These are representative sample records from Science.gov related to your search topic.
For comprehensive and current results, perform a real-time search at Science.gov.
1

Electronic structure of BAs and boride III-V alloys  

SciTech Connect

Boron arsenide, the typically ignored member of the Group-III--V arsenide series BAs-AlAs-GaAs-InAs is found to resemble silicon electronically: its {Gamma} conduction-band minimum is p-like ({Gamma}{sub 15}), not s-like ({Gamma}{sub 1c}), it has an X{sub 1c}-like indirect band gap, and its bond charge is distributed almost equally on the two atoms in the unit cell, exhibiting nearly perfect covalency. The reasons for these are tracked down to the anomalously low atomic p orbital energy in the boron and to the unusually strong s--s repulsion in BAs relative to most other Group-III--V compounds. We find unexpected valence-band offsets of BAs with respect to GaAs and AlAs. The valence-band maximum (VBM) of BAs is significantly higher than that of AlAs, despite the much smaller bond length of BAs, and the VBM of GaAs is only slightly higher than in BAs. These effects result from the unusually strong mixing of the cation and anion states at the VBM. For the BAs-GaAs alloys, we find (i) a relatively small ({approx}3.5 eV) and composition-independent band-gap bowing. This means that while addition of small amounts of nitrogen to GaAs lowers the gap, addition of small amounts of boron to GaAs raises the gap; (ii) boron ''semilocalized'' states in the conduction band (similar to those in GaN-GaAs alloys); and (iii) bulk mixing enthalpies that are smaller than in GaN-GaAs alloys. The unique features of boride Group-III--V alloys offer new opportunities in band-gap engineering.

Hart, Gus L. W.; Zunger, Alex

2000-11-15

2

Method for preparing homogeneous single crystal ternary III-V alloys  

DOEpatents

A method for producing homogeneous, single-crystal III-V ternary alloys of high crystal perfection using a floating crucible system in which the outer crucible holds a ternary alloy of the composition desired to be produced in the crystal and an inner floating crucible having a narrow, melt-passing channel in its bottom wall holds a small quantity of melt of a pseudo-binary liquidus composition that would freeze into the desired crystal composition. The alloy of the floating crucilbe is maintained at a predetermined lower temperature than the alloy of the outer crucible, and a single crystal of the desired homogeneous alloy is pulled out of the floating crucible melt, as melt from the outer crucible flows into a bottom channel of the floating crucible at a rate that corresponds to the rate of growth of the crystal.

Ciszek, Theodore F. (Evergreen, CO)

1991-01-01

3

Method for preparing homogeneous single crystal ternary III-V alloys  

SciTech Connect

A method for producing homogenous single crystal III--V ternary alloys of high crystal perfection using a floating crucible system in which the outer crucible holds a ternary alloy of the composition desired to be produced in the crystal and an inner floating crucible having a narrow, melt-passing channel in its bottom wall holds a small quantity of melt of a pseudo-binary liquidus composition which would freeze into the desired crystal composition. The alloy of the floating crucible is maintained at a predetermined lower temperature than the alloy of the outer crucible, and a single crystal of the desired homogeneous alloy is pulled out of the floating crucible melt, as melt from the outer crucible flows into a bottom channel of the floating crucible at a rate that corresponds to the rate of growth of the crystal.

Ciszek, T.F.

1990-08-14

4

Band parameters for III-V compound semiconductors and their alloys  

NASA Astrophysics Data System (ADS)

We present a comprehensive, up-to-date compilation of band parameters for the technologically important III-V zinc blende and wurtzite compound semiconductors: GaAs, GaSb, GaP, GaN, AlAs, AlSb, AlP, AlN, InAs, InSb, InP, and InN, along with their ternary and quaternary alloys. Based on a review of the existing literature, complete and consistent parameter sets are given for all materials. Emphasizing the quantities required for band structure calculations, we tabulate the direct and indirect energy gaps, spin-orbit, and crystal-field splittings, alloy bowing parameters, effective masses for electrons, heavy, light, and split-off holes, Luttinger parameters, interband momentum matrix elements, and deformation potentials, including temperature and alloy-composition dependences where available. Heterostructure band offsets are also given, on an absolute scale that allows any material to be aligned relative to any other.

Vurgaftman, I.; Meyer, J. R.; Ram-Mohan, L. R.

2001-06-01

5

Defect complexes in III V compounds  

NASA Astrophysics Data System (ADS)

Some technically important examples of defect complexes in III-V semi-conductors will be briefly discussed in this paper. It is now clear that the midgap donor level in GaAs, often referred to as EL2, is not as previously assumed due to substitutional oxygen on an As site, but is a defect complex involving a Ga vacancy. This defect makes it possible to grow undoped semi-insulating GaAs for the production of integrated circuits. Defect reactions can be monitored by studying the luminescence from ZnO pairs, which are used to obtain red light from GaP LED's. The A and B levels often present in liquid phase GaAs are identified as the GaAs antisite. A normally unwanted but frequent contaminant in III-V semiconductors is Cu. We now know that the two copper-related levels which may appear in all large bandgap III-V's are not two levels of the same defect. At least one of the defects therefore has to be a complex. Studies in series of alloys demonstrate that the copper-related levels have the same defect origin in GaP, InP, GaAs and AlAs.

Ledebo, Lars-Åke

6

Envelope Function Approximation (EFA) Bandstructure Calculations for III-V Non-square Stepped Alloy Quantum Wells Incorporating Ultra-narrow (˜5Å) Epitaxial Layers  

NASA Astrophysics Data System (ADS)

We describe Envelope Function Approximation (EFA) bandstructure calculations based on a 4-band electron (EL), heavy-hole (HH), light-hole (LH) and split-off hole (SO) effective mass Hamiltonian, with Burt-Foreman hermitianisation, which can handle III-V quantum well structures that incorporate ultra-narrow epi-layers. The model takes into account the coupling of EL, HH, LH and SO bands and is suitable for describing quantum wells tuned to the 1.0 - 1.55 ?m window exploited by optical fibre communication devices. We have used the multi-band solver to calculate the bandstructure of an illustrative InGaAsSb-AlGaSb non-square quantum well that incorporates 6Å potential “spikes” in its well region. Calculations based on the Burt-Foreman hermitianised Hamiltonian and those based on a Hamiltonian with standard “symmetrised” hermitianisation are presented and compared. When coupling to the conduction band is excluded from the calculation, the latter formulation leads to anomalous electron-like curvature of the dispersion curves for our spiked non-square quantum well structure.

Kaduki, K. A.; Batty, W.

2000-02-01

7

Synthesis of III-V nitride nanowires with controlled structure, morphology, and composition  

E-print Network

The III-V nitride materials system offers tunable electronic and optical properties that can be tailored for specific electronic and optoelectronic applications by varying the (In,Ga,Al)N alloy composition. While nitride ...

Crawford, Samuel Curtis

2014-01-01

8

Antimony Based III-V Thermophotovoltaic Devices  

SciTech Connect

Antimony-based III-V thermophotovoltaic (TPV) cells are attractive converters for systems with low radiator temperature around 1100 to 1700 K, since these cells potentially can be spectrally matched to the thermal source. Cells under development include GaSb and the lattice-matched GaInAsSb/GaSb and InPAsSb/InAs quaternary systems. GaSb cell technology is the most mature, owing in part to the relative ease in preparation of the binary alloy compared to quaternary GaInAsSb and InPAsSb alloys. Device performance of 0.7-eV GaSb cells exceeds 90% of the practical limit. GaInAsSb TPV cells have been the primary focus of recent research, and cells with energy gap E{sub g} ranging from {approx}0.6 to 0.49 eV have been demonstrated. Quantum efficiency and fill factor approach theoretical limits. Open-circuit voltage factor is as high as 87% of the practical limit for the higher-E{sub g} cells, but degrades to below 80% with decreasing E{sub g} of the alloy, which might be due to Auger recombination. InPAsSb cells are the least studied, and a cell with E{sub g} = 0.45-eV has extended spectral response out to 4.3 {micro}m. This paper briefly reviews the main contributions that have been made for antimonide-based TPV cells, and suggests additional studies for further performance enhancements.

CA Wang

2004-06-09

9

Reliability issues in III–V compound semiconductor devices: optical devices and GaAs-based HBTs  

Microsoft Academic Search

This paper reviews the current status of reliability issues in III–V optical devices, semiconductor lasers and light emitting diodes, and GaAs-based heterojunction bipolar transistors (HBTs). First, material issues in III–V alloy semiconductors and our current understanding of degradation in III–V semiconductor lasers and light emitting diodes are systematically presented. Generation of defects and thermal instability are among these issues for

Osamu Ueda

1999-01-01

10

Hybrid III-V/silicon lasers  

NASA Astrophysics Data System (ADS)

The lack of potent integrated light emitters is one of the bottlenecks that have so far hindered the silicon photonics platform from revolutionizing the communication market. Photonic circuits with integrated light sources have the potential to address a wide range of applications from short-distance data communication to long-haul optical transmission. Notably, the integration of lasers would allow saving large assembly costs and reduce the footprint of optoelectronic products by combining photonic and microelectronic functionalities on a single chip. Since silicon and germanium-based sources are still in their infancy, hybrid approaches using III-V semiconductor materials are currently pursued by several research laboratories in academia as well as in industry. In this paper we review recent developments of hybrid III-V/silicon lasers and discuss the advantages and drawbacks of several integration schemes. The integration approach followed in our laboratory makes use of wafer-bonded III-V material on structured silicon-on-insulator substrates and is based on adiabatic mode transfers between silicon and III-V waveguides. We will highlight some of the most interesting results from devices such as wavelength-tunable lasers and AWG lasers. The good performance demonstrates that an efficient mode transfer can be achieved between III-V and silicon waveguides and encourages further research efforts in this direction.

Kaspar, P.; Jany, C.; Le Liepvre, A.; Accard, A.; Lamponi, M.; Make, D.; Levaufre, G.; Girard, N.; Lelarge, F.; Shen, A.; Charbonnier, P.; Mallecot, F.; Duan, G.-H.; Gentner, J.-.; Fedeli, J.-M.; Olivier, S.; Descos, A.; Ben Bakir, B.; Messaoudene, S.; Bordel, D.; Malhouitre, S.; Kopp, C.; Menezo, S.

2014-05-01

11

Preparation of III-V semiconductor nanocrystals  

DOEpatents

Nanometer-scale crystals of III-V semiconductors are disclosed. They are prepared by reacting a group III metal source with a group V anion source in a liquid phase at elevated temperature in the presence of a crystallite growth terminator such as pyridine or quinoline. 4 figs.

Alivisatos, A.P.; Olshavsky, M.A.

1996-04-09

12

Preparation of III-V semiconductor nanocrystals  

DOEpatents

Nanometer-scale crystals of III-V semiconductors are disclosed, They are prepared by reacting a group III metal source with a group V anion source in a liquid phase at elevated temperature in the presence of a crystallite growth terminator such as pyridine or quinoline.

Alivisatos, A. Paul (Berkeley, CA); Olshavsky, Michael A. (Brunswick, OH)

1996-01-01

13

Photodetectors using III-V nitrides  

DOEpatents

A bandpass photodetector using a III-V nitride and having predetermined electrical properties. The bandpass photodetector detects electromagnetic radiation between a lower transition wavelength and an upper transition wavelength. That detector comprises two low pass photodetectors. The response of the two low pass photodetectors is subtracted to yield a response signal.

Moustakas, Theodore D. (Dover, MA)

1998-01-01

14

Photodetectors using III-V nitrides  

DOEpatents

A bandpass photodetector using a III-V nitride and having predetermined electrical properties is disclosed. The bandpass photodetector detects electromagnetic radiation between a lower transition wavelength and an upper transition wavelength. That detector comprises two low pass photodetectors. The response of the two low pass photodetectors is subtracted to yield a response signal. 24 figs.

Moustakas, T.D.

1998-12-08

15

Buildup of III-V-compound semiconductor heterojunctions: Structural and electronic properties of monolayer-thick III-V overlayers on III-V substrates  

Microsoft Academic Search

We report an extensive study of the first stages of the buildup by molecular-beam epitaxy of III-V-compound semiconductor heterojunctions (AlAs, InAs, and GaAs with each other, and GaAs\\/GaP and InAs\\/InP). Surface-sensitive techniques have been applied in situ, first to yield information on the geometry and crystal structure of monolayer-thick overlayers of a III-V compound grown upon another III-V substrate. For

J. M. Moison; C. Guille; M. van Rompay; F. Barthe; F. Houzay; M. Bensoussan

1989-01-01

16

Progress in III-V materials technology  

NASA Astrophysics Data System (ADS)

Compound semiconductors, in the form of GaAs and InP have achieved major commercial significance in areas of application such as mobile communications, displays and telecoms and offer a versatility of function beyond the capabilities of Si. III-V compounds, and in particular GaAs, have since their early development been the subject of defence related interest. Support from this sector established the basic materials technologies and nurtured development up until their commercial breakthrough into consumer products. GaAs, for example, now provides essential components for mobile phones and CD / DVD players. An overview is presented of the crystal growth and processing methods used in the manufacture of these materials. Current state of the art characteristics on crystal form and quality are discussed, together with the evolution of single crystal growth techniques. Consideration is given to how these principal compounds together with the minor materials, InSb, GaSb and InAs are employed in diverse applications over a broad spectral range, together with information on markets and future perspectives.

Grant, Ian R.

2004-12-01

17

High rate ECR etching of III-V nitride materials.  

National Technical Information Service (NTIS)

The III-V nitride compound semiconductors are attracting considerable attention for blue and ultraviolet light emitting diodes (LEDs) and lasers as well as high temperature electronics due to their wide band gaps and high dielectric constants. The recent ...

R. J. Shul, A. J. Howard, S. P. Kilcoyne, S. J. Pearton, C. R. Abernathy

1994-01-01

18

Quantum capacitance in scaled down III-V FETs  

E-print Network

As Si CMOS approaches the end of the roadmap, finding a new transistor technology that allows the extension of Moore's law has become a technical problem of great significance. Among the various candidates, III-V-based ...

Jin, Donghyun

2010-01-01

19

Progress Towards III-V Photovoltaics on Flexible Substrates  

NASA Technical Reports Server (NTRS)

Presented here is the recent progress of the NASA Glenn Research Center OMVPE group's efforts in the development of high efficiency thin-film polycrystalline III-V photovoltaics on optimum substrates. By using bulk polycrystalline germanium (Ge) films, devices of high efficiency and low mass will be developed and incorporated onto low-cost flexible substrates. Our progress towards the integration of high efficiency polycrystalline III-V devices and recrystallized Ge films on thin metal foils is discussed.

McNatt, Jeremiah S.; Pal, AnnaMaria T.; Clark, Eric B.; Sayir, Ali; Raffaelle, Ryne P.; Bailey, Christopher G.; Hubbard, Seth M.; Maurer, William F.; Fritzemeier, Les

2008-01-01

20

Spontaneous polarization and piezoelectric constants of III-V nitrides  

Microsoft Academic Search

The spontaneous polarization, dynamical Born charges, and piezoelectric constants of the III-V nitrides AlN, GaN, and InN are studied ab initio using the Berry-phase approach to polarization in solids. The piezoelectric constants are found to be up to ten times larger than in conventional III-V and II-VI semiconductor compounds, and comparable to those of ZnO. Further properties at variance with

Fabio Bernardini; Vincenzo Fiorentini; David Vanderbilt

1997-01-01

21

Luminescence properties of erbium in III V compound semiconductors  

NASA Astrophysics Data System (ADS)

Optoelectronic materials doped with Er atoms are receiving widespread attentions due to their impact on optical communication systems operating at 1.54 ?m. Optical amplifiers based on Er-doped fibers have demonstrated major improvements in link distance, data rates and reduced needs for signal regeneration. III-V semiconductors doped with Er offer the prospect of very stable, temperature-insensitive, laser diodes emitting at 1.54 ?m. This paper provides a review of the luminescence characteristics of III-V semiconductors doped with Er atoms. Aspects of Er incorporation in the III-V crystal host, photoluminescence properties, and prototype electroluminescent devices are addressed. Details of some of the first observations of photoluminescence of Er atoms in III-V nitride semiconductors, in particular GaN epilayers, are discussed. The GaN epilayers were optically excited using an argon-ion laser and spectra, centered at 1.54 ?m, were observed at 6, 77 and 300 K. The spectra display many of the allowed transitions typical of the Er 3+ configuration and are nearly as intense at room temperature as at 77K. This result indicates that the wide bandgap III-V semiconductors may be ideal host materials for Er-doped electroluminescent devices.

Zavada, J. M.; Duhua Zhang

1995-07-01

22

III-V semiconductor solid solution single crystal growth  

NASA Technical Reports Server (NTRS)

The feasibility and desirability of space growth of bulk IR semiconductor crystals for use as substrates for epitaxial IR detector material were researched. A III-V ternary compound (GaInSb) and a II-VI binary compound were considered. Vapor epitaxy and quaternary epitaxy techniques were found to be sufficient to permit the use of ground based binary III-V crystals for all major device applications. Float zoning of CdTe was found to be a potentially successful approach to obtaining high quality substrate material, but further experiments were required.

Gertner, E. R.

1982-01-01

23

Approaches for III/V Photonics on Si  

SciTech Connect

We investigated different approaches to overcome difficulties in III/V-on-Si heteroepitaxy, namely growth on compliant substrates and virtual Ge substrates, both realized on top of Si substrates, and in addition, directly on Si. The prospect of this work was the realization of a light emitter on standard Si(100) substrate, capable of being integrated in established industrial processes.

Wiesner, M.; Schulz, W.-M.; Rossbach, R.; Jetter, M.; Michler, P. [Institut fuer Halbleiteroptik und Funktionelle Grenzflaechen, University of Stuttgart, Stuttgart, Germany and Stuttgart Research Center of Photonic Engineering (SCoPE) (Germany); Angelopoulos, E. A.; Burghartz, J. N. [Institut fuer Mikroelektronik Stuttgart (IMS CHIPS), Stuttgart (Germany); Werner, J.; Oehme, M.; Schulze, J. [Institut fuer Halbleitertechnik, University of Stuttgart, Germany and Stuttgart Research Center of Photonic Engineering (SCoPE) (Germany)

2011-12-23

24

Bulk crystal growth of antimonide based III-V compounds for thermophotovoltaics applications  

SciTech Connect

In this paper, the bulk growth of crack-free GaInSb and single phase GaInAsSb alloys are presented. A new class of III-V quasi-binary [A{sub III}B{sub V}]{sub 12{minus}x}[C{sub III}D{sub V}]{sub x} semiconductor alloys has been synthesized and bulk crystals grown from the melt for the first time. The present investigation is focused on the quasi-binary alloy (GaSb){sub 1{minus}x}(InAs){sub x} (0 < x < 0.05) due to its importance for thermophotovoltaic applications. The structural properties of this melt-grown quasi-binary alloy are found to be significantly different from the conventional quaternary compound Ga{sub 1{minus}x}In{sub x}As{sub y}Sb{sub 1{minus}y} with composition x = y. Synthesis and growth procedures are discussed. For the growth of ternary alloys, it was demonstrated that forced convection or mixing in the melt during directional solidification of In{sub x}Ga{sub 1{minus}x}Sb (0 < x < 0.1) significantly reduces cracks in the crystals.

Dutta, P.S.; Ostrogorsky, A.G.; Gutmann, R.J. [Rensselaer Polytechnic Inst., Troy, NY (United States)

1998-10-01

25

Investigation of new semiinsulating behavior of III-V compounds  

NASA Technical Reports Server (NTRS)

The investigation of defect interactions and properties related to semiinsulating behavior of III-V semiconductors resulted in about twenty original publications, six doctoral thesis, one masters thesis and numerous conference presentations. The studies of new compensation mechanisms involving transition metal impurities have defined direct effects associated with deep donor/acceptor levels acting as compensating centers. Electrical and optical properties of vanadium and titanium levels were determined in GaAs, InP and also in ternary compounds InGaAs. The experimental data provided basis for the verification of chemical trends and the VRBE method. They also defined compositional range for III-V mixed crystals whereby semiinsulating behavior can be achieved using transition elements deep levels and a suitable codoping with shallow donor/acceptor impurities.

Lagowski, Jacek

1990-01-01

26

Subnanometer scale characterization of III-V-heterostructures  

SciTech Connect

Heterostructures based on III-V semiconductors play a dominant role for the production of optoelectronic /1/ and electronic high-speed or high-frequency /2/ devices. The necessary band-gap engineering is achieved by optimized growth procedures which allow to change the chemical composition and the crystal structure (e.g., strain or ordering) on the subnanometer scale. The evaluation of individual heterointerfaces with respect to chemical composition and crystal structure requires characterization techniques which offer the necessary high spatial resolution. Scanning transmission electron microscopy (STEM) offers several of such quantitative techniques. It is the intention of this paper to demonstrate the capabilities of STEM in the subnanometer characterization of III-V-heterostructures based on InP-substrates. Additionally, the data obtained from nanocharacterization can be correlated to device performance.

Lakner, H. [Gerhard-Mercator-Univ. Duisburg (Germany). Werkstoffe der Elektrotechnik

1996-12-31

27

Novel integration technique for silicon/III-V hybrid laser.  

PubMed

Integrated semiconductor lasers on silicon are one of the most crucial devices to enable low-cost silicon photonic integrated circuits for high-bandwidth optic communications and interconnects. While optical amplifiers and lasers are typically realized in III-V waveguide structures, it is beneficial to have an integration approach which allows flexible and efficient coupling of light between III-V gain media and silicon waveguides. In this paper, we propose and demonstrate a novel fabrication technique and associated transition structure to realize integrated lasers without the constraints of other critical processing parameters such as the starting silicon layer thicknesses. This technique employs epitaxial growth of silicon in a pre-defined trench with taper structures. We fabricate and demonstrate a long-cavity hybrid laser with a narrow linewidth of 130 kHz and an output power of 1.5 mW using the proposed technique. PMID:25401832

Dong, Po; Hu, Ting-Chen; Liow, Tsung-Yang; Chen, Young-Kai; Xie, Chongjin; Luo, Xianshu; Lo, Guo-Qiang; Kopf, Rose; Tate, Alaric

2014-11-01

28

FOREWORD: The physics of III-V nitrides The physics of III-V nitrides  

NASA Astrophysics Data System (ADS)

The evolution of semiconductor physics is driven by the increasing sophistication of the art of crystal growing and fabrication techniques. From Ge at the birth of the transistor, possibly the purest material ever grown, through Si, the work-horse of the crystal revolution, to the III-Vs, whose optical properties opened up a second front, namely, optoelectronics. Crystal growth with monolayer control gave us quantum wells, superlattices, quantum wires and quantum dots, along with the quantum Hall effect and quantized resistance. The potential for high-power devices triggered interest in the III-V nitrides with their large bandgaps. The nitrides mostly crystallize in the hexagonal form, and this has introduced the phenomenon of spontaneous polarization into mainstream semiconductor physics. Its effect manifests itself in huge electric fields in heterostructures like AlGaN/GaN which, in turn, causes the induction of substantial electron populations in the channel of a HFET without the need for doping. High-power microwave transistors have been successfully fabricated, even though there are features associated with spontaneous polarization that still needs clarifying. Another strange effect is the large electron population on the surface of InN. The lack of a suitable substrate for growing GaN has meant that the dislocation density is higher than we would wish, but that situation is expected to steadily improve. Given the current interest in the physics of nitrides, it is natural to come across a special issue devoted to this topic. The difficulty presented by the surface layer in InN in the attempt to measure transport properties is discussed in the paper by King et al. A property that can affect transport is the lifetime of optical phonons and its dependence on electron density. Measurements of phonon lifetime in InN are reported by Tsen and Ferry, and in GaN channels, via the measure of hot-electron fluctuations, by Matulionis. The dependence on electron density is thought to be associated with the coupling of plasma and phonon modes, and this is discussed by Dyson. The intrinsic cause of phonon decay is the anharmonic interaction involving three phonons, and this process is described for zinc blende BN and hexagonal AlN, GaN and InN by Srivastava. The principal electron scattering mechanism at room temperature is associated with the interaction with polar optical modes. At high fields, transfer to the upper conduction-band valleys can take place and this involves the deformation-potential interaction. Deformation potentials have been derived by Yamakawa et al for GaN, and they have been incorporated into a cellular Monte Carlo simulation to describe high-field transport. In high-power devices, thermal as well as electronic transport is important. The thermal conductivity of the substrate of devices is a vital factor, and the possible use of AlN ceramics is discussed by AlShaikhi and Srivastarva. A striking device based on a zinc blende superlattice is the quantum cascade laser. Exploiting intersubband transitions in the AlN/GaN superlattice for the high-speed detection of infrared light is described by Hofstetter et al, clearly a first step towards a nitride based quantum cascade laser. In bulk material the displacement of As by N that transforms GaAs to GaN produces a huge change in properties. Adding a small amount of N to GaAs might be expected to produce a gradual more-or-less linear shift towards the properties of GaN, but this turns out to be far from the case. The strange properties of dilute nitrides have intrigued many workers in recent years. Its curious bandstructure suggested that hot-electron transport could exhibit a negative differential resistance, and a report on this topic can be found in the article by Patane et al A comprehensive study of transport of electrons and holes in dilute nitride/GaAs quantum wells is reported by Sun et al. An unusual new device—a spin filter—is presaged by the work of Zhao et al on spin-dependent recombination, controllable by adjusting the N content. Answers to a numbe

Ridley, B. K.

2009-04-01

29

Enhanced performance of optical sources in III-V materials using photonic crystals  

E-print Network

This thesis applies the unique properties of photonic crystals to enhance the performance of several III-V optical sources. Emphasis is placed on the primary limitation of using photonic crystals for III-V optical sources: ...

Erchak, Alexei A. (Alexei Andrew), 1976-

2002-01-01

30

Effective electron mass in quantum wires of III-V, ternary and quaternary materials.  

PubMed

In this paper, an attempt is made to study the effective electron mass (EEM) in Quantum wires (QWs) of III-V, ternary and quaternary materials on the basis of three and two band models of Kane within the framework of k x p formalism. It has been found, taking QWs of InAs, InSb, GaAs, Hg(1-x)Cd(x)Te and In(1-x)Ga(x)As(1-y)P(t) that the 1D EEM increases with electron concentration per unit length and decreases with increasing film thickness respectively. For ternary and quaternary materials the EEM increases with increase in alloy composition. Under certain special conditions all the results for all the 1-D materials get simplified into the well known parabolic energy bands and thus confirming the compatibility test. The results of this paper find two applications in the fields of nanoscience and technology. PMID:23447948

Paitya, N; Ghatak, K P

2012-12-01

31

III-V Growth on Silicon Toward a Multijunction Cell  

SciTech Connect

A III-V on Si multijunction solar cell promises high efficiency at relatively low cost. The challenges to epitaxial growth of high-quality III-Vs on Si, though, are extensive. Lattice-matched (LM) dilute-nitride GaNPAs solar cells have been grown on Si, but their performance is limited by defects related to the nitrogen. Advances in the growth of lattice-mismatched (LMM) materials make more traditional III-Vs, such as GaInP and GaAsP, very attractive for use in multijunction solar cells on silicon.

Geisz, J.; Olson, J.; McMahon, W.; Friedman, D.; Kibbler, A.; Kramer, C.; Young, M.; Duda, A.; Ward, S.; Ptak, A.; Kurtz, S.; Wanlass, M.; Ahrenkiel, P.; Jiang, C. S.; Moutinho, H.; Norman, A.; Jones, K.; Romero, M.; Reedy, B.

2005-11-01

32

Supermode Silicon/III--V Lasers and Circular Bragg Lasers  

NASA Astrophysics Data System (ADS)

Semiconductor lasers are arguably the most important component in optical communications. This thesis investigates two types of semiconductor lasers that are useful in integrated optics. Part I focuses on supermode Si/III-V lasers and Part II discusses circular Bragg lasers for the application as surface-emitting lasers. Just as optical fibers have largely replaced the traditional copper wires in long-distance applications, people started to consider incorporating optical communication onto chips, primarily because the increased ohmic heating and RC delay associated with the metal interconnection prevent further increase in the data-processing rate. Si is well known to be the integration platform for electronics, and III-V materials (GaAs, InP, etc.) are efficient light emitters. It is natural to bring them together to realize the on-chip optical communication. Among various Si/III-V integration schemes the most promising is the hybrid Si evanescent platform in which a wafer-bonding technique that is compatible with current CMOS processing is used to bring Si and III-V materials together. Part I of this thesis focuses on the application of a novel mode-control method to such hybrid waveguide system to enhance the modal gain, which makes for more efficient and, most importantly, shorter devices that may hold the key to the photonics/electronics integration. The supermode theory is derived, the shortest adiabatic mode transformer is theoretically and numerically studied, and the device design and fabrication are presented, followed by the experimental demonstration of the performance enhancement in the mode-controlled Si/InGaAsP laser devices. Vertical cavity surface emitting lasers are a commercial light source for optical communications, but their single-modedness and good emission pattern are guaranteed only over a very small mode area (diameter of several microns) thus they have limitations in high-power applications. As an alternative, circular Bragg lasers can be designed as a superior surface emitting laser that produces high output power with good beam quality. Part II of this thesis presents a comprehensive and systematic theoretical study on the surface-emitting Hankel-phased circular Bragg lasers in various geometries. The analytical and numerical mode-solving methods will be described, followed by near- and above-threshold modal analyses.

Sun, Xiankai

33

III-V nitrides for electronic and optoelectronic applications  

NASA Astrophysics Data System (ADS)

Recent developments in III-V nitride thin-film materials for electronic and optoelectronic applications are reviewed. The problems that are limiting the development of these materials are discussed. The properties of cubic BN, AlN, GaN, AlN/GaN solid solutions and heterostructures, and InN are discussed. The lack of a suitable substrate, with the possible exception of SiC for AlN, is a problem of considerable magnitude, compounded by the presence of shallow donor bands in GaN and InN. The question of whether these vacancies occur as a result of intrinsic or extrinsic nonstoichiometry has not been answered, but recent advances in the fabrication of p-type GaN and a p-n junction LEDs via the electron beam stimulation of the Mg dopant are very encouraging. Self-compensation effects, similar to those observed in ZnO and ZnSe, may not be present in the III-V nitrides, since cubic BN (cBN) AlN, and now GaN have been reportedly doped both n- and p-type.

Davis, Robert F.

1991-05-01

34

III-V nanowire arrays: growth and light interaction.  

PubMed

Semiconductor nanowire arrays are reproducible and rational platforms for the realization of high performing designs of light emitting diodes and photovoltaic devices. In this paper we present an overview of the growth challenges of III-V nanowire arrays obtained by molecular beam epitaxy and the design of III-V nanowire arrays on silicon for solar cells. While InAs tends to grow in a relatively straightforward manner on patterned (111)Si substrates, GaAs nanowires remain more challenging; success depends on the cleaning steps, annealing procedure, pattern design and mask thickness. Nanowire arrays might also be used for next generation solar cells. We discuss the photonic effects derived from the vertical configuration of nanowires standing on a substrate and how these are beneficial for photovoltaics. Finally, due to the special interaction of light with standing nanowires we also show that the Raman scattering properties of standing nanowires are modified. This result is important for fundamental studies on the structural and functional properties of nanowires. PMID:24334728

Heiss, M; Russo-Averchi, E; Dalmau-Mallorquí, A; Tütüncüo?lu, G; Matteini, F; Rüffer, D; Conesa-Boj, S; Demichel, O; Alarcon-Lladó, E; Fontcuberta i Morral, A

2014-01-10

35

Surface assessment after removing III–V layer on III–V/silicon-on-insulator wafer fabricated by plasma activated bonding  

NASA Astrophysics Data System (ADS)

The partial removal of the III–V layers of a III–V/silicon-on-insulator hybrid wafer was investigated to realize III–V/Si hybrid photonic integrated circuits. Using transmission electron microscopy, we found that an amorphous layer was generated at the interface of a III–V/Si wafer fabricated by N2-plasma-activated bonding. In order to remove the III–V layers including the amorphous layers without damage to the Si surface, several etching processes were carried out, and the surface conditions were evaluated by X-ray photoelectron spectroscopy. As a result, we demonstrated comparable propagation losses in Si wire waveguides with and without the bonding/removal processes.

Suzuki, Junichi; Hayashi, Yusuke; Kuno, Yuki; Kang, JoonHyun; Amemiya, Tomohiro; Nishiyama, Nobuhiko; Arai, Shigehisa

2014-11-01

36

High rate ECR etching of III-V nitride materials  

NASA Astrophysics Data System (ADS)

The III-V nitride compound semiconductors are attracting considerable attention for blue and ultraviolet light emitting diodes (LED's) and lasers as well as high temperature electronics due to their wide band gaps and high dielectric constants. The recent progress observed in the growth of these materials has not been matched by progress in processing techniques to fabricate more highly sophisticated devices. Patterning these materials has been especially difficult due to the relatively inert chemical nature of the group-III nitrides. The authors review dry etch techniques which have been used to pattern these materials including electron cyclotron resonance (ECR), reactive ion etch (RIE), and chemically assisted ion beam etching (CAIBE). ECR etch rates greater than 3800 A/min for InN, 3500 A/min for GaN, and 1170 A/min for AlN are reported. Etch anisotropy, surface morphology, and near-surface stoichiometry are discussed.

Shul, R. J.; Howard, A. J.; Kilcoyne, S. P.; Pearton, S. J.; Abernathy, C. R.; Vartuli, C. B.; Barnes, P. A.; Bozack, M. J.

37

Characteristics of III-V Semiconductor Devices at High Temperature  

NASA Technical Reports Server (NTRS)

This paper presents the development of III-V based pseudomorphic high electron mobility transistors (PHEMT's) designed to operate over the temperature range 77 to 473 K (-196 to 200 C). These devices have a pseudomorphic undoped InGaAs channel that is sandwiched between an AlGaAs spacer and a buffer layer; gate widths of 200, 400, 1600, and 3200 micrometers; and a gate length of 2 micrometers. Measurements were performed at both room temperature and 473 K (200 C) and show that the drain current decreases by 30 percent and the gate current increases to about 9 microns A (at a reverse bias of -1.5 V) at the higher temperature. These devices have a maximum DC power dissipation of about 4.5 W and a breakdown voltage of about 16 V.

Simons, Rainee N.; Young, Paul G.; Taub, Susan R.; Alterovitz, Samuel A.

1994-01-01

38

Binary III-V semiconductor core optical fiber.  

PubMed

For the first time to the best of our knowledge a glass-clad optical fiber comprising a crystalline binary III-V semiconductor core has been fabricated. More specifically, a phosphate glass-clad fiber containing an indium antimonide (InSb) core was drawn using a molten core approach. The core was found to be highly crystalline with some oxygen and phosphorus diffusing in from the cladding glass. While optical transmission measurements were unable to be made, most likely due to free carrier absorption associated with the conductivity of the core, this work constitutes a proof-of-concept that optical fibers comprising semiconductor cores of higher crystallographic complexity than previously realized can be drawn using conventional fiber fabrication techniques. Such binary semiconductors may open the door to future fiber-based nonlinear devices. PMID:20389508

Ballato, John; Hawkins, Thomas; Foy, Paul; McMillen, Colin; Burka, Laura; Reppert, Jason; Podila, Ramakrishna; Rao, A M; Rice, Robert R

2010-03-01

39

III-V nitride semiconductors for solar hydrogen production  

NASA Astrophysics Data System (ADS)

Photoelectrochemical cells are devices that can convert solar radiation to hydrogen gas through a water decomposition process. In this process, energy is converted from incident photons to the bonds of the generated H2 molecules. The solar radiation absorption, electron-hole pair splitting, and photoelectrolysis half reactions all occur in the vicinity of the electrode-electrolyte interface. As a result, engineering the electrode material and its interaction with the electrolyte is important in investigating and improving the energy conversion process in these devices. III-V nitride materials are promising candidates for photoelectrochemical energy applications. We demonstrate solar-to-hydrogen conversion in these cells using p-type GaN and n-type InGaN as a photocathode and photoanode material, respectively. Additionally, we demonstrate heteroepitaxial MOCVD growth of GaP on Si, enabling future work in developing GaPN as a photocathode material.

Parameshwaran, Vijay; Gallinat, Chad; Enck, Ryan W.; Sampath, Anand V.; Shen, Paul H.; Kuykendall, Tevye; Aloni, Shaul; Wraback, Michael; Clemens, Bruce M.

2012-06-01

40

III-V Nanowire Array Growth by Selective Area Epitaxy  

SciTech Connect

III-V semiconductor nanowires are unique material phase due to their high aspect ratio, large surface area, and strong quantum confinement. This affords the opportunity to control charge transport and optical properties for electrical and photonic applications. Nanoscale selective area metalorganic chemical vapor deposition growth (NS-SAG) is a promising technique to maximize control of nanowire diameter and position, which are essential for device application. In this work, InP and GaAs nanowire arrays are grown by NS-SAG. We observe enhanced sidewall growth and array uniformity disorder in high growth rate condition. Disorder in surface morphology and array uniformity of InP nanowire array is explained by enhanced growth on the sidewall and stacking faults. We also find that AsH{sub 3} decomposition on the sidewall affects the growth behavior of GaAs nanowire arrays.

Chu, Hyung-Joon; Stewart, Lawrence [Ming Hsieh Department of Electrical Engineering, University of Southern California (United States); Yeh, Tingwei [Mork Family Department of Chemical Engineering and Material Science, University of Southern California 3651 Watt Way, VHE-314, Los Angeles, CA90089 (United States); Dapkus, P. Daniel [Ming Hsieh Department of Electrical Engineering, University of Southern California (United States); Mork Family Department of Chemical Engineering and Material Science, University of Southern California 3651 Watt Way, VHE-314, Los Angeles, CA90089 (United States)

2011-12-23

41

Bulk III-V compound semiconductor crystal growth  

SciTech Connect

This paper discusses the production of III-V compound semiconductor substrates characterized by structural perfection and chemical homogeneity. Special attention is given to the use of vertical-gradient-freeze (VGF) technique for producing large high-quality GaP, InP, and GaAs crystals. The characteristics of VGF-grown GaAs crystals are described, including the dislocation-count distribution, etch-pit density, and electrical properties. The VGF-grown crystals have very low levels of crystalline defects distributed uniformly throughout the crystal; growth striations are planar and are greatly reduced in comparison with those observed in materials produced by the liquid-encapsulated Czochralski method. Yields obtained with the VGF method compare favorably with those of other commercial crystal-growth processes. 9 refs.

Clemans, J.E.; Ejim, T.I.; Gault, W.A.; Monberg, E.M. (AT and T Bell Laboratories, Princeton, NJ (USA) AT and T Microelectronics, Reading, PA (USA) AT and T Bell Laboratories, Murray Hill, NJ (USA))

1989-02-01

42

III-V Compound Detectors for CO2 DIAL Measurements  

NASA Technical Reports Server (NTRS)

Profiling of atmospheric carbon dioxide (CO2) is important for understanding the natural carbon cycle on Earth and its influence on global warming and climate change. Differential absorption lidar is a powerful remote sensing technique used for profiling and monitoring atmospheric constituents. Recently there has been an interest to apply this technique, at the 2 m wavelength, for investigating atmospheric CO2. This drives the need for high quality detectors at this wavelength. Although 2 m detectors are commercially available, the quest for a better detector is still on. The detector performance, regarding quantum efficiency, gain and associated noise, affects the DIAL signal-to-noise ratio and background signal, thereby influencing the instrument sensitivity and dynamic range. Detectors based on the III-V based compound materials shows a strong potential for such application. In this paper the detector requirements for a long range CO2 DIAL profiles will be discussed. These requirements were compared to newly developed III-V compound infrared detectors. The performance of ternary InGaSb pn junction devices will be presented using different substrates, as well as quaternary InGaAsSb npn structure. The performance study was based on experimental characterization of the devices dark current, spectral response, gain and noise. The final results are compared to the current state-of-the-art InGaAs technology. Npn phototransistor structure showed the best performance, regarding the internal gain and therefore the device signal-to-noise ratio. 2-micrometers detectivity as high as 3.9 x 10(exp 11) cmHz(sup 1/2)/W was obtained at a temperature of -20 C and 4 V bias voltage. This corresponds to a responsivity of 2650 A/W with about 60% quantum efficiency.

Refaat, Tamer F.; Abedin, M. Nurul; Sulima, Oleg V.; Ismail, Syed; Singh, Upendra N.

2005-01-01

43

Hydrogen-impurity complexes in III V semiconductors  

NASA Astrophysics Data System (ADS)

This review summarizes the presently available knowledge concerning hydrogen-impurity complexes in III-V compounds. The impurities form shallow acceptors on group III sites (Be, Zn, Cd) and on group V sites (C, Si, Ge) as well as shallow donors on group V sites (S, Se, Te) and on group III sites (Si, Sn). These complexes are mainly revealed by their hydrogen stretching modes. Therefore, nearly all information about their structure and dynamic properties is derived from vibrational spectroscopy. The complexes of shallow impurities with hydrogen have been most extensively investigated in GaAs, GaP and InP. This holds also for Mg-H in GaN. The complexes exhibit a different microscopic structure, which is discussed in detail. The isoelectronic impurity nitrogen, complexed with one hydrogen atom, is investigated in detail in GaAs and GaP. Those complexes can exist in different charge states. The experimental results such as vibrational frequencies, the microscopic structure and the activation energy for reorientation for many of these complexes are in very good agreement with results of ab initio calculations. Different types of oxygen-hydrogen complexes in GaAs and GaP are described, with one hydrogen atom or two hydrogen atoms bonded to oxygen. Three of these complexes in GaAs were found to be electrically active.

Ulrici, W.

2004-12-01

44

Hot-hole lasers in III--V semiconductors  

SciTech Connect

Following the success of p-Ge hot-hole lasers, there is potential for using other semiconductor materials, notably III--V materials such as GaAs and InSb. Previous analysis had suggested that a large effective mass ratio between the heavy and light holes is advantageous, which implies that InSb would make an excellent hot-hole laser. Using our Monte Carlo simulation of both GaAs and InSb hot-hole lasers in combination with a rate equation model, we see that previously accepted criteria used to predict performance are not always reliable, and we suggest suitable alternatives. The simulation results include gain and gain bandwidth as a function of field strength and laser frequency, and alternative field orientations and photon polarizations are considered. Comparisons are made with bulk 1-Ge systems. The optimum conditions predicted by our simulation could then be used in the design of quantum-well hot-hole lasers. {copyright} 2001 American Institute of Physics.

Kinsler, P.; Wenckebach, W. Th.

2001-08-15

45

III-V\\/Si integration: potential and outlook for integrated low power micro and nanosystems  

Microsoft Academic Search

Integration of III-V compound semiconductors with silicon on a monolithic platform has been a long term vision for the semiconductor industry. In the past, this concept began as a simple notion that the best physical properties of III-V semiconductors and devices could be married with the characteristics of the silicon manufacturing processes. However in recent years, the renewed interest in

Soon Fatt Yoon

2009-01-01

46

Dopant Profiling of III-V Nanostructures for Electronic Applications  

NASA Astrophysics Data System (ADS)

High electron mobility III-V compound semiconductors such as indium arsenide (InAs) are promising candidates for future active channel materials of electron devices to further enhance device performance. In particular, compound semiconductors heterogeneously integrated on Si substrates have been studied, combining the high mobility of III-V semiconductors and the well-established, low cost processing of Si technology. However, one of the primary challenges of III-V device fabrication is controllable, post-growth dopant profiling. Here InAs nanowires and ultrathin layers (nanoribbons) on SiO2/Si are investigated as the channel material for high performance field-effect transistors (FETs) and post-growth, patterned doping techniques are demonstrated. First, the synthesis of crystalline InAs nanowires with high yield and tunable diameters by using Ni nanoparticles as the catalyst material on SiO 2/Si substrates is demonstrated. The back-gated InAs nanowire FETs have electron field-effect mobilities of ˜4,000 cm2/Vs and ION/IOFF ˜104. The uniformity of the InAs nanowires is demonstrated by large-scale assembly of parallel arrays of nanowires (˜400 nanowires) on SiO2/Si substrates by a contact printing process. This enables high performance, "printable" transistors with 5--10 mA ON currents. Second, an epitaxial transfer method for the integration of ultrathin layers of single-crystalline InAs on SiO2/Si substrates is demonstrated. As a parallel to silicon-on-insulator (SOI) technology, the abbreviation "XOI" is used to represent this compound semiconductor-on-insulator platform. A high quality InAs/dielectric interface is obtained by the use of a thermally grown interfacial InAsOx layer (˜1 nm thick). Top-gated FETs exhibit a peak transconductance of ˜1.6 mS/microm at V DS=0.5V with ION/I OFF >104 and subthreshold swings of 107--150 mV/decade for a channel length of ˜0.5 microm. Next, temperature-dependent I-V and C-V studies of single InAs nanowire FETs are utilized to investigate the intrinsic electron transport properties as a function of nanowire radius. From C-V characterization, the densities of thermally-activated fixed charges and trap states on the surface of as-grown (unpassivated) nanowires are investigated to allow the accurate measurement of the gate oxide capacitance. This allows the direct assessment of the electron field-effect mobility. The field-effect mobility is found to monotonically decrease as the radius is reduced to sub-10 nm, with the low temperature transport data highlighting the impact of surface roughness scattering on the mobility degradation for smaller radius nanowires. Next, the electrical properties of the InAs XOI transistors are studied, showing the critical role of quantum confinement in the transport properties of ultrathin XOI layers. Following the investigation of the electrical properties of undoped InAs nanostructures, post-growth, surface doping processes for InAs nanostructures are addressed. Nanoscale, sulfur doping of InAs planar substrates with high dopant areal dose and uniformity by using a self-limiting monolayer doping approach is demonstrated as a means to create ultrashallow junctions. From transmission electron microscopy (TEM) and secondary ion mass spectrometry (SIMS), a dopant profile abruptness of ˜3.5 nm/decade is observed without significant lattice damage. The n+/ p+ junctions fabricated using this doping method exhibit negative differential resistance (NDR) behavior, demonstrating the utility of this approach for device fabrication with high electrically active sulfur concentrations of ˜8x1018 cm-3. Next, a gas phase doping approach for InAs nanowires and ultrathin XOI layers using zinc is demonstrated as an effective means for enabling post-growth dopant profiling of nanostructures. The versatility of the approach is demonstrated by the fabrication of gated diodes and p-MOSFETs. Electrically active zinc concentrations of ˜1x1019 cm-3 are achieved which is necessary for compensating the high electron concentration at the surface o

Ford, Alexandra Caroline

47

BAs-GaAs Semiconductor Alloys as a Photovoltaic Alternative to Nitride Alloys  

SciTech Connect

Nitrogen alloyed III-V semiconductor compounds have been intensely studied in recent years due to unusual effects caused by nitrogen alloying. These effects are exploited in band gap engineering for specific applications such as solar cells and blue lasers.

Hart, G. L. W.; Zunger, A.

2000-01-01

48

Potential applications of III–V nitride semiconductors  

Microsoft Academic Search

Gallium nitride and its alloys with InN and AlN have recently emerged as important semiconductor materials with applications to yellow, green, blue and ultraviolet portions of the spectrum as emitters and detectors and high power temperature electronics. Blue and green nitride LEDs exhibit brightness levels and longevity well in excess of that required for outdoor applications. Combined with the available

Hadis Morkoç

1997-01-01

49

The coupling of thermochemistry and phase diagrams for group III-V semiconductor systems. Final report  

SciTech Connect

The project was directed at linking the thermochemical properties of III-V compound semiconductors systems with the reported phase diagrams. The solid-liquid phase equilibrium problem was formulated and three approaches to calculating the reduced standard state chemical potential were identified and values were calculated. In addition, thermochemical values for critical properties were measured using solid state electrochemical techniques. These values, along with the standard state chemical potentials and other available thermochemical and phase diagram data, were combined with a critical assessment of selected III-V systems. This work was culminated with a comprehensive assessment of all the III-V binary systems. A novel aspect of the experimental part of this project was the demonstration of the use of a liquid encapsulate to measure component activities by a solid state emf technique in liquid III-V systems that exhibit high vapor pressures at the measurement temperature.

Anderson, T.J.

1998-07-21

50

Substrate engineering for monolithic integration of III-V semiconductors with Si CMOS technology  

E-print Network

Ge virtual substrates, fabricated using Si1-xGex-.Ge, compositionally graded buffers, enable the epitaxial growth of device-quality GaAs on Si substrates, but monolithic integration of III-V semiconductors with Si CMOS ...

Dohrman, Carl Lawrence

2008-01-01

51

Platform for monolithic integration of III-V devices with Si CMOS technology  

E-print Network

Monolithic integration of III-V compound semiconductors and Si complementary metal-oxide- semiconductor (CMOS) enables the creation of advanced circuits with new functionalities. In order to merge the two technologies, ...

Pacella, Nan Yang

2012-01-01

52

Nano-scale metal contacts for future III-V CMOS  

E-print Network

As modem transistors continue to scale down in size, conventional Si CMOS is reaching its physical limits and alternative technologies are needed to extend Moore's law. Among different candidates, MOSFETs with a III-V ...

Guo, Alex

2012-01-01

53

Precise measurement of charged defects in III-V compounds (supplement 2)  

NASA Technical Reports Server (NTRS)

Experimental methods and related theory which will permit the measurement of low concentrations of vacancies and other defects in III-V compound semiconductors are discussed. Once the nature of these defects has been determined, this information can be incorporated into a transport theory for devices constructed from these materials, and experiments conducted to test the theory. The vacancies and other defects in the III-V compounds are detected by measurement of the nuclear magnetic resonance (NMR) line width. Most of the III-V compounds have at least one isotope with a nuclear quadrupole moment. In a crystal with a cubic crystal field (characteristic of most III-V compounds) there is no quadrupole splitting of the Zeeman resonance line. However, a defect removes the cubic symmetry locally and causes splitting which result in a change of the NMR width. This change can be used to detect the presence of vacancies.

Soest, J. F.

1973-01-01

54

Development of X-ray lithography and nanofabrication techniques for III-V optical devices  

E-print Network

This dissertation covers the development of fabrication techniques for Bragg-grating-based integrated optical devices in III-V materials. Work on this rich family of devices has largely been limited to numerical analysis ...

Lim, Michael H. (Michael Hong)

2002-01-01

55

On the temperature distributions around dislocations in III-V compounds due to Joule heating  

Microsoft Academic Search

The nonuniform rate of creation of Joule heat due to variations in the electrical conductivity around dislocations in III-V compounds gives rise to variations in the temperature around these dislocations. The general equations and boundary conditions for this temperature distribution are derived for any III-V compound. The specific temperature distributions around 60° and edge dislocations in n-type GaSb are calculated.

H. Booyens; J. S. Vermaak; G. R. Proto

1978-01-01

56

Recent progress in integration of III-V nanowire transistors on Si substrate by selective-area growth  

NASA Astrophysics Data System (ADS)

We report on the recent progress in electronic applications using III-V nanowires (NWs) on Si substrates using the selective-area growth method. This method could align vertical III-V NWs on Si under specific growth conditions. Detailed studies of the III-V NW/Si heterointerface showed the possibility of achieving coherent growth regardless of misfit dislocations in the III-V/Si heterojunction. The vertical III-V NWs grown using selective-area growth were utilized for high performance vertical field-effect transistors (FETs). Furthermore, III-V NW/Si heterointerfaces with fewer misfit dislocations provided us with a unique band discontinuity with a new functionality that can be used for the application of tunnel diodes and tunnel FETs. These demonstrations could open the door to a new approach for creating low power switches using III-V NWs as building-blocks of future nanometre-scaled electronic circuits on Si platforms.

Tomioka, Katsuhiro; Fukui, Takashi

2014-10-01

57

Structural and optical properties of II-VI and III-V compound semiconductors  

NASA Astrophysics Data System (ADS)

This dissertation is on the study of structural and optical properties of some III-V and II-VI compound semiconductors. The first part of this dissertation is a study of the deformation mechanisms associated with nanoindentation and nanoscratching of InP, GaN, and ZnO crystals. The second part is an investigation of some fundamental issues regarding compositional fluctuations and microstructure in GaInNAs and InAlN alloys. In the first part, the microstructure of (001) InP scratched in an atomic force microscope with a small diamond tip has been studied as a function of applied normal force and crystalline direction in order to understand at the nanometer scale the deformation mechanisms in the zinc-blende structure. TEM images show deeper dislocation propagation for scratches along <110> compared to <100>. High strain fields were observed in <100> scratches, indicating hardening due to locking of dislocations gliding on different slip planes. Reverse plastic flow have been observed in <110> scratches in the form of pop-up events that result from recovery of stored elastic strain. In a separate study, nanoindentation-induced plastic deformation has been studied in c-, a-, and m-plane ZnO single crystals and c-plane GaN respectively, to study the deformation mechanism in wurtzite hexagonal structures. TEM results reveal that the prime deformation mechanism is slip on basal planes and in some cases, on pyramidal planes, and strain built up along particular directions. No evidence of phase transformation or cracking was observed in both materials. CL imaging reveals quenching of near band-edge emission by dislocations. In the second part, compositional inhomogeneity in quaternary GaInNAs and ternary InAlN alloys has been studied using TEM. It is shown that exposure to antimony during growth of GaInNAs results in uniform chemical composition in the epilayer, as antimony suppresses the surface mobility of adatoms that otherwise leads to two-dimensional growth and elemental segregation. In a separate study, compositional instability is observed in lattice-matched InAlN films grown on GaN, for growth beyond a certain thickness. Beyond 200 nm of thickness, two sub-layers with different indium content are observed, the top one with lower indium content.

Huang, Jingyi

58

Microstructural evaluation of heteroepitaxial III-V semiconductor thin films  

NASA Astrophysics Data System (ADS)

Microstructural features of single and multilayered strained (In xGa1-xAs/GaAs, (Al)GaAs1-ySb y/GaAs) and unstrained (In0.49Ga0.51P/GaAs) heteroepitaxial structures were evaluated. During growth of a 1.5% mismatched InxGa 1-xAs layer on GaAs at 470°C, real-time multibeam optical stress sensor measurements revealed an unexpected shoulder in the strain-thickness profile. Real-time data was used to pause film growth at pre-determined stress-states surrounding the shoulder region (pre-, mid- and post-shoulder) to probe its origin. Dislocation structure of each stress-state was characterized by transmission electron microscopy. The shoulder coincided with reactions between 60° dislocations forming edge dislocations, suggesting an increased dislocation mobility which is required for multiplication. Dislocation half-loops were observed via cross-sectional microscopy, resulting in rapid relaxation of the film. In-graded (InxGa1-xAs) and Sb-graded (Al0.5Ga0.5As1-ySby, GaAs 1-ySby) compositionally step-graded multilayer buffers were analyzed to determine the optimal alloy for preventing the propagation of threading dislocations to the epitaxial surface. Multilayers were graded from a lattice parameter of 0.564 nm to 0.591 nm (4.6% mismatch) over a 1 mum film thickness. Threading dislocation density in the top-most layer of the Sb-graded structures (?109 cm-2) was lower than the In-graded alloy (>1010 cm-2). In the InxGa1-xAs structure, threading dislocations were observed to congregate in discrete channels directly correlated to surface crosshatches. As/Sb compositional modulations in the Sb-graded structures reveal a more planar growth surface, preventing threading dislocation trapping. Characterization of dislocation structure indicated a directional asymmetry in the 60° and edge dislocation density for the GaAs1-ySb y multilayer. Replacing Ga with Al0.5Ga0.5 in the Sb-graded ternary improved planarity, resulting in a more uniform dislocation density. Residual strain (calculated from quantitative x-ray analysis and dislocation density) in each of the buffer layers was within the bounds predicted by existing relaxation models and dependent upon lattice mismatch strain. Lattice-matched In0.49Ga0.51P-GaAs junctions as active regions of a heterojuction bipolar transistor were evaluated by high-resolution transmission electron microscopy and related to device performance. Microscopy was established as a feasible technique for characterizing interfacial roughness which was related to interface crystal quality (quantified by reverse-biased leakage currents) but not low-voltage device performance.

Chen, Eric Brice

59

Metal/III-V Schottky barrier height tuning for the design of nonalloyed III-V field-effect transistor source/drain contacts  

NASA Astrophysics Data System (ADS)

In this work, we introduce a novel nonalloyed contact structure for n-GaAs and n-In0.53Ga0.47As by using single metals in combination with a thin dielectric to tune the effective metal/III-V work function toward the conduction band edge. We reduced the effective Schottky barrier height (?B,eff) of Al/GaAs from 0.75 to 0.17 eV through the use of a thin atomic layer deposition Al2O3. Barrier height reduction was verified for a variety of metals (Y, Er, Al, Ti, and W) through direct measurements and deduced from increased diode current and reduced contact resistance. Similar results were observed on n-In0.53Ga0.47As. Two possible underlying mechanisms are discussed: one based on the formation of a dielectric dipole and the other based on the blocking of metal induced gap states. This structure has applications as a nonalloyed low resistance ohmic contact for III-V metal-oxide-semiconductor field-effect transistors (MOSFETs) or high electron mobility transistors (HEMTs), and as a near zero barrier height contact for III-V Schottky barrier field-effect transistors or diodes.

Hu, Jenny; Saraswat, Krishna C.; Wong, H.-S. Philip

2010-03-01

60

III-V/Si on silicon-on-insulator platform for hybrid nanoelectronics  

NASA Astrophysics Data System (ADS)

The unique properties of SOI wafers enable the integration of heterogeneous materials with distinct functionalities in different layers. In particular, III-V compound semiconductors are very attractive for low-noise and high-speed electronic and photonic components integrated on a single chip. We have developed a CMOS compatible and fully integrated solution for the integration of III-V compound semiconductors with silicon technology for optoelectronic applications. InAs compound semiconductor nanostructures are synthesized in SOI wafers using the combined ion beam implantation and millisecond liquid-phase epitaxial growth. Optoelectronic and microstructural investigations carried out on implanted, annealed, and selectively etched samples confirm the formation of high-quality III-V compound semiconductor nanostructures.

Prucnal, Slawomir; Zhou, Shengqiang; Ou, Xin; Facsko, Stefan; Oskar Liedke, Maciej; Bregolin, Felipe; Liedke, Bartosz; Grebing, Jochen; Fritzsche, Monika; Hübner, Rene; Mücklich, Arndt; Rebohle, Lars; Helm, Manfred; Turek, Marcin; Drozdziel, Andrzej; Skorupa, Wolfgang

2014-02-01

61

Nontrivial Z2 topology in bismuth-based III-V compounds  

NASA Astrophysics Data System (ADS)

Realizing topological insulators in commonly used III-V semiconductors is of great importance for their potential application in spintronics and quantum computing. Here we propose a general strategy to realize topological insulators in conventional III-V semiconductors by bismuth substitution and external strain. Based on first-principles calculations, we identify that AlBi (GaBi and InBi) become topological insulators (semimetals) under proper external strain by directly calculating Z2 invariants and surface states. Furthermore, we demonstrate that a topological phase transition can be induced by Bi substitution in common III-V semiconductors like GaAs. These proposed topological insulators can be easily integrated into various semiconductor electronic devices and modulated by well-developed modern semiconductor technologies.

Huang, Huaqing; Liu, Jianpeng; Duan, Wenhui

2014-11-01

62

Silicon MCM substrates for integration of III-V photonic devices and CMOS IC`s  

SciTech Connect

The progress made in advanced packaging development at Sandia National Laboratories for integration of III-V photonic devices and CMOS IC`s on Silicon MCM substrates for planar aid stacked applications will be reported. Studies to characterize precision alignment techniques using solder attach materials compatible with both silicon IC`s and III-V devices will be discussed. Examples of the use of back-side alignment and IR through-wafer inspection will be shown along with the extra processing steps that are used. Under bump metallurgy considerations are also addressed.

Seigal, P.; Carson, R.; Flores, R.; Rose, B.

1993-07-01

63

III-V/silicon germanium tandem solar cells on silicon substrates  

NASA Astrophysics Data System (ADS)

The development of a cost-effective high voltage tandem solar cell that can be grown directly on a silicon (Si) platform can lead to a 34% increase in efficiency over the present best monocrystalline Si laboratory device. III-V devices are known to yield some of the highest efficiencies in photovoltaics, but the high cost of lattice matched substrates and metal organic chemical vapor deposition (MOCVD) and device development make them prohibitively expensive in many markets. By utilizing silicon substrates and limiting the thickness of the III-V MOCVD material growth, this cost can be reduced. The leveraging technology of this initiative is a metamorphic silicon:germanium (SiGe) buffer between the silicon substrate and the active device layers. As developed by AmberWave Inc., it provides a low-dislocation interface for III-V nucleation and a high quality bottom cell grown by reduced pressure chemical vapor deposition (RPCVD). This research first reports on the theoretical limits of a III-V/SiGe tandem solar cell. Results will evaluate multiple III-V materials for the determination of optimal material composition to be lattice-matched with SiGe. Following this, a more complex device simulation, incorporating all major loss mechanisms, is accomplished in order to predict ideal efficiency targets and evaluate present experimental structures. Results demonstrate a robust model capable of simulating a wide range of binary and ternary III-V devices. Predictions show the capability of a tandem device operating at 32.5% 1-sun efficiency without requiring TDD improvement beyond that of the present SiGe layers. Following simulations, experimental III-V structures are grown via MOCVD and characterized, indicating successful process development for growth of III-V materials on the SiGe platform. This growth is then validated via the design and development of experimental solar device structures. Each iteration, beginning with the single-junction windowless GaAsP solar cell and concluding with a GaAsP/SiGe tandem device, is analyzed and reported. GaAsP bandgap-voltage offsets achieve a record best result of 0.54 Volts in single-junction devices while dual-junction devices demonstrate a result toward AM1.5 19.4% efficiency with AR-correction and light trapping.

Schmieder, Kenneth J.

64

Electronic structure of III-V zinc-blende semiconductors from first principles  

NASA Astrophysics Data System (ADS)

For analyzing quantum transport in semiconductor devices, accurate electronic structures are critical for quantitative predictions. Here we report theoretical analysis of electronic structures of all III-V zinc-blende semiconductor compounds. Our calculations are from density functional theory with the semilocal exchange proposed recently [Tran and Blaha, Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.102.226401 102, 226401 (2009)], within the linear muffin tin orbital scheme. The calculated band gaps and effective masses are compared to experimental data and good quantitative agreement is obtained. Using the theoretical scheme presented here, quantum transport in nanostructures of III-V compounds can be confidently predicted.

Wang, Yin; Yin, Haitao; Cao, Ronggen; Zahid, Ferdows; Zhu, Yu; Liu, Lei; Wang, Jian; Guo, Hong

2013-06-01

65

Etched-wall bent-guide structure for integrated optics in the III-V semiconductors  

Microsoft Academic Search

Bent-guide structures will undoubtedly play an important role in increasing packing density in future integrated optical circuits. A method for forming bends in waveguides in III-V semiconductors by reflection off an etched vertical wall is proposed for providing wave-guiding through 90° with negligible loss.

TREVOR M. BENSON

1984-01-01

66

Selective area growth of III-V semiconductors by chemical beam epitaxy: study of reaction mechanisms  

Microsoft Academic Search

The localized growth of III-V epitaxial structures on substrates patterned with dielectric masks provides a flexible technique for the monolithic integration of electronic and optoelectronic devices. Chemical beam epitaxy (CBE) is an attractive growth technique for use in this approach and interest has consequently focussed on the reaction mechanisms which give rise to selective area growth in CBE. In the

Graham J. Davies; P. J. Skevington; J. S. Foord; C. L. French; C. L. Levoguer

1994-01-01

67

Low-index nanopatterned barrier for hybrid oxide-free III-V silicon conductive bonding.  

PubMed

Oxide-free bonding of a III-V active stack emitting at 1300-1600 nm to a silicon-on-insulator wafer offers the capability to electrically inject lasers from the silicon side. However, a typical 500-nm-thick silicon layer notably attracts the fundamental guided mode of the silicon + III-V stack, a detrimental feature compared to established III-V Separate-Confinement Heterostructure (SCH) stacks. We experimentally probe with photoluminescence as an internal light source the guiding behavior for oxide-free bonding to a nanopatterned silicon wafer that acts as a low-index barrier. We use a sub-wavelength square array of small holes as an effective "low-index silicon" medium. It is weakly modulated along one dimension (superperiodic array) to outcouple the resulting guided modes to free space, where we use an angle-resolved spectroscopy study. Analysis of experimental branches confirms the capability to operate with a fundamental mode well localized in the III-V heterostructures. PMID:25321802

Bougot-Robin, Kristelle; Talneau, Anne; Benisty, Henri

2014-09-22

68

Ballistic recovery in III-V nanowire transistors M. J. Gilberta  

E-print Network

Ballistic recovery in III-V nanowire transistors M. J. Gilberta and S. K. Banerjee Microelectronics of polar optical phonon processes allow devices to recover their ballistic behavior even in the presence different simulations of ballistic operation of these devices.2,3 However, recent work has shown

Gilbert, Matthew

69

Heterogeneous integration of III–V on Silicon based microlaser sources for photonic integrated circuit applications  

Microsoft Academic Search

Large scale integration of optical functions on Silicon has become of a great interest in the last years. Through heterogeneous integration of III-V materials on Silicon, new building blocks are currently studied. An important issue is the development of efficient laser sources, for both guided and free space emission. Low threshold combined to small footprints are required for silicon photonics

Pedro Rojo Romeo; Lydie Ferrier; Fabien Mandorlo; Xavier Letartre; Pierre Viktorovitch; Jean-Marc Fedeli

2009-01-01

70

High temperature thermoelectric characterization of III-V semiconductor thin films by oxide bonding  

E-print Network

Page 1 High temperature thermoelectric characterization of III-V semiconductor thin films by oxide bonding technique is developed for high temperature thermoelectric characterization of the thin film III-W-N diffusion barrier. A thermoelectric material, thin film ErAs:InGaAlAs metal/semiconductor nanocomposite

Bowers, John

71

Narrow band gap III–V based-FET for ultra low power high frequency analog applications  

Microsoft Academic Search

For more than 30 years, III-V materials and associated transistors or integrated circuits aroused of numerous studies to achieve today an industrial reality with the availability of a panel of high performance technologies. For the development of these III-V technologies, there was no established roadmap; the line of sight was essentially the increase of the operating frequency limit (more than

Gilles Dambrine; S. Bollaert; Y. Roellens; A. Noudeviwa; F. Danneville; A. Olivier; N. Wichmann; L. Desplanque; X. Wallart; J. Grahn; G. Moschetti; P.-A. Nilsson; M. Malmkvist; E. Lefebvre

2009-01-01

72

Hybrid III-V/silicon single-mode laser with periodic microstructures.  

PubMed

In this Letter, a III-V/silicon hybrid single-mode laser operating at C band for photonic integration circuit is presented. The InGaAlAs gain structure is bonded onto a patterned silicon-on insulator through wafer to wafer directly. The mode selected mechanism based on a hybrid III-V/silicon straight cavity with periodic microstructures is applied, which only need low cost i-line projection photolithography in the whole technological process. At room temperature, we obtain 0.62 mW output power in continuous-wave. The side mode suppression ratio of larger than 20 dB is obtained from experiments. [corrected]. PMID:23503234

Zhang, Yejin; Qu, Hongwei; Wang, Hailing; Zhang, Siriguleng; Ma, Shaodong; Qi, Aiyi; Feng, Zhigang; Peng, Hongling; Zheng, Wanhua

2013-03-15

73

MBE growth technology for high quality strained III-V layers  

NASA Technical Reports Server (NTRS)

III-V films are grown on large automatically perfect terraces of III-V substrates which have a different lattice constant, with temperature and Group II and V arrival rates chosen to give a Group III element stable surface. The growth is pulsed to inhibit Group III metal accumulation to low temperature, and to permit the film to relax to equilibrium. The method of the invention 1) minimizes starting step density on sample surface; 2) deposits InAs and GaAs using an interrupted growth mode (0.25 to 2 mono-layers at a time); 3) maintains the instantaneous surface stoichiometry during growth (As-stable for GaAs, In-stable for InAs); and 4) uses time-resolved RHEED to achieve aspects (1)-14 (3).

Grunthaner, Frank J. (Inventor); Liu, John K. (Inventor); Hancock, Bruce R. (Inventor)

1992-01-01

74

MBE growth technology for high quality strained III-V layers  

NASA Technical Reports Server (NTRS)

The III-V films are grown on large automatically perfect terraces of III-V substrates which have a different lattice constant, with temperature and Group III and V arrival rates chosen to give a Group III element stable surface. The growth is pulsed to inhibit Group III metal accumulation of low temperature, and to permit the film to relax to equilibrium. The method of the invention: (1) minimizes starting step density on sample surface; (2) deposits InAs and GaAs using an interrupted growth mode (0.25 to 2 monolayers at a time); (3) maintains the instantaneous surface stoichiometry during growth (As-stable for GaAs, In-stable for InAs); and (4) uses time-resolved RHEED to achieve aspects (1) through (3).

Grunthaner, Frank J. (inventor); Liu, John K. (inventor); Hancock, Bruce R. (inventor)

1990-01-01

75

Electrochemical pore formation mechanism in III-V crystals (Part II)  

SciTech Connect

Chemical and electrical processes developing at the semiconductor-electrolyte interface under conditions of anodic polarization were analyzed. It was shown that dense chemisorption coatings are formed on the surface of III-V crystals at voltages of pore formation onset, and a degenerate inversion layer is formed on the semiconductor side. In this case, a drop of the largest part of the applied voltage in the adsorption layer creates the prerequisites for nucleophilic substitution reactions involving chemisorbed anions and coordination-saturated atoms under the crystal surface. The mechanisms of these reactions were considered as applied to sphalerite-structured crystals. The results of experimental studies of the structures and compositions of porous layers in III-V crystals formed in various electrolytes at various polarization voltages are explained on the basis of the obtained concepts.

Ulin, V. P.; Konnikov, S. G. [Russian Academy of Sciences, Ioffe Physicotechnical Institute (Russian Federation)], E-mail: konnikov@mail.ioffe.ru

2007-07-15

76

AM0 concentration operation of III-V compounds solar cells  

Microsoft Academic Search

III-V compounds solar cells were examined by concentrated illumination of AM0 sunlight. High concentration or nonuniform illumination was found to bring significance degradation of FF due to apparent degradation of a diode ideality factor or “rounded” I-V curve. The output current at the maximum power point dropped as a result. This paper covers an experimental evaluation, analysis and solutions to

K. Araki; M. Yamaguchi; M. Imaizumi; S. Matsuda; T. Takamoto; H. Kurita

2000-01-01

77

New and unified model for Schottky barrier and III--V insulator interface states formation  

Microsoft Academic Search

For n- and p-doped III--V compounds, Fermi-level pinning and accompanying phenomena of the (110) cleavage surface have been studied using photoemission at h..nu..< or approx. =300 eV (so that core as well as valence band levels could be studied). Both the clean surfaces and the changes produced, as metals or oxygen are added to those surfaces in submonolayer quantities, have

W. E. Spicer; P. W. Chye; P. R. Skeath; C. Y. Su; I. Lindau

1979-01-01

78

Methodology for Development of High-? Stacked Gate Dielectrics on III–V Semiconductors  

Microsoft Academic Search

A comprehensive methodology for the development of gate dielectrics on III–V semiconductors is presented. This methodology\\u000a has been motivated by the tremendous difficulties encountered during the development of gate dielectrics on GaAs. The understanding\\u000a that modern gate dielectrics are typically layered structures with the immediate dielectric\\/semiconductor interface having\\u000a substantially different (and often mutually exclusive) requirements compared to the bulk of

Matthias Passlack

79

Power-efficient III-V/silicon external cavity DBR lasers.  

PubMed

We report the design and characterization of external-cavity DBR lasers built with a III-V-semiconductor reflective-SOA with spot-size converter edge-coupled to SOI waveguides containing Bragg grating mirrors. The un-cooled lasers have wall-plug-efficiencies of up to 9.5% at powers of 6 mW. The lasers are suitable for making power efficient, hybrid WDM transmitters in a CMOS-compatible SOI optical platform. PMID:23188309

Zilkie, A J; Seddighian, P; Bijlani, B J; Qian, W; Lee, D C; Fathololoumi, S; Fong, J; Shafiiha, R; Feng, D; Luff, B J; Zheng, X; Cunningham, J E; Krishnamoorthy, A V; Asghari, M

2012-10-01

80

Improved Precursor Chemistry for the Synthesis of III-V Quantum Dots  

PubMed Central

The synthesis of III-V Quantum Dots has been long known to be more challenging than the synthesis of other types of inorganic quantum dots. This is attributed to highly reactive group-V precursors. We synthesized molecules that are suitable for use as group-V precursors and characterized their reactivity using multiple complementary techniques. We show that the size distribution of indium arsenide quantum dots indeed improves with decreased precursor reactivity. PMID:23228014

Harris, Daniel K.; Bawendi, Moungi G.

2012-01-01

81

Quantum corrections to the Hall effect in III-V semiconductors  

Microsoft Academic Search

The authors have measured the temperature dependence of the low-temperature Hall effect coefficient, RH, and resistance, R, of various III-V semiconductors. In 3D when the magnetic field suppresses the quantum interference correction, RH and R vary with temperature T as T1\\/2 in the manner predicted for the electron interaction correction. However, the ratio ( delta RH\\/RH)\\/( delta R\\/R) did not

D J Newson; M Pepper; E Y Hall; G Hill

1987-01-01

82

Vertical microcavities based on photonic crystal mirrors for III-V\\/Si integrated microlasers  

Microsoft Academic Search

The on-coming photonic layer of CMOS integrated circuits needs efficient light sources to treat and transmit the flow of data. We develop new configurations of III-V\\/Si vertical cavity lasers coupled to silicon optical waveguides using mirror\\/coupler based on photonic crystals. These devices can be fabricated using fully CMOS-compatible technological steps. Using this approach, the optical gain is provided by the

Lydie Ferrier; Salim Boutami; Fabien Mandorlo; Xavier Letartre; Pedro Rojo Romeo; Pierre Viktorovitch; Philippe Gilet; Badhise Ben Bakir; Philippe Grosse; Jean-Marc Fedeli; Alexei Chelnokov

2008-01-01

83

First principles calculation of material properties of group IV elements and III-V compounds  

E-print Network

of narrow-band-gap semiconductors: InP, InAs, and InSb.f (Ry) bands in ? Si Ge AlP AlAs AlSb InP InAs InSb GaP GaAsband structures for the group IV and group III-V materials Si, Ge, AlP, AlAs, AlSb, InP, InAs, InSb, GaP,

Malone, Brad Dean

2012-01-01

84

III-V quantum light source and cavity-QED on Silicon  

PubMed Central

Non-classical light sources offer a myriad of possibilities in both fundamental science and commercial applications. Single photons are the most robust carriers of quantum information and can be exploited for linear optics quantum information processing. Scale-up requires miniaturisation of the waveguide circuit and multiple single photon sources. Silicon photonics, driven by the incentive of optical interconnects is a highly promising platform for the passive optical components, but integrated light sources are limited by silicon's indirect band-gap. III–V semiconductor quantum-dots, on the other hand, are proven quantum emitters. Here we demonstrate single-photon emission from quantum-dots coupled to photonic crystal nanocavities fabricated from III–V material grown directly on silicon substrates. The high quality of the III–V material and photonic structures is emphasized by observation of the strong-coupling regime. This work opens-up the advantages of silicon photonics to the integration and scale-up of solid-state quantum optical systems. PMID:23393621

Luxmoore, I. J.; Toro, R.; Pozo-Zamudio, O. Del; Wasley, N. A.; Chekhovich, E. A.; Sanchez, A. M.; Beanland, R.; Fox, A. M.; Skolnick, M. S.; Liu, H. Y.; Tartakovskii, A. I.

2013-01-01

85

First principles investigation of water adsorption and charge transfer on III-V(110) semiconductor surfaces  

NASA Astrophysics Data System (ADS)

We report a DFT/GGA study of water adsorption and charge transfer at the relaxed (110) surfaces of several III-V binary semiconductors: GaAs, GaSb, and InAs. Our calculations are the first to show that adsorption of dissociated water changes the (110) surface structure. The characteristic III-V bond rotation through an angle of 30° is reversed. The buckled III-V bond at the semiconductor/water interface rotates into the surface through a new angle, which we calculate to be approximately 11° on all three binaries. Only dissociation of water - as opposed to chemisorption or physisorption - leads to this pseudo-unrelaxed configuration. We calculate geometries and reaction energies for several different adsorption mechanisms and find that molecular adsorption is the most favorable. We are able to reproduce binding configurations and energies for known adsorption sites on GaAs(110), but we also show new calculations for water on GaSb(110) and InAs(110). Lastly, we calculate the shift in electronic work function and induced surface dipole moment due to adsorbed water. We show that shifts in work function maximize at 1 ML of water, consistent with previous experimental works. Analysis of the partial charges and electron density reveals that adsorption of water polarizes the (110) surface, leading to local charge transfer across the semiconductor/water interface.

Williams, Kristen S.; Lenhart, Joseph L.; Andzelm, Jan W.; Bandara, Sumith V.; Baril, Neil F.; Henry, Nathan C.; Tidrow, Meimei Z.

2014-04-01

86

High mobility CMOS technologies using III-V/Ge channels on Si platform  

NASA Astrophysics Data System (ADS)

MOSFETs using channel materials with high mobility and low effective mass have been regarded as strongly important for obtaining high current drive and low supply voltage CMOS under sub 10 nm regime. From this viewpoint, attentions have recently been paid to Ge and III-V channels. In this paper, possible solutions for realizing III-V/Ge MOSFETs on the Si platform are presented. The high quality III-V channel formation on Si substrates can be realized through direct wafer bonding. The gate stack formation is constructed on a basis of atomic layer deposition (ALD) Al2O3 gate insulators for both InGaAs and Ge MOSFETs. As the source/drain (S/D) formation, Ni-based metal S/D is implemented for both InGaAs and Ge MOSFETs. By combining these technologies, we demonstrate successful integration of InGaAs-OI nMOSFETs and Ge p-MOSFETs on a same wafer and their superior device performance.

Takagi, S.; Kim, S.-H.; Yokoyama, M.; Zhang, R.; Taoka, N.; Urabe, Y.; Yasuda, T.; Yamada, H.; Ichikawa, O.; Fukuhara, N.; Hata, M.; Takenaka, M.

2013-10-01

87

Broadband and omnidirectional anti-reflection layer for III/V multi-junction solar cells  

E-print Network

We report a novel graded refractive index antireflection coating for III/V quadruple solar cells based on bottom-up grown tapered GaP nanowires. We have calculated the photocurrent density of an InGaP-GaAs-InGaAsP-InGaAs solar cell with a MgF2/ZnS double layer antireflection coating and with a graded refractive index coating. The photocurrent density can be increased by 5.9 % when the solar cell is coated with a graded refractive index layer with a thickness of 1\\mu m. We propose to realize such a graded refractive index layer by growing tapered GaP nanowires on III/V solar cells. For a first demonstration of the feasibility of the growth of tapered nanowires on III/V solar cells, we have grown tapered GaP nanowires on AlInP/GaAs substrates. We show experimentally that the reflection from the nanowire coated substrate is reduced and that the transmission into the substrate is increased for a broad spectral and angular range.

Diedenhofen, Silke L; Haverkamp, Erik; Bauhuis, Gerard; Schermer, John; Rivas, Jaime Gómez; 10.1016/j.solmat.2012.02.022

2012-01-01

88

Oxidized In-containing III-V(100) surfaces: Formation of crystalline oxide films and semiconductor-oxide interfaces  

NASA Astrophysics Data System (ADS)

Previously found oxidized III-V semiconductor surfaces have been generally structurally disordered and useless for applications. We disclose a family of well-ordered oxidized InAs, InGaAs, InP, and InSb surfaces found by experiments. The found epitaxial oxide-III-V interface is insulating and free of defects related to the harmful Fermi-level pinning, which opens up new possibilities to develop long-sought III-V metal-oxide-semiconductor transistors. Calculations reveal that the early stages in the oxidation process include only O-III bonds due to the geometry of the III-V(100)c(8×2) substrate, which is responsible for the formation of the ordered interface. The found surfaces provide a different platform to study the oxidation and properties of oxides, e.g., the origins of the photoemission shifts and electronic structures, using surface science methods.

Punkkinen, M. P. J.; Laukkanen, P.; Lång, J.; Kuzmin, M.; Tuominen, M.; Tuominen, V.; Dahl, J.; Pessa, M.; Guina, M.; Kokko, K.; Sadowski, J.; Johansson, B.; Väyrynen, I. J.; Vitos, L.

2011-05-01

89

Integration of III-V optical devices and interconnects on Si using SiGe virtual substrates  

E-print Network

Because of the limitations to the functionality that Si can provide, integration of light emitting materials such as GaAs and other III-V materials provides the promise for the combination of electrical and optical devices ...

Yang, Vicky Kung-Fan, 1975-

2002-01-01

90

30 CFR 57.22218 - Seals and stoppings (III, V-A, and V-B mines).  

...NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-UNDERGROUND METAL AND NONMETAL MINES Safety Standards for Methane in Metal and Nonmetal Mines Ventilation § 57.22218 Seals and stoppings (III, V-A, and V-B mines)....

2014-07-01

91

Formation of III-V-on-insulator structures on Si by direct wafer bonding  

NASA Astrophysics Data System (ADS)

We have studied the formation of III-V-compound-semiconductors-on-insulator (III-V-OI) structures with thin buried oxide (BOX) layers on Si wafers by using developed direct wafer bonding (DWB). In order to realize III-V-OI MOSFETs with ultrathin body and extremely thin body (ETB) InGaAs-OI channel layers and ultrathin BOX layers, we have developed an electron-cyclotron resonance (ECR) O2 plasma-assisted DWB process with ECR sputtered SiO2 BOX layers and a DWB process based on atomic-layer-deposition Al2O3 (ALD-Al2O3) BOX layers. It is essential to suppress micro-void generation during wafer bonding process to achieve excellent wafer bonding. We have found that major causes of micro-void generation in DWB processes with ECR-SiO2 and ALD-Al2O3 BOX layers are desorption of Ar and H2O gas, respectively. In order to suppress micro-void generation in the ECR-SiO2 BOX layers, it is effective to introduce the outgas process before bonding wafers. On the other hand, it is a possible solution for suppressing micro-void generation in the ALD-Al2O3 BOX layers to increase the deposition temperature of the ALD-Al2O3 BOX layers. It is also another possible solution to deposit ALD-Al2O3 BOX layers on thermally oxidized SiO2 layers, which can absorb the desorption gas from ALD-Al2O3 BOX layers.

Yokoyama, Masafumi; Iida, Ryo; Ikku, Yuki; Kim, Sanghyeon; Takagi, Hideki; Yasuda, Tetsuji; Yamada, Hisashi; Ichikawa, Osamu; Fukuhara, Noboru; Hata, Masahiko; Takenaka, Mitsuru; Takagi, Shinichi

2013-09-01

92

Microscopic study of the hydrogen diffusion in III-V semiconductors  

SciTech Connect

The authors report on experiments which observe on a microscopic scale the migration of isolated hydrogen in InP, GaAs, and InAs. Using the radioactive acceptor {sup 117}Cd, Cd-H pairs have been formed in these III-V semiconductors. After the decay of {sup 117}Cd to {sup 117}In, H is no longer bound to an acceptor and can diffuse freely. This diffusion has been observed by perturbed {gamma}{gamma} angular correlation (PAC) spectroscopy. At 10 K, the occupation of two different lattice sites by hydrogen has been observed. First results on the diffusion of hydrogen will be discussed.

Burchard, A.; Deicher, M.; Knopf, M.; Stoetzler, A. [Univ. Konstanz (Germany). Fakultaet fuer Physik; Forkel-Wirth, D. [CERN/PPE, Geneva (Switzerland); Magerle, R. [Univ. Bayreuth (Germany). Physikalische Chemie; Fedoseyev, V.N.; Mishin, V.I. [Inst. of Spectroscopy, Troitzk (Russian Federation)

1998-12-31

93

Heralded single-photon source in a III-V photonic crystal.  

PubMed

In this Letter we demonstrate heralded single-photon generation in a III-V semiconductor photonic crystal platform through spontaneous four-wave mixing. We achieve a high brightness of 3.4×10(7) pairs·s(-1) nm(-1) W(-1) facilitated through dispersion engineering and the suppression of two-photon absorption in the gallium indium phosphide material. Photon pairs are generated with a coincidence-to-accidental ratio over 60 and a low g(2) (0) of 0.06 proving nonclassical operation in the single photon regime. PMID:23455253

Clark, Alex S; Husko, Chad; Collins, Matthew J; Lehoucq, Gaelle; Xavier, Stéphane; De Rossi, Alfredo; Combrié, Sylvain; Xiong, Chunle; Eggleton, Benjamin J

2013-03-01

94

Solid-state lighting : the III-V Epi Killer App.  

SciTech Connect

Throughout its history, lighting technology has made tremendous progress: the efficiency with which power is converted into usable light has increased 2.8 orders of magnitude over three centuries. This progress has, in turn, fueled large increases in the consumption of light and productivity of human society. In this talk, we review an emerging new technology, solid-state lighting: its frontier performance potential; the underlying advances in physics and materials that might enable this performance potential; the resulting energy consumption and human productivity benefits; and the impact on worldwide III-V epi manufacture.

Tsao, Jeffrey Yeenien

2010-06-01

95

Effect of defects on III-V MWIR nBn detector performance  

NASA Astrophysics Data System (ADS)

Under elevated defect concentrations, MWIR, III-V nBn detectors exhibit diffusion limited performance with elevated dark current densities. The resulting diffusion current is limited by the generation of carriers through defect states in the neutral n-type absorber and a dark current dependence on the defect density described by one of two limits, a short absorber or long absorber limit. This characteristic contrasts that exhibited by defect limited, conventional pn junction based photodiodes which exhibit performance limited by Shockley-Read-Hall generation in the depletion layer rather than diffusion based processes.

Savich, G. R.; Sidor, D. E.; Du, X.; Morath, C. P.; Cowan, V. M.; Wicks, G. W.

2014-09-01

96

Vertical bridgman and gradient freeze growth of III-V compound semiconductors  

SciTech Connect

Major improvements in the structural and electrical perfection of single crystals of III-V compound semiconductors have been achieved by using new vertical Bridgman-type and vertical gradient freeze techniques. A general review of experimental set-ups used for growth of large diameter crystals of GaP, InP and GaAs is presented. Crystal properties and characteristic features are discussed to illustrate advantages and disadvantages of the vertical Bridgman-type growth techniques. 22 refs., 5 figs.

Bourret, E.D.

1990-07-01

97

Progress in the Development of Metamorphic Multi-Junction III-V Space-Solar Cells at Essential Research Incorporated  

NASA Technical Reports Server (NTRS)

Theoretical calculations have shown that highest efficiency III-V multi-junction solar cells require alloy structures that cannot be grown on a lattice-matched substrate. Ever since the first demonstration of high efficiency metamorphic single junction 1.1 eV and 1.2 eV InGaAs solar cells by Essential Research Incorporated (ERI), interest has grown in the development of multi-junction cells of this type using graded buffer layer technology. ERI is currently developing a dual-junction 1.6 eV InGaP/1.1 eV InGaAs tandem cell (projected practical air-mass zero (AM0), one-sun efficiency of 28%, and 100-sun efficiency of 37.5%) under a Ballistic Missile Defense Command (BMDO) SBIR Phase II program. A second ongoing research effort at ERI involves the development of a 2.1 eV AlGaInP/1.6 eV InGaAsP/1.2 eV InGaAs triple-junction concentrator tandem cell (projected practical AM0 efficiency of 36.5% under 100 suns) under a SBIR Phase II program funded by the Air Force. We are in the process of optimizing the dual-junction cell performance. In case of the triple-junction cell, we have developed the bottom and the middle cell, and are in the process of developing the layer structures needed for the top cell. A progress report is presented in this paper.

Sinharoy, Samar; Patton, Martin O.; Valko, Thomas M., Sr.; Weizer, Victor G.

2002-01-01

98

Recipes for crystal phase design in Au-catalyzed III-V nanowires  

NASA Astrophysics Data System (ADS)

We develop a kinetic model for the crystal structure of Au-catalyzed III-V nanowires which is capable of describing the wurtzite content as a function of the growth temperature, group V flux, and the nanowire elongation rate. The self-consistency condition with the correct pre-exponent in the Zeldovich nucleation rate allows us to estimate the actual group III concentration in the droplet which corresponds to a given elongation rate. Our model predicts a non-monotonic dependence of the wurtzite percentage on the group III concentration. We analyze relevant experimental data on the preferred crystal structure of Au-catalyzed GaAs nanowires obtained by three different epitaxy techniques and explain why the MBE-grown GaAs nanowires at near 550°C are predominantly wurtzite, while the MOCVD and HVPE-grown GaAs nanowires obtained with very high As fluxes and at very different temperatures (464°C and 715°C) are zincblende. Overall, the model provides some simple recipes for structural design of III-V nanowires by tuning the technologically controlled growth conditions such as temperature and fluxes.

Dubrovskii, Vladimir G.; Grecenkov, Jurij

2014-10-01

99

Electronic structure of generic semiconductors: Antifluorite silicide and III-V compounds  

SciTech Connect

The perturbation potential which transmutes a homopolar column-IV diamondlike semiconductor into either a heteropolar zinc-blende-like III-V or II-VI compound or an antifluorite semiconductor can be thought of as consisting of a sum of two terms: (i) a long-range Coulomb dipole potential ..delta..V-italic/sub dip/(r) associated with the different valence of the atoms of the compound relative to the atoms in the diamondlike system, and (ii) the remaining, short-range and primarily repulsive core pseudopotential ..delta..V-italic/sub CC/(r) (a ''central-cell'' correction). Whereas ..delta..V-italic/sub dip/(r) is common to all members of a given structural class (e.g., all III-V or all II-VI compounds or all antifluorite silicides), defining thereby generic semiconductors, the central-cell potential ..delta..V-italic/sub CC/(r) carries the specific signature of each atom, distinguishing therefore members of a given class from each other.

Wood, D.M.; Zunger, A.

1986-09-15

100

III-V nanocrystals capped with molecular metal chalcogenide ligands: high electron mobility and ambipolar photoresponse.  

PubMed

In this work, we synthesized InP and InAs nanocrystals (NCs) capped with different inorganic ligands, including various molecular metal chalcogenide complexes (MCCs) and chalcogenide ions. We found that MCCs and chalcogenide ions can quantitatively displace organic ligands from the surface of III-V NCs and serve as the inorganic capping groups for III-V NC surfaces. These inorganic ligands stabilize colloidal solutions of InP and InAs NCs in polar solvents and greatly facilitate charge transport between individual NCs. Charge transport studies revealed high electron mobility in the films of MCC-capped InP and InAs NCs. For example, we found that bridging InAs NCs with Cu(7)S(4)(-) MCC ligands can lead to very high electron mobility exceeding 15 cm(2)/(V s). In addition, we observed unprecedented ambipolar (positive/negative) photoresponse of MCC-capped InAs NC solids that changed sign depending on the ligand chemistry, illumination wavelength, and doping of the NC solid. For example, the sign of photoconductance of InAs NCs capped with Cu(7)S(4)(-) or Sn(2)S(6)(4-) ions converted from positive at 0.80 and 0.95 eV to negative at 1.27 and 1.91 eV. We propose an explanation of this unusually complex photoconductivity of InAs NC solids. PMID:23267673

Liu, Wenyong; Lee, Jong-Soo; Talapin, Dmitri V

2013-01-30

101

III-V/Si hybrid photonic devices by direct fusion bonding  

PubMed Central

Monolithic integration of III-V compound semiconductors on silicon is highly sought after for high-speed, low-power-consumption silicon photonics and low-cost, light-weight photovoltaics. Here we present a GaAs/Si direct fusion bonding technique to provide highly conductive and transparent heterojunctions by heterointerfacial band engineering in relation to doping concentrations. Metal- and oxide-free GaAs/Si ohmic heterojunctions have been formed at 300°C; sufficiently low to inhibit active material degradation. We have demonstrated 1.3 ?m InAs/GaAs quantum dot lasers on Si substrates with the lowest threshold current density of any laser on Si to date, and AlGaAs/Si dual-junction solar cells, by p-GaAs/p-Si and p-GaAs/n-Si bonding, respectively. Our direct semiconductor bonding technique opens up a new pathway for realizing ultrahigh efficiency multijunction solar cells with ideal bandgap combinations that are free from lattice-match restrictions required in conventional heteroepitaxy, as well as enabling the creation of novel high performance and practical optoelectronic devices by III-V/Si hybrid integration. PMID:22470842

Tanabe, Katsuaki; Watanabe, Katsuyuki; Arakawa, Yasuhiko

2012-01-01

102

Characteristics and device applications of erbium doped III-V semiconductors grown by molecular beam epitaxy  

NASA Astrophysics Data System (ADS)

We have studied the properties of molecular beam epitaxially (MBE)-grown Erdoped III-V semiconductors for optoelectronic applications. Optically excited Er3+ in insulating materials exhibits optical emission chiefly around 1.54 ?m, in the range of minimum loss in silica fiber. It was thought, therefore, that an electrically pumped Er-doped semiconductor laser would find great applicability in fiber-optic communication systems. Exhaustive photoluminescence (PL) characterization was conducted on several of As-based III-V semiconductors doped with Er, on bulk as well as quantum-well structures. We did not observe any Errelated PL emission at 1.54 ?m for any of the materials/structures studied, a phenomenon which renders impractical the realization of an Er-doped III-V semiconductor laser. Deep level transient spectroscopy studies were performed on GaAs and AlGaAs co-doped with Er and Si to investigate the presence of any Er-related deep levels. The lack of band-edge luminescence in the GaAs:Er films led us to perform carrier-lifetime measurements by electro-optic sampling of photoconductive transients generated in these films. We discovered lifetimes in the picosecond regime, tunable by varying the Er concentration in the films. We also found the films to be highly resistive, the resistivity increasing with increasing Er-concentration. Intensive structural characterization (double-crys-tal x-ray and transmission electron microscopy) performed by us on GaAs:Er epilayers indicates the presence of high-density nanometer-sized ErAs precipitates in MBE-grown GaAs:Er. These metallic nanoprecipitates probably form internal Schottky barriers within the GaAs matrix, which give rise to Shockley-Read-Hall recombination centers, thus accounting for both the high resistivities and the ultrashort carrier lifetimes. Optoelectronic devices fabricated included novel tunable (in terms of speed and responsivity) high-speed metal-semiconductor-metal (MSM) photodiodes made with GaAs:Er. Pseudomorphic AlGaAs/ InGaAs modulation doped field effect transistors (MODFETs) (for high-speed MSM-FET monolithically integrated optical photoreceivers) were also fabricated using a GaAs:Er buffer layer which substantially reduced backgating effects in these devices.

Sethi, S.; Bhattacharya, P. K.

1996-03-01

103

Lattice-Mismatched III-V Epilayers for High-Efficiency Photovoltaics  

SciTech Connect

The project focused on development of new approaches and materials combinations to expand and improve the quality and versatility of lattice-mismatched (LMM) III-V semiconductor epilayers for use in high-efficiency multijunction photovoltaic (PV) devices. To address these goals, new capabilities for materials synthesis and characterization were established at SDSM&T that have applications in modern opto- and nano-electronics, including epitaxial crystal growth and transmission electron microscopy. Advances were made in analyzing and controlling the strain profiles and quality of compositional grades used for these technologies. In particular, quaternary compositional grades were demonstrated, and a quantitative method for characteristic X-ray analysis was developed. The project allowed enhanced collaboration between scientists at NREL and SDSM&T to address closely related research goals, including materials exchange and characterization.

Ahrenkiel, Scott Phillip [South Dakota School of Mines & Technology] [South Dakota School of Mines & Technology

2013-06-30

104

Scanning tunneling microscopy of III-V compound semiconductor (001) surfaces  

NASA Astrophysics Data System (ADS)

While the (001) oriented substrate of compound semiconductors are most commonly used in fabrication of wireless and opto-electronic devices by molecular beam epitaxy, metallorganic chemical vapor deposition and related techniques, their surface structures have been puzzling from the beginning of the development of the techniques with which these materials are artificially prepared. This paper reviews the advances in comprehensive understanding of the geometric and electronic structures and chemical properties of the principal reconstructions found on the (001) surface of III-V compound semiconductors including arsenides, such as GaAs, InAs and AlAs, phosphides, such as.GaP and InP, antimonides, such as GaSb, AlSb and InSb, and also nitrides (GaN), with the emphasis on the GaAs(001), during the first decade following the invention of scanning tunneling microscopy.

Xue, Qi-Kun; Hashizume, T.; Sakurai, T.

1997-10-01

105

Parallel nanogap fabrication with nanometer size control using III-V semiconductor epitaxial technology.  

PubMed

A nanogap fabrication process using strained epitaxial III-V beams is reported. The process is highly reproducible, allowing parallel fabrication and nanogap size control. The beams are fabricated from MBE-grown (GaAs/GaP)/AlGaAs strained heterostructures, standard e-beam lithography and wet etching. During the wet etching process, the relaxation of the accumulated stress at the epitaxial heterostructure produces a controlled beam breakage at the previously defined beam notch. After the breakage, the relaxed strain is proportional to the beam length, allowing nanogap size control. The starting structure is similar to a mechanically adjustable break junction but the stress causing the breakage is, in this case, built into the beam. This novel technique should be useful for molecular-scale electronic devices. PMID:21828698

Fernández-Martínez, Iván; González, Yolanda; Briones, Fernando

2008-07-01

106

Long-wave infrared (LWIR) detectors based on III-V materials  

NASA Technical Reports Server (NTRS)

Future NASA missions for earth observation and planetary science require large photovoltaic detector arrays with high performance in the long wavelength region to 18 microns and at operating temperatures above 65 K where single-cycle long-life cryocoolers are being developed. Since these detector array requirements exceed the state of current HgCdTe technology, alternative detector materials are being investigated as a possible option for future missions. Advanced growth techniques (e.g., MBE and MOCVD) of column III-V semiconductors have opened opportunities for engineering new detector materials and device structures. The technical approaches under investigation at JPL (with university and industry participation) include: quantum well infrared photodetectors, heterojunction internal photoemission (HIP) photodetectors, type-II strained layer superlattices, and nipi doping superlattices. Each of these options are briefly described with some of their pros and cons. A more detailed description is given for the HIP approach being pioneered at JPL.

Maserjian, Joseph

1991-01-01

107

Direct integration of III-V compound semiconductor nanostructures on silicon by selective epitaxy.  

PubMed

Direct integration of III-V compound semiconductor (GaAs) on silicon (Si) substrates has been demonstrated using selective epitaxy on patterned substrates. GaAs was grown directly on patterned (001), (011), and (111) Si substrates covered with 60 nm thick thermally grown SiO(2). After growth, GaAs crystals with both dot and wire shapes show preferred {011} facets. GaAs grown on particular wire patterns which are parallel to {011} surfaces shows uniform nanowire structure. Transmission electron microscopy shows dislocation-free GaAs with low density of anti-phase domain boundaries along [111] directions. Metal-oxide-semiconductor structures with aluminum oxide as gate dielectric were fabricated using GaAs nanowires on Si. Capacitance-voltage measurements show clear inversion and accumulation. PMID:19417293

Zhao, Zuoming; Yadavalli, Kameshwar; Hao, Zhibiao; Wang, Kang L

2009-01-21

108

Ultraviolet photosulfidation of III-V compound semiconductors for electronic passivation  

SciTech Connect

A new vacuum-compatible passivation technique for III-V compound semiconductors has been developed. Sulfur passivation of GaAs(100) is produced by ultraviolet photolytic deposition of a sulfide species from vapor phase elemental sulfur. Photoluminescence studies of the photosulfided GaAs reveal a degree of passivation greater than or equal to that produced by conventional (NH{sub 4}{sub 2}S) solution treatment. X-ray Photoelectron Spectroscopy has shown that the sulfur resides on the surface as a single reduced sulfur species, either as sulfide of disulfide, indicating complete fragmentation of the S{sub 8} ring by UV light in proximity to the surface. The degree of photosulfidation depends strongly on surface preparation as demonstrated by the described surface oxide removal studies.

Zavadil, K.R.; Ashby, C.I.H.; Howard, A.J.; Hammons, B.E.

1993-10-01

109

Development of molecular beam epitaxy technology for III–V compound semiconductor heterostructure devices  

SciTech Connect

Molecular beam epitaxy (MBE) is a versatile ultrahigh vacuum technique for growing multiple epitaxial layers of semiconductor crystals with high precision. The extreme control of the MBE technique over composition variation, interface sharpness, impurity doping profiles, and epitaxial layer thickness to the atomic level makes it possible to demonstrate a wide variety of novel semiconductor structures. Since its invention nearly 40 years ago, the MBE technique has evolved from a laboratory apparatus for exploring new materials and novel devices to a favored tool for the mass production of III–V high-speed devices. This paper will review some of the past developments in this technology and propose an outlook of future developments.

Cheng, K. Y. [Department of Electrical Engineering, National Tsing Hua University, 101 Kuang Fu Road, Section 2, Hsinchu, Taiwan 30013 (China)] [Department of Electrical Engineering, National Tsing Hua University, 101 Kuang Fu Road, Section 2, Hsinchu, Taiwan 30013 (China)

2013-09-15

110

In situ access to the dielectric anisotropy of buried III-V/Si(100) heterointerfaces  

NASA Astrophysics Data System (ADS)

We derive an analytical expression to extract the III-V/Si(100) surface and interface dielectric anisotropy from multisample optical in situ data. Based on the established preparation of P-rich GaP/Si(100) and GaP(100) surfaces in vapor-phase ambient, thin GaP films on Si(100) serve as a model system, where we demonstrate the decomposition of reflection anisotropy spectra to obtain surface and interface signals. The resulting surface dielectric anisotropy of P-rich GaP/Si(100) agrees well with that of a homoepitaxial P-rich GaP(100) reference due to consideration of antiphase disorder in our analytical approach. Hence, we are able to calculate interface dielectric anisotropy spectra of individual GaP/Si(100) samples. Their characteristic line shape provides in situ access to nucleation mechanisms in polar-on-nonpolar heteroepitaxy.

Supplie, Oliver; Hannappel, Thomas; Pristovsek, Markus; Döscher, Henning

2012-07-01

111

Atomic-scale variability and control of III-V nanowire growth kinetics.  

PubMed

In the growth of nanoscale device structures, the ultimate goal is atomic-level precision. By growing III-V nanowires in a transmission electron microscope, we measured the local kinetics in situ as each atomic plane was added at the catalyst-nanowire growth interface by the vapor-liquid-solid process. During growth of gallium phosphide nanowires at typical V/III ratios, we found surprising fluctuations in growth rate, even under steady growth conditions. We correlated these fluctuations with the formation of twin defects in the nanowire, and found that these variations can be suppressed by switching to growth conditions with a low V/III ratio. We derive a growth model showing that this unexpected variation in local growth kinetics reflects the very different supply pathways of the V and III species. The model explains under which conditions the growth rate can be controlled precisely at the atomic level. PMID:24436416

Chou, Y-C; Hillerich, K; Tersoff, J; Reuter, M C; Dick, K A; Ross, F M

2014-01-17

112

Analytical modeling of III-V solar cells close to the fundamental limit  

NASA Astrophysics Data System (ADS)

A highly effective strategy of photon management is to use a back surface reflector. In this work, we present a full analytical model incorporating effects from both the modified generation function and photon recycling in GaAs solar cells with a BSR. We discuss the impact of doping concentration, non-radiative recombination, solar cell dimensions and BSR reflectivity on the efficiency, and compare the prediction of the device models to experimental data measured on GaAs devices. We use the model to predict the performance of alternative III-V materials, such as InP, comparing the predicted performance to state-of-the-art GaAs solar cells.

Lumb, Matthew P.; Steiner, Myles A.; Geisz, John F.; Walters, Robert J.

2014-03-01

113

Towards a low noise class-A hybrid III-V/silicon laser  

NASA Astrophysics Data System (ADS)

We describe a hybrid III-V on Silicon laser designed for low noise class-A dynamics. The laser is based on an InP active region and a passive silicon region integrated in a long laser cavity. High-Q ring resonators are used as optical filters in order to achieve single frequency operation. A fiber-coupled output power of 4.6 mW and a 55 dB side mode suppression ratio are obtained. For a pumping rate of 5.2, the hybrid laser exhibits a Relative Intensity Noise below -145 dB/Hz over a wide frequency bandwidth, from 100 MHz to 40 GHz but still suffers from some noise excess due to relaxation oscillations phenomena and side modes noise. The optimization of the laser cavity design is discussed in order to reach class-A dynamics while reducing residual noise excess.

Girard, Nils; Baili, Ghaya; Nouchi, Pascale; Dolfi, Daniel; Le Liepvre, Alban; Accard, Alain; Kaspar, Peter; Make, Dalila; Charbonnier, Philippe; Mallecot, Franck; Faugeron, Mickael; Van Dijk, Frederic; Duan, Guang-Hua; Olivier, Ségolène; Malhouitre, Stephan; Kopp, Christophe

2014-05-01

114

New III-V cell design approaches for very high efficiency  

SciTech Connect

This report describes progress during the first year of a three-year project. The objective of the research is to examine new design approaches for achieving very high conversion efficiencies. The program is divided into two areas. The first centers on exploring new thin-film approaches specifically designed for III-V semiconductors. The second area centers on exploring design approaches for achieving high conversion efficiencies without requiring extremely high quality material. Research activities consisted of an experimental study of minority carrier recombination in n-type, metal-organic chemical vapor deposition (MOCVD)-deposited GaAs, an assessment of the minority carrier lifetimes in n-GaAs grown by molecular beam epitaxy, and developing a high-efficiency cell fabrication process.

Lundstrom, M.S.; Melloch, M.R.; Lush, G.B.; O'Bradovich, G.J.; Young, M.P. (Purdue Univ., Lafayette, IN (United States))

1993-01-01

115

Strain engineering of epitaxially transferred, ultrathin layers of III-V semiconductor on insulator  

NASA Astrophysics Data System (ADS)

Strain state of ultrathin InAs-on-insulator layers obtained from an epitaxial transfer process is studied. The as-grown InAs epilayer (10-20 nm thick) on the GaSb/AlGaSb source wafer has the expected ˜0.62% tensile strain. The strain is found to fully release during the epitaxial transfer of the InAs layer onto a Si/SiO2 substrate. In order to engineer the strain of the transferred InAs layers, a ZrOx cap was used during the transfer process to effectively preserve the strain. The work presents an important advance toward the control of materials properties of III-V on insulator layers.

Fang, Hui; Madsen, Morten; Carraro, Carlo; Takei, Kuniharu; Kim, Ha Sul; Plis, Elena; Chen, Szu-Ying; Krishna, Sanjay; Chueh, Yu-Lun; Maboudian, Roya; Javey, Ali

2011-01-01

116

Use of 3-aminopropyltriethoxysilane deposited from aqueous solution for surface modification of III-V materials  

NASA Astrophysics Data System (ADS)

Focal plane arrays of strained layer superlattices (SLSs) composed of InAs/GaSb are excellent candidates for infrared imaging, but one key factor limiting their utility is the lack of a surface passivation technique capable of protecting the mesa sidewall from degradation. Along these lines, we demonstrate the use of aqueous 3-aminopropyl triethoxysilane (APTES) deposited as a surface functionalizing agent for subsequent polymer passivation on InAs and GaSb surfaces following a HCl/citric acid procedure to remove the conductive oxide In2O3. Using atomic force microscopy, variable angle spectroscopic ellipsometry, X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption fine structure (NEXAFS), and modeling with density functional theory (DFT), we demonstrate that APTES films can successfully be deposited on III-V substrates by spin coating and directly compare these films to those deposited on silicon substrates. The HCl/citric acid surface preparation treatment is particularly effective at removing In2O3 without the surface segregation of In oxides observed from use of HCl alone. However, HCl/citric acid surface treatment method does result in heavy oxidation of both Ga and Sb, accompanied by segregation of Ga oxide to the surface. Deposited APTES layer thickness did not depend on the substrate choice, and thicknesses between 1 and 20 nm were obtained for APTES solution concentrations ranging from 0.1 to 2.5 vol %. XPS results for the N1s band of APTES showed that the content of ionic nitrogen was high (?50%) for the thinnest films (?1 nm), and decreased with increasing film thickness. These results indicate that APTES can indeed be used to form a silane surface layer to cover III-V materials substrates. Such APTES silane layers may prove useful in surface passivation of these materials alone, or as surface functionalizing agents for subsequent covalent binding with polymer overlayers like polyimide.

Knorr, Daniel B., Jr.; Williams, Kristen S.; Baril, Neil F.; Weiland, Conan; Andzelm, Jan W.; Lenhart, Joseph L.; Woicik, Joseph C.; Fischer, Daniel A.; Tidrow, Meimei Z.; Bandara, Sumith V.; Henry, Nathan C.

2014-11-01

117

Silicon/III-V laser with super-compact diffraction grating for WDM applications in electronic-photonic integrated circuits.  

PubMed

We have demonstrated a heterogeneously integrated III-V-on-Silicon laser based on an ultra-large-angle super-compact grating (SCG). The SCG enables single-wavelength operation due to its high-spectral-resolution aberration-free design, enabling wavelength division multiplexing (WDM) applications in Electronic-Photonic Integrated Circuits (EPICs). The SCG based Si/III-V laser is realized by fabricating the SCG on silicon-on-insulator (SOI) substrate. Optical gain is provided by electrically pumped heterogeneous integrated III-V material on silicon. Single-wavelength lasing at 1550 nm with an output power of over 2 mW and a lasing threshold of around 150 mA were achieved. PMID:21369017

Wang, Yadong; Wei, Yongqiang; Huang, Yingyan; Tu, Yongming; Ng, Doris; Lee, Cheewei; Zheng, Yunan; Liu, Boyang; Ho, Seng-Tiong

2011-01-31

118

Compact modeling of the shift between classical and quantum threshold voltages in a III-V nanowire  

NASA Astrophysics Data System (ADS)

In this work, a quantum correction model for the threshold voltage of cylindrical nanowires is presented. Using a cylindrical self-consistent 1-D Poisson-Schrödinger (PS) numerical resolution of the charge profile as a reference, a generalized and compact Hänsch’s formula is proposed and systematically validated on simulation. As an example of application, this equation is then applied to III-V nanowires and to the study of the threshold voltage variability of these devices. The results suggest an increased variability due to the small mass of III-V semiconductors and to the larger quantum confinement of nanowire architectures.

Hiblot, G.; Rafhay, Q.; Boeuf, F.; Ghibaudo, G.

2014-10-01

119

Studies of III-V compounds is the megabar range. Final report, July 15, 1993--July 14, 1996.  

National Technical Information Service (NTIS)

The core of this work was the study of phase transformations and equation of state of the III-V compounds. The research studies provided an excellent test of theories of molecular bonding and this work was carefully followed by several well known theorist...

A. L. Ruoff

1997-01-01

120

Interface engineering and chemistry of Hf-based high-k dielectrics on III-V substrates  

NASA Astrophysics Data System (ADS)

Recently, III-V materials have been extensively studied as potential candidates for post-Si complementary metal-oxide-semiconductor (CMOS) channel materials. The main obstacle to implement III-V compound semiconductors for CMOS applications is the lack of high quality and thermodynamically stable insulators with low interface trap densities. Due to their excellent thermal stability and relatively high dielectric constants, Hf-based high-k gate dielectrics have been recently highlighted as the most promising high-k dielectrics for III-V-based devices. This paper provides an overview of interface engineering and chemistry of Hf-based high-k dielectrics on III-V substrates. We begin with a survey of methods developed for generating Hf-based high-k gate dielectrics. To address the impact of these hafnium based materials, their interfaces with GaAs as well as a variety of semiconductors are discussed. After that, the integration issues are highlighted, including the development of high-k deposition without Fermi level pinning, surface passivation and interface state, and integration of novel device structure with Si technology. Finally, we conclude this review with the perspectives and outlook on the future developments in this area. This review explores the possible influences of research breakthroughs of Hf-based gate dielectrics on the current and future applications for nano-MOSFET devices.

He, Gang; Chen, Xiaoshuang; Sun, Zhaoqi

2013-03-01

121

Design and Growth of III-V on Si Microwire Array Tandem Solar Cells Christopher T. Chen1  

E-print Network

Design and Growth of III-V on Si Microwire Array Tandem Solar Cells Christopher T. Chen1 , Daniel B Abstract -- Tandem Ga1-xInxP/Si microwire array solar cells are a route towards a high efficiency, low cost, flexible, wafer- free solar technology. Coupled full-field optical and device physics simulations of a Ga0

Atwater, Harry

122

A new, efficient approach to the large-scale thermal modeling of III-V devices and integrated circuits  

Microsoft Academic Search

An efficient approach is presented to the self-consistent, steady-state, large-scale thermal modeling of III-V devices, allowing for multilayered substrates with non-linear thermal properties, thermally conductive metallizations and via holes. Examples are discussed to highlight the model features and to compare the model results with experimental data

F. Bonani; G. Ghione; M. Pirola; C. U. Naldi

1993-01-01

123

Exploring cryogenic focused ion beam milling as a Group III-V device fabrication tool  

NASA Astrophysics Data System (ADS)

In this paper, we compare the features observed on a Group III-V strained layer superlattice (SLS) materials system as a result of room temperature Ga+ focused ion beam (FIB) milling to the features observed as a result of cryogenic FIB (cryo-FIB) milling at -135 °C under the same beam conditions (30 kV:1 nA). The features on the cryo-FIB milled material were observed both when the material was still cold and after it returned to room temperature. Although cryo-FIB milling yielded patterned features that were initially cleaner than comparable features defined by FIB milling at room temperature, we found that both room temperature FIB milling and cryo-FIB milling with subsequent sample warm-up resulted in the formation of Group III enriched features. These findings suggest that the structural and chemical properties of features fabricated by cryo-FIB milling are temperature-dependent, which is an important consideration when it comes to device fabrication. These dependencies will need to be better understood and controlled if cryo-FIB milling is to have future applications in this area.

Dolph, Melissa Commisso; Santeufemio, Christopher

2014-06-01

124

Development and operation of research-scale III-V nanowire growth reactors  

NASA Astrophysics Data System (ADS)

III-V nanowires are useful platforms for studying the electronic and mechanical properties of materials at the nanometer scale. However, the costs associated with commercial nanowire growth reactors are prohibitive for most research groups. We developed hot-wall and cold-wall metal organic vapor phase epitaxy reactors for the growth of InAs nanowires, which both use the same gas handling system. The hot-wall reactor is based on an inexpensive quartz tube furnace and yields InAs nanowires for a narrow range of operating conditions. Improvement of crystal quality and an increase in growth run to growth run reproducibility are obtained using a homebuilt UHV cold-wall reactor with a base pressure of 2×10-9 Torr. A load lock on the UHV reactor prevents the growth chamber from being exposed to atmospheric conditions during sample transfers. Nanowires grown in the cold-wall system have a low defect density, as determined using transmission electron microscopy, and exhibit field effect gating with mobilities approaching 16 000 cm2/(V s).

Schroer, M. D.; Xu, S. Y.; Bergman, A. M.; Petta, J. R.

2010-02-01

125

Dynamical properties of Sb- and Bi-covered (110) surfaces of III-V compounds  

NASA Astrophysics Data System (ADS)

We present results from plane-wave pseudopotential calculations and density-functional perturbation theory applied to investigate the surface phonon dispersion of (110) surfaces of InAs and InP covered by monolayers of Sb and Bi. The importance of vibrational spectroscopy for the investigation of structural properties is demonstrated for the Bi-covered InAs(110) surface which forms a (1×1) and, in addition, a (1×2) phase. Our calculations predict two prominent low-frequency modes which are fingerprints of the missing-row reconstruction recently proposed for the (1×2) phase. A comparison of the modes allows us to analyse systematic trends and to study the physical origin of vibrational states occurring on clean and adsorbate-covered Owen(underscore)Haskins(at)espicom.comIII-V(110) surfaces. The electronic band structure computed for the (1×1) and (1×2) phases of the Bi-covered InAs(110) surface is in agreement with experimental data. Compared with the (1×1) phase, we find a much smaller band gap for the (1×2) reconstruction.

Fritsch, Jürgen; Dvorák, Alexander; Arnold, Marcus; Schröder, Ulrich

2002-06-01

126

Gate control of Berry phase in III-V semiconductor quantum dots  

NASA Astrophysics Data System (ADS)

We analyze the Berry phase in III-V semiconductor quantum dots (QDs). We show that the Berry phase is highly sensitive to electric fields arising from the interplay between the Rashba and Dresselhaus spin-orbit (SO) couplings. We report that the accumulated Berry phase can be induced from other available quantum states that differ only by one quantum number of the corresponding spin state. The sign change in the g-factor due to the penetration of Bloch wave functions into the barrier materials can be reflected in the Berry phase. We provide characteristics of the Berry phase for three different length scales (spin-orbit length, hybrid orbital length, and orbital radius). We solve the time-dependent Schrödinger equation by utilizing the Feynman disentangling technique, and we investigate the evolution of spin dynamics during the adiabatic transport of QDs in the two-dimensional plane. Our results can pave the way to building a topological quantum computer in which the Berry phase can be engineered and be manipulated with the application of the spin-orbit couplings through gate-controlled electric fields.

Prabhakar, Sanjay; Melnik, Roderick; Bonilla, Luis L.

2014-06-01

127

Ion implantation for high performance III-V JFETS and HFETS  

SciTech Connect

Ion implantation has been an enabling technology for realizing many high performance electronic devices in III-V semiconductor materials. We report on advances in ion implantation processing for GaAs JFETs (joint field effect transistors), AlGaAs/GaAs HFETs (heterostructure field effect transistors), and InGaP or InAlP-barrier HFETs. The GaAs JFET has required the development of shallow p-type implants using Zn or Cd with junction depths down to 35 nm after the activation anneal. Implant activation and ionization issues for AlGaAs are reported along with those for InGaP and InAlP. A comprehensive treatment of Si-implant doping of AlGaAs is given based on donor ionization energies and conduction band density-of-states dependence on Al-composition. Si and Si+P implants in InGaP are shown to achieve higher electron concentrations than for similar implants in AlGaAs due to absence of the deep donor level. An optimized P co- implantation scheme in InGaP is shown to increase the implanted donor saturation level by 65%.

Zolper, J.C.; Baca, A.G.; Sherwin, M.E.; Klem, J.F.

1996-06-01

128

30 CFR 57.22234 - Actions at 1.0 percent methane (I-A, I-B, III, V-A, and V-B mines).  

...2014-07-01 false Actions at 1.0 percent methane (I-A, I-B, III, V-A, and V-B...NONMETAL MINES Safety Standards for Methane in Metal and Nonmetal Mines Ventilation § 57.22234 Actions at 1.0 percent methane (I-A, I-B, III, V-A, and...

2014-07-01

129

Alloy  

NASA Astrophysics Data System (ADS)

The Mg98.5Gd1Zn0.5 alloy produced by a powder metallurgy route was studied and compared with the same alloy produced by extrusion of ingots. Atomized powders were cold compacted and extruded at 623 K and 673 K (350 °C and 400 °C). The microstructure of extruded materials was characterized by ?-Mg grains, and Mg3Gd and 14H-LPSO particles located at grain boundaries. Grain size decreased from 6.8 ?m in the extruded ingot, down to 1.6 ?m for powders extruded at 623 K (350 °C). Grain refinement resulted in an increase in mechanical properties at room and high temperatures. Moreover, at high temperatures the PM alloy showed superplasticity at high strain rates, with elongations to failure up to 700 pct.

Cabeza, Sandra; Garcés, Gerardo; Pérez, Pablo; Adeva, Paloma

2014-07-01

130

In-situ plasma cleaning of stainless steel III-V MOCVD growth systems  

NASA Astrophysics Data System (ADS)

A plasma enhanced, in-situ, dry etching process for the cleaning of stainless steel III-V Metal Organic Chemical Vapor Deposition growth systems was investigated as a function of etchant gas, flow rate, electrode configuration, power density and plasma frequency. The plasma enhanced etching process was investigated using Ar, CH4 (5% in H2), CCl2F2 (Freon 12)/Ar and Cl2/Ar plasmas with flows varying from 5 to 25 seem. The plasma was excited using three electrode configurations, and two radio frequency generators (90 460 KHz and 13.56 MHz), singly and in combination. The plasma power was varied over the range from 200 to 700 Watts (˜0.2W/cm2 0.7W/cm2). The etching rates of GaAs, InP, As, and Mo were measured using a weight difference method. The Cl2/Ar plasmas exhibited etching rates typically 5 to 10 times greater than that of CCl2F2 plasmas, which in turn is several times greater than that of the other etchant gases investigated. At 400 W, elemental As etch rates, as high as ˜180 ?m/hr and ˜20 ?m/hr were achieved using Cl2 and CCl2F2 plasmas, respectively. InP/GaAs etch rates using Cl2 were ˜30 ?m/hr and using CCl2F2 were ˜7 ?m/hr. Plasma characteristics and etch rate measurements are reported. The in-situ process investigated is a safe, cost effective and an efficient method for increasing reactor uptime.

Li, S.; Tompa, G. S.; Moy, K.; West, S. B.; Nelson, C. R.; Stall, R. A.; Burnham, R.; Smith, S.

1992-02-01

131

Difference in formation of ferromagnetic MnAs nanoclusters on III-V semiconducting nanowire templates  

NASA Astrophysics Data System (ADS)

The authors report on the differences in ferromagnetic MnAs nanocluster formation on GaAs, GaAs/AlGaAs, GaAs/GaAsP, and InAs nanowire templates by combing selective-area metal-organic vapor phase epitaxy of semiconducting nanowires and endotaxial nanoclustering of MnAs. To characterize the dependences of MnAs nanocluster formation on semiconducting materials of the nanowire templates, GaAs, GaAs/AlGaAs core-shell, and GaAs/GaAsP core-shell nanowires have been grown at 750 °C, whereas InAs nanowires have been grown at 580 °C. MnAs nanoclusters are commonly and most frequently formed at six ridges between two {0-11} crystal facets on hexagonal prisms of III-V semiconducting nanowires. That is presumably because many atomic steps exist between the crystal facets. Here, MnAs nanoclusters are grown "into" the nanowires, as a result of the phenomenon of "endotaxy". Manganese atoms on the nanowires surface form chemical bonds mainly with arsenic atoms of the nanowires, because only manganese organometallic source and hydrogen are supplied, i.e. no supply of arsenic hydride source during the endotaxy of MnAs. In the case of GaAs/GaAsP core-shell and InAs nanowires, however, MnAs nanoclusters are formed on the top {111}B surfaces of the nanowires, as well as at six ridges of the hexagonal prisms. The results obtained in the current work possibly show that the endotaxy of MnAs depends on the thermal stability of the nanowires and/or the strength of atomic bonds in the host materials of nanowires.

Hara, Shinjiro; Fujimagari, Hiromu; Sakita, Shinya; Yatago, Masatoshi

2013-09-01

132

Investigation of the design parameters of quantum dot enhanced III-V solar cells  

NASA Astrophysics Data System (ADS)

The incorporation of nanostructures, such as quantum dots (QD), into the intrinsic region of III-V solar cells has been proposed as a potential route towards boosting conversion efficiencies with immediate applications in concentrator photovoltaic and space power systems. Necessary to the optimization process of this particular class of solar cells is the ability to correlate nanoscale properties with macroscopic device characteristics. To this purpose, the physics-based software Crosslight APSYS has been developed to investigate the design parameters of QD enhanced solar cells with particular focus on the InAs/GaAs system. This methodology is used to study how nanoscale variables, including size, shape and material compositions, influence photovoltaic performance. In addition, device-level engineering of the nanostructures is explored in optimizing the overall device response. Specifically, the effect of the position of the QDs within the intrinsic regions is investigated. Preliminary simulations suggest strategically placing the QDs off-center reduces non-radiative recombination and thereby the dark saturation current, contributing to a marked increase in opencircuit voltage and fill factor. The short-circuit current remains unchanged in the high field region resulting in an increase in overall conversion efficiency. To further explore this finding, a series of three samples with the QDs placed in the center and near the doped regions of a pin-GaAs solar cell have been grown using MOCVD, fabricated and fully characterized. Contrary to predictions, the emitter-shifted devices exhibit a marked decrease in open-circuit voltage and fill factor. This behavior is attributed to non-negligible n-type background doping in the intrinsic region which shifts the region of maximum recombination towards the p-type emitter.

Driscoll, Kristina; Bennett, Mitchell; Polly, Stephen; Forbes, David V.; Hubbard, Seth M.

2013-03-01

133

A III-V nanowire channel on silicon for high-performance vertical transistors.  

PubMed

Silicon transistors are expected to have new gate architectures, channel materials and switching mechanisms in ten years' time. The trend in transistor scaling has already led to a change in gate structure from two dimensions to three, used in fin field-effect transistors, to avoid problems inherent in miniaturization such as high off-state leakage current and the short-channel effect. At present, planar and fin architectures using III-V materials, specifically InGaAs, are being explored as alternative fast channels on silicon because of their high electron mobility and high-quality interface with gate dielectrics. The idea of surrounding-gate transistors, in which the gate is wrapped around a nanowire channel to provide the best possible electrostatic gate control, using InGaAs channels on silicon, however, has been less well investigated because of difficulties in integrating free-standing InGaAs nanostructures on silicon. Here we report the position-controlled growth of vertical InGaAs nanowires on silicon without any buffering technique and demonstrate surrounding-gate transistors using InGaAs nanowires and InGaAs/InP/InAlAs/InGaAs core-multishell nanowires as channels. Surrounding-gate transistors using core-multishell nanowire channels with a six-sided, high-electron-mobility transistor structure greatly enhance the on-state current and transconductance while keeping good gate controllability. These devices provide a route to making vertically oriented transistors for the next generation of field-effect transistors and may be useful as building blocks for wireless networks on silicon platforms. PMID:22854778

Tomioka, Katsuhiro; Yoshimura, Masatoshi; Fukui, Takashi

2012-08-01

134

III-V semiconductor waveguides for photonic functionality at 780 nm  

NASA Astrophysics Data System (ADS)

Photonic integrated circuits based on III-V semiconductor polarization-maintaining waveguides were designed and fabricated for the first time for application in a compact cold-atom gravimeter1,2 at an operational wavelength of 780 nm. Compared with optical fiber-based components, semiconductor waveguides achieve very compact guiding of optical signals for both passive functions, such as splitting and recombining, and for active functions, such as switching or modulation. Quantum sensors, which have enhanced sensitivity to a physical parameter as a result of their quantum nature, can be made from quantum gases of ultra-cold atoms. A cloud of ultra-cold atoms may start to exhibit quantum-mechanical properties when it is trapped and cooled using laser cooling in a magneto-optical trap, to reach milli-Kelvin temperatures. The work presented here focuses on the design and fabrication of optical devices for a quantum sensor to measure the acceleration of gravity precisely and accurately. In this case the cloud of ultra-cold atoms consists of rubidium (87Rb) atoms and the sensor exploits the hyperfine structure of the D1 transition, from an outer electronic state of 5 2S ½ to 5 2P3/2 which has an energy of 1.589 eV or 780.241 nm. The short wavelength of operation of the devices dictated stringent requirements on the Molecular Beam Epitaxy (MBE) and device fabrication in terms of anisotropy and smoothness of plasma etch processes, cross-wafer uniformities and alignment tolerances. Initial measurements of the optical loss of the polarization-maintaining waveguide, assuming Fresnel reflection losses only at the facets, suggested a loss of 8 dB cm-1, a loss coefficient, ?, of 1.9 (+/-0.3) cm-1.

Maclean, Jessica O.; Greenaway, Mark T.; Campion, Richard P.; Pyragius, Tadas; Fromhold, T. Mark; Kent, Anthony J.; Mellor, Christopher J.

2014-03-01

135

A survey of ohmic contacts to III-V compound semiconductors  

SciTech Connect

A survey of ohmic contact materials and properties to GaAs, InP, GaN will be presented along with critical issues pertaining to each semiconductor material. Au-based alloys (e.g., GeAuNi for n-type GaAs) are the most commonly used contacts for GaAs and InP materials for both n- and p-type contacts due to the excellent contact resistivity, reliability, and usefulness over a wide range of doping levels. Research into new contacting schemes for these materials has focused on addressing limitations of the conventional Au-alloys in thermal stability, propensity for spiking, poor edge definition, and new approaches for a non-alloyed contact. The alternative contacts to GaAs and InP include alloys with higher temperature stability, contacts based on solid phase regrowth, and contacts that react with the substrate to form lower bandgap semiconductors alloys at the interface. A new area of contact studies is for the wide bandgap group III-Nitride materials. At present, low resistivity ohmic contact to p-type GaN has not been obtained primarily due to the large acceptor ionization energy and the resultant difficulty in achieving high free hole concentrations at room temperature. For n-type GaN, however, significant progress has been reported with reactive Ti-based metalization schemes or the use of graded InGaN layers. The present status of these approaches will be reviewed.

Baca, A.G.; Zolper, J.C.; Briggs, R.D. [Sandia National Labs., Albuquerque, NM (United States); Ren, F. [Lucent Technologies, Murray Hill, NJ (United States); Pearton, S.J. [Univ. of Florida, Gainesville, FL (United States)

1997-04-01

136

Ga-rich GaxIn1-xP solar cells on Si with 1.95 eV bandgap for ideal III-V/Si photovoltaics  

NASA Astrophysics Data System (ADS)

Theoretical models for III-V compound multijunction solar cells show that solar cells with bandgaps of 1.95-2.3 eV are needed to create ideal optical partitioning of the solar spectrum for device architectures containing three, four and more junctions. For III-V solar cells integrated with an active Si sub-cell, GaInP alloys in the Ga-rich regime are ideal since direct bandgaps of up to ~ 2.25 eV are achieved at lattice constants that can be integrated with appropriate GaAsP, SiGe and Si materials, with efficiencies of almost 50% being predicted using practical solar cell models under concentrated sunlight. Here we report on Ga-rich, lattice-mismatched Ga0.57In0.43P sub-cell prototypes with a bandgap of 1.95 eV grown on tensile step-graded metamorphic GaAsyP1-y buffers on GaAs substrates. The goal is to create a high bandgap top cell for integration with Si-based III-V/Si triple-junction devices. Excellent carrier collection efficiency was measured via internal quantum efficiency measurements and with their design being targeted for multijunction implementation (i.e. they are too thin for single junction cells), initial cell results are encouraging. The first generation of identical 1.95 eV cells on Si were fabricated as well, with efficiencies for these large bandgap, thin single junction cells ranging from 7% on Si to 11% on GaAs without antireflection coatings, systematically tracking the change in defect density as a function of growth substrate.

Ratcliff, Christopher; Grassman, T. J.; Carlin, J. A.; Chmielewski, D. J.; Ringel, S. A.

2014-03-01

137

Gold-Free Ternary III–V Antimonide Nanowire Arrays on Silicon: Twin-Free down to the First Bilayer  

PubMed Central

With the continued maturation of III–V nanowire research, expectations of material quality should be concomitantly raised. Ideally, III–V nanowires integrated on silicon should be entirely free of extended planar defects such as twins, stacking faults, or polytypism, position-controlled for convenient device processing, and gold-free for compatibility with standard complementary metal–oxide–semiconductor (CMOS) processing tools. Here we demonstrate large area vertical GaAsxSb1–x nanowire arrays grown on silicon (111) by molecular beam epitaxy. The nanowires’ complex faceting, pure zinc blende crystal structure, and composition are mapped using characterization techniques both at the nanoscale and in large-area ensembles. We prove unambiguously that these gold-free nanowires are entirely twin-free down to the first bilayer and reveal their three-dimensional composition evolution, paving the way for novel infrared devices integrated directly on the cost-effective Si platform. PMID:24329502

2013-01-01

138

In situ observation of ellipsometry monolayer oscillations of metalorganic vapor-phase epitaxy-grown III–V compound materials  

Microsoft Academic Search

Oscillations of the ellipsometry signal were clearly seen during metalorganic vapor-phase epitaxy (MOVPE) of III–V materials under high sample rotation at 1400rpm. The ellipsometric signal oscillated at a period corresponding to 1 monolayer of MOVPE growth. Agreement was excellent between growth rate data from the oscillation period and that from thickness measurements after growth (deviation: <1%). Oscillations correlated with the

Jeong-Sik Lee; Shigeo Sugou; Yasuaki Masumoto

2000-01-01

139

Self-assembled monolayers of Lewis bases: effects on surface and interfacial electronic properties in III-V optical semiconductors  

Microsoft Academic Search

The nature and disposition of surface states can have a dramatic effect on the near-surface electronic properties in semiconductor heterostructures. In particular the lack of a well-defined surface oxide in III-V materials means that surface band bending can cause surface recombination velocities to be up to 103 larger than in Si-based materials. Raman scattering by coupled longitudinal optic phonons and

J. F. Dorsten; James E. Maslar; Y. Zhang; T. B. Rauchfuss; Paul W. Bohn; S. Agarwala; Ilesanmi Adesida; Catherine Caneau; Rajaram J. Bhat

1994-01-01

140

European PVSECE Glasgow, Scotland 2000 III-V SPACE SOLAR CELLS ON Si SUBSTRATES USING GRADED GeSi BUFFERS  

E-print Network

GeSi BUFFERS S.A. Ringel,a J.A. Carlin,a C.W. Leitz,b M. Currie,b T. Langdo,b E.A. Fitzgerald,b M, on Si wafers coated with compositionally-graded GeSi buffers. The combination of controlled strain relaxation within the GeSi buffer and monolayer-scale control of the III-V layer nucleation step is shown

141

Pressure-induced structural change of liquid InAs and the systematics of liquid III-V compounds  

Microsoft Academic Search

To understand the pressure-induced structural changes of liquid III-V compounds systematically, the pressure dependence of l-InAs was investigated using the synchrotron x-ray diffraction and an ab initio molecular-dynamics simulation (AIMD). The x-ray diffraction experiments revealed that the liquid changes its compression behavior from a nearly uniform type to a nonuniform one around 9 GPa. Corresponding to this change, the coordination

T. Hattori; K. Tsuji; Y. Miyata; T. Sugahara; F. Shimojo

2007-01-01

142

Pressure-induced structural change of liquid InAs and the systematics of liquid III-V compounds  

Microsoft Academic Search

To understand the pressure-induced structural changes of liquid III-V compounds systematically, the pressure dependence of l-InAs was investigated using the synchrotron x-ray diffraction and an ab initio molecular-dynamics simulation (AIMD). The x-ray diffraction experiments revealed that the liquid changes its compression behavior from a nearly uniform type to a nonuniform one around 9GPa . Corresponding to this change, the coordination

T. Hattori; K. Tsuji; Y. Miyata; T. Sugahara; F. Shimojo

2007-01-01

143

A thermodynamic analysis of native point defect and dopant solubilities in zinc-blende III-V semiconductors  

Microsoft Academic Search

A thermodynamic model is used to analyze available experimental data relevant to point defects in the binary zinc-blende III-V compounds (Ga,In)-(P,As,Sb). The important point defects and their complexes in each of the materials are identified and included in the model. Essentially all of the available experimental data on dopant solubility, crystal density, and lattice parameter of melt and solution grown

D. T. J. Hurle; D. T. J

2010-01-01

144

A thermodynamic analysis of native point defect and dopant solubilities in zinc-blende III–V semiconductors  

Microsoft Academic Search

A thermodynamic model is used to analyze available experimental data relevant to point defects in the binary zinc-blende III–V compounds (Ga,In)-(P,As,Sb). The important point defects and their complexes in each of the materials are identified and included in the model. Essentially all of the available experimental data on dopant solubility, crystal density, and lattice parameter of melt and solution grown

D. T. J. Hurle

2010-01-01

145

Nanometer-Scale Compositional Structure in III-V Semiconductor Heterostructures Characterized by Scanning Tunneling Microscopy  

SciTech Connect

Nanometer-scale compositional structure in InAsxP1.InNYAsxPl.x-Y/InP, grown by gas-source molecular-beam epitaxy and in InAsl-xPJkAsl$b#InAs heterostructures heterostructures grown by metal-organic chemical vapor deposition has been characterized using cross-sectional scanning tunneling microscopy. InAsxP1-x alloy layers are found to contain As-rich and P-rich clusters with boundaries formed preferentially within (T 11) and (111) crystal planes. Similar compositional structure is observed within InNYAsxP1-x-Y alloy layers. Imaging of InAsl-xp@Asl#bY superlattices reveals nanometer-scale clustering within both the hAsI-.p and InAsl$bY alloy layers, with preferential alignment of compositional features in the direction. Instances are observed of compositional structure correlated across a heterojunction interface, with regions whose composition corresponds to a smaller unstrained lattice, constant relative to the surrounding alloy material appearing to propagate across the interface.

Allerman, A.A.; Bi, W.G.; Biefeld, R.M.; Tu, C.W.; Yu, E.T.; Zuo, S.L.

1998-11-10

146

X-ray studies of III-V native oxide/gallium arsenide interface  

NASA Astrophysics Data System (ADS)

Three x-ray techniques have been employed to study wet-thermal native oxides of AlGaAs on GaAs. For these materials, a knowledge of the role of As at the interface is important for understanding Fermi-level pinning and is a central issue in efforts to develop high performance III-V MOSFET devices. This study is focused on how the As is incorporated at the interface, the interfacial strain, and related local structural parameters. X-ray absorption fine-structure spectroscopy (XAFS) was used to determine the site of residual As in wet-oxidized Al0.96Ga0.04As. In a ˜0.5 mum oxide film removed from its GaAs substrate, the remaining As atoms were found to be coordinated with oxygen in the form of amorphous As oxides, with a mixture of ˜80% As3+ and ˜20% As 5+ sites. These two sites are locally similar to As2O 3 and As2O5. Through this measurement, no evidence of interstitial or substitutional As, As precipitates, or GaAs was seen, implying that less than 10% of the As atoms are in these forms. To characterize the oxide structure in both the oxide film and the interfacial region, x-ray reflectivity and reflection-mode XAFS experiments were performed for a thin (300 A) oxidized AlxGa1-xAs (x = 0.96) film grown on GaAs. X-ray reflectivity studies showed that the composition of the surface oxidized film is not homogeneous as a function of depth. Reflection-mode XAFS, which uses the total external reflection of x-rays to confine an x-ray beam to the interfacial region, provided details of the local environment of As atoms at the interface of the oxide/GaAs. Analysis through this technique revealed that As atoms are in the form of mixed As oxides, with the local environment appearing to resemble As2O3 and As 2O5 in the interfacial region, which is consistent with the above observation from the isolated oxide film.

Cheong, Seong-Kyun

147

Update on III-V antimonide-based superlattice FPA development and material characterization  

NASA Astrophysics Data System (ADS)

Much progress has been made in the past 2 years in developing III-V antimonide-based superlattice infrared detectors and focal plane arrays (FPAs). In the area of detector material growth by molecular beam epitaxy, the wafer foundry group, helped by government-trusted entities and other partnering institutions, has leapfrogged many years of R&D effort to become the premier detector wafer supplier. The wafers produced are of high quality as measured by surface morphology, defect density, photoluminescence property, high-resolution X-ray diffraction, and diode current-voltage characteristics. In the area of detector design and FPA processing, the team-consisting of members from government laboratories, academia, and the FPA industry-has made rapid progress in device structure design, detector array etching, passivation, hybridization, and packaging. The progress is reflected in the steady reduction in FPA median darkcurrent density and improvement in median quantum efficiency, as well as reasonably low median noise-equivalent different temperature under 300 K scene background, when compared with the performance from some of the commercially available HgCdTe FPAs. In parallel with the FPA research and development effort, a small amount of funding has been devoted to measuring minority carrier lifetimes and to understanding life-killing defects and mechanisms of superlattice devices. Results of direct time-resolved photoluminescence measurement on superlattice absorbers indicate relatively short lifetimes (on the order of 30 ns) due to Shockley-Read-Hall mechanism. Modeling and curve fitting with diode current-voltage data indicate longer minority carrier lifetimes, although the best fit lifetime values differ greatly, possibly due to the difference in material quality and device structure. Several models or hypotheses have been proposed to explain experimental data. More data are required to validate these models and hypotheses. Further work is also necessary to reconcile the substantially different results from different groups and to truly understand the physics of minority carrier lifetimes, which is necessary to improve the lifetime and realize the theoretical promise of superlattice materials.

Zheng, Lucy; Tidrow, Meimei; Bandara, Sumith; Aitcheson, Leslie; Shih, Tiffany

2011-06-01

148

Exploration of GaInT1P and Related T1-Containing III-V Alloys for Photovoltaics  

SciTech Connect

This paper discusses the results of an attempt to grow GaInTlP for application as a 1-eV material for the third junction of a GaInP/GaAs/3rd-junction high-efficiency solar cell. Although early indications from the literature were promising, we are unable to produce crystalline homogeneous material, and so we conclude that this material is not a promising candidate for such applications as photovoltaics.

Friedman, D.J.; Kibbler, A.E.; Kurtz, S.R.

1998-11-02

149

Exploration of GaInTlP and related Tl-containing III-V alloys for photovoltaics  

SciTech Connect

This paper discusses the results of an attempt to grow GaInTlP for application as a 1-eV material for the third junction of a GaInP/GaAs/3rd-junction high-efficiency solar cell. Although early indications from the literature were promising, we are unable to produce crystalline homogeneous material, and so we conclude that this material is not a promising candidate for such applications as photovoltaics.

Friedman, D. J.; Kurtz, Sarah R.; Kibbler, A. E. [National Renewable Energy Laboratory, 1617 Cole Blvd., Golden, Colorado 80401 (United States)

1999-03-05

150

Silicon, germanium, and III-V-based tunneling devices for low-power applications  

NASA Astrophysics Data System (ADS)

While the scaling of transistor dimensions has kept pace with Moore's Law, the voltages applied to these devices have not scaled in tandem, giving rise to ever-increasing power/heating challenges in state-of-the-art integrated circuits. A primary reason for this scaling mismatch is due to the thermal limit---the 60 mV minimum required at room temperature to change the current through the device by one order of magnitude. This voltage scaling limitation is inherent in devices that rely on the mechanism of thermal emission of charge carriers over a gate-controlled barrier to transition between the ON- and OFF-states, such as in the case of conventional CMOS-based technologies. To overcome this voltage scaling barrier, several steep-slope device concepts have been pursued that have experimentally demonstrated sub-60-mV/decade operation since 2004, including the tunneling-field effect transistor (TFET), impact ionization metal-oxide-semiconductor (IMOS), suspended-gate FET (SG-FET), and ferroelectric FET (Fe-FET). These reports have excited strong efforts within the semiconductor research community toward the realization of a low-power device that will support continued scaling efforts, while alleviating the heating issues prevalent in modern computer chips. Literature is replete with claims of sub-60-mV/decade operation, but often with neglect to other voltage scaling factors that offset this result. Ideally, a low-power device should be able to attain sub-60-mV/decade inverse subthreshold slopes (S) employing low supply and gate voltages with a foreseeable path toward integration. This dissertation describes the experimental development and realization of CMOS-compatible processes to enhance tunneling efficiency in Si and Si/Ge nanowire (NW) TFETs for improved average S (S avg) and ON-currents (ION), and a novel, III-V-based tunneling device alternative is also proposed. After reviewing reported efforts on the TFET, IMOS, and SG-FET, the TFET is highlighted as the most promising low-power device candidate, owing to its potential to operate within small supply and gate voltage windows. In a critical analysis of the TFET, the advantages of 1-D systems, such as NWs, that can potentially access the so-called quantum capacitance limit (QCL) are discussed, and the remaining challenges for TFETs, such as source/channel doping abruptness, and material tradeoffs are considered. To this end, substantial performance improvements, as measured by Savg and ION, are experimentally realized in top-down fabricated Si NW-TFET arrays by systematically varying the annealing process used to enhance doping abruptness at the source/channel junction---a critical feature for maximizing tunneling efficiency. A combination of excimer laser annealing (ELA) and a low-temperature rapid thermal anneal (LT-RTA) are identified as an optimum choice, resulting in a 36% decrease in Savg as well as ˜500% improvement in ION over the conventional RTA approach. Extrapolation of these results with simulation shows that sub-60-mV/decade operation is possible on a Si-based platform for aggressively scaled, yet realistic, NW-TFET devices. Back-gated NW-FET measurements are also presented to assess the material quality of Ge/Si core/shell NW heterostructures with an n+-doped shell, and these NWs are found to be suitable building blocks for the fabrication of more efficient TFET systems, owing to the very abrupt doping profile at the shell/core (source/channel) interface and smaller bandgap/effective mass of the Ge channel. Finally, low current levels in conventional TFETs have recently led researchers to re-examine III-V heterostructures, particularly those with a broken-gap band alignment to allow a tunneling probability near unity. Along these lines, a novel tunnel-based alternative is presented---the broken-gap tunnel MOS---that enables a constant S < 60 mV/decade. The proposed device permits the use of 2-D device architectures without degradation of S given the source-controlled operation mechanism, while simultaneously avoiding undesirable nonlinearities in

Smith, Joshua T.

151

III-V compound semiconductor growth on silicon via germanium buffer and surface passivation for CMOS technology  

NASA Astrophysics Data System (ADS)

Integration of III-V compound semiconductors on silicon substrates has recently received much attention for the development of optoelectronic and high speed electronic devices. However, it is well known that there are some key challenges for the realization of III-V device fabrication on Si substrates: (i) the large lattice mismatch (in case of GaAs: 4.1%), and (ii) the formation of antiphase domain (APD) due to the polar compound semiconductor growth on non-polar elemental structure. Besides these growth issues, the lack of a useful surface passivation technology for compound semiconductors has precluded development of metal-oxide-semiconductor (MOS) devices and causes high surface recombination parasitics in scaled devices. This work demonstrates the growth of high quality III-V materials on Si via an intermediate Ge buffer layer and some surface passivation methods to reduce interface defect density for the fabrication of MOS devices. The initial goal was to achieve both low threading dislocation density (TDD) and low surface roughness on Ge-on-Si heterostructure growth. This was achieved by repeating a deposition-annealing cycle consisting of low temperature deposition + high temperature-high rate deposition + high temperature hydrogen annealing, using reduced-pressure chemical-vapor deposition (CVD). We then grew III-V materials on the Ge/Si virtual substrates using molecular-beam epitaxy (MBE). The relationship between initial Ge surface configuration and antiphase boundary formation was investigated using surface reflection high-energy electron diffraction (RHEED) patterns and atomic force microscopy (AFM) image analysis. In addition, some MBE growth techniques, such as migration enhanced epitaxy (MEE) and low temperature GaAs growth, were adopted to improve surface roughness and solve the Ge self-doping problem. Finally, an Al2O3 gate oxide layer was deposited using atomic-layer-deposition (ALD) system after HCl native oxide etching and ALD in-situ pre-annealing at 400 °C. A 100 nm thick aluminum layer was deposited to form the gate contact for a MOS device fabrication. C-V measurement results show very small frequency dispersion and 200-300 mV hysteresis, comparable to our best results for InGaAs/GaAs MOS structures on GaAs substrate. Most notably, the quasi-static C-V curve demonstrates clear inversion layer formation. I-V curves show a reasonable leakage current level. The inferred midgap interface state density, Dit, of 2.4 x 1012 eV-1cm-2 was calculated by combined high-low frequency capacitance method. In addition, we investigated the interface properties of amorphous LaAlO 3/GaAs MOS capacitors fabricated on GaAs substrate. The surface was protected during sample transfer between III-V and oxide molecular beam deposition (MBD) chambers by a thick arsenic-capping layer. An annealing method, a low temperature-short time RTA followed by a high temperature RTA, was developed, yielding extremely small hysteresis (˜ 30 mV), frequency dispersion (˜ 60 mV), and interface trap density (mid 1010 eV-1cm -2). We used capacitance-voltage (C-V) and current-voltage (I-V) measurements for electrical characterization of MOS devices, tapping-mode AFM for surface morphology analysis, X-ray photoelectron spectroscopy (XPS) for chemical elements analysis of interface, cross section transmission-electron microscopy (TEM), X-ray diffraction (XRD), secondary ion mass spectrometry (SIMS), and photoluminescence (PL) measurement for film quality characterization. This successful growth and appropriate surface treatments of III-V materials provides a first step for the fabrication of III-V optical and electrical devices on the same Si-based electronic circuits.

Choi, Donghun

152

Nanometer-scale compositional variations in III-V semiconductor heterostructures characterized by scanning tunneling microscopy  

E-print Network

, with such ordering appearing to yield significant reductions in the energy band gap.11 Understanding of and controlP heterostructures grown by gas-source molecular beam epitaxy and in InAs1 xPx/InAs1 ySby/InAs heterostructures grown x y alloy layers. Imaging of InAs1 xPx/InAs1 ySby superlattices reveals nanometer-scale clustering

Yu, Edward T.

153

Metabolomic and proteomic biomarkers for III-V semiconductors: Chemical-specific porphyrinurias and proteinurias  

SciTech Connect

A pressing need exists to develop and validate molecular biomarkers to assess the early effects of chemical agents, both individually and in mixtures. This is particularly true for new and chemically intensive industries such as the semiconductor industry. Previous studies from this laboratory and others have demonstrated element-specific alterations of the heme biosynthetic pathway for the III-V semiconductors gallium arsenide (GaAs) and indium arsenide (InAs) with attendant increased urinary excretion of specific heme precursors. These data represent an example of a metabolomic biomarker to assess chemical effects early, before clinical disease develops. Previous studies have demonstrated that the intratracheal or subcutaneous administration of GaAs and InAs particles to hamsters produces the induction of the major stress protein gene families in renal proximal tubule cells. This was monitored by 35-S methionine labeling of gene products followed by two-dimensional gel electrophoresis after exposure to InAs particles. The present studies examined whether these effects were associated with the development of compound-specific proteinuria after 10 or 30 days following subcutaneous injection of GaAs or InAs particles in hamsters. The results of these studies demonstrated the development of GaAs- and InAs-specific alterations in renal tubule cell protein expression patterns that varied at 10 and 30 days. At the 30-day point, cells in hamsters that received InAs particles showed marked attenuation of protein expression, suggesting inhibition of the stress protein response. These changes were associated with GaAs and InAs proteinuria patterns as monitored by two-dimensional gel electrophoresis and silver staining. The intensity of the protein excretion patterns increased between the 10- and 30-day points and was most pronounced for animals in the 30-day InAs treatment group. No overt morphologic signs of cell death were seen in renal tubule cells of these animals. Western blot analyses of the urines with antibodies to the 32-, 70-, and 90-kDa stress protein families did not show the presence of these molecules, indicating that these proteins were not excreted in the urine samples. These data suggest that the observed proteinuria patterns were not a result of cell death and that the observed chemical-specific proteinurias were produced before marked cellular toxicity. These findings suggest a hypothesis involving GaAs and InAs interference with stress protein chaperoning of reabsorbed proteins for proteosomic degradation and the probable chaperoning of damaged intracellular proteins from renal proximal tubule cells into the urinary filtrate. Overall, the results of these studies provide further information on the nephrotoxicity of these semiconductor compounds. They also suggest the use of two-dimensional gel electrophoresis with silver staining of urinary protein patterns as a potentially useful proteomic approach to renal damage early in relation to intracellular proteotoxicity in kidney tubule cells.

Fowler, Bruce A. [Program in Toxicology, University of Maryland, Baltimore, MD 21201 (United States)]. E-mail: bxf9@cdc.gov; Conner, Elizabeth A. [Program in Toxicology, University of Maryland, Baltimore, MD 21201 (United States); Yamauchi, Hiroshi [Program in Toxicology, University of Maryland, Baltimore, MD 21201 (United States)

2005-08-07

154

Optimized III-V Multijunction Concentrator Solar Cells on Patterned Si and Ge Substrates: Final Technical Report, 15 September 2004--30 September 2006  

SciTech Connect

Goal is to demo realistic path to III-V multijunction concentrator efficiencies > 40% by substrate-engineering combining compositional grading with patterned epitaxy for small-area cells for high concentration.

Ringel, S. A.

2008-11-01

155

LATTICE THERMAL CONDUCTIVITY OF p-TYPE III-V SEMICONDUCTORS AND p-Si AT LOW TEMPERATURES  

E-print Network

conductivité des semiconduc- teurs de type p légèrement dopés tels que p-GaSb, p-InSb, p-AlSb, p-GaP et p such as p-GaSb, p-InSb, p-AlSb, p-GaP as well as p-Si has been investigated in the low temperature range in the p-type III-V semiconductor compounds such as GaSb [17,18], GaAs [21], InSb [19], AlSb [20] and Ga

Paris-Sud XI, Université de

156

Towards efficient band structure and effective mass calculations for III-V direct band-gap semiconductors  

Microsoft Academic Search

The band structures and effective masses of III-V semiconductors (InP, InAs, InSb, GaAs, and GaSb) are calculated using the GW method, the Heyd, Scuseria, and Ernzerhof hybrid functional, and modified Becke-Johnson combined with the local-density approximation (MBJLDA)---a local potential optimized for the description of the fundamental band gaps [F. Tran and P. Blaha, Phys. Rev. Lett. 102, 226401 (2009)10.1103\\/PhysRevLett.102.226401]. We

Yoon-Suk Kim; Martijn Marsman; Georg Kresse; Fabien Tran; Peter Blaha

2010-01-01

157

InAsSbBi, a direct band-gap, III-V, LWIR material  

NASA Technical Reports Server (NTRS)

In the last several years Dr. Stringfellow's group at the University of Utah has reported success in incorporating over 3 percent Bi in InAs and 1.5 percent in InAsSb using Organometallic Vapor Phase Epitaxy (OMVPE) growth techniques. For InAs the lattice constant increase is linear with a=6.058+0.966x (InAs(1-x)Bi(x)), and a decrease in band gap energy of dEg / dx = -55meV / at a percentage Bi. Extrapolating this to the ternary minimum band gap at InAs(0.35)Sb(0.65), an addition of 1 to 2 percent Bi should drop the band gap to the 0.1 to 0.05eV range (10 to 20 microns). These alloys are direct band gap semiconductors making them candidates for far IR detectors. The current status of the InAsSbBi alloys is that good crystal morphology and x ray diffraction data has been obtained for up to 3.4 percent Bi. The Bi is metastable at these concentrations but the OMVPE grown material has been able to withstand the 400 C growth temperature for several hours without phase separation.

Stringfellow, G. B.; Jones, Colin E.; Frodsham, John

1990-01-01

158

A direct thin-film path towards low-cost large-area III-V photovoltaics  

PubMed Central

III-V photovoltaics (PVs) have demonstrated the highest power conversion efficiencies for both single- and multi-junction cells. However, expensive epitaxial growth substrates, low precursor utilization rates, long growth times, and large equipment investments restrict applications to concentrated and space photovoltaics (PVs). Here, we demonstrate the first vapor-liquid-solid (VLS) growth of high-quality III-V thin-films on metal foils as a promising platform for large-area terrestrial PVs overcoming the above obstacles. We demonstrate 1–3??m thick InP thin-films on Mo foils with ultra-large grain size up to 100??m, which is ~100 times larger than those obtained by conventional growth processes. The films exhibit electron mobilities as high as 500?cm2/V-s and minority carrier lifetimes as long as 2.5?ns. Furthermore, under 1-sun equivalent illumination, photoluminescence efficiency measurements indicate that an open circuit voltage of up to 930?mV can be achieved, only 40?mV lower than measured on a single crystal reference wafer. PMID:23881474

Kapadia, Rehan; Yu, Zhibin; Wang, Hsin-Hua H.; Zheng, Maxwell; Battaglia, Corsin; Hettick, Mark; Kiriya, Daisuke; Takei, Kuniharu; Lobaccaro, Peter; Beeman, Jeffrey W.; Ager, Joel W.; Maboudian, Roya; Chrzan, Daryl C.; Javey, Ali

2013-01-01

159

High-coherence semiconductor lasers based on integral high-Q resonators in hybrid Si/III-V platforms  

PubMed Central

The semiconductor laser (SCL) is the principal light source powering the worldwide optical fiber network. The ever-increasing demand for data is causing the network to migrate to phase-coherent modulation formats, which place strict requirements on the temporal coherence of the light source that no longer can be met by current SCLs. This failure can be traced directly to the canonical laser design, in which photons are both generated and stored in the same, optically lossy, III-V material. This leads to an excessive and large amount of noisy spontaneous emission commingling with the laser mode, thereby degrading its coherence. High losses also decrease the amount of stored optical energy in the laser cavity, magnifying the effect of each individual spontaneous emission event on the phase of the laser field. Here, we propose a new design paradigm for the SCL. The keys to this paradigm are the deliberate removal of stored optical energy from the lossy III-V material by concentrating it in a passive, low-loss material and the incorporation of a very high-Q resonator as an integral (i.e., not externally coupled) part of the laser cavity. We demonstrate an SCL with a spectral linewidth of 18 kHz in the telecom band around 1.55 ?m, achieved using a single-mode silicon resonator with Q of 106. PMID:24516134

Santis, Christos Theodoros; Steger, Scott T.; Vilenchik, Yaakov; Vasilyev, Arseny; Yariv, Amnon

2014-01-01

160

Towards large size substrates for III-V co-integration made by direct wafer bonding on Si  

NASA Astrophysics Data System (ADS)

We report the first demonstration of 200 mm InGaAs-on-insulator (InGaAs-o-I) fabricated by the direct wafer bonding technique with a donor wafer made of III-V heteroepitaxial structure grown on 200 mm silicon wafer. The measured threading dislocation density of the In0.53Ga0.47As (InGaAs) active layer is equal to 3.5 × 109 cm-2, and it does not degrade after the bonding and the layer transfer steps. The surface roughness of the InGaAs layer can be improved by chemical-mechanical-polishing step, reaching values as low as 0.4 nm root-mean-square. The electron Hall mobility in 450 nm thick InGaAs-o-I layer reaches values of up to 6000 cm2/Vs, and working pseudo-MOS transistors are demonstrated with an extracted electron mobility in the range of 2000-3000 cm2/Vs. Finally, the fabrication of an InGaAs-o-I substrate with the active layer as thin as 90 nm is achieved with a Buried Oxide of 50 nm. These results open the way to very large scale production of III-V-o-I advanced substrates for future CMOS technology nodes.

Daix, N.; Uccelli, E.; Czornomaz, L.; Caimi, D.; Rossel, C.; Sousa, M.; Siegwart, H.; Marchiori, C.; Hartmann, J. M.; Shiu, K.-T.; Cheng, C.-W.; Krishnan, M.; Lofaro, M.; Kobayashi, M.; Sadana, D.; Fompeyrine, J.

2014-08-01

161

Preservation of water samples for arsenic(III/V) determinations: An evaluation of the literature and new analytical results  

USGS Publications Warehouse

Published literature on preservation procedures for stabilizing aqueous inorganic As(III/V) redox species contains discrepancies. This study critically evaluates published reports on As redox preservation and explains discrepancies in the literature. Synthetic laboratory preservation experiments and time stability experiments were conducted for natural water samples from several field sites. Any field collection procedure that filters out microorganisms, adds a reagent that prevents dissolved Fe and Mn oxidation and precipitation, and isolates the sample from solar radiation will preserve the As(III/V) ratio. Reagents that prevent Fe and Mn oxidation and precipitation include HCl, H 2SO4, and EDTA, although extremely high concentrations of EDTA are necessary for some water samples high in Fe. Photo-catalyzed Fe(III) reduction causes As(III) oxidation; however, storing the sample in the dark prevents photochemical reactions. Furthermore, the presence of Fe(II) or SO 4 inhibits the oxidation of As(III) by Fe(III) because of complexation reactions and competing reactions with free radicals. Consequently, fast abiotic As(III) oxidation reactions observed in the laboratory are not observed in natural water samples for one or more of the following reasons: (1) the As redox species have already stabilized, (2) most natural waters contain very low dissolved Fe(III) concentrations, (3) the As(III) oxidation caused by Fe(III) photoreduction is inhibited by Fe(II) or SO4.

McCleskey, R.B.; Nordstrom, D.K.; Maest, A.S.

2004-01-01

162

Inter-band optoelectronic properties in quantum dot structure of low band gap III-V semiconductors  

NASA Astrophysics Data System (ADS)

A generalized theory is developed to study inter-band optical absorption coefficient (IOAC) and material gain (MG) in quantum dot structures of narrow gap III-V compound semiconductor considering the wave-vector (k?) dependence of the optical transition matrix element. The band structures of these low band gap semiconducting materials with sufficiently separated split-off valance band are frequently described by the three energy band model of Kane. This has been adopted for analysis of the IOAC and MG taking InAs, InSb, Hg1-xCdxTe, and In1-xGaxAsyP1-y lattice matched to InP, as example of III-V compound semiconductors, having varied split-off energy band compared to their bulk band gap energy. It has been found that magnitude of the IOAC for quantum dots increases with increasing incident photon energy and the lines of absorption are more closely spaced in the three band model of Kane than those with parabolic energy band approximations reflecting the direct the influence of energy band parameters. The results show a significant deviation to the MG spectrum of narrow-gap materials having band nonparabolicity compared to the parabolic band model approximations. The results reflect the important role of valence band split-off energies in these narrow gap semiconductors.

Dey, Anup; Maiti, Biswajit; Chanda Sarkar, Debasree

2014-04-01

163

Predicted energy band gaps of (AIIIBV)1-xXIV2x metastable, substitutional, crystalline alloys  

Microsoft Academic Search

Predictions of the energy band gaps as functions of alloy composition are given for the Greene alloys, which are metastable, crystalline, substitutional alloys of III-V compounds and group-IV elemental materials. All possible combinations of these alloys involving Al, Ga, In, P, As, Sb, Si, Ge, and Sn are considered. The Gamma and L conduction-band minima, relative to the valence-band maxima,

David W. Jenkins; Kathie E. Newman; John D. Dow

1985-01-01

164

Toward the Development of Group III-V Photodetectors and Imaging Arrays  

NASA Technical Reports Server (NTRS)

A collaboration between researchers at NASA Goddard Space Flight Center (GSFC) (Code 718.1) and the Johns Hopkins University Applied Physics Laboratory (APL) on the development of gallium nitride (GaN) based photodetectors has been in existence since July 1994. This collaboration, based on APL undertaking the material growth and GSFC undertaking the device processing, has led to discrete GaN photoconductive detectors with superior characteristics to those of similar devices reported in the literature and, more recently, to the development of state-of-the art 256x256 imaging arrays with the pixels indium bump-bonded to a silicon readout circuit (RIOC). The object of this proposal is to continue the collaboration for the period 1998-2002 by outlining a program of work at the APL on the metalorganic chemical vapor deposition (MOCVD) growth of GaN and related materials for UV detector applications. In particular, emphasis will be placed on the optimization of growth on 2 in diameter substrates, on the growth of In(sub x)Ga(1-x)N and Al(sub x)Ga(1-x)N alloy structures to produce devices with a wider range of tailored cut-off wavelengths, and on the growth of pn-junction structures for photovoltaic devices.

Wickenden, Dennis K.

2003-01-01

165

Dependence of the photoluminescence of annealed III-V semiconductor quantum dots on their shape and dimension  

NASA Astrophysics Data System (ADS)

Interdiffusion in III-V semiconductor quantum dots (QDs) may occur during growth and subsequent device processing steps. The photoluminescence (PL) spectra of InXGa1-XAs/GaAs and InXGa1-XN/GaN QDs change significantly on annealing. The size and shape of a QD dot are important parameters, which govern this change of the PL spectra. In this communication, we have investigated the effects of interdiffusion in realistic InXGa1-XAs/GaAs and InXGa1-XN/GaN QDs with various geometries which are of theoretical and practical interest such as pyramidal, truncated pyramidal, and lens shaped, through quantum mechanical computations.

Kumar, Subindu; Kabi, Sanjib; Biswas, Dipankar

2008-10-01

166

Removal of Arsenic (III, V) from aqueous solution by nanoscale zero-valent iron stabilized with starch and carboxymethyl cellulose.  

PubMed

In this work, synthetic nanoscale zerovalent iron (NZVI) stabilized with two polymers, Starch and Carboxymethyl cellulose (CMC) were examined and compared for their ability in removing As (III) and As (V) from aqueous solutions as the most promising iron nanoparticles form for arsenic removal. Batch operations were conducted with different process parameters such as contact time, nanoparticles concentration, initial arsenic concentration and pH. Results revealed that starch stabilized particles (S-nZVI) presented an outstanding ability to remove both arsenate and arsenite and displayed?~?36.5% greater removal for As (V) and 30% for As (III) in comparison with CMC-stabilized nanoparticles (C-nZVI). However, from the particle stabilization viewpoint, there is a clear trade off to choosing the best stabilized nanoparticles form. Removal efficiency was enhanced with increasing the contact time and iron loading but reduced with increasing initial As (III, V) concentrations and pH. Almost complete removal of arsenic (up to 500 ?g/L) was achieved in just 5 min when the S-nZVI mass concentration was 0.3 g/L and initial solution pH of 7?±?0.1. The maximum removal efficiency of both arsenic species was obtained at pH?=?5?±?0.1 and starched nanoparticles was effective in slightly acidic and natural pH values. The adsorption kinetics fitted well with pseudo-second-order model and the adsorption data obeyed the Langmuir equation with a maximum adsorption capacity of 14 mg/g for arsenic (V), and 12.2 mg/g for arsenic (III). It could be concluded that starch stabilized Fe(0) nanoparticles showed remarkable potential for As (III, V) removal from aqueous solution e.g. contaminated water. PMID:24860660

Mosaferi, Mohammad; Nemati, Sepideh; Khataee, Alireza; Nasseri, Simin; Hashemi, Ahmad Asl

2014-01-01

167

Formation of III-V semiconductor nanotubes on an InP substrate by using the strain-induced self-rolling Method  

NASA Astrophysics Data System (ADS)

Semiconductor nanotube structures have attracted much interest for building blocks of future nanoscale electronic and optical devices. Here, we investigate the structural properties of straininduced self-rolled III-V semiconductor nanotubes. The III-V semiconductor structures for nanotube formation were grown on InP substrates. The bilayer and the quantum-well structures are grown using a metalorganic chemical-vapor deposition system and were fabricated into selfrolled nanotubes. For the self-rolling process, ternary In x Ga1- x As layers were used to produce a lattice-mismatch strain in the nanotube membrane. The experimental observations of the nanotube structures are discussed.

Kim, Myung Sang; Ji, Taeksoo; Hwang, Jeongwoo; Shin, Jae Cheol

2014-08-01

168

Pressure-induced structural change of liquid InAs and the systematics of liquid III-V compounds  

SciTech Connect

To understand the pressure-induced structural changes of liquid III-V compounds systematically, the pressure dependence of l-InAs was investigated using the synchrotron x-ray diffraction and an ab initio molecular-dynamics simulation (AIMD). The x-ray diffraction experiments revealed that the liquid changes its compression behavior from a nearly uniform type to a nonuniform one around 9 GPa. Corresponding to this change, the coordination number (China), which is maintained up to 9 GPa, markedly increases from 6.0 to 7.5. The AIMD simulation revealed that this change is related to the change in the pressure dependence of all three pair correlations. In particular, a marked change is observed in the As-As correlation; in the low-pressure region, the position of the first peak in g{sub AsAs}(r), r{sub AsAs}, increases while maintaining the CN{sub AsAs}, but in the high-pressure region, the r{sub AsAs} stops increasing and the CN{sub AsAs} begins to increase. The AIMD simulation also revealed that each partial structure of l-InAs is similar to that for the pure-element liquid with the same valence electron number. Upon compression, each partial structure approaches the respective one for a heavier element in the same group. These findings suggest that the structures of liquid compounds are locally controlled by the number of the valence electrons in each ion pair and that the change in each partial structure obeys the empirical rule that the high-pressure state resembles the ambient state of a heavier element in the same group. Comparing the pressure-induced structural change of l-InAs to those of other liquid III-V compounds (GaSb and InSb) has revealed that, although the high-pressure behaviors of these three liquids are apparently different, their structural changes are systematically understood by a common structural sequence. This systematics originates from the same effect on each partial structure between increasing the atomic number and the pressurization.

Hattori, T.; Tsuji, K.; Miyata, Y.; Sugahara, T.; Shimojo, F. [Synchrotron Radiation Research Center, Japan Atomic Energy Agency, Kouto, Sayo, Hyogo 679-5148 (Japan); Department of Physics, Keio University, Hiyoshi, Yokohama 223-8522 (Japan); Department of Physics, Kumamoto University, Kumamoto 860-8555 (Japan)

2007-10-01

169

Self-Aligned, Extremely High Frequency III-V Metal-Oxide-Semiconductor Field-Effect Transistors on Rigid and Flexible  

E-print Network

Self-Aligned, Extremely High Frequency III-V Metal-Oxide- Semiconductor Field-Effect Transistors (RF) performance of InAs nanomembrane transistors on both mechanically rigid and flexible substrates high performance InAs metal-oxide-semiconductor field- effect transistors (MOSFETs) with channel

Javey, Ali

170

30 CFR 57.22202 - Main fans (I-A, I-B, I-C, II-A, III, V-A, and V-B mines).  

Code of Federal Regulations, 2011 CFR

...I-B, I-C, II-A, III, V-A, and V-B mines). 57.22202 Section 57.22202 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH...

2011-07-01

171

30 CFR 57.22202 - Main fans (I-A, I-B, I-C, II-A, III, V-A, and V-B mines).  

Code of Federal Regulations, 2010 CFR

...I-B, I-C, II-A, III, V-A, and V-B mines). 57.22202 Section 57.22202 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH...

2010-07-01

172

30 CFR 57.22234 - Actions at 1.0 percent methane (I-A, I-B, III, V-A, and V-B mines).  

Code of Federal Regulations, 2012 CFR

...methane (I-A, I-B, III, V-A, and V-B mines). 57.22234 Section 57.22234 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH...

2012-07-01

173

30 CFR 57.22234 - Actions at 1.0 percent methane (I-A, I-B, III, V-A, and V-B mines).  

Code of Federal Regulations, 2011 CFR

...methane (I-A, I-B, III, V-A, and V-B mines). 57.22234 Section 57.22234 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH...

2011-07-01

174

30 CFR 57.22234 - Actions at 1.0 percent methane (I-A, I-B, III, V-A, and V-B mines).  

Code of Federal Regulations, 2010 CFR

...methane (I-A, I-B, III, V-A, and V-B mines). 57.22234 Section 57.22234 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH...

2010-07-01

175

30 CFR 57.22234 - Actions at 1.0 percent methane (I-A, I-B, III, V-A, and V-B mines).  

Code of Federal Regulations, 2013 CFR

...methane (I-A, I-B, III, V-A, and V-B mines). 57.22234 Section 57.22234 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH...

2013-07-01

176

30 CFR 57.22202 - Main fans (I-A, I-B, I-C, II-A, III, V-A, and V-B mines).  

Code of Federal Regulations, 2013 CFR

...I-B, I-C, II-A, III, V-A, and V-B mines). 57.22202 Section 57.22202 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH...

2013-07-01

177

30 CFR 57.22202 - Main fans (I-A, I-B, I-C, II-A, III, V-A, and V-B mines).  

Code of Federal Regulations, 2012 CFR

...I-B, I-C, II-A, III, V-A, and V-B mines). 57.22202 Section 57.22202 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH...

2012-07-01

178

Channel length scaling limits of III-V channel MOSFETs governed by source-drain direct tunneling  

NASA Astrophysics Data System (ADS)

The difference in the impact of source-drain (SD) direct tunneling in In0.53Ga0.47As and InP metal-oxide-semiconductor field-effect transistors (MOSFETs) was investigated by a quantum Wigner Monte Carlo simulation. It was found that the subthreshold current increase due to SD direct tunneling is more marked in In0.53Ga0.47As MOSFETs owing to their lower effective mass. In addition, the critical channel length at which a drastic increase in subthreshold current occurs owing to SD direct tunneling was found to be about 20 nm for both In0.53Ga0.47As and InP MOSFETs. Since this value is significantly larger than that for Si MOSFETs, SD direct tunneling can be a major obstacle in downscaling III-V MOSFETs into Lch < 20 nm. Hence, to go beyond the end of the roadmap, we will need a selection of materials to suppress SD direct tunneling.

Koba, Shunsuke; Ohmori, Masaki; Maegawa, Y?suke; Tsuchiya, Hideaki; Kamakura, Yoshinari; Mori, Nobuya; Ogawa, Matsuto

2014-04-01

179

Faceting, composition and crystal phase evolution in III-V antimonide nanowire heterostructures revealed by combining microscopy techniques.  

PubMed

III-V antimonide nanowires are among the most interesting semiconductors for transport physics, nanoelectronics and long-wavelength optoelectronic devices due to their optimal material properties. In order to investigate their complex crystal structure evolution, faceting and composition, we report a combined scanning electron microscopy (SEM), transmission electron microscopy (TEM), and scanning tunneling microscopy (STM) study of gold-nucleated ternary InAs/InAs(1-x)Sb(x) nanowire heterostructures grown by molecular beam epitaxy. SEM showed the general morphology and faceting, TEM revealed the internal crystal structure and ternary compositions, while STM was successfully applied to characterize the oxide-free nanowire sidewalls, in terms of nanofaceting morphology, atomic structure and surface composition. The complementary use of these techniques allows for correlation of the morphological and structural properties of the nanowires with the amount of Sb incorporated during growth. The addition of even a minute amount of Sb to InAs changes the crystal structure from perfect wurtzite to perfect zinc blende, via intermediate stacking fault and pseudo-periodic twinning regimes. Moreover, the addition of Sb during the axial growth of InAs/InAs(1-x)Sb(x) heterostructure nanowires causes a significant conformal lateral overgrowth on both segments, leading to the spontaneous formation of a core-shell structure, with an Sb-rich shell. PMID:22322440

Xu, Tao; Dick, Kimberly A; Plissard, Sébastien; Nguyen, Thanh Hai; Makoudi, Younes; Berthe, Maxime; Nys, Jean-Philippe; Wallart, Xavier; Grandidier, Bruno; Caroff, Philippe

2012-03-01

180

Novel Approaches to High-Efficiency III-V Nitride Heterostructure Emitters for Next-Generation Lighting Applications  

SciTech Connect

We report research activities and technical progress on the development of high-efficiency long wavelength ({lambda} {approx} 540nm) green light emitting diodes which covers the first year of the three-year program ''Novel approaches to high-efficiency III-V nitride heterostructure emitters for next-generation lighting applications''. The first year activities were focused on the installation, set-up, and use of advanced equipment for the metalorganic chemical vapor deposition growth of III-nitride films and the characterization of these materials (Task 1) and the design, fabrication, testing of nitride LEDs (Task 4). As a progress highlight, we obtained improved quality of {approx} 2 {micro}m-thick GaN layers (as measured by the full width at half maximum of the asymmetric (102) X-ray diffraction peak of less than 350 arc-s) and higher p-GaN:Mg doping level (free hole carrier higher than 1E18 cm{sup -3}). Also in this year, we have developed the growth of InGaN/GaN active layers for long-wavelength green light emitting diodes, specifically, for emission at {lambda} {approx} 540nm. The effect of the Column III precursor (for Ga) and the post-growth thermal annealing effect were also studied. Our LED device fabrication process was developed and initially optimized, especially for low-resistance ohmic contacts for p-GaN:Mg layers, and blue-green light emitting diode structures were processed and characterized.

Russell D. Dupuis

2004-09-30

181

Proteomic and metabolomic biomarkers for III-V semiconductors: And prospects for application to nano-materials  

SciTech Connect

There has been an increased appreciation over the last 20 years that chemical agents at very low dose levels can produce biological responses in protein expression patterns (proteomic responses) or alterations in sensitive metabolic pathways (metabolomic responses). Marked improvements in analytical methodologies, such as 2-D gel electrophoresis, matrix-assisted laser desorption-time of flight (MALDI-TOF) and surface enhanced laser desorption-time of flight (SELDI-TOF) technologies are capable of identifying specific protein patterns related to exposure to chemicals either alone or as mixtures. The detection and interpretation of early cellular responses to chemical agents have also made great advances through correlative ultrastructural morphometric and biochemical studies. Similarly, advances in analytical technologies such as HPLC, proton NMR, MALDI-TOF, and SELDI-TOF have permitted early detection of changes in a number of essential metabolic pathways following chemical exposures by measurement of alterations in metabolic products from those pathways. Data from these approaches are increasingly regarded as potentially useful biomarkers of chemical exposure and early cellular responses. Validation and establishment of linkages to biological outcomes are needed in order for biomarkers of effect to be established. This short review will cover a number of the above techniques and report data from chemical exposures to two binary III-V semiconductor compounds to illustrate gender differences in proteomic responses. In addition, the use of these methodologies in relation to rapid safety evaluations of nanotechnology products will be discussed. (Supported in part by NIH R01-ES4879)

Fowler, Bruce A. [Program in Toxicology, University of Maryland, Baltimore, Maryland (United States); ATSDR, Atlanta, Georgia (United States)], E-mail: bxf9@cdc.gov; Conner, Elizabeth A. [Program in Toxicology, University of Maryland, Baltimore, Maryland (United States); NCI, Bethesda, Maryland (United States); Yamauchi, Hiroshi [Program in Toxicology, University of Maryland, Baltimore, Maryland (United States); Kitasato University (Japan)

2008-11-15

182

Quasiparticle self-consistent GW theory of III-V nitride semiconductors: Bands, gap bowing, and effective masses  

E-print Network

- pendence of the spectral distribution of luminescence light on carrier concentration.8 When InN is alloyed. The progress in sample preparation techniques has recently led to a revision of the fundamental gap

Svane, Axel Torstein

183

Secondary-ion emission from III-V semiconductive materials under MeV-energy heavy-ion bombardment  

SciTech Connect

Secondary-ion emission from III-V semiconductive chemical compounds (InP, InAs, and InSb) has been experimentally studied at heavy-ion energies from 0.5 to 5.0 MeV, where electronic collision is a dominant process. Various secondary ions such as large cluster ions and atomic ions were observed. Yields of In atomic and cluster ions depend scantly on the incident energy, and those of group-V atomic ions and of cluster ions containing group-V elements can be expressed by an exponential function of S{sub e}{sup -1}, where S{sub e} is the electronic stopping power. This fact shows that the ionization probabilities of the atoms and the clusters whose ionization potentials are higher than the work functions of target materials are increased by transient electronic excitation induced by ion bombardment. The energy distributions of the atomic ions show that the singly charged atomic ions are emitted through the linear collision cascade process even at MeV incident energies, and the multiply charged ions are produced by a projectile-induced simultaneous process of ionization and recoiling of atoms on the target surface. The yield dependences of the cluster ions on the electronic stopping power and on the cluster size are so much different from those for SiO{sub 2}. This fact precludes the multiple-bond-breaking process applied to the insulating material. Structural instabilities caused by high-density electronic excitations, which are known to take place in GaAs irradiated by slow multiply charged ions or lasers, are a possible cause of the cluster-ion emission from the semiconductive compounds at the MeV energy range.

Ninomiya, Satoshi; Imada, Chikage; Nagai, Masafumi; Nakata, Yoshihiko; Imanishi, Nobutsugu [Department of Nuclear Engineering, Kyoto University, Sakyo, Kyoto 606-8501 (Japan)

2004-10-01

184

Soil attenuation of As(III, V) and Se(IV, VI) seepage potential at ash disposal facilities.  

PubMed

Leachate from ash landfills is frequently enriched with As and Se but their off-site movement is not well understood. The attenuation potential of As and Se by soils surrounding selected landfills during leachate seepage was investigated in laboratory column studies using simulated ash leachate. As(III, V) and Se(IV, VI) concentrations as well as pH, flow rate, and a tracer were monitored in influent and effluent for up to 800 pore volumes followed by sequential desorption, extraction, and digestion of column segments. Column breakthrough curves (BTCs) were compared to predictions based on previously measured sorption isotherms. Early As(V) breakthrough and retarded As(III) breakthrough relative to predicted BTCs are indicative of oxidative transformation during seepage. For Se(VI), which exhibits linear sorption and the lowest sorption propensity, measured BTCs were predicted fairly well by equilibrium sorption isotherms, except for the early arrival of Se(IV) in one site soil, which in part, may be due to higher column pH values compared to batch isotherms. Most of the As and Se retained by soils during leaching was found to be strongly sorbed (60-90%) or irreversibly bound (10-40%) with <5% readily desorbable. Redox potential favoring transformation to the more sorptive valence states of As(V) and Se(IV) will invoke additional attenuation beyond equilibrium sorption-based predictions. With the exception of Se(IV) on one site soil, results indicate that attenuation by down-gradient soils of As and Se in ash landfill seepage will often be no less than what is predicted by equilibrium sorption capacity with further attenuation expected due to favorable redox transformation processes, thus mitigating contaminant plumes and associated risks. PMID:24054132

Hyun, Seunghun; Lee, Linda S

2013-11-01

185

Secondary-ion emission from III-V semiconductive materials under MeV-energy heavy-ion bombardment  

NASA Astrophysics Data System (ADS)

Secondary-ion emission from III-V semiconductive chemical compounds (InP, InAs, and InSb) has been experimentally studied at heavy-ion energies from 0.5to5.0MeV , where electronic collision is a dominant process. Various secondary ions such as large cluster ions and atomic ions were observed. Yields of In atomic and cluster ions depend scantly on the incident energy, and those of group-V atomic ions and of cluster ions containing group-V elements can be expressed by an exponential function of Se-1 , where Se is the electronic stopping power. This fact shows that the ionization probabilities of the atoms and the clusters whose ionization potentials are higher than the work functions of target materials are increased by transient electronic excitation induced by ion bombardment. The energy distributions of the atomic ions show that the singly charged atomic ions are emitted through the linear collision cascade process even at MeV incident energies, and the multiply charged ions are produced by a projectile-induced simultaneous process of ionization and recoiling of atoms on the target surface. The yield dependences of the cluster ions on the electronic stopping power and on the cluster size are so much different from those for SiO2 . This fact precludes the multiple-bond-breaking process applied to the insulating material. Structural instabilities caused by high-density electronic excitations, which are known to take place in GaAs irradiated by slow multiply charged ions or lasers, are a possible cause of the cluster-ion emission from the semiconductive compounds at the MeV energy range.

Ninomiya, Satoshi; Imada, Chikage; Nagai, Masafumi; Nakata, Yoshihiko; Imanishi, Nobutsugu

2004-10-01

186

Novel Approaches to High-Efficiency III-V Nitride Heterostructure Emitters for Next-Generation Lighting Applications  

SciTech Connect

We report research activities and technical progress on the development of high-efficiency long wavelength ({lambda} {approx} 540nm) green light emitting diodes which covers whole years of the three-year program 'Novel approaches to high-efficiency III-V nitride heterostructure emitters for next-generation lighting applications'. The research activities were focused on the development of p-type layer that has less/no detrimental thermal annealing effect on as well as excellent structural and electrical properties and the development of green LED active region that has superior luminescence quality for {lambda}{approx}540nm green LEDs. We have also studied (1) the thermal annealing effect on blue and green LED active region during the p-type layer growth; (2) the effect of growth parameters and structural factors for LED active region on electroluminescence properties; (3) the effect of substrates and orientation on electrical and electro-optical properties of green LEDs. As a progress highlight, we obtained green-LED-active-region-friendly In{sub 0.04}Ga{sub 0.96}N:Mg exhibiting low resistivity with higher hole concentration (p=2.0 x 10{sup 18} cm{sup -3} and a low resistivity of 0.5 {omega}-cm) and improved optical quality green LED active region emitting at {approx}540nm by electroluminescence. The LEDs with p-InGaN layer can act as a quantum-confined Stark effect mitigation layer by reducing strain in the QW. We also have achieved (projected) peak IQE of {approx}25% at {lambda}{approx}530 nm and of {approx}13% at {lambda}{approx}545 nm. Visible LEDs on a non-polar substrate using (11-20) {alpha}-plane bulk substrates. The absence of quantum-confined Stark effect was confirmed but further improvement in electrical and optical properties is required.

Russell Dupuis

2007-06-30

187

Novel Approaches to High-Efficiency III-V Nitride Heterostructure Emitters for Next-Generation Lighting Applications  

SciTech Connect

We report research activities and technical progress on the development of high-efficiency long wavelength ({lambda} {approx} 540nm) green light emitting diodes which covers the second year of the three-year program ''Novel approaches to high-efficiency III-V nitride heterostructure emitters for next-generation lighting applications''. The second year activities were focused on the development of p-type layer that has less/no detrimental thermal annealing effect on green LED active region as well as excellent structural and electrical properties and the development of green LED active region that has superior luminescence quality for {lambda} {approx}540nm green LEDs. We have also studied the thermal annealing effect on blue and green LED active region during the p-type layer growth. As a progress highlight, we obtained green-LED-active-region-friendly In{sub 0.04}Ga{sub 0.96}N:Mg exhibiting low resistivity with higher hole concentration (p=2.0 x 10{sup 18} cm{sup -3} and a low resistivity of 0.5 {Omega}-cm) and improved optical quality green LED active region emitting at {lambda} {approx}540nm by electroluminescence. The active region of the green LEDs was found to be much more sensitive to the thermal annealing effect during the p-type layer growth than that of the blue LEDs. We have designed grown, fabricated green LED structures for both 520 nm and 540 nm for the evaluation of second year green LED development.

Russell D. Dupuis

2006-01-01

188

Shape control of III-V semiconductor nanocrystals: synthesis and properties of InAs quantum rods.  

PubMed

A novel approach for synthesis of soluble semiconductor quantum rods using metal nanoparticles to direct and catalyze one-dimensional growth is developed. The method is useful in particular for III-V semiconductors with cubic lattice, where the utilization of surfactant-controlled rod-growth is not easily realized. The growth takes place via the solution-liquid-solid (SLS) mechanism where proper precursors are injected into a coordinating solvent. Centrifugation is used for separation of rod-fractions with different lengths. The reaction is demonstrated for InAs, InP and GaAs. Focusing on InAs rods as a model system, we examined the effects of the type of metal catalyst, and the tuning of reaction conditions with respect to temperature, concentration, catalyst content and reaction time. Within the three types of metal catalysts used--Au, Ag and In, Au was found to provide the best control for achieving rod-growth even though the melting point of bulk gold is significantly higher then the reaction temperature. The structural properties of the rods were characterized by transmission electron microscopy, X-ray diffraction and energy dispersive X-ray spectroscopy. Rods have a cubic lattice and grow mainly along the [111] direction. The relative gold content decreases in shorter rods suggesting Au depletion as a cause for limiting the growth. Room and low temperature absorption and photoluminescence measurements show that the band-gap shifts to the red upon increasing rod length revealing strong quantum confinement along the long axis in InAs rods, providing spectral coverage of the near-IR range relevant for telecommunication applications. Emission intensity also decreases with increased rod-length. These length dependent properties manifest the transition from 0D to 1D quantum confined systems. PMID:14750662

Kan, ShiHai; Aharoni, Assaf; Mokari, Taleb; Banin, Uri

2004-01-01

189

Systematic experimental and theoretical studies of the lattice vibrations of host atoms and substitutional Sn impurities in III–V semiconductors  

Microsoft Academic Search

The lattice vibrations of the two constituent atoms in the III–V semiconductors GaP, GaAs, GaSb, InP, InAs, and InSb have been studied experimentally by neutron diffraction and theoretically by calculations within the framework of various phonon models proposed in the literature for these compounds. The mean-square amplitudes (measured at 295 K) show a general increase with increasing lattice constant and

O. H. Nielsen; F. K. Larsen; S. Damgaard; J. W. Petersen; G. Weyer

1983-01-01

190

Ab-initio study of early stages of III-V epitaxy on Si : direct vs. buffer deposition on vicinal surfaces  

Microsoft Academic Search

III-V materials, such as GaAs or InSb as well as other compound semiconductors with high carrier mobility are considered as potential candidates for a channel material in future CMOS-type devices. The most promising route to incorporate these advanced materials into CMOS is by growing epitaxial thin films on Si, either directly or via a buffer layer. Direct deposition suffers from

A. A. Demkov; Onise Sharia; Hendrik Bentmann

2008-01-01

191

A thermodynamic analysis of native point defect and dopant solubilities in zinc-blende III-V semiconductors  

SciTech Connect

A thermodynamic model is used to analyze available experimental data relevant to point defects in the binary zinc-blende III-V compounds (Ga,In)-(P,As,Sb). The important point defects and their complexes in each of the materials are identified and included in the model. Essentially all of the available experimental data on dopant solubility, crystal density, and lattice parameter of melt and solution grown crystals and epilayers are reproduced by the model. It extends an earlier study [Hurle, J. Appl. Phys. 85, 6957 (1999)] devoted solely to GaAs. Values for the enthalpy and entropy of formation of both native and dopant related point defects are obtained by fitting to experimental data. In undoped material, vacancies, and interstitials on the Group V sublattice dominate in the vicinity of the melting point (MP) in both the phosphides and arsenides, whereas, in the antimonides, vacancies on both sublattices dominate. The calculated concentrations of the native point defects are used to construct the solidus curves of all the compounds. The charged native point defect concentrations at the MP in four of the six materials are significantly higher than their intrinsic carrier concentrations. Thus the usually assumed high temperature 'intrinsic' electroneutrality condition for undoped material (n=p) is not valid for these materials. In GaSb, the Ga{sub Sb} antisite defect appears to be grown-in from the melt. This contrasts with the As{sub Ga} defect in GaAs for which the concentration grown-in at the MP is negligibly small. Compensation of donor-doped material by donor-Group III vacancy complexes is shown to exist in all the compounds except InP where Group VI doped crystals are uncompensated and in InSb where there is a lack of experimental data. The annealing effects in n{sup +} GaAs, including lattice superdilation, which were shown in the earlier paper to be due to Group III vacancy undersaturation during cooling, are found to be present also in GaSb and InAs. Results for native point defects are compared with reported ''first principles'' calculations for GaAs. It is seen that, while there is some accord with experimental findings for low temperature molecular beam epitaxial (MBE) growth, they fail totally to predict the behavior under high temperature growth conditions. The analysis of data on liquid phase epitaxy (LPE) growth of GaAs from Bi solution in the earlier paper has been re-calculated in the light of experimental data that showed that the model used in that paper to represent the Ga-As-Bi phase equilibria was inadequate. An improved model reveals that Ga vacancies exert a greater effect in controlling the extent of the linear range of donor dopant solubility than previously predicted. It has also led to a re-evaluation of the equilibrium EL2 and Ga vacancy concentrations in GaAs during MBE growth under As-rich conditions at low temperatures ({approx}500 K). The amended model predicts that the very high concentrations of EL2 and of Ga vacancies observed experimentally are near equilibrium values. The predicted increase in the equilibrium concentrations of these defects at low temperatures results from coulombic attraction between the two defects. At temperatures somewhat lower than 500 K the rate of increase becomes catastrophic.

Hurle, D. T. J. [Scotscraig House, Storridge, Malvern, Worcestershire WR13 5EY (United Kingdom)

2010-06-15

192

A thermodynamic analysis of native point defect and dopant solubilities in zinc-blende III-V semiconductors  

NASA Astrophysics Data System (ADS)

A thermodynamic model is used to analyze available experimental data relevant to point defects in the binary zinc-blende III-V compounds (Ga,In)-(P,As,Sb). The important point defects and their complexes in each of the materials are identified and included in the model. Essentially all of the available experimental data on dopant solubility, crystal density, and lattice parameter of melt and solution grown crystals and epilayers are reproduced by the model. It extends an earlier study [Hurle, J. Appl. Phys. 85, 6957 (1999)] devoted solely to GaAs. Values for the enthalpy and entropy of formation of both native and dopant related point defects are obtained by fitting to experimental data. In undoped material, vacancies, and interstitials on the Group V sublattice dominate in the vicinity of the melting point (MP) in both the phosphides and arsenides, whereas, in the antimonides, vacancies on both sublattices dominate. The calculated concentrations of the native point defects are used to construct the solidus curves of all the compounds. The charged native point defect concentrations at the MP in four of the six materials are significantly higher than their intrinsic carrier concentrations. Thus the usually assumed high temperature "intrinsic" electroneutrality condition for undoped material (n=p) is not valid for these materials. In GaSb, the GaSb antisite defect appears to be grown-in from the melt. This contrasts with the AsGa defect in GaAs for which the concentration grown-in at the MP is negligibly small. Compensation of donor-doped material by donor-Group III vacancy complexes is shown to exist in all the compounds except InP where Group VI doped crystals are uncompensated and in InSb where there is a lack of experimental data. The annealing effects in n+ GaAs, including lattice superdilation, which were shown in the earlier paper to be due to Group III vacancy undersaturation during cooling, are found to be present also in GaSb and InAs. Results for native point defects are compared with reported "first principles" calculations for GaAs. It is seen that, while there is some accord with experimental findings for low temperature molecular beam epitaxial (MBE) growth, they fail totally to predict the behavior under high temperature growth conditions. The analysis of data on liquid phase epitaxy (LPE) growth of GaAs from Bi solution in the earlier paper has been re-calculated in the light of experimental data that showed that the model used in that paper to represent the Ga-As-Bi phase equilibria was inadequate. An improved model reveals that Ga vacancies exert a greater effect in controlling the extent of the linear range of donor dopant solubility than previously predicted. It has also led to a re-evaluation of the equilibrium EL2 and Ga vacancy concentrations in GaAs during MBE growth under As-rich conditions at low temperatures (˜500 K). The amended model predicts that the very high concentrations of EL2 and of Ga vacancies observed experimentally are near equilibrium values. The predicted increase in the equilibrium concentrations of these defects at low temperatures results from coulombic attraction between the two defects. At temperatures somewhat lower than 500 K the rate of increase becomes catastrophic.

Hurle, D. T. J.

2010-06-01

193

FOUR D'OXYDATION AlOx Cet quipement est ddi l'oxydation thermique humide d'alliages semi-conducteurs III-V riches en  

E-print Network

FOUR D'OXYDATION AlOx Cet équipement est dédié à l'oxydation thermique humide d'alliages semi-conducteurs III-V riches en Al. L'oxydation réalisée sous flux gazeux humide peut être monitorée par un contrôle PRINCIPALES Température d'opération : 300°C Oxydation d'alliages AlGaAs Système

Ingrand, François

194

Detection of soft X-rays with NEA III-V photocathodes. [Negative Electron Affinity X-ray detector for astronomy  

NASA Technical Reports Server (NTRS)

A description is presented of the results of tests on an X-ray photomultiplier containing a negative electron affinity (NEA) photocathode. This device makes it possible to investigate the response of the NEA photocathode to X-rays of various energies. The obtained data provide a basis for the determination of the photoelectron yield and energy resolution of the considered photocathode as a function of energy in the range from 0.8 to 3 keV. The investigation demonstrates the feasibility of using an NEA III-V photocathode for the detection of soft X-rays.

Bardas, D.; Kellogg, E.; Murray, S.; Enck, R., Jr.

1978-01-01

195

Nanostructures produced by phase-separation during growth of (III-V).sub.1-x(IV.sub.2).sub.x alloys  

DOEpatents

Nanostructures (18) and methods for production thereof by phase separation during metal organic vapor-phase epitaxy (MOVPE). An embodiment of one of the methods may comprise providing a growth surface in a reaction chamber and introducing a first mixture of precursor materials into the reaction chamber to form a buffer layer (12) thereon. A second mixture of precursor materials may be provided into the reaction chamber to form an active region (14) on the buffer layer (12), wherein the nanostructure (18) is embedded in a matrix (16) in the active region (14). Additional steps are also disclosed for preparing the nanostructure (18) product for various applications.

Norman, Andrew G. (Evergreen, CO); Olson, Jerry M. (Lakewood, CO)

2007-06-12

196

Selective area growth of III-V nanowires and their heterostructures on silicon in a nanotube template: towards monolithic integration of nano-devices.  

PubMed

We demonstrate a catalyst-free growth technique to directly integrate III-V semiconducting nanowires on silicon using selective area epitaxy within a nanotube template. The nanotube template is selectively filled by homo- as well as heteroepitaxial growth of nanowires with the morphology entirely defined by the template geometry. To demonstrate the method single-crystalline InAs wires on Si as well as InAs-InSb axial heterostructure nanowires are grown within the template. The achieved heterointerface is very sharp and confined within 5-6 atomic planes which constitutes a primary advantage of this technique. Compared to metal-catalyzed or self-catalyzed nanowire growth processes, the nanotube template approach does not suffer from the often observed intermixing of (hetero-) interfaces and non-intentional core-shell formation. The sequential deposition of different material layers within a nanotube template can therefore serve as a general monolithic integration path for III-V based electronic and optoelectronic devices on silicon. PMID:23637047

Kanungo, Pratyush Das; Schmid, Heinz; Björk, Mikael T; Gignac, Lynne M; Breslin, Chris; Bruley, John; Bessire, Cedric D; Riel, Heike

2013-06-01

197

Ferromagnetism of low-dimensional Mn-doped III-V semiconductor structures in the vicinity of the insulator-metal transition  

NASA Astrophysics Data System (ADS)

The structural and transport properties of GaAs/Mn/GaAs/InxGa1-xAs/GaAs quantum wells (x ?0.2) with Mn ?-layer (4-10 at. %), separated from the well by a GaAs spacer, have been studied. The hole mobility in the investigated structures has exceeded the values known for magnetic III-V heterostructures by two orders of magnitude. For structures with the conductivity of the metal type, we have succeeded to observe at low temperatures Shubnikov-de Haas oscillations just confirming the two dimensionality (2D) of the hole energy spectrum. Exactly those 2D holes promote the ferromagnetic ordering of the Mn layer. That has been proven by (i) observing maxima (at 25-40 K) in temperature dependencies of the resistance, which positions agree with calculated values of Curie temperatures (for structures with the indirect interaction of Mn atoms via 2D holes), and (ii) revealing the negative spin-dependent magnetoresistance (NMR) as well as the anomalous Hall effect (AHE), which values are also in good agreement with calculations relating to ferromagnetic 2D III-V systems. As for the structures with the insulator type of the conductivity, their NMR and AHE features evidence the phase separation—the sample fragmentation with the formation of mesoscopic ferromagnetic areas separated by paramagnetic strata of the high tunnel conductivity.

Aronzon, B. A.; Pankov, M. A.; Rylkov, V. V.; Meilikhov, E. Z.; Lagutin, A. S.; Pashaev, E. M.; Chuev, M. A.; Kvardakov, V. V.; Likhachev, I. A.; Vihrova, O. V.; Lashkul, A. V.; Lähderanta, E.; Vedeneev, A. S.; Kervalishvili, P.

2010-01-01

198

Experimental And Theoretical X-Ray Absorption Near-Edge Study Of III-V Compound Semiconductor Materials  

NASA Astrophysics Data System (ADS)

We report experimental and theoretical near-edge x-ray absorption fine structure (NEXAFS) spectra of clean and arsenic-capped gallium arsenide and the pseudo-binary alloy indium-gallium arsenide. Experimental data were obtained using synchrotron-radiation total-photoelectron-yield spectroscopy from the Ga(M2,3), As(M2,3), In(N2,3), and In(M4,5) edges. In addition, both C(K) and 0(K) NEXAFS spectra, and photon-stimulated ion-desorption mass spectra were obtained to assess and monitor the sample cleanliness. The samples studied were grown by molecular-beam epitaxy at China Lake and capped with arsenic for protection during transit to the Stanford Synchrotron-Radiation Laboratory. We have found by monitoring the As edges that heating the samples to 300 or 350 °C completely removes the arsenic cap. Also, we find that after evaporation of the As cap, the NEXAFS spectra are identical for capped and uncapped samples. Theoretical calculations of the arsenic NEXAFS spectra were performed using a full multiple-scattering theory. The inputs to the calculations were ab initio phase shifts, calculated using pseudopotentials and a model geometry. Theoretical calculations of the arsenic NEXAFS spectra of In0.53Ga0.47As crystals are reported also. Here, the calculations are performed by creating many model crystals that have the appropriate stoichiometry and averaging the resulting spectra.

Schwartz, C.; Cole, T. L.; Green, A. K.; Love, P. J.; Rehn, Victor

1988-07-01

199

Optical and electrical properties of III-V nitride wide bandgap semiconductors. Annual report, April 1, 1997--May 31, 1998  

SciTech Connect

The objectives of this project were to investigate the optical and electrical properties of III-nitride wide bandgap semiconductors (GaN, InGaN, AlGaN) and quantum wells, to understand the fundamental optical transitions and impurity properties of these materials, to study the physics components of GaN-based devices, and to provide input for new approaches toward the improvement of materials quality and the optimization of device design. We were the first group to employ transport measurement techniques on the persistent photoconductivity (PPC) state to study the impurity properties of III-nitrides. We were also one of the few research groups m in the world to employ picosecond time-resolved photoluminescence (PL) measurement technique to study mechanisms of optical transitions, LED emission, and lasing m in GaN materials. During this funding period, we have investigated a variety of GaN samples and structures grown by MBE as well as by MOCVD. We have also made a significant progress in MOCVD GaN materials growth. This report briefly discusses the following accomplishments: effects of deep level impurities in the AlGaN/GaN heterostructures; materials characterization of III-nitrides alloys; optical studies of III-nitride epilayers and quantum wells; fabrication and optical studies of III-nitride microdisk arrays; and materials growth by MOCVD.

NONE

1998-06-01

200

The recombination velocity at III-V compound heterojunctions with applications to Al (x) Ga(1-x)As-GaAs(1-y)Sb(y)  

NASA Technical Reports Server (NTRS)

Interface recombination velocity in AlxGa1-xAs-GaAs and A10.85 Ga0.15As-GaAs1-ySby heterojunction systems was studied as a function of lattice mismatch. The results are applied to the design of highly efficient III-V heterojunction solar cells. A horizontal liquid-phase epitaxial growth system was used to prepare p-p-p and p-p-n double heterojunction test samples with specified values of x and y. Samples were grown at each composition, with different GaAs and GaAsSb layer thicknesses. A method was developed to obtain the lattice mismatch and lattice constants in mixed single crystals grown on (100) and (111)B oriented GaAs substrates.

Kim, J. S.

1978-01-01

201

New III-V cell design approaches for very high efficiency. Annual subcontract report, 1 August 1990--31 July 1991  

SciTech Connect

This report describes progress during the first year of a three-year project. The objective of the research is to examine new design approaches for achieving very high conversion efficiencies. The program is divided into two areas. The first centers on exploring new thin-film approaches specifically designed for III-V semiconductors. The second area centers on exploring design approaches for achieving high conversion efficiencies without requiring extremely high quality material. Research activities consisted of an experimental study of minority carrier recombination in n-type, metal-organic chemical vapor deposition (MOCVD)-deposited GaAs, an assessment of the minority carrier lifetimes in n-GaAs grown by molecular beam epitaxy, and developing a high-efficiency cell fabrication process.

Lundstrom, M.S.; Melloch, M.R.; Lush, G.B.; O`Bradovich, G.J.; Young, M.P. [Purdue Univ., Lafayette, IN (United States)

1993-01-01

202

Structural properties of bismuth-bearing semiconductor alloys  

NASA Technical Reports Server (NTRS)

The structural properties of bismuth-bearing III-V semiconductor alloys InPBi, InAsBi, and InSbBi were studied theoretically. Bond energies, bond lengths, and strain coefficients were calculated for pure AlBi, GaBi, and InBi compounds and their alloys, and predictions were made for the mixing enthalpies, miscibility gaps, and critical metastable-to-stable material transition temperatures. Miscibility calculations indicate that InSbBi will be the most miscible, and the InPBi will be the the most difficult to mix. However, calculations of the hardness of the Bi compounds indicate that, once formed, the InPBi alloy will be harder than the other Bi alloys and substantially harder than the currently favored narrow-gap semiconductor HgCdTe.

Berding, M. A.; Sher, A.; Chen, A.-B.; Miller, W. E.

1988-01-01

203

Revetements antireflet-passivation a base de nitrure de silicium PECVD pour cellules solaires triple-jonction III-V/ Ge  

NASA Astrophysics Data System (ADS)

Dans le contexte environnemental actuel, le photovoltaïque bénéficie de l'augmentation des efforts de recherche dans le domaine des énergies renouvelables. Pour réduire le coût de la production d'électricité par conversion directe de l'énergie lumineuse en électricité, le photovoltaïque concentré est intéressant. Le principe est de concentrer une grande quantité d'énergie lumineuse sur des petites surfaces de cellules solaires multi-jonction à haute efficacité. Lors de la fabrication d'une cellule solaire, il est essentiel d'inclure une méthode pour réduire la réflexion de la lumière à la surface du dispositif. Le design d'un revêtement antireflet (ARC) pour cellules solaires multi-jonction présente des défis à cause de la large bande d'absorption et du besoin d'égaliser le courant produit par chaque sous-cellule. Le nitrure de silicium déposé par PECVD en utilisant des conditions standards est largement utilisé dans l'industrie des cellules solaires à base de silicium. Cependant, ce diélectrique présente de l'absorption dans la plage des courtes longueurs d'onde. Nous proposons l'utilisation du nitrure de silicium déposé par PECVD basse fréquence (LFSiN) optimisé pour avoir un haut indice de réfraction et une faible absorption optique pour l'ARC pour cellules solaires triple-jonction III-V/Ge. Ce matériau peut aussi servir de couche de passivation/encapsulation. Les simulations montrent que l'ARC double couche SiO2/LFSiN peut être très efficace pour réduire les pertes par réflexion dans la plage de longueurs d'onde de la sous-cellule limitante autant pour des cellules solaires triple-jonction limitées par la sous-cellule du haut que pour celles limitées par la sous-cellule du milieu. Nous démontrons aussi que la performance de la structure est robuste par rapport aux fluctuations des paramètres des couches PECVD (épaisseurs, indice de réfraction). Mots-clés : Photovoltaïque concentré (CPV), cellules solaires multi-jonction (MJSC), revêtement antireflet (ARC), passivation des semiconducteurs III-V, nitrure de silicium (Si?Ny), PECVD.

Homier, Ram

204

Fabrication of HfO2 patterns by laser interference nanolithography and selective dry etching for III-V CMOS application  

PubMed Central

Nanostructuring of ultrathin HfO2 films deposited on GaAs (001) substrates by high-resolution Lloyd's mirror laser interference nanolithography is described. Pattern transfer to the HfO2 film was carried out by reactive ion beam etching using CF4 and O2 plasmas. A combination of atomic force microscopy, high-resolution scanning electron microscopy, high-resolution transmission electron microscopy, and energy-dispersive X-ray spectroscopy microanalysis was used to characterise the various etching steps of the process and the resulting HfO2/GaAs pattern morphology, structure, and chemical composition. We show that the patterning process can be applied to fabricate uniform arrays of HfO2 mesa stripes with tapered sidewalls and linewidths of 100 nm. The exposed GaAs trenches were found to be residue-free and atomically smooth with a root-mean-square line roughness of 0.18 nm after plasma etching. PACS: Dielectric oxides 77.84.Bw, Nanoscale pattern formation 81.16.Rf, Plasma etching 52.77.Bn, Fabrication of III-V semiconductors 81.05.Ea PMID:21711946

2011-01-01

205

Theoretical modeling and optimization of III-V GaInP/GaAs/Ge monolithic triple-junction solar cells  

NASA Astrophysics Data System (ADS)

We design and optimize monolithic III-V GaInP/GaAs/Ge triple-junction (TJ) solar cells by using a commercial software Silvaco ATLAS simulator to obtain the maximum short-circuit current density J sc . The maximum J sc , which is a current matching value between the GaInP top and GaAs middle subcells, can be determined by varying the base thicknesses of the GaInP top and GaAs middle subcells. From the numerical simulation results, a matched maximum J sc value of 13.92 mA/cm2 is obtained at base thicknesses of 0.57 ?m and 3 ?m for the GaInP top and GaAs middle subcells, respectively, under 1-sun air mass 1.5 global spectrum illumination, leading to a high power conversion efficiency of 30.72%. The open-circuit voltage and the fill factor are 2.55 V and 86.55%, respectively. For the optimized cell structure, the external quantum efficiency and the photogeneration rate distributions are also investigated. To obtain efficient antireflection coatings (ARCs), we perform optical reflectance calculations by using a rigorous coupled-wave analysis method. For this, a silicon oxide/titanium oxide double-layer is used as an ARC on the TJ solar cell.

Leem, Jung Woo; Yu, Jae Su; Kim, Jong Nam; Noh, Sam Kyu

2014-05-01

206

Self-consistent 1-D Schrödinger-Poisson solver for III-V heterostructures accounting for conduction band non-parabolicity  

NASA Astrophysics Data System (ADS)

We present in this paper a novel method to solve self-consistently the Schrödinger and Poisson's equations with non-parabolic conduction bands in III-V heterostructures with one dimensional material and electrostatic potential variation. Our calculation suggests ˜20% more sheet charge density ( N s) may be expected for a representative quantum well FET structure featuring an InGaAs channel cladded with an AlGaSb barrier, compared to predictions from the parabolic band assumption; N s reaches >5 × 10 12 cm -2 at 0.8 V gate overdrive. The increase in sheet density directly results in a higher FET gate capacitance and therefore better transconductance, which stems from the different density of states (DOS) function with the non-parabolic conduction band. Calculation demonstrates that non-parabolicity results in a "tilted staircase" DOS function (as opposed to the classical "flat staircase"). This model was also extended to accommodate satellite valleys, which allows the proper FET gate bias range to be determined in order to avoid overall carrier mobility drop due to L-valley occupation.

Wang, Lingquan; Asbeck, Peter M.; Taur, Yuan

2010-11-01

207

III-V semiconductor Quantum Well systems: Physics of Gallium Arsenide two-dimensional hole systems and engineering of mid-infrared Quantum Cascade lasers  

NASA Astrophysics Data System (ADS)

This dissertation examines two types of III-V semiconductor quantum well systems: two-dimensional holes in GaAs, and mid-infrared Quantum Cascade lasers. GaAs holes have a much reduced hyperfine interaction with the nuclei due to the p-like orbital, resulting in a longer hole spin coherence time comparing to the electron spin coherence time. Therefore, holes' spins are promising candidates for quantum computing qubits, but the effective mass and the Lande g-factor, whose product determines the spin-susceptibility of holes, are not well known. In this thesis, we measure the effective hole mass through analyzing the temperature dependence of Shubnikov-de Haas oscillations in a relatively strong interacting two-dimensional hole systems confined to a 20 nm-wide, (311)A GaAs quantum well. The holes in this system occupy two nearly-degenerate spin subbands whose effective mass we measure to be ˜ 0.2 me. We then apply a sufficiently strong parallel magnetic field to fully depopulate one of the spin subbands, and the spin susceptibility of the two-dimensional hole system is deduced from the depopulation field. We also confine holes in closely spaced bilayer GaAs quantum wells to study the interlayer tunneling spectrum as a function of interlayer bias and in-plane magnetic field, in hope of probing the hole's Fermi contour. Quantum Cascade lasers are one of the major mid-infrared light sources well suited for applications in health and environmental sensing. One of the important factors that affect Quantum Cascade laser performance is the quality of the interfaces between the epitaxial layers. What has long been neglected is that interface roughness causes intersubband scattering, and thus affecting the relation between the lifetimes of the upper and lower laser states, which determines if population inversion is possible. We first utilize strategically added interface roughness in the laser design to engineer the intersubband scattering lifetimes. We further experimentally prove the importance of interface roughness on intersubband scattering by measuring the electron transit time of different quantum cascade lasers and comparing them to the calculated upper laser level lifetimes with and without taking into account interface roughness induced intersubband scattering. A significantly better correlation is found between the experimental results and the calculation when the interface roughness scattering is included. Lastly, we study the effect of growth asymmetry on scattering mechanisms in mid-infrared Quantum Cascade lasers. Due to the dopant migration of around 10 nm along the growth direction of InGaAs/InAlAs Quantum Cascade laser structures, ionized impurity scattering is found to have a non-negligible influence on the lifetime of the upper laser level when the laser is biased in the polarity that electrons flow along the growth direction, in sharp contrast to the situation for the opposite polarity.

Chiu, YenTing

208

Arsenic(III, V) adsorption on a goethite-based adsorbent in the presence of major co-existing ions: Modeling competitive adsorption consistent with spectroscopic and molecular evidence  

NASA Astrophysics Data System (ADS)

Adsorption of the two oxyanions, arsenate (As(V)) and arsenite (As(III)), on a common goethite-based granular porous adsorbent is studied in the presence of major co-existing ions in groundwater (i.e., phosphate, silicic acid, sulfate, carbonate, magnesium, and calcium) and predicted using the extended triple layer model (ETLM), a dipole modified single-site triple layer surface complexation model consistent with spectroscopic and molecular evidence. Surface species of all ions were selected according to the previous ETLM studies and published experimental spectroscopic/theoretical molecular information. The adsorption equilibrium constants for all ions were determined using adsorption data obtained in single-solute systems. The adsorption equilibrium constants referenced to the site-occupancy standard state (indicated by K?) were compared with those for goethite in the literature if available. The values of these constants for the goethite-based adsorbent are found to be close to the values for goethite previously studied. These "constrained" adsorption equilibrium constants determined in single-solute systems were used in the ETLM to predict the competitive interactions of As(III, V) with the co-existing ions in binary-solute systems. The ETLM is capable of predicting As(III, V) adsorption in the presence of oxyanions (phosphate, silicic acid, sulfate, and carbonate). This study presents the first successful and systematic prediction of the competitive interactions of As(III, V) with these oxyanions using the ETLM. The ETLM prediction of surface (and aqueous) speciation also provides insights into the distinct adsorption behavior of As(III, V) in the presence of the oxyanions. Magnesium and calcium significantly enhanced As(V) adsorption at higher pH values, while they had little effect on As(III) adsorption. The enhanced adsorption of As(V), however, could not be predicted by the ETLM using the surface species proposed in previous ETLM studies. Further studies are necessary to identify ternary complexes, especially at high pH. Adsorption isotherms of As(V), a dominant form of arsenic in adsorptive water treatment systems, in the presence of the co-existing ions under relevant conditions of water treatment systems are also obtained and predicted by the ETLM to study and compare the effect of the co-existing ions on As(V) removal.

Kanematsu, Masakazu; Young, Thomas M.; Fukushi, Keisuke; Green, Peter G.; Darby, Jeannie L.

2013-04-01

209

Origin of the Tunnel Anisotropic Magnetoresistance in Ga1-xMnxAs/ZnSe/Ga1-xMnxAs Magnetic Tunnel Junctions of II-VI/III-V Heterostructures  

NASA Astrophysics Data System (ADS)

We investigated spin-dependent transport in magnetic tunnel junctions made of III-V Ga1-xMnxAs electrodes and II-VI ZnSe tunnel barriers. The high tunnel magnetoresistance (TMR) ratio up to 100% we observed indicates high spin polarization at the barrier/electrodes interfaces. We found anisotropic tunneling conductance having a magnitude of 10% with respect to the direction of magnetization to linearly depend on the magnetic anisotropy energy of Ga1-xMnxAs. This proves that the spin-orbit interactions in the valence band of Ga1-xMnxAs are responsible for the tunnel anisotropic magnetoresistance (TAMR) effect.

Saito, H.; Yuasa, S.; Ando, K.

2005-08-01

210

Origin of the tunnel anisotropic magnetoresistance in Ga(1-x)Mn(x)As/ZnSe/Ga(1-x)Mn(x)As magnetic tunnel junctions of II-VI/III-V heterostructures.  

PubMed

We investigated spin-dependent transport in magnetic tunnel junctions made of III-V Ga(1-x)Mn(x)As electrodes and II-VI ZnSe tunnel barriers. The high tunnel magnetoresistance (TMR) ratio up to 100% we observed indicates high spin polarization at the barrier/electrodes interfaces. We found anisotropic tunneling conductance having a magnitude of 10% with respect to the direction of magnetization to linearly depend on the magnetic anisotropy energy of Ga(1-x)Mn(x)As. This proves that the spin-orbit interactions in the valence band of Ga(1-x)M(x)As are responsible for the tunnel anisotropic magnetoresistance (TAMR) effect. PMID:16196884

Saito, H; Yuasa, S; Ando, K

2005-08-19

211

Structural properties of bismuth-bearing semiconductor alloys  

NASA Technical Reports Server (NTRS)

The structural properties of bismuth-bearing III-V semiconductor alloys are addressed. Because the Bi compounds are not known to form zincblende structures, only the anion-substituted alloys InPBi, InAsBi, and InSbBi are considered candidates as narrow-gap semiconductors. Miscibility calculations indicate that InSbBi will be the most miscible, and InPBi, with the large lattice mismatch of the constituents, will be the most difficult to mix. Calculations of the hardness of the Bi compounds indicate that, once formed, the InPBi alloy will be harder than the other Bi alloys, and substantially harder than the currently favored narrow-gap semiconductor HgCdTe. Thus, although InSbBi may be an easier material to prepare, InPBi promises to be a harder material. Growth of the Bi compounds will require high effective growth temperatures, probably attainable only through the use of nonequilibrium energy-assisted epitaxial growth techniques.

Berding, M. A.; Sher, A.; Chen, A. B.

1986-01-01

212

Mechanical Alloying  

Microsoft Academic Search

A new technique of combining metals has been developed which overcomes many of the limitations of conventional alloying. Ball mills that generate higher energies than conventional ball mills are used to tumble a mixture of powders, such as WC and Co, in order to form a composite. Ni-base alloys can be dispersion-hardened in this way with an oxide such as

J. S. Benjamin

1976-01-01

213

Multiple doping of silicon-germanium alloys for thermoelectric applications  

NASA Technical Reports Server (NTRS)

It is shown that heavy doping of n-type Si/Ge alloys with phosphorus and arsenic (V-V doping interaction) by diffusion leads to a significant enhancement of their carrier concentration and possible improvement of the thermoelectric figure of merit. High carrier concentrations were achieved by arsenic doping alone, but for a same doping level higher carrier mobilities and lower resistivities are obtained through phosphorus doping. By combining the two dopants with the proper diffusion treatments, it was possible to optimize the different properties, obtaining high carrier concentration, good carrier mobility and low electrical resistivity. Similar experiments, using the III-V doping interaction, were conducted on boron-doped p-type samples and showed the possibility of overcompensating the samples by diffusing arsenic, in order to get n-type behavior.

Fleurial, Jean-Pierre; Vining, Cronin B.; Borshchevsky, Alex

1989-01-01

214

'Candidatus Phytoplasma sudamericanum', a novel taxon, and strain PassWB-Br4, a new subgroup 16SrIII-V phytoplasma, from diseased passion fruit (Passiflora edulis f. flavicarpa Deg.).  

PubMed

Symptoms of abnormal proliferation of shoots resulting in formation of witches'-broom growths were observed on diseased plants of passion fruit (Passiflora edulis f. flavicarpa Deg.) in Brazil. RFLP analysis of 16S rRNA gene sequences amplified in PCRs containing template DNAs extracted from diseased plants collected in Bonito (Pernambuco) and Viçosa (Minas Gerais) Brazil, indicated that such symptoms were associated with infections by two mutually distinct phytoplasmas. One phytoplasma, PassWB-Br4 from Bonito, represents a new subgroup, 16SrIII-V, in the X-disease phytoplasma group ('Candidatus Phytoplasma pruni'-related strains). The second phytoplasma, PassWB-Br3 from Viçosa, represents a previously undescribed subgroup in group 16SrVI. Phylogenetic analyses of 16S rRNA gene sequences were consistent with the hypothesis that strain PassWB-Br3 is distinct from previously described 'Ca. Phytoplasma' species. Nucleotide sequence alignments revealed that strain PassWB-Br3 shared less than 97.5 % 16S rRNA gene sequence similarity with previously described 'Ca. Phytoplasma' species. The unique properties of its DNA, in addition to natural host and geographical occurrence, support the recognition of strain PassWB-Br3 as a representative of a novel taxon, 'Candidatus Phytoplasma sudamericanum'. PMID:21669919

Davis, Robert E; Zhao, Yan; Dally, Ellen L; Jomantiene, Rasa; Lee, Ing-Ming; Wei, Wei; Kitajima, Elliot W

2012-04-01

215

Surface phonons of III-V semiconductors  

E-print Network

-resolution electron energy loss spectroscopy measurements. We predict an additional acoustic branch along [ ]. For InP, we predict a prominent optical branch, in the gap between bulk acoustic and optical modes. The (110) surfaces of Ill-V semiconductors...

Das, Pradip Kumar

2012-06-07

216

The physics of III-V nitrides  

Microsoft Academic Search

The evolution of semiconductor physics is driven by the increasing sophistication of the art of crystal growing and fabrication techniques. From Ge at the birth of the transistor, possibly the purest material ever grown, through Si, the work-horse of the crystal revolution, to the III-Vs, whose optical properties opened up a second front, namely, optoelectronics. Crystal growth with monolayer control

B K Ridley

2009-01-01

217

Towards III-V solar cells on Si: Improvement in the crystalline quality of Ge-on-Si virtual substrates through low porosity porous silicon buffer layer and annealing  

NASA Astrophysics Data System (ADS)

A comparison between the crystalline quality of Ge grown on bulk Si and on a low porosity porous Si (pSi) buffer layer using low energy plasma enhanced chemical vapor deposition is reported. Omega/2Theta coupled scans around the Ge and Si (004) diffraction peaks show a reduction of the Ge full-width at half maximum (FWHM) of 22.4% in presence of the pSi buffer layer, indicating it is effective in improving the epilayer crystalline quality. At the same time atomic force microscopy analysis shows an increase in root means square roughness for Ge grown on pSi from 38.5 nm to 48.0 nm, as a consequence of the larger surface roughness of pSi compared to bulk Si. The effect of 20 minutes vacuum annealing at 580°C is also investigated. The annealing leads to a FWHM reduction of 23% for Ge grown on Si and of 36.5% for Ge on pSi, resulting in a FWHM of 101 arcsec in the latter case. At the same time, the RMS roughness is reduced of 8.8% and of 46.5% for Ge grown on bulk Si and on pSi, respectively. The biggest improvement in the crystalline quality of Ge grown on pSi with respect to Ge grown on bulk Si observed after annealing is a consequence of the simultaneous reorganization of the Ge epilayer and the buffer layer driven by energy minimization. A low porosity buffer layer can thus be used for the growth of low defect density Ge on Si virtual substrates for the successive integration of III-V multijunction solar cells on Si. The suggested approach is simple and fast -thus allowing for high throughput-, moreover is cost effective and fully compatible with subsequent wafer processing. Finally it does not introduce new chemicals in the solar cell fabrication process and can be scaled to large area silicon wafers.

Calabrese, Gabriele; Baricordi, Stefano; Bernardoni, Paolo; Fin, Samuele; Guidi, Vincenzo; Vincenzi, Donato

2014-09-01

218

4,000-atom LDA supercell calculations of wavefunction localization in III-V nitrides GaAsN, InAsN, GaPN, InPN  

NASA Astrophysics Data System (ADS)

Whereas addition of N to III-Vs, e.g. GaAs, creates localized electron states, addition of P to GaAs or Ga to InAs does not. What controls this behavior? We suggest that impurity X will have a localized electron state when substituted in semiconductor AY if the AY/AX conduction band offsets is large enough, and the AX electron effective mass heavy enough. We test this "particle in a box" rule for nitrogen in GaAs, InAs, GaP, InP and for Ga in InAs and P in GaAs, examining both hole and electron localization. To diagnose the existence of localized states in these materials, particularly Indium compounds where experimental data is lacking, we have performed 4096 atom LDA calculations using a newly developed algorithm combining "charge patching" with the "folded spectrum method". This method enables us to obtain selected LDA eigenvalues around the band gap of the 4096 atom system, without solving for all of the occupied states. We find localized electron states for N in these III-V systems, but in contrast, for Ga in InAs, no such localized states exist, despite the large GaAs/InAs conduction band offset. This is primarily because the InAs electron mass is very light. For P in GaAs, the band offsets, band gaps, and masses are such that P-induced electron state is only weakly resonant high in the conduction band. We find that this "particle in a box" rule may be used to predict both electron and hole localization in various isovalent systems.

Kent, P. R. C.; Zunger, Alex; Lin-Wang, Wang

2002-03-01

219

Amorphous metal alloys produced by mechanical alloying  

SciTech Connect

Mechanical alloying is a powder metallurgy method used in commercial production of high temperature superalloys. Under specific conditions, mechanical alloying allows the synthesis of amorphous metal alloys from mixtures of pure metal powders or from the powders of intermetallic compounds. Because the amorphizing transformation during mechanical alloying is a solid state reaction, most of the difficulties related to the amorphization by rapid solidification of melts can be avoided. Mechanical alloying allows the synthesis of amorphous alloys from metals with high melting temperatures and the resulting alloys have interesting properties such as high hardness and high crystallization temperatures. We used mechanical alloying for the synthesis of amorphous alloys in the binary alloy systems Nl-Sn, Nb-Si and Al-Hf. The amorphous alloy powders were characterized by x-ray diffraction, differential scanning calorimetry, scanning and transmission electron microscopy and hardness measurements. Produced alloys were compacted by hot pressing and the obtained compacts were characterized by x-ray diffraction, density and hardness measurements and by optical and scanning electron microscopy. The results of the amorphization and compaction studies are presented and discussed together with the characteristics of the mechanical alloying process. 15 refs., 5 figs.

Tiainen, T.J.; Schwarz, R.B.

1989-01-01

220

Composition Dependence of the Band Gap and Doping in Cu2O-Based Alloys as Predicted by an Extension of the Dilute-Defect Model  

NASA Astrophysics Data System (ADS)

Tuning the optoelectronic properties through alloying is essential for semiconductor technology. Currently, mostly isovalent and isostructural alloys are used (e.g., groups IV and III-V), but a vast and unexplored space of novel functional materials is conceivable when considering more complex alloys by mixing aliovalent and heterostructural constituents. The real challenge lies in the quantitative property prediction for such complex alloys to guide their experimental exploration. We develop an approach to predict compositional dependence of both band-structure and electrical properties from ab initio calculations by extending the conventional dilute-defect model to higher (alloy) concentrations. Considering alloying of aliovalent (Mg, Zn, Cd) cations and isovalent anions (S, Se) into Cu2O, we predict tunability of band-gap energies and doping levels over a wide range, including the type conversion from p to n type. Initial synthesis and characterization of Zn-and Se-substituted Cu2O support the defect model, suggesting these alloys as promising novel oxide-semiconductor materials.

Stevanovi?, Vladan; Zakutayev, Andriy; Lany, Stephan

2014-10-01

221

Semiconductor structures having electrically insulating and conducting portions formed from an AlSb-alloy layer  

DOEpatents

The semiconductor structure comprises a plurality of semiconductor layers formed on a substrate including at least one layer of a III-V compound semiconductor alloy comprising aluminum (Al) and antimony (Sb), with at least a part of the AlSb-alloy layer being chemically converted by an oxidation process to form superposed electrically insulating and electrically conducting portions. The electrically insulating portion formed from the AlSb-alloy layer comprises an oxide of aluminum (e.g., Al{sub 2}O{sub 3}), while the electrically conducting portion comprises Sb. A lateral oxidation process allows formation of the superposed insulating and conducting portions below monocrystalline semiconductor layers for forming many different types of semiconductor structures having particular utility for optoelectronic devices such as light-emitting diodes, edge-emitting lasers, vertical-cavity surface-emitting lasers, photodetectors and optical modulators (waveguide and surface normal), and for electronic devices such as heterojunction bipolar transistors, field-effect transistors and quantum-effect devices. The invention is expected to be particularly useful for forming light-emitting devices for use in the 1.3--1.6 {mu}m wavelength range, with the AlSb-alloy layer acting to define an active region of the device and to effectively channel an electrical current therein for efficient light generation. 10 figs.

Spahn, O.B.; Lear, K.L.

1998-03-10

222

FOREWORD: The physics of III-V nitrides The physics of III-V nitrides  

Microsoft Academic Search

The evolution of semiconductor physics is driven by the increasing sophistication of the art of crystal growing and fabrication techniques. From Ge at the birth of the transistor, possibly the purest material ever grown, through Si, the work-horse of the crystal revolution, to the III-Vs, whose optical properties opened up a second front, namely, optoelectronics. Crystal growth with monolayer control

B. K. Ridley

2009-01-01

223

III V CMOS:III-V CMOS: A sub-10 nm Electronics Technology?gy  

E-print Network

Microsystems Technology Laboratories, MIT AVS 57th International Symposium & Exhibition October 17-22, 2010 microprocessors Intel microprocessors 3 #12;Recent trend in CMOS scaling · Si CMOS has entered era of "power nm)- InAs core (tInAs = 5 nm) - InGaAs cladding - n Hall = 13,200 cm2/V-secn,Hall 13,200 cm /V sec

del Alamo, Jesús A.

224

Anodizing of aluminium alloys  

Microsoft Academic Search

Anodizing is used widely in the surface treatment of aluminium alloys for aerospace applications. Considers recent advances in understanding of the influences of alloying elements in anodizing of aluminium alloys and, in particular, their applicability to second phase particles during anodizing of commercial alloys. Through more precise knowledge of the response of second phase materials to anodic polarization, improved anodizing

G. E. Thompson; H. Habazaki; K. Shimizu; M. Sakairi; P. Skeldon; X. Zhou; G. C. Wood

1999-01-01

225

Austenitic stainless steel alloy  

Microsoft Academic Search

This patent describes a stainless steel alloy composition for service exposed to irradiation, having resistance to irradiation promoted stress corrosion cracking and reduced long term irradiation induced radioactivity. The alloy consisting of a low carbon content austenitic stainless steel alloy composition comprising about 18 to 20 percent weight of chromium, about 9 to 11 percent weight of nickel, about 1.5

D. J. Coates; G. M. Gordon; A. J. Jacobs; D. W. Sandusky

1989-01-01

226

Alloys for aerospace  

Microsoft Academic Search

Aerospace industries require special allows with many properties tailored to meet specific needs. Prerequisites include clean melting techniques to maintain low impurity levels, tight control of alloy chemistry, and the analytical capability to characterize the product. Teledyne Wah Chang (TWC) produces specially refractory metals, including zirconium, hafnium, titanium, niobium and vanadium, which are essential components of many aerospace alloys. Alloys

S. Tuominen; C. Wojcik

1995-01-01

227

Creep Resistant Zinc Alloy  

SciTech Connect

This report covers the development of Hot Chamber Die Castable Zinc Alloys with High Creep Strengths. This project commenced in 2000, with the primary objective of developing a hot chamber zinc die-casting alloy, capable of satisfactory service at 140 C. The core objectives of the development program were to: (1) fill in missing alloy data areas and develop a more complete empirical model of the influence of alloy composition on creep strength and other selected properties, and (2) based on the results from this model, examine promising alloy composition areas, for further development and for meeting the property combination targets, with the view to designing an optimized alloy composition. The target properties identified by ILZRO for an improved creep resistant zinc die-casting alloy were identified as follows: (1) temperature capability of 1470 C; (2) creep stress of 31 MPa (4500 psi); (3) exposure time of 1000 hours; and (4) maximum creep elongation under these conditions of 1%. The project was broadly divided into three tasks: (1) Task 1--General and Modeling, covering Experimental design of a first batch of alloys, alloy preparation and characterization. (2) Task 2--Refinement and Optimization, covering Experimental design of a second batch of alloys. (3) Task 3--Creep Testing and Technology transfer, covering the finalization of testing and the transfer of technology to the Zinc industry should have at least one improved alloy result from this work.

Frank E. Goodwin

2002-12-31

228

Recovery of uranium alloy  

SciTech Connect

A method is described of recovery of uranium alloy from a mixture of uranium alloy with magnesium fluoride comprising: (a) pretreating uranium fluoride with magnesium at 400/sup 0/-1250/sup 0/C. to form a pretreated mixture of uranium and magnesium fluoride, (b) introducing the pretreated mixture into a molten-salt bath floating on a molten-uranium-alloy trap, (c) allowing the bath to transfer heat to the pretreated mixture to cause the magnesium fluoride to dissolve into the molten-salt bath and the uranium alloy to be molten, (d) allowing molten uranium alloy from the pretreated mixture in the bath to separate from the bath into the trap, (e) discharging separated molten-uranium alloy from the trap, and (f) discharging non-alloy components of the pretreated mixture along with excess molten salt from the bath.

Elliott, G.R.B.

1987-01-13

229

CD2Alloy: Class Diagrams Analysis Using Alloy Revisited  

E-print Network

CD2Alloy: Class Diagrams Analysis Using Alloy Revisited Shahar Maoz , Jan Oliver Ringert present CD2Alloy, a novel, powerful translation of UML class diagrams (CDs) to Alloy. Unlike existingAlloy uses a deeper embedding strategy. Rather than mapping each CD construct to a semantically

Maoz, Shahar

230

Research on mechanically alloyed aluminum alloy products for aerospace applications  

Microsoft Academic Search

Mechanically alloyed (MA) aluminum alloys represent an advanced aluminum powder metallurgy technology. Chemically homogeneous alloy powders containing a fine distribution of oxide and carbide dispersoids are manufactured by mechanical alloying, an INCO propriety process involving high energy milling of elemental powders. This process allows a desirable chemistry\\/microstructure\\/property combination to be engineered into the alloy. Consolidation by canless vacuum hot pressing

R. D. Schelleng; P. S. Gilman; A. D. Jatkar; S. J. Donachie

2008-01-01

231

Weldability of High Alloys  

SciTech Connect

The purpose of this study was to investigate the effect of silicon and iron on the weldability of HAYNES HR-160{reg_sign} alloy. HR-I60 alloy is a solid solution strengthened Ni-Co-Cr-Si alloy. The alloy is designed to resist corrosion in sulfidizing and other aggressive high temperature environments. Silicon is added ({approx}2.75%) to promote the formation of a protective oxide scale in environments with low oxygen activity. HR-160 alloy has found applications in waste incinerators, calciners, pulp and paper recovery boilers, coal gasification systems, and fluidized bed combustion systems. HR-160 alloy has been successfully used in a wide range of welded applications. However, the alloy can be susceptible to solidification cracking under conditions of severe restraint. A previous study by DuPont, et al. [1] showed that silicon promoted solidification cracking in the commercial alloy. In earlier work conducted at Haynes, and also from published work by DuPont et al., it was recognized that silicon segregates to the terminal liquid, creating low melting point liquid films on solidification grain boundaries. Solidification cracking has been encountered when using the alloy as a weld overlay on steel, and when joining HR-160 plate in a thickness greater than19 millimeters (0.75 inches) with matching filler metal. The effect of silicon on the weldability of HR-160 alloy has been well documented, but the effect of iron is not well understood. Prior experience at Haynes has indicated that iron may be detrimental to the solidification cracking resistance of the alloy. Iron does not segregate to the terminal solidification product in nickel-base alloys, as does silicon [2], but iron may have an indirect or interactive influence on weldability. A set of alloys covering a range of silicon and iron contents was prepared and characterized to better understand the welding metallurgy of HR-160 alloy.

Maroef, I

2003-01-22

232

Alloy 10: A 1300F Disk Alloy  

NASA Technical Reports Server (NTRS)

Gas turbine engines for future subsonic transports will probably have higher pressure ratios which will require nickel-base superalloy disks with 13000 to 1400 F temperature capability. Several advanced disk alloys are being developed to fill this need. One of these, Allied Signal's Alloy 10, is a promising candidate for gas turbine engines to be used on smaller, regional aircraft. For this application, compressor/turbine disks must withstand temperatures of 1300 F for several hundred hours over the life of the engine. In this paper, three key properties of Alloy 10--tensile, 0.2% creep, and fatigue crack growth--will be assessed at 1300 F.

Gayda, John

2000-01-01

233

Catalyst Alloys Processing  

NASA Astrophysics Data System (ADS)

Catalysts are one of the key materials used for diamond formation at high pressures. Several such catalyst products have been developed and applied in China and around the world. The catalyst alloy most widely used in China is Ni70Mn25Co5 developed at Changsha Research Institute of Mining and Metallurgy. In this article, detailed techniques for manufacturing such a typical catalyst alloy will be reviewed. The characteristics of the alloy will be described. Detailed processing of the alloy will be presented, including remelting and casting, hot rolling, annealing, surface treatment, cold rolling, blanking, finishing, packaging, and waste treatment. An example use of the catalyst alloy will also be given. Industrial experience shows that for the catalyst alloy products, a vacuum induction remelt furnace can be used for remelting, a metal mold can be used for casting, hot and cold rolling can be used for forming, and acid pickling can be used for metal surface cleaning.

Tan, Xincai

2014-10-01

234

Low activation ferritic alloys  

DOEpatents

Low activation ferritic alloys, specifically bainitic and martensitic stainless steels, are described for use in the production of structural components for nuclear fusion reactors. They are designed specifically to achieve low activation characteristics suitable for efficient waste disposal. The alloys essentially exclude molybdenum, nickel, nitrogen and niobium. Strength is achieved by substituting vanadium, tungsten, and/or tantalum in place of the usual molybdenum content in such alloys.

Gelles, David S. (West Richland, WA); Ghoniem, Nasr M. (Granada Hills, CA); Powell, Roger W. (Pasco, WA)

1986-01-01

235

Low activation ferritic alloys  

DOEpatents

Low activation ferritic alloys, specifically bainitic and martensitic stainless steels, are described for use in the production of structural components for nuclear fusion reactors. They are designed specifically to achieve low activation characteristics suitable for efficient waste disposal. The alloys essentially exclude molybdenum, nickel, nitrogen and niobium. Strength is achieved by substituting vanadium, tungsten, and/or tantalum in place of the usual molybdenum content in such alloys.

Gelles, D.S.; Ghoniem, N.M.; Powell, R.W.

1985-02-07

236

Translating Z to Alloy  

Microsoft Academic Search

\\u000a Few tools are available to help with the difficult task of validating that a Z specification captures its intended meaning.\\u000a One tool that has been proven to be useful for validating specifications is the Alloy Analyzer, an interactive tool for checking\\u000a and visualising Alloy models. However, Z specifications need to be translated to Alloy notation to make use of the

Petra Malik; Lindsay Groves; Clare Lenihan

2010-01-01

237

Amorphous metal alloy  

DOEpatents

Amorphous metal alloys of the iron-chromium and nickel-chromium type have excellent corrosion resistance and high temperature stability and are suitable for use as a protective coating on less corrosion resistant substrates. The alloys are stabilized in the amorphous state by one or more elements of titanium, zirconium, hafnium, niobium, tantalum, molybdenum, and tungsten. The alloy is preferably prepared by sputter deposition.

Wang, R.; Merz, M.D.

1980-04-09

238

Advanced aerospace Al alloys  

Microsoft Academic Search

SiC particulate or whisker-reinforced aluminum alloys are very attractive for applications requiring high stiffness coupled with a comparatively light weight. The dispersion strengthened Al alloys produced through the rapid solidification processing\\/powder metallurgy route demonstrate superior elevated temperature strength and microstructural stability, extending the useful service temperature of Al alloys to 350 C. However, low ductility and poor fracture toughness levels

K. S. Ravichandran; E. S. Dwarakadasa

1987-01-01

239

Integration of GaAsP alloys on SiGe virtual substrates for Si-based dual-junction solar cells  

E-print Network

Integration of III-V compound semiconductors with silicon is an area that has generated a lot of interest because III-V materials and Si are best suited for different types of devices. Monolithic integration enables the ...

Sharma, Prithu

2013-01-01

240

Ductile transplutonium metal alloys  

DOEpatents

Alloys of Ce with transplutonium metals such as Am, Cm, Bk and Cf have properties making them highly suitable as souces of the transplutonium element, e.g., for use in radiation detector technology or as radiation sources. The alloys are ductile, homogeneous, easy to prepare and have a fairly high density.

Conner, W.V.

1981-10-09

241

Neutron Absorbing Alloys  

DOEpatents

The present invention is drawn to new classes of advanced neutron absorbing structural materials for use in spent nuclear fuel applications requiring structural strength, weldability, and long term corrosion resistance. Particularly, an austenitic stainless steel alloy containing gadolinium and less than 5% of a ferrite content is disclosed. Additionally, a nickel-based alloy containing gadolinium and greater than 50% nickel is also disclosed.

Mizia, Ronald E. (Idaho Falls, ID); Shaber, Eric L. (Idaho Falls, ID); DuPont, John N. (Whitehall, PA); Robino, Charles V. (Albuquerque, NM); Williams, David B. (Bethlehem, PA)

2004-05-04

242

Surface composition of alloys  

NASA Astrophysics Data System (ADS)

In equilibrium, the composition of the surface of an alloy will, in general, differ from that of the bulk. The broken-bond model is applicable to alloys with atoms of virtually equal size. If the heat of alloy formation is zero, the component of lower heat of atomization is found enriched in the surface. If both partners have equal heats of sublimination, the surface of a diluted alloy is enriched with the minority component. Size effects can enhance or weaken the electronic effects. In general, lattice strain can be relaxed by precipitating atoms of deviating size on the surface. Two-phase alloys are described by the "cherry model", i.e. one alloy phase, the "kernel" is surrounded by another alloy, the "flesh", and the surface of the outer phase, the "skin" displays a deviating surface composition as in monophasic alloys. In the presence of molecules capable of forming chemical bonds with individual metal atoms, "chemisorption induced surface segregation" can be observed at low temperatures, i.e. the surface becomes enriched with the metal forming the stronger chemisorption bonds.

Sachtler, W. M. H.

1984-11-01

243

Aluminum battery alloys  

DOEpatents

Aluminum alloys suitable for use as anode structures in electrochemical cells are disclosed. These alloys include iron levels higher than previously felt possible, due to the presence of controlled amounts of manganese, with possible additions of magnesium and controlled amounts of gallium.

Thompson, D.S.; Scott, D.H.

1984-09-28

244

Shape Memory Alloys  

Microsoft Academic Search

This special issue on shape memory alloys (SMA) is an encore to a special issue on the same topic edited by us six years ago (Smart Mater. Struct.9 (5) October 2000). A total of 19 papers is offered in this issue, organized into the three broad categories of modeling, characterization and applications. In addition to thermally activated shape memory alloys,

Abhijit Bhattacharyya; Dimitris C Lagoudas

2007-01-01

245

Alloys for aerospace  

SciTech Connect

Aerospace industries require special allows with many properties tailored to meet specific needs. Prerequisites include clean melting techniques to maintain low impurity levels, tight control of alloy chemistry, and the analytical capability to characterize the product. Teledyne Wah Chang (TWC) produces specially refractory metals, including zirconium, hafnium, titanium, niobium and vanadium, which are essential components of many aerospace alloys. Alloys are prepared by vacuum-arc-remelting (VAR) or electron beam (EB) melting, and ingots are processed to products ranging from bar and tube stock to wire and foil. Chemical, mechanical, and microstructural tests are all conducted at TWC`s in-house laboratory facilities. Of the alloys described here, Ti-3Al-2.5V, Tiadyne 3515 (Alloy C), NiTiFe, and C-103 are produced commercially, while orthorhombic titanium aluminides are promising candidates for future light-weight composite matrices.

Tuominen, S.; Wojcik, C. [Teledyne Wah Chang, Albany, OR (United States)

1995-04-01

246

Alloys in energy development  

SciTech Connect

The development of new and advanced energy systems often requires the tailoring of new alloys or alloy combinations to meet the novel and often stringent requirements of those systems. Longer life at higher temperatures and stresses in aggressive environments is the most common goal. Alloy theory helps in achieving this goal by suggesting uses of multiphase systems and intermediate phases, where solid solutions were traditionally used. However, the use of materials under non-equilibrium conditions is now quite common - as with rapidly solidified metals - and the application of alloy theory must be modified accordingly. Under certain conditions, as in a reactor core, the rate of approach to equilibrium will be modified; sometimes a quasi-equilibrium is established. Thus an alloy may exhibit enhanced general diffusion at the same time as precipitate particles are being dispersed and solute atoms are being carried to vacancy sinks. We are approaching an understanding of these processes and can begin to model these complex systems.

Frost, B.R.T.

1984-02-01

247

(Si){sub 5-2y}(AlP){sub y} alloys assembled on Si(100) from Al-P-Si{sub 3} building units  

SciTech Connect

An original class of IV/III-V hybrid (Si){sub 5-2y}(AlP){sub y}/Si(100) semiconductors have been produced via tailored interactions of molecular P(SiH{sub 3}){sub 3} and atomic Al yielding tetrahedral ''Al-P-Si{sub 3}'' building blocks. Extensive structural, optical, and vibrational characterization corroborates that these units condense to assemble single-phase, monocrystalline alloys containing 60%-90% Si (y = 0.3-1.0) as nearly defect-free layers lattice-matched to Si. Spectroscopic ellipsometry and density functional theory band structure calculations indicate mild compositional bowing of the band gaps, suggesting that the tuning needed for optoelectronic applications should be feasible.

Watkins, T.; Chizmeshya, A. V. G.; Kouvetakis, J. [Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604 (United States); Jiang, L.; Xu, C.; Smith, D. J.; Menendez, J. [Department of Physics, Arizona State University, Tempe, Arizona 85287-1504 (United States)

2012-01-09

248

Controlled expansion alloy  

Microsoft Academic Search

In an age hardenable controlled expansion alloy essentially devoid of chromium, the combination of short term tensile properties and elevated temperature properties, particularly notch rupture strength, are improved by the inclusion therein of silicon in an amount leass than 1%.

J. S. Smith; D. F. Jr. Smith

1984-01-01

249

Manufacture of Superplastic Alloys.  

National Technical Information Service (NTIS)

The requirements in a superplastic sheet material are either to possess a fine uniform grain size or to be capable of developing such a grain structure during the course of superplastic deformation. Alloys that are currently being commercially exploited f...

R. Grimes

1989-01-01

250

Calculations of the temperature and alloy composition effects on the optical properties of AlxGa1-xAsySb1-y and GaxIn1-xAsySb1-y in the spectral range 0.5-6 eV  

NASA Astrophysics Data System (ADS)

A detailed analysis is presented on the temperature and alloy composition dependence of the optical properties of III-V alloys AlxGa1-xAsySb1-y and GaxIn1-xAsySb1-y in the energy range 0.5-6 eV. Expressions for the complex dielectric function are based on a semiempirical phenomenological model, which takes under consideration indirect and direct transitions below and above the fundamental absorption edge. Dielectric function and absorption coefficient calculations are in satisfactory agreement with available experimental data. Other dielectric related optical data, such as the refractive index, extinction, and reflection coefficients, can also be obtained from the model.

Gonzalez-Cuevas, Juan A.; Refaat, Tamer F.; Abedin, M. Nurul; Elsayed-Ali, Hani E.

2007-07-01

251

Mechanical alloying and milling  

Microsoft Academic Search

Mechanical alloying (MA) is a solid-state powder processng technique involving repeated welding, fracturing, and rewelding of powder particles in a high-energy ball mill. Originally developed to produce oxide-dispersion strengthened (ODS) nickel- and iron-base superalloys for applications in the aerospace industry, MA has now been shown to be capable of synthesizing a variety of equilibrium and non-equilibrium alloy phases starting from

C. Suryanarayana

2001-01-01

252

Thermoelectric figure of merit of (In0.53Ga0.47As)0.8(In0.52Al0.48As)0.2 III-V semiconductor alloys Je-Hyeong Bahk,1 Zhixi Bian,2 Mona Zebarjadi,2 Joshua M. O. Zide,3 Hong Lu,1,4 Dongyan Xu,5 Joseph P. Feser,5  

E-print Network

with light elec- tron effective masses such as InAs and InSb were studied because of their relatively high ZT that ZT can be much higher than unity at room temperature for ultrathin NWs such as InSb NWs thin- ner than 15 nm and InAs NWs thinner than 5 nm in diameter.9 The InSb and InAs nanowires have been success

253

Novel compound semiconductor devices based on III-V nitrides  

SciTech Connect

New developments in dry and wet etching, ohmic contacts and epitaxial growth of Ill-V nitrides are reported. These make possible devices such as microdisk laser structures and GaAs/AlGaAs heterojunction bipolar transistors with improved InN ohmic contacts.

Pearton, S.J.; Abernathy, C.R. [Florida Univ., Gainesville, FL (United States); Ren, F. [AT & T Bell Laboratories, Murray Hill, NJ (United States)] [and others

1995-10-01

254

Ion implantation and annealing studies in III-V nitrides  

SciTech Connect

Ion implantation doping and isolation is expected to play an enabling role for the realization of advanced III-Nitride based devices. In fact, implantation has already been used to demonstrate n- and p-type doping of GaN with Si and Mg or Ca, respectively, as well as to fabricate the first GaN junction field effect transistor. Although these initial implantation studies demonstrated the feasibility of this technique for the III-Nitride materials, further work is needed to realize its full potential. After reviewing some of the initial studies in this field, the authors present new results for improved annealing sequences and defect studies in GaN. First, sputtered AlN is shown by electrical characterization of Schottky and Ohmic contacts to be an effect encapsulant of GaN during the 1,100 C implant activation anneal. The AlN suppresses N-loss from the GaN surface and the formation of a degenerate n{sup +}-surface region that would prohibit Schottky barrier formation after the implant activation anneal. Second, they examine the nature of the defect generation and annealing sequence following implantation using both Rutherford Backscattering (RBS) and Hall characterization. They show that for a Si-dose of 1 x 10{sup 16} cm{sup {minus}2} 50% electrical donor activation is achieved despite a significant amount of residual implantation-induced damage in the material.

Zolper, J.C. [Sandia National Labs., Albuquerque, NM (United States); Pearton, S.J. [Univ. of Florida, Gainesville, FL (United States). Dept. of Materials Science and Engineering; Williams, J.S.; Tan, H.H. [Australian National Univ., Canberra (Australia). Dept. of Electronic Materials Engineering; Karlicek, R.J. Jr.; Stall, R.A. [Emcore Corp., Somerset, NJ (United States)

1996-12-31

255

Surface Localization of Buried III-V Semiconductor Nanostructures.  

PubMed

In this work, we study the top surface localization of InAs quantum dots once capped by a GaAs layer grown by molecular beam epitaxy. At the used growth conditions, the underneath nanostructures are revealed at the top surface as mounding features that match their density with independence of the cap layer thickness explored (from 25 to 100 nm). The correspondence between these mounds and the buried nanostructures is confirmed by posterior selective strain-driven formation of new nanostructures on top of them, when the distance between the buried and the superficial nanostructures is short enough (d = 25 nm). PMID:20596455

Alonso-González, P; González, L; Fuster, D; Martín-Sánchez, J; González, Yolanda

2009-01-01

256

Asiago eclipsing binaries program. III. V570 Persei  

NASA Astrophysics Data System (ADS)

The orbit and physical parameters of the previously unsolved double-lined eclipsing binary V570 Per, discovered by the Hipparcos satellite, were derived using high-resolution Echelle spectroscopy and B, V photoelectric photometry. The metallicity from ?2 analysis of the spectra is [ M/H]=+0.02±0.03, and reddening from interstellar NaI and KI absorption lines is EB-V=0.023±0.007. V570 Per is a well-detached system, with shallow eclipses (due to low orbital inclination) and no sign of chromospheric activity. The two components have masses of 1.449±0.006 and 1.350±0.006~M_? and spectral types F3 and F5, respectively. They are both still within the main sequence band (T_1=6842±25 K, T_2=6562± 25 K from ?2 analysis, R_1=1.523±0.030, R_2=1.388± 0.019 R_? derived by forcing the orbital solution to conform to the spectroscopic light ratio) and are dynamically relaxed to co-rotation with the orbital motion (V_rot,1,2 sin i=40 and 36 (±1) km s-1). The distance to V570 Per obtained from the orbital solution is 123 ±2 pc, in excellent agreement with the revised Hipparcos distance of 123±11 pc. The observed properties of V570 Per components were compared to available families of stellar evolutionary tracks and, in particular, to BaSTI models computed on purpose for exactly the observed masses and varied chemical compositions. This system is interesting since both components have their masses in the range where the efficiency of convective core overshooting has to decrease with the total mass as a consequence of the decreasing size of the convective core during the central H-burning stage. Our numerical simulations show that, in order to match all empirical constraints, a small but not null overshooting is required, with efficiencies of ?_OV=0.14 and 0.11 for the 1.449 and 1.350 M_? components, respectively. This confirms the finding of Paper II on the similar system V505 Per. At the ?0.8 Gyr age of the system, the element diffusion has reduced the surface metallicity of the models from the initial [ M/H]=+0.17 to [ M/H]=+0.02, in perfect agreement with the spectroscopically derived [ M/H]=+0.02± 0.03 value. Based mainly on data obtained with Asiago 1.82 m telescope. Table 1 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/483/263

Tomasella, L.; Munari, U.; Cassisi, S.; Siviero, A.; Dallaporta, S.; Sordo, R.; Zwitter, T.

2008-05-01

257

Characterization of novel III-V semiconductor devices  

E-print Network

This thesis presents the characterization of tunnel junctions and tunnel-junction-coupled lasers. The reverse-biased leakage current in a tunnel junction can be exploited to tunnel electrons from the valence band of one ...

Young, Sue Y

2006-01-01

258

Catalyst-free, III-V nanowire photovoltaics  

NASA Astrophysics Data System (ADS)

We report on room temperature, photovoltaic operation of catalyst-free GaAs p-i-n junction nanowire arrays. Growth studies were first performed to determine the optimum conditions for controlling the vertical and lateral growth of the nanowires. Following this, devices consisting of axial p-i-n junctions were fabricated by planarising the nanowire arrays with a hard baked polymer. We discuss the photovoltaic properties of this proof-of-concept device, and significant improvements to be made during the growth.

Davies, D. G.; Lambert, N.; Fry, P. W.; Foster, A.; Krysa, A. B.; Wilson, L. R.

2014-05-01

259

Nano-scale ohmic contacts for III-V MOSFETs  

E-print Network

As modem silicon CMOS has been scaled down to extremely small dimensions, there is an urgent need for technological innovations of new devices architectures that would allow the continuation of Moore's Law into the future. ...

Lu, Wenjie

2014-01-01

260

The Performance of Advanced III-V Solar Cells  

NASA Technical Reports Server (NTRS)

Test results show triple junction solar cells with efficiencies as high as 27% at 28C and 136.7 mw/sq cm. Triple junction cells also achieve up to 27.5% at -120 C and 5 mw/sq cm, conditions applicable to missions to Jupiter. Some triple junction cells show practically no degradation as a result of Low Intensity Low Temperature (LILT) effects, while others show some; this degradation can be overcome with minor changes to the cell design.

Mueller, Robert L.; Gaddy, Edward; Day, John H. (Technical Monitor)

2002-01-01

261

First III–V-nitride-based violet laser diodes  

Microsoft Academic Search

InGaN multi-quantum-well (MQW) structure laser diodes (LDs) were grown by metalorganic chemical vapor deposition on a sapphire substrate with (112?0) orientation (A face). The mirror facet for a laser cavity was formed by cleaving the substrate along the (11?02) orientation (R-face). The structure of the LDs was an InGaN MQW\\/GaN\\/AlGaN separate confinement heterostructure (SCH). As an active layer, the InGaN

Shuji Nakamura

1997-01-01

262

Vertical III-V nanowire device integration on Si(100).  

PubMed

We report complementary metal-oxide-semiconductor (CMOS)-compatible integration of compound semiconductors on Si substrates. InAs and GaAs nanowires are selectively grown in vertical SiO2 nanotube templates fabricated on Si substrates of varying crystallographic orientations, including nanocrystalline Si. The nanowires investigated are epitaxially grown, single-crystalline, free from threading dislocations, and with an orientation and dimension directly given by the shape of the template. GaAs nanowires exhibit stable photoluminescence at room temperature, with a higher measured intensity when still surrounded by the template. Si-InAs heterojunction nanowire tunnel diodes were fabricated on Si(100) and are electrically characterized. The results indicate a high uniformity and scalability in the fabrication process. PMID:24628529

Borg, Mattias; Schmid, Heinz; Moselund, Kirsten E; Signorello, Giorgio; Gignac, Lynne; Bruley, John; Breslin, Chris; Das Kanungo, Pratyush; Werner, Peter; Riel, Heike

2014-04-01

263

III-V CMOS: What have we learned from HEMTs?  

E-print Network

The ability of Si CMOS to continue to scale down transistor size while delivering enhanced logic performance has recently come into question. An end to Moore's Law threatens to bring to a halt the microelectronics revolution: ...

del Alamo, Jesus A.

264

Structural defects in Si-doped III-V Nitrides  

SciTech Connect

Transmission electron microscopy has been used to studyundoped and Si-doped InGaN/GaN layers. The doped layers show formation ofextrinsic dislocation loops. These defects are not formed in the undopedsamples. The highly-Si-doped layers show failure of selectivephotoelectrochemical wet-etching used for device fabrication. This lossof etching selectivity is attributed to Si-induced defects evenlydistributed in the InGaN layers and its vicinity.

Zakharov, Dmitri N.; Liliental-Weber, Zuzanna; Gao, Yan; Hu, Evelyn

2005-05-05

265

Structural defects in Si-doped III-V Nitrides  

SciTech Connect

Transmission electron microscopy has been used to study undoped and Si-doped InGaN/GaN layers. The doped layers show formation of extrinsic dislocation loops. These defects are not formed in the undoped samples. The highly-Si-doped layers show failure of selective photoelectrochemical wet-etching used for device fabrication. This loss of etching selectivity is attributed to Si-induced defects evenly distributed in the InGaN layers and its vicinity.

Zakharov, Dmitri N.; Liliental-Weber, Zuzanna; Gao, Yan; Hu, Evelyn

2005-05-05

266

Translating alloy using Boolean circuits  

E-print Network

Alloy is a automatically analyzable modelling language based on first-order logic. An Alloy model can be translated into a Boolean formula whose satisfying assignments correspond to instances in the model. Currently, the ...

Daitch, Samuel Isaac

2004-01-01

267

Semiconductor alloys - Structural property engineering  

NASA Technical Reports Server (NTRS)

Semiconductor alloys have been used for years to tune band gaps and average bond lengths to specific applications. Other selection criteria for alloy composition, and a growth technique designed to modify their structural properties, are presently considered. The alloys Zn(1-y)Cd(y)Te and CdSe(y)Te(1-y) are treated as examples.

Sher, A.; Van Schilfgaarde, M.; Berding, M.; Chen, A.-B.

1987-01-01

268

De-alloyed platinum nanoparticles  

SciTech Connect

A method of producing de-alloyed nanoparticles. In an embodiment, the method comprises admixing metal precursors, freeze-drying, annealing, and de-alloying the nanoparticles in situ. Further, in an embodiment de-alloyed nanoparticle formed by the method, wherein the nanoparticle further comprises a core-shell arrangement. The nanoparticle is suitable for electrocatalytic processes and devices.

Strasser, Peter (Houston, TX); Koh, Shirlaine (Houston, TX); Mani, Prasanna (Houston, TX); Ratndeep, Srivastava (Houston, TX)

2011-08-09

269

Above-room-temperature ferromagnetism in GaSb/Mn digital alloys*  

NASA Astrophysics Data System (ADS)

As an effort to realize spintronic applications with 6.1 angstrom III-V semiconductors, digital alloys of GaSb/Mn were fabricated by molecular beam epitaxy and characterized with a wide range of experimental techniques. Cross sectional scanning electron microscopy studies indicate that the Mn-containing layers consist of quasi-2D islands of MnSb and isolated Mn ions. Two ferromagnetic phases were observed, with a low temperature phase having a Tc typically below 50 K and the other one observable at 400 K. The properties of the two phases, including their anisotropy and interaction, were studied with both magnetization measurements and magnetotransport techniques. For external tuning of ferromagnetism in this material system, gated structures were fabricated for studies of electrically controlled ferromagnetism. Systematic and significant changes in coercive fields were observed as a function of applied bias. * In collaboration with G. B. KIM, M. CHEON, X. CHEN, S. WANG, B. D. McCOMBE, Y. SASAKI, X. LIU, T. WOJTOWICZ, J. K. FURDYNA, G. BOISHIN and L. J. WHITMAN; this work was supported by DARPA/ONR (N00014-00-1-0951)

Luo, H.

2003-03-01

270

Optical absorption and emission of InP sub 1 minus x Sb sub x alloys  

SciTech Connect

A detailed optical study of the metastable III/V semiconductor alloy InP{sub 1{minus}{ital x}}Sb{sub {ital x}} is presented. InP{sub 1{minus}{ital x}}Sb{sub {ital x}} layers are grown throughout the entire compositional range by atmospheric pressure organometallic vapor phase epitaxy on InP, InAs, and InSb substrates. Composition and strain are measured by combined electron microprobe analysis and x-ray diffractometry. The dependence of band gap on composition is experimentally established for the first time from absorption spectra measured at 10 and 300 K. The resultant value of the band-gap bowing parameter is 1.52{plus minus}0.08 eV, independent of temperature. The absorption spectra show the InP{sub 1{minus}{ital x}}Sb{sub {ital x}} layers to have long band tails, which extend further into the gap as the Sb concentration is increased. The band tails are induced by compositional clustering. Photoluminescence (PL) spectra are measured between 10 and 300 K. The PL peaks are assigned to recombination between carriers occupying band-tail states or to recombination via deep centers in the gap.

Reihlen, E.H.; Jou, M.J.; Fang, Z.M.; Stringfellow, G.B. (Department of Electrical Engineering, University of Utah, Salt Lake City, UT (USA) Materials Science and Engineering, University of Utah, Salt Lake City, UT (USA))

1990-11-01

271

Hydrogen in titanium alloys  

SciTech Connect

The titanium alloys that offer properties worthy of consideration for fusion reactors are Ti-6Al-4V, Ti-6Al-2Sn-4Zr-2Mo-Si (Ti-6242S) and Ti-5Al-6Sn-2Zr-1Mo-Si (Ti-5621S). The Ti-6242S and Ti-5621S are being considered because of their high creep resistance at elevated temperatures of 500/sup 0/C. Also, irradiation tests on these alloys have shown irradiation creep properties comparable to 20% cold worked 316 stainless steel. These alloys would be susceptible to slow strain rate embrittlement if sufficient hydrogen concentrations are obtained. Concentrations greater than 250 to 500 wppm hydrogen and temperatures lower than 100 to 150/sup 0/C are approximate threshold conditions for detrimental effects on tensile properties. Indications are that at the elevated temperature - low hydrogen pressure conditions of the reactors, there would be negligible hydrogen embrittlement.

Wille, G W; Davis, J W

1981-04-01

272

Microstructural studies on Alloy 693  

NASA Astrophysics Data System (ADS)

Superalloy 693, is a newly identified ‘high-temperature corrosion resistant alloy’. Present study focuses on microstructure and mechanical properties of the alloy prepared by double ‘vacuum melting’ route. In general, the alloy contains ordered Ni3Al precipitates distributed within austenitic matrix. M6C primary carbide, M23C6 type secondary carbide and NbC particles are also found to be present. Heat treatment of the alloy at 1373 K for 30 min followed by water quenching (WQ) brings about a microstructure that is free from secondary carbides and Ni3Al type precipitates but contains primary carbides. Tensile property of Alloy 693 materials was measured with as received and solution annealed (1323 K, 60 min, WQ) and (1373 K, 30 min, WQ) conditions. Yield strength, ultimate tensile strength (UTS) and hardness of the alloy are found to drop with annealing. It is noted that in annealed condition, considerable cold working of the alloy can be performed.

Halder, R.; Dutta, R. S.; Sengupta, P.; Samajdar, I.; Dey, G. K.

2014-10-01

273

High Strength Ferritic Alloy.  

National Technical Information Service (NTIS)

A high-strength ferritic alloy is described which is useful for fast reactor duct and cladding applications. An iron base contains from about 9% to about 13% by weight chromium, from about 4% to about 8% by weight molybdenum, from about 0.2% to about 0.8%...

W. C. Hagel, F. A. Smidt, M. K. Korenko

1977-01-01

274

Molybdenum-based alloy  

SciTech Connect

A molybdenum-based alloy improved in mechanical strength and hot workability, which consists of 0.01 to 5.0% by weight of vanadium, 10 to 100 ppm of boron, 10 to 1,000 ppm of carbon, and the balance of molybdenum.

Koizumi, H.; Ishihara, H.; Kawakita, K.; Matsumoto, T.

1984-02-07

275

Superplasticity in aluminum alloys  

SciTech Connect

We have characterized in the Al-Mg system the microstructure and mechanical properties of a cold-rolled Al-6Mg-0.3Sc alloy. The alloy exhibited superplasticity at relatively high strain rates (about 10-2 s-1). At a strain rate of 10-2 s-1 there exists a wide temperature range (475-520`C) within which the tensile elongation is over 1000%. There also exists a wide strain rate range (10-3 - 10-1 s-1) within which the tensile elongation is over 500%. The presence of Sc in the alloy results in a uniform distribution of fine coherent Al3SC precipitates which effectively pin grain and subgrain boundaries during static and continuous recrystallization. As a result, the alloy retains its fine grain size (about 7 micron), even after extensive superplastic deformation (>1000%). During deformation, dislocations Mg with a high Schmidt factor slip across subgrains but are trapped by subgrain boundaries, as a result of the strong pining of Al3Sc. This process leads to the conversion of low-angled subgrain boundaries to high-angled grain boundaries and the subsequent grain boundary sliding, which produces superelasticity. A model is proposed to describe grain boundary sliding accommodated by dislocation glide across grains with a uniform distribution of coherent precipitates. The model predictions is consistent with experimental observations.

Nieh, T. G.

1997-12-01

276

Titanium alloy development  

Microsoft Academic Search

Over the last decade, the focus of titanium alloy development has shifted from aerospace to industrial applications. The titanium industry has been very dependent on the aerospace market, and this sector will constitute a significant percentage of total consumption for years to come. However, titanium is increasingly being selected for industrial products as a result of value analyses based on

1996-01-01

277

High-temperature property data: Ferrous alloys  

Microsoft Academic Search

In this book over 250 alloys are organized by AISI number into 10 major sections: Irons, Carbon Steels, Alloy Steels, Low Alloy Constructional Steels, Ultra High Strength Steels, Tool Steels, Maraging Steels, Wrought Stainless Steels, Heat Resistnat Casting Alloys, and Iron Based Rought Superalloys. Each alloy record lists the designation, specifications, UNS number, composition, product forms and a comment on

Rothman

1987-01-01

278

Grindability of dental magnetic alloys.  

PubMed

In this study, the grindability of cast magnetic alloys (Fe-Pt-Nb magnetic alloy and magnetic stainless steel) was evaluated and compared with that of conventional dental casting alloys (Ag-Pd-Au alloy, Type 4 gold alloy, and cobalt-chromium alloy). Grindability was evaluated in terms of grinding rate (i.e., volume of metal removed per minute) and grinding ratio (i.e., volume ratio of metal removed compared to wheel material lost). Solution treated Fe-Pt-Nb magnetic alloy had a significantly higher grinding rate than the aged one at a grinding speed of 750-1500 m x min(-1). At 500 m x min(-1), there were no significant differences in grinding rate between solution treated and aged Fe-Pt-Nb magnetic alloys. At a lower speed of 500 m x min(-1) or 750 m x min(-1), it was found that the grinding rates of aged Fe-Pt-Nb magnetic alloy and stainless steel were higher than those of conventional casting alloys. PMID:16022434

Hayashi, Eisei; Kikuchi, Masafumi; Okuno, Osamu; Kimura, Kohei

2005-06-01

279

Advanced ordered intermetallic alloy deployment  

SciTech Connect

The need for high-strength, high-temperature, and light-weight materials for structural applications has generated a great deal of interest in ordered intermetallic alloys, particularly in {gamma}-based titanium aluminides {gamma}-based TiAl alloys offer an attractive mix of low density ({approximately}4g/cm{sup 3}), good creep resistance, and high-temperature strength and oxidation resistance. For rotating or high-speed components. TiAl also has a high damping coefficient which minimizes vibrations and noise. These alloys generally contain two phases. {alpha}{sub 2} (DO{sub 19} structure) and {gamma} (L 1{sub 0}), at temperatures below 1120{degrees}C, the euticoid temperature. The mechanical properties of TiAl-based alloys are sensitive to both alloy compositions and microstructure. Depending on heat-treatment and thermomechanical processing, microstructures with near equiaxed {gamma}, a duplex structure (a mix of the {gamma} and {alpha}{sub 2} phases) can be developed in TiAl alloys containing 45 to 50 at. % Al. The major concern for structural use of TiAl alloys is their low ductility and poor fracture resistance at ambient temperatures. The purpose of this project is to improve the fracture toughness of TiAl-based alloys by controlling alloy composition, microstructure and thermomechanical treatment. This work is expected to lead to the development of TiAl alloys with significantly improved fracture toughness and tensile ductility for structural use.

Liu, C.T.; Maziasz, P.J.; Easton, D.S. [Oak Ridge National Lab., TN (United States)

1997-04-01

280

Filler metal alloy for welding cast nickel aluminide alloys  

DOEpatents

A filler metal alloy used as a filler for welding cast nickel aluminide alloys contains from about 15 to about 17 wt. % chromium, from about 4 to about 5 wt. % aluminum, equal to or less than about 1.5 wt. % molybdenum, from about 1 to about 4.5 wt. % zirconium, equal to or less than about 0.01 wt. % yttrium, equal to or less than about 0.01 wt. % boron and the balance nickel. The filler metal alloy is made by melting and casting techniques such as are melting the components of the filler metal alloy and cast in copper chill molds. 3 figs.

Santella, M.L.; Sikka, V.K.

1998-03-10

281

Magnesium-lithium casting alloys  

NASA Technical Reports Server (NTRS)

The strength properties of magnesium-lithium alloys at room, low, and high temperatures are investigated. It is found that the alloys may have practical application at ambient temperatures up to 100 C, that negative temperatures have a favorable influence on the alloy strength, and that cyclic temperature variations have practically no effect on the strength characteristics. The influence of chemical coatings on corrosion resistance of the MgLi alloys is examined. Several facilities based on pressure casting machines, low-pressure casting machines, and magnetodynamic pumps were designed for producing MgLi alloy castings. Results were obtained for MgLi alloys reinforced with fibers having a volumetric content of 15%.

Latenko, V. P.; Silchenko, T. V.; Tikhonov, V. A.; Maltsev, V. P.; Korablin, V. P.

1974-01-01

282

Materials data handbook, aluminum alloy 7075  

NASA Technical Reports Server (NTRS)

Materials data handbook on aluminum alloy 7075 includes data on the properties of the alloy at cryogenic, ambient, and elevated temperatures, and other pertinent engineering information required for the design and fabrication of components and equipment utilizing this alloy.

Sessler, J.; Weiss, V.

1967-01-01

283

Alchemy: Transmuting Base Alloy Specifications into Implementations  

E-print Network

Alchemy: Transmuting Base Alloy Specifications into Implementations Shriram Krishnamurthi Brown University Daniel J. Dougherty WPI Kathi Fisler WPI Daniel Yoo WPI ABSTRACT Alloy specifications are used to define lightweight models of systems. We present Alchemy, which compiles Alloy specifi- cations

Krishnamurthi, Shriram

284

Alloy Interface Interdiffusion Modeled  

NASA Technical Reports Server (NTRS)

With renewed interest in developing nuclear-powered deep space probes, attention will return to improving the metallurgical processing of potential nuclear fuels so that they remain dimensionally stable over the years required for a successful mission. Previous work on fuel alloys at the NASA Glenn Research Center was primarily empirical, with virtually no continuing research. Even when empirical studies are exacting, they often fail to provide enough insight to guide future research efforts. In addition, from a fundamental theoretical standpoint, the actinide metals (which include materials used for nuclear fuels) pose a severe challenge to modern electronic-structure theory. Recent advances in quantum approximate atomistic modeling, coupled with first-principles derivation of needed input parameters, can help researchers develop new alloys for nuclear propulsion.

Bozzolo, Guillermo H.; Garces, Jorge E.; Abel, Phillip B.

2003-01-01

285

Titanium alloy development  

SciTech Connect

Over the last decade, the focus of titanium alloy development has shifted from aerospace to industrial applications. The titanium industry has been very dependent on the aerospace market, and this sector will constitute a significant percentage of total consumption for years to come. However, titanium is increasingly being selected for industrial products as a result of value analyses based on life cycle cost rather than initial price. This shift in development emphasis is not unique to Timet, and efforts to diversify titanium usage are evident throughout the industry. Today, very little producer-industry research is aimed at fundamentally new alloys. Strategy is centered on developing or improving manufacturing processes that offer new product forms, or more cost-effective products. The goal is to expand current non-aerospace markets, or penetrate new ones. This article reviews developments in the various market sectors, together with the future thrust of research.

Allen, P. [Titanium Metals Corp., Henderson, NV (United States)

1996-10-01

286

Nanocrystal dispersed amorphous alloys  

NASA Technical Reports Server (NTRS)

Compositions and methods for obtaining nanocrystal dispersed amorphous alloys are described. A composition includes an amorphous matrix forming element (e.g., Al or Fe); at least one transition metal element; and at least one crystallizing agent that is insoluble in the resulting amorphous matrix. During devitrification, the crystallizing agent causes the formation of a high density nanocrystal dispersion. The compositions and methods provide advantages in that materials with superior properties are provided.

Perepezko, John H. (Inventor); Allen, Donald R. (Inventor); Foley, James C. (Inventor)

2001-01-01

287

Shape memory alloy actuator  

DOEpatents

An actuator for cycling between first and second positions includes a first shaped memory alloy (SMA) leg, a second SMA leg. At least one heating/cooling device is thermally connected to at least one of the legs, each heating/cooling device capable of simultaneously heating one leg while cooling the other leg. The heating/cooling devices can include thermoelectric and/or thermoionic elements.

Varma, Venugopal K. (Knoxville, TN)

2001-01-01

288

High temperature shape memory alloys  

SciTech Connect

Several alloy systems can be selected for high-temperature shape memory alloys, defined as alloys with stable reverse transformation temperatures above 120 C. However, due to the lack of minimum quality standards for stability, ductility, functional behavior and reliability, no successful applications have been realized so far. Research on high temperature shape memory alloys (HTSMA) is, nevertheless, an important topic not only for scientific reasons but also due to the market pull. This paper reviews existing systems of HTSMA pointing out their weak and strong parts.

Humbeeck, J. van [K.U. Leuven, Heverlee (Belgium). Dept. of Metallurgy and Materials Engineering

1999-01-01

289

Better Alloys with Quantum Design  

NASA Astrophysics Data System (ADS)

Alloy discovery and development is slowed by trial and error methods used to identify beneficial alloying elements. This fact has led to suggestions that integrating quantum theory and modeling with traditional experimental approaches might accelerate the pace of alloy discovery. We report here on one such effort, using advances in first principles computation along with an evolving theory that allows for the partitioning of charge density into chemically meaningful structures, alloying elements that improve the adhesive properties of interfaces common to high strength steels have been identified.

Jones, Travis E.; Eberhart, Mark E.; Imlay, Scott; Mackey, Craig; Olson, Greg B.

2012-09-01

290

Alloy Phase Formation by Mechanical Alloying:. Constraints and Mechanisms  

Microsoft Academic Search

Alloy phase formation in binary metallic systems by mechanical alloying (MA) of elemental powders is briefly reviewed. Our recent results indicate the inadequacy of the current understanding of the MA process, which has been depicted as an isothermal solid-state interdiffusion reaction under interfacial, metastable, equilibrium in layered composites. A structural and thermodynamic analysis of the supersaturation followed by amorphization in

E. Ma; M. Atzmon

1992-01-01

291

Shape memory alloy thaw sensors  

DOEpatents

A sensor permanently indicates that it has been exposed to temperatures exceeding a critical temperature for a predetermined time period. An element of the sensor made from shape memory alloy changes shape when exposed, even temporarily, to temperatures above the Austenitic temperature of the shape memory alloy. The shape change of the SMA element causes the sensor to change between two readily distinguishable states.

Shahinpoor, Mohsen (Albuquerque, NM); Martinez, David R. (Albuquerque, NM)

1998-01-01

292

Fatigue behavior of titanium alloys  

Microsoft Academic Search

This symposium was international in nature, with leaders in the fields of fatigue technology and the metallurgy of titanium from the US, Europe and Asia. It covered basic research, development, applications and modeling--life predictions and design of both fatigue crack initiation and propagation of titanium alloys. There were presentations on the full range of titanium alloy systems, from commercially pure

R. R. Boyer; D. Eylon; G. Luetjering

1999-01-01

293

Heat storage in alloy transformations  

NASA Astrophysics Data System (ADS)

The feasibility of using metal alloys as thermal energy storage media was determined. The following major elements were studied: (1) identification of congruently transforming alloys and thermochemical property measurements; (2) development of a precise and convenient method for measuring volume change during phase transformation and thermal expansion coefficients; (3) development of a numerical modeling routine for calculating heat flow in cylindrical heat exchangers containing phase change materials; and (4) identification of materials that could be used to contain the metal alloys. Several eutectic alloys and ternary intermetallic phases were determined. A method employing X-ray absorption techniques was developed to determine the coefficients of thermal expansion of both the solid and liquid phases and the volume change during phase transformation from data obtained during one continuous experimental test. The method and apparatus are discussed and the experimental results are presented. The development of the numerical modeling method is presented and results are discussed for both salt and metal alloy phase change media.

Birchenall, C. E.; Gueceri, S. I.; Farkas, D.; Labdon, M. B.; Nagaswami, N.; Pregger, B.

1981-03-01

294

Equivalent crystal theory of alloys  

NASA Technical Reports Server (NTRS)

Equivalent Crystal Theory (ECT) is a new, semi-empirical approach to calculating the energetics of a solid with defects. The theory has successfully reproduced surface energies in metals and semiconductors. The theory of binary alloys to date, both with first-principles and semi-empirical models, has not been very successful in predicting the energetics of alloys. This procedure is used to predict the heats of formation, cohesive energy, and lattice parameter of binary alloys of Cu, Ni, Al, Ag, Au, Pd, and Pt as functions of composition. The procedure accurately reproduces the heats of formation versus composition curves for a variety of binary alloys. The results are then compared with other approaches such as the embedded atom and lattice parameters of alloys from pure metal properties more accurately than Vegard's law is presented.

Bozzolo, Guillermo; Ferrante, John

1991-01-01

295

Normal evaporation of binary alloys  

NASA Technical Reports Server (NTRS)

In the study of normal evaporation, it is assumed that the evaporating alloy is homogeneous, that the vapor is instantly removed, and that the alloy follows Raoult's law. The differential equation of normal evaporation relating the evaporating time to the final solute concentration is given and solved for several important special cases. Uses of the derived equations are exemplified with a Ni-Al alloy and some binary iron alloys. The accuracy of the predicted results are checked by analyses of actual experimental data on Fe-Ni and Ni-Cr alloys evaporated at 1600 C, and also on the vacuum purification of beryllium. These analyses suggest that the normal evaporation equations presented here give satisfactory results that are accurate to within an order of magnitude of the correct values, even for some highly concentrated solutions. Limited diffusion and the resultant surface solute depletion or enrichment appear important in the extension of this normal evaporation approach.

Li, C. H.

1972-01-01

296

Heat storage in alloy transformations  

NASA Technical Reports Server (NTRS)

The feasibility of using metal alloys as thermal energy storage media was determined. The following major elements were studied: (1) identification of congruently transforming alloys and thermochemical property measurements; (2) development of a precise and convenient method for measuring volume change during phase transformation and thermal expansion coefficients; (3) development of a numerical modeling routine for calculating heat flow in cylindrical heat exchangers containing phase change materials; and (4) identification of materials that could be used to contain the metal alloys. Several eutectic alloys and ternary intermetallic phases were determined. A method employing X-ray absorption techniques was developed to determine the coefficients of thermal expansion of both the solid and liquid phases and the volume change during phase transformation from data obtained during one continuous experimental test. The method and apparatus are discussed and the experimental results are presented. The development of the numerical modeling method is presented and results are discussed for both salt and metal alloy phase change media.

Birchenall, C. E.; Gueceri, S. I.; Farkas, D.; Labdon, M. B.; Nagaswami, N.; Pregger, B.

1981-01-01

297

Thermomechanical treatment of alloys  

DOEpatents

An article of an alloy of AISI 316 stainless steel is reduced in size to predetermined dimensions by cold working in repeated steps. Before the last reduction step the article is annealed by heating within a temperature range, specifically between 1010.degree. C. and 1038.degree. C. for a time interval between 90 and 60 seconds depending on the actual temperature. By this treatment the swelling under neutron bombardment by epithermal neutrons is reduced while substantial recrystallization does not occur in actual use for a time interval of at least of the order of 5000 hours.

Bates, John F. (Ogden, UT); Brager, Howard R. (Richland, WA); Paxton, Michael M. (Gaithersburg, MD)

1983-01-01

298

Titanium alloy production technology, market prospects and industry development  

Microsoft Academic Search

Titanium alloy with a low density, high specific strength, corrosion resistance and good process performance, is the ideal structural materials for the aerospace engineering. Based on the microstructure of titanium alloys, it can be divided into ?-type titanium alloys (heat-resistant titanium alloys), ?-type titanium alloys and ?+?-type titanium alloys. The research scopes also include the fabrication technology of titanium alloys,

Chunxiang Cui; BaoMin Hu; Lichen Zhao; Shuangjin Liu

2011-01-01

299

Recent advances and developments in refractory alloys  

Microsoft Academic Search

Refractory metal alloys based on Mo, W, Re, Ta, and Nb (Cb) find applications in a wide range of aerospace applications because of their high melting points and high-temperature strength. This paper, presents recent progress in understanding and applications of these alloys. Recent studies to improve the oxidation and mechanical behavior of refractory metal alloys, and particularly Nb alloys, are

T. G. Nieh; J. Wadsworth

1993-01-01

300

High-Alloy Materials for Offshore Applications  

Microsoft Academic Search

High-alloy materials possessing good corrosion resistance in hot, sour brines are being seriously considered for offshore applications. These alloys are available in a wide range of strength levels which can be attained by the methods of cold working or precipitation hardening. Results of testing INCONEL alloys 625 and 718 and INCOLOY alloys 825 and 925 for resistance to general corrosion,

T. F. Lemke; J. A. Harris

1983-01-01

301

High performance alloy electroforming  

NASA Technical Reports Server (NTRS)

Electroformed copper and nickel are used in structural applications for advanced propellant combustion chambers. An improved process has been developed by Bell Aerospace Textron, Inc. wherein electroformed nickel-manganese alloy has demonstrated superior mechanical and thermal stability when compared to previously reported deposits from known nickel plating processes. Solution chemistry and parametric operating procedures are now established and material property data is established for deposition of thick, large complex shapes such as the Space Shuttle Main Engine. The critical operating variables are those governing the ratio of codeposited nickel and manganese. The deposition uniformity which in turn affects the manganese concentration distribution is affected by solution resistance and geometric effects as well as solution agitation. The manganese concentration in the deposit must be between 2000 and 3000 ppm for optimum physical properties to be realized. The study also includes data regarding deposition procedures for achieving excellent bond strength at an interface with copper, nickel-manganese or INCONEL 718. Applications for this electroformed material include fabrication of complex or re-entry shapes which would be difficult or impossible to form from high strength alloys such as INCONEL 718.

Malone, G. A.; Winkelman, D. M.

1989-01-01

302

B Alloy Melt  

NASA Astrophysics Data System (ADS)

The solidification of undercooled Ni-4.5 wt pct B alloy melt was investigated by using the glass fluxing technique. The alloy melt was undercooled up to ? T p ~ 245 K (245 °C), where a mixture of ?-Ni dendrite, Ni3B dendrite, rod eutectic, and precipitates was obtained. If ? T p < 175 K ± 10 K (175 °C ± 10 °C), the solidification pathway was found as primary transformation and eutectic transformation (L ? Ni3B and L ? Ni/Ni3B); if ? T p ? 175 K ± 10 K (175 °C ± 10 °C), the pathway was found as metastable eutectic transformation, metastable phase decomposition, and residual liquid solidification (L ? Ni/Ni23B6, Ni23B6 ? Ni/Ni3B, and Lr ? Ni/Ni3B). A high-speed video system was adopted to observe the solidification front of each transformation. It showed that for residual liquid solidification, the solidification front velocity is the same magnitude as that for eutectic transformation, but is an order of magnitude larger than for metastable eutectic transformation, which confirms the reaction as Lr ? Ni/Ni3B; it also showed that this velocity decreases with increasing ? T r, which can be explained by reduction of the residual liquid fraction and decrease of Ni23B6 decomposition rate.

Liu, Feng; Xu, Junfeng; Zhang, Di; Jian, Zengyun

2014-10-01

303

Oxidation resistant alloys, method for producing oxidation resistant alloys  

DOEpatents

A method for producing oxidation-resistant austenitic alloys for use at temperatures below 800.degree. C. comprising of: providing an alloy comprising, by weight %: 14-18% chromium, 15-18% nickel, 1-3% manganese, 1-2% molybdenum, 2-4% silicon, 0% aluminum and the balance being iron; heating the alloy to 800.degree. C. for between 175-250 hours prior to use in order to form a continuous silicon oxide film and another oxide film. The method provides a means of producing stainless steels with superior oxidation resistance at temperatures above 700.degree. C. at a low cost

Dunning, John S. (Corvallis, OR); Alman, David E. (Salem, OR)

2002-11-05

304

Oxidation resistant alloys, method for producing oxidation resistant alloys  

DOEpatents

A method for producing oxidation-resistant austenitic alloys for use at temperatures below 800 C. comprising of: providing an alloy comprising, by weight %: 14-18% chromium, 15-18% nickel, 1-3% manganese, 1-2% molybdenum, 2-4% silicon, 0% aluminum and the balance being iron; heating the alloy to 800 C. for between 175-250 hours prior to use in order to form a continuous silicon oxide film and another oxide film. The method provides a means of producing stainless steels with superior oxidation resistance at temperatures above 700 C. at a low cost

Dunning, John S.; Alman, David E.

2002-11-05

305

Fatigue of die cast zinc alloys  

SciTech Connect

The rotating bending fatigue limit of die cast zinc alloy 2, alloy 3, alloy 5, AcuZinc 5, and ZA-8 were determined as a part of an on-going program by ILZRO into the mechanical properties of die cast zinc. The stress-life (S-N) curves of alloys 3, 5, AcuZinc 5, and ZA-8 were determined previously. This presentation reports the results of the S-N curve for Alloy 2 and the calculated fatigue limits for all five alloys. During the previous stress-life testing, the samples were stopped at 10 million cycles and the fatigue limit for alloy 3, alloy 5, and AcuZinc 5 appeared to be higher and the fatigue limit for ZA-8 appeared to be lower than the values reported in the literature. This was further investigated in alloy 5 and ZA-8 by testing continuous cast bulk alloy 5 and ZA-8.

Schrems, K.K.; Dogan, O.N.; Goodwin, F.E. (International Lead Zinc Research Organization, Inc.)

2006-04-01

306

Heat storage in alloy transformations  

NASA Technical Reports Server (NTRS)

The feasibility of using metal alloys as thermal energy storage media was investigated. The elements selected as candidate media were limited to aluminum, copper, magnesium, silicon, zinc, calcium, and phosphorus on the basis of low cost and latent heat of transformation. Several new eutectic alloys and ternary intermetallic phases were determined. A new method employing X-ray absorption techniques was developed to determine the coefficients of thermal expansion of both the solid and liquid phases and the volume change during phase transformation. The method and apparatus are discussed and the experimental results are presented for aluminum and two aluminum-eutectic alloys. Candidate materials were evaluated to determine suitable materials for containment of the metal alloys. Graphite was used to contain the alloys during the volume change measurements. Silicon carbide was identified as a promising containment material and surface-coated iron alloys were also evaluated. System considerations that are pertinent if alloy eutectics are used as thermal energy storage media are discussed. Potential applications to solar receivers and industrial furnaces are illustrated schematically.

Birchenall, C. E.

1980-01-01

307

Cast alloys for gas turbine vanes  

Microsoft Academic Search

1.The investigation of the casting properties and manufacture of turbine vanes showed that it is possible to use investment casting for gas turbine vanes of the experimental alloys tested.2.In alloys hardened with aluminum and titanium (alloys 1 and 2) the maximum short-term strength was retained to higher temperatures than for the alloys hardened with aluminum and niobium (alloy 3) or

M. N. Efimova; E. N. Masaleva

1971-01-01

308

New Al–Mg–Sc alloys  

Microsoft Academic Search

Data on new 01515, 01523, 01535, 01545, 01570 and 01571 wrought weldable alloys based on the Al–Mg–Sc system are presented. These alloys differ from each other, mainly, by magnesium content and belong to the family of non-heat-treatable alloys. Wrought Al–Mg–Sc alloy semiproducts as-hot worked or as-annealed show much higher properties (especially yield strength) than those made from conventional Al–Mg alloys

Yu. A Filatov; V. I Yelagin; V. V Zakharov

2000-01-01

309

Advances in nickel alloys for aerospace applications  

Microsoft Academic Search

Recent advances in several areas of alloy development are examined, with emphasis on the application of these alloys to aerospace usage. Two mechanically alloyed materials are described, with emphasis on the outstanding high-temperature features of such alloys. A low-expansion high-strength alloy is described, with examples of its use in gas turbines and the Space Shuttle main engine. Properties of a

Tillack

1977-01-01

310

Dendritic Alloy Solidification Experiment (DASE)  

NASA Technical Reports Server (NTRS)

A space experiment, and supporting ground-based research, is proposed to study the microstructural evolution in free dendritic growth from a supercooled melt of the transparent model alloy succinonitrile-acetone (SCN-ACE). The research is relevant to equiaxed solidification of metal alloy castings. The microgravity experiment will establish a benchmark for testing of equiaxed dendritic growth theories, scaling laws, and models in the presence of purely diffusive, coupled heat and solute transport, without the complicating influences of melt convection. The specific objectives are to: determine the selection of the dendrite tip operating state, i.e. the growth velocity and tip radius, for free dendritic growth of succinonitrile-acetone alloys; determine the growth morphology and sidebranching behavior for freely grown alloy dendrites; determine the effects of the thermal/solutal interactions in the growth of an assemblage of equiaxed alloy crystals; determine the effects of melt convection on the free growth of alloy dendrites; measure the surface tension anisotropy strength of succinon itrile -acetone alloys establish a theoretical and modeling framework for the experiments. Microgravity experiments on equiaxed dendritic growth of alloy dendrites have not been performed in the past. The proposed experiment builds on the Isothermal Dendritic Growth Experiment (IDGE) of Glicksman and coworkers, which focused on the steady growth of a single crystal from pure supercooled melts (succinonitrile and pivalic acid). It also extends the Equiaxed Dendritic Solidification Experiment (EDSE) of the present investigators, which is concerned with the interactions and transients arising in the growth of an assemblage of equiaxed crystals (succinonitrile). However, these experiments with pure substances are not able to address the issues related to coupled heat and solute transport in growth of alloy dendrites.

Beckermann, C.; Karma, A.; Steinbach, I.; deGroh, H. C., III

2001-01-01

311

Laser surface alloying of silicon into aluminum casting alloys.  

SciTech Connect

Aluminum alloys that are easily castable tend to have lower silicon content, and hence, lower wear resistance. The use of laser surface alloying to improve the surface wear resistance of 319 and 320 aluminum alloys was examined. A silicon layer was painted onto the surface to be treated. A high power pulsed Nd:yttrium-aluminum-garnet laser with fiber-optic beam delivery was used to carry out the laser surface treatment to enhance the silicon content and produce a very fine silicon-rich phase. One advantage of using a pulsed laser beam to carry out the surface alloying is it provides a vigorous turbulence in the molten pool and enhances the dissolution of the fine silicon into the molten bath and its dispersal in a short process time. Process parameters were varied to obtain smooth single treated tracks and minimize the surface roughness from overlap of the treated tracks. Our goal is to take advantage of the vigorous turbulence characteristic of the pulsed beam to obtain desired microstructure of laser-alloyed layers, and at the same time to employ the pulse parameters that mimic continuous wave operation as closely as possible to produce the smooth surface. The surface-alloyed layer was characterized and the silicon content and microhardness profile were determined.

Xu, Z.; Leong, K. H.; Sanders, P. G.; Technology Development

2000-08-01

312

Metallic alloy stability studies  

NASA Technical Reports Server (NTRS)

The dimensional stability of candidate cryogenic wind tunnel model materials was investigated. Flat specimens of candidate materials were fabricated and cryo-cycled to assess relative dimensional stability. Existing 2-dimensional airfoil models as well as models in various stages of manufacture were also cryo-cycled. The tests indicate that 18 Ni maraging steel offers the greatest dimensional stability and that PH 13-8 Mo stainless steel is the most stable of the stainless steels. Dimensional stability is influenced primarily by metallurgical transformations (austenitic to martensitic) and manufacturing-induced stresses. These factors can be minimized by utilization of stable alloys, refinement of existing manufacturing techniques, and incorporation of new manufacturing technologies.

Firth, G. C.

1983-01-01

313

Magnesium Alloys and their Applications  

NASA Astrophysics Data System (ADS)

In the recent years there has been a dramatic increase in research activity and also applications of magnesium alloys. The driving force is the growing demand by the automobile industry resulting from the pressure to reduce weight and hence to reduce the fuel consumption. The U.S. car industry incorporates the largest amount of magnesium at the present time. In Europe, Volkswagen had a history of using magnesium in the VW Beetle. Volkswagen, in common with other major car producers has initiated a major research and development programme for advanced magnesium materials. The main emphasis of this book is in the field of general physical metallurgy and alloy development refelcting the need to provide a wider range of alloys both casting and wrought alloys to meet the increasing demands of industry. Other topics are nevertheless well represented such as casting, recycling, joining, corrosion, and surface treatment.

Kainer, Karl U.

1999-04-01

314

Copper alloys for industrial hardware  

SciTech Connect

Copper and its alloys are widely used because of their excellent electrical and thermal conductivities, outstanding resistance to corrosion, and ease of fabrication. Lifecycle costs are another important reason for new and expanding applications for copper and copper alloys. For example, lifecycle cost analyses favor the use of copper-nickel for automotive brake tubes, and copper alloys in molds for plastic parts. However, copper also competes very well on a first-cost basis in the brazed copper-and-brass radiator, and in free-cutting brass machined components. This article highlights four specific applications in which advanced copper alloys and fabrication techniques enhance the performance of industrial hardware, based largely on conductivity, corrosion resistance, and lifecycle costs.

Peters, D.T. [Copper Development Association Inc., New York, NY (United States)

1996-10-01

315

Technical Seminar "Shape Memory Alloys"  

NASA Video Gallery

Shape memory alloys are a unique group of materials that remember their original shape and return to that shape after being strained. How could the aerospace, automotive, and energy exploration ind...

316

An imperative extension to Alloy  

E-print Network

We extend the Alloy language with the standard imperative constructs; we show the mix of declarative and imperative constructs to be useful in modeling dynamic systems. We present a translation from our extended language ...

Near, Joseph Paul

317

Ordered Magnesium-Lithium alloys  

Microsoft Academic Search

Emerging technologies increasingly depend on the production of ultra-lightweight materials. Magnesium-lithium (MgLi) alloys are the lightest metallic alloys, having densities near that of plastics, and are strong enough to be used in a variety of high- performance applications. Although considerable work has been done on the MgLi system, little is known regarding potential ordered phases. An analysis of the system

Richard Taylor; Stefano Curtarolo; Gus Hart

2009-01-01

318

IMPROVEMENTS RELATING TO ZIRCONIUM ALLOYS  

Microsoft Academic Search

A Zr alloy suitable for use in aqueous media at high temperatures, e.g., ; in pressurized or boiling water reactors, is one containing 0.75to 1.25 wt% Cu ; and 0.25to 0.75 wt % Sn, the balance being Zr and impurities. The preferred ; alloy contains 1.0 wt % Cu and 0.5 wt % Sn and was found to have a

T. Raine; J. A. Robinson

1961-01-01

319

Overview of ODS Alloy Development  

Microsoft Academic Search

The overall goal of this effort is to address the materials-related barriers to expediting the use of oxide dispersion-strengthened (ODS) alloys in components required in the U.S. Department of Energy's (DOE's) Office of Fossil Energy's advanced coal combustion, gasification, and utilization processes to operate at temperatures higher than are possible with conventionally-strengthened alloys. The project is focused on the needs

Ian G Wright; Bruce A Pint

2005-01-01

320

The mechanism of mechanical alloying  

Microsoft Academic Search

The mechanical alloying process is a new method for producing composite metal powders with controlled microstructures. It\\u000a is unique in that it is an entirely solid state process, permitting dispersion of insoluble phases such as refractory oxides\\u000a and addition of reactive alloying elements such as aluminum and titanium. Interdispersion of the ingredients occurs by repeated\\u000a cold welding and fracture of

J. S. Benjamin; T. E. Volin

1974-01-01

321

Shape memory alloy thaw sensors  

DOEpatents

A sensor permanently indicates that it has been exposed to temperatures exceeding a critical temperature for a predetermined time period. An element of the sensor made from shape memory alloy changes shape when exposed, even temporarily, to temperatures above the austenitic temperature of the shape memory alloy. The shape change of the SMA element causes the sensor to change between two readily distinguishable states. 16 figs.

Shahinpoor, M.; Martinez, D.R.

1998-04-07

322

Casting Characteristics of Aluminum Die Casting Alloys  

SciTech Connect

The research program investigates the casting characteristics of selected aluminum die casting alloys. Specifically, the alloys' tendencies towards die soldering and sludge formation, and the alloys' fluidity and machinability are evaluated. It was found that: When the Fe and Mn contents of the alloy are low; caution has to be taken against possible die soldering. When the alloy has a high sludge factor, particularly a high level of Fe, measures must be taken to prevent the formation of large hardspots. For this kind of alloy, the Fe content should be kept at its lowest allowable level and the Mn content should be at its highest possible level. If there are problems in die filling, measures other than changing the alloy chemistry need to be considered first. In terms of alloy chemistry, the elements that form high temperature compounds must be kept at their lowest allowable levels. The alloys should not have machining problems when appropriate machining techniques and machining parameters are used.

Makhlouf M. Makhlouf; Diran Apelian

2002-02-05

323

Light weight alloys for aerospace applications  

Microsoft Academic Search

This book contains the proceedings of this 1989 TMS annual meeting. Topics covered include: High temperature and high strength aluminum alloys; Aluminum-lithium alloys; Metal matrix composites; and Superplasticity and joining.

E. W. Lee; E. H. Chia; N. J. Kim

1989-01-01

324

Alloy hardening and softening in binary molybdenum alloys as related to electron concentration  

NASA Technical Reports Server (NTRS)

An investigation was conducted to determine the effects of alloy additions of hafnium, tantalum, tungsten, rhenium, osmium, iridium, and platinum on hardness of molybdenum. Special emphasis was placed on alloy softening in these binary molybdenum alloys. Results showed that alloy softening was produced by those elements having an excess of s+d electrons compared to molybdenum, while those elements having an equal number or fewer s+d electrons that molybdenum failed to produce alloy softening. Alloy softening and alloy hardening can be correlated with the difference in number of s+d electrons of the solute element and molybdenum.

Stephens, J. R.; Witzke, W. R.

1972-01-01

325

Quasicrystal-reinforced Mg alloys  

NASA Astrophysics Data System (ADS)

The formation of the icosahedral phase (I-phase) as a secondary solidification phase in Mg-Zn-Y and Mg-Zn-Al base systems provides useful advantages in designing high performance wrought magnesium alloys. The strengthening in two-phase composites (I-phase + ?-Mg) can be explained by dispersion hardening due to the presence of I-phase particles and by the strong bonding property at the I-phase/matrix interface. The presence of an additional secondary solidification phase can further enhance formability and mechanical properties. In Mg-Zn-Y alloys, the co-presence of I and Ca2Mg6Zn3 phases by addition of Ca can significantly enhance formability, while in Mg-Zn-Al alloys, the co-presence of the I-phase and Mg2Sn phase leads to the enhancement of mechanical properties. Dynamic and static recrystallization are significantly accelerated by addition of Ca in Mg-Zn-Y alloy, resulting in much smaller grain size and more random texture. The high strength of Mg-Zn-Al-Sn alloys is attributed to the presence of finely distributed Mg2Sn and I-phase particles embedded in the ?-Mg matrix.

Kim, Young Kyun; Kim, Won Tae; Hyang Kim, Do

2014-04-01

326

Nickel aluminide alloys with improved weldability  

DOEpatents

Weldable nickel aluminide alloys which are essentially free, if not entirely free, of weld hot cracking are provided by employing zirconium concentrations in these alloys of greater than 2.6 wt. % or sufficient to provide a substantial presence of Ni--Zr eutectic phase in the weld so as to prevent weld hot cracking. Weld filler metals formed from these so modified nickel aluminide alloys provide for crack-free welds in previously known nickel aluminide alloys. 5 figs.

Santella, M.L.; Goodwin, G.M.

1995-05-09

327

Nickel aluminide alloys with improved weldability  

DOEpatents

Weldable nickel aluminide alloys which are essentially free, if not entirely free, of weld hot cracking are provided by employing zirconium concentrations in these alloys of greater than 2.6 wt. % or sufficient to provide a substantial presence of Ni--Zr eutectic phase in the weld so as to prevent weld hot cracking. Weld filler metals formed from these so modified nickel aluminide alloys provide for crack-free welds in previously known nickel aluminide alloys.

Santella, Michael L. (Knoxville, TN); Goodwin, Gene M. (Lenior City, TN)

1995-05-09

328

Research on Alloying Tecniques of Mischmetal in Die Casting Magnesium Alloy  

Microsoft Academic Search

An aim of the experiments is to study alloying techniques of dollop-like MM, as-cast and extruded Mg-MM master alloy in die casting AZ91D magnesium alloy at conventional cold chamber die casting temperature. The as-cast AZ91D-1.2wt%MM alloys were prepared and MM was added by different way at 720°C. The results showed that the efficiency of alloying achieved less than 50% within

Yulei Xu; Kui Zhang; Xinggang Li; Kang Zhang; Jian Lei; Haibo Yuan

2009-01-01

329

Diffusion bonding of Al7075 alloy to titanium aluminum vanadate alloy  

Microsoft Academic Search

The aluminum alloy (Al7075) and titanium alloy (Ti-6Al-4V) are used in a variety of applications in the aerospace industry. However, the high cost of Ti-6Al-4V alloy has been a major factor which has limited its use and therefore, the ability to join Al7075 alloy to Ti-6Al-4V alloy can provide a product that is less costly, but retains the high strength

Abdulaziz Nasser Alhazaa

2010-01-01

330

Electromagnetic stirring of aluminium-silicon alloys  

Microsoft Academic Search

A laboratory-scale electromagnetic stirrer was designed, constructed and tested on two aluminium-silicon alloys with silicon contents of seven and twenty mass per cent. The effect of stirring intensity on the structure of the hypoeutectic alloy was studied and also thermal analysis was performed. For the case of the hypereutectic alloy, the distribution of silicon was determined. The results demonstrate that

D. A. Currey; C. A. Pickles

1988-01-01

331

Characterization of brazing alloys with stainless steels  

Microsoft Academic Search

To simulate braze joints, qualitative x-ray mapping of the elemental ; interactions between brazing alloys and two common types of stainless steels was ; performed via the electron microprobe. In general both steels, Types 304L and 21-; 6-9, react with a particular brazing alloy in a similar manner, the exceptions ; being the gold--copper brazing alloys which show deeper penetration

D. H. Riefenberg; J. H. Doyle; R. F. Hillyer; W. S. Bennett

1975-01-01

332

Alloy rotary kilns for hazardous waste disposal  

Microsoft Academic Search

The major conclusions of the study of rotary kilns for processing abrasive, energetic or corrosive hazardous wastes are: Alloy kilns are preferable to smaller refractory lined kilns for abrasive and\\/or explosive feed materials. Alloy construction and bolted sections make alloy kilns transportable; a pyrolysis operating mode can reduce the equipment size for wastes with a high energy release rate. However,

J. V. Del Bene; J. K. Shah; E. F. Colburn

1987-01-01

333

Welding high-strength aluminum alloys  

NASA Technical Reports Server (NTRS)

Handbook has been published which integrates results of 19 research programs involving welding of high-strength aluminum alloys. Book introduces metallurgy and properties of aluminum alloys by discussing commercial alloys and heat treatments. Several current welding processes are reviewed such as gas tungsten-arc welding and gas metal-arc welding.

Parks, P. G.; Hoppes, R. V.; Hasemeyer, E. A.; Masubuchi, K.

1974-01-01

334

UML2Alloy: A Challenging Model Transformation  

E-print Network

UML2Alloy: A Challenging Model Transformation Kyriakos Anastasakis1 , Behzad Bordbar1 , Geri Georg2,iray]@cs.colostate.edu Abstract. Alloy is a formal language, which has been applied to mod- elling of systems in a wide range of application domains. It is supported by Alloy Analyzer, a tool, which allows fully automated analysis

Bordbar, Behzad

335

HIGHLY DISPERSED ALLOY CATHODE CATALYST FOR DURABILITY  

E-print Network

HIGHLY DISPERSED ALLOY CATHODE CATALYST FOR DURABILITY T. D. Jarvi UTC Power Corporation This presentation does not contain any proprietary or confidential information #12;HIGHLY DISPERSED ALLOY CATALYSTVRHE (IR-Free) 720 A/cm2 Cost $8/kW #12;HIGHLY DISPERSED ALLOY CATALYST CurrentStateofArtcathodes (e

336

Fatigue crack propagation in aerospace aluminum alloys  

Microsoft Academic Search

This article reviews fracture mechanics-based, damage tolerant characterizations and predictions of fatigue crack growth in aerospace aluminum alloys. The results of laboratory experimentation and micromechanical modeling are summarized in the areas of 1) the wide range crack growth rate response of conventional aluminum alloys, 2) fatigue crack closure, 3) the fatigue behavior of advanced monolithic aluminum alloys and metal matrix

Richard P. Gangloff; Robert S. Piascik; Dennis L. Dicus; James C. Newman Jr.

1994-01-01

337

Environmental behavior of beta titanium alloys  

Microsoft Academic Search

Stemming from their unique combination of elevated strength, low density, and good overall corrosion resistance, beta titanium alloys have become attractive candidate materials for critical, high-stress components in corrosive services. An overview of the comparative corrosion resistance of beta alloys to conventional alpha and alpha\\/beta titanium alloys in common industrial and aerospace service environments generally reveals attractive behavior depending on

Schutz

1994-01-01

338

Mechanically alloyed metal hydride systems  

NASA Astrophysics Data System (ADS)

Mechanosynthesis of metal hydrides is a new field in which important progress has been reported. In this paper, we present recent developments in mechanosynthesis of magnesium-based hydrides for storage applications. The effect of intense milling on magnesium and magnesium hydrides is presented. The influence of various additives on hydrogen-sorption properties is discussed with special emphasis on nanocomposite MgH2+5 at.%V, where hydrogen-storage characteristics, cycling properties and the mechanism of hydrogen desorption are presented. The production of novel nanocrystalline porous structures by mechanical alloying followed by a leaching technique is discussed. Hot ball-milling, as a new method for rapid synthesis of alloys, is also presented. Finally, two other methods of production of metal hydrides are discussed. One is reactive milling where metal hydrides are synthesized by mechanical alloying under hydrogen pressure, while the other is milling elemental hydrides to produce complex hydrides.

Huot, J.; Liang, G.; Schulz, R.

2001-04-01

339

Diffusion phase transitions in alloys  

NASA Astrophysics Data System (ADS)

We present a critical analysis of research on the thermodynamics, kinetics, and morphology of diffusion phase transitions in alloys. We show that diffusion phase transitions are mainly driven by the chemical potential difference due to a change in the sign of the chemical interaction among the component atoms. We explain how the sign of the chemical interaction energy can be obtained from experimental measurements. Examples are given to illustrate the kinetics and morphology of the ordering-separation phase transition in Ni- and Co-based alloys. We show how introducing the concept of the ordering-separation phase transition may affect our thinking in this area.

Ustinovshchikov, Yu I.

2014-07-01

340

Imparting passivity to vapor deposited magnesium alloys  

NASA Astrophysics Data System (ADS)

Magnesium has the lowest density of all structural metals. Utilization of low density materials is advantageous from a design standpoint, because lower weight translates into improved performance of engineered products (i.e., notebook computers are more portable, vehicles achieve better gas mileage, and aircraft can carry more payload). Despite their low density and high strength to weight ratio, however, the widespread implementation of magnesium alloys is currently hindered by their relatively poor corrosion resistance. The objective of this research dissertation is to develop a scientific basis for the creation of a corrosion resistant magnesium alloy. The corrosion resistance of magnesium alloys is affected by several interrelated factors. Among these are alloying, microstructure, impurities, galvanic corrosion effects, and service conditions, among others. Alloying and modification of the microstructure are primary approaches to controlling corrosion. Furthermore, nonequilibrium alloying of magnesium via physical vapor deposition allows for the formation of single-phase magnesium alloys with supersaturated concentrations of passivity-enhancing elements. The microstructure and surface morphology is also modifiable during physical vapor deposition through the variation of evaporation power, pressure, temperature, ion bombardment, and the source-to-substrate distance. Aluminum, titanium, yttrium, and zirconium were initially chosen as candidates likely to impart passivity on vapor deposited magnesium alloys. Prior to this research, alloys of this type have never before been produced, much less studied. All of these metals were observed to afford some degree of corrosion resistance to magnesium. Due to the especially promising results from nonequilibrium alloying of magnesium with yttrium and titanium, the ternary magnesium-yttrium-titanium system was investigated in depth. While all of the alloys are lustrous, surface morphology is observed under the scanning electron microscope. The corrosion rate of the nonequilibrium sputtered alloys, as determined by polarization resistance, is significantly reduced compared to the most corrosion resistant commercial magnesium alloys. The open circuit potentials of the sputter deposited alloys are significantly more noble compared to commercial, equilibrium phase magnesium alloys. Galvanic corrosion susceptibility has also been considerably reduced. Nonequilibrium magnesium-yttrium-titanium alloys have been shown to achieve passivity autonomously by alteration of the composition chemistry of the surface oxide/hydroxide layer. Self-healing properties are also evident, as corrosion propagation can be arrested after initial pitting of the material. A clear relationship exists between the corrosion resistance of sputter vapor deposited magnesium alloys and the amount of ion bombardment incurred by the alloy during deposition. Argon pressure, the distance between the source and the substrate, and alloy morphology play important roles in determining the ability of the alloy to develop a passive film. Thermal effects, both during and after alloy deposition, alter the stress state of the alloys, precipitation of second phases, and the mechanical stability of the passive film. An optimal thermal treatment has been developed in order to maximize the corrosion resistance of the magnesium-yttrium-titanium alloys. The significance of the results includes the acquisition of electrochemical data for these novel materials, as well as expanding the utilization of magnesium alloys by the improvement in their corrosion resistance. The magnesium alloys developed in this work are more corrosion resistant than any commercial magnesium alloy. Structural components comprised of these alloys would therefore exhibit unprecedented corrosion performance. Coatings of these alloys on magnesium components would provide a corrosion resistant yet galvanically-compatible coating. The broad impact of these contributions is that these new low-density, corrosion resistant magnesium alloys can be used to produce engine

Wolfe, Ryan C.

341

Phase transformation of Mg-Fe alloys  

SciTech Connect

An Mg-Fe alloy system prepared through mechanical alloying (MA) was structurally analyzed. MA can produce single-phase bcc alloys using Mg concentrations up to about 15 mol %. Use of conventional average structure analysis and x-ray pair-distribution function method enabled the long-range and short-range order structures of the Mg-Fe alloys to be bridged. The substituted Mg atoms were randomly arranged in the low-Mg composition but started to have an order structure. The partially ordered Mg-Fe alloy undergoes an austenitic (cubic) to martensitic (orthorhombic) phase change, as increasing Mg composition.

Yoneda, Yasuhiro [Synchrotron Radiation Research Unit, Japan Atomic Energy Agency, 1-1-1 Kouto, Sayo-cho Sayo-gun, Hyogo 679-5148 (Japan); Abe, Hiroshi; Ohshima, Takeshi [Department of Material development, Japan Atomic Energy Agency, 1233 Watanuki, Takasaki, Gunma 370-1292 (Japan); Uchida, Hirohisa [Department of Applied Physics, Graduate and Undergraduate Schools of Engineering, Tokai University, 1117 Kitakaname, Hiratsuka, Kanagawa 259-1292 (Japan)

2010-05-15

342

Alloy softening in binary iron solid solutions  

NASA Technical Reports Server (NTRS)

An investigation was conducted to determine softening and hardening behavior in 19 binary iron-alloy systems. Microhardness tests were conducted at four temperatures in the range 77 to 411 K. Alloy softening was exhibited by 17 of the 19 alloy systems. Alloy softening observed in 15 of the alloy systems was attributed to an intrinsic mechanism, believed to be lowering of the Peierls (lattice friction) stress. Softening and hardening rates could be correlated with the atomic radius ratio of solute to iron. Softening observed in two other systems was attributed to an extrinsic mechanism, believed to be associated with scavenging of interstitial impurities.

Stephens, J. R.; Witzke, W. R.

1976-01-01

343

Protective claddings for high strength chromium alloys  

NASA Technical Reports Server (NTRS)

The application of a Cr-Y-Hf-Th alloy as a protective cladding for a high strength chromium alloy was investigated for its effectiveness in inhibiting nitrogen embrittlement of a core alloy. Cladding was accomplished by a combination of hot gas pressure bonding and roll cladding techniques. Based on bend DBTT, the cladding alloy was effective in inhibiting nitrogen embrittlement of the chromium core alloy for up to 720 ks (200hours) in air at 1422 K (2100 F). A significant increase in the bend DBTT occurred with longer time exposures at 1422 K or short time exposures at 1589 K (2400 F).

Collins, J. F.

1971-01-01

344

Semiempirical Analysis of Surface Alloy Formation  

NASA Technical Reports Server (NTRS)

The BFS method for alloys is applied to the study of surface alloy formation. This method was previously used to examine the experimental STM observation of surface alloying of Au on Ni(110) for low Au coverages by means of a numerical simulation. In this work, we extend the study to include other cases of surface alloying for immiscible as well as miscible metals. All binary combinations of Ni, Au, Cu, and Al are considered and the simulation results are compared to experiment when data is available. The driving mechanisms of surface alloy formation are then discussed in terms of the BFS method and the available results.

Bozzolo, Guillermo; Ferrante, John; Ibanez-Meier, Rodrigo

1995-01-01

345

High-alloy materials for offshore applications  

SciTech Connect

High-alloy materials possessing good corrosion resistance in hot, sour brines are being seriously considered for offshore applications. These alloys are available in a wide range of strength levels which can be attained by the methods of cold working or precipitation hardening. Results of testing INCONEL alloys 625 and 718 and INCOLOY alloys 825 and 925 for resistance to general corrosion, hydrogen embrittlement, and stress-corrosion cracking (SCC) are presented. This paper also contrasts the range of mechanical properties available in precipitation-hardened materials with properties of cold-worked alloys.

Lemke, T.F.; Harris, J.A.

1983-05-01

346

Creep Behavior of Hydrogenated Zirconium Alloys  

NASA Astrophysics Data System (ADS)

Zirconium (Zr) alloys are the primary structural materials of most water reactors. Creep is considered to be one of the important degradation mechanisms of Zr alloys during reactor operating and repository conditions. Zr alloys pick up hydrogen (H2) during their service from the coolant water. Hydrogen can be present in solid solution or precipitated hydride form in Zr alloys depending upon the temperature and concentration. This study reviews the effect of hydrogen on creep behavior of Zr alloys used in the water reactors.

Sarkar, A.; Boopathy, K.; Eapen, J.; Murty, K. L.

2014-10-01

347

Fabrication and characterization of GaSb based thermophotovoltaic cells using Zn diffusion from a doped spin-on glass source  

SciTech Connect

The GaInSb material system is attractive for application in thermophotovoltaic (TPV) cells since its band gap can be tuned to match the radiation of the emitter. At present, most of the TPV cells are fabricated using epitaxial layers and hence are expensive. To reduce the cost, Zn diffusion using elemental vapors in a semi-closed diffusion system is being pursued by several laboratories. In this paper, the authors present studies carried out on Zn diffusion into n-type (Te-doped) GaSb substrates in an open tube diffusion furnace. The dopant precursor was a 2,000 {angstrom} thick, zinc doped spin-on glass. The diffusion was carried out at temperatures ranging from 550 to 600 C, for times from 1 to 10 hours. The diffused layers were characterized by Hall measurements using step-and-repeat etching by anodic oxidation, secondary ion mass spectrometry (SIMS) measurements and TPV device fabrication. For diffusion carried out at 600 C, the junction depth was 0.3 {micro}m, and the hole concentration near the surface was 5 {times} 10{sup 19}/cm{sup 3}. The external quantum efficiency, measured without any anti-reflection coating, of the TPV cells fabricated using mesa-etching had a maximum value of 38%. Masked diffusion was also carried out by opening windows in a Si{sub 3}N{sub 4} coated, GaSb wafer. TPV cells fabricated on these structures had similar quantum efficiency, but lower dark current.

Dakshinamurthy, S.; Shetty, S.; Bhat, I.; Hitchcock, C.; Gutmann, R. [Rensselaer Polytechnic Inst., Troy, NY (United States); Charache, G.; Freeman, M. [Lockheed Martin Corp., Schenectady, NY (United States)

1998-06-01

348

Eutectic nucleation in Al-Si alloys  

SciTech Connect

In addition to a change in silicon morphology, modification of aluminium-silicon alloys with strontium or sodium increases the size of the eutectic grains. To determine the mechanism responsible, eutectic solidification in commercial purity and ultra-high purity aluminium-silicon alloys, with and without strontium additions, was examined by a quenching technique. In the commercial unmodified alloy, nucleation was prolific while in the high-purity unmodified alloy few eutectic grains nucleated. The addition of strontium to the commercial alloy reduced the number of eutectic grains that nucleated. Addition of strontium to the high-purity alloy did not significantly alter nucleation. It is concluded that commercial purity alloys contain a large number of potent nuclei that are susceptible to poisoning by impurity modification. The flake-to-fibre transition that occurs with impurity modification is shown to be independent of any change in eutectic nucleation mode and frequency.

McDonald, Stuart D.; Nogita, Kazuhiro; Dahle, Arne K

2004-08-16

349

Fractal characteristics of dendrite in aluminum alloys  

NASA Astrophysics Data System (ADS)

The fractal dimensions of dendrites in Al-Si and Al-Cu binary alloys were measured under furnace cooling and casting experiments. The fractal dimension of the Al-Si alloy increased from 1.275 to 1.495 along with increase in Si content. The fractal dimension of the Al-Cu alloy increased from 1.139 to 1.486 along with increase in Cu content. The fractal dimension of the binary alloys also increased with increase in cooling rate during solidification. Phase-field simulations for the evolution of the dendrites in the binary aluminium alloys were carried out and a same tendency as the experimental results was obtained. The permeability of an Al-5mass%Si alloy was estimated from the measured fractal dimension of an experimentally observed dendrite structure. The estimated permeability agreed well with reported permeability of an Al-Si alloy.

Ohsasa, K.; Katsumi, T.; Sugawara, R.; Natsume, Y.

2012-07-01

350

Environmental fatigue in aluminum-lithium alloys  

NASA Technical Reports Server (NTRS)

Aluminum-lithium alloys exhibit similar environmental fatigue crack growth characteristics compared to conventional 2000 series alloys and are more resistant to environmental fatigue compared to 7000 series alloys. The superior fatigue crack growth behavior of Al-Li alloys 2090, 2091, 8090, and 8091 is due to crack closure caused by tortuous crack path morphology and crack surface corrosion products. At high R and reduced closure, chemical environment effects are pronounced resulting in accelerated near threshold da/dN. The beneficial effects of crack closure are minimized for small cracks resulting in rapid growth rates. Limited data suggest that the 'chemically small crack' effect, observed in other alloy system, is not pronounced in Al-Li alloys. Modeling of environmental fatigue in Al-Li-Cu alloys related accelerated fatigue crack growth in moist air and salt water to hydrogen embrittlement.

Piascik, Robert S.

1992-01-01

351

Environmental fatigue in aluminum-lithium alloys  

NASA Astrophysics Data System (ADS)

Aluminum-lithium alloys exhibit similar environmental fatigue crack growth characteristics compared to conventional 2000 series alloys and are more resistant to environmental fatigue compared to 7000 series alloys. The superior fatigue crack growth behavior of Al-Li alloys 2090, 2091, 8090, and 8091 is due to crack closure caused by tortuous crack path morphology and crack surface corrosion products. At high R and reduced closure, chemical environment effects are pronounced resulting in accelerated near threshold da/dN. The beneficial effects of crack closure are minimized for small cracks resulting in rapid growth rates. Limited data suggest that the 'chemically small crack' effect, observed in other alloy system, is not pronounced in Al-Li alloys. Modeling of environmental fatigue in Al-Li-Cu alloys related accelerated fatigue crack growth in moist air and salt water to hydrogen embrittlement.

Piascik, Robert S.

1992-07-01

352

Alcoa: the alloy constraint analyzer  

Microsoft Academic Search

Alcoa is a tool for analyzing object models. It has a range of uses. At one end, it can act as a support tool for object model diagrams, checking for consistency of multiplicities and generating sample snapshots. At the other end, it embodies a lightweight formal method in which subtle properties of behaviour can be investigated.Alcoa's input language, Alloy, is

Daniel Jackson; Ian Schechter; Hya Shlyahter

2000-01-01

353

Alcoa: the Alloy constraint analyzer  

Microsoft Academic Search

Alcoa is a tool for analyzing object models. It has a range of uses. At one end, it can act as a support tool for object model diagrams, checking for consistency of multiplicities and generating sample snapshots. At the other end, it embodies a lightweight formal method in which subtle properties of behaviour can be investigated. Alcoa's input language, Alloy,

Daniel Jackson; Ian Schechter; Ilya Shlyakhter

2000-01-01

354

Dispersion-strengthened chromium alloy  

NASA Technical Reports Server (NTRS)

Finely divided powder mixture produced by vapor deposition of CR on small ThO2 particles was hot pressed or pressure bonded. Resulting alloy has lower ductile-to-brittle transition temperature than pure chromium, and high strength and oxidation resistance at elevated temperatures, both in as-rolled condition and after annealing.

Blocker, J. M., Jr.; Veigel, N. D.

1972-01-01

355

Machining of aerospace titanium alloys  

Microsoft Academic Search

The performance of PCBN (AMBORITE*) and PCD (SYNDITE) has been compared with that of coated tungsten carbide tool currently being used to machine titanium aerospace alloy. Tests confirm that SYNDITE gives a better surface finish, longer tool life and more manageable swarf than other tools. In addition, the “quick-stop” technique establishes that, for all three cutting tools, a layer is

Farhad Nabhani

2001-01-01

356

Welding of TZM molybdenum alloy  

Microsoft Academic Search

Molybdenum and TZM alloy are not too difficult to form or weld if the proper procedures are employed. Consistently good welds can be obtained by controlling the area of heating by ensuring full penetration of the welded pieces and by reducing the stresses. A large percentage of the problems incurred in welding TZM can be corrected by good weld joint

Hanks

1970-01-01

357

Strainhardening and softening of vanadium-alloyed ferrite  

Microsoft Academic Search

This investigation into the softening of alloyed ferrlte was concerned with the changes in mechanical properties and microstructure of alloys. G. Tammann [1] alloyed solid solutions with small amounts of alloy elements producing equiatomic concentrations, this permitting a comparison os the effects of various elements in the most correct fashion. Austin in [2, 3] showed that alloy additions ~ncrease the

L. I. Mirkin

1959-01-01

358

CORROSION OF HIGH-TEMPERATURE ALLOYS  

SciTech Connect

Five alloys were tested in the presence of water vapor and water vapor with HCl for 1000 hours using simulated combustion gas. Samples were removed at intervals during each test and measured for determination of corrosion rates. One sample of each alloy was examined with a SEM after the completion of each test. Cumulative corrosion depths were similar for the superstainless alloys. Corrosion for Alloy TP310 roughly doubled. Corrosion for the enhanced stainless alloys changed dramatically with the addition of chlorine. Corrosion for Alloy RA85H increased threefold, whereas Alloy TP347HFG showed an eightfold increase. SEM examination of the alloys revealed that water vapor alone allowed the formation of chromium oxide protective layers on the superstainless alloys. The enhanced stainless alloys underwent more corrosion due to greater attack of sulfur. Iron-rich oxide layers were more likely to form, which do not provide protection from further corrosion. The addition of chlorine further increased the corrosion because of its ability to diffuse through the oxide layers and react with iron. This resulted in a broken, discontinuous, and loose oxide layer that offered less protection. Niobium, although added to aid in creep strength, was found to be detrimental to corrosion resistance. The niobium tended to be concentrated in nodules and was easily attacked through sulfidation, providing conduits for further corrosion deep into the alloy. The alloys that displayed the best corrosion resistance were those which could produce chromium oxide protective layers. The predicted microstructure of all alloys except Alloy HR3C is the same and provided no further information relating to corrosion resistance. No correlation can be found relating corrosion resistance to the quantity of minor austenite-or ferrite-stabilizing elements. Also, there does not appear to be a correlation between corrosion resistance and the Cr:Ni ratio of the alloy. These alloys were tested for their corrosion resistance alone. Strength and creep tests were not performed. Based only their corrosion resistance, Alloys RA310 and TP310 were shown to be the best suited to resist chlorine in a combustion environment. These alloys produced protective chromium oxide layers, displayed more general rather than localized corrosion, and their additives did not react to provide conduits for further corrosion.

John P. Hurley; John P. Kay

1999-10-01

359

Substitutional alloying and deformation modes in high chromium ferritic alloys  

Microsoft Academic Search

The effect of microalloying additions of between 0.05 and 2 wt pct Ni, Ru, Nb, and Ti on the plastic deformation of alloys\\u000a based on Fe-40 wt pct Cr has been studied. The dislocation sub-structures in the deformed and recovered conditions have been\\u000a characterized for a series of isothermal annealing cycles. Unalloyed Fe-40Cr deforms at room temperature by mixed twinning

I. M. Wolff; A. Ball

1992-01-01

360

First principles theory of disordered alloys and alloy phase stability  

SciTech Connect

These lecture notes review the LDA-KKR-CPA method for treating the electronic structure and energetics of random alloys and the MF-CF and GPM theories of ordering and phase stability built on the LDA- KKR-CPA description of the disordered phase. Section 2 lays out the basic LDA-KKR-CPA theory of random alloys and some applications. Section 3 reviews the progress made in understanding specific ordering phenomena in binary solid solutions base on the MF-CF and GPM theories of ordering and phase stability. Examples are Fermi surface nesting, band filling, off diagonal randomness, charge transfer, size difference or local strain fluctuations, magnetic effects; in each case, an attempt is made to link the ordering and the underlying electronic structure of the disordered phase. Section 4 reviews calculations of electronic structure of {beta}-phase Ni{sub c}Al{sub 1-c} alloys using a version of the LDA-KKR-CPA codes generalized to complex lattices.

Stocks, G.M.; Nicholson, D.M.C.; Shelton, W.A. [and others

1993-06-05

361

Evaluation of zirconium-iron-rhenium alloys as surrogates for a technetium alloy waste form  

E-print Network

Stainless steel – zirconium alloys were developed by the US Department of Energy Laboratories as metallic waste forms for noble metal fission products. This thesis evaluates iron–zirconium–rhenium alloys to establish a technical basis for using...

Mews, Paul Aaron

2009-05-15

362

Effects of Substitutional Alloy Elements in an Fe-10Cr Ferritic Alloy.  

National Technical Information Service (NTIS)

The objective of this effort is to determine the effects of substitutional alloying elements in an Fe-10Cr base composition on microstructural development due to neutron irradiation. The alloying elements selected are of interest in reduced activation app...

D. S. Gelles, W. L. Beems

1984-01-01

363

High nickel, chromium-molybdenum alloys - are some new alloys more corrosion resistant than the old  

SciTech Connect

Within the past decade, several highly corrosion resistant, proprietary alloys have had their patients expire, and have been produced by others who wish to enter this competitive market. As such, research and development began in earnest for really new corrosion resistant alloys which could receive their own patents, and hopefully, premium prices or single source appropriation. Some limited corrosion test results have made these newer alloys appear outstanding. However, these alloys have not yet established a long or impressive track record within the Chemical Process Industry that has been generated by the older alloys over many years of intensive in-plant service. Therefore, a comparative alloy corrosion resistance testing program was performed to evaluate some of these newer alloys versus older alloys in four different acid environments and some aqueous solutions based on sodium chloride-ferric chloride.

Corbett, R.A.; Morrison, W.S.

1988-01-01

364

Corrosion behavior and fatigue of alloy 625, alloy 33 and alloy 31 under conditions of decouplers in automotive exhaust systems  

SciTech Connect

The alloys 625, 31, 33 and in some tests the newly developed alloy 626Si have been investigated with respect to their mechanical properties and their corrosion resistance against alkali salts containing chlorides at temperatures of 550 C, 65O C, 7OO C and 750 C. Concerning strength in the sensitized condition, all alloys are suitable as decoupler materials. The mechanical properties of alloys 625, 626Si and probably 31 indicate adequate manufacturing possibilities of bellows. All alloys investigated suffer accelerated corrosion in the presence of alkali salt containing chlorides at temperatures ranging from 550 C to 750 C. At 750 C alloy 626Si shows the lowest corrosion rate. At 75O C, 7OO C and 650 C no difference between the solution annealed and the sensitized specimens was found. At 55O C, however, the corrosion rate of the alloys 625 and 33 increased significantly, when the material was sensitized prior to corrosion testing. Alloy 31 does not suffer significant corrosion attack at 55O C both in the solution annealed and in the sensitized condition, thus making it a potential cost effective alternative to the more expensive alloy 625 for decoupler applications.

Agarwal, D.C. [Krupp VDM GmbH, Houston, TX (United States); Kloewer, J.; Koehler, M.; Kolb-Telieps, A. [Krupp VDM GmbH, Werdohl (Germany)

1998-12-31

365

Wetting behavior of alternative solder alloys  

SciTech Connect

Recent economic and environmental issues have stimulated interest in solder alloys other than the traditional Sn-Pb eutectic or near eutectic composition. Preliminary evaluations suggest that several of these alloys approach the baseline properties (wetting, mechanical, thermal, and electrical) of the Sn-Pb solders. Final alloy acceptance will require major revisions to existing industrial and military soldering specifications. Bulk alloy and solder joint properties are consequently being investigated to validate their producibility and reliability. The work reported in this paper examines the wetting behavior of several of the more promising commercial alloys on copper substrates. Solder wettability was determined by the meniscometer and wetting balance techniques. The wetting results suggest that several of the alternative solders would satisfy pretinning and surface mount soldering applications. Their use on plated through hole technology might be more difficult since the alloys generally did not spread or flow as well as the 60Sn-40Pb solder.

Hosking, F.M.; Vianco, P.T.; Hernandez, C.L.; Rejent, J.A.

1993-07-01

366

Directionally solidified eutectic alloy gamma-beta  

NASA Technical Reports Server (NTRS)

A pseudobinary eutectic alloy composition was determined by a previously developed bleed-out technique. The directionally solidified eutectic alloy with a composition of Ni-37.4Fe-10.0Cr-9.6Al (in wt%) had tensile strengths decreasing from 1,090 MPa at room temperature to 54 MPa at 1,100 C. The low density, excellent microstructural stability, and oxidation resistance of the alloy during thermal cycling suggest that it might have applicability as a gas turbine vane alloy while its relatively low high temperature strength precludes its use as a blade alloy. A zirconium addition increased the 750 C strength, and a tungsten addition was ineffective. The gamma=beta eutectic alloys appeared to obey a normal freezing relation.

Tewari, S. N.

1977-01-01

367

Alloy Effects on the Gas Nitriding Process  

NASA Astrophysics Data System (ADS)

Alloy elements, such as Al, Cr, V, and Mo, have been used to improve the nitriding performance of steels. In the present work, plain carbon steel AISI 1045 and alloy steel AISI 4140 were selected to compare the nitriding effects of the alloying elements in AISI 4140. Fundamental analysis is carried out by using the "Lehrer-like" diagrams (alloy specific Lehrer diagram and nitriding potential versus nitrogen concentration diagram) and the compound layer growth model to simulate the gas nitriding process. With this method, the fundamental understanding for the alloy effect based on the thermodynamics and kinetics becomes possible. This new method paves the way for the development of new alloy for nitriding.

Yang, M.; Sisson, R. D.

2014-10-01

368

Evaluation of zirconium-iron-rhenium alloys as surrogates for a technetium alloy waste form  

E-print Network

EVALUATION OF ZIRCONIUM-IRON-RHENIUM ALLOYS AS SURROGATES FOR A TECHNETIUM ALLOY WASTE FORM A Thesis by PAUL AARON MEWS Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment... of the requirements for the degree of MASTER OF SCIENCE December 2007 Major Subject: Nuclear Engineering EVALUATION OF ZIRCONIUM-IRON-RHENIUM ALLOYS AS SURROGATES FOR A TECHNETIUM ALLOY WASTE FORM A Thesis by PAUL AARON MEWS Submitted...

Mews, Paul Aaron

2008-10-10

369

Effect of alloying chemistry on the lattice constant of austenitic Fe-Mn-Al-C alloys  

Microsoft Academic Search

Austenitic Fe-Al-Mn-C alloys are developed as a possible substitute for the Ni-Cr stainless steel and have shown some promise as engineering alloys for their high strength, light weight and low cost. A clear composition boundary for single phase austenite has not yet been established in this alloy system. However, the compositions employed for austenitic Fe-Mn-Al-C alloys are generally constrained within

C. M. Chu; H. Huang; P. W. Kao; D. Gan

1994-01-01

370

Microstructural control in lead alloys for storage battery application  

Microsoft Academic Search

The role of alloying and thermomechanical processing in direct microstructural control in lead-base storage battery alloys is reviewed. Strength, corrosion, and electrochemical correlations are discussed for conventional and emerging lead alloy systems.

Jeff Perkins; G. R. Edwards

1975-01-01

371

21 CFR 872.3080 - Mercury and alloy dispenser.  

Code of Federal Regulations, 2011 CFR

...2011-04-01 2011-04-01 false Mercury and alloy dispenser. 872.3080 Section...DEVICES Prosthetic Devices § 872.3080 Mercury and alloy dispenser. (a) Identification. A mercury and alloy dispenser is a device...

2011-04-01

372

21 CFR 872.3080 - Mercury and alloy dispenser.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 2013-04-01 false Mercury and alloy dispenser. 872.3080 Section...DEVICES Prosthetic Devices § 872.3080 Mercury and alloy dispenser. (a) Identification. A mercury and alloy dispenser is a device...

2013-04-01

373

21 CFR 872.3080 - Mercury and alloy dispenser.  

Code of Federal Regulations, 2012 CFR

...2012-04-01 2012-04-01 false Mercury and alloy dispenser. 872.3080 Section...DEVICES Prosthetic Devices § 872.3080 Mercury and alloy dispenser. (a) Identification. A mercury and alloy dispenser is a device...

2012-04-01

374

21 CFR 872.3080 - Mercury and alloy dispenser.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 2010-04-01 false Mercury and alloy dispenser. 872.3080 Section...DEVICES Prosthetic Devices § 872.3080 Mercury and alloy dispenser. (a) Identification. A mercury and alloy dispenser is a device...

2010-04-01

375

21 CFR 872.3080 - Mercury and alloy dispenser.  

...2014-04-01 2014-04-01 false Mercury and alloy dispenser. 872.3080 Section...DEVICES Prosthetic Devices § 872.3080 Mercury and alloy dispenser. (a) Identification. A mercury and alloy dispenser is a device...

2014-04-01

376

Large warm worked, alloy article  

Microsoft Academic Search

A large, austenitic, non-magnetic, stainless steel, alloy article which has been significantly warm worked between about 1500° F. and 1650° F. but not subsequently annealed, which has a 0.2% yield strength of at least about 90 ksi, and which, when formed into a U-bend, does not undergo stress corrosion cracking within about 700 hours in boiling saturated aqueous sodium chloride

T. A. DeBold; J. H. Magee

1985-01-01

377

Mechanical alloying of IN738  

Microsoft Academic Search

Mechanical alloying has been applied to produce a dispersion-strengthened superalloy IN-738 containing 1.5 wt pct Y2O3. Annealing of extrusion bars above the recrystallization temperature of 1160°C can be described by three stages of recrystallization:finegrain;\\u000a isotropic coarse-grain; and fibrous coarse grain growth. A maximum grain length of 550 ?m and a maximum grain aspect ratio\\u000a of 4.8 have been obtained for

Gernot H. Gessinger

1976-01-01

378

Mechanical alloying of IN738  

Microsoft Academic Search

Mechanical alloying has been applied to produce a dispersion-strengthened superalloy IN-738 containing 1.5 wt pct Y2O3. Annealing of extrusion bars above the recrystallization temperature of 1160°C can be described by three stages of recrystallization:finegrain; isotropic coarse-grain; and fibrous coarse grain growth. A maximum grain length of 550 mum and a maximum grain aspect ratio of 4.8 have been obtained for

Gernot H. Gessinger

1976-01-01

379

Molybdenum disilicide alloy matrix composite  

DOEpatents

Compositions of matter consisting of matrix materials having silicon carbide dispersed throughout them and methods of making the compositions. A matrix material is an alloy of an intermetallic compound, molybdenum disilicide, and at least one secondary component which is a refractory silicide. The silicon carbide dispersant may be in the form of VLS whiskers, VS whiskers, or submicron powder or a mixture of these forms.

Petrovic, John J. (Los Alamos, NM); Honnell, Richard E. (Los Alamos, NM); Gibbs, W. Scott (Los Alamos, NM)

1991-01-01

380

Molybdenum disilicide alloy matrix composite  

DOEpatents

Compositions of matter consisting of matrix materials having silicon carbide dispersed throughout them and methods of making the compositions are disclosed. A matrix material is an alloy of an intermetallic compound, molybdenum disilicide, and at least one secondary component which is a refractory silicide. The silicon carbide dispersant may be in the form of VLS whiskers, VS whiskers, or submicron powder or a mixture of these forms. 3 figures.

Petrovic, J.J.; Honnell, R.E.; Gibbs, W.S.

1991-12-03

381

Molybdenum disilicide alloy matrix composite  

DOEpatents

Compositions of matter consisting of matrix matrials having silicon carbide dispersed throughout them and methods of making the compositions. A matrix material is an alloy of an intermetallic compound, molybdenum disilicide, and at least one secondary component which is a refractory silicide. The silicon carbide dispersant may be in the form of VLS whiskers, VS whiskers, or submicron powder or a mixture of these forms.

Petrovic, John J. (Los Alamos, NM); Honnell, Richard E. (Los Alamos, NM); Gibbs, W. Scott (Los Alamos, NM)

1990-01-01

382

Structure of liquid aluminium-silicon alloys  

Microsoft Academic Search

The Kumar-Samarin technique of centrifuging was adopted to study the structure of aluminium-silicon alloys in terms of the concept of the existence of clusters in liquid state. The investigation shows that in hypo-eutectic alloys the clusters are denser than the monatomic matrix whilst in hyper-eutectic alloys they are lighter. It is suggested that this difference in the distribution of silicon

Manjit Singh; Rajendra Kumar

1973-01-01

383

Magnetic entropy in nanocomposite binary gadolinium alloys  

Microsoft Academic Search

Investigation on magnetocaloric effects, magnetic entropy, Curie temperature, and specific heat of nanocomposite binary gadolinium alloys Gd–Tb, Gd–Zn, and Gd–Y has been carried out with an applied magnetic field of 1 T and in a temperature range of 233–313 K. Compared with the respective bulk alloys, the as-prepared nanocomposite alloys were found to have higher specific heat and lower Curie

Yuanzhi Shao; Jinxiu Zhang; J. K. L. Lai; C. H. Shek

1996-01-01

384

New Zinc alloys for semisolid applications  

Microsoft Academic Search

A new alloy for fashion products, alternative to traditional die-cast Zamak and hot-forged brass, was designed. The attention\\u000a was focused on zinc-based alloy and different chemical compositions were investigated, mainly containing aluminum and copper\\u000a as alloying elements, in order to obtain a proper material also for semisolid applications. The semisolid microstructure was\\u000a obtained by ultrasound treatment of the liquid metal.

A. Pola; R. Roberti; L. Montesano

2010-01-01

385

High toughness-high strength iron alloy  

NASA Technical Reports Server (NTRS)

An iron alloy is provided which exhibits strength and toughness characteristics at cryogenic temperatures. The alloy consists essentially of about 10 to 16 percent by weight nickel, about 0.1 to 1.0 percent by weight aluminum, and 0 to about 3 percent by weight copper, with the balance being essentially iron. The iron alloy is produced by a process which includes cold rolling at room temperature and subsequent heat treatment.

Stephens, J. R.; Witzke, W. R. (inventors)

1980-01-01

386

Graded coatings for metallic implant alloys  

Microsoft Academic Search

Graded glass and glass-hydroxyapatite coatings on Ti-based and Co-Cr alloys have been prepared using a simple enameling technique. The composition of the glasses has been tailored to match the thermal expansion of the alloys. By controlling the firing time, and temperature, it has been possible to control the reactivity between the glass and the alloy and to fabricate coatings (25

Eduardo Saiz; Antoni P. Tomsia; Shigeru Fujino; Jose M. Gomez-Vega

2002-01-01

387

Modeling Asymmetric Rolling Process of Mg alloys  

SciTech Connect

Asymmetric deformation during rolling can arise in various ways: difference in the radii, speeds, frictions of the top and bottom rolls. Asymmetric warm rolling processes of magnesium alloys were modeled using a lagrangian incremental approach. A constitutive equation representing flow behaviors of AZ31 magnesium alloys during warm deformation was implemented to the modeling. Various roll speed ratios were introduced to investigate deformation behaviors of the magnesium alloys. Bending and texturing of the strips were examined.

Cho, Jaehyung; Kim, Hyung-Wuk; Kang, Suk-Bong [Korea Institute of Materials Science, 66 Sangnam-dong, Changwon-city, Kyungnam, 641-010 (Korea, Republic of)

2010-06-15

388

Reduction in Defect Content in ODS Alloys  

Microsoft Academic Search

In order to develop FeCrAl-based ODS alloy tubing with the coarse, high aspect ratio, appropriately oriented grain structures likely to deliver enhanced high temperature (11000C) hoop creep strength compared to conventionally formed ODS alloy tubing, flow forming techniques were explored in a European funded programme. The evolution of microstructure in PM2000 alloy tubing formed by warm flow forming techniques has

A. R. Jones; J. Ritherdon; D. J. Prior

2003-01-01

389

Advanced powder metallurgy aluminum alloys and composites  

NASA Technical Reports Server (NTRS)

The differences between powder and ingot metallurgy processing of aluminum alloys are outlined. The potential payoff in the use of advanced powder metallurgy (PM) aluminum alloys in future transport aircraft is indicated. The national program to bring this technology to commercial fruition and the NASA Langley Research Center role in this program are briefly outlined. Some initial results of research in 2000-series PM alloys and composites that highlight the property improvements possible are given.

Lisagor, W. B.; Stein, B. A.

1982-01-01

390

Review of alloy and process development of TiAl alloys  

Microsoft Academic Search

The improved understanding of the factors that control microstructure and properties of TiAl alloys is reviewed together with current work aimed at developing both wrought and cast products. It is suggested that the choice of alloy composition is perhaps far simpler than the complex literature would suggest and the factors that underlie alloy choice will be explained. These factors include

Xinhua Wu

2006-01-01

391

Controlling quality of ferroalloys and alloying additives in the manufacture of nickel alloys for nuclear applications  

Microsoft Academic Search

Nickel alloys supplied to the nuclear industry must meet strict requirements for quality and traceability of constituents. Ensuring that end products meet those requirements involves careful control of the raw materials used in melting the alloys. Especially important is an effective system of quality control for purchasing and consuming ferroalloys and alloying additives. Development and operation of such a system

Stryker

1981-01-01

392

[Composition and morphology of oxides on porcelain fused to Ni-Cr alloys. Be containing alloys].  

PubMed

Bonding strength between porcelain and Ni-Cr alloy for the porcelain fused-to metal crown in which Be is contained in the alloy is known to be higher than those in which Be is not contained. Since, bonding between porcelain and alloy is the reaction of oxides and porcelain, the bonding is thought to be influenced by the quality the oxides film which forms on the alloy surface. The purpose of this study was to determine the composition and morphology of the oxides formed on both Be containing and non-Be contained Ni-Cr alloys. The oxides analysis was done using an EPMA and Auger analysis. Also, the Porcelain/Ni-Cr alloy interface was observed by a scanning electron microscope (SEM). The following results are indicated from this investigation: 1. The oxides from the alloys not containing Be are corundum type Cr2O3 and spinel type NiCr2O4. These oxide layers are uniform, thick and porous and the adhesion to alloy is poor. 2. The oxides from alloy containing Be is BeO only. The BeO is uniform, thin and condensed. The adhesion to the alloy is good. 3. The oxide layer formed when the porcelain is fused to alloy containing Be is thin (1 micron average) and has good adhesion to alloy. 4. Be is selectively oxidized and controlled the form of Cr2O3 and NiO. PMID:2700282

Watanabe, T

1989-06-01

393

Magnetic Alloys in Nanoscale Biomaterials  

SciTech Connect

Fe-Co composition gradient and Fe-Pt multilayer alloy films were tested as catalysts for growing vertically aligned carbon nanofibers (VACNFs) by plasma-enhanced chemical vapor deposition (PECVD). The Fe-Co film yielded nanofibers with alloy tips in a wide compositional range varying from 8.15 pct Fe at the Co-rich end to 46.29 pct Fe in the middle of the wafer as determined by energy-dispersive X-ray analysis. Two Fe-Co cubic phases (SG Pm3m, Pm{bar 3}m) were identified by preliminary X-ray diffraction (XRD) measurements. Magnetic measurements showed a substantially greater hysteresis loop area and coercivity in Fe-Co catalyst nanoparticles as compared to the as deposited Fe-Co film. The Fe-Pt film did not break into FePt alloy nanoparticles under the applied processing parameters and thus the utility of FePt as a VACNF catalyst has been inconclusive.

Leventouri, T. H. [Florida Atlantic University; Melechko, Anatoli Vasilievich [ORNL; Sorge, Korey D. [Florida Atlantic University; Klein, Kate L [ORNL; Fowlkes, Jason Davidson [ORNL; Rack, P. D. [University of Tennessee, Knoxville (UTK); Anderson, Ian M [ORNL; Thompson, James R [ORNL; McKnight, Timothy E [ORNL; Simpson, Michael L [ORNL

2006-01-01

394

Rotary actuator utilizing a shape memory alloy  

SciTech Connect

An apparatus is described comprising; (a) rotary accumulator means for accumulating a length of a shape memory alloy wire; (b) the shape memory alloy wire attached at one end to a point fixed with respect to the rotary accumulator means and attached at a second end to the rotary accumulator means; (c) biasing means for biasing the rotary accumulator means to a first position; and (d) means for heating the shape memory alloy wire to cause the shape memory alloy wire to contract, thereby rotating the rotary accumulator means from the first position to a second position.

Bloch, J.T.

1988-08-09

395

Surface alloying of silicon into aluminum substrate.  

SciTech Connect

Aluminum alloys that are easily castable tend to have lower silicon content and hence lower wear resistance. The use of laser surface alloying to improve the surface wear resistance of 319 and 320 aluminum alloys was examined. A silicon layer was painted onto the surface to be treated. A high power pulsed Nd:YAG laser with fiberoptic beam delivery was used to carry out the laser surface treatment to enhance the silicon content. Process parameters were varied to minimize the surface roughness from overlap of the laser beam treatment. The surface-alloyed layer was characterized and the silicon content was determined.

Xu, Z.

1998-10-28

396

Irradiation-assisted stress corrosion cracking in HTH Alloy X-750 and Alloy 625  

SciTech Connect

In-reactor testing of bolt-loaded compact tension specimens was performed in 360 C water to determine the irradiation-assisted stress corrosion cracking (IASCC) behavior of HTH Alloy X-750 and direct-aged Alloy 625. New data confirm previous results showing that high irradiation levels reduce SCC resistance in Alloy X-750. Heat-to-heat variability correlates with boron content, with low boron heats showing improved IASCC properties. Alloy 625 is resistant to IASCC, as no cracking was observed in any Alloy 625 specimens. Microstructural, microchemical and deformation studies were performed to characterize the mechanisms responsible for IASCC in Alloy X-750 and the lack of an effect in Alloy 625. The mechanisms under investigation are: boron transmutation effects, radiation-induced changes in microstructure and deformation characteristics, and radiation-induced segregation. Irradiation of Alloy X-750 caused significant strengthening and ductility loss that was associated with the formation of cavities and dislocation loops. High irradiation levels did not cause significant segregation of alloying or trace elements in Alloy X-750. Irradiation of Alloy 625 resulted in the formation of small dislocation loops and a fine body-centered-orthorhombic phase. The strengthening due to the loops and precipitates was apparently offset by a partial dissolution of {gamma}{double_prime} precipitates, as Alloy 625 showed no irradiation-induced strengthening or ductility loss. In the nonirradiated condition, an IASCC susceptible HTH heat containing 28 ppm B showed grain boundary segregation of boron, whereas a nonsusceptible HTH heat containing 2 ppm B and Alloy 625 with 20 ppm B did not show significant boron segregation. Transmutation of boron to helium at grain boundaries, coupled with matrix strengthening, is believed to be responsible for IASCC in Alloy X-750, and the absence of these two effects results in the superior IASCC resistance displayed by Alloy 625.

Bajaj, R.; Mills, W.J.; Lebo, M.R.; Hyatt, B.Z.; Burke, M.G. [Westinghouse Electric Corp., West Mifflin, PA (United States). Bettis Atomic Power Lab.

1995-12-31

397

Effect of a microstructure and surface hydrogen alloying of a VT6 alloy on diffusion welding  

NASA Astrophysics Data System (ADS)

The effect of a structural type (lamellar, fine, gradient) and additional surface alloying with hydrogen on the diffusion bonding of titanium alloy VT6 samples is studied. It is shown that the surface alloying of VT6 alloy parts with hydrogen allows one to decrease the diffusion welding temperature by 50-100°C, to obtain high-quality pore-free bonding, and to remove the "structural" boundary between materials to be welded that usually forms during welding of titanium alloys with a lamellar structure.

Senkevich, K. S.; Skvortsova, S. V.; Kudelina, I. M.; Knyazev, M. I.; Zasypkin, V. V.

2014-01-01

398

Role of alloying elements in adhesive transfer and friction of copper-base alloys  

NASA Technical Reports Server (NTRS)

Sliding friction experiments were conducted in a vacuum with binary-copper alloy riders sliding against a conventional bearing-steel surface with normal residual oxides present. The binary alloys contained 1 atomic percent of various alloying elements. Auger spectroscopy analysis was used to monitor the adhesive transfer of the copper alloys to the bearing-steel surface. A relation was found to exist between adhesive transfer and the reaction potential and free energy of formation of the alloying element in the copper. The more chemically active the element and the more stable its oxide, the greater was the adhesive transfer and wear of the copper alloy. Transfer occurred in all the alloys except copper-gold after relatively few (25) passes across the steel surface.

Buckley, D. H.

1978-01-01

399

Scanning and transmission electron microscopy microstructure characterization of mechanically alloyed Nb-Ti-Al alloys.  

PubMed

Results are presented of an investigation of the microstructure development during mechanical alloying and following consolidation of an Nb15Ti15Al alloy. The alloy was synthesized from elemental as well as pre-alloyed powders. The microstructure of this material was examined by transmission electron microscopy, scanning electron microscopy and X-ray diffraction. The use of pre-alloyed TiAl powder for synthesis of the Nb15Ti15Al alloy meant that a much shorter time was required to complete the mechanical alloying process compared with the synthesis of elemental powders. The investigation indicates that three phases were present in the consolidated materials: the Nb solid solution, the Nb(3)Al intermetallic phase and the dispersoid. PMID:17100907

Rozmus, Magdalena; Blicharski, Marek; Dymek, Stanis?aw

2006-10-01

400

Zirconium Alloys in Nuclear Power Plants  

Microsoft Academic Search

The use of zirconium alloys for nuclear fuel and reactor internals in nuclear reactors is reviewed, with special attention to the mechanisms that can limit fuel burnup extensions in light water reactors, such as corrosion and hydriding and irradiation growth and creep. Recent techniques for studying these processes open the possibility that they can be understood mechanistically such that alloys

A. T. Motta

401

Electron Density of States of Dilute Alloys.  

National Technical Information Service (NTIS)

The change in the electron density of states with dilute alloying is directly related to the shielding of the added impurities. If there is no volume change on alloying, the change in rho (E), the density of states at energy E, is proportional to the exce...

E. A. Stern

1969-01-01

402

Study of stress corrosion in aluminum alloys  

NASA Technical Reports Server (NTRS)

Mechanism of the stress corrosion cracking of high-strength aluminum alloys was investigated using electrochemical, mechanical, and electron microscopic techniques. The feasibility of detecting stress corrosion damage in fabricated aluminum alloy parts by nondestructive testing was investigated using ultrasonic surface waves and eddy currents.

Brummer, S. B.

1967-01-01

403

Progress in High-Entropy Alloys  

SciTech Connect

Strictly speaking, high-entropy alloys (HEAs) refer to single-phase, solid-solution alloys with multiprincipal elements in an equal or a near-equal molar ratio whose configurational entropy is tremendously high. This special topic was organized to reflect the focus and diversity of HEA research topics in the community.

Gao, Michael C.

2013-12-01

404

Atomization of Alloy Constraints Vincent Yeung  

E-print Network

Atomization of Alloy Constraints by Vincent Yeung Submitted to the Department of Electrical modeling language, can be translated into Boolean logic and solved with a SAT solver. Atomization on the performance of atomization on a number of Alloy models; in a majority of the cases, we found a sizable

405

Heats of formation of bcc binary alloys  

NASA Technical Reports Server (NTRS)

The method of Bozzolo, Ferrante and Smith is applied for the calculation of alloy energies for bcc elements. The heat of formation of several alloys is computed with the help of the Connolly-Williams method within the tetrahedron approximation. The dependence of the results on the choice of different sets of ordered structures is discussed.

Bozzolo, Guillermo; Ferrante, John

1992-01-01

406

Glass forming ranges of amorphous alloys  

SciTech Connect

Two main methods of synthesis of amorphous metallic alloys are based on the rapid solidification of molten alloys and on isothermal solid state reactions between pure metals. We discuss recent calculations for the glass forming range for both techniques and we compare the predicted homogeneity ranges of the amorphous phase with experiments. 10 refs., 2 figs.

Schwarz, R.B.

1988-01-01

407

The rheology of a partially solid alloy  

Microsoft Academic Search

The effect of various thermomechanical treatments on the structure and rheological behaviour of Sn-15% Pb alloy in its solidifcation range was investigated using a concentric cylinder viscometer. The apparatus was designed to permit wide ranges of cooling rates up to 25° C min-1 and shear rates up to 750 sec-1. Initially, the alloy was continuously sheared as it cooled from

P. A. Joly; R. Mehrabian

1976-01-01

408

TEXTURE, MICROSTRUCTURE AND FORMABILITY OF ALUMINUM ALLOYS  

Microsoft Academic Search

Texture, microstructure and formability were studied in Direct Chill Cast (DC) and Strip Cast (SC) aluminum alloys with regard to crystallographic anisotropy, the Portevin-Le Chatelier effect and aging softening behavior. It was found that material properties change greatly with manufacturing processes (DC vs. SC) and chemical composition (3xxx vs. 5 xxx alloys). DC cast hot band materials are usually fully

Xiang-Ming Cheng

2001-01-01

409

Castable nickel aluminide alloys for structural applications  

DOEpatents

The specification discloses nickel aluminide alloys which include as a component from about 0.5 to about 4 at. % of one or more of the elements selected from the group consisting of molybdenum or niobium to substantially improve the mechanical properties of the alloys in the cast condition. 4 figs.

Liu, C.T.

1992-04-28

410

Simulating the cooling of an immiscible alloy  

NASA Technical Reports Server (NTRS)

A computer program to simulate the cooling of immiscible alloys is described, and the Pb-Zn system is presented as an example. The program permits the user to calculate various compositions of immiscible alloys. Illustrations are presented which depict the sequence of computer-monitor displays generated by the program.

Probst, H. B.

1987-01-01

411

Machining of uranium and uranium alloys  

SciTech Connect

Uranium and uranium alloys can be readily machined by conventional methods in the standard machine shop when proper safety and operating techniques are used. Material properties that affect machining processes and recommended machining parameters are discussed. Safety procedures and precautions necessary in machining uranium and uranium alloys are also covered. 30 figures.

Morris, T.O.

1981-12-14

412

Special Features of Steels Alloyed with Nitrogen  

Microsoft Academic Search

The role of nitrogen as an alloying element that stabilizes austenite in steels and makes it possible to replace nickel, manganese, and other austenization promoters without deterioration of mechanical and special properties of the metal is considered. Put into practice this could reduce the volume of mining of the mentioned elements. Methods for introducing nitrogen into iron alloys are described.

M. V. Kostina; O. A. Bannykh; V. M. Blinov

2000-01-01

413

Application of modern aluminum alloys to aircraft  

Microsoft Academic Search

Aluminum alloys have been the primary material of choice for structural components of aircraft since about 1930. Although polymer matrix composites are being used extensively in high-performance military aircraft and are being specified for some applications in modern commercial aircraft, aluminum alloys are the overwhelming choice for the fuselage, wing, and supporting structure of commercial airliners and military cargo and

E. A. Starke; J. T. Staley

1996-01-01

414

Titanium and Titanium Alloys: Fundamentals and Applications  

Microsoft Academic Search

An excellent reference for materials scientists and engineers needing to gain further knowledge of these engineering materials. After introductory chapters on the fundamental material properties of titanium, readers will find comprehensive descriptions of the development, processing and properties of modern titanium alloys. There then follows a detailed discussion of the applications of titanium and its alloys in aerospace, medicine, energy

Christoph Leyens; Manfred Peters

2003-01-01

415

Status of vanadium alloys for fusion reactors  

Microsoft Academic Search

Advantages of vanadium alloys for fusion reactor structural applications are: low induced activation, excellent thermal stress factor, high strength at elevated temperatures, and superior ductility at low temperatures. Resistance to irradiation damage is also very impressive, i.e. very small DBTT shift by irradiation and low swelling. Research and development of vanadium alloys have made a remarkable progress in recent years

H. Matsui; K. Fukumoto; D. L. Smith; Hee M. Chung; W. van Witzenburg; S. N. Votinov

1996-01-01

416

Castable nickel aluminide alloys for structural applications  

DOEpatents

The specification discloses nickel aluminide alloys which include as a component from about 0.5 to about 4 at. % of one or more of the elements selected from the group consisting of molybdenum or niobium to substantially improve the mechanical properties of the alloys in the cast condition.

Liu, Chain T. (Oak Ridge, TN)

1992-01-01

417

Production of Aluminum Alloys: Status and Prospects  

Microsoft Academic Search

Due to their physico-mechanical properties, aluminum alloys are one of the most important structural materials presently in use. Aluminum alloys are second only to steel in terms of volume of production and substantially outstrip other nonferrous metals in this regard. For example, the worldwide production of different types of metals at the end of the last century broke down as

G. S. Makarov

2002-01-01

418

Bonding titanium to Rene 41 alloy  

NASA Technical Reports Server (NTRS)

Pair of intermediate materials joined by electron beam welding method welds titanium to Rene 41 alloy. Bond is necessary for combining into one structure high strength-to-density ratio titanium fan blades and temperature resistant nickel-base alloy turbine-buckets in VTOL aircraft lift-fan rotor.

Scott, R. W.

1972-01-01

419

Beryllium-aluminum alloys for investment castings  

Microsoft Academic Search

Beryllium-aluminum alloys containing greater than 60 wt % beryllium are very favorable materials for applications requiring light weight and high stiffness. However, when produced by traditional powder metallurgical methods, these alloys are expensive and have limited applications. To reduce the cost of making beryllium-aluminum components, Nuclear Metals Inc. (NMI) and Lockheed Martin Electronics and Missiles have recently developed a family

W. T. Nachtrab; N. Levoy

1997-01-01

420

Heat storage in alloy transformations. Final report  

SciTech Connect

A study conducted to determine the feasibility of using metal alloys as thermal energy storage media is described. The study had the following major elements: (1) the identification of congruently transforming alloys and thermochemical property measurements, (2) the development of a precise and convenient method for measuring volume change during phase transformation and thermal expansion coefficients, (3) the development of a numerical modeling routine for calculating heat flow in cylindrical heat exchangers containing phase-change materials, and (4) the identification of materials that could be used to contain the metal alloys. The elements selected as candidate media were limited to aluminum, copper, magnesium, silicon, zinc, calcium, and phosphorus on the basis of low cost and latent heat of transformation. Several new eutectic alloys and ternary intermetallic phases have been determined. A new method employing x-ray absorption techniques was developed to determine the coefficients of thermal expansion of both the solid and liquid phases and the volume change during phase transformation from data that are obtained during one continuous experimental test. The method and apparatus are discussed and the experimental results are presented. The development of the numerical modeling method is presented and results are discussed for both salt and metal alloy phase-change media. Candidate materials were evaluated to determine suitable materials for containment of the metal alloys. Graphite was used to contain the alloys during the volume change measurements. Silicon carbide has been identified as a promising containment material and surface-coated iron alloys were considered.

Birchenall, C E; Gueceri, S I; Farkas, D; Labdon, M B; Nagaswami, N; Pregger, B

1981-03-01

421

A Study of Tungsten-Technetium Alloys  

NASA Technical Reports Server (NTRS)

Technetium is a sister element to rhenium and has many properties that are similar to rhenium. It is predicted that technetium will have about the same effects on tungsten as rhenium in regard to increase in workability, lowered ductile to brittle transition temperature, and improved ductility. The objectives of the current work are to recover technetium from fission product wastes at Hanford Atomic Products Operation and reduce to purified metal; prepare W-Tc alloys containing up to 50 atomic% Tc; fabricate the alloy ingots to sheet stock, assessing the effect of technetium on workability; and perform metallurgical and mechanical properties evaluation of the fabricated alloys. Previous reports have described the separation and purification of 800 g of technetium metal powder, melting of technetium and W-Tc alloys, and some initial observation of the alloy material.

Maltz, J. W.

1965-01-01

422

The interaction of hydrogen with metal alloys  

NASA Technical Reports Server (NTRS)

Hydrogen diffusion coefficients were measured for several alloys, and these were determined to be about the same at 25 C for all alloys investigated. The relation of structure, both metallurgical and crystallographic, to the observed hydrogen distribution on charging was investigated, as well as the role of hydride formation in the hydrogen resistance of metal alloys. An attempt was made to correlate the structures and compositions of metal alloys as well as other parameters with the ratios of their notched tensile strengths in hydrogen to that in helium, R(H2/He), which are believed to represent a measure of their hydrogen resistance. Evidence supports the belief that hydrogen permeability and hydrogen resistance are increased by smaller grain sizes for a given alloy composition.

Danford, M. D.; Montano, J. W.

1991-01-01

423

Beryllium-aluminum alloys for investment castings  

SciTech Connect

Beryllium-aluminum alloys containing greater than 60 wt % beryllium are very favorable materials for applications requiring light weight and high stiffness. However, when produced by traditional powder metallurgical methods, these alloys are expensive and have limited applications. To reduce the cost of making beryllium-aluminum components, Nuclear Metals Inc. (NMI) and Lockheed Martin Electronics and Missiles have recently developed a family of patented beryllium-aluminum alloys that can be investment cast. Designated Beralcast, the alloys can achieve substantial weight savings because of their high specific strength and stiffness. In some cases, weight has been reduced by up to 50% over aluminum investment casting. Beralcast is now being used to make thin wall precision investment castings for several advanced aerospace applications, such as the RAH-66 Comanche helicopter and F-22 jet fighter. This article discusses alloy compositions, properties, casting method, and the effects of cobalt additions on strength.

Nachtrab, W.T.; Levoy, N. [Nuclear Metals Inc., Concord, MA (United States)

1997-05-01

424

Development of chromium-tungsten alloys  

SciTech Connect

Cr alloys containing 0-30 weight % W were investigated for their high temperature strength and oxidation resistance. These experimental alloys are intended for use in elevated temperature applications. Alloys were melted in a water-cooled, copper-hearth arc furnace. Microstructure of the alloys was studied using X-ray diffraction, scanning electron microscopy, and light microscopy. Meyer and Vickers hardness tests were utilized for measuring room temperature strength. A hot hardness tester with a spherical ruby indenter was used to study the strength of these materials between 800ºC and 1200ºC. A parabolic relationship was observed between load and indent size at all temperatures. On the other hand, decrease in hardness of the alloys with temperature was linear up to 1200ºC.

Dogan, Omer N.; Alman, David E.; Hawk, Jeffrey A.

2004-03-01

425

The recyclability of lead alloys  

SciTech Connect

In 1996, the production of battery lead and alloys from the recycle industry was 3 times the Primary lead production in the United States. The Buick Resource Recovery Center of the Doe Run Lead Company at a capacity of 90,000 tons per year is one of 25 plants recycling lead metal in the United States. This plant was commissioned in 1991 and has been running with a 0.30 Lost Time Accident rate per 200,000 hours of work. The paper delineates and ranks the cost of treating various impurities found in lead.

Worcester, A.W.; Sankovitch, M.J. [Doe Run Co., Herculaneum, MO (United States)

1997-12-01

426

Hydrogen resistant alloy - NASA 23  

NASA Technical Reports Server (NTRS)

The invention is a high-strength metal alloy that resists hydrogen embrittlement consisting essentially of thirty-seven (37) percent by weight of iron, thirty-two (32) percent by weight of nickel, fifteen (15) percent by weight of cobalt, ten (10) percent by weight of chromium, three (3) percent by weight of niobium, two-and-one-half (2.5) percent by weight of titanium, fifteen hundredths (0.15) percent by weight of aluminum, and an amount of carbon that does not exceed four hundredths (0.04) percent by weight.

Mcpherson, William B. (inventor); Kuruvilla, A. K. (inventor)

1994-01-01

427

Annealing studies of amorphous alloys  

SciTech Connect

Amorphous films of the alloys Ni-Nb, Ni-Mo, Mo-Si, and W-Si were sputter deposited on single-crystal semiconductor substrates. One-hour crystallization temperatures of the films were determined to within +-25/sup 0/C by annealing and x-ray diffraction measurements. Interdiffusion between Au or Cu overlayers and the amorphous films were studied by annealing combined with Auger Electron Spectroscopy (AES) profiling, and by Rutherford Backscatter (RBS) analysis. Supplementary measurements used to study structural relaxation and crystallization included resistivity as a function of temperature; DTA and DSC; and electron microscopy.

Wiley, J.D.; Perepezko, J.H.; Nordman, J.E.

1983-04-01

428

Laser welding of aluminum alloys  

SciTech Connect

Recent interest in reducing the weight of automobiles to increase fuel mileage has focused attention on the use of aluminum and associated joining technologies. Laser beam welding is one of the more promising methods for high speed welding of aluminum. Consequently, substantial effort has been expended in attempting to develop a robust laser beam welding process. Early results have not been very consistent in the process requirements but more definitive data has been produced recently. This paper reviews the process parameters needed to obtain consistent laser welds on 5,000 series aluminum alloys and discusses the research necessary to make laser processing of aluminum a reality for automotive applications.

Leong, K.H.; Sabo, K.R.; Sanders, P.G. [Argonne National Lab., IL (United States). Technology Development Div.; Spawr, W.J.

1997-03-01

429

Plating on stainless steel alloys  

SciTech Connect

Quantitative adhesion data are presented for a variety of electroplated stainless steel type alloys. Results show that excellent adhesion can be obtained by using a Wood's nickel strike or a sulfamate nickel strike prior to final plating. Specimens plated after Wood's nickel striking failed in the deposit rather than at the interface between the substrate and the coating. Flyer plate quantitative tests showed that use of anodic treatment in sulfuric acid prior to Wood's nickel striking even further improved adhesion. In contrast activation of stainless steels by immersion or cathodic treatment in hydrochloric acid resulted in very reduced bond strengths with failure always occurring at the interface between the coating and substrate.

Dini, J.W.; Johnson, H.R.

1981-09-11

430

Alloying Mechanisms for Epitaxial Nanocrystals  

NASA Astrophysics Data System (ADS)

The different mechanisms involved in the alloying of epitaxial nanocrystals are reported in this Letter. Intermixing during growth, surface diffusion, and intraisland diffusion were investigated by varying the growth conditions and annealing environments during chemical vapor deposition. The relative importance of each mechanism was evaluated in determining a particular composition profile for dome-shaped Ge:Si (001) islands. For samples grown at a faster rate, intermixing during growth was reduced. Si surface diffusion dominates during H2 annealing, whereas Ge surface diffusion and intraisland diffusion prevail during annealing in a PH3 environment.

Leite, M. S.; Medeiros-Ribeiro, G.; Kamins, T. I.; Williams, R. Stanley

2007-04-01

431

Ordering Phenomena in Undercooled Alloys  

SciTech Connect

Much of the work performed under this grant was devoted to using modern ideas in kinetics to understand atom movements in metallic alloys far from thermodynamic equilibrium. Kinetics arguments were based explicitly on the vacancy mechanism for atom movements. The emphasis was on how individual atom movements are influenced by the local chemical environment of the moving atom, and how atom movements cause changes in the local chemical environments. The author formulated a kinetic master equation method to treat atom movements on a crystal lattice with a vacancy mechanism. Some of these analyses [3,10,16] are as detailed as any treatment of the statistical kinetics of atom movements in crystalline alloys. Three results came from this work. Chronologically they were (1) A recognition that tracking time dependencies is not necessarily the best way to study kinetic phenomena. If multiple order parameters can be measured in a material, the ''kinetic path'' through the space spanned by these order parameters maybe just as informative about the chemical factors that affect atom movements [2,3,5-7,9-11,14-16,18,19,21,23,24,26,36,37]. (2) Kinetic paths need not follow the steepest gradient of the free energy function (this should be well-known), and for alloys far from equilibrium the free energy function can be almost useless in describing kinetic behavior. This is why the third result surprised me. (3) In cluster approximations with multiple order parameters, saddle points are common features of free energy functions. Interestingly, kinetic processes stall or change time scale when the kinetic path approaches a state at a saddle point in the free energy function, even though these states exist far from thermodynamic equilibrium. The author calls such a state a ''pseudostable'' (falsely stable) state [6,21,26]. I have also studied these phenomena by more ''exact'' Monte Carlo simulations. The kinetic paths showed features similar to those found in analytical theories. The author found that a microstructure with interfaces arranged in space as a periodic minimal surface is a probably an alloy at a saddle point in its free energy function [21,26,37].

Fultz, Brent

1997-07-17

432

Braze alloy spreading on steel  

NASA Technical Reports Server (NTRS)

Scanning electron microscopy (SEM) and Auger electron microscopy (AEM) were employed to observe elemental surface decomposition resulting from the brazing of a copper-treated steel. Two types of steel were used for the study, stainless steel (treated with a eutectic silver-copper alloy), and low-carbon steel (treated with pure copper). Attention is given to oxygen partial pressure during the processes; a low enough pressure (8 x 10 to the -5th torr) was found to totally inhibit the spreading of the filler material at a fixed heating cycle. With both types of steel, copper treatment enhanced even spreading at a decreased temperature.

Siewert, T. A.; Heine, R. W.; Lagally, M. G.

1978-01-01

433

Thermal stability of high temperature structural alloys  

SciTech Connect

High temperature structural alloys were evaluated for suitability for long term operation at elevated temperatures. The effect of elevated temperature exposure on the microstructure and mechanical properties of a number of alloys was characterized. Fe-based alloys (330 stainless steel, 800H, and mechanically alloyed MA 956), and Ni-based alloys (Hastelloy X, Haynes 230, Alloy 718, and mechanically alloyed MA 758) were evaluated for room temperature tensile and impact toughness properties after exposure at 750 C for 10,000 hours. Of the Fe-based alloys evaluated, 330 stainless steel and 800H showed secondary carbide (M{sub 23}C{sub 6}) precipitation and a corresponding reduction in ductility and toughness as compared to the as-received condition. Within the group of Ni-based alloys tested, Alloy 718 showed the most dramatic structure change as it formed delta phase during 10,000 hours of exposure at 750 C with significant reductions in strength, ductility, and toughness. Haynes 230 and Hastelloy X showed significant M{sub 23}C{sub 6} carbide precipitation and a resulting reduction in ductility and toughness. Haynes 230 was also evaluated after 10,000 hours of exposure at 850, 950, and 1050 C. For the 750--950 C exposures the M{sub 23}C{sub 6} carbides in Haynes 230 coarsened. This resulted in large reductions in impact strength and ductility for the 750, 850 and 950 C specimens. The 1050 C exposure specimens showed the resolution of M{sub 23}C{sub 6} secondary carbides, and mechanical properties similar to the as-received solution annealed condition.

Jordan, C.E.; Rasefske, R.K.; Castagna, A. [Lockheed Martin Corp., Schenectady, NY (United States)

1999-03-01

434

Theory of AlN, GaN, InN and their alloys  

NASA Astrophysics Data System (ADS)

This review focuses on the fundamental properties of III-V compound semiconductors from a theoretical or computational standpoint. Its purpose is to summarize the contributions of electronic structure theory to the present context and to provide some foundations for the modern techniques. This will enable one to assess the limitations of the techniques employed previously.

van Schilfgaarde, M.; Sher, A.; Chen, A.-B.

1997-06-01

435

NiAl alloys for structural uses  

NASA Technical Reports Server (NTRS)

Alloys based on the intermetallic compound NiAl are of technological interest as high temperature structural alloys. These alloys possess a relatively low density, high melting temperature, good thermal conductivity, and (usually) good oxidation resistance. However, NiAl and NiAl-base alloys suffer from poor fracture resistance at low temperatures as well as inadequate creep strength at elevated temperatures. This research program explored macroalloying additions to NiAl-base alloys in order to identify possible alloying and processing routes which promote both low temperature fracture toughness and high temperature strength. Initial results from the study examined the additions of Fe, Co, and Hf on the microstructure, deformation, and fracture resistance of NiAl-based alloys. Of significance were the observations that the presence of the gamma-prime phase, based on Ni3Al, could enhance the fracture resistance if the gamma-prime were present as a continuous grain boundary film or 'necklace'; and the Ni-35Al-20Fe alloy was ductile in ribbon form despite a microstructure consisting solely of the B2 beta phase based on NiAl. The ductility inherent in the Ni-35Al-20Fe alloy was explored further in subsequent studies. Those results confirm the presence of ductility in the Ni-35Al-20Fe alloy after rapid cooling from 750 - 1000 C. However exposure at 550 C caused embrittlement; this was associated with an age-hardening reaction caused by the formation of Fe-rich precipitates. In contrast, to the Ni-35Al-20Fe alloy, exploratory research indicated that compositions in the range of Ni-35Al-12Fe retain the ordered B2 structure of NiAl, are ductile, and do not age-harden or embrittle after thermal exposure. Thus, our recent efforts have focused on the behavior of the Ni-35Al-12Fe alloy. A second parallel effort initiated in this program was to use an alternate processing technique, mechanical alloying, to improve the properties of NiAl-alloys. Mechanical alloying in the conventional sense requires ductile powder particles which, through a cold welding and fracture process, can be dispersion strengthened by submicron-sized oxide particles. Using both the Ni-35Al-Fe alloys to contain approx. 1 v/o Y2O3. Preliminary results indicate that mechanically alloyed and extruded NiAl-Fe + Y2O3 alloys when heat treated to a grain-coarsened condition, exhibit improved creep resistance at 1000 C when compared to NiAl; oxidation resistance comparable to NiAl; and fracture toughness values a factor of three better than NiAl. As a result of the research initiated on this NASA program, a subsequent project with support from Inco Alloys International is underway.

Koss, D. A.

1991-01-01

436

Alloy hardening and softening in binary molybdenum alloys as related to electron concentration.  

NASA Technical Reports Server (NTRS)

Determination of the effects of alloy additions of Hf, Ta, W, Re, Os, Ir, and Pt on the hardness of Mo. Special emphasis was placed on alloy softening in these binary Mo alloys. A modified microhardness test unit permitted hardness determinations at homologous temperatures ranging from 0.02 to 0.15, where alloy softening normally occurs in bcc alloys. Results showed that alloy softening was produced by those elements having an excess of s + d electrons compared to Mo while those elements having an equal number or fewer s + d electrons than Mo failed to produce alloy softening. The magnitude of the softening and the amount of solute element at the hardness minimum diminished rapidly with increasing test temperature. At solute concentrations where alloy softening was observed, the temperature sensitivity of hardness was lowered. For solute elements having an excess of s + d electrons or fewer s + d electrons than Mo, alloy softening and alloy hardening can be correlated with the difference in number of s + d electrons of the solute element and Mo.

Stephens, J. R.; Witzke, W. R.

1972-01-01

437

Development of Combinatorial Methods for Alloy Design and Optimization  

Microsoft Academic Search

The primary goal of this research was to develop a comprehensive methodology for designing and optimizing metallic alloys by combinatorial principles. Because conventional techniques for alloy preparation are unavoidably restrictive in the range of alloy composition that can be examined, combinatorial methods promise to significantly reduce the time, energy, and expense needed for alloy design. Combinatorial methods can be developed

George M. Pharr; Easo P. George; Michael L Santella

2005-01-01

438

Corrosion-resistant alloys in oil and gas production  

SciTech Connect

This book features more than 150 classic NACE papers, including many from 1995, in the following six sections: general papers including field experiences; martensitic stainless steels; austenitic stainless steels; ferritic stainless steels; duplex stainless steels; precipitation hardened nickel alloys; solid solution nickel/cobalt base alloys; other alloys; and acidizing corrosion-resistant alloys.

Kolts, J.; Ciaraldi, S. [eds.

1995-12-31

439

Impact of alloying on microbiologically influenced corrosion--A review  

SciTech Connect

Alloying elements are added to metals to improve workability, electrical properties, and corrosion resistance. Alloying elements also alter the formation, chemical composition, thickness, and tenacity of corrosion products and may increase or decrease susceptibility to microbiologically influenced corrosion (MIC). The influence of alloying elements on MIC are reviewed for stainless steels and copper, nickel, aluminum, and titanium alloys.

Wagner, P.; Little, B. (Naval Research Lab., MS (United States))

1993-09-01

440

Wegner estimate for sparse and other generalized alloy type potentials  

E-print Network

Wegner estimate for sparse and other generalized alloy type potentials Werner Kirsch and Ivan on the occasion of his Sixtieth Birthday Abstract We prove a Wegner estimate for generalized alloy type models Generalized alloy type models 3 3 Selfadjointness 7 4 Wegner estimate for generalized alloy type potentials 9

441

Alloy Annotations for Efficient Incremental Analysis via Domain Specific Solvers  

E-print Network

Alloy Annotations for Efficient Incremental Analysis via Domain Specific Solvers Svetoslav Ganov@mail.utexas.edu Abstract--Alloy is a declarative modelling language based on first-order logic with sets and relations. Alloy formulas are checked for satisfiability by the fully automatic Alloy Analyzer. The analyzer, given

Perry, Dewayne E.

442

"Exploring damage management of high performance metallic alloys in critical  

E-print Network

"Exploring damage management of high performance metallic alloys in critical systems to develop new crack resistant alloys as well as new prognosis methods to manage durability and safety." Richard Metallic Alloys Research Group Cracking in high performance metallic alloys; due to fatigue, stress

Acton, Scott

443

Recent Research and Development Activities on Mg Alloys at CAAM  

Microsoft Academic Search

A brief review of recent research and development activities on light weight Mg alloys at the Center for Advanced Aerospace Materials (CAAM) is reported. Current research projects include various fields such as: (i) development of high strength\\/ductility Mg alloys; (ii) improvement in corrosion resistant of Mg alloys; (iii) semisolid state processing of Mg alloys and (iv) development of ultralight Mg

D. H. Kim; N. J. Kim

1998-01-01

444

Issues in the development of beta titanium alloys  

Microsoft Academic Search

In an attempt to expand the aerospace and industrial applications of these alloys, two international conferences on beta titanium alloys were recently held. They were the symposium Beta Titanium Alloys in the 90s, which was held at the 1993 TMS Annual Meeting in Denver, Colorado, and the International Workshop on Beta Titanium Alloys, which was sponsored by the French Metallurgical

D. Eylon; A. Vassel; Y. Combres; R. R. Boyer; P. J. Bania; R. W. Schutz

1994-01-01

445

HIGH CONDUCTIVITY COPPER-RICH Cu-Zr ALLOYS  

Microsoft Academic Search

A high-purity Cu--Zr alloy system was investigated. The Zr content of ; the alloys studied varied from 0.003 to 0.23%. The Solid solubility of Zr in Cu ; and some physical and mechanical properties of the alloys were determined. By ; proper heat treatment, Cu-- Zr alloy can develop a high electrical conductivity ; and resistance to softening at temperatures

Saarivirta

1960-01-01

446

Crystallographic attributes of a shape-memory alloy  

SciTech Connect

Shape-memory alloys are attractive for many potential applications. In an attempt to provide ideas and guidelines for the development of new shape-memory alloys, this paper reports on a series of investigations that examine the reasons in the crystallography that made (i) shape-memory alloys special amongst martensites and (ii) Nickel-Titanium special among shape-memory alloys.

Bhattacharya, K. [California Inst. of Tech., Pasadena, CA (United States). Div. of Engineering and Applied Science

1999-01-01

447

Development of Metallic Sensory Alloys  

NASA Technical Reports Server (NTRS)

Existing nondestructive evaluation (NDE) technologies are inherently limited by the physical response of the structural material being inspected and are therefore not generally effective at the identification of small discontinuities, making the detection of incipient damage extremely difficult. One innovative solution to this problem is to enhance or complement the NDE signature of structural materials to dramatically improve the ability of existing NDE tools to detect damage. To address this need, a multifunctional metallic material has been developed that can be used in structural applications. The material is processed to contain second phase sensory particles that significantly improve the NDE response, enhancing the ability of conventional NDE techniques to detect incipient damage both during and after flight. Ferromagnetic shape-memory alloys (FSMAs) are an ideal material for these sensory particles as they undergo a uniform and repeatable change in both magnetic properties and crystallographic structure (martensitic transformation) when subjected to strain and/or temperature changes which can be detected using conventional NDE techniques. In this study, the use of a ferromagnetic shape memory alloy (FSMA) as the sensory particles was investigated.

Wallace Terryl A.; Newman, John A.; Horne, Michael R.; Messick, Peter L.

2010-01-01

448

Vacancy formation and extraction energies in semiconductor compounds and alloys  

NASA Technical Reports Server (NTRS)

A model for calculating the extraction energies and vacancy-formation energies in diamond-cubic and zinc-blende semiconductors is developed on the basis of Harrison's (1980, 1983) tight-binding theory. The extraction energies provide a reference from which other final states of the removed atoms can be calculated. The results of calculations show that, in a given compound, the calculated extraction energies are larger for the anion than for the cation, with the difference between the cation and the anion being larger in the II-VI than in the III-V compounds. This is in agreement with experimental results.

Berding, M. A.; Sher, A.; Chen, A.-B.

1990-01-01

449

The effect of alloy composition on the mechanism of stress corrosion cracking of titanium alloys in aqueous environments  

NASA Technical Reports Server (NTRS)

The effects of alloy composition on the aqueous stress corrosion of titanium alloys were studied with emphasis on determining the interrelations among composition, phase structure, and deformation and fracture properties of the alpha phase in alpha-beta alloys. Accomplishments summarized include the effects of alloy composition on susceptibility, and metallurgical mechanisms of stress-corrosion cracking.

Boyd, J. D.; Williams, D. N.; Wood, R. A.; Jaffee, R. I.

1972-01-01

450

Thermal aging effects in refractory metal alloys  

NASA Technical Reports Server (NTRS)

The alloys of niobium and tantalum are attractive from a strength and compatibility viewpoint for high operating temperatures required in materials for fuel cladding, liquid metal transfer, and heat pipe applications in space power systems that will supply from 100 kWe to multi-megawatts for advanced space systems. To meet the system requirements, operating temperatures ranging from 1100 to 1600 K have been proposed. Expected lives of these space power systems are from 7 to 10 yr. A program is conducted at NASA Lewis to determine the effects of long-term, high-temperature exposure on the microstructural stability of several commercial tantalum and niobium alloys. Variables studied in the investigation include alloy composition, pre-age annealing temperature, aging time, temperature, and environment (lithium or vacuum), welding, and hydrogen doping. Alloys are investigated by means of cryogenic bend tests and tensile tests. Results show that the combination of tungsten and hafnium or zirconium found in commercial alloys such as T-111 and Cb-752 can lead to aging embrittlement and increased susceptibility to hydrogen embrittlement of ternary and more complex alloys. Modification of alloy composition helps to eliminate the embrittlement problem.

Stephens, J. R.

1986-01-01

451

Electroslag remelting of a vanadium alloy  

SciTech Connect

The Bureau of Mines, in cooperation with the Idaho National Engineering Laboratory, has electroslag melted a V-5Ti-5Cr alloy using a fused CaF{sub 2} flux. The alloy is a candidate for use in future fusion reactors. One objective of this research was to evaluate the feasibility of the electroslag melting process in separating simulated radioactive isotopes from the V alloy to demonstrate recyclability. Small amounts of Ca, Y, and Mn were added as surrogates for radioactive isotopes. Results showed that this vanadium alloy can be electroslag melted satisfactorily. The impurities added intentionally were removed or decreased successfully. Among the major alloying constituents, Cr was retained but there were some Ti losses. The latter may be controlled with process refinements. This research suggests that the electroslag melting process could be a suitable method for recycling V alloys after use in future fusion reactors, or for processing other reactive metal alloys with more immediate applications. 3 refs., 1 fig., 5 tabs.

Nafziger, R.H. [Bureau of Mines, Albany, OR (United States); Smolik, G.R.; Carmack, W.J. [Idaho National Engineering Lab., Idaho Falls, ID (United States)

1996-12-31

452

Structural alloys for high field superconducting magnets  

SciTech Connect

Research toward structural alloys for use in high field superconducting magnets is international in scope, and has three principal objectives: the selection or development of suitable structural alloys for the magnet support structure, the identification of mechanical phenomena and failure modes that may influence service behavior, and the design of suitable testing procedures to provide engineering design data. This paper reviews recent progress toward the first two of these objectives. The structural alloy needs depend on the magnet design and superconductor type and differ between magnets that use monolithic and those that employ force-cooled or ICCS conductors. In the former case the central requirement is for high strength, high toughness, weldable alloys that are used in thick sections for the magnet case. In the latter case the need is for high strength, high toughness alloys that are used in thin welded sections for the conductor conduit. There is productive current research on both alloy types. The service behavior of these alloys is influenced by mechanical phenomena that are peculiar to the magnet environment, including cryogenic fatigue, magnetic effects, and cryogenic creep. The design of appropriate mechanical tests is complicated by the need for testing at 4/sup 0/K and by rate effects associated with adiabatic heating during the tests. 46 refs.

Morris, J.W. Jr.

1985-08-01

453

Impurity control and corrosion resistance of magnesium-aluminum alloy  

SciTech Connect

The corrosion resistance of magnesium alloys is very sensitive to the contents of impurity elements such as iron. In this study, a series of diecast AXJ530 magnesium alloy samples were prepared with additions of Mn and Fe. Through a comprehensive phase diagram calculation and corrosion evaluation, the mechanisms for the tolerance limit of Fe in magnesium alloy are discussed. This adds a new dimension to control the alloying impurity in terms of alloying composition design and casting conditions.

Liu, M. [GM China Lab] [GM China Lab; Song, GuangLing [ORNL] [ORNL

2013-01-01

454

General and localized corrosion of magnesium alloys: A critical review  

Microsoft Academic Search

Magnesium (Mg) alloys as well as experimental alloys are emerging as light structural materials for current, new, and innovative\\u000a applications. This paper describes the influence of the alloying elements and the different casting processes on the microstructure\\u000a and performance of these alloys and corrosion. It gives a comprehensible approach for the resistance of these alloys to general,\\u000a localized and metallurgically

Edward Ghali; Wolfgang Dietzel; Karl-Ulrich Kainer

2004-01-01

455

Welding the four most popular aluminum alloys  

SciTech Connect

The fact that business is good in aluminum welding is a sure sign that more manufacturers and fabricators are using GMA and GTA welding to build new products out of this lightweight nonferrous metal. Among the most widely specified weldable grades are Alloys 6061, 5083, 5052 and 5454. A rundown on these four alloys, including properties and selected applications, is provided. Any company working with aluminum for the first time needs to know something about these four alloys. Alloys of copper-magnesium-silicon combination, of which 6061 is one, are heat-treatable. The three 5XXX series alloys, on the other hand, are nonheat-treatable. According to P.B. Dickerson, consultant, Lower Burrell, Pa., 5083, because of its high magnesium content, is the easiest of the four alloys to arc weld. Dickerson put the cut-off point in weldability at 3.5% magnesium. To prevent cracking, he added, both 6061 and 5052 require much more filler metal than do the other two alloys. Alloy 6061 consists of 0.25Cu, 0.6Si, 1.0Mg, and 0.20Cr. The main applications for 6061 aluminum are structural, architectural, automotive, railway, marine and pipe. It has good formability, weldability, corrosion resistance and strength. Although the 6XXX series alloys are prone to hot cracking, this condition can be readily overcome by correct choice of joint design and electrode. The most popular temper for 6061 is T6, although the -T651, -T4, and -F temper are also popular. The -T651 temper is like a -T6 temper, only it has received some final stretch hardening. The -T4 temper has been solution heat-treated and quenched. The -F temper is in the as-fabricated condition.

Irving, B.

1994-02-01

456

The Development of the Low-Cost Titanium Alloy Containing Cr and Mn Alloying Elements  

NASA Astrophysics Data System (ADS)

The ? + ?-type Ti-4.5Al-6.9Cr-2.3Mn alloy has been theoretically designed on the basis of assessment of the Ti-Al-Cr-Mn thermodynamic system and the relationship between the molybdenum equivalent and mechanical properties of titanium alloys. The alloy is successfully prepared by the split water-cooled copper crucible, and its microstructures and mechanical properties at room temperature are investigated using the OM, SEM, and the universal testing machine. The results show that the Ti-4.5Al-6.9Cr-2.3Mn alloy is an ? + ?-type alloy which is consistent with the expectation, and its fracture strength, yield strength, and elongation reach 1191.3, 928.4 MPa, and 10.7 pct, respectively. Although there is no strong segregation of alloying elements under the condition of as-cast, the segregation of Cr and Mn is obvious at the grain boundary after thermomechanical treatment.

Zhu, Kailiang; Gui, Na; Jiang, Tao; Zhu, Ming; Lu, Xionggang; Zhang, Jieyu; Li, Chonghe

2014-04-01

457

Development of oxide dispersion strengthened turbine blade alloy by mechanical alloying  

NASA Technical Reports Server (NTRS)

There were three nickel-base alloys containing up to 18 wt. % of refractory metal examined initially for oxide dispersion strengthening. To provide greater processing freedom, however, a leaner alloy was finally selected. This base alloy, alloy D, contained 0.05C/15Cr / 2Mo/4W/2Ta/4.5Al/2.Ti/015Zr/0.01-B/Bal. Ni. Following alloy selection, the effect of extrusion, heat treatment, and oxide volume fraction and size on microstructure and properties were examined. The optimum structure was achieved in zone annealed alloy D which contained 2.5 vol. % of 35 mm Y2O3 and which was extruded 16:1 at 1038 C.

Merrick, H. F.; Curwick, L. R. R.; Kim, Y. G.

1977-01-01

458

Hydrogen solubility in inhomogeneous Pd alloys  

SciTech Connect

As-cast, arc-melted Pd-Ni alloys are inhomogeneous and the H{sub 2} isotherms for these differ from their homogeneous counterparts in the two phase, (dilute + hydride), regions but not in the dilute phase regions. Pd-Ni alloys, which become inhomogeneous via a ternary (Pd + Ni + H) equilibrium phase change, have H{sub 2} isotherms which differ from those of the homogeneous alloy in both the two-phase and the dilute phase regions. These results are discussed with respect to the expected type of inhomogeneities.

Flanagan, T.B.; Wang, D.; Clewley, J.D. [Univ. of Vermont, Burlington, VT (United States). Chemistry Dept.

1998-12-31

459

New alloys to conserve critical elements  

NASA Technical Reports Server (NTRS)

Based on availability of domestic reserves, chromium is one of the most critical elements within the U.S. metal industry. New alloys having reduced chromium contents which offer potential as substitutes for higher chromium containing alloys currently in use are being investigated. This paper focuses primarily on modified Type 304 stainless steels having one-third less chromium, but maintaining comparable oxidation and corrosion properties to that of type 304 stainless steel, the largest single use of chromium. Substitutes for chromium in these modified Type 304 stainless steel alloys include silicon and aluminum plus molybdenum.

Stephens, J. R.

1978-01-01

460

First principles design of ductile refractory alloys  

SciTech Connect

The purpose of this work is to predict elastic and thermodynamic properties of Cr-based alloys based on first-principles calculations. The ultimate goal is to develop new materials for hightemperature applications in energy systems. In this study, we choose both Poisson ratio and Rice–Thomson parameter as computational screening tool for identifying ductilizing additives to the refractory alloys. In this report, we present our preliminary results on bulk modulus and enthalpy of mixing of 25 bcc Cr15X1 alloys.

Gao, M.C.; Rollett, A.D. (Carnegie-Mellon Univ., Pittsburgh, PA); Widom, M. (Carnegie-Mellon Univ., Pittsburgh, PA); Dogan, O.N.; King, P.E.

2008-03-09

461

Graded coatings for metallic implant alloys  

SciTech Connect

Graded glass and glass-hydroxyapatite coatings on Ti-based and Co-Cr alloys have been prepared using a simple enameling technique. The composition of the glasses has been tailored to match the thermal expansion of the alloys. By controlling the firing time, and temperature, it has been possible to control the reactivity between the glass and the alloy and to fabricate coatings (25 to 150 mu m thick) with excellent adhesion to the substrate, resistant to corrosion and able to precipitate hydroxyapatite during in vitro tests in simulated body fluid.

Saiz, Eduardo; Tomsia, Antoni P.; Fujino, Shigeru; Gomez-Vega, Jose M.

2002-08-01

462

Stress corrosion cracking of titanium alloys  

NASA Technical Reports Server (NTRS)

The effect of hydrogen on the properties of metals, including titanium and its alloys, was investigated. The basic theories of stress corrosion of titanium alloys are reviewed along with the literature concerned with the effect of absorbed hydrogen on the mechanical properties of metals. Finally, the basic modes of metal fracture and their importance to this study is considered. The experimental work was designed to determine the effects of hydrogen concentration on the critical strain at which plastic instability along pure shear directions occurs. The materials used were titanium alloys Ti-8Al-lMo-lV and Ti-5Al-2.5Sn.

Statler, G. R.; Spretnak, J. W.; Beck, F. H.; Fontana, M. G.

1974-01-01

463

Electrochemical Impedance Spectroscopy Of Metal Alloys  

NASA Technical Reports Server (NTRS)

Report describes use of electrochemical impedance spectroscopy (EIS) to investigate resistances of 19 alloys to corrosion under conditions similar to those of corrosive, chloride-laden seaside environment of Space Transportation System launch site. Alloys investigated: Hastelloy C-4, C-22, C-276, and B-2; Inconel(R) 600, 625, and 825; Inco(R) G-3; Monel 400; Zirconium 702; Stainless Steel 304L, 304LN, 316L, 317L, and 904L; 20Cb-3; 7Mo+N; ES2205; and Ferralium 255. Results suggest electrochemical impedance spectroscopy used to predict corrosion performances of metal alloys.

Macdowell, L. G.; Calle, L. M.

1993-01-01

464

Melting of iron-aluminide alloys  

SciTech Connect

The melting of Fe{sub 3}Al-based alloys at the Oak Ridge National Laboratory (ORNL) and commercial vendors is described. The melting processes evaluated includes are melting, air-induction melting (AIM), vacuum-induction melting (VIM), and electroslag remelting (ESR). The quality of the ingots studied are base on internal soundness and the surface finish obtained. The ingots were analyzed for recovery of various elements during melting. The impurity levels observed in the alloys by various melting processes were compared. Recommendations are made for viable processes for commercial melting of these alloys. 1 ref., 5 figs., 3 tabs.

Sikka, V.K.

1990-01-01

465

Gas-Alloy Interactions at Elevated Temperatures  

SciTech Connect

The understanding of the stability of metals and alloys against oxidation and other detrimental reactions, to the catalysis of important chemical reactions and the minimization of defects associated with processing and synthesis have one thing in common: At the most fundamental level, all these scientific/engineering problems involve interactions between metals and alloys (in the solid or liquid state) and gaseous atmospheres at elevated temperatures. In this special issue, we have collected a series of articles that illustrate the application of different theoretical, computational, and experimental techniques to investigate gas-alloy interactions.

Arroyave, Raymundo; Gao, Michael

2012-12-01

466

Laser surface alloying of ferritic Fe40Cr alloy with ruthenium  

Microsoft Academic Search

An investigation is made of the laser surface alloying of an experimental ferritic Fe-40Cr alloy with a rutherium powder coating using a continuous wave CO2 laser. Themicrostructure and corrosion behaviour of the laser surface alloying layer and the Fe-40Cr bulk allyo were examined by means of scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy, microhardness, potentiodynamic and corrosion potential measurements.

S. C. Tjong; J. S. Ku; N. J. Ho

1997-01-01

467

Preparation of a novel Ni\\/Co-based alloy gradient coating on surface of the crystallizer copper alloy by laser  

Microsoft Academic Search

A high wear-resistant gradient coating made of Ni\\/Co-based alloys on the surface of a Cu alloy substrate was synthesized using a YAG laser induced in situ reaction method. The coating consists of three layers: the first is a Ni-based alloy layer, the second and third are Co-based