bluuebunny/crossref_metadata_2025_split huggingface dataset:
An Evaluation of Implantation-Disordering of (Inga)As/Gaas Strained-Layer Superlattices
Authors: Myers D. R. , Barnes C. E. , Arnold G. W. , Dawson L. R. , Biefeld R. M. , Zipperian T. E. , Gourley P. L. , Fritz I. J. 
Published: March 2011

AbstractWe have examined the optical and transport properties of In.2Ga.8As/GaAs straled-kayer superlZotices (SLS's), which have been implanted either with 5 × 1015/cm2, 250keV Zn+ or with 5 × 1014/cm2, 70keV Be+ and annealed under an arsenic overpressure at 600 °C. For both cases, electrical activation in the implantation-doped regions equalled that of similar implants and anneals in bulk GaAs, even though the Be implant retained the SLS structure, while the Zn implant intermixed the SLS layers to produce an alloy semiconductor of the average SLS composition. Photoluminescence intensities in the annealed implanted regions were significantly reduced from that of virgin material, apparently due to residual implant damage. Diodes formed from both the Be- and the Zn-implanted SLS's produced electroluminescence intensity comparable to that of grown-junction SLS diodes in the same chemical system, despite the implantation processing and the potential for vertical lattice mismatch in the Zn-disordered SLS device. These results indicate that Zn-disordering can be as useful in strained-layer superlattices as in lattice-matched systems.
Schottky Barrier Heights at Singe Crystal Metal Semiconductor Interfaces
Authors: Tung R. T. 
Published: March 2011

AbstractElectrical behavior at single crystal silicide-silicon interfaces was studied. Schottky barrier heights were determined for epitaxial NiSi2 and CoSi2 layers grown under ultrahigh vacuum conditions on (111), (100) and (110) surfaces of Si. A dependence of Schottky barrier heights on interface structure was observed. These results favor intrinsic mechanisms for Schottky barrier formation. The advantages of having homogeneous metal-semiconductor interfaces for the study of Schottky barrier mechanisms are pointed out. In particular, the present epitaxial silicide-silicon interfaces represent ideal candidates for detailed theoretical investigations based on experimentally obtained atomic structures.
Ion Channeling and Blocking Study of Ultra-Thin NiSi2 Films Grown on Atomically Clean Si(111) Surfaces
Authors: Van Loenen E. J. , Van Der Veen J. F. 
Published: March 2011

AbstractEpitaxial NiSi2 films of less than 40 Å thickness have been grown on atomically clean Si(111) surfaces. Ion channeling and blocking have been used to determine the morphology and orientation of these films, as well as the strain resulting from the lattice mismatch with the Si substrate. The films are found to be continuous for Ni coverages above 5×1015 atoms/cm2. For all coverages the films are (111) oriented but rotated 180° around the surface normal with respect to the substrate. The NiSi2-Si(111) interface has been probed directly by the ion beam and is found to be well ordered and atomically abrupt.
Pinning Action of a Thin Ga Interfacial Layer in an Sb/Ga/GaAs Schottky Barrier Structure Grown by MBE
Authors: Zhang X.-J. , Cheng H. , Milnes A. G. 
Published: March 2011

AbstractThe pinning action on the barrier height of a Ga interfacial layer in an Sb/Ga/GaAs structure prepared by molecular beam epitaxy has been tracked as a function of Ga layer thicknesses for both n and p-GaAs (100). The barrier height ÆBn for n-type GaAs (ND=3×1015cm−3), determined by thermal activation measurements and capacitance measurements, changes from 0.8 to 1.0 eV as the Ga layer is increased from zero to three monolayers. The barrier height ÆBp for p-type GaAs decreases in a converse fashion so that the sum ÆBn + ÆBp is equal to the GaAs energy gap. Up to a Ga layer thickness of about one monolayer the barrier height changes are about linearly proportional to thickness.The action seen is compatible with barrier height changes that are seen when Sb/GaAs junctions are prepared with the original surface alternatively As or Ga rich and subjected to thermal annealing at temperatures up to 250°C.
Atomic Structure of the Epitaxial Al/Si Interface
Authors: LeGoues F. K. , Krakow W. , Ho P. S. 
Published: March 2011

AbstractAl was deposited on Si(l l l) and observed by cross-sectional electron microscopy, both in the annealed and as deposited states. It is shown that Al is strongly textured when deposited on Si(111), with Al(111)//Si(111) and AI<110>//Si<110> or AI(100)//Si(111) and AI<I10>//Si<110>. Annealed samples are completely epitaxial with A1(111)//Si(111) and A1<110>//Si<110>. Lattices imaging of the interfaces shows an amorphous layer (native Si oxide) between Al and Si, in the as-deposited case. The two lattices are in contact only at pinholes in the native oxide and fringes on both sides of the interface are seen to be continuous through the interface only at those points. Annealed samples do not show any amorphous or disordered layer at the interface: The two lattices are completely in contact, with lattice fringes extending from one side of the interface to the other. An atomic model of the annealed interface, based on energy considerations and consistent with TEM observations, is proposed.
Effects of Incommensuracy on the Structural and Electrical Properties in PbTe-Bi Superlattice Films
Authors: Shin Sung-Chul 
Published: March 2011

AbstractWe studied the structural and electrical transport properties of incommensurate PbTe-Bi superlattice films. The properties of those samples were noticeably different from those of commensurate samples. For the incommensurate samples, the satellite peaks, in the 9–29 x-ray scans along the [111] growth orientation, became broader and the ratio of satellite intensities to the Bragg intensity became smaller. The resistances of incommensurate samples were about three times larger than those of corresponding commensurate ones. These features are interpreted by an enhancement of the lateral nonuniformity of interfaces in incommensurate samples. The exponential dependence of the resistance on temperature in incommensurate samples was also in contrast to the logarithmic behavior observed in commensurate ones.
Observation of the CdTe-GaAs Interface by High Resolution Electron Microscopy
Authors: Otsuka N. , Kolodziejski L. A. , Gunshor R. L. , Datta S. , Bicknell R. N. , Schetzina J. F. 
Published: March 2011

AbstractCdTe films have been grown on GaAs substrates with two types of interfaces - one with the epitaxial relation (111)CdTe║ (100)GaAs and the other with (100)CdTe║ (100)GaAs,. High resolution electron microscope observation of the two types of interfaces was carried out in order to determine the role of the substrate surface microstructure in determining the epitaxy. The interface of the former type shows a direct contact between the CdTe and GaAs crystals, while the interface of the latter type has a very thin oxide layer (∼10 Å in thickness) between the two crystals. These observations suggest that details of the substrate preheating cycle prior to film growth is the principle factor in determining which epitaxial relation occurs in this system. The relation between interfacial structures and the origin of the two epitaxial relations is discussed.
Electrical Contact and Adhesion Modification Produced by High Energy Heavy Ion Bombardment of Au Films on GaAs
Authors: Livi R. P. , Paine S. , Wie C. R. , Mendenhall M. H. , Tang J. Y. , Vreeland T. , Tombrello T. A. 
Published: March 2011

AbstractThin gold films over GaAs wafers with different dopants (Cr, Si, Te, and Zn) were used to study the role of he substrate electronic properties in the electrical contact and adhesion modification induced by MeV/nucleon heavy ion bombardment. The enhanced adhesion was studied using a scratch test; the results show very different modifications of adhesion depending on the bulk electronic properties of the substrate. The sample with a Cr compensation doped substrate showed enhancement in adhesion for beam doses as low as 1012 ions/cm2, but Si and Te doped (n–type) substrates showed a sudden enhancement in adhesion for doses around 1014 ions/cm2. Samples with Si and Te doped substrates were used to sudy the bombarding ion dE/dx dependence of the induced adhesion for 19F and 35C1 ions with electronic stopping power ranging from 161 eV/Å to 506 eV/Å. In this range the dose threshold fgfjhe ops! of induced adhesion has a power law dependence, D = D0(dE/dx)− (1.90 ± 1.0)
Improved Uniformity of Reacted GaAs Contacts by Interface Mixing
Authors: Palmrøm C. J. , Kavanagh K. L. , Hollis M. J. , Mukherjee S. D. , Mayer J. W. 
Published: March 2011

AbstractIon beam mixing is used to produce more uniform Au.Au-Ge and Au-Ge-Ni reacted contacts to GaAs.
Reaction of Amorphous Minb Films with Crystalline Metal Overlayers
Authors: Dobisz E. A. , Doyle B. L. , Perepezko J. H. , Wiley J. D. , Peercy P. S. 
Published: March 2011

AbstractIn many cases the stability of amorphous films is influenced by interaction with metallic crystalline overlayers. Such interactions between Au, Ni, Nb and Ta overlayers and a-(Ni-Nb) films are reported. During interdiffusion Au overlayers reacted with a-(Ni-Nb) to form two different adjacent crystalline layers. In order to study the influence of relaxation of the amorphous film on overlayer reaction several a-(Ni-Nb) samples were pre-annealed prior to Au deposition. High depth resolution Rutherford Backscattering Spectrometry (RBS) demonstrates that preannealing lowers the diffusion poefficient of Au in a-(Ni-Nb) at 4500C from 7.5×10−22 m2/s to 8.7×10−23 m22/s. During interdiffusion Ta was discovered to be substantially more inert than Au. For example, negligible interdiffusion between Ta and a-(Ni-Nb) at 505°C after 25 hours implies a diffusivity of less than 5×10−24 m2/s. These observations allow assessment of some of the requirements for increasing the stability of crystalline-amorphous metal film layered structures.
Superconducting Properties of Amorphous Multilayer Metal-Semiconductor Composites
Authors: Kadin A. M. , Burkhardt R. W. , Chen J. T. , Keem J. E. , Ovshinsky S. R. 
Published: March 2011

AbstractFollowing the earlier multilayer work of Ovshinsky and colleagues, we have fabricated thin-film samples consisting of alternating periodic layers of a transition metal (Nb, Mo, W) and a semiconducting element (Si, Ge, C) by sequential sputtering from two targets onto room-temperature substrates. The regular repeat spacing has been varied from 10 Å to more than 100 Å, with as many as several hundred layer pairs. Crystalline epitaxy was not required or even desired; many samples were largely amorphous as determined from x-ray scattering. Electrical transport measurements of superconducting properties have been carried out parallel to the layers. Samples exhibited highly anisotropic superconducting critical magnetic fields, with some values in excess of 200kG parallel to the layers. Evidence suggesting an asymmetric interface profile will be presented.
Structural Properties of Single Crystal Rare-Earth Thin Films Y and Gd Grown by Molecular Beam Epitaxy
Authors: Kwo J. , McWhan D. B. , Hong M. , Gyorgy E. M. , Feldman L. C. , Cunningham J. E. 
Published: March 2011

AbstractBy means of metal MBE technique with in-situ RHEED characterization, high-quality single crystal rare earth metal films of yttrium and gadolinium were grown as a necessary requirement for studying Gd/Y superlattices. The key step of this successful growth is the employment of the single-crystal Nb film as a buffer layer to eliminate the interaction of rare earth metals with most substrates. Structural analyses by X-ray diffraction and ion channeling show that these crystals exhibit not only complete texture of [00.1], but also narrow rocking curves both perpendicular (00.2) and parallel (10.0) to the film.
Influence of Modulation Wavelength Induced Order on the Physical Properties of Nb/Rare Earth Superlattices
Authors: Greene L. H. , Feldmann W. L. , Rowell J. M. , Batlogg B. , Hull R. , McWhan D. B. 
Published: March 2011

AbstractWe report the observation of a higher degree of preferred crystalline orientation in Nb/rare earth superlattices for modulation wavelengths in the range of 200 Å to 500 Å than that exhibited by single component films. All films and multilayers are sputter deposited onto room temperature sapphire substrates. Electronic transport measurements also show that the residual resistance ratio is higher and the room temperature resistivity is lower than for multilayers of either greater or lower periodicities. Transmission electron micrographs (TEM) showing excellent layering, grain size comparable to the layer thickness, and evidence of some degree of epitaxy are presented.
Mechanical Properties of Composition Modulated Copper-Nickel-Iron Thin Films
Authors: Jankowski A. F. , Tsakalakos T. 
Published: March 2011

AbstractThe enhanced elastic modulus effect was found in composition modulated Cu/NiFe foils. Young's modulus was measured via tensile testing on thin foils containing short-wavelength composition modulations of 1.4–10. nm. The foils, of 53% Cu -40% Ni -7% Fe composition, were produced by vapor deposition using a three-source evaporator. As compared with homogeneous foils of the same average composition, the modulated foils exhibited an appreciable increase (up to 300%) in modulus for two distinct ranges of compositon wavelength: 2.1–2.7 nm and 3.6–4.1 nm. Results of x-ray diffraction and Mossbauer spectroscopy studies suggest the concept of interfacial coherency, accommodating the lattice misfit between the composition layers, is the underlying structural feature responsible for the enhanced modulus effect.
Solid-Phase Ohmic Contacts to GaAs with TiN Diffusion Barriers
Authors: Kattelus H. P. , Tandon J. L. , Hamdi A. H. , Nicolet M-A. 
Published: March 2011

AbstractWe report on contacts to p-type GaAs formed by a GaAs/Pt/TiN/Ag system. Ohmic behavior in this system is believed to be accomplished by the solidstate reaction of Pt with GaAs. This reaction is confined by the TiN film which is thermally stable. In addition, the TiN film acts as an excellent diffusion barrier in preventing the intermixing of the top Ag layer with GaAs or Pt. Contacts formed with such controlled reaction have important implications for the stability of shallow p-n junction devices.
Self Aligned Nitridation of TiSi2: A TiN/TiSi2Contact Structure
Authors: Rosser Paul J. , Tomkins Gary J. 
Published: March 2011

AbstractTitanium nitride is an ideal barrier to silicon migration into aluminium metallisations in MOS devices. Various means by which a TiN,TiSi2 contact structure can be achieved to give low resistivity interconnects and stable contacts are outlined. It is shown that TiN/ TiSi2 contact structures self aligned to contact holes cut down to the TiSi2 can be simply achieved. Results showing the stability of the nitride film against silicon diffusion are presented.
Titanium Silicide Films Deposited by Low Pressure Chemical Vapor Deposition
Authors: Tedrow Prabha K. , Ilderem Vida , Reif R. 
Published: March 2011

AbstractSmooth titanium silicide films have been deposited using a Low Pressure Chemical Vapor Deposition (LPCVD) process. A system has been designed and built for the LPCVD of titanium silicide. It is a cold wall reactor with the wafer being heated externally by infrared lamps. Sequential deposition of polycrystalline silicon (polysilicon) and titanium silicide films, and in-situ annealing of these films, if required, can be performed in this system. A turbomolecular pump is used to provide a contaminant free environment with a base pressure of <10−7 torr. SiH4 and TiCl4 are used as silicon and titanium sources, respectively.Tithnium silicide films with resistivities ranging from 22 to 39 μΩ-cm have been obtained. At low deposition rates, these films have surface roughnesses ranging from 50 to 250 Å. From X-ray diffractometry, it was determined that the as-deposited titanium silicide films were polycrystalline, and TiSi2 was the predominant phase. Si/Ti ratios of 1.8 to 2.3 were obtained frog Rutherford Backscattering Spectroscopy (RBS). Auger analyses did not show any impurities such as oxygen, carbon or chlorine in these films.
Pre-Annealing of TiN Barriers in Al Metallization of Silicon
Authors: Sinke W. , Stout P. K. , Saris F. W. 
Published: March 2011

AbstractWe have studied the influence of a high-temperature pre-anneal on the barrier performance of TiN in Al metallization of Si. The results show that barrier failure is shifted towards a higher temperature by 20°C-40°C when the barrier is pre-annealed at 600°C-800°C. In addition, we studied the failure mechanism and found that the barrier breaks down by compound formation.
Epitaxial Phases Formation Due to Interaction Between Ni Thin Films and GaAs
Authors: Lahav A. , Eizenberg M. , Komem Y. 
Published: March 2011

AbstractSolid state reactions between Ni thin films and (100) GaAs were studied by transmission electron microscopy, X-ray diffraction, Auger electron spectroscopy and Rutherford backscattering. The hexagonal ternary phase Ni2GaAs is formed at the temperature range of 150 to 300°C with the following epitaxial relations to the substrate: (1011)//(001) and [1011]//[100]. The gradual decrease with temperature of the (1011)interplanar spacing of this phase may be related to strain relaxation associated with microtwins formation. At the temperature range of 350 to 550°C precipitation of NiAs in Ni2GaAs matrix and an increase of the twin size are observed. In this range the (1011) interplanar spacing of the ternary phase increases with temperature, possibly due to stoichiometric changes resulting from NiAs precipitation. At 600°C the ternary phase decomposes into NiGa and NiAs with average grain size of about 1 micron in lateral dimension. The cubic phase, NiGa, has simple epitaxial relations with GaAs: (001)//(001) and [010]//[010].Ni atoms are the dominant diffusing species during the ternary phase growth process as was observed in a marker experiment utilizing a very thin Ta Layer interposed between the Ni film and the substrate.
Dynamics of Laves Phase Intersections in a Concentration Gradient
Authors: Allen C. W. 
Published: March 2011

ABSTRACTIn the approximate interval 850–1150C, the Laves phase TiCr2 exhibits several composition dependent structures, ranging from two layer hexagonal (2H), denoted C14, to face-centered cubic, denoted C15, for Ti-deficient and Ti-excess material, respectively. Intermediate stacking variants such a dihexagonal (4H), denoted C36, may also exist. The Laves phase band in a Ti-Cr microdiffusion couple is examined in cross-section TEM at ambient temperature, after a 1000 C anneal. The band consists of very faulty hexagonal material, at least in part reflecting rapid shear transformation on cooling; in addition the cubic phase is present, in some instances within the same grain as the hexagonal phase. The cubic/hexagonal interfaces are approximately parallel rather than perpendicular to the bulk diffusion direction. Due to a difference in Ti and Cr fluxes, there is a gradual transformation of cubic to hexagonal by a shear mechanism. A model for the mobility of the hexagonal/cubic interface in a concentration gradient is proposed.
Influence of Phosphorous on the Kinetics of Ordering in Ni2Cr
Authors: Lehman Lawrence P. , Kosel T. H. 
Published: March 2011

ABSTRACTThe isothermal ordering kinetics of stoichiometric Ni2Cr was investigated in specimens aged at 500°C and containing 3 different phosphorous impurity concentrations; 0.004, 0.032, and 0.142 atomic percent P. In every case, higher P specimens were found to transform more rapidly than lower P content specimens, with as much as an order of magnitude difference in transformation times. Low and medium P specimens transformed via a continuous ordering process. In contrast, the highest P specimens transformed by an unusual process in which colonies of ordered domains were formed which consumed grains through the advance of an order-disorder interface. Colonies tens of microns in size were typically observed while individual ordered domains were only a few tens of nm in size.
Ordered Alloys for High Temperature Applications
Authors: Stoloff Norman S. 
Published: March 2011

ABSTRACTThis paper will provide an overview of the current status of the development of ordered alloys for high temperature structural applications. The physical and mechanical properties of ordered alloys will be reviewed with particular emphasis on aluminides and (FeNiCo)3V alloys. Alloy theory, slip systems, yielding, strain hardening, fatigue, wear resistance and processing are among the subjects to be covered. Current research programs in the U.S. and abroad will be outlined, and the kinds of scientific and application-oriented research needed in the future will be discussed.
Theories of Alloy Ordering - Overview and Forecast
Authors: Clapp Philip C. 
Published: March 2011

ABSTRACTThe task of any alloy ordering theory simply put is to predict from a small amount of experimental data the ordering phase transitions, their temperature, composition and crystal structure in some selected alloy system. Ideally, the experimental information needed would be not more than the atomic numbers of the alloy components involved. This paper attempts to assess the progress that has been made towards that objective, the various techniques that have been used to provide solutions and the probable avenues of most rapid progress in the next ten years. The major areas that will be reviewed are Ising model approaches, many body interaction approaches, computer simulation techniques, and first principle calculations. It will be argued that we are on the verge of some quite exciting breakthroughs in the field of alloy phase prediction.
Property Comparison of Melt-Spun Ribbons and Consolidated Powders of Ni3A1-B
Authors: Chang K-M , Taub A. I. , Huang S. C. 
Published: March 2011

ABSTRACTDuctile intermetallic Ni3 Al-B alloys have been processed through three rapid solidification techniques: melt spinning, gas atomization, and plasma deposition. Different thermal treatment was required for each rapidly solidified product to form samples for mechanical evaluation. Melt-spun ribbons were tested in ribbon form in the as-cast or annealed conditions, while atomized powders were tested after consolidation by hot isostatic pressing (HIP) or low pressure plasma deposition. Alloy strength, as well as tensile ductility, was found to depend strongly on processing technique, thermal treatment, sample geometry, and most importantly, alloy chemistry. Microstructural and fractographic observations indicate that grain boundary brittleness caused by material processing history plays the major role in determining the alloy's mechanical behavior.
Rapidly Solidified NiAl and FeAl
Authors: Gaydosh Darrell J. , Crimp Martin A. 
Published: March 2011

ABSTRACTMelt spinning was used to produce rapidly solidified ribbons of the B2 intermetallics NiAl and FeAl. Both Fe-40Al and Fe-45A1 possessed some bend ductility in the as spun condition. The bend ductility of Fe-40Al, Fe-45Al, and equiatomic NiAl increased with subsequent heat treatment. Heat treatment at approximately 0.85 Tm resulted in significant grain growth in equiatomic FeAl and in all of the NiAl compositions. Low bend ductility in both FeAl and NiAl generally coincided with intergranular failure, while increased bend ductility was characterized by increasing amounts of transgranular cleavage fracture.