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in subjects: "Amorphous State"

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Structural characterization of the thermal evolution of tetrahedrally coordinated amorphous carbon films

The authors present the results of a post-deposition annealing structural study on amorphous tetrahedrally-coordinated carbon (a-tC) films on Si(100) prepared by pulsed-laser deposition. Films as-deposited and post-annealed at 200, 300, 400, 500 and 600 C, respectively, are studied using combined X-ray reflectivity and low-angle scattering measurements. The scans are fit to the Fresnel equations to obtain values for average film density, film and interface thickness, and film and interface roug… more

Date: December 1, 1997

Creator: Martinez-Miranda, L.J.; Sullivan, J.P.; Friedmann, T.A.; Siegal, M.P. & DiNardo, N.J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

In situ examination of moving crack tips in ordered intermetallics.

Recent studies have shown that high stress concentrations at moving crack tips in the intermetallic compound NiTi can induce a crystalline-to-amorphous (C-A) transformation of the crack tip region. This stress-induced C-A transformation has a temperature dependence and crystallization behavior similar to those of ion irradiation-induced C-A transformation of NiTi. The present study examines if these similarities between stress- and irradiation-induced amorphization hold true for two other inter… more

Date: January 25, 1999

Creator: Heuer, J.; Lam, N. Q.; Okamoto, P. R. & Stubbins, J. F.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Optical characterization of sputtered carbon films

Spattered carbon films are widely used as protective overcoats for thin film disk media. Raman spectroscopy is nondestructive and relatively rapid and is well suited for the characterization of carbon films. Specific features in the Raman spectra are empirically correlated with the rates of specific types of mechanical wear for both hydrogenated and unhydrogenated films. This observation is interpreted in terms of a random covalent network, in which the mechanical performance of the film is det… more

Date: May 1, 1992

Creator: Ager, J. W., III

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Charged particle detectors based on high quality amorphous silicon deposited with hydrogen or helium dilution of silane

Electrical transport properties of the authors PECVD a-Si:H material has been improved by using hydrogen and/or helium dilution of silane and lower substrate temperature for deposition. For hydrogen-diluted material they have measured electron and hole mobilities {approximately} 4 times larger, and {mu}{tau} values 2-3 times higher than for their standard a-Si:H. The density of ionized dangling bonds (N{sub D}*) also showed a factor of 5-10 improvement. Due to its higher conductivity, the impro… more

Date: November 1, 1994

Creator: Hong, Wan-Shick; Drewery, J. S.; Jing, Tao; Lee, Hyoung-Koo; Kaplan, S. N.; Perez-Mendez, V. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Anisotropic phase separation through the metal-insulator transition in amorphous Mo-Ge and Fe-Ge alloys

Since an amorphous solid is often defined as that which lacks long-range order, the atomic structure is typically characterized in terms of the high-degree of short-range order. Most descriptions of vapor-deposited amorphous alloys focus on characterizing this order, while assuming that the material is chemically homogeneous beyond a few near neighbors. By coupling traditional small-angle x-ray scattering which probes spatial variations of the electron density with anomalous dispersion which cr… more

Date: December 1, 1993

Creator: Regan, M. J.

Item Type: Thesis or Dissertation

Partner: UNT Libraries Government Documents Department

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In situ studies of amorphization of the Ge-Al and Si-Al systems induced by 1 MeV electron irradiation

Ge/Al and Si/Al bilayer specimens, as well as Al-2.3 at. % Ge two-phase alloy specimens, were irradiated in situ with 1 MeV electrons at temperatures in the range 10--190 K in a high voltage electron microscope. At 10 K, it is found that for a Ge/Al bilayer specimen, amorphization at the interface occurs only when the Ge layer faces the incident electron beam, while for a Si/Al bilayer specimen amorphization occurs regardless of the direction of the incident beam. In this case, the critical flu… more

Date: October 1, 1990

Creator: Lin, X. W.; Seidman, D. N. & Okamoto, P. R.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Structure and stability of microvoids in A-Si:H

Microvoids appear to be universally present in a-Si:H as demonstrated by small angle X-ray scattering including the presence of microvoids in device quality glow discharge a-Si:H. We have studied the structural properties of these microvoids with molecular dynamics simulations. Using molecular dynamics simulations with classical potentials, we have created microvoids by removing Si and H atoms from a computer generated a-Si:H network. The internal surfaces of the microvoids were passivated with… more

Date: July 1, 1993

Creator: Biswas, R. & Kwon, I.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

The future of amorphous silicon photovoltaic technology

Amorphous silicon modules are commercially available. They are the first truly commercial thin-film photovoltaic (PV) devices. Well-defined production processes over very large areas (>1 m{sup 2}) have been implemented. There are few environmental issues during manufacturing, deployment in the field, or with the eventual disposal of the modules. Manufacturing safety issues are well characterized and controllable. The highest measured initial efficiency to date is 13.7% for a small triple-stacke… more

Date: June 1, 1995

Creator: Crandall, R. & Luft, W.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Microstructure and mechanical properties of nitrided molybdenum silicide coatings

Mo-Si-N films with a high nitrogen concentration were produced by sputter-deposition in nitrogen plasma. Chemical composition was determined with Rutherford backscattering and nuclear reaction analysis. Ratio of Mo to Si was 1:2 in the coatings with a nitrogen concentration of 50%. Microstructure of the as-deposited coatings on a silicon substrate was amorphous and no crystallization was found after annealing up to 1000{degree}C, although some relaxation was observed in X-ray diffraction. This … more

Date: December 31, 1993

Creator: Hirvonen, J. P.; Suni, I.; Kattelus, H.; Lappalainen, R.; Torri, P.; Kung, H. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Comprehensive research on the stability and electronic properties of a-Si:H and a-SiGe:H alloys and devices. Final subcontract report, 10 March 1991--30 August 1994

This report describes work on the growth of a-Si:H and a-(Si,Ge):H materials and devices using well-controlled growth techniques. The a-Si:H materials were grown at higher temperatures (300{degrees}-375{degrees}C) using electron-cyclotron-resonance (ECR) plasma techniques with a remote H beam. These films have excellent electronic quality and show significant improvements in stability compared with glow-discharge-produced a-Si:H materials. Several problems were encountered during the fabricatio… more

Date: April 1, 1995

Creator: Dalal, V.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Multiple routes for vortex depinning in amorphous thin film superconductors

ffWe present simulations of vortex dynamics in amorphous two-dimensional thin film superconductors, using a new exact method to evaluate long range interactions between vortices. We find that the onset of vortex motion is dominated by filamentary channels of flow. There are multiple patterns of filamentary flow which are stable in a wide range of bias current. As a consequence, there are multiple steps in the differential resistance, each step corresponding to a different pattern of filamentary… more

Date: July 1, 1996

Creator: Groenbech-Jensen, N.; Bishop, A. R. & Dominquez, D.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

The examination of calcium ion implanted alumina with energy filtered transmission electron microscopy

Ion implantation can be used to alter in the optical response of insulators through the formation of embedded nano-sized particles. Single crystal alumina has been implanted at ambient temperature with 50 keV Ca{sup +} to a fluence of 5 {times} 10{sup 16} ions/cm{sup 2}. Ion channeling, Knoop microhardness measurements, and transmission electron microscopy (TEM) indicate that the alumina surface layer was amorphized by the implant. TEM also revealed nano-sized crystals {approx}7--8 nm in diamet… more

Date: April 1, 1997

Creator: Hunt, E.M.; Hampikian, J.M. & Evans, N.D.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Radiation damage effects in ferroelectric LiTaO

Z-cut lithium tantalate (LiTaO{sub 3}) ferroelectric single crystals were irradiated with 200 keV Ar{sup ++} ions. LiTaO{sub 3} possesses a structure that is a derivative of the corundum (Al{sub 2}O{sub 3}) crystal structure. A systematic study of the radiation damage accumulation rate as a function of ion dose was performed using ion-beam channeling experiments. An ion fluence of 2.5 x 10{sup 18} Ar{sup 2+} ions/m{sup 2} was sufficient to amorphize the irradiated volume of a LiTaO{sub 3} cryst… more

Date: August 4, 1999

Creator: Wetteland, C.J.; Sickafus, K.E.; Gopalan, V.; Mitchell, J.N.; Hartmann, T.; Nastasi, M. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

The structure and dynamics of amorphous and crystalline phases of ice

The structures of the high and low-density amorphous phases of ice are studied using several techniques. The diffraction patterns of high and low density amorphous ice are analyzed using reverse Monte Carlo methods and compared with molecular dynamics simulations of these phases. The spectra of crystalline and amorphous phases of ice obtained by Raman and incoherent inelastic neutron scattering are analyzed to yield structural features for comparison with the results of molecular dynamics and R… more

Date: July 14, 2000

Creator: Klug, D. D.; Tse, J. S.; Tulk, C. A.; Svensson, E. C.; Swainson, I. & Loong, C.-K.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Stress-induced amorphization at moving crack tips in NiTi.

In situ fracture studies on thin-film NiTi intermetallic compounds have been carried out in the high-voltage electron microscope at Argonne National Laboratory. Local stress-induced amorphization of regions directly in front of moving crack tips has been observed under tensile loading conditions. The stress-induced amorphization at crack tips exhibits a temperature dependence similar to that of ion-induced amorphization of NiTi. The upper limiting temperature for stress-induced amorphization is… more

Date: January 29, 1998

Creator: Okamoto, P. R.; Heuer, J.; Lam, N. Q.; Ohnuki, S.; Matsukawa, Y.; Tozawa, K. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Deposition of DLC via intense ion beam ablation

Diamond-like carbon films were prepared by high intensity pulsed ion beam ablation of graphite targets. A 350 key, 35 kA, 400 ns pulse width beam, consisting primarily of carbon ions and protons, was focused onto a graphite target at a fluence of 15-45J/cm{sup 2}. Films were deposited onto substrates positioned i.n q n angular array from normal to the target to 90{degrees} off normal. Deposition rates up to 30 nm per pulse, corresponding to an instantaneous deposition rate greater than I mn/sec… more

Date: December 31, 1993

Creator: Johnston, G. P.; Tiwari, P.; Rej, D. J.; Davis, H. A.; Waganaar, W. J.; Muenchausen, R. E. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Amorphous Ge bipolar blocking contacts on Ge detectors

Semiconductor nuclear radiation detectors are usually operated in a full depletion mode and blocking contacts are required to maintain low leakage currents and high electric fields for charge collection. Blocking contacts on Ge detectors typically consist of n-type contacts formed by lithium diffusion and p-type contacts formed by boron ion implantation. Electrical contacts formed using sputtered amorphous Ge (a-Ge) films on high-purity Ge crystals were found to exhibit good blocking behavior i… more

Date: October 1, 1991

Creator: Luke, P. N.; Cork, C. P.; Madden, N. W.; Rossington, C. S. & Wesela, M. F.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Elastic properties of amorphous thin films studied by Rayleigh waves

Physical vapor deposition in ultra-high vacuum was used to co-deposit nickel and zirconium onto quartz single crystals and grow amorphous Ni{sub 1-x}Zr{sub x} (0.1 < x < 0.87) thin film. A high-resolution surface acoustic wave technique was developed for in situ measurement of film shear moduli. The modulus has narrow maxima at x = 0. 17, 0.22, 0.43, 0.5, 0.63, and 0.72, reflecting short-range ordering and formation of aggregates in amorphous phase. It is proposed that the aggregates correspond… more

Date: August 1, 1993

Creator: Schwarz, R. B. & Rubin, J. B.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Vibrational and electronic properties of clusters and ultrathin films. Progress report

This covers {approximately} 26 months of research. In addition to clusters and thin films, studies of bulk fullerene and amorphous carbon are also reported. Results and activities are reported under the headings: structure of C{sub 60}, dynamics of C{sub 60}, Raman scattering of fullerene-based systems, Bi clusters, and amorphous carbon structure.

Date: May 1, 1993

Creator: Lannin, J. S.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

XRD Technique: A way to disseminate structural changes in iron-based amorphous materials

Prevention of corrosion is a vital goal for the Department of Defense when billions of dollars are spent every year. Corrosion resistant materials have applications in all sort of military vehicles, and more importantly in naval vessels and submarines which come in contact with the seawater. It is known that corrosion resistance property can be improved by the used of structurally designed materials in the amorphous state where the atoms are arranged in a non-periodic fashion and specific atoms… more

Date: May 24, 2007

Creator: Saw, C. K.; Lian, T.; Day, D. & Farmer, J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Diamond-like atomic-scale composite films: Surface properties and stability studied by STM and AFM

Amorphous ``diamond-like/quartz-like`` composites a-(C:H/Si:O) and metal containing a-(C:H/Si:O/Me) constitute a novel class of diamond-related materials with a number of unique bulk and surface properties. In order to gain a more fundamental understanding of the surface properties and stability of these solids we have performed a scanning tunneling and atomic force microscopy investigation of both a-(C:H/Si:O) and a-(C:H/Si:O/Me) films, including the effects of ion bombardment and annealing.

Date: October 1, 1995

Creator: Dorfman, B.; Abraizov, M.; Pollak, F.H.; Eby, R.; Rong, Z.Y.; Strongin, M. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Structural analysis of a completely amorphous {sup 238}Pu-doped zircon by neutron diffraction.

The structure of a completely amorphous zircon was determined by time-of-flight neutron diffraction at Argonne's Intense Pulsed Neutron Source (IPNS). The sample of metamict zircon (ZrSiO{sub 4}),initially doped to 8.85 weight percent {sup 238}Pi, had been completely amorphized by alpha-recoil damage since its synthesis in 1981 at the Pacific Northwest National Laboratory (PNNL). The measured diffraction structure factor, S(Q), indicated a completely amorphous sample, with no signs of residual … more

Date: December 16, 1998

Creator: Fortner, J. A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Fabrication Technology

The mission of the Fabrication Technology thrust area is to have an adequate base of manufacturing technology, not necessarily resident at Lawrence Livermore National Laboratory (LLNL), to conduct the future business of LLNL. The specific goals continue to be to (1) develop an understanding of fundamental fabrication processes; (2) construct general purpose process models that will have wide applicability; (3) document findings and models in journals; (4) transfer technology to LLNL programs, i… more

Date: March 1, 1993

Creator: Blaedel, K. L.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Bulk metallic glass formation in the Pd-Ni-P and Pd-Cu-P alloy systems

Bulk metallic glasses were prepared in the Pd-Ni-P and Pd-Cu-P systems using a fluxing technique. The formation of bulk amorphous Pd-Cu-P alloys was reported here for the first time. For both alloy systems, bulk glass formation requires maintaining the phosphorus content near 20 at.%. In the Pd-Ni-P system, 10-mm diameter amorphous Pd{sub x}Ni{sub 80{minus}x}P{sub 20} rods can be formed for 25 {le} x {le} 60. In the Pd-Cu-P system, 7-mm diameter amorphous Pd{sub x}Cu{sub 80{minus}x}P{sub 20} ro… more

Date: December 11, 1996

Creator: Schwarz, R.B. & He, Y.

Item Type: Report

Partner: UNT Libraries Government Documents Department