energy efficient and multifunctional electronics. Due to the single atom thickness of monolayers, their properties are strongly affected by interactions with the external environment. We develop a model for interface thermal conductance (ITC) in an atomic monolayer van der Waals bonded to a disordered substrate. Graphene on SiO2 is initially used in our model and contrasted against available experimental data; the model is then applied to monolayer molybdenum disulfide (MoS2) on SiO2 substrate. Our findings show the dominant carrier of heat in both graphene and MoS2 in the cross-plane direction is the flexural (ZA) phonon mode, owing to the large overlap between graphene ZA and substrate vibrational density of states. The rate of phonon transfer across the interface depends quadratically on the substrate coupling constant K a , but this interaction also causes a lifting of the lowest flexural phonon modes. As a result, ITC depends roughly linearly on the strength of the coupling between a monolayer and its substrate. We conclude that, in both graphene and MoS2 on SiO2, substrate adhesion plays a strong role in determining ITC, requiring further study of substrate coupling in TMDCs.

Ultrafast Thermal Plasma Preparation of Solid Si Films with Potential Application in Photovoltaic Cells: A Parametric Study

NASA Astrophysics Data System (ADS)

Mostajeran Goortani, Behnam; Gitzhofer, François; Bouyer, Etienne; Mousavi, Mehdi

2009-03-01

An innovative method, namely ultrafast plasma surface melting, is developed to fabricate solid films of silicon with very high rates (150 cm2/min). The method is composed of preparing a suspension of solid particles in a volatile solvent and spreading it on a refractory substrate such as Mo. After solvent evaporation, the resulting porous layer is exposed to the flame tale of inductively coupled RF plasma to sinter and melt the surface particles and to prepare a solid film of silicon. It is shown that by controlling the flow dynamics and heat transfer around the substrate, and managing the kinetic parameters (i.e., exposure time, substrate transport speed, and reaction kinetics) in the reactor, we can produce solid crystalline Si films with the potential applications in photovoltaic cells industry. The results indicate that the optimum formation conditions with a film thickness of 250-700 μm is when the exposure time in the plasma is in the range of 5-12.5 s for a 100 × 50 mm large layer. By combining the Fourier’s law of conduction with the experimental measurements, we obtained an effective heat diffusivity and developed a model to obtain heat diffusion in the porous layer exposed to the plasma. The model further predicts the minimum and maximum exposure time for the substrate in the plasma flame as a function of material properties, the porous layer thickness and of the imposed heat flux.

Ultraviolet-Diode Pump Solid State Laser Removal of Titanium Aluminium Nitride Coating from Tungsten Carbide Substrate

NASA Astrophysics Data System (ADS)

See, Tian Long; Chantzis, Dimitrios; Royer, Raphael; Metsios, Ioannis; Antar, Mohammad; Marimuthu, Sundar

2017-09-01

This paper presents an investigation on the titanium aluminium nitride (TiAlN) coating removal from tungsten carbide (WC-Co) substrate using a diode pump solid state (DPSS) ultraviolet (UV) laser with maximum average power of 90 W, wavelength of 355 nm and pulse width of 50 ns. The TiAlN coating of 1.5 μm thickness is removed from the WC-Co substrate with laser fluence of 2.71 J/cm2 at 285.6 number of pulses (NOP) and with NOP of 117.6 at 3.38 J/cm2 fluence. Titanium oxide formation was observed on the ablated surface due to the re-deposition of ablated titanium residue and also attributed to the high temperature observed during the laser ablation process. Crack width of around 0.2 μm was observed over both TiAlN coating and WC-Co substrate. The crack depth ranging from 1 to 10 μm was observed and is related to the thickness of the melted carbide. The crack formation is a result of the thermal induced stresses caused by the laser beam interaction with the material as well as the higher thermal conductivity of cobalt compared to WC. Two cleaning regions are observed and is a consequence of the Gaussian distribution of the laser beam energy. The surface roughness of the ablated WC-Co increased with increasing laser fluence and NOP.

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

PubMed Central

Ji, Ran

2011-01-01

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

Stress in (Al, Ga)N heterostructures grown on 6H-SiC and Si substrates byplasma-assisted molecular beam epitaxy

NASA Astrophysics Data System (ADS)

Koshelev, O. A.; Nechaev, D. V.; Sitnikova, A. A.; Ratnikov, V. V.; Ivanov, S. V.; Jmerik, V. N.

2017-11-01

The paper describes experimental results on low temperature plasma-assisted molecular beam epitaxy of GaN/AlN heterostructures on both 6H-SiC and Si(111) substrates. We demonstrate that application of migration enhanced epitaxy and metal-modulated epitaxy for growth of AlN nucleation and buffer layers lowers the screw and edge(total)threading dislocation (TD) densities down to 1.7·108 and 2·109 cm-2, respectively, in a 2.8-μm-thick GaN buffer layer grown atop of AlN/6H-SiC. The screw and total TD densities of 1.2·109 and 7.4·109 cm-2, respectively, were achieved in a 1-μm-thickGaN/AlNheterostructure on Si(111). Stress generation and relaxation in GaN/AlN heterostructures were investigated by using multi-beam optical stress sensor (MOSS) to achieve zero substrate curvature at room temperature. It is demonstrated that a 1-μm-thick GaN/AlN buffer layer grown by PA MBE provides planar substrate morphology in the case of growth on Si substrates whereas 5-μm-thick GaN buffer layers have to be used to achieve the same when growing on 6H-SiC substrates.

Thick crystalline films on foreign substrates

DOEpatents

Smith, Henry I.; Atwater, Harry A.; Geis, Michael W.

1986-01-01

To achieve a uniform texture, large crystalline grains or, in some cases, a single crystalline orientation in a thick (>1 .mu.m) film on a foreign substrate, the film is formed so as to be thin (<1 .mu.m) in a certain section. Zone-melting recrystallization is initiated in the thin section and then extended into the thick section. The method may employ planar constriction patterns of orientation filter patterns.

Thick crystalline films on foreign substrates

DOEpatents

Smith, H.I.; Atwater, H.A.; Geis, M.W.

1986-03-18

To achieve a uniform texture, large crystalline grains or, in some cases, a single crystalline orientation in a thick (>1 [mu]m) film on a foreign substrate, the film is formed so as to be thin (<1 [mu]m) in a certain section. Zone-melting recrystallization is initiated in the thin section and then extended into the thick section. The method may employ planar constriction patterns of orientation filter patterns. 2 figs.

Method for high-precision multi-layered thin film deposition for deep and extreme ultraviolet mirrors

DOEpatents

Ruffner, Judith Alison

1999-01-01

A method for coating (flat or non-flat) optical substrates with high-reflectivity multi-layer coatings for use at Deep Ultra-Violet ("DUV") and Extreme Ultra-Violet ("EUV") wavelengths. The method results in a product with minimum feature sizes of less than 0.10-.mu.m for the shortest wavelength (13.4-nm). The present invention employs a computer-based modeling and deposition method to enable lateral and vertical thickness control by scanning the position of the substrate with respect to the sputter target during deposition. The thickness profile of the sputter targets is modeled before deposition and then an appropriate scanning algorithm is implemented to produce any desired, radially-symmetric thickness profile. The present invention offers the ability to predict and achieve a wide range of thickness profiles on flat or figured substrates, i.e., account for 1/R.sup.2 factor in a model, and the ability to predict and accommodate changes in deposition rate as a result of plasma geometry, i.e., over figured substrates.

Interface layer to tailor the texture and surface morphology of Al-doped ZnO polycrystalline films on glass substrates

NASA Astrophysics Data System (ADS)

Nomoto, Junichi; Inaba, Katsuhiko; Kobayashi, Shintaro; Makino, Hisao; Yamamoto, Tetsuya

2017-06-01

A 10-nm-thick radio frequency magnetron-sputtered aluminum-doped zinc oxide (AZO) showing a texture with a preferential (0001) orientation on amorphous glass substrates was used as an interface layer for tailoring the orientation of 490-nm-thick polycrystalline AZO films subsequently deposited by direct current (DC) magnetron sputtering at a substrate temperature of 200 °C. Wide-angle X-ray diffraction pole figure analysis showed that the resulting 500-nm-thick AZO films showed a texture with a highly preferential c-axis orientation. This showed that DC-magnetron-sputtered AZO films grew along with the orientation matching that of the interface layer, whereas 500-nm-thick AZO films deposited on bare glass substrates by DC magnetron sputtering exhibited a mixed orientation of the c-plane and other planes. The surface morphology was also improved while retaining the lateral grain size by applying the interface layer as revealed by atomic force microscopy.

Group-III Nitride Field Emitters

NASA Technical Reports Server (NTRS)

Bensaoula, Abdelhak; Berishev, Igor

2008-01-01

Field-emission devices (cold cathodes) having low electron affinities can be fabricated through lattice-mismatched epitaxial growth of nitrides of elements from group III of the periodic table. Field emission of electrons from solid surfaces is typically utilized in vacuum microelectronic devices, including some display devices. The present field-emission devices and the method of fabricating them were developed to satisfy needs to reduce the cost of fabricating field emitters, make them compatible with established techniques for deposition of and on silicon, and enable monolithic integration of field emitters with silicon-based driving circuitry. In fabricating a device of this type, one deposits a nitride of one or more group-III elements on a substrate of (111) silicon or other suitable material. One example of a suitable deposition process is chemical vapor deposition in a reactor that contains plasma generated by use of electron cyclotron resonance. Under properly chosen growth conditions, the large mismatch between the crystal lattices of the substrate and the nitride causes strains to accumulate in the growing nitride film, such that the associated stresses cause the film to crack. The cracks lie in planes parallel to the direction of growth, so that the growing nitride film becomes divided into microscopic growing single-crystal columns. The outer ends of the fully-grown columns can serve as field-emission tips. By virtue of their chemical compositions and crystalline structures, the columns have low work functions and high electrical conductivities, both of which are desirable for field emission of electrons. From examination of transmission electron micrographs of a prototype device, the average column width was determined to be about 100 nm and the sharpness of the tips was determined to be characterized by a dimension somewhat less than 100 nm. The areal density of the columns was found to about 5 x 10(exp 9)/sq cm . about 4 to 5 orders of magnitude greater than the areal density of tips in prior field-emission devices. The electric field necessary to turn on the emission current and the current per tip in this device are both lower than in prior field-emission devices, such that it becomes possible to achieve longer operational lifetime. Moreover, notwithstanding the lower current per tip, because of the greater areal density of tips, it becomes possible to achieve greater current density averaged over the cathode area. The thickness of the grown nitride film (equivalently, the length of the columns) could lie between about 0.5 microns and a few microns; in any event, a thickness of about 1 micron is sufficient and costs less than do greater thicknesses. It may be possible to grow nitride emitter columns on glass or other substrate materials that cost less than silicon does. What is important in the choice of substrate material is the difference between the substrate and nitride crystalline structures. Inasmuch as the deposition process is nondestructive, an ability to grow emitter columns on a variety of materials would be advantageous in that it would facilitate the integration of field-emitter structures onto previously processed integrated circuits.

Thickness limitations in carbon nanotube reinforced silicon nitride coatings synthesized by vapor infiltration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eres, Gyula

Chemical vapor infiltration is a convenient method for synthesizing carbon nanotube (CNT)-reinforced ceramic coatings. The thickness over which infiltration is relatively uniform is limited by gas phase diffusion in the pore structure. These effects were investigated in two types of silicon nitride matrix composites. With CNTs that were distributed uniformly on the substrate surface dense coatings were limited to thicknesses of several microns. With dual structured CNT arrays produced by photolithography coatings up to 400 gm thick were obtained with minimal residual porosity. Gas transport into these dual structured materials was facilitated by creating micron sized channels between "CNT pillars"more » (i.e. each pillar consisted of a large number of individual CNTs). The experimental results are consistent with basic comparisons between the rates of gas diffusion and silicon nitride growth in porous structures. This analysis also provides a general insight into optimizing infiltration conditions during the fabrication of thick CNT-reinforced composite coatings. (C) 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.« less

Hybrid calcium phosphate coatings for implants

NASA Astrophysics Data System (ADS)

Malchikhina, Alena I.; Shesterikov, Evgeny V.; Bolbasov, Evgeny N.; Ignatov, Viktor P.; Tverdokhlebov, Sergei I.

2016-08-01

Monophasic biomaterials cannot provide all the necessary functions of bones or other calcined tissues. It is necessary to create for cancer patients the multiphase materials with the structure and composition simulating the natural bone. Such materials are classified as hybrid, obtained by a combination of chemically different components. The paper presents the physical, chemical and biological studies of coatings produced by hybrid technologies (HT), which combine primer layer and calcium phosphate (CaP) coating. The first HT type combines the method of vacuum arc titanium primer layer deposition on a stainless steel substrate with the following micro-arc oxidation (MAO) in phosphoric acid solution with addition of calcium compounds to achieve high supersaturated state. MAO CaP coatings feature high porosity (2-8%, pore size 5-7 µm) and surface morphology with the thickness greater than 5 µm. The thickness of Ti primer layer is 5-40 µm. Amorphous MAO CaP coating micro-hardness was measured at maximum normal load Fmax = 300 mN. It was 3.1 ± 0.8 GPa, surface layer elasticity modulus E = 110 ± 20 GPa, roughness Ra = 0.9 ± 0.1 µm, Rz = 7.5 ± 0.2 µm, which is less than the titanium primer layer roughness. Hybrid MAO CaP coating is biocompatible, able to form calcium phosphates from supersaturated body fluid (SBF) solution and also stimulates osteoinduction processes. The second HT type includes the oxide layer formation by thermal oxidation and then CaP target radio frequency magnetron sputtering (RFMS). Oxide-RFMS CaP coating is a thin dense coating with good adhesion to the substrate material, which can be used for metal implants. The RFMS CaP coating has thickness 1.6 ± 0.1 µm and consists of main target elements calcium and phosphorus and Ca/P ratio 2.4. The second HT type can form calcium phosphates from SBF solution. In vivo study shows that hybrid RFMS CaP coating is biocompatible and produces fibrointegration processes.

Effect of tooth substrate and porcelain thickness on porcelain veneer failure loads in vitro.

PubMed

Ge, Chunling; Green, Chad C; Sederstrom, Dalene A; McLaren, Edward A; Chalfant, James A; White, Shane N

2017-12-19

Bonded porcelain veneers are widely used esthetic restorations. High success and survival rates have been reported, but failures do occur. Fractures are the commonest failure mode. Minimally invasive or thin veneers have gained popularity. Increased enamel and porcelain thickness improve the strength of veneers bonded to enamel, but less is known about dentin or mixed substrates. The purpose of this in vitro study was to measure the influences of tooth substrate type (all-enamel, all-dentin, or half-dentin-half-enamel) and veneer thickness on the loads needed to cause initial and catastrophic porcelain veneer failure. Model discoid porcelain veneer specimens of varying thicknesses were bonded to the flattened facial surfaces of incisors with different enamel and dentin tooth substrates, artificially aged, and loaded to failure with a small sphere. Initial and catastrophic fracture events were identified and analyzed statistically and fractographically. Fracture events included initial Hertzian cracks, intermediate radial cracks, and catastrophic gross failure. All specimens retained some porcelain after catastrophic failure. Cement failure occurred at the cement-porcelain interface not at the cement-tooth interface. Porcelain veneers bonded to enamel were substantially stronger and more damage-tolerant than those bonded to dentin or mixed substrates. Increased porcelain thickness substantially raised the loads to catastrophic failure on enamel substrates but only moderately raised the loads to catastrophic failure on dentin or mixed substrates. The veneers bonded to half-dentin-half-enamel behaved remarkably like those bonded wholly to dentin. Porcelain veneers bonded to enamel were substantially stronger and more damage-tolerant than those bonded to dentin or half-enamel-half dentin. Copyright © 2017 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Tailored benzoxazines as novel resin systems for printed circuit boards in high temperature e-mobility applications

NASA Astrophysics Data System (ADS)

Troeger, K.; Darka, R. Khanpour; Neumeyer, T.; Altstaedt, V.

2014-05-01

This study focuses on the development of Bisphenol-F-benzoxazine resins blended with different ratios of a trifunctional epoxy resin suitable as matrix for substrates for high temperature printed circuit board (HT-PCB) applications. With the benzoxazine blends glass transition temperatures of more than 190 °C could be achieved in combination with a coefficient of thermal expansion in thickness direction (z-CTE) of less than 60 ppm/K without adding any fillers. This shows the high potential of the benzoxazine-epoxy blend systems as substrate materials for HT-PCBs. To understand the thermal behavior of the different formulations, the apparent crosslink density was calculated based on data from Dynamic Mechanical Analysis. Laminates in laboratory scale were prepared and characterized to demonstrate the transformation of the neat resin properties into real electronic substrate properties. The produced laminates exhibit a z-CTE below 40 ppm/K.

Solid surface dependent layering of self-arranged structures with fibril-like assemblies of alpha-synuclein

NASA Astrophysics Data System (ADS)

Bukauskas, V.; Šetkus, A.; Šimkienė, I.; Tumėnas, S.; Kašalynas, I.; Rėza, A.; Babonas, J.; Časaitė, V.; Povilonienė, S.; Meškys, R.

2012-03-01

In present work the formation of hybrid constructions composed of alpha-synuclein-based colloidal solutions on various solid surfaces (silica coated Si, mica, CaF2 and KBr) is investigated by scanning probe microscopy, spectrocopic ellipsometry, Fourier transformed infrared spectroscopy and vibrational circular dichroism. Prior to the modification of the solids, the proteins were intentionally fibrilled under special conditions. It is proved that the multi-component coatings are self-arranged on the solid substrates. Depending on the substrate material, the interface films consisting of individual biomolecules can be detected on the solid surfaces. The coatings with fibril-like alpha-synuclein objects can be obtained on solid surfaces with negligible or comparatively thick interface films. The results are interpreted in terms of the charged surface-controlled electrostatic interaction between the substrate and the biomolecules. Solubility of solids is considered in this interpretation.

Electrowetting in a water droplet with a movable floating substrate

NASA Astrophysics Data System (ADS)

Shahzad, Amir; Masud, A. R.; Song, Jang-Kun

2016-05-01

Electrowetting (EW) enables facile manipulation of a liquid droplet on a hydrophobic surface. In this study, manipulation of an electrolyte droplet having a small floating object on it was investigated on a solid hydrophobic substrate under the EW process. Herein, the floating object exhibited a vertical motion under an applied electric field owing to the spreading and contraction of the droplet on its connecting substrates. The field-induced height variation of the floating object was significantly influenced by the thicknesses of the dielectric and hydrophobic materials. A small mass was also placed on the top floating object and its effect on the spreading of the droplet was observed. In this system, the height of the top floating object is precisely controllable under the application of an electric voltage. The proposed system is expected to be highly useful in the design of nano- and micro-oscillatory systems for microengineering.

Electrowetting in a water droplet with a movable floating substrate.

PubMed

Shahzad, Amir; Masud, A R; Song, Jang-Kun

2016-05-01

Electrowetting (EW) enables facile manipulation of a liquid droplet on a hydrophobic surface. In this study, manipulation of an electrolyte droplet having a small floating object on it was investigated on a solid hydrophobic substrate under the EW process. Herein, the floating object exhibited a vertical motion under an applied electric field owing to the spreading and contraction of the droplet on its connecting substrates. The field-induced height variation of the floating object was significantly influenced by the thicknesses of the dielectric and hydrophobic materials. A small mass was also placed on the top floating object and its effect on the spreading of the droplet was observed. In this system, the height of the top floating object is precisely controllable under the application of an electric voltage. The proposed system is expected to be highly useful in the design of nano- and micro-oscillatory systems for microengineering.

Tailored benzoxazines as novel resin systems for printed circuit boards in high temperature e-mobility applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Troeger, K., E-mail: altstaedt@uni-bayreuth.de; Darka, R. Khanpour, E-mail: altstaedt@uni-bayreuth.de; Neumeyer, T., E-mail: altstaedt@uni-bayreuth.de

2014-05-15

This study focuses on the development of Bisphenol-F-benzoxazine resins blended with different ratios of a trifunctional epoxy resin suitable as matrix for substrates for high temperature printed circuit board (HT-PCB) applications. With the benzoxazine blends glass transition temperatures of more than 190 °C could be achieved in combination with a coefficient of thermal expansion in thickness direction (z-CTE) of less than 60 ppm/K without adding any fillers. This shows the high potential of the benzoxazine-epoxy blend systems as substrate materials for HT-PCBs. To understand the thermal behavior of the different formulations, the apparent crosslink density was calculated based on datamore » from Dynamic Mechanical Analysis. Laminates in laboratory scale were prepared and characterized to demonstrate the transformation of the neat resin properties into real electronic substrate properties. The produced laminates exhibit a z-CTE below 40 ppm/K.« less

Structural and optical properties of copper-coated substrates for solar thermal absorbers

NASA Astrophysics Data System (ADS)

Pratesi, Stefano; De Lucia, Maurizio; Meucci, Marco; Sani, Elisa

2016-10-01

Spectral selectivity, i.e. merging a high absorbance at sunlight wavelengths to a low emittance at the wavelengths of thermal spectrum, is a key characteristics for materials to be used for solar thermal receivers. It is known that spectrally selective absorbers can raise the receiver efficiency for all solar thermal technologies. Tubular sunlight receivers for parabolic trough collector (PTC) systems can be improved by the use of spectrally selective coatings. Their absorbance is increased by deposing black films, while the thermal emittance is minimized by the use of properly-prepared substrates. In this work we describe the intermediate step in the fabrication of black-chrome coated solar absorbers, namely the fabrication and characterization of copper coatings on previously nickel-plated stainless steel substrates. We investigate the copper surface features and optical properties, correlating them to the coating thickness and to the deposition process, in the perspective to assess optimal conditions for solar absorber applications.

Fabrication and Characterization of Fully Transparent ZnO Thin-Film Transistors and Self-Switching Nano-Diodes

NASA Astrophysics Data System (ADS)

Sun, Y.; Ashida, K.; Sasaki, S.; Koyama, M.; Maemoto, T.; Sasa, S.; Kasai, S.; Iñiguez-de-la-Torre, I.; González, T.

2015-10-01

Fully transparent zinc oxide (ZnO) based thin-film transistors (TFTs) and a new type of rectifiers calls self-switching nano-diodes (SSDs) were fabricated on glass substrates at room temperature by using low resistivity and transparent conducting Al- doped ZnO (AZO) thin-films. The deposition conditions of AZO thin-films were optimized with pulsed laser deposition (PLD). AZO thin-films on glass substrates were characterized and the transparency of 80% and resistivity with 1.6*10-3 Ωcm were obtained of 50 nm thickness. Transparent ZnO-TFTs were fabricated on glass substrates by using AZO thin-films as electrodes. A ZnO-TFT with 2 μm long gate device exhibits a transconductance of 400 μS/mm and an ON/OFF ratio of 2.8*107. Transparent ZnO-SSDs were also fabricated by using ZnO based materials and clear diode-like characteristics were observed.

Silicon on Ceramic Process: Silicon Sheet Growth and Device Development for the Large-area Silicon Sheet and Cell Development Tasks of the Low-cost Solar Array Project

NASA Technical Reports Server (NTRS)

Chapman, P. W.; Zook, J. D.; Heaps, J. D.; Pickering, C.; Grung, B. L.; Koepke, B.; Schuldt, S. B.

1979-01-01

The technical and economic feasibility of producing solar cell quality sheet silicon was investigated. It was hoped this could be done by coating one surface of carbonized ceramic substrates with a thin layer of large-grain polycrystalline silicon from the melt. Work was directed towards the solution of unique cell processing/design problems encountered with the silicon-ceramic (SOC) material due to its intimate contact with the ceramic substrate. Significant progress was demonstrated in the following areas; (1) the continuous coater succeeded in producing small-area coatings exhibiting unidirectional solidification and substatial grain size; (2) dip coater succeeded in producing thick (more than 500 micron) dendritic layers at coating speeds of 0.2-0.3 cm/sec; and (3) a standard for producing total area SOC solar cells using slotted ceramic substrates was developed.

Using graphene/styrene-isoprene-styrene copolymer composite thin film as a flexible microstrip antenna for the detection of heptane vapors

NASA Astrophysics Data System (ADS)

Olejnik, Robert; Matyas, Jiri; Slobodian, Petr; Riha, Pavel

2018-03-01

Most portable devices, such as mobile phones or tablets, use antennas made of copper. This paper demonstrates the possible use of antenna constructed from electrically conductive polymer composite materials for use in those applications. The method of preparation and the properties of the graphene/styrene-isoprene-styrene copolymer as flexible microstrip antenna are described in this contribution. Graphene/styrene-isoprene-styrene copolymer toluene solution was prepared by means of ultrasound and the PET substrate was dip coated to reach a fine thin film. The main advantages of using PET as a substrate are low weight and flexibility. The final size of the flexible microstrip antenna was 10 × 25 mm with thickness of 0.48 mm (PET substrate 0.25 mm) with a weight of 0.110 g. The resulting antenna operates at a frequency of 1.8 GHz and gain ‑40.02 dB.

Ion-conducting ceramic apparatus, method, fabrication, and applications

DOEpatents

Yates, Matthew [Penfield, NY; Liu, Dongxia [Rochester, NY

2012-03-06

A c-axis-oriented HAP thin film synthesized by seeded growth on a palladium hydrogen membrane substrate. An exemplary synthetic process includes electrochemical seeding on the substrate, and secondary and tertiary hydrothermal treatments under conditions that favor growth along c-axes and a-axes in sequence. By adjusting corresponding synthetic conditions, an HAP this film can be grown to a controllable thickness with a dense coverage on the underlying substrate. The thin films have relatively high proton conductivity under hydrogen atmosphere and high temperature conditions. The c-axis oriented films may be integrated into fuel cells for application in the intermediate temperature range of 200-600.degree. C. The electrochemical-hydrothermal deposition technique may be applied to create other oriented crystal materials having optimized properties, useful for separations and catalysis as well as electronic and electrochemical applications, electrochemical membrane reactors, and in chemical sensors.

Predicted lattice-misfit stresses in a gallium-nitride (GaN) film

NASA Astrophysics Data System (ADS)

Suhir, E.; Yi, S.

2017-02-01

Effective, easy-to-use and physically meaningful analytical predictive models are developed for the evaluation the lattice-misfit stresses (LMS) in a semiconductor film grown on a circular substrate (wafer). The two-dimensional (plane-stress) theory-of-elasticity approximation (TEA) is employed. First of all, the interfacial shearing stresses are evaluated. These stresses might lead to the occurrence and growth of dislocations, as well as to possible delaminations (adhesive strength of the assembly) and the elevated stress and strain in the buffering material, if any (cohesive strength of the assembly). Second of all, the normal radial and circumferential (tangential) stresses acting in the film cross-sections are determined. These stresses determine the short- and long-term strength (fracture toughness) of the film material. It is shown that while the normal stresses in the semiconductor film are independent of its thickness, the interfacial shearing stresses increase with an increase in the induced force (not stress!) acting in the film cross-sections, and that this force increases with an increase in the film thickness. This leads, for a thick enough film, to the occurrence, growth and propagation of dislocations. These start at the assembly ends and propagate, when the film thickness increases, inwards the structure. The TEA data are compared with the results obtained using a simplified strength-of-materials approach (SMA). This approach considers, instead of an actual circular assembly, an elongated bi-material rectangular strip of unit width and of finite length equal to the wafer diameter. The analysis, although applicable to any semiconductor crystal growth (SCG) technology is geared in this analysis to the Gallium-Nitride (GaN) technology. The numerical example is carried out for a GaN film grown on a Silicon Carbide (SiC) substrate. It is concluded that the SMA model is acceptable for understanding the physics of the state of stress and for the prediction of the normal stresses acting in the major mid-portion of the assembly. The SMA model underestimates, however, the maximum interfacial shearing stress at the assembly periphery, and, because of the very nature of the SMA, is unable to address the circumferential stress. This stress can be quite high at the circular boundary of the assembly. At the assembly edge the circumferential stress is as high as σθ = (2-ν1)σ1, i.e., by the factor of 2-ν1 higher than the normal stress, σ1, in the mid-portion of the film. In this formula, ν1 is Poisson's ratio of the film material.

Green technologies in natural and synthetic surfaces use for dumps reclamation

NASA Astrophysics Data System (ADS)

Klimkina, Iryna; Fedotov, Viacheslav; Heilmeier, Hermann

2016-04-01

Last 50 years coal dumps reclamation in Ukraine was based on two- or three-layer models. These models use a fertile substratum underneath a black soil (chernozem) layer 0.5 m thick (Model 1) or 0.70-1 m thick (Model 2). Model 3 has 3 layers. The deepest layer is a substrate which is phytotoxic or unfavourable for crop growth (coal-bearing substrates with a high content of pyrite, saline substrates). The second layers acts as a protective shield and consist of loess (0.5 m). The third is the layer of fertile chernozem (0.3-0.8 m). However, due to the situation of a shortage of fertile soils, a lack of nutrient elements in the waste rock, and a moisture deficit with strong rock acidification, it is considered important to develop new non-traditional reclamation methods based on the geo-synthetic materials used in conjunction with sowing lawn grasses or grass seeds inside. The geogrids and biogeotextiles made from natural materials such as hemp, flax, jute, coconut and other plant biopolymer fibers are recommended for bioremediation. The biodegradable carcass of reclamation covering materials stabilises the slopes, effectively restraints the soil particles from leaching and blowing, and prevents wash-out of the plant seeds, as well as protecting them from being eaten by animals. The research object of the presented work was the coal dumps of sulfide rocks in Western Donbass (Ukraine). These rocks are characterized by low level of the maximum hygroscopic moisture (4.3%) and moisture content not available for plant growth (5-6%). Also the rock has an average level of salinity, mainly of the sulphate type. The main goal of the study was to justify the use of some non-traditional materials such as burlap (jute cloth), agricultural fibers (light non-woven material from polypropylene fiber of spun-bond type) and a padding of polyester in the capacity of a geosynthetic substrate as a basis for the mixed grass crop that enable a reduction in the bioremediation costs (in comparison with traditional methods of covering by fertile soil layer) and the arrangement of lawn roll. A mixture of grass crops was used that included three types of grass seeds which were sown in the condition of hydroponics with settled tap water in a floating poly-foam frame on the one- and two-layer (with grass seeds inside) substrates of the above-mentioned materials. The best results, in terms of seed germination, root and above-ground parts of the plants length, were obtained with a single layer of jute burlap on which practically all germinated seeds reached a high degree of seedlings mass and root productivity similar to indices of growth mixtures in greenhouses. As a mulch of organic ingredients a wide range of crop residues, namely wheat straw, corn stalks, sunflower stalks and husks, and others, can be used.

Distributed Capacitive Sensor for Sample Mass Measurement

NASA Technical Reports Server (NTRS)

Toda, Risaku; McKinney, Colin; Jackson, Shannon P.; Mojarradi, Mohammad; Manohara, Harish; Trebi-Ollennu, Ashitey

2011-01-01

Previous robotic sample return missions lacked in situ sample verification/ quantity measurement instruments. Therefore, the outcome of the mission remained unclear until spacecraft return. In situ sample verification systems such as this Distributed Capacitive (DisC) sensor would enable an unmanned spacecraft system to re-attempt the sample acquisition procedures until the capture of desired sample quantity is positively confirmed, thereby maximizing the prospect for scientific reward. The DisC device contains a 10-cm-diameter pressure-sensitive elastic membrane placed at the bottom of a sample canister. The membrane deforms under the weight of accumulating planetary sample. The membrane is positioned in close proximity to an opposing rigid substrate with a narrow gap. The deformation of the membrane makes the gap narrower, resulting in increased capacitance between the two parallel plates (elastic membrane and rigid substrate). C-V conversion circuits on a nearby PCB (printed circuit board) provide capacitance readout via LVDS (low-voltage differential signaling) interface. The capacitance method was chosen over other potential approaches such as the piezoelectric method because of its inherent temperature stability advantage. A reference capacitor and temperature sensor are embedded in the system to compensate for temperature effects. The pressure-sensitive membranes are aluminum 6061, stainless steel (SUS) 403, and metal-coated polyimide plates. The thicknesses of these membranes range from 250 to 500 m. The rigid substrate is made with a 1- to 2-mm-thick wafer of one of the following materials depending on the application requirements glass, silicon, polyimide, PCB substrate. The glass substrate is fabricated by a microelectromechanical systems (MEMS) fabrication approach. Several concentric electrode patterns are printed on the substrate. The initial gap between the two plates, 100 m, is defined by a silicon spacer ring that is anodically bonded to the glass substrate. The fabricated proof-of-concept devices have successfully demonstrated tens to hundreds of picofarads of capacitance change when a simulated sample (100 g to 500 g) is placed on the membrane.

Photothermoelastic contrast in nanoscale infrared spectroscopy

NASA Astrophysics Data System (ADS)

Morozovska, Anna N.; Eliseev, Eugene A.; Borodinov, Nikolay; Ovchinnikova, Olga S.; Morozovsky, Nicholas V.; Kalinin, Sergei V.

2018-01-01

The contrast formation mechanism in nanoscale Infrared (IR) Spectroscopy is analyzed. The temperature distribution and elastic displacement across the illuminated T-shape boundary between two materials with different IR-radiation absorption coefficients and thermo-physical and elastic properties located on a rigid substrate are calculated self-consistently for different frequencies f ˜ (1 kHz-1 MHz) of IR-radiation modulation (fully coupled problem). Analytical expressions for the temperature and displacement profiles across the "thermo-elastic step" are derived in the decoupling approximation for f = 0 ("static limit"), and conditions for approximation validity at low frequencies of IR-modulation are established. The step height was found to be thickness-independent for thick layers and proportional to the square of the thickness for very thin films. The theoretical results will be of potential interest for applications in the scanning thermo-ionic and thermal infrared microscopies for relatively long sample thermalization times and possibly for photothermal induced resonance microscopy using optomechanical probes.

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

PubMed

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

2017-12-19

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

Thin liquid film in polymer tubing : dynamics and dewetting in partial wetting condition

NASA Astrophysics Data System (ADS)

Hayoun, Pascaline; Letailleur, Alban; Teisseire, Jérémie; Verneuil, Emilie; Lequeux, François; Barthel, Etienne

2015-11-01

Polymers such as PVC and Silicone are low cost materials widely used in industry to produce tubing for fluid transport. Most of these applications involve repeated, intermittent flow of liquids which can lead to unwanted contamination. This study aims at better understanding contamination mechanisms during intermittent flow in polymer tubing, and at elucidating the relation between flow, wetting and contamination. We experimentally and theoretically investigate, flow regimes as well as dewetting process at the triple line induced by gravity flow of a vertical liquid slug in a cylindrical geometry. Our results for Newtonian fluids evidence a succession of thick film formation, hydraulic jump creation in the thickness profile, oscillatory regime and destabilization leading to substrate contamination. In order to understand theoretically the flow, one crucial quantity to assess is the film thickness in the inside of the tube. Based on an absorption measurement method, we provide explanations for behaviors and flow regimes observed experimentally.

Modeling of thin, back-wall silicon solar cells

NASA Technical Reports Server (NTRS)

Baraona, C. R.

1979-01-01

The performance of silicon solar cells with p-n junctions on the nonilluminated surface (i.e., upside-down or back-wall cells) was calculated. These structures consisted of a uniformly shaped p-type substrate layer, a p(+)-type field layer on the front (illuminated) surface, and a shallow, n-type junction on the back (nonilluminated) surface. A four-layer solar cell model was used to calculate efficiency, open-circuit voltage, and short-circuit current. The effect on performance of p-layer thickness and resistivity was determined. The diffusion length was varied to simulate the effect of radiation damage. The results show that peak initial efficiencies greater than 15 percent are possible for cell thicknesses or 100 micrometers or less. After 10 years of radiation damage in geosynchronous orbit, thin (25 to 50 micrometers thick) cells made from 10 to 100 ohm cm material show the smallest decrease (approximately 10 percent) in performance.

Surface Passivation of ZrO2 Artificial Dentures by Magnetized Coaxial Plasma deposition

NASA Astrophysics Data System (ADS)

Arai, Soya; Kurumi, Satoshi; Matsuda, Ken-Ichi; Suzuki, Kaoru; Hara, Katsuya; Kato, Tatsuya; Asai, Tomohiko; Hirose, Hideharu; Masutani, Shigeyuki; Nihon University Team

2015-09-01

Recent growth and fabrication technologies for functional materials have been greatly contributed to drastic development of oral surgery field. Zirconia based ceramics is expected to utilize artificial dentures because these ceramics have good biocompatibility, high hardness and aesthetic attractively. However, to apply these ceramics to artificial dentures, this denture is removed from a dental plate because of weakly bond. For improving this problem, synthesis an Al passivation-layer on the ceramics for bonding with these dental items is suitable. In order to deposit the passivation layer, we focused on a magnetized coaxial plasma deposition (MCPD). The greatest characteristic of MCPD is that high-melting point metal can be deposited on various substrates. Additionally, adhesion force between substrate and films deposited by the MCPD is superior to it of general deposition methods. In this study, we have reported on the growth techniques of Al films on ZrO2 for contributing to oral surgery by the MCPD. Surface of deposited films shows there were some droplets and thickness of it is about 200 nm. Thickness is increased to 500 nm with increasing applied voltage.

Silicon Carbide membranes as substrate for Synchrotron measurements

NASA Astrophysics Data System (ADS)

Altissimo, M.; Iacopi, A.; Hold, L.; Matruglio, A.; Zucchiatti, P.; Vaccari, L.; Bedolla, D. E.; Ulloa Severino, L.; Parisse, P.; Gianoncelli, A.

2018-05-01

Silicon Nitride (SiN) membranes have long been the substrate of choice for many different synchrotron techniques at very different wavelengths (from IR to hard X-rays), due to their ease of production, relative robustness even in films <200 nm in thickness, and compatibility with standard microfabrication techniques. Here we present a set of data referring to custom-made Silicon Carbide (SiC) windows. We measured SiC surface roughness, mechanical robustness and membrane transmission both at IR and soft X-rays wavelengths, and compared the data with standard Si3N4, acquired in the same conditions. Further, we grew HEK293T cells both on Si3N4 and SiC membranes, and analysed them with IR and soft X-ray microscopy. Our data demonstrates how SiC is an excellent choice as membrane material for synchrotron measurements, since it shows higher transmission and higher robustness as compared to Si3N4 of the same thickness, and an improved compatibility for cell culturing, allowing to postulate their use also for bio-oriented research.

Photonics of 2D gold nanolayers on sapphire surface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muslimov, A. E., E-mail: amuslimov@mail.ru; Butashin, A. V.; Nabatov, B. V.

Gold layers with thicknesses of up to several nanometers, including ordered and disordered 2D nanostructures of gold particles, have been formed on sapphire substrates; their morphology is described; and optical investigations are carried out. The possibility of increasing the accuracy of predicting the optical properties of gold layers and 2D nanostructures using quantum-mechanical models based on functional density theory calculation techniques is considered. The application potential of the obtained materials in photonics is estimated.

Department of Defense Advisory Group on Electron Devices. Special Technology Area Review on Microwave Packaging Technology. Appendix

DTIC Science & Technology

1993-02-01

sintered in hydrogen furnace at very high temperatures . Multiple furnace firing occurs until the binders are removed and part density is achieved "* Process...and base Low temperature co-fired ceramic - Metallized for shielding and grounding - Low resistance thick-film metallization - High thermal resistance...ESPECIALLY LOW TEMPERATURE COFIRED CERAMIC CERAMICS HIGH THERMAL CONDUCTIVITY,MATCHED GaAS AND SILICON SUBSTRATE MATERIALS I I,1Z#A,17Mr1 J, TI

The influence of felling season and log-soaking temperature on the wetting and phenol formaldehyde adhesive bonding characteristics of birch veneer

Treesearch

Anti Rohumaa; Christopher G. Hunt; Charles R. Frihart; Pekka Saranpää; Martin Ohlmeyer; Mark Hughes

2014-01-01

Most adhesive studies employing wood veneer as the substrate assume that it is a relatively uniform material if wood species and veneer thickness are constant. In the present study, veneers from rotary cut birch (Betula pendula Roth) were produced from logs harvested in spring, autumn and winter, and soaked at 20°C and 70°C prior to peeling. Firstly...

Self-Limited Growth in Pentacene Thin Films

PubMed Central

2017-01-01

Pentacene is one of the most studied organic semiconducting materials. While many aspects of the film formation have already been identified in very thin films, this study provides new insight into the transition from the metastable thin-film phase to bulk phase polymorphs. This study focuses on the growth behavior of pentacene within thin films as a function of film thickness ranging from 20 to 300 nm. By employing various X-ray diffraction methods, combined with supporting atomic force microscopy investigations, one crystalline orientation for the thin-film phase is observed, while three differently tilted bulk phase orientations are found. First, bulk phase crystallites grow with their 00L planes parallel to the substrate surface; second, however, crystallites tilted by 0.75° with respect to the substrate are found, which clearly dominate the former in ratio; third, a different bulk phase polymorph with crystallites tilted by 21° is found. The transition from the thin-film phase to the bulk phase is rationalized by the nucleation of the latter at crystal facets of the thin-film-phase crystallites. This leads to a self-limiting growth of the thin-film phase and explains the thickness-dependent phase behavior observed in pentacene thin films, showing that a large amount of material is present in the bulk phase much earlier during the film growth than previously thought. PMID:28287698