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1

Nuclear Magnetic Resonance Studies of II-Vi and Iii-V Semiconductor Alloys  

NASA Astrophysics Data System (ADS)

In this thesis, I show how the basic solid-state NMR techniques can be used to study the local electronic structures of II-VI and III-V semiconductor alloys on an atomic scale. We have focused our studies on a few high quality samples, mainly Hg_{rm 1-x}Cd_{rm x} Te in the II-VI group, In-based binary III-V bulk semiconductors InP, InAs and InSb, and the III-V alloys Ga_{rm 1-x}In _{rm x}As. For solid-state-recrystallized device-quality bulk Hg_{rm 1-x}Cd _{rm x}Te samples, with x equal to 0.2, 0.22 and 0.28, corresponding to the narrow-gap semiconducting side of the band-inversion configurations, we have obtained detailed band-edge symmetry information, and site-selective quantitative charge carrier orbital characteristics on an atomic scale. Our study also indicated that a random cation distribution model well described the materials. We have investigated ^{115 }In magnetic resonance frequency shifts and the temperature dependence of these shifts in In-based III-V binary semiconductors. We have extracted the chemical shifts from the total shifts for these III-V semiconductors at 303K and 77K. Our NMR study of these binary semiconductors not only enhanced the understanding of electronic properties of these compounds, but also served as a reference for our NMR studies of III-V alloys. We performed ^{115}In NMR studies for dilute III-V semiconductor alloy Ga _{rm 1-x}In_ {rm x}As with x equal to 0.72%. Spectra clearly indicating the local electronic configurations were obtained. We carried out a series of field orientation studies, and determined the field gradient which is due to In-In pairs. This study provided evidence of local clustering of In atoms.

Shi, Jian-Hui

2

New III-V Semiconductor InGaAsBi Alloy Grown by Molecular Beam Epitaxy  

NASA Astrophysics Data System (ADS)

A new Bi-containing III-V semiconductor InGaAsBi alloy was firstly grown by molecular beam epitaxy (MBE). The high crystalline quality of the InGaAsBi epilayer with smooth interfaces was confirmed by X-ray diffraction measurements. Up to 2.5% Bi was incorporated in the film based on Rutherford back scattering (RBS) results. The RBS channeling spectra give clear evidence that the Bi atoms were substitutionally located in the InGaAs zinc-blende lattice sites.

Feng, Gan; Yoshimoto, Masahiro; Oe, Kunishige; Chayahara, Akiyoshi; Horino, Yuji

2005-09-01

3

Lattice Dynamics and Optical Properties of III -v Quaternary Mixed Alloys  

NASA Astrophysics Data System (ADS)

This thesis presents two topics related to the optical properties of III-V quaternary alloys. The first topic is the Raman scattering of the mixed alloys and the second topic is the measurement of the bandgap by linear optical methods. Chapter 3 describes the Raman scattering results for rm Al_{x}Ga _{0.5-x}In_{0.5}P, rm Ga_{x}In_{1 -x}As_{y}Sb_{1-y} , rm Ga_{1-x}In_ {x}P_{1-y}Sb_{y} , and rm Al_{x}Ga _{1-x}As_{y}Sb_ {1-y} quaternary alloys. The composition dependence of the peak intensity and energy shift for each optical phonon mode is reported. The rm Al_{x}Ga_{0.5-x}In_ {0.5}P system shows a three-mode behavior with the appearance of AlP, GaP and InP LO modes. The rm Ga_{x}In_{1 -x}As_{y}Sb_{1-y} system shows a two-mode behavior with the appearance of the GaAs LO and the GaSb and InAs mixed modes. The Ga_{rm 1-x}In _{rm x}P_ {rm 1-y}Sb_{ rm y} system shows a four-mode behavior with the appearance of GaP, InP, GaSb and InSb LO modes. The Raman spectra for rm Al_{x}Ga _{1-x}As_{y}Sb_ {1-y} show a three-mode behavior over the composition range investigated. The observed three modes are the GaAs LO, GaSb LO, and the AlAs and AlSb mixed modes. The behavior of optical phonons in III-V quaternary alloys is described by theoretical models developed in Chapter 4. The phonon behavior of rm Al _{x}Ga_{0.5-x}In_ {0.5}P and rm Ga_ {x}In_{1-x}As_{y }Sb_{1-y} is explained by the random element isodisplacement (REI) model. A modification of the REI model, the random cell isodisplacement (RCI) model, is used to explain the phonon behavior of rm Ga_{1-x}In_{x}P _{1-y}Sb_{y} and rm Al_{x}Ga_{1 -x}As_{y}Sb_{1-y} alloys. The change of phonon frequencies versus the alloy composition are calculated by these models. The calculated results are in good agreement with the Raman scattering results. In Chapter 5, 10 K absorption measurements have been done on rm Ga_{1-x}In _{x}P_{1-y}Sb_ {y} epilayers grown on the InP substrates. In order to deduce the bandgap, the absorption spectrum is fitted to Beer's law with an adjustable exponent. The bandgaps for samples grown on GaAs substrates are obtained using photoluminescence excitation (PLE) measurements. The PLE spectrum shows a clear decrease to zero before reaching the PL peak energy. The transition region of the PLE signal is about 50 meV. The bandgap is extracted by a linear extrapolation of the cutoff edge of the spectrum.

Jaw, Duen-Hwa

4

Connections between local and macroscopic properties in solids: The case of N in III-V-N alloys  

NASA Astrophysics Data System (ADS)

Although it is well known that dilute species often significantly modify the properties of solids in which they are hosted, a basic question remains open: How critical are their local properties in determining the macroscopic ones of the host material? Here we address this issue by taking N in dilute III-V-N alloys as a paradigmatic case and propose an original approach based on synergic progress in x-ray spectroscopies, density functional theory simulations, and hydrogen exposure as a tool to modify local bonding. In this way we are able to clarify how local properties operate by identifying the coupling mechanism between specific atomic orbitals responsible for the changes of both deep and band edge states. The success of our approach indicates a new way to connect local and macroscopic properties.

Amidani, L.; Ciatto, G.; Boscherini, F.; Filippone, F.; Mattioli, G.; Alippi, P.; Bondino, F.; Polimeni, A.; Capizzi, M.; Amore Bonapasta, A.

2014-02-01

5

Annealing group III-V compound doped silicon-germanium alloy for improved thermo-electric conversion efficiency  

NASA Technical Reports Server (NTRS)

The thermoelectric conversion efficiency of a GaP doped SiGe alloy is improved about 30 percent by annealing the alloy at a temperature above the melting point of the alloy, preferably stepwise from 1200 C to 1275 C in air to form large grains having a size over 50 microns and to form a GeGaP rich phase and a silicon rich phase containing SiP and SiO2 particles.

Vandersande, Jan W. (inventor); Wood, Charles (inventor); Draper, Susan L. (inventor)

1989-01-01

6

Defect engineering in III–V ternary alloys: effects of strain and local charge on the formation of substitutional and interstitial native defects  

Microsoft Academic Search

The effects of external and internal strains and of defect charges on the formation of vacancies, antisites and interstitials in GaAs and In0.5Ga0.5As have been investigated by first principles density functional methods. Present results show that strain and doping permit a defect engineering of III–V semiconductors. Specifically, they predict that doping may have major effects on the formation of antisites

A. Amore Bonapasta; P. Giannozzi

2001-01-01

7

Organometallic Vapor-Phase Epitaxial Growth and Characterization of Iii-V Semiconductor Alloys Emitting Visible Light: Gallium Arsenic Phosphide, Gallium Indium Phosphide, and Aluminum Gallium Indium Phosphide  

NASA Astrophysics Data System (ADS)

High band gap III-V semiconductor alloys, GaAs _{rm 1-x}P _{rm x}, Ga_ {rm x}In_{rm 1-x}P, and (Al_{rm x}Ga_{rm 1-x} )_{rm y}In _{rm 1-y}P, have been successfully grown on GaAs substrates using atmospheric pressure organometallic vapor-phase epitaxy (OMVPE). Trimethylgallium (TMGa), trimethylindium (TMIn), and trimethylaluminum (TMAI), were used as group III source materials, and arsine (AsH _3), phosphine (PH_3 ), and tertiarybutylphosphine (TBP) were used as group V source materials. For the growth of GaAs_{rm 1-x}P_{rm x} , strained layer superlattices (SLSs) were used to reduce misfit dislocation density. The grown structure consisted of a 2-?m P compositionally graded layer, a GaAs_{rm 1-y' }P_{rm y'}/GaAs _{rm 1-y}P _{rm y} SLS, and a 1- ?m GaAs_{0.6}P _{0.4} layer. It was found that linear grading gave the lowest dislocation density among the three grading layers investigated: sublinear, hyperlinear, and linear. A novel method, called "overshoot," was developed to prevent the release of residual strain in the 2-?m linearly graded layer. Using the overshoot method and SLSs, GaAs_{0.6 }P_{0.4} with good surface morphology, strong visible photoluminescence(PL) intensity, and a dislocation density of 6.5 times 10^5 cm^ {-2} has been obtained. For growth of GaInP, the effect of growth rate on the properties of the layers was investigated. It was observed that surface morphology degraded, the band gap at 300K decreased by 40meV, and the degree of ordering and size of ordered domains increased when the growth rate was changed from 12 to 4.1 mum/hr. At high growth rates (~12 mum/hr), the 300-K band gap of epilayer had the same values as the layers grown by LPE and was independent of the V/III ratio. The epilayers grown at a rate of 12 mum/hr and a V/III ratio of 148 had PL halfwidths of 35 and 7.2meV at 300K and 10K, respectively, the best reported results to date. A mechanism for the growth rate effect on the properties of OMVPE-grown GaInP is discussed. For the growth of AlGaInP, either PH_3 or TBP was used as the group V source material, respectively. For layers grown using trimethylalkyls and PH_3, excellent surface morphologies were obtained over the entire Al composition range. The 300-K band gap varied with x as 1.9 + 0.6x, consistent with calculated and previous results. The experimental results showed that the minority-carrier lifetime was constant when Al concentration was changed. For layers grown using trimethylalkyls and TBP, the P vapor pressure required was less than that using PH_3 to obtain good surface morphologies. No parasitic reactions were observed between TBP and the trimethylalkyls. However, the PL peak energy for layers grown using TBP did not follow the relation 1.9 + 0.6x. This was explained by a deep donor level, induced by an impurity from the TBP, bound to the X conduction band minimum. It is concluded that TBP is a suitable material to replace PH_3 for OMVPE growth of Al-containing compounds.

Cao, Diansheng

8

Valence-band anticrossing in mismatched III-V semiconductor alloys K. Alberi,1,2 J. Wu,1,2 W. Walukiewicz,1 K. M. Yu,1 O. D. Dubon,1,2 S. P. Watkins,3 C. X. Wang,3 X. Liu,4 Y.-J. Cho,4 and  

E-print Network

Valence-band anticrossing in mismatched III-V semiconductor alloys K. Alberi,1,2 J. Wu,1,2 W. Walukiewicz,1 K. M. Yu,1 O. D. Dubon,1,2 S. P. Watkins,3 C. X. Wang,3 X. Liu,4 Y.-J. Cho,4 and J. Furdyna4 1 received 15 November 2006; published 16 January 2007 We show that the band gap bowing trends observed

Wu, Junqiao

9

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

10

Photodetectors using III-V nitrides  

DOEpatents

A photodetector using a III-V nitride and having predetermined electrical properties is disclosed. The photodetector includes a substrate with interdigitated electrodes formed on its surface. The substrate has a sapphire base layer, a buffer layer formed from a III-V nitride and a single crystal III-V nitride film. The three layers are formed by electron cyclotron resonance microwave plasma-assisted molecular beam epitaxy (ECR-assisted MBE). Use of the ECR-assisted MBE process allows control and predetermination of the electrical properties of the photodetector.

Moustakas, Theodore D. (Dover, MA); Misra, Mira (Arlington, MA)

1997-01-01

11

III-V arsenide-nitride semiconductor  

NASA Technical Reports Server (NTRS)

III-V arsenide-nitride semiconductor are disclosed. Group III elements are combined with group V elements, including at least nitrogen and arsenic, in concentrations chosen to lattice match commercially available crystalline substrates. Epitaxial growth of these III-V crystals results in direct bandgap materials, which can be used in applications such as light emitting diodes and lasers. Varying the concentrations of the elements in the III-V materials varies the bandgaps, such that materials emitting light spanning the visible spectra, as well as mid-IR and near-UV emitters, can be created. Conversely, such material can be used to create devices that acquire light and convert the light to electricity, for applications such as full color photodetectors and solar energy collectors. The growth of the III-V material can be accomplished by growing thin layers of elements or compounds in sequences that result in the overall lattice match and bandgap desired.

Major, Jo S. (Inventor); Welch, David F. (Inventor); Scifres, Donald R. (Inventor)

2000-01-01

12

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

13

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

14

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

15

Electro-optical properties of III-V compound semiconductors for spatial light modulation applications  

Microsoft Academic Search

The applicability of III-V compounds such as GaAs and InP and the related ternary and quaternary alloys to the fabrication of spatial light modulators (SLMs) for use in optical and hybrid computers is investigated, reviewing the results of recent experimental investigations. The fundamental principles of electroabsorption and electrorefraction in direct-bandgap semiconductors and multiple-quantum-well structures are explained; measurement results for several

William S. C. Chang; H. H. Wieder; T. E. van Eck; A. L. Kellner; P. Chu

1987-01-01

16

Epochs I,II Epochs III-V  

E-print Network

Epochs I,II Epochs III-V Epochs VI-VIII A History of Algebraic Geometry Rob Easton February 26, 2010 Rob Easton A History of Algebraic Geometry #12;Epochs I,II Epochs III-V Epochs VI-VIII References., 1985. Rob Easton A History of Algebraic Geometry #12;Epochs I,II Epochs III-V Epochs VI-VIII Jean

Easton, Robert W.

17

Historical perspective on radiation effects in III-V devices  

Microsoft Academic Search

A historical review of radiation effects on III-V semiconductor devices is presented. The discussion ranges from examining early material and device studies to present-day understanding of III-V radiation effects. The purpose of this paper is to provide present researchers with a summary of discoveries and lessons learned from previous failures and successes.

Todd R. Weatherford

2003-01-01

18

III-V semiconductor devices integrated with silicon III-V semiconductor devices integrated with silicon  

NASA Astrophysics Data System (ADS)

The integration of III-V semiconductor devices with silicon is one of the most topical challenges in current electronic materials research. The combination has the potential to exploit the unique optical and electronic functionality of III-V technology with the signal processing capabilities and advanced low-cost volume production techniques associated with silicon. Key industrial drivers include the use of high mobility III-V channel materials (InGaAs, InAs, InSb) to extend the performance of Si CMOS, the unification of electronics and photonics by combining photonic components (GaAs, InP) with a silicon platform for next-generation optical interconnects and the exploitation of large-area silicon substrates and high-volume Si processing capabilities to meet the challenges of low-cost production, a challenge which is particularly important for GaN-based devices in both power management and lighting applications. The diverse nature of the III-V and Si device approaches, materials technologies and the distinct differences between industrial Si and III-V processing have provided a major barrier to integration in the past. However, advances over the last decade in areas such as die transfer, wafer fusion and epitaxial growth have promoted widespread renewed interest. It is now timely to bring some of these topics together in a special issue covering a range of approaches and materials providing a snapshot of recent progress across the field. The issue opens a paper describing a strategy for the epitaxial integration of photonic devices where Kataria et al describe progress in the lateral overgrowth of InP/Si. As an alternative, Benjoucef and Reithmaier report on the potential of InAs quantum dots grown direct onto Si surfaces whilst Sandall et al describe the properties of similar InAs quantum dots as an optical modulator device. As an alternative to epitaxial integration approaches, Yokoyama et al describe a wafer bonding approach using a buried oxide concept, Corbett et al describe the transfer printing and bonding of III-V die on to CMOS wafers and Dastjerdi et al describe the optical performance of free-standing InGaAsP tube optical cavities which may be transferred to silicon substrates. Finally, describing important recent progress on GaN-based devices Jiang et al describe their work on InGaN light-emitting diodes on Si (1?1?1) substrates, Wallis et al describe similar structures with the emphasis on x-ray methods for the control of AlGaN buffer layer strain, Kumar et al describe low leakage current, large-area Schottky barrier photodetectors on Si, whilst Soltani et al describe their recent progress on AlGaN/GaN high electron mobility transistors grown on (1?0?0) and (1?1?0) silicon substrates. Overall, we think that this special issue of Semiconductor Science and Technology provides a timely overview of progress and the opportunities in this exciting and important field. Finally, we would like to thank the IOP editorial staff, in particular Alice Malhador, for their support, and we would also like to thank all contributors for their efforts in making this special issue possible.

Hopkinson, Mark; Martin, Trevor; Smowton, Peter

2013-09-01

19

III-V High-Efficiency Multijunction Photovoltaics (Fact Sheet)  

SciTech Connect

Capabilities fact sheet that includes scope, core competencies and capabilities, and contact/web information for III-V High-Efficiency Multijunction Photovoltaics at the National Center for Photovoltaics.

Not Available

2011-06-01

20

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

21

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

22

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

23

Isoelectronic dopant and surfactant effects in III/V semiconductors  

NASA Astrophysics Data System (ADS)

Organometallic vapor-phase epitaxy (OMVPE) is a versatile growth technique used for production of many III/V semiconductors. Surface processes are an important aspect of any epitaxial growth technique. Understanding these surface processes and the ability to control them is of paramount importance to developing materials with specific properties for devices. This study focuses on the effects of using isoelectronic elements on materials properties of III/V semiconductors grown via OMVPE. The addition of diborane during the growth of GaAs is investigated. The solubility of B in GaAs is calculated to be only 5 x 1015cm -3. The bowing parameter is calculated to be 11.8 +/- 0.6 eV. Experimental data show that B incorporation is highly dependent on growth conditions and changed by a factor of 103 for conditions studied. The maximum amount of B incorporated was 4 x 1019cm -3. Photoluminescence (PL) experiments show that the band gap of GaAs was reduced with B incorporation, and was used to extrapolate a bowing parameter of 12.4 +/- 4.5 eV in close agreement with the theoretical value. This study also presents the results of using dimethylhydrazine during the growth of GaP and GaInP. The N content in GaP is studied up to approximately 1%. PL experiments show an increase in PL intensity for low concentrations of N. The PL progresses from N-N pairs to a N triplet state at 2070 meV to a broad peak at lower energy with no sharp features. However, at the highest N concentration of 2.3 x 1020cm-3, the PL intensity is significantly reduced. Annealing the sample increased the integrated intensity by 30%. The use of the surfactant N during the growth of GaInP produces changes in microstructure, morphology, and composition, while only 2 x 10 18cm-3 N is incorporated. Experiments show that ordering is reduced and suggests that N disorders GaInP via two mechanisms, (1) by replacing P dimers reducing the thermodynamic driving force, and (2) by roughening the surface creating pyramid features with angles >8°. The addition of the surfactants Sb and Bi enhances the Zn and H concentration in the solid during the growth of Zn-doped GaInP. It is found that adding a small amount of either triethylantimony or trimethylbismuth (surfactant/V v ? 5.5 x 10-4) can increase the Zn concentration by a factor of 2.1. Secondary ion mass spectroscopy found that Bi and Sb were not significantly incorporated into the solid. Thus, these effects are not from alloying, but suggest that neutral Zn-H complexes are incorporated during growth leading to increased Zn in the solid.

Chapman, David Cook

24

Assessment of a low-cost gold-free metallization for III–V high concentrator solar cells  

Microsoft Academic Search

A gold-free metallization is proposed to be used as the grid contact in III–V concentrator solar cells. This metallization is based on the Cu\\/Ge system which has been reported to attain very low specific contact resistances on n-GaAs. In this letter, we show that metal layers with low resistivity (13??cm) can be obtained if the copper content in the alloy

Ignacio Rey-Stolle; Beatriz Galiana; Carlos Algora

2007-01-01

25

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

26

Coherent Twinning Phenomena: Towards Twinning Superlattices in III-V  

E-print Network

Coherent Twinning Phenomena: Towards Twinning Superlattices in III-V Semiconducting Nanowires Qihua an additional series of diffraction peaks consistent with a quasiperiodic placement of twinning boundaries along.e., the distance between twin boundaries, has been found to depend on the temperature gradient imposed

Xiong, Qihua

27

III-V aresenide-nitride semiconductor materials and devices  

NASA Technical Reports Server (NTRS)

III-V arsenide-nitride semiconductor crystals, methods for producing such crystals and devices employing such crystals. Group III elements are combined with group V elements, including at least nitrogen and arsenic, in concentrations chosen to lattice match commercially available crystalline substrates. Epitaxial growth of these III-V crystals results in direct bandgap materials, which can be used in applications such as light emitting diodes and lasers. Varying the concentrations of the elements in the III-V crystals varies the bandgaps, such that materials emitting light spanning the visible spectra, as well as mid-IR and near-UV emitters, can be created. Conversely, such material can be used to create devices that acquire light and convert the light to electricity, for applications such as full color photodetectors and solar energy collectors. The growth of the III-V crystals can be accomplished by growing thin layers of elements or compounds in sequences that result in the overall lattice match and bandgap desired.

Major, Jo S. (Inventor); Welch, David F. (Inventor); Scifres, Donald R. (Inventor)

1997-01-01

28

III-V Multijunctions in Amonix Solar Power Plants  

NASA Astrophysics Data System (ADS)

Amonix has installed over 300 kW of CPV systems based on III-V multijunctions. A performance model has been developed that effectively predicts system peak power and aggregate energy generation. System AC efficiencies reach 25% and power is expected to increase by over 10% in the next year.

Kinsey, Geoffrey S.; Gordon, Robert; Stone, Kenneth; Garboushian, Vahan

2010-10-01

29

Recent progress in III-V based ferromagnetic semiconductors: Band structure, Fermi level, and tunneling transport  

NASA Astrophysics Data System (ADS)

Spin-based electronics or spintronics is an emerging field, in which we try to utilize spin degrees of freedom as well as charge transport in materials and devices. While metal-based spin-devices, such as magnetic-field sensors and magnetoresistive random access memory using giant magnetoresistance and tunneling magnetoresistance, are already put to practical use, semiconductor-based spintronics has greater potential for expansion because of good compatibility with existing semiconductor technology. Many semiconductor-based spintronics devices with useful functionalities have been proposed and explored so far. To realize those devices and functionalities, we definitely need appropriate materials which have both the properties of semiconductors and ferromagnets. Ferromagnetic semiconductors (FMSs), which are alloy semiconductors containing magnetic atoms such as Mn and Fe, are one of the most promising classes of materials for this purpose and thus have been intensively studied for the past two decades. Here, we review the recent progress in the studies of the most prototypical III-V based FMS, p-type (GaMn)As and its heterostructures with focus on tunneling transport, Fermi level, and bandstructure. Furthermore, we cover the properties of a new n-type FMS, (In,Fe)As, which shows electron-induced ferromagnetism. These FMS materials having zinc-blende crystal structure show excellent compatibility with well-developed III-V heterostructures and devices.

Tanaka, Masaaki; Ohya, Shinobu; Nam Hai, Pham

2014-03-01

30

Recent progress in III-V based ferromagnetic semiconductors: Band structure, Fermi level, and tunneling transport  

SciTech Connect

Spin-based electronics or spintronics is an emerging field, in which we try to utilize spin degrees of freedom as well as charge transport in materials and devices. While metal-based spin-devices, such as magnetic-field sensors and magnetoresistive random access memory using giant magnetoresistance and tunneling magnetoresistance, are already put to practical use, semiconductor-based spintronics has greater potential for expansion because of good compatibility with existing semiconductor technology. Many semiconductor-based spintronics devices with useful functionalities have been proposed and explored so far. To realize those devices and functionalities, we definitely need appropriate materials which have both the properties of semiconductors and ferromagnets. Ferromagnetic semiconductors (FMSs), which are alloy semiconductors containing magnetic atoms such as Mn and Fe, are one of the most promising classes of materials for this purpose and thus have been intensively studied for the past two decades. Here, we review the recent progress in the studies of the most prototypical III-V based FMS, p-type (GaMn)As and its heterostructures with focus on tunneling transport, Fermi level, and bandstructure. Furthermore, we cover the properties of a new n-type FMS, (In,Fe)As, which shows electron-induced ferromagnetism. These FMS materials having zinc-blende crystal structure show excellent compatibility with well-developed III-V heterostructures and devices.

Tanaka, Masaaki, E-mail: masaaki@ee.t.u-tokyo.ac.jp [Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Institute for Nano Quantum Electronics, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan); Ohya, Shinobu, E-mail: ohya@cryst.t.u-tokyo.ac.jp; Nam Hai, Pham, E-mail: pham@cryst.t.u-tokyo.ac.jp [Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan)

2014-03-15

31

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

32

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

33

Heterogeneously integrated III-V/silicon distributed feedback lasers.  

PubMed

Heterogeneously integrated III-V-on-silicon second-order distributed feedback lasers utilizing an ultra-thin DVS-BCB die-to-wafer bonding process are reported. A novel DFB laser design exploiting high confinement in the active waveguide is demonstrated. A 14 mW single-facet output power coupled to a silicon waveguide, 50 dB side-mode suppression ratio and continuous wave operation up to 60°C around 1550 nm is obtained. PMID:24343010

Keyvaninia, S; Verstuyft, S; Van Landschoot, L; Lelarge, F; Duan, G-H; Messaoudene, S; Fedeli, J M; De Vries, T; Smalbrugge, B; Geluk, E J; Bolk, J; Smit, M; Morthier, G; Van Thourhout, D; Roelkens, G

2013-12-15

34

Method of fabricating vertically aligned group III-V nanowires  

DOEpatents

A top-down method of fabricating vertically aligned Group III-V micro- and nanowires uses a two-step etch process that adds a selective anisotropic wet etch after an initial plasma etch to remove the dry etch damage while enabling micro/nanowires with straight and smooth faceted sidewalls and controllable diameters independent of pitch. The method enables the fabrication of nanowire lasers, LEDs, and solar cells.

Wang, George T; Li, Qiming

2014-11-25

35

III-V Growth on Silicon Toward a Multijunction Cell  

Microsoft Academic Search

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

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

2005-01-01

36

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

37

Electronic bands and excited states of III-V semiconductor polytypes with screened-exchange density functional calculations  

SciTech Connect

The electronic band structures and excited states of III-V semiconductors such as GaP, AlP, AlAs, and AlSb for various polytypes are determined employing the screened-exchange density functional calculations implemented in the full-potential linearized augmented plane-wave methods. We demonstrate that GaP and AlSb in the wurtzite (WZ) structure have direct gap while III-V semiconductors in the zinc blende, 4H, and 6H structures considered in this study exhibit an indirect gap. Furthermore, we find that inclusion of Al atoms less than 17% and 83% in the hexagonal Al{sub x}Ga{sub 1?x}P and Al{sub x}Ga{sub 1?x}As alloys, respectively, leads to a direct transition with a gap energy of ?2.3 eV. The feasibility of III-V semiconductors with a direct gap in WZ structure offers a possible crystal structure engineering to tune the optical properties of semiconductor materials.

Akiyama, Toru; Nakamura, Kohji; Ito, Tomonori [Department of Physics Engineering, Mie University, 1577 Kurima-Machiya, Tsu 514-8507 (Japan); Freeman, Arthur J. [Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208 (United States)

2014-03-31

38

Hybrid III-V/silicon SOA for photonic integrated circuits  

NASA Astrophysics Data System (ADS)

Silicon photonics has reached a considerable level of maturity, and the complexity of photonic integrated circuits (PIC) is steadily increasing. As the number of components in a PIC grows, loss management becomes more and more important. Integrated semiconductor optical amplifiers (SOA) will be crucial components in future photonic systems for loss compensation. In addition, there are specific applications, where SOAs can play a key role beyond mere loss compensation, such as modulated reflective SOAs in carrier distributed passive optical networks or optical gates in packet switching. It is, therefore, highly desirable to find a generic integration platform that includes the possibility of integrating SOAs on silicon. Various methods are currently being developed to integrate light emitters on silicon-on-insulator (SOI) waveguide circuits. Many of them use III-V materials for the hybrid integration on SOI. Various types of lasers have been demonstrated by several groups around the globe. In some of the integration approaches, SOAs can be implemented using essentially the same technology as for lasers. In this paper we will focus on SOA devices based on a hybrid integration approach where III-V material is bonded on SOI and a vertical optical mode transfer is used to couple light between SOI waveguides and guides formed in bonded III-V semiconductor layers. In contrast to evanescent coupling schemes, this mode transfer allows for a higher confinement factor in the gain material and thus for efficient light amplification over short propagation distances. We will outline the fabrication process of our hybrid components and present some of the most interesting results from a fabricated and packaged hybrid SOA.

Kaspar, P.; Brenot, R.; Le Liepvre, A.; Accard, A.; Make, D.; Levaufre, G.; Girard, N.; Lelarge, F.; Duan, G.-H.; Olivier, S.; Jany, Christophe; Kopp, C.; Menezo, S.

2014-11-01

39

Recent Soviet microelectronics research on III-V compounds semiconductors  

NASA Astrophysics Data System (ADS)

The activity in the Soviet Union on III-V compound semiconductor devices during the past five years is examined in the areas of materials, processes, radiation effects, and devices by a search of the translated technical journals. The majority of the work in III-V materials is concerned with gallium arsenide (GaAs), and the materials are certainly of the quality needed to make integrated circuits (ICs). However, the focus of Soviet growth and characterization studies appears to be basic materials properties, rather than development of capabilities and understanding for making integrated circuits. In processing, the Soviets appear to have very little effort on metaloorganic chemical vapor deposition on III-V compounds, while this is the process of choice in the West. There is, however, a substantial effort on X-ray lithography for silicon that could be extended to GaAs. High-quality work is also reported for ion beam, electron beam, optical projection, and laser processing silicon. Research on metallization (interconnection) and dielectric deposition processes for GaAs is absent. Soviet research on ion implantation and laser annealing in compound semiconductors is largely directed toward basic phenomena, such as defect information, rather than on electrical characteristics considered important for integrated circuit fabrication. Outstanding basic work is also being conducted on the radiation effects of electrons, protons, alpha, gamma, and X-rays on materials. These Soviet studies of radiation effects do not appear to be directed toward the fabrication of actual devices. Soviet GaAs device work appears to be generally of a theoretical nature, relying in part on device data obtained from Western articles. The most advanced involves the junction field effect transistor and heterojunction bipolar transistor, with little work reported on the fabrication of GaAs integrated circuits.

Sello, H.; Kirkpatrick, C. G.

1988-08-01

40

Nanometre-scale electronics with III-V compound semiconductors.  

PubMed

For 50 years the exponential rise in the power of electronics has been fuelled by an increase in the density of silicon complementary metal-oxide-semiconductor (CMOS) transistors and improvements to their logic performance. But silicon transistor scaling is now reaching its limits, threatening to end the microelectronics revolution. Attention is turning to a family of materials that is well placed to address this problem: group III-V compound semiconductors. The outstanding electron transport properties of these materials might be central to the development of the first nanometre-scale logic transistors. PMID:22094691

del Alamo, Jesús A

2011-11-17

41

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

42

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

43

III/V Nanowires for Electronic and Optoelectronic Applications  

NASA Astrophysics Data System (ADS)

III/V semiconductor nanowires are grown by the vapour-liquid solid growth mode from Au seed particles in an industrial type metal-organic vapour phase epitaxial apparatus. For electronic applications InAs nanowires with very high electron were developed on InAs (111), InAs (100), and GaAs (111) substrates. The wires were deposited on insulating host substrate for metal-insulator-semiconductor FET fabrication. Their excellent DC and RF performance are presented. For optoelectronic applications the focus is on selective n- and p-type doping. GaAs nanowires with an axial p-n junction are presented. Pronounced electroluminescence at room temperature reveals the quality of the fabricated device. Moreover, spatially resolved photocurrent microscopy shows that optical generation of carriers took place only in the vicinity of the p-n junction. A solar conversion efficiency of 9 % was obtained. In summary, III/V semiconductor nanowires are emerged to high performance and versatile nanoscaled building blocks for both electronic and optoelectronic applications.

Gutsche, Christoph; Regolin, Ingo; Lysov, Andrey; Blekker, Kai; Do, Quoc-Thai; Prost, Werner; Tegude, Franz-Josef

44

Carbon doping of III-V compound semiconductors  

SciTech Connect

Focus of the study is C acceptor doping of GaAs, since C diffusion coefficient is at least one order of magnitude lower than that of other common p-type dopants in GaAs. C ion implantation results in a concentration of free holes in the valence band < 10% of that of the implanted C atoms for doses > 10{sup 14}/cm{sup 2}. Rutherford backscattering, electrical measurements, Raman spectroscopy, and Fourier transform infrared spectroscopy were amonth the techniques used. Ga co-implantation increased the C activation in two steps: first, the additional radiation damage creates vacant As sites that the implanted C can occupy, and second, it maintains the stoichiometry of the implanted layer, reducing the number of compensating native defects. In InP, the behavior of C was different from that in GaAs. C acts as n-type dopant in the In site; however, its incorporation by implantation was difficult to control; experiments using P co-implants were inconsistent. The lattice position of inactive C in GaAs in implanted and epitaxial layers is discussed; evidence for formation of C precipitates in GaAs and InP was found. Correlation of the results with literature on C doping in III-V semiconductors led to a phenomenological description of C in III-V compounds (particularly GaAs): The behavior of C is controlled by the chemical nature of C and the instrinsic Fermi level stabilization energy of the material.

Moll, A.J.

1994-09-01

45

Status of ion implantation doping and isolation of III-V nitrides  

SciTech Connect

Ion implantation doping and isolation has played a critical role in the realization of high performance photonic and electronic devices in all mature semiconductor material systems. This is also expected to be the case for the binary III-V nitrides (InN, GaN, and AlN) and their alloys as the epitaxial material quality improves and more advanced device structures are fabricated. With this in mind, we review the status of implant doping and isolation of GaN and the ternary alloys AlGaN, InGaN, and InAlN. In particular, we reported on the successful n- and p-type doping of GaN by ion implantation of Mg+P and Si, respectively, and subsequent high temperature rapid thermal anneals in excess of 1000{degrees}C. In the area of implant isolation, N-implantation has been shown to compensate both n- and p-type GaN, N and O-implantation effectively compensates InAlN, and InGaN shows limited compensation with either N or F implantation.

Zolper, J.C. [Sandia National Labs., Albuquerque, NM (United States); Pearton, S.J.; Abernathy, C.R. [Univ. of Florida, Gainesville, FL (United States)] [and others

1995-09-01

46

III-V-on-silicon multi-frequency lasers.  

PubMed

Compact multi-frequency lasers are realized by combining III-V based optical amplifiers with silicon waveguide optical demultiplexers using a heterogeneous integration process based on adhesive wafer bonding. Both devices using arrayed waveguide grating routers as well as devices using ring resonators as the demultiplexer showed lasing with threshold currents between 30 and 40 mA and output powers in the order of a few mW. Laser operation up to 60°C is demonstrated. The small bending radius allowable for the silicon waveguides results in a short cavity length, ensuring stable lasing in a single longitudinal mode, even with relaxed values for the intra-cavity filter bandwidths. PMID:23736620

Keyvaninia, S; Verstuyft, S; Pathak, S; Lelarge, F; Duan, G-H; Bordel, D; Fedeli, J-M; De Vries, T; Smalbrugge, B; Geluk, E J; Bolk, J; Smit, M; Roelkens, G; Van Thourhout, D

2013-06-01

47

High rate ECR etching of III-V nitride materials  

SciTech Connect

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 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 3,800 {angstrom}/min for InN, 3,500 {angstrom}/min for GaN, and 1,170 A/min for AlN are reported. Etch anisotropy, surface morphology, and near-surface stoichiometry will be discussed.

Shul, R.J.; Howard, A.J.; Kilcoyne, S.P. [Sandia National Labs., Albuquerque, NM (United States); Pearton, S.J.; Abernathy, C.R.; Vartuli, C.B. [Univ. of Florida, Gainesville, FL (United States); Barnes, P.A.; Bozack, M.J. [Auburn Univ., AL (United States)

1994-12-31

48

Nanostencil lithography for fabrication of III-V nanostructures  

NASA Astrophysics Data System (ADS)

Nanostencil Lithography (NStL), while comparatively still in infant stages, is proving to be a viable option for low-cost and high resolution fabrication. An ideal stencil for NStL consists of a low-stressed silicon nitride membrane supported on a silicon chip with required patterned features in nanometer range that become apertures. The stencil is used as a shadow mask and placed in close contact on top of a substrate/wafer. This pair is then ready for either depositing metal through the apertures in the stencil using variety of deposition techniques or etching the substrate using dry etching techniques with stencil acting as a mask. The nanostencils were fabricated using focused ion beam writing on a silicon nitride window/membrane. We made well-ordered array of 700 nm diameter and 15 nm thick gold and chromium nanodots on III-V substrate. Metal layers were deposited using e-beam evaporator. The formed gold nanodots can be used for vapor-liquid-solid nanowire growth (bottom-up), while the chromium nanodots were used as a mask for reactive ion etching of GaAs structures, for instance, fabricating nanowires (top-down approach). We used the nanostencil directly as a mask for dry etching of InP substrate for making nanoholes array. Making these types of nanoholes in silicon oxide layer deposited on the top of III-V substrate opens the possibility to use in selective area growth of nanowires. Additionally, we fabricated optical nanoantenna structures to demonstrate other possible usage of NStL.

Vora, Kaushal; Karouta, Fouad; Jagadish, Chennupati

2013-09-01

49

optical phonon scattering. In III-V terahertz quantum cascade lasers, the upper state life-  

E-print Network

639 optical phonon scattering. In III-V terahertz quantum cascade lasers, the upper state life than III-V mate- rials. A silicon-based quantum cascade laser therefore promises to be a good candidate the design of successful silicon/germa- nium quantum cascade struc- tures more challenging than is the case

Kuzmanovic, Aleksandar

50

III-V Semiconductor Diodes and the Terahertz Technology Gap  

NASA Astrophysics Data System (ADS)

The terahertz frequency band, spanning from roughly 100 GHz through 10 THz, is often sited as the most scientifically rich, yet unexplored region of the electromagnetic spectrum. Scientific applications include radio astronomy, chemical spectroscopy, plasma diagnostics, compact range radar, atmospheric remote sensing and electron paramagnetic resonance studies of organic molecules. Recently, many groups have developed rudimentary imaging systems for this frequency band, either for basic scientific investigations or defense and security scanners. However, the inherent difficulty of creating sources of terahertz power that are sufficiently powerful, tunable, reliable and robust is a primary difficulty. Researchers in the field generally speak of the terahertz technology gap, which spans the transition from classical electronics to quantum photonics. This talk will consider the nature of the terahertz technology gap and the technological transition from electronics to photonics. Efforts to develop useful sources and receivers of terahertz energy based on III-V semiconductor diodes will be discussed. Also, important recent results, including the development of all-solid-state sources and receivers for the 0.1 -- 3 THz frequency range will be presented. Finally, the fundamental limitations of this technology will be considered.

Crowe, Thomas

2006-03-01

51

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

52

Characterization of III-V materials by optical interferometry  

NASA Astrophysics Data System (ADS)

Digital interference microscopy is a new measuring technique with submicron horizontal resolution and nanometric vertical resolution, that can be used for the three-dimensional analysis of surface defects and device features in many microelectronics applications on bulk materials and epitaxial layers. In this paper we show how certain defects can be analysed on III-V materials and devices using two different interferometric techniques. The choice of the technique depends on the height and the slope of the surface features to be measured. We show that small defects less than ?/2 in height, or surfaces with shallow continuous slopes upto one or two microns high are best profiled with the phase stepping technique (PSM) because of the high vertical resolution of 1 nm and the higher speed and precision. This is illustrated by studies of the surface polish of InP wafers, defects after chemical etching of tin doped InP, defects on an epitaxial layer of GaAs on InP and quantum dot structures on GaAs. For measuring devices which contain mesas and grooves with step heights greater than ?/2, the peak fringe scanning (PFSM) method is the better choice. The vertical resolution is slightly less (4 nm), but the vertical range is higher (upto 15 ?m) as demonstrated with the measurement of an etched groove in a laser/detector device on a quaternary layer on InP, and a MESFET device on GaAs. Compared with electron microscopy and the new near field scanning techniques, digital interference microscopy has the advantages of ease of use and speed of analysis and being able to resolve certain problems that are difficult or not possible by other means, such as profiling deep narrow etched grooves, or measuring the relief of a surface hidden under a transparent layer. The main disadvantages are that the horizontal resolution is limited to the resolving power of the objective and that errors due to variations in the optical properties of the sample need to be taken into account. La microscopie interférentielle numérique est une nouvelle méthode de mesure qui a une résolution latérale micronique et une résolution verticale nanométrique. Ceci est utile pour l'analyse tri-dimensionnelle des défauts de surface et de la forme des composants dans beaucoup d'applications sur les matériaux massifs et épitaxiés. Dans cet article nous démontrons comment certains défauts peuvent être analysés sur les matériaux et les composants III-V avec deux méthodes interférométriques différentes. La microscopie à saut de phase est mieux adaptée, avec sa résolution de 1 nm et sa meilleure précision, à la mesure des petits défauts de moins de ?/2 en hauteur, ou des surfaces avec des pentes douces et continues, jusqu'à une altitude de 1 ou 2 ?m. Ceci est illustré par les études du polissage de plaquettes d'InP, des défauts sur une couche épitaxiée de GaAs sur InP et des boîtes quantiques sur GaAs. Pour mesurer les motifs, les mésas et les sillons qui ont des marches de plus que ?/2, la microscopie à glissement de franges est le meilleur choix. La résolution verticale est un peu moins bonne que celle de la PSM (4 nm) mais la dynamique verticale est plus grande (15 ?m). Ceci est démontré par les mesures d'un sillon gravé dans une structure laser/détecteur sur une couche quaternaire sur InP et d'un MESFET sur GaAs. En comparaison avec la microscopie électronique et les méthodes de champ proche, la microscopie interférentielle numérique a les avantages de la facilité d'utilisation et de la rapidité. Elle est également capable de résoudre certains problèmes difficiles ou insolubles avec les autres techniques, comme par exemple le profil des sillons étroits, ou la mesure des reliefs enterrés sous une couche transparente. Les inconvénients sont la résolution latérale qui est limitée au pouvoir résolutif de l'objectif et l'introduction d'erreurs liées aux variations des propriétés optiques de l'échantillon qui doivent être prises en compte.

Montgomery, P. C.; Vabre, P.; Montaner, D.; Fillard, J. P.

1993-09-01

53

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

54

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

55

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

56

Effects of Humidity on Non-Hermetically Packaged III-V Structures and Devices  

NASA Technical Reports Server (NTRS)

High humidity and temperature test (known as 85/85 tests) were performed on various III-V devices and structures to determine environmental effects in non-hermetically packaged GaAs membrane mixer diodes.

Leon, R.; Martin, S.; Lee, T.; Okuno, J.; Ruiz, R.; Gauldin, R.; Gaidis, M.; Smith, R.

1999-01-01

57

Hydrogen incorporation into III-V nitrides during processing  

SciTech Connect

Hydrogen is readily incorporated into GaN and related alloys during wet and dry etching, chemical vapor deposition of dielectric overlayers, boiling in water and other process steps, in addition to its effects during MOCVD or MOMBE growth. The hydrogen is bound at defects or impurities and passivates their electrical activity. Reactivation occurs at 450-550{degrees}C, but evolution from the crystal requires much higher temperatures ({ge} 800{degrees}C).

Pearton, S.J.; Abernathy, C.R.; Vartuli, C.B. [Univ. of Florida, Gainesville, FL (United States)] [and others

1995-10-01

58

Integration of III-V compound semiconductors on silicon MEMS structures  

Microsoft Academic Search

We have exploited several technologies to integrating III-V compound semiconductors on silicon-based MEMS structures. They included utilizing silicon nano-structures as compliant substrates to improve the quality of heteroeptaxial III-V semiconductors on silicon; building optical active devices on MEMS; and using a MEMS micro-instrument for testing the optical properties of OMVPE thin films. A light emitting tip-array has been fabricated by

Yan Wang

2000-01-01

59

Strategic Options for a Led-Like Approach in III-V Concentrator Photovoltaics  

Microsoft Academic Search

Well-designed strategies are required in order to push III-V concentration to low cost scenarios that beat the prices of the already existing silicon-based concentration systems operating at 250-400 suns. Several laboratories and pilot production lines are starting to use in III-V solar cells similar approaches than those used for LEDs (Light Emitting Diodes). We firstly proposed the so-called \\

C. Algora; I. Rey-Stolle; B. Galiana; J. R. Gonzalez; M. Baudrit; I. Garcia

2006-01-01

60

Structural and electronic properties of monolayer hydrogenated honeycomb III-V sheets from first-principles  

NASA Astrophysics Data System (ADS)

Using first-principles calculations, we investigate the structural and electronic properties of monolayer hydrogenated honeycomb III-V sheets. The lattice constants and cohesive energies of the hydrogenated III-V (XY H 2, X=B, Al, Ga, and Y =N, P, As) sheets depend on the III-V elements and follow the same trend as the atomic radii of the elements. We find that the short lattice constants correspond to the large cohesive energies of the hydrogenated III-V sheets. Similar to the graphane sheet, the hydrogenated BP and BAs sheets prefer the chair conformation. While for the hydrogenated BN, AlN, AlP, and GaN sheets, the boat conformation is favored. For the hydrogenated AlAs, GaP, and GaAs sheets, the chair and boat conformations are degenerate structures. We obtain that all the hydrogenated III-V sheets are wide-gap semiconductors. With GW corrections, the band gaps of hydrogenated III-V sheets follow the order of nitrogen > phosphorous > arsenic compounds for both the chair and boat conformations.

Wang, Yanli; Shi, Siqi

2010-08-01

61

Scanning transmission electron microscopy study of III-V nitrides  

NASA Astrophysics Data System (ADS)

A study of the electronic properties of the III-V nitrides and the characterization of nitride-based heterostructures, interfaces and quantum wells using scanning transmission electron microscopy (STEM) are presented. Examination of the epitaxially grown GaN/Al0.25Ga0.75N heterostructure shows that, in contrast to expectations, the interface between GaN buffer and Al0.25Ga0.75N barrier is not atomically sharp, but diffuse. High spatial resolution electron energy loss spectroscopy measurements and annular dark field imaging indicate that these interfaces can be up to 20 A wide. The effects of the presence of the diffuse interface between the GaN and AlxGa1- xN layers on formation of the quasi-two-dimensional electron gas at the heterointerface are studied. Electronic energy levels and the distribution of these highly localized electrons at the interface are calculated for different interface widths and for various physical parameters of the structure. The long-range and atomic level uniformities of the GaN quantum wells grown in an AlN matrix are characterized using electron energy loss spectroscopy and annular dark field imaging. The effects of the incident electron beam broadening inside the specimen on STEM measurements are discussed and mechanisms to minimize them are suggested. For quantitative correlation, the measured intensity of the nitrogen K-edge is compared with the propagating beam intensity obtained from multislice calculations. Possible effects of strain in the structure on its electronic states and energy-loss spectra are predicted. The electron-beam-induced damage of the wurtzite InN in STEM is studied and knock-on type damage with ejection of nitrogen atoms from a sample is observed. From comparison of the measured integrated intensity of the nitrogen K-edge and indium M4,5-edge with a calculated mass-loss model the vacancy-enhanced displacement energy for nitrogen atoms in InN is obtained. Investigations of the electronic structure of the wurtzite InN are carried out and excellent agreement between measured spectra of the nitrogen K-edge and the indium M4,5 -edge and corresponding nitrogen 2p and the indium 5p partial density of states (DOS) of the conduction band is obtained. The calculations of DOS are performed using density functional theory (DFT). DFT calculations of nitrogen 2p partial DOS of the conduction band in strained and relaxed wurtzite InN combined with multiple scattering x-ray absorption near edge structure calculations of the corresponding nitrogen K-edge spectra suggest that a strong modification of the electronic structure should be expected in epitaxially grown multilayer structures when a significant mismatch in lattice constants between layers is present.

Mkhoyan, Karen Andre

62

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

63

Development of III-V p-MOSFETs with high-kappa gate stack for future CMOS applications  

NASA Astrophysics Data System (ADS)

As the semiconductor industry approaches the limits of traditional silicon CMOS scaling, non-silicon materials and new device architectures are gradually being introduced to improve Si integrated circuit performance and continue transistor scaling. Recently, the replacement of SiO2 with a high-k material (HfO2) as gate dielectric has essentially removed one of the biggest advantages of Si as channel material. As a result, alternate high mobility materials are being considered to replace Si in the channel to achieve higher drive currents and switching speeds. III-V materials in particular have become of great interest as channel materials, owing to their superior electron transport properties. However, there are several critical challenges that need to be addressed before III-V based CMOS can replace Si CMOS technology. Some of these challenges include development of a high quality, thermally stable gate dielectric/III-V interface, and improvement in III-V p-channel hole mobility to complement the n-channel mobility, low source/drain resistance and integration onto Si substrate. In this thesis, we would be addressing the first two issues i.e. the development high performance III-V p-channels and obtaining high quality III-V/high-k interface. We start with using the device architecture of the already established InGaAs n-channels as a baseline to understand the effect of remote scattering from the high-k oxide and oxide/semiconductor interface on channel transport properties such as electron mobility and channel electron concentration. Temperature dependent Hall electron mobility measurements were performed to separate various scattering induced mobility limiting factors. Dependence of channel mobility on proximity of the channel to the oxide interface, oxide thickness, annealing conditions are discussed. The results from this work will be used in the design of the p-channel MOSFETs. Following this, InxGa1-xAs (x>0.53) is chosen as channel material for developing p-channel MOSFETs. Band engineering, strain induced valence band splitting and quantum confinement is used to improve channel hole mobility. Experimental results on the Hall hole mobility is presented for InxGa1-xAs channels with varying In content, thickness of the quantum well and temperature. Then, high mobility InxGa 1-xAs heterostructure thus obtained are integrated with in-situ deposited high-k gate oxide required for high performance p-MOSFET and discuss the challenges associated with the gated structure and draw conclusions on this material system. Antimonide based channel materials such as GaSb and InxGa 1-xSb are explored for III-V based p-MOSFETs in last two chapters. Options for Sb based strained QW channels to obtain maximum hole mobility by varying the strain, channel and barrier material, thickness of the layers etc. is discussed followed by the growth of these Sb channels on GaAs and InP substrates using molecular beam epitaxy. The physical properties of the structures such as the heterostructure quality, alloy content and surface roughness are examined via TEM, XRD and AFM. Following this, electrical measurement results on Hall hole mobility is presented. The effect of strain, alloy content, temperature and thickness on channel mobility and concentration is reported. Development of GaSb n- and p-MOS capacitor structures with in-situ deposited HfO2 gate oxide dielectric using in-situ deposited amorphous Si (a-Si) interface passivation layer (IPL) to improve the interface quality of high-k oxide and (In)GaSb surface is presented. In-situ deposited gate oxides such as Al2O3 and combination oxide of Al 2O3 and HfO2 with and without the a-Si IPL are also explored as alternate gate dielectrics. Subsequently, MOS capacitor structures using buried InGaSb QWs are demonstrated. Development of an inversion type bulk GaSb with implanted source-drain contacts and in-situ deposited gate oxide HfO2 gate oxide is discussed. The merits of biaxial compressive strain is demonstrated on strained surface and buried channel In0.36 Ga0.64Sb QW MOSFETs with thin top

Nagaiah, Padmaja

64

III-V complementary metal-oxide-semiconductor electronics on silicon substrates.  

PubMed

One of the major challenges in further advancement of III-V electronics is to integrate high mobility complementary transistors on the same substrate. The difficulty is due to the large lattice mismatch of the optimal p- and n-type III-V semiconductors. In this work, we employ a two-step epitaxial layer transfer process for the heterogeneous assembly of ultrathin membranes of III-V compound semiconductors on Si/SiO(2) substrates. In this III-V-on-insulator (XOI) concept, ultrathin-body InAs (thickness, 13 nm) and InGaSb (thickness, 7 nm) layers are used for enhancement-mode n- and p- MOSFETs, respectively. The peak effective mobilities of the complementary devices are ?1190 and ?370 cm(2)/(V s) for electrons and holes, respectively, both of which are higher than the state-of-the-art Si MOSFETs. We demonstrate the first proof-of-concept III-V CMOS logic operation by fabricating NOT and NAND gates, highlighting the utility of the XOI platform. PMID:22694195

Nah, Junghyo; Fang, Hui; Wang, Chuan; Takei, Kuniharu; Lee, Min Hyung; Plis, E; Krishna, Sanjay; Javey, Ali

2012-07-11

65

A developed Ullmann reaction to III-V semiconductor nanocrystals in sealed vacuum tubes.  

PubMed

Group III-V (13-15, III = Ga, In, and V = P, As) semiconductor nanocrystals were effectively obtained via a developed Ullmann reaction route through the reactions of preformed nanoscale metallic indium or commercial gallium with triphenylphosphine (PPh(3)) and triphenylarsine (AsPh(3)) in sealed vacuum quartz tubes under moderate conditions at 320-400 degrees C for 8-24 h. The developed synthetic strategy in sealed vacuum tubes extends the synthesis of III-V semiconductor materials, and the air-stable PPh(3) and AsPh(3) with low toxicity provide good alternative pnicogen precursors for the synthesis of III-V nanocrystals. The analysis of XRD, ED and HRTEM established the production of one-dimensional (1D) metastable wurtzite (W) InP, InAs and GaP nanostructures in the zinc blende (ZB) products. Further investigations showed that 1D W nanostructures resulted from kinetic effects under the moderate synthetic conditions employed and the steric effect of PPh(3) and AsPh(3), and that the tendency for the synthesis of III-V nanocrystals was in the orders of IIIP > IIIAs and GaV > InV on the basis of experiments and thermodynamic calculations. Meanwhile, the microstructures and growth mechanism of the III-V nanocrystals were investigated. PMID:19082064

Wang, Junli; Yang, Qing

2008-11-21

66

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

SciTech Connect

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, E-mail: s.prucnal@hzdr.de; Zhou, Shengqiang; Ou, Xin; Facsko, Stefan; Oskar Liedke, Maciej; Bregolin, Felipe; Liedke, Bartosz; Grebing, Jochen; Fritzsche, Monika; Hübner, Rene; Mücklich, Arndt; Rebohle, Lars; Skorupa, Wolfgang [Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstr. 400, 01328 Dresden (Germany); Helm, Manfred [Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstr. 400, 01328 Dresden (Germany); Center for Advancing Electronics Dresden (CFAED), Technische Universität Dresden, 01062 Dresden (Germany); Turek, Marcin; Drozdziel, Andrzej [Maria Curie-Sklodowska University, Pl. M. Curie-Sklodowskiej 1, 20-035 Lublin (Poland)

2014-02-21

67

Methods for forming group III-V arsenide-nitride semiconductor materials  

NASA Technical Reports Server (NTRS)

Methods are disclosed for forming Group III--arsenide-nitride semiconductor materials. Group III elements are combined with group V elements, including at least nitrogen and arsenic, in concentrations chosen to lattice match commercially available crystalline substrates. Epitaxial growth of these III-V crystals results in direct bandgap materials, which can be used in applications such as light emitting diodes and lasers. Varying the concentrations of the elements in the III-V crystals varies the bandgaps, such that materials emitting light spanning the visible spectra, as well as mid-IR and near-UV emitters, can be created. Conversely, such material can be used to create devices that acquire light and convert the light to electricity, for applications such as full color photodetectors and solar energy collectors. The growth of the III-V crystals can be accomplished by growing thin layers of elements or compounds in sequences that result in the overall lattice match and bandgap desired.

Major, Jo S. (Inventor); Welch, David F. (Inventor); Scifres, Donald R. (Inventor)

2000-01-01

68

Relaxation Models of the (110) Zinc-Blende III-V Semiconductor Surfaces: Density Functional Study  

SciTech Connect

Clean III-V zinc-blende (110) surfaces are the most extensively studied semiconductor surface. For conventional III-V compounds such as GaAs and InP, the surface relaxation follows a bond rotation relaxation model. However, for III-nitrides recent study indicates that they follow a bond-constricting relaxation model. First-principles atom relaxation calculations are performed to explore the origin of the difference between the two groups of materials. By analyzing the individual shift trends and ionic properties of the top layer anions and cations, we attribute the difference between the conventional and nitride III-V compounds to the strong electronegativity of N, which leads to the s{sup 2}p{sup 3} pyramid bond angle to be larger than the ideal one in bulk (109.5{sup o}). The general trends of the atomic relaxation at the III-nitrides (110) surfaces are explained.

Ye, H.; Chen, G.; Wu, Y.; Zhu, Y.; Wei, S. H.

2008-11-01

69

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

70

Light emission and enhanced nonlinearity in nanophotonic waveguide circuits by III-V/silicon-on-insulator heterogeneous integration  

NASA Astrophysics Data System (ADS)

The heterogeneous integration of a III-V thin film on top of a silicon-on-insulator (SOI) optical waveguide circuit by means of adhesive divinylsiloxane-benzocyclobutene (DVS-BCB) die-to-wafer bonding is demonstrated, thereby achieving light emission and enhanced nonlinearity in ultracompact SOI cavities. This approach requires ultrathin DVS-BCB bonding layers to allow the highly confined optical mode to overlap with the bonded III-V film. The transfer of sub-100-nm III-V layers using a 65 nm DVS-BCB bonding layer onto SOI racetrack resonator structures is demonstrated. Spontaneous emission coupled to a SOI bus waveguide, spectrally centered around the resonator resonances, is observed by optically pumping the III-V layer. Strong carrier-induced nonlinearities are observed in the transmission characteristics of the III-V/SOI resonator structure. The all-optical control of an optical signal in these III-V/SOI resonators is demonstrated.

Roelkens, G.; Liu, L.; Van Thourhout, D.; Baets, R.; Nötzel, R.; Raineri, F.; Sagnes, I.; Beaudoin, G.; Raj, R.

2008-08-01

71

Hybrid III-V on silicon lasers for photonic integrated circuits on silicon  

NASA Astrophysics Data System (ADS)

Silicon photonics is attracting large attention due to the promise of fabricating low-cost, compact circuits that integrate photonic and microelectronic elements. It can address a wide range of applications from short distance data communication to long haul optical transmission. Today, practical Si-based light sources are still missing, despite the recent demonstration of an optically pumped germanium laser. This situation has driven research to the heterogeneous integration of III-V semiconductors on silicon through wafer bonding techniques. This paper reports on recent advances on integrated hybrid InP/SOI lasers and transmitters using a wafer bonding technique made in particular at III-V Lab, France.

Duan, Guang-Hua; Jany, Christophe; Le Liepvre, Alban; Accard, Alain; Lamponi, Marco; Make, Dalila; Kaspar, Peter; Levaufre, Guillaume; Girard, Nils; Lelarge, François; Fedeli, Jean-Marc; Messaoudene, Sonia; Bordel, Damien; Olivier, Segolene

2014-02-01

72

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.

73

Performance of CPV system using three types of III-V multi-junction solar cells  

NASA Astrophysics Data System (ADS)

Performance of III-V multi-junction solar cells depends on spectral conditions according to which junction limits the photocurrent. Specifically, the response of concentrating multi-junction solar cells depends on the illumination at the cell surface. Because the illumination condition depends on alignment, it is important to characterize the CPV performance not only for a mono-module but also for a system or an array. In this paper the spectral effect on the CPV system and the mono-module consisting of III-V multi-junction solar cells from three different manufactures will be discussed.

Hashimoto, Jun; Kurtz, Sarah; Sakurai, Keiichiro; Muller, Matthew; Otani, Kenji

2012-10-01

74

Buried dislocation networks designed to organize the growth of III-V semiconductor nanostructures  

E-print Network

1 Buried dislocation networks designed to organize the growth of III-V semiconductor nanostructures Laboratoire de Photonique et de Nanostructures, CNRS, Route de Nozay, F-91460 Marcoussis, France We first by such DNs has been used to pilot the lateral ordering of GaAs and InGaAs nanostructures during metalorganic

Paris-Sud XI, Université de

75

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

76

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

77

Hybrid silicon evanescent laser fabricated with a silicon waveguide and III-V offset quantum wells  

E-print Network

Hybrid silicon evanescent laser fabricated with a silicon waveguide and III-V offset quantum wells: A novel laser that utilizes a silicon waveguide bonded to AlGaInAs quantum wells is demonstrated. This wafer scale fabrication approach allows the optical waveguide to be defined by CMOS-compatible silicon

Bowers, John

78

Quantum Chemical Study of Arsenic (III, V) Adsorption on Mn-Oxides  

E-print Network

(As)isatoxicelementwithamaximumconcentration levelindrinkingwatersetto10ppbbytheU.S.Environmental Protection Agency. Arsenic contamination results from bothQuantum Chemical Study of Arsenic (III, V) Adsorption on Mn-Oxides: Implications for Arsenic-MnOOH) during As(III) oxidation. Introduction Arsenic

Sparks, Donald L.

79

Degradation of III-V inversion-type enhancement-mode MOSFETs  

E-print Network

telegraph noise appears at the gate, which seems to be not correlated with the soft breakdowns commonly gate ramp voltage stress on III-V InGaAs based MOSFETs. Stress induces trapped charge and it also leads to interface trap generation, which has detrimental effects on the subthreshold slope

Ye, Peide "Peter"

80

Transient transport in central-valley-dominated ternary III V alloys  

NASA Astrophysics Data System (ADS)

This paper describes results of an ensemble Monte Carlo study of ballistic transport and velocity overshoot in Al 0.25In 0.75As and Ga 0.4In 0.6As. Velocity overshoot in these materials is limited primarily by transport properties of the central valley. The transfer of carriers into higher-lying energy valleys occurs only after velocity overshoot has subsided. Instantaneous conduction-band occupancies, carrier positions, and carrier velocities are given as functions of time for electric field intensities of 10 and 40 kV/cm. These curves show that transient velocities exceed steady-state values by as much as 27 to one, that these transients persist over distances ranging from 0.22 to 0.79 ?m, and that average velocities during velocity overshoot are as large as 5.6 × 10 7 cm/sec. These results have important implications for submicron-device applications of these materials.

Massengill, L. W.; Glisson, T. H.; Hauser, J. R.; Littlejohn, M. A.

1986-07-01

81

Bismuth containing III-V quaternary alloy InGaAsBi grown by MBE  

NASA Astrophysics Data System (ADS)

InGaAsBi epilayers were created on InP substrates by molecular beam epitaxy for the first time. The high crystalline quality of the InGaAsBi epilayer with smooth interface was confirmed by high resolution X-ray diffraction measurements. Up to 2.5% Bi was incorporated in the film based on Rutherford back scattering (RBS) results. The RBS channeling spectra give clear evidence that the Bi atoms were substitutionally located in the InGaAs zinc-blende lattice sites.

Feng, G.; Oe, K.; Yoshimoto, M.

2006-09-01

82

The metal grating design of plasmonic hybrid III-V/Si evanescent lasers.  

PubMed

A hybrid III-V/silicon laser design with a metal grating layer inserted in between is proposed and numerically studied. The metal grating layer is buried in a silicon ridge waveguide surrounded by silicon dioxide, and its structural parameters such as periodicity, width and depth can be varied for optimization purpose. The plasmonic effect originated from the grating layer can manage optical fields between III-V and silicon layers in hopes of dimension reduction. The substrate is planarized to minimize the bonding failure. A numerical algorithm with various combinations of metal grating and waveguide structural parameters was created and the optimal design with 730 nm grating period and 600 nm of buried waveguide ridge height was obtained by minimizing the corresponding laser threshold. With top AlInGaAs quantum wells and optimized design of hybrid metal/silicon waveguide, a 0.6 ?m(-1) threshold gain can be achieved. PMID:24105566

Hsu, Min-Hsiang; Lin, Chien-Chung; Kuo, Hao-Chung

2013-08-26

83

To the understanding of the formation of the droplet-epitaxial III-V based nanostructures  

SciTech Connect

In this work, we discuss the evolution of the self-assembling III-V based nanostructures. These nano-structures were prepared by droplet epitaxial technique. The different nanostructures such as quantum dot, quantum ring, double quantum ring, or nanohole form similarly from an initial Ga droplet but under different substrate temperature and various arsenic pressures. Started from few atomic courses, we give here a qualitative description of the key processes for all of the aforementioned nanostructures.

Nemcsics, Ákos [Institute for Microelectronics and Technology, Óbuda University, Tavaszmez? u. 17. H-1084 Budapest, Hungary and Research Institute for Technical Physics and Materials Science, Hungarian Academy of Sciences, P.O. Box 49. H-1525 Budapest (Hungary)

2014-05-15

84

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

85

Lattice-mismatched approaches for high-performance, III-V photovoltaic energy converters  

Microsoft Academic Search

We discuss lattice-mismatched (LMM) approaches utilizing compositionally step-graded layers and buffer layers that yield III-V photovoltaic devices with performance parameters equaling those of similar lattice-matched (LM) devices. Our progress in developing high-performance, LMM, InP-based GaInAs\\/InAsP materials and devices for thermophotovoltaic (TPV) energy conversion is highlighted. A novel, monolithic, multi-bandgap, tandem device for solar PV (SPV) conversion involving LMM materials is

M. W. Wanlass; S. P. Ahrenkiel; R. K. Ahrenkiel; D. S. Albin; J. J. Carapella; A. Duda; J. F. Geisz; S. Kurtz; T. Moriarty; R. J. Wehrer; B. Wernsman

2005-01-01

86

Bonding principles of passivation mechanism at III-V-oxide interfaces  

NASA Astrophysics Data System (ADS)

We analyze the conditions necessary to passivate interfacial defects at III-V-oxide interfaces, in terms of an electron-counting rule. We propose that this rule, previously used to describe reconstructions at GaAs or ZnSe surfaces, acts during oxide growth or deposition, atomic layer by atomic layer. The need to satisfy this rule continuously drives the creation of interface defects, whose states can lie in the bulk band gap of the semiconductor.

Robertson, J.; Lin, L.

2011-11-01

87

Process for forming shaped group III-V semiconductor nanocrystals, and product formed using process  

DOEpatents

A process for the formation of shaped Group III-V semiconductor nanocrystals comprises contacting the semiconductor nanocrystal precursors with a liquid media comprising a binary mixture of phosphorus-containing organic surfactants capable of promoting the growth of either spherical semiconductor nanocrystals or rod-like semiconductor nanocrystals, whereby the shape of the semiconductor nanocrystals formed in said binary mixture of surfactants is controlled by adjusting the ratio of the surfactants in the binary mixture.

Alivisatos, A. Paul (Oakland, CA); Peng, Xiaogang (Fayetteville, AR); Manna, Liberato (Palo del Colle, IT)

2001-01-01

88

Advances in III-V based photonic crystals for integrated optical processing  

Microsoft Academic Search

Compactness, massive integration of multiple functions on a single chip and power consumption are crucial for transmission of large aggregated bit rates at short distance. Efficient implementation of data processing at the optical level are very attractive. Here we present a technology for implementing ultra-fast switching with recordlow energy·recovery time product. We developed high-quality photonic crystal micro-resonators based on III-V

Sylvain Combrié; Pierre Colman; Chad Husko; Quynh Vy Tran; Alfredo de Rossi

2010-01-01

89

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

90

Studies of high DC current induced degradation in III-V nitride based heterojunctions  

Microsoft Academic Search

We report experiments on high dc current stressing in commercial III-V nitride based heterojunction light-emitting diodes. Stressing currents ranging from 100 mA to 200 mA were used. Degradations in the device properties were investigated through detailed studies of the current-voltage (I-V) characteristics, electroluminescence, deep-level transient Fourier spectroscopy and flicker noise. Our experimental data demonstrated significant distortions in the I-V characteristics

W. Y. Ho; Charles Surya; K. Y. Tong; L. W. Lu; W. K. Ge

2000-01-01

91

Nonlinear Landau absorption in III-V semiconductors near the fundamental absorption edge  

Microsoft Academic Search

Analytical investigations have been made of nonlinear Landau absorption in important III-V semiconductors such as GaAs, GaSb, InSb, and InAs which have been irradiated by suitable lasers of photon energies (homega) nearly equal to the band-gap energies (homegag) in the presence of a large magnetostatic field. A coherent radiation-exciton interaction model has been used for the direct allowed transitions between

P. K. Sen

1986-01-01

92

Optical Absorption, Emission, and Modulation in Iii-V Semiconductor Quantum Well Structures  

Microsoft Academic Search

An experimental study of topics relating to optical absorption, emission, and modulation in III-V semiconductor GaAs\\/AlGaAs quantum well structures is presented. Several novel quantum well structures are examined and evaluated for use in electrooptic modulators, laser diodes, and monolithically integrated laser diodes and passive waveguides. The design of the epitaxial structures, the molecular beam epitaxy growth, the optical characterization of

Steven Marc Shank

1993-01-01

93

Excitonic contribution to the optical absorption in zinc-blende III-V semiconductors  

Microsoft Academic Search

The imaginary part of the dielectric function of zinc-blende III-V semiconductors in the vicinity of the direct absorption edge was calculated using the kp model of the band structure and the Elliott's theory of excitonic absorption. From comparison to the experimental data, we found that the excitonic contribution is to be weighted in favor of the band-to-band transitions by a

S. Shokhovets; G. Gobsch; O. Ambacher

2006-01-01

94

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

95

Fatigue failure of concentrator III-V solar cells - Does forward bias current injection really kill III-V CPV cells?  

NASA Astrophysics Data System (ADS)

CPV cells are successively exposed by cycles of concentrated sunlight and huge cycling current flows out of contacts. The purpose of this research is to identify if the fatigue will be one of the life-end and wearing modes of CPV cells and how long the life-time will be. One of the best ways of giving cycling stress on cells and contacts is cycling forward bias injection. First, it is important to investigate if forward bias itself damages concentrator III-V cells. To confirm the forward bias current itself does not damage the CPV solar cells but cycling does, we applied 4 times of Isc continuously in 500 hours, equivalently total injection of 90,000 cycles, but no damage or degradation was observed. What's more, we applied the cycling test after the stress of 500 hour continuous forward bias injection. We did not identify any changes between groups of with stress of continuous forward bias and without them. On-Off tests giving forward bias current as high as 4 times of Isc are conducted. The failure was analyzed by the Weible function. About 2,000 cells in total were examined. A small number of initial failure, that of failure number of cycles lied along exponential distribution and distinct portion of wear mode failure that of failure number of cycles lied along Gaussian distribution were identified. The EL measurement indicated that all the damaged cells in wear mode were local shunt under the top contacts suggesting stress under the top contacts would be possibly responsible to the fatigue failure. Advanced contact design that leads to reduce the stress on the top contact is expected to prolong the lifetime of the III-V concentrator cells.

Araki, Kenji; Nagai, Hirokazu; Tamura, Kazuyuki

2012-10-01

96

The path to stoichiometric composition of III–V binary quantum dots through plasma\\/ion-assisted self-assembly  

Microsoft Academic Search

Semiconductor III–V quantum dots (QDs) are particularly enticing components for the integration of optically promising III–V materials with the silicon technology prevalent in the microelectronics industry. However, defects due to deviations from a stoichiometric composition [group III: group V=1] may lead to impaired device performance. This paper investigates the initial stages of formation of InSb and GaAs QDs on Si(100)

A. E. Rider; K. Ostrikov

2009-01-01

97

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

98

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

NASA Astrophysics Data System (ADS)

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.

2002-10-01

99

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

100

Electronic structure and v alence of Mn imputiries in III-V semiconductors  

NASA Astrophysics Data System (ADS)

Substitutional Mn impurities in III-V semiconductors can acquire either a divalent or a trivalent configuration. For example, it is generally accepted that Mn in GaAs is in a (d^5+h) configuration with five occupied Mn d-orbitals and a delocalized hole in the valence band. In contrast, Mn in GaN is believed to be in a d^4 configuration with a deep impurity state that has d-character. But there have recently been some discussions about the possibility of having some Mn ion in GaN assuming a divalent (d^5+h) type configuration. In order to achieve carrier induced ferromagnetism, the desired state of the Mn ions in III-V semiconductors is the (d^5+h) configuration. We have therefore performed ab-initio calculations of the Mn valence when it substitutes Ga in various III-V semiconductor hosts. We use the self-interaction corrected local spin density (SIC-LSD) method which is able to treat localized impurity orbitals properly. In particular we find that the method is capable of predicting the (d^5+h) state of Mn in GaAs. For Mn in GaP and GaN the calculations predict a trivalent d^4 state in the idealized system. The energy differences between d^4 and (d^5+h) configurations in GaP are, however, very small. Introduction of defects or donors doe change the valence of Mn in GaP, favoring the divalent state under certain circumstances. Work supported by the Defense Advanced Research Project Agency and by the Division of Materials Science and Engineering, U.S. Department of Energy, under Contract DE-AC05-00OR22725 with UT-Battelle LLC.

Schulthess, T. C.; Temmerman, W.; Szotek, Z.; Stocks, G. M.; Butler, W. H.

2004-03-01

101

Ultraviolet photodetectors and imaging arrays based on III-V nitride heterostructures  

NASA Astrophysics Data System (ADS)

The III-V nitride class of compound semiconductors has received much attention in the last decade. These materials have a wide, direct bandgap, making them a prime candidate for optoelectronic devices in the blue, green, and ultraviolet spectral regions. These materials exhibit impressive optical, electrical, and thermal properties, even though there are fundamental materials issues that are thus far unresolved. This work explores the application of III-V nitride semiconductors to optical detectors in the ultraviolet region of the electromagnetic spectrum. Metalorganic vapor phase epitaxy was used to synthesize thin film p-i-n photodiode structures on double side polished sapphire substrates; these films were characterized for optical, electrical and structural properties. The grown structures were designed to respond to a predetermined region of the UV spectrum when illuminated from the substrate side. These structures were fabricated into devices using generally accepted techniques for dry etching and p and n-contact metallizations. Test devices were characterized using tools developed by the author. These devices demonstrated as high as 80% quantum efficiency and extremely low dark currents; resulting in spectral detectivities as large as 6 * 1013 cmHz1/2W-1. Devices were designed and demonstrated for a series of detection regions ranging from 365 nm to 250 nm. Photolithography masks were designed to allow the fabrication of photodiode arrays that would hybridize to commercially available CMOS based readout integrated circuits (ROICs), used routinely for infrared photodiode imaging. Photodiode arrays were fabricated and indium bumps were deposited onto the diode contacts and the ROICs to provide electrical connection. The hybrid detector arrays were placed in leadless chip carriers, wirebonded, and connected to commercially available drive and readout circuitry. Images of UV scenes were focused onto the arrays using fused quartz lenses. These images and movies were successfully collected at frame rates up to 240 Hz using both 32 x 32 and 128 x 128 III-V nitride based UV photodiode imagers.

Brown, Jeffrey David

2000-10-01

102

Temperature dependence of threshold current in III-V semiconductor lasers: Experimental prediction and explanation  

SciTech Connect

The newly developed differential carrier lifetime and threshold carrier density measurement techniques are applied to temperature-dependent measurements of the recombination rates and threshold carrier density of III-V semiconductor lasers. Quantities obtained from these measurements are used to predict the temperature dependence T/sub 0/ of the threshold current, which is in excellent agreement with T/sub 0/ observed at 20 /sup 0/C for both InGaAsP and AlGaAs lasers. The main causes for the stronger temperature sensitivity of InGaAsP material are due to Auger recombination and a smaller radiative coefficient.

Su, C.B.; Olshansky, R.; Manning, J.; Powazinik, W.

1984-06-01

103

Spin-induced forbidden evanescent states in III-V semiconductors.  

PubMed

Within the band gap of a semiconductor no electronic propagating states are allowed, but there exist evanescent states which govern charge transport such as tunneling. In this Letter, we address the issue of their spin dependence in III-V semiconductors. Taking into account the spin-orbit interaction, we treat the problem using a k . p 14 x 14 Hamiltonian that we numerically compute for GaAs. Our results show that the removed spin degeneracy in the band gap can lead to giant energy splittings and induces forbidden zones in space where evanescent states are suppressed. PMID:16383929

Rougemaille, N; Drouhin, H-J; Richard, S; Fishman, G; Schmid, A K

2005-10-28

104

Tunable electronic transport properties of metal-cluster-decorated III-V nanowire transistors.  

PubMed

A metal-cluster-decoration approach is utilized to tailor electronic transport properties (e.g., threshold voltage) of III-V NWFETs through the modulation of free carriers in the NW channel via the deposition of different metal clusters with different work function. The versatility of this technique has been demonstrated through the fabrication of high-mobility enhancement-mode InAs NW parallel FETs as well as the construction of low-power InAs NW inverters. PMID:23784849

Han, Ning; Wang, Fengyun; Hou, Jared J; Yip, Sen Po; Lin, Hao; Xiu, Fei; Fang, Ming; Yang, Zaixing; Shi, Xiaoling; Dong, Guofa; Hung, Tak Fu; Ho, Johnny C

2013-08-27

105

General theory of the transverse dielectric constant of III-V semiconducting compounds  

NASA Technical Reports Server (NTRS)

A general model of the transverse dielectric constant of III-V compounds is developed using a hybrid method which combines the kp method with a nonlocal pseudopotential calculation. In this method the Brillouin zone is partitioned into three regions by expanding the energy bands and matrix elements about the F, X, and L symmetry points. The real and imaginary parts of the dielectric constant are calculated as a sum of the individual contributions of each region. By using this partition method, it is possible to get good insight into the dependence of the dielectric constant on the shape of the band structure.

Kahen, K. B.; Leburton, J. P.

1985-01-01

106

Lattice-Mismatched Approaches for High-Performance, III-V Photovoltaic Energy Converters  

SciTech Connect

We discuss lattice-mismatched (LMM) approaches using compositionally step-graded layers and buffer layers that yield III-V photovoltaic devices with performance parameters equaling those of similar lattice-matched (LM) devices. Our progress in developing high-performance, LMM, InP-based GaInAs/InAsP materials and devices for thermophotovoltaic (TPV) energy conversion is highlighted. A novel, monolithic, multi-bandgap, tandem device for solar PV (SPV) conversion involving LMM materials is also presented, along with promising preliminary performance results.

Wanlass, M. W.; Ahrenkiel, S. P.; Ahrenkiel, R. K.; Albin, D. S.; Carapella, J. J.; Duda, A.; Geisz, J. F.; Kurtz, S.; Moriarty, T.; Wehrer, R. J.; Wernsman, B.

2005-02-01

107

III-V/silicon photonic integrated circuits for communication and sensing applications  

NASA Astrophysics Data System (ADS)

In this paper we review our work in the field of heterogeneous integration of III-V semiconductors and non-reciprocal optical materials on a silicon waveguide circuit. We elaborate on the heterogeneous integration technology based on adhesive DVS-BCB die-to-wafer bonding and discuss several device demonstrations. The presented devices are envisioned to be used in photonic integrated circuits for communication applications (telecommunications and optical interconnects) as well as in spectroscopic sensing systems operating in the short-wave infrared wavelength range.

Roelkens, Gunther; Keyvaninia, Shahram; Stankovic, Stevan; De Koninck, Yannick; Tassaert, Martijn; Mechet, Pauline; Spuesens, Thijs; Hattasan, N.; Gassenq, A.; Muneeb, M.; Ryckeboer, E.; Ghosh, Samir; Van Thourhout, D.; Baets, R.

2013-03-01

108

Atomic strings of group IV, III-V, and II-VI elements  

NASA Astrophysics Data System (ADS)

A systematic first-principles study of atomic strings made by group IV, III-V, and II-VI elements has revealed interesting mechanical, electronic, and transport properties. The double bond structure underlies their unusual properties. We found that linear chain of C, Si, Ge, SiGe, GaAs, InSb, and CdTe are stable and good conductor, although their parent diamond (zincblende) crystals are covalent (polar) semiconductors but, compounds SiC, BN, AlP, and ZnSe are semiconductors. First row elements do not form zigzag structures.

Tongay, S.; Durgun, E.; Ciraci, S.

2004-12-01

109

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

110

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

PubMed

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

111

Properties of Group-IV, III-V and II-VI Semiconductors  

NASA Astrophysics Data System (ADS)

Almost all the semiconductors of practical interest are the group-IV, III-V and II-VI semiconductors and the range of technical applications of such semiconductors is extremely wide. The purpose of this book is twofold: * to discuss the key properties of the group-IV, III-V and II-VI semiconductors * to systemize these properties from a solid-state physics aspect The majority of the text is devoted to the description of the lattice structural, thermal, elastic, lattice dynamic, electronic energy-band structural, optical and carrier transport properties of these semiconductors. Some corrective effects and related properties, such as piezoelectric, elastooptic and electrooptic properties, are also discussed. The book contains convenient tables summarizing the various material parameters and the definitions of important semiconductor properties. In addition, graphs are included in order to make the information more quantitative and intuitive. The book is intended not only for semiconductor device engineers, but also physicists and physical chemists, and particularly students specializing in the fields of semiconductor synthesis, crystal growth, semiconductor device physics and technology.

Adachi, Sadao

2005-03-01

112

MOVPE growth of dilute nitride III/V semiconductors using all liquid metalorganic precursors  

NASA Astrophysics Data System (ADS)

Understanding the growth mechanisms of III/V semiconductors containing dilute amounts of N, like (GaIn)(NAs) is necessary as these materials are promising candidates for the active material in several optoelectronic devices, as lasers and solar cells. As one deals with metastable material systems, growth has to be conducted far away from thermodynamic equilibrium with several characteristics emanating from that. This paper summarizes our present understanding of the growth of dilute nitride materials by metal organic vapour phase epitaxy, using exclusively liquid metalorganic precursors. N-incorporation in III/V semiconductors for Ga(NAs) as a model system is predominantly determined by the competition of the group-V elements. Large dependencies of the N-incorporation on crystal composition as well as on strain are observed. Additionally, there are minor effects of gas-phase reactions of metalorganic precursors. The nitrogen uptake of the quaternary material system (GaIn)(NAs)/GaAs is shown to be dominated by In-induced desorption of the nitrogen from the surface, which results in a decrease of N-content, by increasing growth temperature or lowering growth rate.

Volz, Kerstin; Koch, Jörg; Höhnsdorf, Falko; Kunert, Bernardette; Stolz, Wolfgang

2009-04-01

113

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

NASA Astrophysics Data System (ADS)

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.

Tanabe, Katsuaki; Watanabe, Katsuyuki; Arakawa, Yasuhiko

2012-04-01

114

Design and fabrication of optical microcavities using III-V semiconductor-based MOEMS  

NASA Astrophysics Data System (ADS)

The state of the art of III-V semiconductor based MOEMS is presented with a special emphasis on InP and related materials. It is shown that the MOEMS technology can enhance considerably the capabilities of optical micro-cavities, which are considered as a major component for optical signal processing and light generation. Illustrations of the potential of III-V MOEMS are given in the fields of optical telecommunications. Design and fabrication of highly selective and widely tunable optical filters for wavelength division multiplexing systems are presented. These devices are monolithic and are based on surface micro-machining technology. They combine a variety of very attractive properties such as low control power, low insertion loss, tunability, small bandwidth no polarization dependence, simple fiber coupling, no memory effects and reasonable tuning speed. Fiber to fiber transmission characterizations of packaged filters are presented, including bit error rate measurements. Future prospects implying the use of multi-air-gap MOEMS structures as a basic building-block for a wide variety of routing photonic devices are proposed.

Viktorovitch, Pierre; Leclercq, Jean Louis; Goutain, Eric; Rondi, D.

2000-08-01

115

Metal-seeded growth of III-V semiconductor nanowires: towards gold-free synthesis.  

PubMed

Semiconductor nanowires composed of III-V materials have enormous potential to add new functionality to electronics and optical applications. However, integration of these promising structures into applications is severely limited by the current near-universal reliance on gold nanoparticles as seeds for nanowire fabrication. Although highly controlled fabrication is achieved, this metal is entirely incompatible with the Si-based electronics industry. In this Feature we review the progress towards developing gold-free bottom-up synthesis techniques for III-V semiconductor nanowires. Three main categories of nanowire synthesis are discussed: selective-area epitaxy, self-seeding and foreign metal seeding, with main focus on the metal-seeded techniques. For comparison, we also review the development of foreign metal seeded synthesis of silicon and germanium nanowires. Finally, directions for future development and anticipated important trends are discussed. We anticipate significant development in the use of foreign metal seeding in particular. In addition, we speculate that multiple different techniques must be developed in order to replace gold and to provide a variety of nanowire structures and properties suited to a diverse range of applications. PMID:24522389

Dick, Kimberly A; Caroff, Philippe

2014-03-21

116

Calculation of the electron mobility in III-V inversion layers with high-? dielectrics  

NASA Astrophysics Data System (ADS)

We calculate the electron mobility for a metal-oxide-semiconductor system with a metallic gate, high-? dielectric layer, and III-V substrate, including scattering with longitudinal-optical (LO) polar-phonons of the III-V substrate and with the interfacial excitations resulting from the coupling of insulator and substrate optical modes among themselves and with substrate plasmons. In treating scattering with the substrate LO-modes, multisubband dynamic screening is included and compared to the dielectric screening in the static limit and with the commonly used screening model obtained by defining an effective screening wave vector. The electron mobility components limited by substrate LO phonons and interfacial modes are calculated for In0.53Ga0.47As and GaAs substrates with SiO2 and HfO2 gate dielectrics. The mobility components limited by the LO-modes and interfacial phonons are also investigated as a function of temperature. Scattering with surface roughness, fixed interface charge, and nonpolar-phonons is also included to judge the relative impact of each scattering mechanism in the total mobility for In0.53Ga0.47As with HfO2 gate dielectric. We show that InGaAs is affected by interfacial-phonon scattering to an extent larger than Si, lowering the expected performance, but probably not enough to question the technological relevance of InGaAs.

O'Regan, T. P.; Fischetti, M. V.; Sorée, B.; Jin, S.; Magnus, W.; Meuris, M.

2010-11-01

117

III-V multiple quantum well long-wavelength infrared detectors  

NASA Astrophysics Data System (ADS)

Quantum well infrared photodetectors (QWIP), based on intersubband absorption in III-V multiple quantum well (MQW) structures, have advanced considerably in the last several years for infrared detection in the spectral regions 3-5 mum and 8-12 mum. This investigation explored the molecular beam epitaxially grown n-type GaAs/AlGaAs, p-type lattice matched InGaAs/InP, and n-type lattice matched InGaAs/InP III-V intersubband photodetectors. In addition, the intermixed wavelength shifted n-type GaAs/AlGaAs QWIP is explored as well as the linear grating 4 x 2 focal plane array. Furthermore, device characteristics of n-type GaAs/AlGaAs quantum well infrared photodetector on GaAs-on-Si substrate is presented. A comprehensive set of experiments was conducted on QWIP fabricated from both as-grown and intermixed multiple quantum well structures. Intermixing of the MQW was achieved by dielectric encapsulating (SiOsb2) the surface. A shift in the peak response wavelength and a broadening of the photoresponse spectrum was demonstrated for the intermixed n-type GaAs/AlGaAs QWIP. Red-shifts on the order of {˜}1.42 mum and {˜}0.8 mum were observed for the room-temperature absorption and low-temperature photoresponses, respectively. In addition, the noise performance resulted in a detectivity which is five times lower than that of QWIP, fabricated from as-grown structures. Despite the large lattice mismatch, 8.41 mum n-type GaAs/AlGaAs QWIP, on GaAs-on-Silicon substrate were fabricated. The devices were experimentally characterized by measurements of the dark current, spectral response, and absolute responsivity. The detector structure exhibited dark current and absolute responsivity comparable to a similar detector structure grown on a GaAs substrate, while displaying a small blue shift in the spectral response. Also, detection at 4.55 mum in the mid-wavelength infrared band was observed for an ultra-short ({˜}10A) p-type InGaAs/InP QWIPs which, complimented by the high responsivity 8.93 mum n-type InGaAs/InP QWIP, offers the possibility of a two-color QWIPs on the same InP substrate. The results of the research provide information of III-V intersubband optoelectronic properties which are fundamental to the future sensitive, low-cost, large long wavelength infrared focal-plane arrays.

Sengupta, Deepak Kumar

118

Progressive materials integration: III-V on insulator by wafer bonding  

NASA Astrophysics Data System (ADS)

The development of wafer bonded III-V on insulator structures aims to provide advancements in high-speed electronic applications such as High Electron Mobility Transistors. This study demonstrates the feasibility of hydrogen exfoliated template layers for the growth III-V based device structures. InP layers are transferred to GaAs substrates to assess the suitability of the InP layer as a template for metal-organic vapor phase epitaxial growth. Strong, large area bonds between III-V wafers are achieved using SiN intermediate layers, which provide robust structures at high temperatures. The bonding mechanisms of SiN layers with a short oxygen plasma exposure are found to mimic those of SiO2. These bonds are strong enough to withstand thermal strain imposed by bonded wafers that exhibit appreciable coefficient of thermal expansion mismatch, such as InP and GaAs. These bonded wafers exhibit some stability against defect formation for low thermal strains. However, depending upon the thermal expansion coefficient mismatch and required thermal processing, misfit dislocations can form to relieve this thermal strain. Careful control of both template thickness and annealing temperatures leads to a stable template for subsequent epitaxial growth. Once bonding is complete, the template layer is separated from the bulk by a technique of hydrogen ion implantation and exfoliation. The layer exfoliation from a hydrogen implanted InP substrate is facilitated by the formation of extended defects in a certain temperature regime due to hydrogen trapping. Subsequently increasing the temperature produces rapid planar exfoliation. This two-step annealing scheme simultaneously allows the wafer bond to strengthen during the low temperature defect nucleation phase. After exfoliation, the surface of the template layer is generally very rough, therefore a chemical mechanical polishing step was developed to planarize this layer for subsequent epitaxial growth. Damage-free planarization of the transferred InP layer is achieved with an abrasive free sodium hypochlorite and citric acid solution. The hydrogen implantation process is found to induce crystalline damage throughout the thickness of the transferred layer. This ion damage does not initiate any extended defects into subsequent epitaxial layers; however, a slight mosaic tilt is propagated. The electronic properties of the epitaxial layers grown on these template layers are largely affected by the final surface preparation. The optimized CMP process provides planarization, however, a post-CMP HCl etch improves the surface and produces a high quality growth.

Hayashi, Sumiko Lynn

119

Temperature dependence of defect-related photoluminescence in III-V and II-VI semiconductors  

SciTech Connect

Mechanisms of thermal quenching of photoluminescence (PL) related to defects in semiconductors are analyzed. We conclude that the Schön-Klasens (multi-center) mechanism of the thermal quenching of PL is much more common for defects in III–V and II–VI semiconductors as compared to the Seitz-Mott (one-center) mechanism. The temperature dependencies of PL are simulated with a phenomenological model. In its simplest version, three types of defects are included: a shallow donor, an acceptor responsible for the PL, and a nonradiative center that has the highest recombination efficiency. The case of abrupt and tunable thermal quenching of PL is considered in more detail. This phenomenon is predicted to occur in high-resistivity semiconductors. It is caused by a sudden redirection of the recombination flow from a radiative acceptor to a nonradiative defect.

Reshchikov, Michael A., E-mail: mreshchi@vcu.edu [Department of Physics, Virginia Commonwealth University, Richmond, Virginia 23284 (United States)

2014-01-07

120

Seebeck Enhancement Through Miniband Conduction in III-V Semiconductor Superlattices at Low Temperatures  

NASA Astrophysics Data System (ADS)

We present theoretically that the cross-plane Seebeck coefficient of InGaAs/InGaAlAs III-V semiconductor superlattices can be significantly enhanced through miniband transport at low temperatures. The miniband dispersion curves are calculated by self-consistently solving the Schrödinger equation with the periodic potential, and the Poisson equation taking into account the charge transfer between the two layers. Boltzmann transport in the relaxation-time approximation is used to calculate the thermoelectric transport properties in the cross-plane direction based on the modified density of states and group velocity. It is found that the cross-plane Seebeck coefficient can be enhanced more than 60% over the bulk values at an equivalent doping level at 80 K when the Fermi level is aligned at an edge of the minibands. Other thermoelectric transport properties are also calculated and discussed to further enhance the thermoelectric power factor.

Bahk, Je-Hyeong; Sadeghian, Ramin Banan; Bian, Zhixi; Shakouri, Ali

2012-06-01

121

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

122

Dilute Group III-V nitride intermediate band solar cells with contact blocking layers  

DOEpatents

An intermediate band solar cell (IBSC) is provided including a p-n junction based on dilute III-V nitride materials and a pair of contact blocking layers positioned on opposite surfaces of the p-n junction for electrically isolating the intermediate band of the p-n junction by blocking the charge transport in the intermediate band without affecting the electron and hole collection efficiency of the p-n junction, thereby increasing open circuit voltage (V.sub.OC) of the IBSC and increasing the photocurrent by utilizing the intermediate band to absorb photons with energy below the band gap of the absorber layers of the IBSC. Hence, the overall power conversion efficiency of a IBSC will be much higher than an conventional single junction solar cell. The p-n junction absorber layers of the IBSC may further have compositionally graded nitrogen concentrations to provide an electric field for more efficient charge collection.

Walukiewicz, Wladyslaw (Kensington, CA); Yu, Kin Man (Lafayette, CA)

2012-07-31

123

Heterogeneously integrated III-V/silicon dual-mode distributed feedback laser array for terahertz generation.  

PubMed

We demonstrate an integrated distributed feedback (DFB) laser array as a dual-wavelength source for narrowband terahertz (THz) generation. The laser array is composed of four heterogeneously integrated III-V-on-silicon DFB lasers with different lengths enabling dual-mode lasing tolerant to process variations, bias fluctuations, and ambient temperature variations. By optical heterodyning the two modes emitted by the dual-wavelength DFB laser in the laser array using a THz photomixer composed of an uni-traveling carrier photodiode (UTC-PD), a narrow and stable carrier signal with a frequency of 0.357 THz is generated. The central operating frequency and the emitted terahertz wave linewidth are analyzed, along with their dependency on the bias current applied to the laser diode and ambient temperature. PMID:25490479

Shao, Haifeng; Keyvaninia, Shahram; Vanwolleghem, Mathias; Ducournau, Guillaume; Jiang, Xiaoqing; Morthier, Geert; Lampin, Jean-Francois; Roelkens, Gunther

2014-11-15

124

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

125

Growth of III-V nitride materials by MOCVD for device applications  

NASA Astrophysics Data System (ADS)

This dissertation describes an investigation of the growth of gallium nitride (GaN) and aluminum gallium nitride (AlxGa1-x N) semiconductor materials by metalorganic chemical vapor deposition (MOCVD) for heterojunction field-effect transistor (HFET) and photodetector device applications. In Chapter I, the III-V nitride material system is discussed, and the current status of growth and device research in this material system is reviewed. Chapter 2 presents a detailed discussion of two important tensor properties of the wurtzite III-V nitrides: elasticity and piezoelectricity. In this discussion, a series of equations are developed that are used throughout this work to calculate properties such as strain, composition, and piezoelectric charge. In Chapter 3, the characterization techniques used to gather data for this dissertation are described. Particular attention is given to x-ray diffraction because of the usefulness and versatility of this technique. Chapter 4 is a description of the MOCVD reactor used to grow all of the films in this work. Chapter 5 presents a complete discussion of the growth and doping of GaN epitaxial layers. This chapter is divided into five sections: buffer layer optimization, GaN:ud growth, GaN:Si growth, Si-implantation of GaN, and GaN:Mg growth. In Chapter 6, the focus shifts to AlGaN epitaxial growth. The first part of the chapter is devoted to the growth and doping of AlGaN layers, while the second part deals with the characteristics of AlGaN/GaN heterostructures. Chapter 7 displays some of the device data from HFETs and photodetectors fabricated from the material described in Chapter 5 and Chapter 6. Finally, this dissertation concludes with Chapter 8, a summary of results and a discussion of potential research for the future.

Eiting, Christopher James

126

Advances in Single and Multijunction III-V Photovoltaics on Silicon for Space Power  

NASA Technical Reports Server (NTRS)

A collaborative research effort at MIT, Ohio State University and NASA has resulted in the demonstration of record quality gallium arsenide (GaAs) based single junction photovoltaic devices on silicon (Si) substrates. The ability to integrate highly efficient, radiation hard III-V based devices on silicon offers the potential for dramatic reductions in cell mass (approx.2x) and increases in cell area. Both of these improvements offer the potential for dramatic reductions in the cost of on-orbit electrical power. Recently, lattice matched InGaP/GaAs and metamorphic InGaP/InGaAs dual junction solar cells were demonstrated by MBE and OMVPE, respectively. Single junction GaAs on Si devices have been integrated into a space flight experiment (MISSES), scheduled to be launched to the International Space Station in March of 2005. I-V performance data from the GaAs/Si will be collected on-orbit and telemetered to ground stations daily. Microcracks in the GaAs epitaxial material, generated because of differences in the thermal expansion coefficient between GaAs and Si, are of concern in the widely varying thermal environment encountered in low Earth orbit. Ground based thermal life cycling (-80 C to + 80 C) equivalent to 1 year in LEO has been conducted on GaAs/Si devices with no discernable degradation in device performance, suggesting that microcracks may not limit the ability to field GaAs/Si in harsh thermal environments. Recent advances in the development and testing of III-V photovoltaic devices on Si will be presented.

Wilt, David M.; Fitzgerald, Eugene A.; Ringel, Steven A.

2005-01-01

127

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

128

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

129

MODIFYING PC1D TO MODEL SPONTANEOUS AND PIEZOELECTRIC POLARIZATION IN III-V NITRIDE SOLAR CELLS  

E-print Network

efficiency caused by polarization-induced electric fields at the GaN/InGaN heterojunction. Scope for future and thus, have significant consequence on solar cell design. Polarization in the III-nitrides induce sheetMODIFYING PC1D TO MODEL SPONTANEOUS AND PIEZOELECTRIC POLARIZATION IN III-V NITRIDE SOLAR CELLS M

Honsberg, Christiana

130

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

E-print Network

A direct thin-film path towards low-cost large-area III-V photovoltaics Rehan Kapadia1,2 *, Zhibin-V photovoltaics (PVs) have demonstrated the highest power conversion efficiencies for both single- and multi times, and large equipment investments restrict applications to concentrated and space photovoltaics

California at Irvine, University of

131

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

...2011-07-01 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...

2011-07-01

132

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

...2010-07-01 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...

2010-07-01

133

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

134

Simulation of III-V strained quantum well lasers with coupled concentric racetrack resonators  

NASA Astrophysics Data System (ADS)

The simulation of the lasing behavior of semiconductor quantum well structures with accurate description of transport phenomena and optical propagation poses great challenges when complex epitaxial layers are coupled with optical cavities in the transverse direction that are more complex than the well know Fabry-Pérot and distributed feedbackreflector based resonators. In this work, we present an approximate approach for the simulation of an electricallypumped III-V strained quantum well laser with coupled concentric racetrack resonators. The electrical, thermal and optical behavior of an epitaxial stack with at least one quantum well is obtained from a physics based simulator for a reduced dimensionality problem, and this solution is coupled with the cold cavity analysis of the resonator using either finite difference time domain simulation or coupled-mode analysis. The effects of gain and charge transport on the active resonator are then taken into account as a perturbation and the approximate solution derived. Comparison with actual devices based on InGaAlAs/InGaAs/InP and InGaSb/AlGaAsSb/GaSb shows reasonable agreement. The concentric racetrack resonator exhibits complex dispersive behavior, with possible applications in sensing, nonlinear phenomena and optical signal processing.

Viegas, Jaime; Xing, Peng; Serunjogi, Solomon M.

2014-03-01

135

Calculations of the specific resistance of contacts to III-V nitride compounds  

SciTech Connect

The authors present calculations of the specific contact resistance for metals to GaN. The calculations include a correct determination of the Fermi level taking into account the effect of the degenerate doping levels, required in creating tunneling ohmic contacts. Using a recently reported improved WKB approximation suitable in representing the depletion width at the metal-semiconductor interface, and a two band k{center_dot}p model for the effective masses, specific contact resistance was determined as a function of doping concentration. The specific contact resistance was calculated using the best data available for barrier heights, effective masses and dielectric coefficients for GaN. Because the barrier height at the metal-semiconductor interface has a very large effect on the contact resistance and the available data is sketchy or uncertain, the effect of varying the barrier height on the calculated specific contact resistance was investigated. Further, since the III-V nitrides are being considered for high temperature device applications, the specific contact resistance was also determined as a function of temperature.

Barnes, P.A.; Zhang, X.J. [Auburn Univ., AL (United States). Dept. of Physics; Lovejoy, M.L.; Drummond, T.J.; Hjalmarson, H.P.; Crawford, M.; Shul, R.J.; Zolper, J.C. [Sandia National Labs., Albuquerque, NM (United States)

1996-11-01

136

Calculations of the specific resistance of contacts to III-V nitride compounds  

SciTech Connect

We present calculations of the specific contact resistance for metals to GaN. The calculations include a correct determination of the Fermi level taking into account the effect of the degenerate doping levels, required in creating tunneling ohmic contacts. Using a recently reported improved WKB approximation suitable in representing the depletion width at the metal-semiconductor interface, and a two band k-p model for the effective masses, specific contact resistance was determined as a function of doping concentration. The specific contact resistance was calculated using the best data available for barrier heights, effective masses and dielectric coefficients for GaN. Because the barrier height at the metal-semiconductor interface has a very large effect on the contact resistance and the available data is sketchy or uncertain, the effect of varying the barrier height on the calculated specific contact resistance was investigated. Further, since the III-V nitrides are being considered for high temperature device applications, the specific contact resistance was also determined as a function of temperature.

Barnes, P.A.; Zhang, X.J. [Auburn Univ., AL (United States). Dept. of Physics; Lovejoy, M.L.; Drummond, T.J.; Hjalmarson, H.P.; Crawford, M.; Shul, R.J.; Zolper, J.C. [Sandia National Labs., Albuquerque, NM (United States)

1995-12-31

137

Compositional and Structural Characterization by TEM of Lattice-Mismatched III-V Epilayers  

SciTech Connect

We discuss compositional and structural transmission electron microscopy (TEM) characterization of lattice-mismatched (LMM) III-V epilayers grown on GaAs by metalorganic chemical vapor deposition (MOCVD), with possible applications in high-efficiency multijunction solar cells. In addition to the use of TEM imaging to survey layer thicknesses and defect morphology, our analysis emphasizes the particular methods of energy-dispersive X-ray spectrometry (EDX) and convergent-beam electron diffraction (CBED). Outlined here is a standards-based method for extracting compositions by EDX, which uses principal-component analysis (PCA) [1], combined with the zeta-factor approach of Watanabe and Williams [2]. A procedure is described that uses the coordinates of high-order Laue zone (HOLZ) lines, which are found in the bright-field disks of CBED patterns, to extract composition and strain parameters from embedded epilayers. The majority of the crystal growth for this work was performed at NREL, which has accommodated the development at SDSM&T of the characterization techniques described. However, epilayer deposition capability at SDSM&T has recently been achieved, using a home-built system, which is presently being used to examine new lattice-mismatched structures relevant to photovoltaic technology.

Ahrenkiel, S. P.; Rathi, M.; Nesheim, R.; Zheng, N.; Vunnam, S.; Carapella, J. J.; Wanlass, M. W.

2011-01-01

138

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

139

Studies of the III-V compounds in the megabar regime  

NASA Astrophysics Data System (ADS)

In this project the authors develop techniques for making high pressure measurements (x-ray diffraction and optical measurements) on samples in the multimegabar regime and they make systematic studies of the crystal structure of III-V compounds and other materials as a function of pressure with the broad objective of providing experimental data over a broad range of coordination number and interatomic spacing which can play a leading role in the testing and development of theoretical models of binding. They also create new materials. It was shown that all the compounds AlN, GaN, and InN transform to the C1-type structure with AlN remaining as 100% rocksalt structure on release of pressure. Various parameters in the equation of state (EOS) were measured. The EOS of BP was measured to 110 GPa but no phase transitions were seen. AlAs was shown to transform from the initial zincblende phase to the nickel arsenide phase, the first case of this in the IV-V compounds. The first experiments on CdTe were carried to 51 GPa and are now being analyzed.

Ruoff, Arhtur L.

140

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

141

A novel surface preparation methodology for epi-ready antimonide based III-V substrates  

NASA Astrophysics Data System (ADS)

Surfaces of GaSb substrates currently available from various commercial vendors are nowhere close to device grade GaAs, Si or InP wafer surfaces. Hence epitaxial growth and device fabrication on as-received commercial substrates poses significant difficulties amongst antimonide based researchers. Antimonide based materials are known to have poor surface oxide quality and not so well understood chemical reactions with various chemicals used to remove the oxides prior to growth. There are no existing reports on the detailed recipe for the preparation of "atomically flat and clean" surfaces that works on wafers obtained from various commercial vendors. This paper presents a detailed recipe for obtaining atomically flat and clean GaSb surfaces, irrespective of the initial polishing source. The same recipe (with slight modification) has been found to be successful with other III-V and II-VI compounds. The novel surface preparation process developed in our laboratory includes, chemical-mechanical polishing using an agglomerate-free sub-micron alumina slurry on a soft pad such as velvet, surface cleaning using dilute ammonium or potassium hydroxide-H2O solution and surfactant or glycerol, surface degreasing using organic solvents, oxide desorption using HCl-H2O and HF-H2O mixtures, mild chemical etching using ammonium sulfide and a final rinse in high purity deionized (DI) water and methanol. Using this recipe, we have been able to achieve surfaces with atomic flatness (RMS surface roughness close to 0.5 nm over a 10 x 10 mm2) and extremely clean surfaces, irrespective of the initial contamination or the sources of the wafers. Results of wafer surfaces before and after polishing using our recipe will be presented.

Dutta, P. S.; Rajagopalan, G.; Kim, H. J.; Kumar, A.

2005-05-01

142

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

143

Impact of vacuum anneal at low temperature on Al2O3/In-based III-V interfaces  

NASA Astrophysics Data System (ADS)

We report on the effect of vacuum anneal on interfacial oxides formed between Al2O3 and III-V semiconductors. On InGaAs, no interfacial oxide is detected after annealing at 600 °C under UHV whereas annealing under secondary vacuum favours the regrowth of thin InGaOx interfacial oxide. Lowering the temperature at 400 °C highlights the effect of III-V substrates since In-OH bonds are only formed on InAs by OH release from TMA/H2O deposited alumina. On InGaAs, regrowth of InGaOx is observed, as a result of preferential oxidation of Ga. On InP, a transition from InPOx to POx is highlighted.

Martinez, E.; Grampeix, H.; Desplats, O.; Herrera-Gomez, A.; Ceballos-Sanchez, O.; Guerrero, J.; Yckache, K.; Martin, F.

2012-06-01

144

Optimization of the silicon subcell for III-V on silicon multijunction solar cells: Key differences with conventional silicon technology  

NASA Astrophysics Data System (ADS)

Dual-junction solar cells formed by a GaAsP or GaInP top cell and a silicon (Si) bottom cell seem to be attractive candidates to materialize the long sought-for integration of III-V materials on Si for photovoltaic (PV) applications. Such integration would offer a cost breakthrough for PV technology, unifying the low cost of Si and the efficiency potential of III-V multijunction solar cells. The optimization of the Si solar cells properties in flat-plate PV technology is well-known; nevertheless, it has been proven that the behavior of Si substrates is different when processed in an MOVPE reactor In this study, we analyze several factors influencing the bottom subcell performance, namely, 1) the emitter formation as a result of phosphorus diffusion; 2) the passivation quality provided by the GaP nucleation layer; and 3) the process impact on the bottom subcell PV properties.

García-Tabarés, Elisa; Martín, Diego; García, Iván; Lelièvre, Jean François; Rey-Stolle, Ignacio

2012-10-01

145

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

146

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

147

Static and dynamical properties of II-VI and III-V group binary solids  

NASA Astrophysics Data System (ADS)

In this paper, we extend to II-VI and III-V group binary solids of zinc blende (ZB) structure with conduction d-electrons the calculation of static and dynamical properties such as bulk modulus (B) and cohesive energy or total energy (Ecoh) using the plasma oscillation theory of solids formalism already employed for ternary chalcopyrite semiconductors. The present method is not limited to tetrahedrally coordinated semiconductors and ternary chalcopyrites, but can be used for all semiconducting compounds. We have applied an extended formula on ZB structured binary semiconductors and found better agreement with the experimental data as compared to the values evaluated by previous researchers. The bulk modulus and cohesive energy of ZB-type structure compounds exhibit a linear relationship when plotted on a log-log scale against the plasmon energy planck?p (in eV), but fall on a straight line. The results for bulk modulus differ from experimental values by the following amounts: ZnS 0.36%, ZnSe 10%, ZnTe 0.62%, CdS 1.8%, CdSe 7.4% and CdTe 1.6%, AlP 2.6%, AlAs 5.3%, AlSb 4.0%, GaP 0%, AlAs 0%, AlS 4.4%, InP 0%, InAs 0% and InSb 2.1%; and the results for cohesive energy differ from experimental values by the following amounts: ZnS 0.16%, ZnSe 0.73%, ZnTe 0.6%, CdS 7.6%, CdSe 3.5%, CdTe 2.5%, AlP 2.0%, AlAs 3.0%, AlSb 11.1%, GaP 14.6%, AlAs 17.0%, AlSb 8.7%, InP 4.3%, InAs 5.5% and InSb 0.6%.

Yadav, D. S.; Singh, D. V.

2012-01-01

148

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.

149

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

150

A survey of ohmic contacts to III-V compound semiconductors  

Microsoft Academic Search

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. Ni\\/AuGe 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

A. G. Baca; F. Ren; J. C. Zopler; R. D. Briggs; S. J. Pearton

1997-01-01

151

Understanding the Potential and Limitations of Dilute Nitride Alloys for Solar Cells  

SciTech Connect

Dilute nitride alloys provide a powerful tool for engineering the band gap and lattice constant of III-V alloys. However, nitrogen degrades the performance of GaAs solar cells. This project seeks to understand and demonstrate the limits of performance of GaInNAs alloys by (a) correlating deep-level transient spectroscopy (DLTS) data with device performance and (b) using molecular beam epitaxy (MBE) to reduce background impurity concentrations.

Kurtz, S.; Ptak, A.; Johnston, S.; Kramer, C.; Young, M.; Friedman, D.; Geisz, J.; McMahon, W.; Kibbler, A.; Olson, J.; Crandall, R.; Branz, H.

2005-11-01

152

Spectroscopic Characterization of Dry Etch-Induced Modification in Iii-V Semiconductors and Semiconductor Heterostructures  

NASA Astrophysics Data System (ADS)

The effects of dry etching on the structural and electrical properties of III-V semiconductors and semiconductor heterostructures were studied using vibrational and electronic Raman spectroscopy and low and room temperature photoluminescence spectroscopy. The frequency, intensity, and lineshape of the dipole-allowed and dipole-forbidden longitudinal optic (LO) phonon as well as the dipole-forbidden transverse optic phonon were used to evaluate structural modification in doped and undoped material. The intensities and frequencies of the coupled LO phonon-plasmon modes relative to those of the unscreened LO phonon were used to probe changes in the surface space charge region and free carrier concentration. Photoluminescence peak energies, intensity, and lineshape were used to evaluate crystal quality and defect identity. Structural modification was investigated in GaAs etched in SiCl_4, SiCl_4 /SiF_4, and CH_4 /H_2 plasmas and sputtered in an Ar plasma. SiCl_4 and SiCl _4/SiF_4 etches both produced significant structural modification. CH _4/H_2 plasmas produced less structural modification, however, a highly disordered surface layer was still created. Electrical modification by the methane-based plasmas was found to depend weakly on the self-bias voltage and was confined to within ca. 125 A of the surface. The effects of reactive ion etching (RIE) in methane -based plasmas as well as sputtering in Ar and He plasmas on InP were investigated. In general, methane-based plasmas showed far less structural damage than sputtering. Samples sputtered in Ar plasmas exhibited the most structural modification, however, at larger bias voltages some structural modification was observed for methane-based etches (except CH _4/H_2 plasmas). Of the methane-based etches CH_4/H _2 and CH_4/H _2/Ar plasmas exhibited the least structural modification. Electrical modification was also seen to be more extensive with sputter etches than methane -based etches. Samples sputtered in He plasmas showed more electrical perturbations than samples sputtered in Ar plasmas. Methane -based etches did affect electrical properties of InP. No clear trends were observed, although, in general, CH _4/H_2 etches resulted in the largest depletion widths. The effects of HBr RIE and Ar sputtering on InGaAs and InAlAs were investigated. Ar sputtering of InGaAs resulted in significant structural modification. HBr-etching lead to significantly less structural modification, although some disorder was created by these etches. Ar sputtering of InAlAs also resulted in structural modification, although to a lesser degree than observed for InGaAs. Ar sputtering results in the formation of a high-donor density surface region, which leads to the creation of an electron accumulation layer in the near-surface region. A decrease in carrier concentration was observed to ca. 230 A in HBr-etched n^+-InAlAs. The presence and shifts of the coupled phonon -two-dimensional electron gas (2DEG) plasmon modes in InGaAs/InAlAs heterostructures were used to investigate the effects of HBr RIE on the 2DEG properties. Etch-induced 2DEG modification was greatly reduced when the InAlAs barrier thickness was increased from 75 A to 350 A. For the structures with the smallest barrier thicknesses the decrease in 2DEG concentration was more strongly dependent on increased etch times than increased self-bias voltage.

Maslar, James Edgar

153

Low-frequency noise sources in III-V semiconductor heterostructures  

NASA Astrophysics Data System (ADS)

III-V semiconductor heterostructures have widespread interest in both electrical and optical applications. Their figure-of-merit low-frequency noise level directly sets the limits of the performance of devices and indirectly serves as the indicator of material properties and device reliability. In particular, generation-recombination noise signals in the low-frequency noise range directly indicate the dominant traps that impact device operation. In this dissertation, low-frequency noise source investigations of GaAs/buffer and AlxGa1-xN/GaN heterostructures in the applications of microwave power amplifiers will be presented. For GaAs/buffer heterostructures, low-frequency noise characteristics of GaAs-On-Insulator metal-semiconductor field effect transistors, for which the insulating buffer layer was produced by lateral wet-oxidation of AlAs, are studied. Devices with different gate widths were fabricated resulting in different over-oxidation times for the AlAs layer. Three characteristic generation-recombination noise signatures are observed depending on the measurement temperature and the gate bias. A generation-recombination noise signature with energy level at Ec-0.69 eV is found to increase with the amount of over-oxidation time. This near mid-gap trap shows an increase in concentration towards the oxide interface, and it is tentatively assigned to an arsenic-antisite related defect known from previous studies as EB4. A possible mechanism for the formation and the microscopic origin of this defect are discussed. 1/f interface noise model is applied to analyze the GaAs/buffer interfacial quality. The effective interface state density was found to be as high as 1015 cm-2 and increase with additional over-oxidation. A correlation between the amount of over-oxidation and the number of calculated interface states is observed. For AlxGa1-xN/GaN heterostructures, low-frequency noise characteristics of AlxGa1-xN/GaN HEMTs with Al composition of 28--35% in the barrier layer are studied. A generation-recombination noise signature is attributed to a trap in AlxGa1-x N barrier layer which increases in concentration towards the Al xGa1-xN/GaN interface. The origin and the location of low-frequency noise were differentiated by the drain current dependent measurement. When the long-channel device is operated with an open channel (e.g. VG = 0), the main noise source resides in the gated channel instead of in the ungated region. Hooge's parameter of the gated channel (alpha ˜ 10-4) is found to be independent of the Al composition but dependent on the AlxGa1-x N barrier thickness. This is proposed to correspond to the onset of barrier relaxation. Even though the AlxGa1-xN/GaN HEMT exhibits a low level of gate leakage current (<1% of drain current), the low-frequency noise is still heavily influenced by the gate leakage current at certain bias conditions. The effect of gate leakage current on the low-frequency noise properties is discussed. The surface leakage path appeared to dominate the low-frequency noise properties for devices operated at a high IG/ID ratio.

Tzeng, Susie

154

Continuous-wave quasi-phase-matched waveguide correlated photon pair source on a III–V chip  

SciTech Connect

We report on the demonstration of correlated photon pair generation in a quasi-phase-matched superlattice GaAs/AlGaAs waveguide using a continuous-wave pump. Our photon pair source has a low noise level and achieves a high coincidence-to-accidental ratio greater than 100, which is the highest value reported in III–V chips so far. This correlated photon pair source has the potential to be monolithically integrated with on-chip pump laser sources fabricated on the same superlattice wafer structure, enabling direct correlated/entangled photon pair production from a compact electrically powered chip.

Sarrafi, Peyman, E-mail: peyman.sarrafi@mail.utoronto.ca; Zhu, Eric Y.; Dolgaleva, Ksenia; Aitchison, J. Stewart; Qian, Li [Department of Electrical and Computer Engineering, University of Toronto, 10 King's College Road, Toronto, Ontario M5S 3G4 (Canada)] [Department of Electrical and Computer Engineering, University of Toronto, 10 King's College Road, Toronto, Ontario M5S 3G4 (Canada); Holmes, Barry M.; Hutchings, David C. [School of Engineering, University of Glasgow, Glasgow G12 8QQ, Scotland (United Kingdom)] [School of Engineering, University of Glasgow, Glasgow G12 8QQ, Scotland (United Kingdom)

2013-12-16

155

Studies on Miltenberger class III, V, Mv and Mk red cells. I. Sodium-dodecylsulfate polyacrylamide gel electrophoretic investigations.  

PubMed

The glycoproteins in erythrocyte membrane from individuals exhibiting the rare alleles at the MNSs blood group locus Miltenberger (Mi-) III, V, Mv and Mk were studied by sodium-dodecylsulfate polyacrylamide gel electrophoretic techniques. The results suggest that the genes Mi-III and -V give rise to the formation of Ss sialoglycoproteins whose electrophoretic mobilities are altered. The Mi-V alteration is additionally associated with a decreased MN glycoprotein content. The allele Mv leads to a decreased Ss glycoprotein content. Data on ordinary Mk and Mk/Mi-III red cells suggest that the gene complex Mk does not give rise to the synthesis of Ss glycoprotein. PMID:687840

Dahr, W; Longster, G; Uhlenbruck, G; Schumacher, K

1978-09-15

156

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

157

The coupling of thermochemistry and phase diagrams for Group III-V semiconductor systems  

NASA Astrophysics Data System (ADS)

Assessment studies revealed inconsistencies in reported Tl activities. Ga and In activities were measured as a function of temperature and composition in liquid Ga-Tl and In-Tl alloys. Large positive deviations from ideal solution behavior were found in Ga-Tl while the In-Tl system showed nearly ideal behavior. The extent of solid solution in the compound AlSb was determined by electrochemical titration with a measured range 8 x 10 to the -4 to 2 x 10 to the -3 mole fraction at 846 C. The enthalpy of mixing GaP and InP to form the pseudobinary solid solution Ga(sub x)In(sub 1-x)P was determined by solution calorimetry. A positive enthalpy of mixing was reported. Knudsen effusion studies were performed on Ga(sub x)In(sub 1-x)P alloys. Results indicate the existence of a solid miscibility gap in this system. CALPHAD procedures were applied to the Al-Ga-In-Sb pseudoternary and Ga-In-Sn ternary systems.

Anderson, T. J.

1987-05-01

158

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

159

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

NASA Astrophysics Data System (ADS)

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.

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

2013-07-01

160

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

SciTech Connect

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{sup ?}) 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, Hg{sub 1?x}Cd{sub x}Te, and In{sub 1?x}Ga{sub x}As{sub y}P{sub 1?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, E-mail: a-dey2002@yahoo.com [Electronics and Communication Engineering Department, Kalyani Government Engineering College, Kalyani 741235 (India); Maiti, Biswajit [Physics Department, Kalyani Government Engineering College, Kalyani 741235 (India); Chanda, Debasree [Department of Engineering and Technological Studies, Kalyani University, Kalyani 741235 (India)

2014-04-14

161

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

162

Generation of substrate-free III-V nanodisks from user-defined multilayer nanopillar arrays for integration on Si  

NASA Astrophysics Data System (ADS)

High material quality InP-based multilayer nanopillar (NP) arrays are fabricated using a combination of self-assembly of silica particles for mask generation and dry etching. In particular, the NP arrays are made from user-defined epitaxial multilayer stacks with specific materials and layer thicknesses. An additional degree of flexibility in the structures is obtained by changing the lateral diameters of the NP multilayer stacks. Pre-defined NP arrays made from InGaAsP/InP and InGaAs/InP NPs are then used to generate substrate-free nanodisks of a chosen material from the stack by selective etching. A soft-stamping method is demonstrated to transfer the generated nanodisks with arbitrary densities onto Si. The transferred nanodisks retain their smooth surface morphologies and their designed geometrical dimensions. Both InP and InGaAsP nanodisks display excellent photoluminescence properties, with line-widths comparable to unprocessed reference epitaxial layers of similar composition. The multilayer NP arrays are potentially attractive for broad-band absorption in third-generation solar cells. The high optical quality, substrate-free InP and InGaAsP nanodisks on Si offer a new path to explore alternative ways to integrate III-V on Si by bonding nanodisks to Si. The method also has the advantage of re-usable III-V substrates for subsequent layer growth.

Naureen, S.; Shahid, N.; Dev, A.; Anand, S.

2013-06-01

163

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

PubMed

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 10(6). PMID:24516134

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

2014-02-25

164

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

165

All-silicon and epitaxially grown III-V-on-silicon photodetectors for on-chip optical interconnection applications  

NASA Astrophysics Data System (ADS)

In this paper we review our recent progress in two complementary approaches to photodetectors on silicon photonic chips for on-chip optical interconnection applications, namely epitaxially grown III-V-on-silicon and all-silicon microcavity-enhanced photodetectors, both for the 1550nm wavelengths. On the epitaxially grown III-V-on-silicon photodetectors front, we have demonstrated both normal-incidence and waveguide-butt-coupled p-i-n photodetectors. We simulate the silicon waveguide butt-coupling to the InGaAs absorption region and estimate the absorption efficiency using a three-dimensional finite-difference time-domain method. We optimize the InGaAs absorption region in order to attain a bandwidth of 46 GHz. We also report our latest experimental demonstration of all-silicon microresonator enhanced linear-absorption photodetectors using defect-state absorption in pn-diode-integrated microresonators. Our initial experiments reveal the measured bandwidths to be exceeding 10 GHz.

Poon, Andrew W.; Feng, Shaoqi; Li, Yu; Geng, Yu; Lau, Kei May

2013-03-01

166

III-V-N materials for super high-efficiency multijunction solar cells  

SciTech Connect

We have been studying concentrator multi-junction solar cells under Japanese Innovative Photovoltaic R and D program since FY2008. InGaAsN is one of appropriate materials for 4-or 5-junction solar cell configuration because this material can be lattice-matched to GaAs and Ge substrates. However, present InGaAsN single-junction solar cells have been inefficient because of low minority-carrier lifetime due to N-related recombination centers and low carrier mobility due to alloy scattering and non-homogeneity of N. This paper presents our major results in the understanding of majority and minority carrier traps in GaAsN grown by chemical beam epitaxy and their relationships with the poor electrical properties of the materials.

Yamaguchi, Masafumi; Bouzazi, Boussairi; Suzuki, Hidetoshi; Ikeda, Kazuma; Kojima, Nobuaki; Ohshita, Yoshio [Toyota Technological Institute, Nagoya 468-8511 (Japan)

2012-10-06

167

Heterogeneously integrated III-V/Si single mode lasers based on a MMI-ring configuration and triplet-ring reflectors  

NASA Astrophysics Data System (ADS)

In this paper we show that using a DVS-BCB adhesive bonding process compact heterogeneously integrated III-V/silicon single mode lasers can be realized. Two new designs were implemented: in a first design a multimode interferometer coupler (MMI) - ring resonator combination is used to provide a comb-like reflection spectrum, while in a second design a triplet-ring reflector design is used to obtain the same. A broadband silicon Bragg grating reflector is implemented on the other side of the cavity. The III-V optical amplifier is heterogeneously integrated on the 400nm thick silicon waveguide layer, which is compatible with high-performance modulator designs and allows for efficient coupling to a standard 220nm high index contrast silicon waveguide layer. In order to make the optical coupling efficient, both the III-V waveguide and the silicon waveguide are tapered, with a tip width of the III-V waveguide of around 500nm. The III-V thin film optical amplifier is implemented as a 3?m wide mesa etched through to the n-type InP contact layer. In this particular device implementation the amplifier section was 500?m long. mW-level waveguide coupled output power at 20°C and a side mode suppression ratio of more than 40dB is obtained.

Keyvaninia, S.; Verstuyft, S.; Lelarge, F.; Duan, G.-H.; Messaoudene, S.; Fédéli, J. M.; Geluk, E. J.; De Vries, T.; Smalbrugge, B.; Bolk, J.; Smit, M.; Van Thourhout, D.; Roelkens, G.

2013-05-01

168

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

NASA Technical Reports Server (NTRS)

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

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

1979-01-01

169

Engineering the Cell-Semiconductor Interface: A Materials Modification Approach using II-VI and III-V Semiconductor Materials.  

PubMed

Developing functional biomedical devices based on semiconductor materials requires an understanding of interactions taking place at the material-biosystem interface. Cell behavior is dependent on the local physicochemical environment. While standard routes of material preparation involve chemical functionalization of the active surface, this review emphasizes both biocompatibility of unmodified surfaces as well as use of topographic features in manipulating cell-material interactions. Initially, the review discusses experiments involving unmodified II-VI and III-V semiconductors - a starting point for assessing cytotoxicity and biocompatibility - followed by specific surface modification, including the generation of submicron roughness or the potential effect of quantum dot structures. Finally, the discussion turns to more recent work in coupling topography and specific chemistry, enhancing the tunability of the cell-semiconductor interface. With this broadened materials approach, researchers' ability to tune the interactions between semiconductors and biological environments continues to improve, reaching new heights in device function. PMID:25387841

Bain, Lauren E; Ivanisevic, Albena

2015-02-01

170

Effects of proton irradiation on luminescence and carrier dynamics of self-assembled III-V quatum dots  

NASA Technical Reports Server (NTRS)

The effects of proton irradiation (1.5 MeV) on photoluminescence intensities and carrier dynamics were compared between III-V quantum dots and similar quantum well structures. A significant enhancement in radiation tolerance is seen with three-dimensional quantum confinement. Measurements were carried out in different quantum dot (QD) structures, varying in material (InGaAs/GaAs and InAlAs/AlGaAs), QD surface density (4x10^8 to 3x10'^10 cm^-2), and substrate orientation [(100) and (311) B]. Similar trends were observed for all QD samples. A slight increase in PL emission after low to intermediate proton doses, are also observed in InGaAs/GaAs (100) QD structures. The latter is explained in terms of more efficient carrier transfer from the wetting layer via radiation-induced defects.

Leon, R.; Marcinkevicius, S.; Siegert, J.; Magness, B.; Taylor, W.; Lobo, C.

2002-01-01

171

Estimation of the isotope effect on the lattice thermal conductivity of group IV and group III-V semiconductors  

NASA Astrophysics Data System (ADS)

The isotope effect on the lattice thermal conductivity for group IV and group III-V semiconductors is calculated using the Debye-Callaway model modified to include both transverse and longitudinal phonon modes explicitly. The frequency and temperature dependences of the normal and umklapp phonon-scattering rates are kept the same for all compounds. The model requires as adjustable parameters only the longitudinal and transverse phonon Grüneisen constants and the effective sample diameter. The model can quantitatively account for the observed isotope effect in diamond and germanium but not in silicon. The magnitude of the isotope effect is predicted for silicon carbide, boron nitride, and gallium nitride. In the case of boron nitride the predicted increase in the room-temperature thermal conductivity with isotopic enrichment is in excess of 100%. Finally, a more general method of estimating normal phonon-scattering rate coefficients for other types of solids is presented.

Morelli, D. T.; Heremans, J. P.; Slack, G. A.

2002-11-01

172

Au-Seeded Growth of Vertical and in-Plane III–V Nanowires on Graphite Substrates  

PubMed Central

Graphene is promising as a transparent, flexible, and possibly cost-effective substrate for nanowire-based devices. We have investigated Au-seeded III–V nanowire growth with graphite as a model substrate. The highest yield of undoped vertical nanowires was found for InAs, but we also observed vertical nanowires for the InP, GaP, and GaAs materials. The yield of vertical nanowires for GaP and GaAs was strongly improved by supplying the p-dopant DEZn before nanowire growth but not by supplying H2S or HCl. In-plane GaAs and GaP nanowire growth exhibited an unexpected behavior, where the seed particles seemingly reflected on the side facets of other nanowires. These results pave the way for vertical and in-plane hybrid graphene- nanowire devices. PMID:24592968

2014-01-01

173

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

174

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

PubMed Central

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 Fe0 nanoparticles showed remarkable potential for As (III, V) removal from aqueous solution e.g. contaminated water. PMID:24860660

2014-01-01

175

Basic studies of III-V high-efficiency cell components: Annual subcontract report, 15 August 1985-14 August 1986  

SciTech Connect

This report documents research on the fabrication and photovoltaic characterization of the basic building blocks of III-V cells: the pn junction, the pn heterojunction, the isotype (p-p and n-n) heterojunction, and graded-gap semiconductors. The goal of the project is to maximize cell performance by characterizing the electrical properties of high-efficiency cell components. Other goals are to demonstrate new cell structures fabricated by molecular beam epitaxy (MBE), develop measurement techniques, and characterize methodologies. This work should help identify paths toward higher efficiency III-V cells.

Lundstrom, M S; Melloch, M R; Kyono, C S; McMahon, C P; Noren, R E; Rancour, D P

1987-03-01

176

Iii-V Compound Multiple Quantum Well Based Modulator and Switching Devices.  

NASA Astrophysics Data System (ADS)

A general formalism to study the absorption and photocurrent in multiple quantum well is provided with detailed consideration of quantum confined Stark shift, exciton binding energy, line broadening, tunneling, polarization, and strain effects. Results on variation of exciton size, binding energies and transition energies as a function electric field and well size have been presented. Inhomogeneous line broadening of exciton lines due to interface roughness, alloy disorder and well to well size fluctuation is calculated. The potential of material tailoring by introducing strain for specific optical response is discussed. Theoretical and experimental results on excitonic and band-to-band absorption spectra in strained multi-quantum well structures are shown. I also report on polarization dependent optical absorption for excitonic and interband transitions in lattice matched and strained multiquantum well structures in presence of transverse electric field. Photocurrent in a p-i(MQW)-n diode with monochromatic light is examined with respect to different temperatures and intensities. The negative resistance of I-V characteristic of the p-i-n diode is based on the quantum confined Stark effect of the heavy hole excitonic transition in a multiquantum well. This exciton based photocurrent characteristic allows efficient switching. A general purpose low power optical logic device using the controller-modulator concept bas been proposed and realized. The controller is a heterojunction phototransistor with multiquantum wells in the base-collector depletion region. This allows an amplified photocurrent controlled voltage feedback with low light intensity levels. Detailed analysis of the sensitivity of this device in various modes of operation is studied. Studies are also presented on the cascadability of the device as well as its integrating -thresholding properties. A multiquantum well heterojunction bipolar transistor (MHBT), which has N^+ -p^+-i(MQW)-N structure has been fabricated to test the concept. Gain (>30) is obtained in the MBE grown devices and efficient switching occurs due to the amplification of the exciton based photocurrent. The level shift operation of the base contacted MHBT are demonstrated.

Hong, Songcheol

177

The formation of ohmic and Schottky enhanced contacts to III-V compound semiconductors via the exchange mechanism: A combined thermodynamic and kinetic model  

Microsoft Academic Search

A methodology is presented for altering the electrical properties of contacts to III-V compound semiconductors through the use of controlled interfacial chemical reactions. The process by which this is accomplished has been termed the exchange mechanism. Under this mechanism, a metallization consisting of a transition metal and a group III element (denoted TIII') is reacted with the semiconductor (denoted IIIV)

D. Swenson; C.-H. Jan; Y. A. Chang

1998-01-01

178

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

179

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

180

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, 2014 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...

2014-07-01

181

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

182

Analytical description of the metal-assisted growth of III-V nanowires: Axial and radial growths  

SciTech Connect

The growth of III-V nanowires from metal seed particles is described in an analytical manner within the framework of a material conservation model. Direct impingement of growth species on the particle, coupled to their diffusion from the sidewall and the substrate surface, are considered in the derivation of expressions for the time evolution of both axial and radial growths. Two regimes are distinguished: the structure originally grows in a purely axial manner until its length exceeds the diffusion length of adatoms incoming from the substrate, at which point sidewall nucleation is triggered, resulting in a shell expanding radially in the lower part of the wire. Factors that take into account the nonunity probability of inclusion of group III adatoms in the axially growing crystal are introduced. Moreover, a step-mediated growth is included to describe the axial evolution of the shell. The numerical values of the various parameters were assessed by fitting the model to experimental data on the morphology evolution of molecular-beam-epitaxy-grown GaAs and InAs nanowires.

Plante, Martin C.; LaPierre, Ray R. [Department of Engineering Physics, Centre for Emerging Device Technologies, McMaster University, Hamilton, Ontario L8S 4L7 (Canada)

2009-06-01

183

Orientation dependence of electronic structure and optical gain of (11N)-oriented III-V-N quantum wells  

NASA Astrophysics Data System (ADS)

A ten-band k.p Hamiltonian for III-V-N dilute nitride semiconductor quantum wells (QWs) grown on the (11N)-oriented substrates is presented. The energy dispersion curves, optical transition matrix elements, internal piezoelectric field, and optical gain of InGaAsN/GaAs on the (110), (111), (113), and (11?)-oriented substrates are investigated including band-anti-crossing, strain, and piezoelectric field effects. The band structures and optical gain are sensitive to the substrate orientation. The fundamental transition energy is the largest for the (111)-oriented QW and the smallest for (11?)-oriented QW. The absolute values of internal piezoelectric field in the well and barrier layers reach the maximum for the (111)-QW, and zero for the (110) and (11?)-oriented QWs. There exists an injection current density turning point. When the injection current density is below the turning point, the (111)-oriented QW has the largest peak gain. At the larger injection current density, the (11?)-oriented QW has the largest peak gain.

Fan, W. J.

2013-02-01

184

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

185

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

186

Minority Carrier Diffusivity Measurements in III -v Semiconductors by the Zero-Field Time-Of Technique  

NASA Astrophysics Data System (ADS)

Minority carrier diffusivity, or equivalently mobility, is an important transport parameter that determines the performance of devices such as transistors and solar cells. Heavily doped gallium arsenide (GaAs) is an important material system for these devices, however, minority carrier diffusivity data are lacking because the diffusivity is difficult to measure. A major objective of this study was to critically analyze the zero-field time-of-flight (ZFTOF) technique and to develop application criteria for measuring the minority carrier diffusivity in heavily doped III-V semiconductors. The main objective of this project was to measure the doping dependence of minority diffusivity in heavily doped n- and p-type GaAs and to compare minority electron properties for Be- and C-doped p^+ -GaAs. Both minority hole and electron diffusivities were found to be higher than theoretically predicted, and the minority electron mobility was higher than was deduced from high-field measurements. Furthermore, the electron properties were found to be the same for p^+ -GaAs doped to ~10 ^{19} cm^{ -3} with beryllium and with carbon. The higher than expected diffusivities were shown to have important implications on device performance. The final objective was to extend the ZFTOF technique to temperature-dependent minority diffusivity measurements. To that end, a ZFTOF cryogenic system was designed and built. The system was being tested at the time this is being written. It is anticipated that temperature-dependent measurements with the new cryostat will provide data which will help to identify the important scattering mechanisms that limit the performance of bipolar devices.

Lovejoy, Michael Lowell

1992-01-01

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 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

188

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

189

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

190

Self-aligned, extremely high frequency III-V metal-oxide-semiconductor field-effect transistors on rigid and flexible substrates.  

PubMed

This paper reports the radio frequency (RF) performance of InAs nanomembrane transistors on both mechanically rigid and flexible substrates. We have employed a self-aligned device architecture by using a T-shaped gate structure to fabricate high performance InAs metal-oxide-semiconductor field-effect transistors (MOSFETs) with channel lengths down to 75 nm. RF measurements reveal that the InAs devices made on a silicon substrate exhibit a cutoff frequency (f(t)) of ?165 GHz, which is one of the best results achieved in III-V MOSFETs on silicon. Similarly, the devices fabricated on a bendable polyimide substrate provide a f(t) of ?105 GHz, representing the best performance achieved for transistors fabricated directly on mechanically flexible substrates. The results demonstrate the potential of III-V-on-insulator platform for extremely high-frequency (EHF) electronics on both conventional silicon and flexible substrates. PMID:22746202

Wang, Chuan; Chien, Jun-Chau; Fang, Hui; Takei, Kuniharu; Nah, Junghyo; Plis, E; Krishna, Sanjay; Niknejad, Ali M; Javey, Ali

2012-08-01

191

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

192

Position-controlled III-V compound semiconductor nanowire solar cells by selective-area metal-organic vapor phase epitaxy.  

PubMed

We demonstrate position-controlled III-V semiconductor nanowires (NWs) by using selective-area metal-organic vapor phase epitaxy and their application to solar cells. Efficiency of 4.23% is achieved for InP core-shell NW solar cells. We form a 'flexible NW array' without a substrate, which has the advantage of saving natural resources over conventional thin film photovoltaic devices. Four junction NW solar cells with over 50% efficiency are proposed and discussed. PMID:22434437

Fukui, Takashi; Yoshimura, Masatoshi; Nakai, Eiji; Tomioka, Katsuhiro

2012-01-01

193

Study of the electronic structure of model (110) surfaces and interfaces of semi-infinite III-V compound semiconductors: The GaSb-InAs system  

Microsoft Academic Search

This paper presents the results of a study of the electronic structure of model (110) surfaces and interfaces of semi-infinite III-V compound semiconductors, with specific application to the GaSb-InAs system. The description of the individual solids is sought within the empirical tight-binding method and combined with the Green's-function technique to account for their semi-infinite nature. Surface states are found to

N. V. Dandekar; A. Madhukar; D. N. Lowy

1980-01-01

194

Comparison for the carrier mobility between the III–V nitrides and AlGaAs/GaAs heterostructure field-effect transistors  

NASA Astrophysics Data System (ADS)

Using the measured capacitance-voltage curves of Ni/Au Schottky contacts with different areas and the current-voltage characteristics for the AlGaAs/GaAs, AlGaN/AlN/GaN and In0.18 Al0.82N/AlN/GaN heterostructure field-effect transistors (HFETs) at low drain-source voltage, the two-dimensional electron gas (2DEG) electron mobility for the prepared HFETs was calculated and analyzed. It was found that there is an obvious difference for the variation trend of the mobility curves between the III–V nitride HFETs and the AlGaAs/GaAs HFETs. In the III–V nitride HFETs, the variation trend for the curves of the 2DEG electron mobility with the gate bias is closely related to the ratio of the gate length to the drain-to-source distance. While the ratio of the gate length to the drain-to-source distance has no effect on the variation trend for the curves of the 2DEG electron mobility with the gate bias in the AlGaAs/GaAs HFETs. The reason is attributed to the polarization Coulomb field scattering in the III–V nitride HFETs.

Chongbiao, Luan; Zhaojun, Lin; Yuanjie, Lü; Zhihong, Feng; Jingtao, Zhao; Yang, Zhou; Ming, Yang

2014-09-01

195

Influence of PH3 exposure on silicon substrate morphology in the MOVPE growth of III-V on silicon multijunction solar cells  

NASA Astrophysics Data System (ADS)

Dual-junction solar cells formed by a GaAsP or GaInP top cell and a silicon bottom cell seem to be attractive candidates to materialize the long sought-for integration of III-V materials on silicon for photovoltaic applications. One of the first issues to be considered in the development of this structure will be the strategy to create the silicon emitter of the bottom subcell. In this study, we explore the possibility of forming the silicon emitter by phosphorus diffusion (i.e. exposing the wafer to PH3 in a MOVPE reactor) and still obtain good surface morphologies to achieve a successful III-V heteroepitaxy as occurs in conventional III-V on germanium solar cell technology. Consequently, we explore the parameter space (PH3 partial pressure, time and temperature) that is needed to create optimized emitter designs and assess the impact of such treatments on surface morphology using atomic force microscopy. Although a strong degradation of surface morphology caused by prolonged exposure of silicon to PH3 is corroborated, it is also shown that subsequent anneals under H2 can recover silicon surface morphology and minimize its RMS roughness and the presence of pits and spikes.

García-Tabarés, E.; García, I.; Martín, D.; Rey-Stolle, I.

2013-11-01

196

The effect of perturbed k -selection and gap shrinkage on the optical transitions in III–V semiconductors  

Microsoft Academic Search

Optical transitions in direct semiconductors are governed according to simple one-electron treatment by ak-selection rule, which in doped or mixed crystals is but lifted to some extent (?k) caused by 1) shallow impurities, 2) isoelectronic impurities or 3) alloy scattering. Values of ?k for these mechanisms are given and the implications for line shapes of optical spectra are discussed.

K. Unger; Sektion Physik; Karl-Marx-Universitdt Leipzig

1980-01-01

197

Self-Interaction Corrections to the Electronic Structure of II-VI and III-V Nitride Semiconductors  

Microsoft Academic Search

II-VI and group-III nitride semiconductors have paramount technological potential for applications in micro- and optoelectronics. A most accurate description of their bulk electronic structure as a basis for studying defect properties, band-edge properties in respective ternary or quaternary alloys and electronic properties of their surfaces and interfaces is of major importance, therefore. Standard LDA band-structure calculations for these wide-band-gap compounds

J. Pollmann

1998-01-01

198

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

199

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

200

Beyond CMOS: heterogeneous integration of III-V devices, RF MEMS and other dissimilar materials/devices with Si CMOS to create intelligent microsystems.  

PubMed

Advances in silicon technology continue to revolutionize micro-/nano-electronics. However, Si cannot do everything, and devices/components based on other materials systems are required. What is the best way to integrate these dissimilar materials and to enhance the capabilities of Si, thereby continuing the micro-/nano-electronics revolution? In this paper, I review different approaches to heterogeneously integrate dissimilar materials with Si complementary metal oxide semiconductor (CMOS) technology. In particular, I summarize results on the successful integration of III-V electronic devices (InP heterojunction bipolar transistors (HBTs) and GaN high-electron-mobility transistors (HEMTs)) with Si CMOS on a common silicon-based wafer using an integration/fabrication process similar to a SiGe BiCMOS process (BiCMOS integrates bipolar junction and CMOS transistors). Our III-V BiCMOS process has been scaled to 200?mm diameter wafers for integration with scaled CMOS and used to fabricate radio-frequency (RF) and mixed signals circuits with on-chip digital control/calibration. I also show that RF microelectromechanical systems (MEMS) can be integrated onto this platform to create tunable or reconfigurable circuits. Thus, heterogeneous integration of III-V devices, MEMS and other dissimilar materials with Si CMOS enables a new class of high-performance integrated circuits that enhance the capabilities of existing systems, enable new circuit architectures and facilitate the continued proliferation of low-cost micro-/nano-electronics for a wide range of applications. PMID:24567473

Kazior, Thomas E

2014-03-28

201

Calculation of III-III-V-V quaternary layer thickness grown by liquid phase epitaxy - application to InGaAsP  

NASA Astrophysics Data System (ADS)

The conceptions of the diffusion process of solute atoms and the liquid and solid composition variations derived from the phase diagram were combined successfully to calculate the III-III-V-V quaternary layer thickness for equilibrium cooling growth. The thickness of LPE In 1- xGa xAs 1- yP y layers was calculated using this model. The calculated results were compared with other calculated results based on the assumption of the uniform solution or the diffusion limited growth process.

Nakajima, Kazuo; Yamazaki, Susumu; Akita, Kenzo

1982-02-01

202

Solid-state ‘‘magic-angle’’ sample-spinning nuclear magnetic resonance spectroscopic study of group III–V (13–15) semiconductors  

Microsoft Academic Search

We have obtained 27 Al, 69 Ga, 71 Ga, 113 In, and 115 In static and ‘‘magic-angle’’ sample-spinning (MASS) solid-state nuclear magnetic resonance (NMR) spectra of a series of polycrystalline III–V semiconductors (AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, InN, InP, InAs, and InSb) at magnetic field strengths of 8.45 and 11.7 T. Line-broadening mechanisms have been identified by

Oc Hee Han; Hye Kyung C. Timken; Eric Oldfield

1988-01-01

203

Growth rate for the selective epitaxial growth of III-V compounds inside submicron shallow-trench-isolation trenches on Si (001) substrates by MOVPE: Modeling and experiments  

NASA Astrophysics Data System (ADS)

A mathematical model was developed to examine the growth rate of III-V compounds inside sub-micron trenches by MOVPE. Based on this model, we theoretically analyzed the possible dependence of the growth rate on the trench width primarily from two aspects, i.e. Knudson diffusion and enhanced equilibrium vapor pressure due to the shrinking trench size. Then, associated with the experimental data from the growth of both InAlAs and InAs, we found that the average growth rate inside submicron trenches is primarily influenced by trench diffusion type under typical growth conditions.

Jiang, S.; Merckling, C.; Guo, W.; Waldron, N.; Caymax, M.; Vandervorst, W.; Seefeldt, M.; Heyns, M.

2014-04-01

204

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

205

The role of lattice strain in the phase equilibria of III-V ternary and quaternary semiconductors  

NASA Astrophysics Data System (ADS)

Liquidus and solidus isotherms for ternary GaxIn1-xAs and AlxIn1-xAs and quaternary In1-xGaxAs1-yPy and In1-xGaxAs1-ySby alloy semiconductors have been calculated using the regular solution phase equilibria model for liquid phase epitaxial growth. The effect of lattice-mismatch strain in the growing layer has been incorporated in the model. Calculations have been made in order to make comparisons with published results of previous workers for both lattice-matched and mismatched layers. It is found that agreements are better with the inclusion of strain than with a zero-strain model.

Bhattacharya, Pallab K.; Srinivasa, Sobhana

1983-09-01

206

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

207

Study of the electronic surface states of III-V compounds and silicon. Final technical progress report 1 Oct 78-30 Sep 82. [HgCdTe  

SciTech Connect

The work performed over the four year span of this contract comprises a large body of research. Its results are summarized in this document. The technical problem was to study the electronic and atomic structure of the surfaces of several semiconductors. The III-V compound semiconductors, especially GaAs, InP, and GaSb, and the column IV semiconductor Si were emphasized, but some work on Ge and HgCdTe was also performed. The predominant methodology used was laboratory experimentation: photoemission spectroscopy excited by synchrotron radiation was utilized heavily, along with angle-resolved photoemission, photoemission excited by conventional ultraviolet and x-ray illumination, low energy electron diffraction, Auger electron spectroscopy, contact potential difference (Kelvin probe) measurements, as well as other techniques which are detailed in the publications.

Spicer, W.E.; Lindau, I.

1982-09-30

208

Low-driving-current InGaAsP photonic-wire optical switches using III-V CMOS photonics platform.  

PubMed

Electrically-driven Mach-Zehnder interferometer type InGaAsP photonic-wire optical switches have been demonstrated using a III-V-on-insulator structure bonded on a thermally oxidized Si with an Al(2)O(3)/InP bonding interfacial layer which enables strong wafer bonding and low propagation loss. Lateral p-i-n junctions in the InGaAsP photonic-wire waveguides were formed by using ion implantation for changing refractive index in the InGaAsP waveguide through carrier injection. Optical switching with 10 dB extinction ratio was achieved with driving current of 200 µA which is approximately 10 times smaller than that of Si photonic-wire optical switch owing to larger free-carrier effect in InGaAsP than that in Si. PMID:23262873

Ikku, Yuki; Yokoyama, Masafumi; Ichikawa, Osamu; Hata, Masahiko; Takenaka, Mitsuru; Takagi, Shinichi

2012-12-10

209

New III-V cell design approaches for very high efficiency. Annual subcontract report, 1 August 1991--31 July 1992  

SciTech Connect

This report describes to examine new solar cell desip approaches for achieving very high conversion efficiencies. The program consists of two elements. The first centers on exploring new thin-film approaches specifically designed for M-III semiconductors. Substantial efficiency gains may be possible by employing light trapping techniques to confine the incident photons, as well as the photons emitted by radiative recombination. The thin-film approach is a promising route for achieving substantial performance improvements in the already high-efficiency, single-junction, III-V cell. The second element of the research involves exploring desip approaches for achieving high conversion efficiencies without requiring extremely high-quality material. This work has applications to multiple-junction cells, for which the selection of a component cell often involves a compromise between optimum band pp and optimum material quality. It could also be a benefit manufacturing environment by making the cell`s efficiency less dependent on materialquality.

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

1993-04-01

210

In situ control of Si(100) and Ge(100) surface preparation for the heteroepitaxy of III-V solar cell architectures  

NASA Astrophysics Data System (ADS)

Si(100) and Ge(100) substrates essential for subsequent III-V integration were studied in the hydrogen ambient of a metalorganic vapor phase epitaxy reactor. Reflectance anisotropy spectroscopy (RAS) enabled us to distinguish characteristic configurations of vicinal Si(100) in situ: covered with oxide, cleaned by thermal removing in H2, and terminated with monohydrides when cooling in H2 ambient. RAS measurements during cooling in H2 ambient after the oxide removal process revealed a transition from the clean to the monohydride terminated Si(100) surface dependent on process temperature. For vicinal Ge(100) we observed a characteristic RA spectrum after annealing and cooling in H2 ambient. According to results from X-ray photo electron spectroscopy and Fourier-transform infrared spectroscopy the spectrum corresponds to the monohydride terminated Ge(100) surface.

Brückner, Sebastian; Supplie, Oliver; Barrigón, Enrique; Dobrich, Anja; Luczak, Johannes; Löbbel, Claas; Rey-Stolle, Ignacio; Kleinschmidt, Peter; Döscher, Henning; Hannappel, Thomas

2012-10-01

211

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

212

Boron alloying of GaN  

NASA Astrophysics Data System (ADS)

The III-V semiconductor GaN has received considerable attention due to its wide band gap. Using LDA calculations, we studied the effects of boron incorporation in GaN (zincblende). Lattice parameters and band gap energies for B_xGa_1-xN supercells were computed. For small boron concentrations, the GaN band gap increased slightly and a band gap bowing parameter was determined. Strain energy calculations were also performed to determine whether boron incorporation could resolve the lattice mismatch in wide band gap semicounductor alloys. Formation enthalpies of B_xGa_1-xN, B_xGa_1-xAs, and GaAs_1-xNx were compared.

Escalanti, Laurian; Hart, Gus L. W.

2003-03-01

213

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

214

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

215

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

216

Large-signal characterizations of DDR IMPATT devices based on group III-V semiconductors at millimeter-wave and terahertz frequencies  

NASA Astrophysics Data System (ADS)

Large-signal (L-S) characterizations of double-drift region (DDR) impact avalanche transit time (IMPATT) devices based on group III-V semiconductors such as wurtzite (Wz) GaN, GaAs and InP have been carried out at both millimeter-wave (mm-wave) and terahertz (THz) frequency bands. A L-S simulation technique based on a non-sinusoidal voltage excitation (NSVE) model developed by the authors has been used to obtain the high frequency properties of the above mentioned devices. The effect of band-to-band tunneling on the L-S properties of the device at different mm-wave and THz frequencies are also investigated. Similar studies are also carried out for DDR IMPATTs based on the most popular semiconductor material, i.e. Si, for the sake of comparison. A comparative study of the devices based on conventional semiconductor materials (i.e. GaAs, InP and Si) with those based on Wz-GaN shows significantly better performance capabilities of the latter at both mm-wave and THz frequencies.

Acharyya, Aritra; Mallik, Aliva; Banerjee, Debopriya; Ganguli, Suman; Das, Arindam; Dasgupta, Sudeepto; Banerjee, J. P.

2014-08-01

217

Electrochemically synthesized broadband antireflective and hydrophobic GaOOH nanopillars for III-V InGaP/GaAs/Ge triple-junction solar cell applications.  

PubMed

We report the efficiency enhancement of III-V InGaP/GaAs/ Ge triple-junction (TJ) solar cells using a novel structure, i.e., vertically-oriented gallium oxide hydroxide (GaOOH) nanopillars (NPs), as an antireflection coating. The optical reflectance properties of rhombus-shaped GaOOH NPs, which were synthesized by a simple, low-cost, and large-scalable electrochemical deposition method, were investigated, together with a theoretical analysis using the rigorous coupled-wave analysis method. For the GaOOH NPs, the solar weighted reflectance of ~8.5% was obtained over a wide wavelength range of 300-1800 nm and their surfaces exhibited a high water contact angle of ~130° (i.e., hydrophobicity). To simply demonstrate the feasibility of device applications, the GaOOH NPs were incorporated into a test-grown InGaP/GaAs/Ge TJ solar cell structure. For the InGaP/GaAs/Ge TJ solar cell with broadband antireflective GaOOH NPs, the conversion efficiency (?) of ~16.47% was obtained, indicating an increased efficiency by 3.47% compared to the bare solar cell (i.e., ?~13%). PMID:24922242

Leem, Jung Woo; Lee, Hee Kwan; Jun, Dong-Hwan; Heo, Jonggon; Park, Won-Kyu; Park, Jin-Hong; Yu, Jae Su

2014-03-10

218

Basic moments of phonon density of states spectra and characteristic phonon temperatures of group IV, III-V, and II-VI materials  

NASA Astrophysics Data System (ADS)

We have redigitized a large variety of phonon density of states (PDOS) spectra, that have been published by diferent researchers for group IV (diamond, 3C-SiC, Si, and Ge), III-V (BN, BP, BAs, BSb, AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, InN, InP, InAs, and InSb), and II-VI materials (ZnO, ZnS, ZnSe, ZnTe, CdS, and CdTe), including calculations of their moments, ??n?, of orders n =-1, 1, 2, and 4. Notwithstanding the obvious differences in concrete shapes of spectra presented for one and the same material by different authors, the respective magnitudes of estimated moments have been found in most cases to be nearly the same (to within uncertainties of some few percent). For most materials under study, the average phonon temperatures of the lower and upper sections of PDOS spectra, ?L and ?U, are found to be by factors of order 0.6 lower or 1.4 higher, respectively, than the average phonon temperature, ?P, of the total PDOS spectra. The estimated high-temperature limits of Debye temperatures, ?D(?), are found to be significantly higher (by factors of order 1.4) than ?P, implying an order-of-magnitude equality, ?D(?)??U (within differences not exceeding an order of ±10%, for all materials under study). The phonon temperatures, ?g, that are effective in controlling the observable temperature dependences of fundamental energy gaps, Eg(T), are found to be usually of the same order as the respective average phonon temperatures, ?g??P. The existing differences between these two qualitatively different types of characteristic phonon temperatures are seen to be limited, for diamond, 3C-SiC, Si, Ge, AlN, GaN, GaP, GaAs, GaSb, InP, InSb, ZnS, ZnSe, ZnTe, and CdTe, to an order of ±12%. We design an exemplary way for precalculating harmonic parts of isochoric heat capacities on the basis of the estimated quadruplets of PDOS spectra moments. This novel calculation scheme is exemplified for silicon and germanium.

Pässler, Roland

2007-05-01

219

Heusler alloys  

Microsoft Academic Search

In 1903 F. Heusler reported that it was possible to make ferromagnetic alloys from non-ferromagnetic constituents copper-manganese bronze and group B elements such as aluminium and tin. Further investigations showed that the magnetic properties of these alloys are related to their chemical, L21, structure, and to the ordering of the manganese atoms on an f.c.c. sublattice.Heusler alloys are properly described

Peter J. Webster

1969-01-01

220

A standards-based method for compositional analysis by energy dispersive X-ray spectrometry using multivariate statistical analysis: application to multicomponent alloys.  

PubMed

Given an unknown multicomponent alloy, and a set of standard compounds or alloys of known composition, can one improve upon popular standards-based methods for energy dispersive X-ray (EDX) spectrometry to quantify the elemental composition of the unknown specimen? A method is presented here for determining elemental composition of alloys using transmission electron microscopy-based EDX with appropriate standards. The method begins with a discrete set of related reference standards of known composition, applies multivariate statistical analysis to those spectra, and evaluates the compositions with a linear matrix algebra method to relate the spectra to elemental composition. By using associated standards, only limited assumptions about the physical origins of the EDX spectra are needed. Spectral absorption corrections can be performed by providing an estimate of the foil thickness of one or more reference standards. The technique was applied to III-V multicomponent alloy thin films: composition and foil thickness were determined for various III-V alloys. The results were then validated by comparing with X-ray diffraction and photoluminescence analysis, demonstrating accuracy of approximately 1% in atomic fraction. PMID:23298470

Rathi, Monika; Ahrenkiel, S P; Carapella, J J; Wanlass, M W

2013-02-01

221

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

222

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

223

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

224

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

225

Nanoscale assembly of silicon-like [Al(As1-xNx)]ySi5-2y alloys: Fundamental theoretical and experimental studies of structural and optical properties  

NASA Astrophysics Data System (ADS)

Ab initio theoretical simulations of Al(As1-xNx)Si3 alloys, a new class of optoelectronic materials, confirm that these compounds are likely to be disordered via a mechanism that preserves the integrity of the constituent III-V-Si3 tetrahedra but randomizes their orientation in the average diamond lattice of the compound. This type of disorder is consistent with experimental structural data and with the proposed growth mechanism for such alloys, according to which “III:V(SiH3)3” intermediate complexes are formed in the gas phase from reactions between group-III atomic beams and V(SiH3)3 molecules, delivering the entire III-V-Si3 tetrahedra to the growing film. Experimental optical studies of these Al(As1-xNx)Si3 alloys as well as more general [Al(As1-xNx)]ySi5-2y compounds grown on Si substrates were carried out using spectroscopic ellipsometry. The resulting dielectric functions are found to be similar to broadened versions of their counterparts in pure Si. This broadening may have important practical applications, particularly in photovoltaics, because it dramatically enhances the optical absorption of Si in the visible range of the electromagnetic spectrum. A critical point analysis reveals the existence of direct optical transitions at energies as low as 2.5 eV, well below the lowest direct absorption edge of Si at 3.3 eV. Such transitions are predicted theoretically for perfectly ordered III-V-Si3 compounds, and the experimental results suggest that they are robust against tetrahedra orientational disorder.

Jiang, L.; Sims, P. E.; Grzybowski, G.; Beeler, R. T.; Chizmeshya, A. V. G.; Smith, D. J.; Kouvetakis, J.; Menéndez, J.

2013-07-01

226

Distributed feedback GaSb based laser diodes with buried grating  

SciTech Connect

We report on the growth, fabrication, and experimental study of distributed feed-back antimonide diode lasers with buried grating. A second order index-coupled grating was defined by interferometric lithography on the top of the laser waveguide and dry etched by reactive ion etching. The grating was then buried thanks to an overgrowth of the top cladding layer using molecular beam epitaxy. The wafer was then processed using standard photolithography and wet etching into 15??m-wide laser ridges. Single frequency laser emission at a wavelength of 2.2??m was measured with a side mode suppression ratio of 34?dB, a maximum output power of 30 mW, and a total continuous tuning range of 6.5?nm.

Gaimard, Q.; Cerutti, L.; Teissier, R.; Vicet, A. [IES, UMR CNRS 5214, CC067, Université Montpellier 2, Place Eugene Bataillon, 34095 Montpellier Cedex 05 (France)

2014-04-21

227

VAl Alloy  

NASA Astrophysics Data System (ADS)

Power generation performance of a thermoelectric module consisting of the Heusler Fe2VAl alloy was evaluated. For construction of the module, W-doped Fe2VAl alloys were prepared using powder metallurgy process. Power generation tests of the module consisting of 18 pairs of p- n junctions were conducted on a heat source of 373-673 K in vacuum. The reduction of thermal conductivity and improvement of thermoelectric figure of merit by W-doping enhanced the conversion efficiency and the output power. High output power density of 0.7 W/cm2 was obtained by virtue of the high thermoelectric power factor of the Heusler alloy. The module exhibited good durability, and the relatively high output power was maintained after temperature cycling test in air.

Mikami, M.; Mizoshiri, M.; Ozaki, K.; Takazawa, H.; Yamamoto, A.; Terazawa, Y.; Takeuchi, T.

2014-06-01

228

Electronic Band Structure of GaNxPyAs1-x -y Highly Mismatched Alloys: Suitability for Intermediate-Band Solar Cells  

NASA Astrophysics Data System (ADS)

Formation of an intermediate band in GaNxP0.4As0.6-x alloys due to the isovalent doping by nitrogen is studied by photoreflectance and absorption spectroscopy. The fundamental energy gap transition (E0) observed for an N-free alloy is replaced by two optical transitions (E- and E+) in GaNPAs layers. The E - and E+ transitions are explained within the band anticrossing model, where the localized level of nitrogen interacts with the conduction band of the GaPAs host, splitting it into two subbands. The valence band (VB) is mostly unaffected by nitrogen incorporation as confirmed by the same spin-orbit splitting for N-free and N-containing alloys. The energy position of the E - subband and a strong optical absorption between the VB and the E- subband indicates the GaNPAs alloys have an electronic structure suitable for intermediate-band solar cells. Such an electronic structure is not observed for other III-V alloys like GaInAs, GaInAsP, etc., for which the virtual crystal approximation can be applied to describe the evolution of the electronic structure with the alloy content. Results obtained in this work clearly show that GaNPAs with a few percent of nitrogen is an unusual material system, for which the electronic structure properties differ very significantly from properties of well-known III-V alloys, and the application of virtual crystal approximation in this case is inappropriate or very limited.

Kudrawiec, R.; Luce, A. V.; Gladysiewicz, M.; Ting, M.; Kuang, Y. J.; Tu, C. W.; Dubon, O. D.; Yu, K. M.; Walukiewicz, W.

2014-04-01

229

Alloy softening in binary molybdenum alloys  

NASA Technical Reports Server (NTRS)

An investigation was conducted to determine 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. 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. Alloy softening and 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

230

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

231

Spin injection from Heusler alloys into semiconductors: A materials perspective  

NASA Astrophysics Data System (ADS)

The notion of using electron spins as bits for highly efficient computation coupled with non-volatile data storage has driven an intense international research effort over the past decade. Such an approach, known as spin-based electronics or spintronics, is considered to be a promising alternative to charge-based electronics in future integrated circuit technologies. Many proposed spin-based devices, such as the well-known spin-transistor, require injection of spin polarized currents from ferromagnetic layers into semiconductor channels, where the degree of injected spin polarization is crucial to the overall device performance. Several ferromagnetic Heusler alloys are predicted to be half-metallic, meaning 100% spin-polarized at the Fermi level, and hence considered to be excellent candidates for electrical spin injection. Furthermore, they exhibit high Curie temperatures and close lattice matching to III-V semiconductors. Despite their promise, Heusler alloy/semiconductor heterostructures investigated in the past decade have failed to fulfill the expectation of near perfect spin injection and in certain cases have even demonstrated inferior behavior compared to their elemental ferromagnetic counterparts. To address this problem, a slew of theoretical and experimental work has emerged studying Heusler alloy/semiconductor interface properties. Here, we review the dominant prohibitive materials challenges that have been identified, namely atomic disorder in the Heusler alloy and in-diffusion of magnetic impurities into the semiconductor, and their ensuing detrimental effects on spin injection. To mitigate these effects, we propose the incorporation of half-metallic Heusler alloys grown at high temperatures (>200 °C) along with insertion of a MgO tunnel barrier at the ferromagnet/semiconductor interface to minimize magnetic impurity in-diffusion and potentially act as a spin-filter. By considering evidence from a variety of structural, optical, and electrical studies, we hope to paint a realistic picture of the materials environment encountered by spins upon injection from Heusler alloys into semiconductors. Finally, we review several emerging device paradigms that utilize Heusler alloys as sources of spin polarized electrons.

Farshchi, R.; Ramsteiner, M.

2013-05-01

232

Metal alloy identifier  

DOEpatents

To identify the composition of a metal alloy, sparks generated from the alloy are optically observed and spectrographically analyzed. The spectrographic data, in the form of a full-spectrum plot of intensity versus wavelength, provide the "signature" of the metal alloy. This signature can be compared with similar plots for alloys of known composition to establish the unknown composition by a positive match with a known alloy. An alternative method is to form intensity ratios for pairs of predetermined wavelengths within the observed spectrum and to then compare the values of such ratios with similar values for known alloy compositions, thereby to positively identify the unknown alloy composition.

Riley, William D. (Avondale, MD); Brown, Jr., Robert D. (Avondale, MD)

1987-01-01

233

Surface phonons of III-V semiconductors  

E-print Network

are the simplest of all semiconductor surfaces. Their atomic relaxations and electronic surface states are rather well understood. There have, however, been surprisingly few experimental studies of their vibrational properties, and ours in the first detailed...

Das, Pradip Kumar

2012-06-07

234

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

235

Calorizing of nickel alloys  

Microsoft Academic Search

1.Calorizing of the ÉI867, ÉI929, and ZhS6K alloys at 850–1100°C for 2–8 h leads to the formation of a surface layer which considerably increases the resistance of these alloys to oxidation.2.The thickness of the layer, the incease in weight, the heat resistance, and the hardness of the three calorized alloys are the same.3.Calorizing of nickel alloys leads to an increase

V. V. Terekhova; A. G. Andreeva

1965-01-01

236

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

237

Alloying of aluminum-beryllium alloys  

NASA Astrophysics Data System (ADS)

The existing phase diagrams of Al-Be- X alloys, where X is an alloying element, are analyzed. Element X is noted to poorly dissolve in both aluminum and beryllium. It is shown that the absence of intermetallic compounds in the Al-Be system affects the phase equilibria in an Al-Be- X system. Possible phase equilibria involving phases based on aluminum, beryllium, and intermetallic compounds are proposed, and the types of strengthening of Al-Be alloys by an addition of a third element are classified.

Molchanova, L. V.; Ilyushin, V. N.

2013-01-01

238

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

239

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

240

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

241

In situ measurement of CuPt alloy ordering using strain anisotropy  

SciTech Connect

The optical and electrical properties of many III-V alloys change with the degree of CuPt atomic ordering, which is very sensitive to growth conditions. The bulk ordered alloy is elongated along the normal to the ordered planes, and is asymmetrically strained when coherent to a cubic substrate. Here, we demonstrate in situ measurement of the anisotropic strain due to ordering using two-dimensional wafer curvature. The measurement is sensitive to bulk anisotropies, and so is complementary to other in situ measurements that are sensitive to surface anisotropies. Using ab initio calculations, we determine a maximum strain anisotropy of 0.27% between [110] and [1{sup ¯}10] when perfectly ordered single-variant GaInP{sub 2} is coherent to a (001) cubic substrate. We relate the in situ measurement of strain anisotropy on various GaInP{sub 2} samples to ex situ measurements of the order parameter to validate the measurement and confirm the capability to predict material properties. The measurement monitors change in ordering during growth, useful for quickly determining the growth condition dependence of ordering or monitoring order-disorder transitions. More generally, this measurement technique could, in principle, be used to monitor phase changes in any epitaxial system for which the strain anisotropy of the two phases differs.

France, Ryan M.; McMahon, William E.; Kang, Joongoo; Steiner, Myles A.; Geisz, John F. [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States)

2014-02-07

242

Nickel base coating alloy  

NASA Technical Reports Server (NTRS)

Zirconium is added to a Ni-30 Al (beta) intermetallic alloy in the range of 0.05 w/o to 0.25 w/o. This addition is made during melting or by using metal powders. The addition of zirconium improves the cyclic oxidation resistance of the alloys at temperatures above 1100 C.

Barrett, C. A. (inventor); Lowell, C. E. (inventor)

1986-01-01

243

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 sources 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, William V. (Boulder, CO)

1983-01-01

244

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

245

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

246

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

247

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

248

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

249

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

250

Magnesium secondary alloys: Alloy design for magnesium alloys with improved tolerance limits against impurities  

Microsoft Academic Search

The development of secondary magnesium alloys requires a completely different concept compared with standard alloys which obtain their corrosion resistance by reducing the levels of impurities below certain alloy and process depending limits. The present approach suitable for Mg–Al based cast and wrought alloys uses a new concept replacing the ?-phase by ?-phase, which is able to incorporate more impurities

C. Blawert; D. Fechner; D. Höche; V. Heitmann; W. Dietzel; K. U. Kainer; P. Živanovi?; C. Scharf; A. Ditze; J. Gröbner; R. Schmid-Fetzer

2010-01-01

251

Analysis of niobium alloys.  

PubMed

An ion-exchange method was applied to the analysis of synthetic mixtures representing various niobium-base alloys. The alloying elements which were separated and determined include vanadium, zirconium, hafnium, titanium, molybdenum, tungsten and tantalum. Mixtures containing zirconium or hafnium, tungsten, tantalum and niobium were separated by means of a single short column. Coupled columns were employed for the resolution of mixtures containing vanadium, zirconium or titanium, molybdenum, tungsten and niobium. The separation procedures and the methods employed for the determination of the alloying elements in their separate fractions are described. PMID:18960385

Ferraro, T A

1968-09-01

252

Lattice constant grading in the Al.sub.y Ca.sub.1-y As.sub.1-x Sb.sub.x alloy system  

DOEpatents

Liquid phase epitaxy is employed to grow a lattice matched layer of GaAsSb on GaAs substrates through the compositional intermediary of the III-V alloy system AlGaAsSb which acts as a grading layer. The Al constituent reaches a peak atomic concentration of about 6% within the first 2.5.mu.m of the transition layer, then decreases smoothly to about 1% to obtain a lattice constant of 5.74 A. In the same interval the equilibrium concentration of Sb smoothly increases from 0 to about 9 atomic percent to form a surface on which a GaAsSb layer having the desired energy bandgap of 1.1 ev for one junction of an optimized dual junction photovoltaic device. The liquid phase epitaxy is accomplished with a step cooling procedure whereby dislocation defects are more uniformly distributed over the surface of the growing layer.

Moon, Ronald L. (Palo Alto, CA)

1981-01-01

253

Lattice constant grading in the Al.sub.y Ga.sub.1-y As.sub.1-x Sb.sub.x alloy system  

DOEpatents

Liquid phase epitaxy is employed to grow a lattice matched layer of GaAsSb on GaAs substrates through the compositional intermediary of the III-V alloy system AlGaAsSb which acts as a grading layer. The Al constituent reaches a peak atomic concentration of about 6% within the first 2.5 .mu.m of the transition layer, then decreases smoothly to about 1% to obtain a lattice constant of 5.74 A. In the same interval the equilibrium concentration of Sb smoothly increases from 0 to about 9 atomic percent to form a surface on which a GaAsSb layer having the desired energy bandgap of 1.1 ev for one junction of an optimized dual junction photolvoltaic device. The liquid phase epitaxy is accomplished with a step cooling procedure whereby dislocation defects are more uniformly distributed over the surface of growing layer.

Moon, Ronald L. (Palo Alto, CA)

1980-01-01

254

Electroplating on titanium alloy  

NASA Technical Reports Server (NTRS)

Activation process forms adherent electrodeposits of copper, nickel, and chromium on titanium alloy. Good adhesion of electroplated deposits is obtained by using acetic-hydrofluoric acid anodic activation process.

Lowery, J. R.

1971-01-01

255

Subtyping in alloy  

E-print Network

A type system for the Alloy modelling language is described that supports subtypes and allows overloading of relation names. No special syntactic features needed to be added to the language to support the type system; there ...

Torlak, Emina, 1979-

2004-01-01

256

Nanocrystalline intermetallics and alloys  

Microsoft Academic Search

Nanocrystalline intermetallics and alloys are novel materials with high surface areas which are potential low-cost and high-performance\\u000a catalysts. Here, we report a general approach to the synthesis of a large variety of nanocrystalline intermetallics and alloys\\u000a with controllable composition, size, and morphology: these include Au-, Pd-, Pt-, Ir-, Ru-, and Rh-based bi- or tri-metallic\\u000a nanocrystals. We find that only those

Dingsheng Wang; Qing Peng; Yadong Li

2010-01-01

257

Modeling dissolution in aluminum alloys  

Microsoft Academic Search

Aluminum and its alloys are used in many aspects of modern life, from soda cans and household foil to the automobiles and aircraft in which we travel. Aluminum alloy systems are characterized by good workability that enables these alloys to be economically rolled, extruded, or forged into useful shapes. Mechanical properties such as strength are altered significantly with cold working,

Tracie Lee Durbin

2005-01-01

258

Process for Nonequilibrium Ternary Alloys  

NASA Technical Reports Server (NTRS)

Proposed metallurgical process yields amorphous ternary alloys of any range of desired compositions. Process produces homogenous alloys even when proportions of constituent metals are not those that exist in equilibrium at solidification temperature. Such alloys are well suited to use in gas turbines and advanced engines.

Lutwack, R.

1986-01-01

259

Surface modification of high temperature iron alloys  

DOEpatents

A method and article of manufacture of a coated iron based alloy. The method includes providing an iron based alloy substrate, depositing a silicon containing layer on the alloy surface while maintaining the alloy at a temperature of about 700.degree. C.-1200.degree. C. to diffuse silicon into the alloy surface and exposing the alloy surface to an ammonia atmosphere to form a silicon/oxygen/nitrogen containing protective layer on the iron based alloy.

Park, Jong-Hee (Clarendon Hills, IL)

1995-01-01

260

Surface modification of high temperature iron alloys  

DOEpatents

A method and article of manufacture of a coated iron based alloy are disclosed. The method includes providing an iron based alloy substrate, depositing a silicon containing layer on the alloy surface while maintaining the alloy at a temperature of about 700--1200 C to diffuse silicon into the alloy surface and exposing the alloy surface to an ammonia atmosphere to form a silicon/oxygen/nitrogen containing protective layer on the iron based alloy. 13 figs.

Park, J.H.

1995-06-06

261

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

262

Magnesium and magnesium alloys  

Microsoft Academic Search

This new handbook is the most comprehensive publication of engineering information on commercial magnesium alloys under one cover in the last sixty years. Prepared with the cooperation of the International Magnesium Association, it presents the industrial practices currently used throughout the world, as well as the properties of the products critical to their proper application. Contents include: general characteristics; physical

M. Avedesian; H. Baker

1998-01-01

263

Shape Memory Alloy Actuator  

NASA Technical Reports Server (NTRS)

The present invention discloses and teaches a unique, remote optically controlled micro actuator particularly suitable for aerospace vehicle applications wherein hot gas, or in the alternative optical energy, is employed as the medium by which shape memory alloy elements are activated. In gas turbine powered aircraft the source of the hot gas may be the turbine engine compressor or turbine sections.

Baumbick, Robert J. (Inventor)

2000-01-01

264

Shape Memory Alloy Actuator  

NASA Technical Reports Server (NTRS)

The present invention discloses and teaches a unique, remote optically controlled micro actuator particularly suitable for aerospace vehicle applications wherein hot gas, or in the alternative optical energy, is employed as the medium by which shape memory alloy elements are activated. In gas turbine powered aircraft the source of the hot gas may be the turbine engine compressor or turbine sections.

Baumbick, Robert J. (Inventor)

2002-01-01

265

Characterizing alloy additions to high nitrogen steels  

Microsoft Academic Search

Numerous articles of individual high nitrogen stainless steel compositions or alloys with near identical alloy compositions have been published characterizing the properties the alloy or the improvement which an individual element contributes to the base alloy's properties. In this study a series of high nitrogen steels alloys were prepared with the intent of characterizing the advantages and limitations of different

James C. Rawers; Joseph H. Tylczak; D. Blankenship; Sophie J. Bullard

2003-01-01

266

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

267

Filler metal alloy for welding cast nickel aluminide alloys  

DOEpatents

A filler metal alloy used as a filler for welding east 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 east in copper chill molds.

Santella, Michael L. (Knoxville, TN); Sikka, Vinod K. (Oak Ridge, TN)

1998-01-01

268

(NH{sub 4})[V{sub 1-x}{sup III}V{sub x}{sup IV}(AsO{sub 4})F{sub 1-x}O{sub x}]: A new mixed valence vanadium(III,IV) fluoro-arsenate with ferromagnetic interactions and electronic conductivity  

SciTech Connect

A new mixed valence vanadium(III,IV) fluoro-arsenate compound, with formula (NH{sub 4})[V{sub 1-x}{sup III}V{sub x}{sup IV}(AsO{sub 4})F{sub 1-x}O{sub x}] and KTP structure-type, has been synthesized by mild hydrothermal techniques. The crystal structure has been solved from single crystal X-ray diffraction data in the Pna2{sub 1} orthorhombic space group. The unit-cell parameters are a=13.196(2) A, b=6.628(1) A and c=10.7379(7) A with Z=8. The final R factors were R1=0.0438 and wR2=0.0943 [all data]. The crystal structure consists of a three-dimensional framework formed by (V{sup III,IV}O{sub 4}F{sub 2}) octahedra and (AsO{sub 4}){sup 3-} tetrahedra arsenate oxoanions. The vanadium(III,IV) cations, from the (V{sup III,IV}O{sub 4}F{sub 2}) octahedra, are linked through the fluorine atoms giving rise to zigzag chains. The ammonium cations are located in the cavities of the structure compensating the anionic charge of the [V{sub 1-x}{sup III}V{sub x}{sup IV}(AsO{sub 4})F{sub 1-x}O{sub x}]{sup -} inorganic skeleton. The thermal stability limit of the phase is 345 deg. C, around to this temperature the ammonium cation and fluoride anion are lost. The IR spectrum shows the characteristic bands of the (NH{sub 4}){sup +} and (AsO{sub 4}){sup 3-} ions. Magnetic measurements indicate the existence of weak ferromagnetic interactions. Electronic conductivity, via a hopping mechanism, occurs with an activation energy of 0.66 eV. - Graphical abstract: Polyhedral view of the crystal structure of (NH{sub 4})[V{sup III}{sub 1-x}V{sup IV}{sub x}(AsO{sub 4})F{sub 1-x}O{sub x}].

Berrocal, Teresa [Departamento de Mineralogia y Petrologia, Facultad de Ciencia y Tecnologia, Universidad del Pais Vasco/EHU, Apdo. 644, E-48080 Bilbao (Spain); Mesa, Jose L. [Departamento de Quimica Inorganica, Facultad de Ciencia y Tecnologia, Universidad del Pais Vasco/EHU, Apdo. 644, E-48080 Bilbao (Spain)], E-mail: joseluis.mesa@ehu.es; Pizarro, Jose L.; Bazan, Begona [Departamento de Mineralogia y Petrologia, Facultad de Ciencia y Tecnologia, Universidad del Pais Vasco/EHU, Apdo. 644, E-48080 Bilbao (Spain); Ruiz de Larramendi, Idoia [Departamento de Quimica Inorganica, Facultad de Ciencia y Tecnologia, Universidad del Pais Vasco/EHU, Apdo. 644, E-48080 Bilbao (Spain); Arriortua, Maria I. [Departamento de Mineralogia y Petrologia, Facultad de Ciencia y Tecnologia, Universidad del Pais Vasco/EHU, Apdo. 644, E-48080 Bilbao (Spain); Rojo, Teofilo [Departamento de Quimica Inorganica, Facultad de Ciencia y Tecnologia, Universidad del Pais Vasco/EHU, Apdo. 644, E-48080 Bilbao (Spain)

2009-01-15

269

Two phase titanium aluminide alloy  

DOEpatents

A two-phase titanic aluminide alloy having a lamellar microstructure with little intercolony structures. The alloy can include fine particles such as boride particles at colony boundaries and/or grain boundary equiaxed structures. The alloy can include alloying additions such as .ltoreq.10 at % W, Nb and/or Mo. The alloy can be free of Cr, V, Mn, Cu and/or Ni and can include, in atomic %, 45 to 55% Ti, 40 to 50% Al, 1 to 5% Nb, 0.3 to 2% W, up to 1% Mo and 0.1 to 0.3% B. In weight %, the alloy can include 57 to 60% Ti, 30 to 32% Al, 4 to 9% Nb, up to 2% Mo, 2 to 8% W and 0.02 to 0.08% B.

Deevi, Seetharama C. (Midlothian, VA); Liu, C. T. (Oak Ridge, TN)

2001-01-01

270

Salt corrosion of titanium alloys  

Microsoft Academic Search

1.The long-term strength (1000 h) of commercial titanium alloys does not decrease under the influence of a film of NaCl at temperatures of 250° or lower.2.With increasing testing temperatures the susceptibility of the alloys to salt increases.3.Natural sea salt is more corrosive than NaCl at temperatures of 250° and higher.4.The corrosion resistance of titanium alloys in contact with salt depends

V. P. Batrakov; L. N. Pivovarova; L. V. Zakharova

1974-01-01

271

Amorphous metal alloy and composite  

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, Rong (Richland, WA); Merz, Martin D. (Richland, WA)

1985-01-01

272

Pareto-optimal alloys  

NASA Astrophysics Data System (ADS)

Large databases that can be used in the search for new materials with specific properties remain an elusive goal in materials science. The problem is complicated by the fact that the optimal material for a given application is usually a compromise between a number of materials properties and the cost. In this letter we present a database consisting of the lattice parameters, bulk moduli, and heats of formation for over 64 000 ordered metallic alloys, which has been established by direct first-principles density-functional-theory calculations. Furthermore, we use a concept from economic theory, the Pareto-optimal set, to determine optimal alloy solutions for the compromise between low compressibility, high stability, and cost.

Bligaard, Thomas; Jóhannesson, Gisli H.; Ruban, Andrei V.; Skriver, Hans L.; Jacobsen, Karsten W.; Nørskov, Jens K.

2003-12-01

273

Growth kinetics and investigations of spontaneous formation of superlattices in AlGaN alloys  

NASA Astrophysics Data System (ADS)

GaN and its alloys with AlN constitute a very important class of materials with a broad range of potential applications in ultraviolet optoelectronic devices, high frequency, high temperature and high power electronic devices and sensors based on micro-electromechanical devices. This work addresses the kinetics of growth of AlGaN alloys by molecular beam epitaxy and the study of spontaneous formation of superlattices of various periodicities. High quality films were grown epitaxially by plasma assisted MBE on sapphire substrates employing appropriate buffer layers. The nature of the buffer layer was found to control the polarity of the films. The ratio of the group-III to group-V atomic fluxes during growth was found to control the adatom surface diffusion and the incorporation of Ga atoms, as well as the film's structural and optical properties. Films grown under nitrogen rich conditions show a rough morphology due to reduced surface diffusion, while films grown under group-III rich conditions are atomically smooth. The growth kinetics of the AlGaN films were investigated at the substrate temperature range of 750 to 800°C and found to be drastically different than in the case of traditional III-V compounds. The sticking probability of aluminum atoms is unity while the sticking probability of gallium is constant only under nitrogen rich growth conditions. In the group-III rich growth regime the sticking probability of gallium decreases monotonically with group-III fluxes since the available active nitrogen bonds preferentially to Al. The spontaneous formation of superlattices in the films during growth was investigated. The formation of superlattices with period of two monolayers was found to be promoted by nitrogen rich conditions of growth on nitrogen polar surfaces. Furthermore, superlattices with longer periods (seven and twelve monolayers) were observed in films grown on gallium polar surfaces. The optical properties of the GaN and AlGaN films were investigated by transmission, luminescence and photoconductivity measurements in the entire alloy composition. A reduction in the direct bandgap of the alloys was correlated with the presence of long range atomic order of group-III atoms.

Iliopoulos, Eleftherios

274

Duct and cladding alloy  

DOEpatents

An austenitic alloy having good thermal stability and resistance to sodium corrosion at 700.degree. C. consists essentially of 35-45% nickel 7.5-14% chromium 0.8-3.2% molybdenum 0.3-1.0% silicon 0.2-1.0% manganese 0-0.1% zirconium 2.0-3.5% titanium 1.0-2.0% aluminum 0.02-0.1% carbon 0-0.01% boron and the balance iron.

Korenko, Michael K. (Rockville, MD)

1983-01-01

275

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

276

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

277

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

278

Aluminum and its light alloys  

NASA Technical Reports Server (NTRS)

Report is a summary of research work which has been done here and abroad on the constitution and mechanical properties of the various alloy systems with aluminum. The mechanical properties and compositions of commercial light alloys for casting, forging, or rolling, obtainable in this country are described.

Merica, Paul D

1920-01-01

279

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

280

Oxidation-resistant nickel alloy  

SciTech Connect

Disclosed is an oxidation resilient nickel alloy containing chromium, tungsten and molybdenum in a critical relationship that provides a combination of engineering properties including a high degree of dynamic oxidation resistance and superior strength. The alloy is especially suited for service under severe conditions, for example, as components of gas turbine engines.

Klarstrom, D.L.

1984-10-09

281

CO2 laser welding of magnesium alloys  

Microsoft Academic Search

Metallic alloys with a low mass density can be considered to be basic materials in aeronautic and automotive industry. Magnesium alloys have better properties than aluminum alloys in respect of their low density and high resistance to traction. The main problems of magnesium alloy welding are the inflammability, the crack formation and the appearance of porosity during the solidification. The

Mohammed Dhahri; Jean Eric Masse; J. F. Mathieu; Gerard Barreau; Michel L. Autric

2000-01-01

282

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

283

Microstructures in friction-stir welded dissimilar magnesium alloys and magnesium alloys to 6061-T6 aluminum alloy  

Microsoft Academic Search

Wrought Mg alloy AZ31B-H24 and semisolid-cast Mg alloy AZ91D (approximately 3% primary solid fraction) were friction-stir welded to Al alloy 6061-T6. Semisolid-cast (approximately 3% and approximately 20% primary solid fractions) Mg alloys AZ91D and AM60B were also joined using the same technique, with AZ91D on the advancing side. Numerous welds were made with the Mg alloys and the 6061-T6 Al

A. C Somasekharan; L. E Murr

2004-01-01

284

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

285

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

286

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

287

Quantum dot quantum computation in III-V type semiconductor  

NASA Astrophysics Data System (ADS)

Among recent proposals for next-generation, non-charge-based logic is the notion that a single electron can be trapped and spin of the electron can be manipulated through the application of gate potentials. In the thesis, there are two major contributions of the manipulation of electron spin. In regard to the first contribution, we present numerical simulations of such a spin in single electron devices for realistic asymmetric potentials in electrostatically confined quantum dot. Using analytical and numerical techniques we show that breaking in-plane rotational symmetry of the confining potential by applied gate voltage leads to a significant effect on the tuning of the electron g-factor. In particular, we find that anisotropy extends the tunability to larger quantum dots in the GaAs case. Although the same extension of tunability exists in the InAs quantum dot case, we find a new effect in the InAs case. The new discovery is that broken in-plane rotational symmetry due to the Rashba spin-orbit coupling in an asymmetric potential results in a significant reverse effect in the tuning of the electron g-factor. This effect can not be observed in symmetric case. The derivative of the g-factor with respect to the electric field has the opposite sign in the above two potentials. The manipulation of Berry phases of spin in nano-scale devices is a topic that has received recent attention as a promising candidate for solid state quantum computation and non-charge-based logic devices. A single electron in an electrostatically defined quantum dot located in a 2 dimensional electron gas (2DEG), for example, can be trapped and the spin can be manipulated by simply moving the center of mass of the quantum dot adiabatically along a closed loop in the 2D plane via the application of gate potentials. In relation to the second contribution, we present numerical simulations and analytical expressions for the spin-dependent electron propagator (a matrix-valued function of position) for an electron trapped in a quantum dot, while the center of mass of the quantum dot is adiabatically moved in the 2D plane in the presence of the Rashba and Dresselhaus spin-orbit interactions. We apply the Feynman disentangling technique to determine the non-abelian matrix Berry phase, we find exact analytical expression for the propagator in three cases: (a) pure Rashba coupling; (b) pure Dresselhaus coupling; and (c) a combination of equally strong Rashba and Dresselhaus couplings. For other cases of interest where the solution of the propagator can not be found analytically, we present results obtained by numerically solving the Riccati equation resulting from the disentangling procedure. We also find that the presence of both spin-orbit couplings leads to a larger spin-flip probability than what would result from either mechanism considered separately.

Prabhakar, Sanjay Kumar

288

[Update of breast cancer in Primary Care (III/V)].  

PubMed

Breast cancer is a prevalent disease with implications in all aspects of patients? life, therefore, family doctors must know this pathology in depth, in order to optimize the health care provided to these patients with the best available resources. This series of five articles on breast cancer is based on a review of the scientific literature of the last ten years. This third article will review the clinical context and the staging and prognostic factors of the disease. This summary report aims to provide a global, current and practical review about this problem, providing answers to family doctors and helping them to be by the patients for their benefit throughout their illness. PMID:24953699

Alvarez Hernández, C; Vich Pérez, P; Brusint, B; Cuadrado Rouco, C; Díaz García, N; Robles Díaz, L

2014-01-01

289

III-V 4D Transistors J. J. Gu 1)  

E-print Network

, West Lafayette, IN 47906, U.S.A. 2) Department of Chemistry and Chemical Biology, Harvard University in between each channel layer. Source/drain implantation was carried out with two-step Si implantation at 20 and liftoff process and the definition of testing pads concludes the fabrication process. All patterns were

290

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

291

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

292

Piezoelectricity and growth polarization in III-V nitrides  

NASA Astrophysics Data System (ADS)

GaN, AlN and InN form a relatively new class of semiconductors being utilized for their direct wide bandgap and polarization effects. Novel transistors using only piezoelectric doping have already surpassed the power handling capabilities of traditional silicon transistors. GaN light emitting diodes and solid state lasers, sensitive to the effects of piezoelectric polarization, are rapidly proliferating for use in lighting and next generation optical storage devices. GaN and AIN sensors and MEMS devices using the strong piezoelectric coupling coefficients of these materials are slowly being introduced into communications and chemical sensing applications. Despite the importance of the piezoelectric effect in each of these devices, relatively little is known of the magnitude of the effect in GaN and AIN as measured experimentally. The present work seeks to develop an experimental method of measuring the piezoelectric effect in thin films of GaN and AIN. Using a stress pulse induced by the single shot of a Nd:YAG laser, substrates of polar GaAs and ZnO are subject to short duration loading which generates piezoelectric dipoles. The orientation and magnitude of these dipoles induces current flow in an external circuit which is measured as a function time. By comparing the magnitude of the current generated in this circuit and the applied stress, it is shown that the axial piezoelectric constant, e 33, can be determined. Extending the measurement technique to thin films of GaN and AIN on sapphire and silicon, we have observed the magnitude and orientation of the piezoelectric dipoles in these materials. A value of 0.45 C/m2 for e33 in GaN was determined. This work motivated a closer investigation of the polarity of GaN during crystal growth. The addition of Mg during MOCVD was found to cause a uniform inversion of the growth axis producing nitrogen terminated surfaces under certain growth conditions. Chemical-mechanical polishing of these surfaces with colloidal silica was found to produce smooth, damage free surfaces suitable for regrowth or additional processing. Growth of GaN and InGaN along the nitrogen polar direction was characterized by AFM, TEM, SIMS, x-ray, PL, and Hall measurements revealing surprisingly high quality material suitable for optical and electrical devices.

Tavernier, Philip Ross

293

Chemical beam epitaxy growth of III–V semiconductor nanowires  

SciTech Connect

Indium- Arsenide (InAs) nanowires were grown in a high vacuum chemical beam epitaxy (CBE) unit on InAs(111) wafers substrates at 425–454°C. Two types of nanogold were used as orientation catalyst, 40nm and 80nm. The measurements were performed using scanning electron microscopy showed that uniform nanowires. The nanowires orient vertically in the InAs nanowire scanning electron microscopy of an array 80nm diameter InAs nanowire with length is in the range 0.5–1 ?m and of an array 40nm diameter with length is in the range 0.3–0.7?m. The nanowire length with growth time shows that the linear increase of nanowires start to grow as soon as TMIn is available. The growth rate with temperature was studied.

Mohummed Noori, Farah T. [University of Baghdad , College of science, Physics department , Jadiriya ,Baghdad (Iraq)

2013-12-16

294

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

2014-01-01

295

Random stacking sequences in III-V nanowires are correlated  

NASA Astrophysics Data System (ADS)

We investigate crystal plane stacking in InP nanowires with marked wurtzite/zinc-blende phase mixing. We measure the length distributions of hexagonal and cubic segments and the frequencies of all short sequences of monolayers. This reveals spatial correlations extending over several monolayers, which we describe in terms of conditional probabilities. Results can be modeled by considering the energy barriers for nucleation on top of all types of preexisting stacking. A quantitative agreement is obtained only if the interaction with the underlying layers involves the edge energy of the nucleus.

Priante, Giacomo; Harmand, Jean-Christophe; Patriarche, Gilles; Glas, Frank

2014-06-01

296

The stochastic model for ternary and quaternary alloys: Application of the Bernoulli relation to the phonon spectra of mixed crystals  

SciTech Connect

To understand and interpret the experimental data on the phonon spectra of the solid solutions, it is necessary to describe mathematically the non-regular distribution of atoms in their lattices. It appears that such description is possible in case of the strongly stochastically homogenous distribution which requires a great number of atoms and very carefully mixed alloys. These conditions are generally fulfilled in case of high quality homogenous semiconductor solid solutions of the III–V and II–VI semiconductor compounds. In this case, we can use the Bernoulli relation describing probability of the occurrence of one n equivalent event which can be applied, to the probability of finding one from n configurations in the solid solution lattice. The results described in this paper for ternary HgCdTe and GaAsP as well as quaternary ZnCdHgTe can provide an affirmative answer to the question: whether stochastic geometry, e.g., the Bernoulli relation, is enough to describe the observed phonon spectra.

Marchewka, M., E-mail: marmi@ur.edu.pl; Wo?ny, M.; Polit, J.; Sheregii, E. M. [Faculty of Mathematics and Natural Sciences, Centre for Microelectronics and Nanotechnology, University of Rzeszów, Pigonia 1, 35-959 Rzeszów (Poland); Kisiel, A. [Institute of Physics, Jagiellonian University, Reymonta 4, Kraków 30-059 (Poland); Robouch, B. V.; Marcelli, A. [INFN-Laboratori Nazionali di Frascati, Via E. Fermi 40, I-00044 Frascati (Italy)

2014-03-21

297

New Amorphous Silicon Alloy Systems  

NASA Astrophysics Data System (ADS)

The properties of hydrogenated amorphous silicon (a-Si:H) have been modified by alloying with Al, Ga and S respectively. The Al and Ga alloys are in effect quaternary alloys as they were fabricated in a carbon-rich discharge. The alloys were prepared by the plasma assisted chemical vapor deposition (PACVD) method. This method has several advantages, the major one being the relatively low defect densities of the resulting materials. The PACVD system used to grow the alloy films was designed and constructed in the laboratory. It was first tested with known (a-Si:H and a-Si:As:H) materials. Thus, it was established that device quality alloy films could be grown with the home-made PACVD setup. The chemical composition of the alloys was characterized by secondary ion mass spectrometry (SIMS), and electron probe microanalysis (EPMA). The homogeneous nature of hydrogen distribution in the alloys was established by SIMS depth profile analysis. A quantitative analysis of the bulk elemental content was carried out by EPMA. The analysis indicated that the alloying element was incorporated in the films more efficiently at low input gas concentrations than at the higher concentrations. A topological model was proposed to explain the observed behavior. The optical energy gap of the alloys could be varied in the 0.90 to 1.92 eV range. The Al and Ga alloys were low band gap materials, whereas alloying with S had the effect of widening the energy gap. It was observed that although the Si-Al and Si-Ga alloys contained significant amounts of C and H, the magnitude of the energy gap was determined by the metallic component. The various trends in optical properties could be related to the binding characteristics of the respective alloy systems. A quantitative explanation of the results was provided by White's tight binding model. The dark conductivity-temperature dependence of the alloys was examined. A linear dependence was observed for the Al and Ga systems. Electronic conduction in the S-alloys appeared to proceed by a two step mechanism. The thermal activation energies for the high Al content and S-alloys were close to half the band gap value. The photoresponse of the films was determined from the light to dark conductivity ratio. The best photoresponse (sigma_ {L}/sigma_{D} = 4 times 10^2) was obtained for the Si-S alloys showing that they are promising electrode materials for solar cell application. A single unit photovoltaic electrolyzer was constructed by combining a-Si:H solar cells with an electrolysis cell. Several different configurations ((PIN), (PIN)^2 , and (PIN)^3) of the solar cells were tested. Both electric power and chemical energy (H_2) could be simultaneously drawn from the electrolyzer.

Kapur, Mridula N.

1990-01-01

298

Alloys of titanium with refaractory elements  

Microsoft Academic Search

1.We investigated the mechanical properties, structure, and phase composition of binary alloys with up to 30% Mo, V, and Cr, and up to 60% Nb, and ternary and more complex alloys with up to 40% refractory metals Mo, Nb, V, and Cr.2.Alloys with a high concentration of alloying elements (30–40%) have a lower plasticity than a and a+ß alloys.3.Most of

O. P. Solonina; N. M. Ulyakova

1973-01-01

299

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

300

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

301

Some thoughts on alloy design  

SciTech Connect

This paper discusses some of the problems associated with attempts to use first principles in alloy design. We briefly summarize the role of microstructure on the properties of high temperature alloys and illustrate some of the microstructural features of conventional superalloys. We also describe how theory and experiment are converging toward some predictive capabilities for relating microstructure and composition using Ni-Al-Mo-X alloys as an example. Finally, this paper suggests that progress is being made in combining the results of condensed matter theory and experimental research.

Martin, P.L.; Williams, J.C.

1984-01-01

302

Modeling dissolution in aluminum alloys  

NASA Astrophysics Data System (ADS)

Aluminum and its alloys are used in many aspects of modern life, from soda cans and household foil to the automobiles and aircraft in which we travel. Aluminum alloy systems are characterized by good workability that enables these alloys to be economically rolled, extruded, or forged into useful shapes. Mechanical properties such as strength are altered significantly with cold working, annealing, precipitation-hardening, and/or heat-treatments. Heat-treatable aluminum alloys contain one or more soluble constituents such as copper, lithium, magnesium, silicon and zinc that individually, or with other elements, can form phases that strengthen the alloy. Microstructure development is highly dependent on all of the processing steps the alloy experiences. Ultimately, the macroscopic properties of the alloy depend strongly on the microstructure. Therefore, a quantitative understanding of the microstructural changes that occur during thermal and mechanical processing is fundamental to predicting alloy properties. In particular, the microstructure becomes more homogeneous and secondary phases are dissolved during thermal treatments. Robust physical models for the kinetics of particle dissolution are necessary to predict the most efficient thermal treatment. A general dissolution model for multi-component alloys has been developed using the front-tracking method to study the dissolution of precipitates in an aluminum alloy matrix. This technique is applicable to any alloy system, provided thermodynamic and diffusion data are available. Treatment of the precipitate interface is explored using two techniques: the immersed-boundary method and a new technique, termed here the "sharp-interface" method. The sharp-interface technique is based on a variation of the ghost fluid method and eliminates the need for corrective source terms in the characteristic equations. In addition, the sharp-interface method is shown to predict the dissolution behavior of precipitates in aluminum alloys when compared with published experimental results. The influence of inter-particle spacing is examined and shown to have a significant effect on dissolution kinetics. Finally, the impact of multiple particles of various sizes interacting in an aluminum matrix is investigated. It is shown that smaller particles dissolve faster, as expected, but influence the dissolution of larger particles through soft-impingement, even after the smaller particles have disappeared.

Durbin, Tracie Lee

2005-07-01

303

Shape memory alloy cables  

NASA Astrophysics Data System (ADS)

Conventional structural cables (or wire ropes) are composed of steel wires helically wound into strands, which, in turn, are wound around a core. Cables made from shape memory alloy (SMA) wires are a new structural element with promising properties for a broad range of new applications. Among the many potential advantages of this form are increased bending flexibility for spooling/packaging, better fatigue performance, energy absorption and damping, reduced thermal lag, redundancy, and signicant design flexibility. Currently there are no known studies of SMA cables in the literature, so exploratory thermo-mechanical experiments were performed on two commercially available cable designs as part of an ongoing research program to systematically characterize their thermomechanical behavior and demonstrate their potential utility as adaptive or resilient tension elements.

Reedlunn, Benjamin; Shaw, John A.

2008-03-01

304

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

305

Electrodeposition on magnesium alloy diecasting.  

E-print Network

??Magnesium alloy diecasting AZ91CC, AZ61CC', AZ91HC and AZ71HC were electroplated using different pretreatment sequences which incorporated conventional zincate immersion processes. Satisfactory peel adhesion in excess… (more)

Wan, Katy Y.

1986-01-01

306

[MRO] Oligocrystalline Shape Memory Alloys  

E-print Network

Copper-based shape memory alloys (SMAs) exhibit excellent shape memory properties in single crystalline form. However, when they are polycrystalline, their shape memory properties are severely compromised by brittle fracture ...

Chen, Ying

307

Smart interfacial bonding alloys  

SciTech Connect

The goal of this LDRD was to explore the use of the newly discovered strain-stabilized 2-D interfacial alloys as smart interface bonding alloys (SIBA). These materials will be used as templates for the heteroepitaxial growth of metallic thin films. SIBA are formed by two metallic components which mix at an interface to relieve strain and prevent dislocations from forming in subsequent thin film growth. The composition of the SIBA is determined locally by the amount of strain, and therefore can react smartly to areas of the highest strain to relieve dislocations. In this way, SIBA can be used to tailor the dislocation structure of thin films. This project included growth, characterization and modeling of films grown using SIBA templates. Characterization will include atomic imaging of the dislocations structure, measurement of the mechanical properties of the film using interface force microscopy (IFM) and the nanoindenter, and measurement of the electronic structure of the SIBA with synchrotron photoemission. Resistance of films to sulfidation and oxidation will also be examined. The Paragon parallel processing computer will be used to calculate the structure of the SIBA and thin films in order to develop ability to predict and tailor SIBA and thin film behavior. This work will lead to the possible development of a new class of thin film materials with properties tailored by varying the composition of the SIBA, serving as a buffer layer to relieve the strain between the substrate and the thin film. Such films will have improved mechanical and corrosion resistance allowing application as protective barriers for weapons applications. They will also exhibit enhanced electrical conductivity and reduced electromigration making them particularly suitable for application as interconnects and other electronic needs.

R. Q. Hwang; J. C. Hamilton; J. E. Houston

1999-04-01

308

Innovations in cast magnesium alloys  

Microsoft Academic Search

This article examines questions related to aspects of the production of castings of magnesium alloys in molds made by volumetric\\u000a stamping without the use of the corresponding tooling. Information is presented on features of the gating-feeding systems\\u000a used to obtain magnesium-alloy castings in molds made by volumetric stamping. Also examined are features of the effect of\\u000a small additions of calcium

V. D. Belov; A. V. Koltygin; N. A. Belov; I. V. Plisetskaya

2010-01-01

309

Casting Alloys: Side-Effects  

Microsoft Academic Search

Side-effects from dental materials are a minor problem, but should be recognized. In recent questionnaire surveys about side-effects, the incidence was estimated to be 1:300 in periodontics and 1:2600 in pedodontics. None of these reactions was related to dental casting alloys. In prosthodontics, the incidence was calculated to be about 1:400, and about 27% were related to base-metal alloys forremovable

Arne Hensten-Pettersen

1992-01-01

310

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

311

Castable hot corrosion resistant alloy  

NASA Technical Reports Server (NTRS)

Some 10 wt percent nickel is added to an Fe-base alloy which has a ferrite microstructure to improve the high temperature castability and crack resistance while about 0.2 wt percent zirconium is added for improved high temperatur cyclic oxidation and corrosion resistance. The basic material is a high temperature FeCrAl heater alloy, and the addition provides a material suitable for burner rig nozzles.

Barrett, Charles A. (inventor); Holt, William H. (inventor)

1988-01-01

312

Magnetic moments in heusler alloys  

Microsoft Academic Search

The Heusler alloys are a series of local moment ferromagnets of composition X2MnY, with a magnetization of ~4muB per Mn atom. Magnetic measurements on the alloy series Ni2MnxT1-xSn, where T is Ti, V or Cr, indicate that the T site moment changes from -muB (for Ti), through zero (for V), to +muB (for CR). A simple physical interpretation is proposed

C. C. M. Campbell

1976-01-01

313

Ni{sub 3}Al aluminide alloys  

SciTech Connect

This paper provides a brief review of the recent progress in research and development of Ni{sub 3}Al and its alloys. Emphasis has been placed on understanding low ductility and brittle fracture of Ni{sub 3}Al alloys at ambient and elevated temperatures. Recent studies have resulted in identifying both intrinsic and extrinsic factors governing the fracture behavior of Ni{sub 3}Al alloys. Parallel efforts on alloy design using physical metallurgy principles have led to properties for structural use. Industrial interest in these alloys is high, and examples of industrial involvement in processing and utilization of these alloys are briefly mentioned.

Liu, C.T.

1993-10-01

314

Alloying element diffusion in alloy 800 H (UNS N08810) and alloy 617 (UNS N06617)  

SciTech Connect

Samples of alloy 800 H (LJNS N08810) and alloy 617 (UNS N06617) were oxidized in a simulated process gas atmosphere. The principal elements of the gaseous environment were 50% H{sub 2}O, 35% H{sub 2} and 5% of CO{sub 2}, CO, and CH{sub 4}, respectively. The experiments were carried out at temperatures from 850 C to 950 C for exposures ranging from 600 to 5,000 hours. After the exposure, the alloy surfaces showed compact oxide layers, which resulted in a depleted zone of oxidizing elements in the substrate layer. Using Electron Probe Microanalysis (EPMA), concentration profiles and the extension of the depleted zone were measured. Calculated theoretical profiles were then fitted to the EPMA-measured profiles, using Fick`s second law of diffusion and resolved by a finite difference method and diffusion coefficients as fitting parameters. The diffusion coefficients for chromium may be represented as D = Do exp.(-Q/RT) with the values Do = 11.4 cm{sup 2}/s and Q = 289 kJ/mol for alloy 800 H and Do = 2.1 cm{sup 2}/s and Q = 280 kJ/ mol for alloy 617. The value of the resulting activation energy Q for diffusion in the investigated alloys is similar to that reported in the literature for f.c.c structures.

Maldonado, L.; Diaz, L. [Unidad Merida (Mexico). Centro de Investigacion y de Estudios Avanzados; Gruebmaier, H.; Naoumidis, A.; Nickel, H. [Research Centre Juelich GmbH (Germany). Inst. for Materials in Energy Systems

1996-10-01

315

Surface modification of 5083 Al alloy by electrical discharge alloying processing with a 75 mass% Si-Fe alloy electrode  

NASA Astrophysics Data System (ADS)

This study experimentally investigates the surface modification of 5083 Al alloy by the electrical discharge alloying (EDA) process with a Si-Fe alloy as an electrode. Samples were analyzed by transmission electron microscopy (TEM), scanning electron microscopy (SEM), micro-hardness and corrosion resistance tests. The micro-hardness of EDA alloyed layer was evidently higher than that of the base metal (5083 Al alloy). The TEM results show that the matrix of the alloyed layer has an amorphous-like structure; the matrix contains fine needle-like Si particles, block-like Si particles and nano-size Al4.5FeSi and Al13Fe4 particles. The TEM results support experimental results for the high hardness of the alloyed layer. Moreover, the EDA alloyed layer with composite microstructures has good corrosion resistance in NaCl aqueous solution.

Stambekova, Kuralay; Lin, Hung-Mao; Uan, Jun-Yen

2012-03-01

316

Characterizing alloy additions to high nitrogen steels  

SciTech Connect

Numerous articles of individual high nitrogen stainless steel compositions or alloys with near identical alloy compositions have been published characterizing the properties the alloy or the improvement which an individual element contributes to the base alloy's properties. In this study a series of high nitrogen steels alloys were prepared with the intent of characterizing the advantages and limitations of different alloy chemistry on the base alloy's material properties such as: microstructure, mechanical properties, environmental interactions (corrosion and oxidation), and wear. A base composition of Fe-15Cr-15 Mn was chosen. Alloys of similar basic compositions are austenitic and often used as a starting composition as a substitute or replacements for Fe-Cr-Ni stainless steel alloys. Mn is less expensive than Ni, is a strong austenizer, enhances nitrogen solubility, and has no allergenic effects. To this base alloy composition additions of C, N, Si, Mo, and Nb was added. Nitrogen (and carbon) alloys as interstitials and have been shown to enhance strength and reduce corrosion. Niobium (or similar elements) is often added to produce intergranular carbide precipitates that further enhance strength. Molybdenum and silicon are added to improve corrosion-oxidation properties. This study was designed to evaluate the action and interaction of these different alloys and suggest what alloys compositions are best used under different engineering requirements. The results of the experimental alloys are compared with that of two experimental higher-nitrogen commercial alloys steels with further alloy addition of Ni and Cu were also studied. Alloy evaluation included: (1) microstructure: optical, SEM, and X-ray diffraction, (2) mechanical properties: yield, tensile, elongation, hardness (room temperature and hot), and energy to failure, (3) oxidation and corrosion, and (4) abrasive wear: scratch, pin-on-drum, and pin-on-disk.

Rawers, James C.; Tylczak, Joseph H.; Blankenship, D.; Bullard, Sophie J.

2003-01-01

317

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

318

New Theoretical Technique for Alloy Design  

NASA Technical Reports Server (NTRS)

During the last 2 years, there has been a breakthrough in alloy design at the NASA Lewis Research Center. A new semi-empirical theoretical technique for alloys, the BFS Theory (Bozzolo, Ferrante, and Smith), has been used to design alloys on a computer. BFS was used, along with Monte Carlo techniques, to predict the phases of ternary alloys of NiAl with Ti or Cr additions. High concentrations of each additive were used to demonstrate the resulting structures.

Ferrante, John

2005-01-01

319

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

320

Fatigue behavior of titanium alloys  

SciTech Connect

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 and {alpha}-alloys, {alpha}/{beta}- and {beta}-alloys to the gamma titanium aluminides. The effects of processing/heat treatment/microstructure on the fatigue properties were discussed, and models proposed to correlate the microstructures to the observed fatigue performance. Test environments reported on included hard vacuum (and the effect of vacuum level), vacuums with partial pressures of miscellaneous gases, lab air and aqueous media. A session was devoted to the effects of environment and fatigue enhancement via surface treatments using techniques such as shot peening and roller burnishing. The effects of dwell on both S-N and crack growth rate behavior were covered. It was a very comprehensive symposium with presentations from academia, government laboratories and industry, with industrial participants ranging from the petroleum industry to medical and aerospace interests. This book has been separated into four sections, representing the technology areas covered in various sessions, namely Mechanisms of Fatigue crack Initiation and Propagation of Conventional Alloys, Fatigue in Intermetallics, Environmental and Surface Aspects of Fatigue, and Application, Life Prediction and Design. Separate abstracts were prepared for most papers in this volume.

Boyer, R.R.; Eylon, D.; Luetjering, G. [eds.

1999-07-01

321

Oxidation of low cobalt alloys  

NASA Technical Reports Server (NTRS)

Four high temperature alloys: U-700, Mar M-247, Waspaloy and PM/HIP U-700 were modified with various cobalt levels ranging from 0 percent to their nominal commercial levels. The alloys were then tested in cyclic oxidation in static air at temperatures ranging from 1000 to 1150 C at times from 500 to 100 1 hour cycles. Specific weight change with time and X-ray diffraction analyses of the oxidized samples were used to evaluate the alloys. The alloys tend to be either Al2O3/aluminate spinel or Cr2O3/chromite spinel formers depending on the Cr/Al ratio in the alloy. Waspaloy with a ratio of 15:1 is a strong Cr2O3 former while this U-700 with a ratio of 3.33:1 tends to form mostly Cr2O3 while Mar M-247 with a ratio of 1.53:1 is a strong Al2O3 former. The best cyclic oxidation resistance is associated with the Al2O3 formers. The cobalt levels appear to have little effect on the oxidation resistance of the Al2O3/aluminate spinel formers while any tendency to form Cr2O3 is accelerated with increased cobalt levels and leads to increased oxidation attack.

Barrett, C. A.

1982-01-01

322

Effect of Al-Ti-B on Magnesium Alloy Micro-Alloyed with Ca  

Microsoft Academic Search

Effect of Al-Ti-B master alloy on the microstructure and mechanical properties was investigated in AZ31 magnesium alloys micro-alloyed with Ca. During the casting process, electromagnetic field was also introduced. The results suggest that the micro addition of Ca to magnesium alloy retards the oxidation rate during melting process, improves casting qualities of magnesium alloy ingots. The grain size of AZ31

Canfeng Fang; Guohong Qi; Xingguo Zhang; Hai Hao; Junze Jin

2009-01-01

323

k-resolved alloy bowing in pseudobinary InxGa1-xAs alloys  

Microsoft Academic Search

k-resolved alloy-bowing data for InxGa1-xAs alloys have been taken and used to examine the validity of different alloy formalisms. Although the molecular coherent-potential approximation is considered to be the most complete alloy formalism for zinc-blende pseudobinary alloys, it is not in agreement with the experimental k-resolved data. In contrast, these k-resolved data are in approximate agreement with the coherent-potential-approximation prediction.

J. Hwang; P. Pianetta; Y.-C. Pao; C. K. Shih; Z.-X. Shen; P. A. P. Lindberg; R. Chow

1988-01-01

324

Explosive depassivation of amorphous alloys during corrosion  

SciTech Connect

It has been shown that, during active and passive corrosion, Fe{sub 80-x}Cr{sub x}P{sub 13}C{sub 7} amorphous alloys can be transformed into a crystalline modification. Crystallization of alloys is a result of selective dissolution and can lead to explosive depassivation upon long-term exposure of alloys in HCl solutions.

Vasil`ev, V.Yu.; Mikaelyan, A.S.; Isirikyan, A.A. [Moscow Institute of Steel and Alloys, Moscow (Russian Federation)

1994-09-01

325

Cytotoxicity of Titanium and Titanium Alloying Elements  

Microsoft Academic Search

It is commonly accepted that titanium and the titanium alloying elements of tantalum, niobium, zirconium, molybdenum, tin, and silicon are biocompatible. However, our research in the development of new titanium alloys for biomedical applications indicated that some titanium alloys containing molybdenum, niobium, and silicon produced by powder metallurgy show a certain degree of cytotoxicity. We hypothesized that the cytotoxicity is

Y. Li; C. Wong; J. Xiong; P. Hodgson; C. Wen

2010-01-01

326

SUPERCONDUCTIVITY OF TECHNETIUM ALLOYS AND COMPOUNDS  

Microsoft Academic Search

The superconducting transition temperatures of Mo- Tc alloys are ; reported. Critical field measurements of a 50 atomic per cent alloy indicate ; that it might be a promising material for superconducting magnets. The ; similarity of Tc and Re with respect to alloy and intermetallic compound ; formation is noted. The superconducting transition temperatures of the compounds ; ZrTcâ

V. B. Compton; E. Corenzwit; J. P. Maita; B. T. Matthias; F. J. Morin

1961-01-01

327

Uranium-fissium alloys containing technetium  

Microsoft Academic Search

A recent study (Report ANL-6495) was completed in which the phase ; relationships and decomposition kinetics of alloys with the complete fissium ; analysis were measured and compared with U-Fs alloys without technetium. The ; presence of the Tc addition appeared to have a relatively minor influence on the ; U-Fs alloys. (W.D.M.);

R. Bohl

1962-01-01

328

Fundamental aspects of the corrosion of alloys  

Microsoft Academic Search

Phenomenological equations are given for the steady state dissolution of alloys and their composition at the surface. The slow component with the smallest rate constant essentially determines the steady state dissolution rate and is enriched in the alloy surface. The phenomenological equations are compared to experimental results both for active and passive alloys. In ideal cases, phenomenological rate constants are

K. E. Heusler

1997-01-01

329

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

330

Alloy 718 for Oilfield Applications  

NASA Astrophysics Data System (ADS)

Alloy 718 (UNS N07718) was developed for use in aircraft gas turbine engines, but its unique combination of room-temperature strength and aqueous corrosion resistance made it a candidate for oilfield fasteners, valves, drill tools, and completion equipment. As well environments became more severe, stress corrosion and hydrogen embrittlement failures in production equipment drove the evolution of the composition and microstructure that distinguish today's oilfield-grade 718 from aerospace grades. This paper reviews the development of the grade and its applications and describes some of its unique characteristics, testing, and manufacturing methods as well as newer alloys designed for high-pressure high-temperature (HPHT) conditions.

deBarbadillo, John J.; Mannan, Sarwan K.

2012-02-01

331

Nd:YAG laser welding aluminum alloys  

SciTech Connect

Autogenous Nd:YAG laser welding wrought 4047, 1100, 3003, 2219, 5052, 5086, 5456, and 6061 and cast A356 aluminum alloys to cast A356 aluminum alloy in restrained annular weld joints was investigated. The welds were 12.7 mm (0.375 in.) and 9.5 mm (0.375 in.) diameter with approximately 0.30 mm (0.012 in.) penetration. This investigation determined 4047 aluminum alloy to be the optimum alloy for autogenous Nd:YAG laser welding to cast A356 aluminum alloy. This report describes the investigation and its results.

Jimenez, E. Jr.

1992-02-01

332

Liquid metal ion source and alloy  

DOEpatents

A liquid metal ion source and alloy, wherein the species to be emitted from the ion source is contained in a congruently vaporizing alloy. In one embodiment, the liquid metal ion source acts as a source of arsenic, and in a source alloy the arsenic is combined with palladium, preferably in a liquid alloy having a range of compositions from about 24 to about 33 atomic percent arsenic. Such an alloy may be readily prepared by a combustion synthesis technique. Liquid metal ion sources thus prepared produce arsenic ions for implantation, have long lifetimes, and are highly stable in operation.

Clark, Jr., William M. (Thousand Oaks, CA); Utlaut, Mark W. (Saugus, CA); Behrens, Robert G. (Los Alamos, NM); Szklarz, Eugene G. (Los Alamos, NM); Storms, Edmund K. (Los Alamos, NM); Santandrea, Robert P. (Santa Fe, NM); Swanson, Lynwood W. (McMinnville, OR)

1988-10-04

333

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

334

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

335

Influence of Chemical Composition of Mg Alloys on Surface Alloying by Diffusion Coating  

NASA Astrophysics Data System (ADS)

A recently developed technique of surface alloying by diffusion-coating has been used to produce coatings on Mg alloys with various Al and Zn contents. The experimental results show that both Al and Zn solutes in the alloy promote the diffusion of alloying elements through grain refinement of the substrate alloys and through reduction of diffusion active energy because of the reduction of melting temperature of the alloys. Therefore, the efficiency of surface alloying increases by diffusion coating. Thick, dense, uniform, and continuous layers of intermetallic compounds, which consist of a ?-phase layer and a ?-phase layer, can be produced on the surface of various Mg alloys. The intermetallic compound layers not only have microhardness values that are 4 to 6 times higher than the substrate but also provide effective protection of the Mg alloys from corrosion in 5 pct NaCl solution at room temperature.

Hirmke, J.; Zhang, M.-X.; St John, D. H.

2012-05-01

336

Alloy softening in binary iron solid solutions  

NASA Technical Reports Server (NTRS)

An experimental study was conducted to determine whether alloy softening in Fe alloys is dependent on electron concentration and to provide a direct comparison of alloy softening and hardening in several binary Fe alloy systems having the same processing history. Alloy additions to Fe included the elements in the Periods 4-6 and the Groups IV-VIII with the exception of technetium. A total of 19 alloy systems was investigated, and hardness testing was the primary means of evaluation. Testing was carried out at four temperatures over a homologous temperature range of 0.043-0.227 times the absolute melting temperature of unalloyed Fe. Major conclusions are that the atomic radius ratio of solute-to-Fe is the key factor in controlling low-temperature hardness of the binary Fe alloys and that alloy softening rates at 77 K and alloy hardening rates at 411 K are correlated with this atomic radius ratio for 15 of the binary alloy systems. Mechanisms of alloy softening and hardening are proposed.

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

1976-01-01

337

Development of strength in solidifying aluminium alloys  

SciTech Connect

Quantitative measurements of the strength development in the mushy-zone during solidification have been obtained in two commercial Al-Si alloys, AlSi7Mg and AlSi11Mg, an AlCu4 alloy and an AlMg5 alloy with a vane method. The results show that the material does not have any strength prior to dendrite coherency, confirming that the dendrites are free-floating and independent. Grain refining the AlSi7Mg and AlCu4 alloy postpones strength development, and strength increases slowly in the grain refined AlCu4 alloy. Adding Sr to the AlSi7Mg alloy postpones dendrite coherency and strength develops more slowly. Fading is observed to change the strength back towards that of the unmodified alloy with time. Adding 1% Si to the AlMg5 alloy postpones dendrite coherency, but the strength increases rapidly and makes the strength of the AlMg5Si1 alloy converge towards that of the AlMg5 alloy at increasing solid fractions. Strength develops very slowly in the AlSi11Mg alloy. The results are shown to be related to the size and morphology of the growing dendrites.

Dahle, A.K.; Arnberg, L. [Norwegian Univ. of Science and Technology, Trondheim (Norway). Dept. of Metallurgy] [Norwegian Univ. of Science and Technology, Trondheim (Norway). Dept. of Metallurgy

1997-02-01

338

Aqueous recovery of actinides from aluminum alloys  

SciTech Connect

Early in the 1980's, a joint Rocky Flats/Savannah River program was established to recover actinides from scraps and residues generated during Rocky Flats purification operations. The initial program involved pyrochemical treatment of Molten Salt Extraction (MSE) chloride salts and Electrorefining (ER) anode heel metal to form aluminum alloys suitable for aqueous processing at Savannah River. Recently Rocky Flats has expressed interest in expanding the aluminum alloy program to include treatment of chloride salt residues from a modified Molten Salt Extraction process and from the Electrorefining purification operations. Samples of the current aluminum alloy buttons were prepared at Rocky Flats and sent to Savannah River Laboratory for flowsheet development and characterization of the alloys. A summary of the scrub alloy-anode heel alloy program will be presented along with recent results from aqueous dissolution studies of the new aluminum alloys. 2 figs., 4 tabs.

Gray, J.H.; Chostner, D.F.; Gray, L.W.

1989-01-01

339

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

340

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

341

Biocompatibility of Dental Casting Alloys  

Microsoft Academic Search

Most cast dental restorations are made from alloys or commercially pure titanium (cpTi). Many orthodontic appliances are also fabricated from metallic materials. It has been documented in vitro and in vivo that metallic dental devices release metal ions, mainly due to corrosion. Those metallic components may be locally and systemically distributed and could play a role in the etiology of

Werner Geurtsen

2002-01-01

342

Recent developments in light alloys  

NASA Technical Reports Server (NTRS)

This report is intended to cover the progress that has been made in both the manufacture and utility of light alloys in the United States since the first part of 1919. Duralumin is extensively discussed both as to manufacture and durability.

Woodward, R W

1920-01-01

343

Introduction to hydrogen in alloys  

SciTech Connect

Substitutional alloys, both those that form hydrides and those that do not, are discussed, but with more emphasis on the former than the latter. This overview includes the following closely related subjects: (1) the significant effects of substitutional solutes on the pressure-composition-temperature (PCT) equilibria of metal-hydrogen systems, (2) the changes in thermodynamic properties resulting from differences in atom size and from modifications of electronic structure, (3) attractive and repulsive interactions between H and solute atoms and the effects of such interactions on the pressure dependent solubility for H, (4) H trapping in alloys of Group V metals and its effect on the terminal solubility for H (TSH), (5) some other mechanisms invoked to explain the enhancement (due to alloying) of the (TSH) in Group V metals, and (6) H-impurity complexes in alloys of the metals Ni, Co, and Fe. Some results showing that an enhanced TSH may ameliorate the resistance of a metal to hydrogen embrittlement are presented.

Westlake, D.G.

1980-01-01

344

New horizons in semimetal alloys  

Microsoft Academic Search

A small number of free carriers, a small cyclotron mass, a very high mobility at superconducting temperatures¿these are among the properties that make bismuth, along with its alloys, the subject of intensive research efforts. The ``cleanness'' of these materials, for example, makes them ideal for new kinds of plasma experiments in solids. Results so far could be described as intriguing

Leo Esaki

1966-01-01

345

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

346

Scanning Probe Alloying Nanolithography (SPAN)  

E-print Network

probe alloying nanolithography STM Scanning tunneling microscope TEM Transmission electron microscope vii TABLE OF CONTENTS ABSTRACT ii ACKNOWLEDEGMENTS v NOMENCLATURE vi TABLE OF CONTENTS vii LIST OF IGURES... Figure 1.1 Steps of optical lithography process .................................................. 3 Figure 1.2 Comparison of AFM with other measurements ................................. 8 Figure 1.3 The conception of STM...

Lee, Hyungoo

2010-07-14

347

Study of the Local Structure of II-Vi Ternary Alloys by Extended X-Ray Absorption Fine Structure  

NASA Astrophysics Data System (ADS)

Bondlengths, Debye-Waller factors, and site occupancy in the diluted magnetic semiconductors Zn_ {rm 1 - x}Mn_{ rm x}Se and Hg_{ rm 1 - x}Mn_{rm x}Te, and the narrow-gap semiconductor Hg _{rm 1 - x}Cd _{rm x}Te have been measured using extended x-ray absorption fine structure (EXAFS). The nearest-neighbor bond lengths in all of these alloys are found to be constant as a function of alloy composition within the experimental uncertainty of 0.01A. Because the average cation-cation distance changes with Mn composition, these results necessarily imply distortion of the tetrahedral bond angles. In the case of Zn_{rm 1 - x}Mn_{rm x} Se, the anion sublattice is shown to suffer the largest distortion, but the cation sublattice also exhibits some relaxation. The repercussions of these results are discussed, in terms of the amount of cation and anion sublattice distortion at low temperature and its connection to the superexchange mechanism occurring between the Mn ^{+2} ions and mediated by the intervening anion in Zn_{rm 1 - x}Mn_{rm x} Se. From the NN bond length relaxation results shown in this study and those reported elsewhere for the III -V-based and II-VI-based ternary compounds and DMS alloys, it appears that substitution of Mn^{+2 } ions into II-VI-based compounds causes greater local distortion, in general, than otherwise observed when group II cations are substituted for one another. We believe that the tetrahedral bond weakening in DMS is due to MN 3d-orbital (t_2) and anion p-orbital hybridization in DMS, leaving fewer p-orbitals available for tetrahedral bonding. This leads to the weakening of the bond force constants alpha, beta, as well as the bond becoming more ionic as Mn^{+2} is substituted into the II-VI-based compounds. Finally, the experimentally extended electron energy loss fine structure (EXELFS) technique, with modulations in the differential inelastic electron scattering cross -section above an absorption core edge, has been used in recent years to study the local structure of condensed matter systems. Basically, the EXELFS phenomenology is the same as that for EXAFS, because the excited electron undergoes the same interference process when the experimental probe is either an electron or a photon. It has been demonstrated to be a complementary tool to EXAFS for obtaining accurate values for the surface structural parameters of materials.

Pong, Way-Faung

348

Structural Properties of Mismatched Alloys  

NASA Astrophysics Data System (ADS)

The problem of understanding the local structure of disordered alloys has been around for a long time. In this thesis, I look more specifically at the effect of size-mismatch disorder in binary alloys under many forms: metallic and semiconductor alloys, bulk and surfaces, two and three dimensional systems. I have studied the limitations of a central-force model (CFM) and an embedded-atom potential (EAM) in describing the local structure of binary metallic alloys composed of Ag, Au, Cu, Ni, Pd, or Pt. Although an analytical model developed using the CFM explains qualitatively well the experimental and numerical results, in many cases, it is important to add electronic density effects through a more sophisticated potential like EAM in order to agree quantitatively with experiment. I have also looked at amorphous and crystalline silicon-germanium alloys. It turns out that the effect of size-mismatch is the same on a crystalline and an amorphous lattice. In the latter case, it can be seen as a perturbation of the much larger disorder due to the amorphisation process. However, the analytical predictions differ, for both the crystalline and amorphous alloys, from the experimental results. If one is to believe the data, there is only one possible explanation for this inconsistency: large amounts of hydrogen are present in the samples used for the measurements. Since the data analysis of EXAFS results is not always straightforward, I have proposed some experiments that could shed light on this problem. One of these experiments would be to look at the (111) surface of a Si-Ge alloy with a scanning tunneling microscope. I also present in this thesis the theoretical predictions for the height distribution at the surface as well as some more general structural information about the relaxation in the network as one goes away from the surface. Finally, I have studied the effect of size -mismatch in a purely two dimensional lattice, looking for mismatch-driven phase transitions. Although it is possible to map size-mismatch on an effective temperature at low disorder, I have not been able to find any indication that a hexatic phase exists in these 2d systems. Since systems were studied with different potentials in very large unit cells, the conclusion is that the hexatic phase is not universal for two dimensional networks.

Mousseau, Normand

349

Fatigue Strength Characteristics of Non-Combustible Mg Alloy  

NASA Astrophysics Data System (ADS)

An ignition point of a non-combustible Mg alloy is about 300K higher than that of a Mg alloy currently in use. It is expected that the non-combustible Mg alloy can be used as a substitute for Al alloys as structure components. In this paper, the fundamentals, the notch effect and the long or small crack effect on fatigue strength of the non-combustible Mg alloy, are investigated. Moreover, the fatigue strength characteristics of the non-combustible Mg alloy are compared with that of an Al alloy to clarify the differences in the fatigue strength characteristics between the non-combustible Mg alloy and Al alloy.

Fujii, Takumi; Morishige, Kazunori; Hamada, Shigeru; Noguchi, Hiroshi; Sakamoto, Michiru; Ueno, Hidetoshi

350

Primary solid solutions in binary nickel alloy systems  

Microsoft Academic Search

The alloying behavior of 40 binary nickel alloy systems was studied in order to determine the extent to which the Hume-Rothery alloying rules apply. An attempt was made to utilize computer facilities in seeking trends of systematic relationships among the various nickel alloys. The nickel-rich parts of the binary-alloy phase diagrams were considered.

R. Štefec

1971-01-01

351

Production of new titanium alloy for orthopedic implants  

Microsoft Academic Search

The beta titanium alloys is one of the most promising groups of the titanium alloys. This fact is due to the good formability, mechanical properties and potential applications; moreover, these alloys present the highest level of mechanical, fatigue and corrosion resistance. The beta titanium alloys present the lowest elastic modulus, an interesting property for orthopedic implants. A ? alloy recently

E. B. Taddei; V. A. R. Henriques; C. R. M. Silva; C. A. A. Cairo

2004-01-01

352

INCOLOY alloy 803, a cost effective alloy for high temperature service  

SciTech Connect

INCOLOY alloy 800 was the first of the 800 series of alloys invented by Inco Alloys International in the 1940`s. Because of its excellent oxidation and carburization resistance as well as high temperature creep strength, alloy 800 found uses for many applications such as heat treating hardware, petrochemical processing, home appliances, food processing, industrial heating, super-heater and re-heater tubing and soon became the workhorse material for the chemical processing industries. Alloy 803 has superior resistance to oxidation and carburization without sacrificing mechanical properties. In this paper the history of alloy 800 with introductions of alloys 800H and 800HT and the differences in properties and chemical compositions among them will be described. The development of alloy 803 for petrochemical applications is also covered. The performance of alloy 803 in cyclic oxidation, carburization and sulfidation tests will be presented and compared with several alloys including alloy HPM. The mechanical properties of alloy 803 including room temperature and high temperature tensile data and stress rupture and creep strengths up to 1,093 C (2,000 F) will be presented. The choice of available filler metals and welding electrodes to join alloy 803, using gas metal arc welding and shielded metal arc welding processes, will also be presented.

Ganesan, P.; Plyburn, J.A.; Tassen, C.S. [INCO Alloys International, Inc., Huntington, WV (United States)

1995-12-31

353

Method of producing superplastic alloys and superplastic alloys produced by the method  

NASA Technical Reports Server (NTRS)

A method for producing new superplastic alloys by inducing in an alloy the formation of precipitates having a sufficient size and homogeneous distribution that a sufficiently refined grain structure to produce superplasticity is obtained after subsequent PSN processing. An age-hardenable alloy having at least one dispersoid phase is selected for processing. The alloy is solution heat-treated and cooled to form a supersaturated solid solution. The alloy is plastically deformed sufficiently to form a high-energy defect structure useful for the subsequent heterogeneous nucleation of precipitates. The alloy is then aged, preferably by a multi-stage low and high temperature process, and precipitates are formed at the defect sites. The alloy then is subjected to a PSN process comprising plastically deforming the alloy to provide sufficient strain energy in the alloy to ensure recrystallization, and statically recrystallizing the alloy. A grain structure exhibiting new, fine, equiaxed and uniform grains is produced in the alloy. An exemplary 6xxx alloy of the type capable of being produced by the present invention, and which is useful for aerospace, automotive and other applications, is disclosed and claimed. The process is also suitable for processing any age-hardenable aluminum or other alloy.

Troeger, Lillianne P. (Inventor); Starke, Jr., Edgar A. (Inventor); Crooks, Roy (Inventor)

2002-01-01

354

Progress in ODS Alloys: A Synopsis of a 2010 Workshop on Fe- Based ODS Alloys  

SciTech Connect

In Fall 2010, a workshop on the role and future of Fe-based Oxide Dispersion Strengthened (ODS) alloys gathered together ODS alloy suppliers, potential industrial end-users, and technical experts in relevant areas. Presentations and discussions focused on the current state of development of these alloys, their availability from commercial suppliers, past major evaluations of ODS alloy components in fossil and nuclear energy applications, and the technical and economic issues attendant to commercial use of ODS alloys. Significant progress has been achieved in joining ODS alloys, with creep resistant joints successfully made by inertia welding, friction stir welding and plasma-assisted pulse diffusion bonding, and in improving models for the prediction of lifetime components. New powder and alloy fabrication methods to lower cost or improve endproduct properties were also described. The final open discussion centered on challenges and pathways for further development and large-scale use of ODS alloys.

Kad, Bimal [University of California, San Diego; Dryepondt, Sebastien N [ORNL; Jones, Andy R. [University of Liverpool; Vito, Cedro III [National Energy Technology Laboratory (NETL); Tatlock, Gordon J [ORNL; Pint, Bruce A [ORNL; Tortorelli, Peter F [ORNL; Rawls, Patricia A. [National Energy Technology Laboratory (NETL)

2012-01-01

355

Status of Testing and Characterization of CMS Alloy 617 and Alloy 230  

SciTech Connect

Status and progress in testing and characterizing CMS Alloy 617 and Alloy 230 tasks in FY06 at ORNL and INL are described. ORNL research has focused on CMS Alloy 617 development and creep and tensile properties of both alloys. In addition to refurbishing facilities to conduct tests, a significant amount of creep and tensile data on Alloy 230, worth several years of research funds and time, has been located and collected from private enterprise. INL research has focused on the creep-fatigue behavior of standard chemistry Alloy 617 base metal and fusion weldments. Creep-fatigue tests have been performed in air, vacuum, and purified Ar environments at 800 and 1000 C. Initial characterization and high-temperature joining work has also been performed on Alloy 230 and CCA Alloy 617 in preparation for creep-fatigue testing.

Ren, Weiju [ORNL; Santella, Michael L [ORNL; Battiste, Rick [ORNL; Terry, Totemeier [Idaho National Laboratory (INL); Denis, Clark [Idaho National Laboratory (INL)

2006-08-01

356

Preparation of TiMn alloy by mechanical alloying and spark plasma sintering for biomedical applications  

NASA Astrophysics Data System (ADS)

TiMn alloy was prepared by mechanical alloying and subsequently consolidated by spark plasma sintering (SPS) technique for exploration of biomedical applications. The microstructures, mechanical properties and cytotoxicity of the TiMn alloys were investigated in comparison with the pure Ti and Mn metals. Ti8Mn and Ti12Mn alloys with high relative density (99%) were prepared by mechanical alloying for 60 h and SPS at 700 °C for 5 min. The doping of Mn in Ti has decreased the transformation temperature from ? to ? phase, increased the relative density and enhanced the hardness of the Ti metal significantly. The Ti8Mn alloys showed 86% cell viability which was comparable to that of the pure Ti (93%). The Mn can be used as a good alloying element for biomedical Ti metal, and the Ti8Mn alloy could have a potential use as bone substitutes and dental implants.

Zhang, F.; Weidmann, A.; Nebe, B. J.; Burkel, E.

2009-01-01

357

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

358

Copper and nickel adherently electroplated on titanium alloy  

NASA Technical Reports Server (NTRS)

Anodic treatment of titanium alloy enables electroplating of tightly adherent coatings of copper and nickel on the alloy. The alloy is treated in a solution of hydrofluoric and acetic acids, followed by the electroplating process.

Brown, E. E.

1967-01-01

359

A highly ductile magnesium alloy system  

NASA Astrophysics Data System (ADS)

Magnesium (Mg) alloys are finding increasing applications in industry mainly due to their high strength-to-weight ratio. However, they have intrinsically poor plastic deformation ability at room temperature. Therefore, the vast majority of Mg alloys are used only in cast state, severely limiting the development of their applications. We have recently discovered a new Mg alloy system that possesses exceptionally high ductility as well as good mechanical strength. The superior plasticity allows this alloy system to be mechanically deformed at room temperature, directly from an as-cast alloy plate, sheet or ingot into working parts. This type of cold mechanical forming properties has never been reported with any other Mg alloy systems.

Gao, W.; Liu, H.

2009-08-01

360

Nickel aluminide alloy suitable for structural applications  

DOEpatents

Alloys for use in structural applications based upon NiAl to which are added selected elements to enhance room temperature ductility and high temperature strength. Specifically, small additions of molybdenum produce a beneficial alloy, while further additions of boron, carbon, iron, niobium, tantalum, zirconium and hafnium further improve performance of alloys at both room temperature and high temperatures. A preferred alloy system composition is Ni--(49.1.+-.0.8%)Al--(1.0.+-.0.8%)Mo--(0.7.+-.0.5%)Nb/Ta/Zr/Hf--(nearly zero to 0.03%)B/C, where the % is at. % in each of the concentrations. All alloys demonstrated good oxidation resistance at the elevated temperatures. The alloys can be fabricated into components using conventional techniques.

Liu, Chain T. (Oak Ridge, TN)

1998-01-01

361

Annealing behavior of high permeability amorphous alloys  

SciTech Connect

Effects of low temperature annealing on the magnetic properties of the amorphous alloy Co/sub 71/ /sub 4/Fe/sub 4/ /sub 6/Si/sub 9/ /sub 6/B/sub 14/ /sub 4/ were investigated. Annealing this alloy below 400/sup 0/C results in magnetic hardening; annealing above 400/sup 0/C but below the crystallization temperature results in magnetic softening. Above the crystallization temperature the alloy hardens drastically and irreversibly. Conventional and high resolution transmission electron microscopy were used to show that the magnetic property changes at low temperatures occur while the alloy is truly amorphous. By imaging the magnetic microstructures, Lorentz electron microscopy has been able to detect the presence of microscopic inhomogeneities in this alloy. The low temperature annealing behavior of this alloy has been explained in terms of atomic pair ordering in the presence of the internal molecular field. Lorentz electron microscopy has been used to confirm this explanation.

Rabenberg, L.

1980-06-01

362

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.

2014-12-01

363

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

364

High-temperature property data: Ferrous alloys  

SciTech Connect

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 the high-temperature properties and applications. Referenced data is then given for physical properties such as density, specific heat, thermal conductivity, thermal expansion, electrical conductivity, Poisson's ratio, moduli of elasticity and rigidity, etc. Mechanical properties follow, and include tensile properties, shearing and bearing properties, impact properties, creep, stress rupture and stress relaxation and fatigue properties. The last part of the alloy record gives other effects of temperature, such as hot hardness, corrosion, and growth.

Rothman, M.F.

1987-01-01

365

Compressive deformation behaviour of magnesium alloys  

Microsoft Academic Search

The compressive deformation behaviour of magnesium alloys AZ91, AE42, AS21, QE22, ZE41, Mg4Li, and Mg8Li has been studied. The alloys were tested in the temperature range 23–300°C. The differences in the deformation behaviour of the alloys are discussed in terms of hardening and softening processes. Non-dislocation obstacles and forest dislocations are considered as the main obstacles for the moving dislocations,

Z. Trojanová; P. Luká?

2005-01-01

366

Newly developed magnesium alloys for powertrain applications  

Microsoft Academic Search

Several new magnesium alloys have been developed recently for high-temperature applications to obtain an optimal combination\\u000a of die cast-ability, creep resistance, mechanical properties, corrosion performance, and affordability. Unfortunately, it\\u000a is difficult to achieve an adequate combination of properties and, in fact, most of the new alloys can only partially meet\\u000a the required performance and cost. The ZE41 alloy, which is

E. Aghion; B. Bronfín; F. Von Buch; S. Schumann; H. Friedrich

2003-01-01

367

New magnesium alloys for transmission parts  

Microsoft Academic Search

Metallurgical aspects of the development of new magnesium alloys for the production of transmission parts and assemblies with\\u000a the use of sand mold casting, chill casting, and high-pressure die casting are considered. The approach suggested has been\\u000a used for creating new alloys with elevated creep resistance. The properties of the alloys are presented and compared with\\u000a the properties of known

B. Bronfin; N. Moscovitch

2006-01-01

368

Mechanical properties of biomedical titanium alloys  

Microsoft Academic Search

Titanium alloys are expected to be much more widely used for implant materials in the medical and dental fields because of their superior biocompatibility, corrosion resistance and specific strength compared with other metallic implant materials. Pure titanium and Ti–6Al–4V, in particular, Ti–6Al–4V ELI have been, however, mainly used for implant materials among various titanium alloys to date. V free alloys

Mitsuo Niinomi

1998-01-01

369

TITANIUM ALLOYS IN 600 F AMMONIATED WATER  

Microsoft Academic Search

Three high-strength titanium alloys, (Ti--6Al--4V), (Ti--6Al--6V--2Sn), ; and (Ti--13V--11Cr--3Al), were corrosion tested in 800 deg F ammoniated water at ; pH 10. There was no significant change in mechanical properties before and after ; exposure in test solution for two alloys, (Ti -- 6Al --4V) and (Ti-- 6Al --2Sn). ; The high vanadiumchromium alloy (Ti -- 13V -- 11Cr-- 3Al)

C. F. Cheng; S. F. Bubar; J. J. McCarthy

1963-01-01

370

Vapor phase lubrication of high temperature alloys  

Microsoft Academic Search

In a previous study, it was found that when a nickel-based superalloy IN750 was heated to high temperatures, a passive layer of aluminum oxide formed on the surface, preventing vapor phase lubrication. In this study, two nickel-chrome-iron alloys and a nickel-copper alloy were studied for high temperature lubrication to see if these alloys, which contained small amounts of aluminum, would

B. F. Hanyaloglu; E. E. Graham; T. Oreskovic; C. G. Hajj

1995-01-01

371

Superconductivity of Technetium Alloys and Compounds  

Microsoft Academic Search

The superconducting transition temperatures of Mo-Tc alloys are reported. Critical field measurements of a 50 atomic percent alloy indicate that it might be a promising material for superconducting magnets. The similarity of Tc and Re with respect to alloy and intermetallic compound formation is noted. The superconducting transition temperatures of the compounds ZrTc6 and NbTc3 are 9.7°K and 10.5°K, respectively.

V. B. Compton; E. Corenzwit; J. P. Maita; B. T. Matthias; F. J. Morin

1961-01-01

372

Rapidly Solidified Aluminum Alloys: A Market Assessment  

NASA Astrophysics Data System (ADS)

A survey of the markets for rapidly solidified, high strength aluminum alloys has been made by Charles River Associates1 on the basis of currently available technologies. This survey includes an assessment of potentially new developments, Advanced powder metallurgy technologies possess a visible market potential primarily in applications requiring high strength, heat treatable alloys of modified 7075 composition (currently alloys 7090 and 7091) and lithium bearing 2XXX series.

Lavernia, E.; Poggiali, B.; Servi, I.; Clark, J.; Katrak, F.; Grant, N.

1985-11-01

373

Order–disorder reaction in Alloy 600  

Microsoft Academic Search

Differential scanning calorimetric tests were carried out in Alloy 600 from room temperature to 800°C on various specimens, in order to investigate the origin of the exothermic and endothermic reactions that occur during thermal analyses. Since it is reasonable that there is a Ni2Cr short-range order in Alloy 600, which is a Cr-rich Ni-base alloy, the differential scanning calorimetry (DSC)

SungSoo Kim; Il Hyun Kuk; Joung Soo Kim

2000-01-01

374

Properties and microstructures for dual alloy combinations of three superalloys with alloy 901  

NASA Technical Reports Server (NTRS)

Dual alloy combinations have potential for use in aircraft engine components such as turbine disks where a wide range of stress and temperature regimes exists during operation. Such alloy combinations may directly result in the conservation of elements which are costly or not available domestically. Preferably, a uniform heat treatment yielding good properties for both alloys should be used. Dual alloy combinations of iron rich Alloy 901 with nickel base superalloys Rene 95, Astroloy, or MERL 76 were not isostatically pressed from prealloyed powders. Individual alloys, alloy mixtures, and layered alloy combinations were given the heat treatments specified for their use in turbine disks or appropriate for Alloy 901. Selected specimens were overaged for 1500 hr at 650 C. Metallographic examinations revealed the absence of phases not originally present in either alloy of a combination. Mechanical tests showed adequate properties in combinations of Rene 95 or Astroloy with Alloy 901 when given the Alloy 901 heat treatment. Combinations with MERL 76 had better properties when given the MERL 76 heat treatment. The results indicate that these combinations are promising candidates for use in turbine disks.

Harf, F. H.

1985-01-01

375

Magnesium alloys laser (Nd:YAG) cladding and alloying with side injection of aluminium powder  

Microsoft Academic Search

The development of the high purity magnesium alloys (such as WE43) incites the designers to reconsider them, and the car industry appears, these days, the most interested to use this kind of alloy. However, due to their ignitability and tendency to oxidation, magnesium alloys require surface treatments. A series of experiments was carried out in order to improve the corrosion

Sorin Ignat; Pierre Sallamand; Dominique Grevey; Michel Lambertin

2004-01-01

376

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

377

Bioreactivity of Titanium Implant Alloys  

NASA Astrophysics Data System (ADS)

A study was conducted regarding the adsorption of peptides on cp titanium and Ti-6Al-4V. The peptides used were arginine-glycine-aspartic acid-alanine (RGDA), arginine-glycine-aspartic acid-serine (RGDS), and arginine -phenylalanine-aspartic acid-serine (RFDS). The tripeptide RGD is known to be important for biologically specific adhesion reactions. CP titanium and Ti-6Al-4V are widely used implant alloys. This research was conducted to investigate the reason for a tendency toward thrombus formation with Ti-6Al-4V that is not observed with cp titanium. It was determined that clean surfaces are critical for the adhesion of biomolecules to an implant surface and that the surface must have a sufficiently high energy. Argon plasma cleaning was found to provide suitable surfaces with these properties. Coupons of cp titanium and Ti-6Al-4V were inserted into solutions with variable concentrations (0.0625 mg/ml to 2 mg/ml) of an individual peptide group under constant temperature and time conditions. The samples were rinsed, dried, and analyzed with x-ray photoelectron spectroscopy (XPS). Adsorption isotherms were obtained by plotting the relative amount of peptide adhesion as a function of solution concentration. It was determined with XPS that the major adhesion mechanism for the peptides to the titanium alloys was hydrogen bonding. CP titanium and Ti-6Al-4V may react differently as implants because Ti-6Al-4V has a more electropositive surface which allows fewer hydrogen bonds to form. Hydrophilic reactions were of secondary importance during bioadhesion, influencing the structure of the second layer adsorbed. There was no correlation found between the net charge of the peptide groups and their adhesion to the alloys. XPS also showed that there was incomplete peptide coverage of the surface of the titanium alloys.

Kerber, Susan Jane

378

Superconducting Technetium-Tungsten Alloys  

Microsoft Academic Search

The transition temperatures, critical fields, electrical resistivities, and crystalline structures of a series of technetium-tungsten alloys containing up to 60 at.% technetium are reported. Tc increases monotonically to 7.9°K and Hc2 (at 4.2°K) to 43.5 kG for 60 at.% technetium. The samples are single-phase solid solutions up to 40 at.% Tc, but a sigma phase is present at higher concentrations.

S. H. Autler; J. K. Hulm; R. S. Kemper

1965-01-01

379

Surface bond strength in nickel based alloys.  

PubMed

Bonding of ceramic to the alloy is essential for the longevity of porcelain fused to metal restorations. Imported alloys used now a days in processing them are not economical. So this study was conducted to evaluate and compare the bond strength of ceramic material to nickel based cost effective Nonferrous Materials Technology Development Center (NFTDC), Hyderabad and Heraenium S, Heraeus Kulzer alloy. An Instron testing machine, which has three-point loading system for the application of load onto the specimen was utilized for analyzing bond strength of both alloys. Student t test was conducted and t value obtained was 0.644, and the mean value of flexural bond strength of indigenous alloy is 81.75 with standard deviation of 12.25 and of imported alloy is 84.42 with standard deviation of 10.35, indicating that there was no significant difference between the two alloys. Due to ever increasing cost of imported non-precious alloy the need for a cost-effective replacement was fulfilled by indigenous NFTDC alloy. PMID:24431791

Ramesh, Ganesh; Padmanabhan, T V; Ariga, Padma; Joshi, Shalini; Bhuminathan, S; Vijayaraghavan, Vasantha

2013-12-01

380

Nondestructive determination of mechanical properties. [aluminum alloys  

NASA Technical Reports Server (NTRS)

Aluminum alloys of types 1100, 3003, 5052, 6061, and 2024 were used to study the sensitivity of the acousto-elastic constant to changes in the microstructure. Results show that there is a strong relationship between the acousto-elastic constants and the yield strength and hardness. This relationship depends on whether the alloy is strain hardened or precipitation hardened. In strain hardened alloys, the constants increase as the amount of solid solution is decreased, while the behavior is the opposite in precipitation hardened alloys.

Schneider, E.; Chu, S. L.; Salma, K.

1984-01-01

381

Newly developed magnesium alloys for powertrain applications  

NASA Astrophysics Data System (ADS)

Several new magnesium alloys have been developed recently for high-temperature applications to obtain an optimal combination of die cast-ability, creep resistance, mechanical properties, corrosion performance, and affordability. Unfortunately, it is difficult to achieve an adequate combination of properties and, in fact, most of the new alloys can only partially meet the required performance and cost. The ZE41 alloy, which is used for most gravity-casting applications, has moderate strength and creep resistance combined with good cast-ability. Although this alloy exhibits poor corrosion resistance, it is still preferred for certain applications.

Aghion, E.; Bronfín, B.; von Buch, F.; Schumann, S.; Friedrich, H.

2003-11-01

382

Evaluation of Sc-Bearing Aluminum Alloy  

E-print Network

The performance of the Al-Mg-Sc alloy C557 was evaluated to assess its potential for a broad range of aerospace applications, including airframe and launch vehicle structures. Of specific interest were mechanical properties at anticipated service temperatures and thermal stability of the alloy. Performance was compared with conventional airframe aluminum alloys and with other emerging aluminum alloys developed for specific service environments. Mechanical properties and metallurgical structure were evaluated for commercially rolled sheet in the as-received H116 condition and after thermal exposures at 107 C. Metallurgical analyses were performed to define grain morphology and texture, strengthening precipitates, and to assess the effect of thermal exposure.

Langley Research Center; Marcia S. Domack; Dennis L. Dicus

2002-01-01

383

Forming of cast precious metal alloys.  

PubMed

It has proven possible to express the true stress-true strain behavior of dental casting alloys by means of a general equation with empirically determined constants. It was also found that the appropriate strain hardening equation for the precious alloys used in this investigation was an exponential function. Integration of the equations, using individually determined constants, made it possible to calculate the work necessary to plastically deform the alloys to a final true strain of 0.05 or any other realistic value. Comparisons of the ease of forming the alloys investigated here showed that this technique yields results similar to those encountered in clinical experience. PMID:7024359

Baran, G; Woodland, E C

1981-10-01

384

Microbial corrosion of aluminum alloy.  

PubMed

Several microbes were isolated from the contaminated fuel-oil in Taiwan and the microbial corrosion of aluminum alloy A356-T6 was tested by MIL-STD-810E test method. Penicillium sp. AM-F5 and Cladosporium resinac ATCC 22712 had significant adsorption and pitting on the surface of aluminum alloy, Pseudomonas acruginosa AM-B5 had weak adsorption and some precipitation in the bottom, and Candida sp. AM-Y1 had the less adsorption and few cavities formation on the surface. pH of the aqueous phase decreased 0.3 to 0.7 unit for 4 months of incubation. The corrosion of aluminum alloy was very significant in the cultures of Penicillium sp. AM-F2, Penicillium sp. AM-F5 and C. resinac ATCC 22712. The major metabolites in the aqueous phase with the inoculation of C. resinac were citric acid and oxalic acid, while succinic acid and fumaric acid were the minors. PMID:10592801

Yang, S S; Chen, C Y; Wei, C B; Lin, Y T

1996-11-01

385

Interfacial adsorption in ternary alloys  

SciTech Connect

Interfaces of A-B-C ternary alloys decomposed into two and three phases are studied. The effect of the gradient energy coefficients {bar {kappa}}{sub II}, I = A, B, C, on the interface composition profiles of ternary alloys is examined. The adsorption of component C in ternary alloys is obtained numerically by finding steady-state solutions of the nonlinear Cahn-Hilliard equations and by solving the two Euler-Lagrange equations resulting from minimizing the interfacial energy, and analytically near the critical point. It is found that the solutions from both numerical methods are identical for a two-phase system. In symmetric ternary systems (equal interaction energy between each pair of components) with a minority component C, the gradient energy coefficient of C, {bar {kappa}}{sub CC}, can have a very strong influence on the degree of adsorption. In the {alpha} and {beta} two-phase regions, where {alpha} and {beta} are the phases rich in the majority components A and B, respectively, as {bar {kappa}}{sub CC} increases, the adsorption of the minority component C in the {alpha} and {beta} interfaces decreases. Near a critical point, however, the degree of adsorption of minority component C is independent of the gradient energy coefficient.

Huang, C.; Cruz, M.O. de la; Voorhees, P.W.

1999-11-26

386

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

387

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

388

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

389

Laser Welding of Aluminum and Aluminum Alloys  

E-print Network

.. ) Laser Welding of Aluminum and Aluminum Alloys Welds made with sharp bevel-groove weld aluminum and by aluminum alloy 5456 have been studied. The results indicate that initial absorption varies of the most dramatic illustrations of the differences in beam characteristics occurs when welding aluminum

Eagar, Thomas W.

390

Titanium alloys for fracture fixation implants  

Microsoft Academic Search

This paper is intended to provide an overview of the composition, mechanical properties, biocompatibility, and clinical applications for titanium alloys that are used for fracture fixation implants. A new class of titanium implant alloys has emerged in recent years that exhibits a ? microstructure and a unique combination of mechanical properties. Important information regarding notch sensitivity testing and clinical significance

J. A. Disegi

2000-01-01

391

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

392

Manufacturing and Microstructural Evolution of Mechanuically Alloyed  

E-print Network

REVIEWS Manufacturing and Microstructural Evolution of Mechanuically Alloyed Oxide Dispersion alloying can be as large as 9; there is proof that this leads to mixing on an atomic scale.50+.50/0 #12;Capdevila, Bhadeshia/Manufacturing and Microstructural Evolution REVIEWS processing including heat

Cambridge, University of

393

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; Smith, John R.

1991-01-01

394

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

395

Materials data handbook: Aluminum alloy 2219  

NASA Technical Reports Server (NTRS)

A summary of the materials property information for aluminum 2219 alloy is presented. The scope of the information includes physical and mechanical properties at cryogenic, ambient, and elevated temperatures. Information on material procurement, metallurgy of the alloy, corrosion, environmental effects, fabrication, and joining techniques is developed.

Muraca, R. F.; Whittick, J. S.

1972-01-01

396

Tantalum modified ferritic iron base alloys  

NASA Technical Reports Server (NTRS)

Strong ferritic alloys of the Fe-CR-Al type containing 0.4% to 2% tantalum were developed. These alloys have improved fabricability without sacrificing high temperature strength and oxidation resistance in the 800 C (1475 F) to 1040 C (1900 F) range.

Oldrieve, R. E.; Blankenship, C. P. (inventors)

1977-01-01

397

Processing depleted uranium quad alloy penetrator rods  

Microsoft Academic Search

Two depleted uranium (DU) quad alloys were cast, extruded and rolled to produce penetrator rods. The two alloy combinations were (1) 1 wt % molybdenum (Mo), 1 wt % niobium (Nb), and 0.75 wt % titanium (Ti); and (2) 1 wt % tantalum (Ta), 1 wt % Nb, and 0.75 wt % Ti. This report covers the processing and results

Bokan

1987-01-01

398

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

399

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

400

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

401

Theoretical Studies of Hydrogen Storage Alloys  

Microsoft Academic Search

Theoretical calculations were carried out to search for lightweight alloys that can be used to reversibly store hydrogen in mobile applications, such as automobiles. Our primary focus was on magnesium based alloys. While MgHâ is in many respects a promising hydrogen storage material, there are two serious problems which need to be solved in order to make it useful: (i)

Hannes

2012-01-01

402

Plasma deposition of amorphous metal alloys  

DOEpatents

Amorphous metal alloy coatings are plasma-deposited by dissociation of vapors of organometallic compounds and metalloid hydrides in the presence of a reducing gas, using a glow discharge. Tetracarbonylnickel, phosphine, and hydrogen constitute a typical reaction mixture of the invention, yielding a NiPC alloy.

Hays, Auda K. (Albuquerque, NM)

1986-01-01

403

Tantalum-columbium-molybdenum-tungsten alloy  

SciTech Connect

Disclosed is a novel refractory metal alloy that retains the essential characteristics of pure tantalum and, additionally, has improved engineering characteristics and may be produced at a lower cost than pure tantalum. The alloy nominally contains, by weight, about 58% tantalum, about 2.0% molybdenum, about 2.5% tungsten and about 37.5% columbium.

Huber Jr., L. E.; Schwartz, H. D.

1985-07-02

404

Alloys of clathrate allotropes for rechargeable batteries  

DOEpatents

The present disclosure is directed at an electrode for a battery wherein the electrode comprises clathrate alloys of silicon, germanium or tin. In method form, the present disclosure is directed at methods of forming clathrate alloys of silicon, germanium or tin which methods lead to the formation of empty cage structures suitable for use as electrodes in rechargeable type batteries.

Chan, Candace K; Miller, Michael A; Chan, Kwai S

2014-12-09

405

Silicon nitride reinforced nickel alloy composite materials  

Microsoft Academic Search

An erosion resistant composite material is described comprising silicon nitride rod reinforced nickel alloy, where the silicon nitride is cold pressed and sintered and substantially nonreactive with the alloy at high temperatures. The silicon nitride can either be polycrystalline or amorphous containing alumina, 15% yttria and about 2% to about 5% silica. Three to 8% alumina is used in the

F. S. Galasso; R. D. Veltri

1985-01-01

406

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

407

Precipitation hardening in aluminum alloy 6022  

SciTech Connect

Although the precipitation process in Al-Mg-Si alloys has been extensively studied, the understanding of the hardening process is still incomplete, since any change in composition, processing and aging practices, etc., could affect the precipitation hardening behavior. In this paper, hardness measurements, differential scanning calorimetry and transmission electron microscopy have been utilized to study the precipitation hardening behavior in aluminum alloy 6022.

Miao, W.F.; Laughlin, D.E. [Carnegie Mellon Univ., Pittsburgh, PA (United States). Dept. of Materials Science and Engineering] [Carnegie Mellon Univ., Pittsburgh, PA (United States). Dept. of Materials Science and Engineering

1999-03-05

408

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

409

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

410

Substitutional alloy of Ce and Al  

PubMed Central

The formation of substitutional alloys has been restricted to elements with similar atomic radii and electronegativity. Using high-pressure at 298 K, we synthesized a face-centered cubic disordered alloy of highly dissimilar elements (large Ce and small Al atoms) by compressing the Ce3Al intermetallic compound >15 GPa or the Ce3Al metallic glass >25 GPa. Synchrotron X-ray diffraction, Ce L3-edge absorption spectroscopy, and ab initio calculations revealed that the pressure-induced Kondo volume collapse and 4f electron delocalization of Ce reduced the differences between Ce and Al and brought them within the Hume-Rothery (HR) limit for substitutional alloying. The alloy remained after complete release of pressure, which was also accompanied by the transformation of Ce back to its ambient 4f electron localized state and reversal of the Kondo volume collapse, resulting in a non-HR alloy at ambient conditions. PMID:19188608

Zeng, Qiao-Shi; Ding, Yang; Mao, Wendy L.; Luo, Wei; Blomqvist, Andreas; Ahuja, Rajeev; Yang, Wenge; Shu, Jinfu; Sinogeikin, Stas V.; Meng, Yue; Brewe, Dale L.; Jiang, Jian-Zhong; Mao, Ho-kwang

2009-01-01

411

Activation analyses for different fusion structural alloys  

NASA Astrophysics Data System (ADS)

The leading candidate structural materials, viz., the vanadium alloys, the nickel or the manganese stabilized austenitic steels, and the ferritic steels, are analysed in terms of their induced activation in the TPSS fusion power reactor. The TPSS reactor has 1950 MW fusion power and inboard and outboard average neutron wall loading of 3.75 and 5.35 MW/m2, respectively. The results show that, after one year of continuous operation, the vanadium alloys have the least radioactivity at reactor shutdown. The maximum difference between the induced radioactivity in the vanadium alloys and in the other iron-based alloys occurs at about ten years after reactor shutdown. At this time, the FW-vanadium activation is three orders of magnitude less than other alloys' FW activation.

Attaya, H.; Smith, D.

1992-09-01

412

Comparison of Three Primary Surface Recuperator Alloys  

SciTech Connect

Extensive work performed by Capstone Turbine Corporation, Oak Ridge National Laboratory, and various others has shown that the traditional primary surface recuperator alloy, type 347 stainless steel, is unsuitable for applications above 650 C ({approx}1200 F). Numerous studies have shown that the presence of water vapor greatly accelerates the oxidation rate of type 347 stainless steel at temperatures above 650 C ({approx}1200 F). Water vapor is present as a product of combustion in the microturbine exhaust, making it necessary to find replacement alloys for type 347 stainless steel that will meet the long life requirements of microturbine primary surface recuperators. It has been well established over the past few years that alloys with higher chromium and nickel contents than type 347 stainless steel have much greater oxidation resistance in the microturbine environment. One such alloy that has replaced type 347 stainless steel in primary surface recuperators is Haynes Alloy HR-120 (Haynes and HR-120 are trademarks of Haynes International, Inc.), a solid-solution-strengthened alloy with nominally 33 wt % Fe, 37 wt % Ni and 25 wt % Cr. Unfortunately, while HR-120 is significantly more oxidation resistant in the microturbine environment, it is also a much more expensive alloy. In the interest of cost reduction, other candidate primary surface recuperator alloys are being investigated as possible alternatives to type 347 stainless steel. An initial rainbow recuperator test has been performed at Capstone to compare the oxidation resistance of type 347 stainless steel, HR-120, and the Allegheny Ludlum austenitic alloy AL 20-25+Nb (AL 20-25+Nb is a trademark of ATI Properties, Inc. and is licensed to Allegheny Ludlum Corporation). Evaluation of surface oxide scale formation and associated alloy depletion and other compositional changes has been carried out at Oak Ridge National Laboratory. The results of this initial rainbow test will be presented and discussed in this paper.

Matthews, Wendy [Capstone Turbines; More, Karren Leslie [ORNL; Walker, Larry R [ORNL

2010-01-01

413

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

414

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

415

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

416

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

417

SynthesisandCharacterizationof HalfMetallicHeusler Alloys  

E-print Network

SynthesisandCharacterizationof HalfMetallicHeusler Alloys Rohan Isaac Advisor: Dr. Amer Lahamer #12 polarized #12;HeuslerAlloys · Ferromagnetic Metal Alloys · Form: XYZ (L2) · First studied in 1903 halfmetals, the Heusler alloys have the greatest potential to become halfmetallic at room temperature due

Baltisberger, Jay H.

418

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

419

-Dispersed AA7075 Alloy Composites  

NASA Astrophysics Data System (ADS)

TiO2-dispersed AA7075 alloy composites were produced by mechanical milling followed by hot uniaxial compaction and sintering. The effects of volume fraction and dispersoid size on precipitation kinetics, densification, and hardness of the composites were studied in detail. While the sinterability of the composites decreases with increasing volume fraction of the particulate reinforcement (dispersoid), the same increases with decreasing particle size of the reinforcement. Microstructural analysis using X-ray diffraction and scanning electron microscopy shows an improvement in the distribution of reinforcement with decreasing particle size. The hardness of the composites increases with increasing volume fraction and decreasing TiO2 particle size. Further, the reinforced composites do not show age hardenability unlike unreinforced AA7075 alloy. Microstructural analysis reveals the formation of MgTiO3 and ZnO near the TiO2-AA7075 interface, which suppresses the formation of Guinier-Preston (GP) zone resulting in no age hardenability of the composites.

Karunanithi, R.; Ghosh, K. S.; Bera, Supriya

2014-08-01

420

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

421

A review on magnesium alloys as biodegradable materials  

Microsoft Academic Search

Magnesium alloys attracted great attention as a new kind of degradable biomaterials. One research direction of biomedical\\u000a magnesium alloys is based on the industrial magnesium alloys system, and another is the self-designed biomedical magnesium\\u000a alloys from the viewpoint of biomaterials. The mechanical, biocorrosion properties and biocompatibilities of currently reported\\u000a Mg alloys were summarized in the present paper, with the mechanical

Xue-Nan Gu; Yu-Feng Zheng

2010-01-01

422

Vapor phase lubrication of high temperature alloys  

SciTech Connect

In a previous study, it was found that when a nickel-based superalloy IN750 was heated to high temperatures, a passive layer of aluminum oxide formed on the surface, preventing vapor phase lubrication. In this study, two nickel-chrome-iron alloys and a nickel-copper alloy were studied for high temperature lubrication to see if these alloys, which contained small amounts of aluminum, would exhibit similar behavior. It was found that under static conditions, all three alloys formed a lubricious nodular coating when exposed to a vapor of aryl phosphate. Under dynamic sliding conditions at 500{degrees}C, these alloys were successfully lubricated with a coefficient of friction of 0.1 and no detectable wear. In order to explain these results, a direct correlation between successful vapor phase lubrication and the composition of the alloys containing aluminum has been proposed. If the ratio of copper/aluminum or iron/aluminum is greater that 100 vapor phase, lubrication will be successful. If the ratio is less than 10, a passive aluminum oxide layer will prevent vapor phase lubrication. By selecting alloys with a high iron or copper content, vapor phase lubrication can provide excellent lubrication at high temperatures. 14 refs., 11 figs., 1 tab.

Hanyaloglu, B.F.; Graham, E.E.; Oreskovic, T.; Hajj, C.G. [Cleveland State Univ., OH (United States)

1995-06-01

423

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, Joseph R.

1987-01-01

424

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

425

Dynamic Characterization of Shape Memory Titanium Alloys  

NASA Astrophysics Data System (ADS)

Evaluation of high strain rate behavior of materials at pre-fracture strains is very important where the materials are considered for ballistic applications. High compression strain rate response of shape memory titanium alloy including a typical titanium alloy are determined using the split Hopkinson pressure bar (SHPB). The conventional SHPB technique has been routinely used for measuring high strain rate properties of high strength materials. A split Hopkinson bar consisting of 10-mm diameter Maraging 350 alloy incident, transmitter, and striker bars was used to determine the compressive response of these alloys. Attempts are underway to use this technique to extract useful information required to design a material for improving its impact resistance. Initial test results performed on these different titanium alloys show an interesting trend with change of composition. Attempts were made to compare the stress-strain data of these alloys with the published data for titanium alloys. Stress-strain data and changes resulting in the microstructure from strain rates in the regime 1800-4000/s are presented.

Joshi, V. S.; Imam, M. A.

2004-07-01

426

Precipitates in Biomedical Co-Cr Alloys  

NASA Astrophysics Data System (ADS)

Herein, precipitates in biomedical Co-Cr-Mo and Co-Cr-W-Ni alloys are reviewed with a focus on their phase, chemical composition, morphology, and formation/dissolution during heat treatment. The effects of the heat-treatment conditions and the addition of minor alloying elements such as carbon, nitrogen, Si, and Mn on the precipitates are also discussed. Mostly, the precipitates in the alloys are of the ?-phase, M23X6-type phase, ?-phase (M6X-M12X type), ?-phase (M2T3X type), ?-phase, M7X3-type phase, or M2X-type phase (M and T refer to metallic elements, and X refers to carbon and/or nitrogen); the ?- and ?-phases are intermetallic compounds, and the others are carbides, nitrides, and carbonitrides. The dissolution of the precipitates during solution treatment is delayed by the formation of the ?-phase at temperatures where partial melting occurs in the alloys. In addition, the stability of the precipitates depends on the content of minor alloying elements. For example, the addition of carbon enhances the formation of M23X6-type and M7X3-type precipitates. Nitrogen stabilizes the M2X-type, ?-phase, and ?-phase precipitates, and Si stabilizes the ?-phase and ?-phase precipitates. The balance between the minor alloying element abundances also affects the constitution of the precipitates in Co-Cr alloys.

Narushima, Takayuki; Mineta, Shingo; Kurihara, Yuto; Ueda, Kyosuke

2013-04-01

427

Radiation-induced segregation in complex alloys  

SciTech Connect

Radiation-induced segregation (RIS) of alloying elements to the surface during 3 MeV /sup 58/Ni/sup +/ ion bombardment was investigated in alloys of Fe-200Cr-12Ni (at. %) containing controlled additions of Si and Mo. The segregation profiles, determined by Auger electron spectroscopy, show that Ni and Si are enriched, while Cr and Mo are depleted at the irradiated surfaces. The data indicates that the RIS of Ni and Cr are affected by the presence of Mo and Si in the alloy. However, no obvious trends are observed as a function of the minor solute element concentration. The temperature dependence of the RIS of the alloying elements was also investigated. A maximum of segregation at approx. 500/sup 0/C is observed for Si followed by a minimum and then a sharp increase in segregation at temperatures above 600/sup 0/C. The temperature dependence of segregation for Cr, Ni and Mo shows continous increase with temperature in the temperature regime investigated. The void swelling data on these alloys is also presented as a function of temperature and composition. Additions of Si reduce the swelling by affecting both the nucleation and the growth of the voids. The peak swelling temperature for all the alloys containing minor solutes are found to be lower (approx. 50/sup 0/C) than that of the base alloy (peak swelling temperature approx. 660/sup 0/C).

Sethi, V.K.; Okamoto, P.R.

1980-01-01

428

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

429

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

430

Antibacterial biodegradable Mg-Ag alloys.  

PubMed

The use of magnesium alloys as degradable metals for biomedical applications is a topic of ongoing research and the demand for multifunctional materials is increasing. Hence, binary Mg-Ag alloys were designed as implant materials to combine the favourable properties of magnesium with the well-known antibacterial property of silver. In this study, three Mg-Ag alloys, Mg2Ag, Mg4Ag and Mg6Ag that contain 1.87 %, 3.82 % and 6.00 % silver by weight, respectively, were cast and processed with solution (T4) and aging (T6) heat treatment. The metallurgical analysis and phase identification showed that all alloys contained Mg4Ag as the dominant ? phase. After heat treatment, the mechanical properties of all Mg-Ag alloys were significantly improved and the corrosion rate was also significantly reduced, due to presence of silver. Mg(OH)? and MgO present the main magnesium corrosion products, while AgCl was found as the corresponding primary silver corrosion product. Immersion tests, under cell culture conditions, demonstrated that the silver content did not significantly shift the pH and magnesium ion release. In vitro tests, with both primary osteoblasts and cell lines (MG63, RAW 264.7), revealed that Mg-Ag alloys show negligible cytotoxicity and sound cytocompatibility. Antibacterial assays, performed in a dynamic bioreactor system, proved that the alloys reduce the viability of two common pathogenic bacteria, Staphylococcus aureus (DSMZ 20231) and Staphylococcus epidermidis (DSMZ 3269), and the results showed that the killing rate of the alloys against tested bacteria exceeded 90%. In summary, biodegradable Mg-Ag alloys are cytocompatible materials with adjustable mechanical and corrosion properties and show promising antibacterial activity, which indicates their potential as antibacterial biodegradable implant materials. PMID:23771512

Tie, D; Feyerabend, F; Müller, W D; Schade, R; Liefeith, K; Kainer, K U; Willumeit, R

2013-01-01

431

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

432

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

433

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

434

Recycling of vanadium alloys in fusion reactors  

NASA Astrophysics Data System (ADS)

The feasibility of reprocessing a vanadium alloy after its use as a structural material in a fusion reactor, in order to enable its subsequent hands-on recycling within the nuclear industry, has been determined. For less neutron-exposed components, clearance of materials has also been considered. A conceptual model for the radiochemical processing of the alloy has been developed and tested experimentally. Using di-2-ethyl-hexyl-phosphoric acid it is possible to purify the components of the V-Cr-Ti alloy after its exposure in a fusion reactor down to the required level of activation product concentrations.

Bartenev, S. A.; Ciampichetti, A.; Firsin, N. G.; Forrest, R. A.; Kolbasov, B. N.; Kvasnitskij, I. B.; Romanov, P. V.; Romanovskij, V. N.; Zucchetti, M.

2007-08-01

435

Sucrose/Glucose molecular alloys by cryomilling.  

PubMed

We report here for the first time a series of amorphous sucrose/glucose molecular alloys prepared by cryomilling. Differential scanning calorimetry, X-ray powder diffraction and solution proton nuclear magnetic resonance showed that cryomilling drives a direct transformation from a two-phase mixture of crystalline sucrose and glucose, to a single-phase amorphous sucrose/glucose molecular alloy. The molecular alloys displayed a single Tg which varied linearly with composition. The effect of atmospheric moisture and the possibility of localised melting of the material because of milling-related friction were also discussed. PMID:24867316

Megarry, Andrew J; Booth, Jonathan; Burley, Jonathan

2014-07-01

436

Corrosion resistant nickel-iron alloy  

SciTech Connect

Disclosed is an alloy eminently suited for use as a tubular product in deep, sour gas operations. The alloy has an optimum combination of corrosion resistance, high strength in the cold worked condition and resistance to sulfide stress cracking and stress corrosion cracking. A typical alloy contains, in weight percent, 0.03 carbon, 22 chromium, 36 iron, 3 molybdenum, 1 manganese, 36 nickel, 0.60 silicon, 0.15 nitrogen, up to 3 tungsten and incidental impurities including copper, cobalt, columbium, tantalum and titanium.

Asphahani, A. I.; Kelley, E. W.; Kolts, J.

1984-12-18

437

K-resolved alloy bowing in pseudobinary In\\/sub x\\/Gaââ\\/sub x\\/As alloys  

Microsoft Academic Search

k-resolved alloy-bowing data for In\\/sub x\\/Gaââ\\/sub x\\/As alloys have been taken and used to examine the validity of different alloy formalisms. Although the molecular coherent-potential approximation is considered to be the most complete alloy formalism for zinc-blende pseudobinary alloys, it is not in agreement with the experimental k-resolved data. In contrast, these k-resolved data are in approximate agreement with the

J. Hwang; P. Pianetta; Y. Pao; C. K. Shih; Z. Shen; P. A. P. Lindberg; R. Chow

1988-01-01

438

Method for homogenizing alloys susceptible to the formation of carbide stringers and alloys prepared thereby  

DOEpatents

A novel fabrication procedure prevents or eliminates the reprecipitation of segregated metal carbides such as stringers in Ti-modified Hastelloy N and stainless steels to provide a novel alloy having carbides uniformly dispersed throughout the matrix. The fabrication procedure is applicable to other alloys prone to the formation of carbide stringers. The process comprises first annealing the alloy at a temperature above the single phase temperature for sufficient time to completely dissolve carbides and then annealing the single phase alloy for an additional time to prevent the formation of carbide stringers upon subsequent aging or thermomechanical treatment.

Braski, David N. (Oak Ridge, TN); Leitnaker, James M. (Kingston, TN)

1980-01-01

439

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

440

Thermal barrier coating for alloy systems  

DOEpatents

An alloy substrate is protected by a thermal barrier coating formed from a layer of metallic bond coat and a top coat formed from generally hollow ceramic particles dispersed in a matrix bonded to the bond coat.

Seals, Roland D. (Oak Ridge, TN); White, Rickey L. (Harriman, TN); Dinwiddie, Ralph B. (Knoxville, TN)

2000-01-01

441

Orthopaedic applications of ferromagnetic shape memory alloys  

E-print Network

Ferromagnetic shape memory alloys (FSMAs) are a new class of magnetic field-actuated active materials with no current commercial applications. By applying a magnetic field of around 0.4 T, they can exert a stress of ...

Guo, Weimin, M. Eng. Massachusetts Institute of Technology

2008-01-01

442

Study of high performance alloy electroforming  

NASA Technical Reports Server (NTRS)

The first series of heat treated nickel manganese alloys are tested for mechanical properties at temperatures of 148.9 C (300 F) and 260 C (500 F). All material receives the same heat treatment in order to provide a common basis for comparison of results. Mechanical property performance improves with increasing manganese content in the alloy. Although all manganese bearing alloy is significantly superior to conventional electroformed nickel, samples containing over 3000 ppm manganese display outstanding ultimate and yield strengths while maintaining reasonably satisfactory ductility. Alloy containing over 6000 ppm of manganese is very competitive to Inconel 718 (mill annealed and age hardened) at all temperatures of interest, although ductility is not as great in the electrodeposited counterpart.

Malone, G. A.

1984-01-01

443

Environmental Studies on Titanium Aluminide Alloys  

NASA Technical Reports Server (NTRS)

Titanium aluminides are attractive alternatives to superalloys in moderate temperature applications (600 to 850 C) by virtue of their high strength-to-density ratio (high specific strength). These alloys are also more ductile than competing intermetallic systems. However, most Ti-based alloys tend to degrade through interstitial embrittlement and rapid oxidation during exposure to elevated temperatures. Therefore, their environmental behavior must be thoroughly investigated before they can be developed further. The goals of titanium aluminide environmental studies at the NASA Lewis Research Center are twofold: characterize the degradation mechanisms for advanced structural alloys and determine what means are available to minimize degradation. The studies to date have covered the alpha 2 (Ti3Al), orthorhombic (Ti2AlNb), and gamma (TiAl) classes of alloys.

Brindley, William J.; Bartolotta, Paul A.; Smialek, James L.; Brady, Michael P.

2005-01-01

444

Environmental embrittlement in ordered intermetallic alloys  

SciTech Connect

Ordered intermetallics based on aluminides and silicides possess many promising properties for elevated-temperature applications; however, poor fracture resistance and limited fabricability restrict their use as engineering material. Recent studies have shown that environmental embrittlement is a major cause of low ductility and brittle fracture in many ordered intermetallic alloys. There are two types of environmental embrittlement observed in intermetallic alloys. One is hydrogen-induced embrittlement occurring at ambient temperatures in air. The other is oxygen-induced embrittlement in oxidizing atmospheres at elevated temperatures. In most cases, the embrittlements are due to a dynamic effect involving generation and penetration of embrittling agents (i.e., hydrogen or oxygen ) during testing. Diffusion of embrittling agents plays a dominant role in fracture of these intermetallic alloys. This chapter summarizes recent progress in understanding and reducing environmental embrittlement in these alloys.

Liu, C.T. [Oak Ridge National Lab., TN (United States); Stoloff, N.S. [Rensselaer Polytechnic Inst., Troy, NY (United States). Dept. of Materials Engineering

1992-12-31

445

Modeling wear of cast Ti alloys  

PubMed Central

The wear behavior of Ti-based alloys was analyzed by considering the elastic–plastic fracture of individual alloys in response to the relevant contact stress field. Using the contact stresses as the process driving force, wear was computed as the wear rate or volume loss as a function of hardness and tensile ductility for Ti-based cast alloys containing an ?, ?+? or ? microstructure with or without the intermetallic precipitates. Model predictions indicated that wear of Ti alloys increases with increasing hardness but with decreasing fracture toughness or tensile ductility. The theoretical results are compared with experimental data to elucidate the roles of microstructure in wear and contrasted against those in grindability. PMID:17224314

Chan, Kwai S.; Koike, Marie; Okabe, Toru

2007-01-01

446

Metal dusting of nickel-containing alloys  

SciTech Connect

Metal dusting is a catastrophic form of carburization which leads to pitting and grooves as the affected metal disintegrates into a mixture of powdery carbon, metallic particles, and possibly oxides and carbides. This high temperature carburization mode is not yet well understood and while relatively infrequent, can be economically disastrous when it does occur in large and complex chemical and petrochemical process streams. References in the literature show that all classes of heat resistant alloys are prone to metal dusting, given the necessary and specific environmental conditions. These same references describe the environments that plague nickel-containing alloys and are used as the basis for postulation on the probable corrosion mechanisms responsible for metal dusting. Using alloy 800 and other nickel-containing alloys and metal dusting atmospheres, an effort is made to examine the steps in the metal dusting process and the temperature ranges over which metal dusting occurs.

Baker, B.A.; Smith, G.D. [Inco Alloys International, Inc., Huntington, WV (United States)

1998-12-31

447

Alloy design with oxide dispersoids and precipitates  

NASA Technical Reports Server (NTRS)

The mechanical behavior of particle-strengthened alloys is reviewed. On the basis of this knowledge, it is concluded that second-phase particles, coherent or incoherent, can enhance the flow strength, creep resistance, and stress-rupture life of alloys. Unfortunately, particles are usually not beneficial alloy-design elements if enhanced uniaxial ductility, plane-strain ductility, stress-rupture ductility, and toughness are called for. Such properties as fatigue-crack propagation resistance appear to require, for example, both high strength and high ductility, a situation which can come to pass only when the perennial conflict between strength and ductility is resolved in particle-strengthened systems in particular and in any other material system in general. Wherever possible, the role of coherent and incoherent particles in alloy design is distinguished.

Tien, J. K.

1977-01-01

448

Study of fluoride corrosion of nickel alloys  

NASA Technical Reports Server (NTRS)

Report contains the results of an investigation of the corrosion resistance of nickel and nickel alloys exposed to fluorine, uranium hexafluoride, and volatile fission product fluorides at high temperatures. Survey of the unclassified literature on the subject is included.

Gunther, W. H.; Steindler, M. J.

1969-01-01

449

Corrosion performance of structural alloys.  

SciTech Connect

Component reliability and long-term trouble-free performance of structural materials are essential in power-generating and gasification processes that utilize coal as a feedstock. During combustion and conversion of coal, the environments encompass a wide range of oxygen partial pressures, from excess-air conditions in conventional boilers to air-deficient conditions in 10W-NO{sub x} and gasification systems. Apart from the environmental aspects of the effluent from coal combustion and conversion, one concern from the systems standpoint is the aggressiveness of the gaseous/deposit environment toward structural components such as waterwall tubes, steam superheaters, syngas coolers, and hot-gas filters. The corrosion tests in the program described in this paper address the individual and combined effects of oxygen, sulfur, and chlorine on the corrosion response of several ASME-coded and noncoded structural alloys that were exposed to air-deficient and excess-air environments typical of coal-combustion and gasification processes. Data in this paper address the effects of preoxidation on the subsequent corrosion performance of structural materials such as 9Cr-1Mo ferritic steel, Type 347 austenitic stainless steel, Alloys 800, 825, 625, 214, Hastelloy X, and iron aluminide when exposed at 650 C to various mixed-gas environments with and without HCI. Results are presented for scaling kinetics, microstructural characteristics of corrosion products, detailed evaluations of near-surface regions of the exposed specimens, gains in our mechanistic understanding of the roles of S and Cl in the corrosion process, and the effect of preoxidation on subsequent corrosion.

Natesan, K.

1999-07-15

450

Metal alloy coatings and methods for applying  

DOEpatents

A method of coating a substrate comprises plasma spraying a prealloyed feed powder onto a substrate, where the prealloyed feed powder comprises a significant amount of an alloy of stainless steel and at least one refractory element selected from the group consisting of titanium, zirconium, hafnium, niobium, tantalum, molybdenum, and tungsten. The plasma spraying of such a feed powder is conducted in an oxygen containing atmosphere and forms an adherent, corrosion resistant, and substantially homogenous metallic refractory alloy coating on the substrate.

Merz, Martin D. (Richland, WA); Knoll, Robert W. (Kennewick, WA)

1991-01-01

451

Mechanical and microstructural properties of alloy 800  

Microsoft Academic Search

The evolution of microstructural and mechanical properties of alloy 800 with respect to operating conditions of the steam\\u000a generator tubings of fast breeder reactors have been analyzed and presented. On the microstructural side two phenomena have\\u000a important influence on the mechanical properties, namely ?? and carbide precipitation. Gamma prime precipitation occurs in\\u000a alloy compositions containing ?0.50 pct Ti + Al,

A. A. Tavassoli; G. Colombe

1978-01-01

452

Alloys cathodically modified with noble metals  

Microsoft Academic Search

The truly remarkable corrosion resistance of alloys containing small amounts of noble metals relies on the principle that the high exchange-current density for the reduction of hydrogen can shift the corrosion potential of the alloy to a value in the passive region, causing it to passivate spontaneously. Research indicates that additions of 0.1 to 0.4% PGMs to chromium in sulphuric

J. H. Potgieter

1991-01-01

453

Microstructure of WE43 casting magnesium alloy  

Microsoft Academic Search

Purpose: WE43 is a high-strength magnesium alloy characterized by good mechanical properties both at an ambient and elevated temperature (up to 300°C). It contains mainly yttrium and neodymium. The aim of this paper is to present the results of research on the microstructure of the WE43 magnesium alloy in an as-cast condition. Design\\/methodology\\/approach: For the microstructure observation, a Reichert metallographic

T. Rzycho?; A. Kie?bus

454

Bulk Modulus Calculations for Liquid Binary Alloys  

NASA Astrophysics Data System (ADS)

In this work, the bulk modulus values as functions of concentration for K-Na, Cs-Na and Rb-Na liquid binary alloys have been studied in the framework of the Gibbs-Bogoliubov(GB) method[1-2]. We have used the local Heine-Abarenkov pseudopotential and Ichimaru-Utsumi screening function[3] and Percus-Yevick partial structure factors in these alloys. The results have been compared with the experimental values[4].

Yilmaz, Mehmet; Karagözlü, Seyfeddin; Dalgiç, Seyfettin

1997-01-01

455

Oxidation of alloys for advanced steam turbines  

SciTech Connect

Ultra supercritical (USC) power plants offer the promise of higher efficiencies and lower emissions. Current goals of the U.S. Department of Energy’s Advanced Power Systems Initiatives include coal generation at 60% efficiency, which would require steam temperatures of up to 760°C. This research examines the steamside oxidation of advanced alloys for use in USC systems, with emphasis placed on alloys for high- and intermediate-pressure turbine sections.

Holcomb, Gordon R.; Covino, Bernard S., Jr.; Bullard, Sophie J.; Ziomek-Moroz, M.; Alman, David E.

2005-01-01

456

Oxidation of advanced steam turbine alloys  

SciTech Connect

Advanced or ultra supercritical (USC) steam power plants offer the promise of higher efficiencies and lower emissions. Current goals of the U.S. Department of Energy’s Advanced Power Systems Initiatives include coal generation at 60% efficiency, which would require steam temperatures of up to 760°C. This research examines the steamside oxidation of advanced alloys for use in USC systems, with emphasis placed on alloys for high- and intermediate-pressure turbine sections.

Holcomb, G.R.; Covino, B.S., Jr.; Bullard, S.J.; Ziomek-Moroz, M.

2006-03-01

457

Hydrogen permeation in palladium--chromium alloys  

Microsoft Academic Search

As part of a search for new palladium alloys with attractive permeation characteristics for hydrogen isotopes, alloys containing 9.3, 16.8, and 24.2 atom percent chromium were evaluated in the temperature range from 322 to 449 K. The permeation coefficient, diffusion coefficient, and hydrogen solubility were all found to decrease with increasing chromium content. The solubility was found to obey Sievert's

W. A. Swansiger; J. H. Swisher; J. P. Darginis; C. W. Schoenfelder

1976-01-01

458

Hydrogen transport in nickel-base alloys  

Microsoft Academic Search

The electrochemical permeation technique has been used to characterize hydrogen transport and trapping in pure nickel and\\u000a in alloys 600, X-750, and 718 at a temperature of 80 ?C. The “effective diffusivity” of hydrogen atoms in alloy 600 is reduced\\u000a by a factor of about 5 compared to pure nickel. This is attributed to both compositional changes and the presence

A. Turnbull; R. G. Ballinger; I. S. Hwang; M. M. Morra; M. Psaila-Dombrowski; R. M. Gates

1992-01-01

459

Hydrogen transport in nickel-base alloys  

Microsoft Academic Search

The electrochemical permeation technique has been used to characterize hydrogen transport and trapping in pure nickel and\\u000a in alloys 600, X-750, and 718 at a temperature of 80 °C. The “effective diffusivity ” of hydrogen atoms in alloy 600 is reduced\\u000a by a factor of about 5 compared to pure nickel. This is attributed to both compositional changes and the

A. Turnbull; R. G. Ballinger; I. S. Hwang; M. M. Morra; M. Psaila-Dombrowski; R. M. Gates

1992-01-01

460

Internal gettering by metal alloy clusters  

DOEpatents

The present invention relates to the internal gettering of impurities in semiconductors by metal alloy clusters. In particular, intermetallic clusters are formed within silicon, such clusters containing two or more transition metal species. Such clusters have melting temperatures below that of the host material and are shown to be particularly effective in gettering impurities within the silicon and collecting them into isolated, less harmful locations. Novel compositions for some of the metal alloy clusters are also described.

Buonassisi, Anthony (San Diego, CA); Heuer, Matthias (Berkeley, CA); Istratov, Andrei A. (Albany, CA); Pickett, Matthew D. (Berkeley, CA); Marcus, Mathew A. (Berkeley, CA); Weber, Eicke R. (Piedmont, CA)

2010-07-27

461

Cryogenic properties of aluminum alloys and composites  

SciTech Connect

Several aluminum-based materials have been evaluated for possible application at cryogenic temperatures. These included the Al-Li alloy 2090, a high purity mechanically alloyed Al, SiC whisker reinforced Al 2124, and SiC particulate reinforced Al 6061. Mechanical properties, thermal properties and electrical properties were measured for these materials. Their performance in a radio frequency cavity was also determined. 4 refs., 6 figs.

Hill, M.A.; Rollett, A.D.; Jacobson, L.A.; Borch, N.R.; Gibbs, W.S.; Patterson, R.A.; Carter, D.H.

1989-01-01

462

Making Thin Laminae Of Frozen Alloy Slurries  

NASA Technical Reports Server (NTRS)

In new technique, primary objective to develop method to distribute uniformly-thin powder-metal-alloy layers between alternate fiber layers prior to consolidation. Involves use of sheets of frozen alloy powder. These laminae, interspersed with fiber mats, used to make metal/fiber composites. In addition to aerospace applications, this technique, appropriately modified, has potential in the manufacture of future automobile engines or components including molded ceramics.

Ghosh, A. K.; Holmes, L. M.; Houston, R. B.; Ecer, G. M.

1992-01-01

463

Tough strong iron alloys for cryogenic service  

NASA Technical Reports Server (NTRS)

Series of alloys with minor additions of reactive metals possesses outstanding strength and toughness at cryogenic