bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fiber Optic Phase and Polarization Modulator Utilizing a Transparent Piezofilm with Indium Tin Oxide Coating
Authors: Sudarshanam V.S. , Desu S. B. , Claus R.O. 
Published: March 2011

AbstractA fiber optic phase and polarization modulator is presented in which a thin transparent piezoelectric polyvinylidene fluoride film with indium tin oxide electrode metallization is placed directly in the path of the output of a single mode fiber. Experimental characterization is presented in terms of the linearity of response, phase shifting coefficient, and frequency response for two arrangements differing in the boundary clamping conditions. Many applications to fiber optic switches, intensity modulators and demultiplexers are indicated.
Ti-Ni Phase Diagram with Applied Stress
Authors: Jardine A.Peter 
Published: March 2011

ABSTRACTThe role of stress on the phase evolution of thin-film TiNi has not been investigated and may play an important role in the phase evolution of thin film TiNi. In this paper, a preliminary set of phase diagrams for Ni-Ti at different pressures are presented relating the stability of the stoichiometric TiNi phase to the other well-documented intermetallics TiNi3 and NiTi2. It is found that for sufficient pressure of the order of a GPa, the region where NiTi (β) phase is single phase shifts towards the Ti-rich side of the diagram. The implications on the annealing of TiNi thin film is discussed.
Effect of Internal Stresses on Thermodynamics of Heterophase Structures in Epitaxial Layers
Authors: Roytburd Alexander L. 
Published: March 2011

ABSTRACTThe effect of the elastic energy of internal stresses in a system of coherent phases within an epitaxial layer is considered. The equilibrium two-phase layer has a transversely modulated structure with a modulation period dependent on the layer thickness. The phase diagrams for the phases in an epitaxial layer can differ qualitatively from standard phase diagrams, and this difference also depends on the layer thickness.
Transmission Electron Microscopy Study of CoPt(001) and FePt(001) Films Formed from Epitaxial Co/Pt and Fe/Pt Multilayers
Authors: Visokay MR.M. , Lairson BM.B. , Clemens B.B. , Sinclair R. 
Published: March 2011

ABSTRACTTransmission electron microscopy was performed on epitaxial Fe/Pt and Co/Pt [001] oriented multilayers that were sputter deposited onto single crystal [001] MgO. Films were examined as-deposited and after annealing in vacuum. Before annealing, the films had a magnetic easy axis in the plane while after annealing the easy axis was out of the plane. Perpendicular anisotropies of 8× 106 erg/cm3 and 1.9x 107 erg/cm3 were measured for the Fe/Pt and Co/Pt post-annealed films. Large magneto-optic Kerr rotations were also measured, 0.6° and 0.4° for the Fe/Pt and Co/Pt annealed films, respectively. Changes in the magnetic properties were a direct result of the transformation of the multilayer into c axis oriented FePt and CoPt intermetallic compounds upon annealing.
Atomic Transport in Irradiated Solids
Authors: Averback R.R. , Ghaly Mai , Lee Y.Y. , Zhu H. 
Published: March 2011

ABSTRACTAtomic transport in irradiated solids has been investigated in both the prompt and delayed regimes. Prompt effects are revealed on an atomic level through molecular dynamics computer simulations. It is demonstrated that for metals like gold, which have high atomic numbers and low melting points, thermal spikes play a primary role in the cascade dynamics and that concepts like melting and rapid quenching are useful descriptions. Surface effects in these metals are also discussed. For metals with higher melting points and lower atomic numbers, the cascade dynamics are determined almost exclusively by energetic collisions far above thermal energies. This is illustrated by simulations of cascades in NiAl. The effect of the high ordering energy in this intermetallic compound on the radiation-induced defect structure has also been studied.Atomic transport in the delayed regime is illustrated by two examples: an order-disorder alloy, Cu3Au, and an amorphous alloy, NiZr. The first example is used to illustrate various aspects of radiation enhanced diffusion (RED): ion beam mixing, diffusion kinetics, the effects of primary recoil spectrum, and the importance of chemical order. The second example illustrates that the basic theory of RED, which was developed to describe crystalline materials, appears to work adequately for amorphous metal alloys, suggesting that similar mechanisms may be operating. It is shown, however, that the kinetics of RED observed in amorphous alloys are not unique to point defect models.
Phase Transition and Formation of TiSi2 Codeposited on Atomically Clean Si(111).
Authors: Jeon Hyeongtag , Cho Y. S. , Kang E. Y. , Park J. W. , Nemanich R.R. 
Published: March 2011

ABSTRACTIn this study, the phase transformation and the surface and interface morphologies of TiSi2 formed on atomically clean Si substrates are investigated. 200Å Ti and 400A Si films on Si(111) have been co-deposited at elevated temperatures (400°C - 800°C) in ultrahigh vacuum. The phase transition of TiSi2 is characterized with using XRD. The results distinguish the formation of the C49 and C54 crystalline titanium silicides. The surface and interface morphologies of titanium silicides have been examined with SEM and TEM. A relatively smooth surface is observed for the C49 phase while a rough surface and interface are observed for the C54 phase. The islanding of the C54 phase becomes severe at high temperature (800°C). Islands of TiSi2 have been observed at temperatures above 700°C but no islands are observed at temperatures below 600°C. For films deposited at 400TC and 500°C, weak XRD peaks corresponding to TiSi were observed and TEM micrographs exhibited small crystalline regions of titanium silicide at the interface.
Contact Reactions at Cu / a-Ge Thin Film Couples
Authors: KÖster Uwe , Blennemann Klaus P. , Schulte Axel 
Published: March 2011

ABSTRACTThe aim of this paper is to investigate phase formation and growth kinetics in thin film Cu/a-Ge difflusion couples (150 nm Cu / 150 nm Ge) by means of cross-sectional transmission electron microscopy. During annealing in the temperature range between 100 and 180°C a highly supersaturated ζ-phase was formed first; the growth of this phase exhibits a parabolic dependence, thus indicating diffusion controlled growth; further annealing leads to a transformation into the orthorhombic ε1-phase. The first phase formed during the contact reaction probably depends on the texture and orientation of the copper layer with (111) Cu favouring the formation of the ζ-phase. When in contact with crystalline Ge the orthorhombic ε1-phase is formed directly, probably caused by a lack of driving force for the formation of the ζ-phase.Crystallization of Cu-contaminated amorphous Ge is characterized by the formation of an extremely fine-grained microstructure; higher Cu contents lead to primary crystallization of the ε1-phase (orthorhombic Cu3Ge) followed by polymorphous crystallization of the amorphous matrix into crystalline Ge. These results indicate that the early formation of a crystalline interlayer is not due to the reduced crystallization temperature of an amorphous Ge(Cu) film as formed by Cu diffusion into the amorphous Ge.
Sputter Deposition and Thermally Induced Phase Transformation of Non-BCC Chromium Thin Films
Authors: O'Keefe M. J. , Horiuchi S. , Chu J.J. , Rigsbee J.J. 
Published: March 2011

ABSTRACTThe crystal structure of sputter deposited chromium thin films on Coming 7059 glass, polytetrafluoroethylene, and cold rolled (110) oriented low carbon steel α-Fe substrates was investigated as a function of O and C incorporation into the growing Cr film. The as-deposited crystal structure of the films was found by X-ray diffraction to be either highly oriented (110) BCC α-Cr or (200) oriented A-15 δ-Cr. Chemical analysis of the films by Auger electron spectroscopy determined that the δ-Cr phaseformed when the combined O and C impurity concentration in the film was ∼15-30 at.%. At total impurity concentrations above ∼30 at.% or below ∼10 at.% standard BCC α-Cr formed. The crystal structure of the films was not influenced by the substrate material. X-ray photoelectron spectroscopy of the Cr 2pl/2-2p3/2 orbitals indicated that the dominate binding state of both the BCC α-Cr and A-15 δ-Cr films was characteristic of elemental Cr. Vacuum annealing of the A-15 δ-Cr films at 500º for one hour transformed the crystal structure into BCC α-Cr without a measurable change in chemical composition. The incorporation of O and C into the growing Cr film is believed to impurity stabilize the A-15 structure and favor its formation over the BCC structure.
Surface Modifications on Charge-Transfer Complexes Using Scanning Probe Microscopy
Authors: Yamaguchi Shoji , Valenzuela Carlos A. , Potember Richard S. 
Published: March 2011

ABSTRACTWe are exploring high density information storage systems based on organometallic materials. Silver and copper salts of tetracyanoquinodimethane (TCNQ) and its derivatives exhibit an electrical and optical field induced reversible switching phenomenon. We have demonstrated a field-induced, charge-transfer reaction driven by the electric field at the STM tip when the field generated by the STM exceeds the switching threshold of the organic charge-transfer complex. The phase transition induced by the STM tip appears as nanometer-sized domains on the metal-TCNQ and derivatives surface. We also have shown this phase transition occur by means of optical laser irradiation. This paper discusses our plans to combine our research results in optical switching with the scanning near-field optical microscope (NSOM) to develop a very high density optical memory system. In order toassess the feasibility of this, we performed a series of experiments aimed at determining the limitations of information storage using this class of organic charge transfer complexes.
Anisotropic Surface Roughness in Strain Relaxed In0.40GA0.60As on Gaas with a Step-Graded InxGA1-xAs Buffer Layer
Authors: Chang J. C. P. , Kad B. K. , Nutt S. R. , Kavanagh K. L. 
Published: March 2011

AbstractWe report the structural characterization of the 3-D relaxation morphology of In0.4Ga0.6As grown on a step-graded InxGa1-xAs buffer layer on GaAs. Scanning electron microscopy showed “grooves” spaced on the order of microns running only in the [110] direction. Each groove was observed with cross-sectional transmission electron microscopy to mark the location of a vertical low-angle tilt and/or twist boundary. The veiy rough layer morphology may be the result of island coalescence or severe surface roughness that created the grain boudnaries as the layer grew. Strain relaxation in the In0.4Ga0.6As layer was much reduced in the [101] in-plane direction. The asymmetry in residual in-plane strains in the In0.3Ga0.7AS layer and/or the increased In composition may be responsible for the development of an anisotropic surface roughness. X-ray microanalysis revealed a periodic variation in layer composition which correlated with a fine contrast modulation presumably the result of phase segregation.
Segregation and Interdiffusion of in Atoms in GaAs/InAs/GaAs Heterostructures
Authors: Kawai T. , Yonezu H. , Ogasawara Y. , Saito D. , Pak K. 
Published: March 2011

AbstractThe segregation and interdiffusion of In atoms in the GaAs/InAs/GaAs heterostructures were investigated by secondary ion mass spectroscopy. When the 1 ML thick InAs layer was grown in a layer-by-layer growth mode with no dislocations, the segregation of In atoms became marked with the increase of the growth temperature. However, the segregation was observed even at relatively low growth temperature of 400°C in molecular beam epitaxy. It was found that the segregation was markedly enhanced by dislocations near the heterointerface when the thick InAs layers were grown in a three-dimensional island growth mode. The interdiffusion of In atoms toward the growth direction occurred after thermal annealing, which could be assisted by vacancies propagating from the film surface into epilayer. It became apparent that the interdiffusion was effectively suppressed by a thin AlAs layer inserted in the GaAs cap layer.
Measurement of the Lateral Periodicity of a Quantum Dot Array by Triple Crystal Diffractometry
Authors: Jenichen B. , Ploog K. , Brandt O. 
Published: March 2011

AbstractThe lateral periodicity of an InAs quantum dot array in a GaAs matrix is measured in the differential rocking curve by triple crystal diffractometry. The quantum dot array was grown by molecular beam epitaxy of submonolayer InAs films on a terraced (001) GaAs substrate. The x-ray diffraction of the array is described in the limits of the kinematical theory. Both the changes in the scattering factor and the tetragonal deformations due to the InAs quantum dots are taken into account. The lateral periodicity of the array along [100] is 8–11nm dependent on the position of the measured region compared with an average of 10nm obtained from the miscut of the sample. In addition the vertical periodicity of the array is measured by comparison of the double crystal rocking curve with the corresponding simulation in the dynamical approximation. The vertical period of the array along [001] is 26.5nm. The coverage of the submonolayer InAs films estimated from the same measurement is 0.4. The absence of plastic relaxation is confirmed by x-ray topography.
Change of Arsenic Coverage on GaAs(001)
Authors: Nörenberg Holger , Koguchi Nobuyuki 
Published: March 2011

Abstract(2×4) and c(4×4) reconstructed GaAs(001) surfaces prepared by Molecular Beam Epitaxy (MBE) were studied by Reflection High Energy Electron Diffraction (RHEED). A method for accurate determination of the Arsenic coverage of reconstructed GaAs(001) surfaces is introduced. The time of Gallium supply to the reconstructed surface until a halo appears in the RHEED pattern is taken as measure for the Arsenic coverage. Structures between them were investigated at a substrate temperature of 200°C. The RHEED results were verified by High Resolution Scanning Electron Microscopy (HRSEM). Dependent on the surface reconstruction, Arsenic coverages between 0.76 and 1.22 monolayer (ML) were observed. Surface structures, observed during transformation between β(2×4) and c(4×4) will be discussed.
The Epitaxial Growth of Ge on Si(100) Using Te as a Surfactant
Authors: Yango X. , Cao R. , Li J. , Terry J. , Wu J. , Pianetta P. 
Published: March 2011

AbstractThe epitaxial growth of Ge on Si using Te as a surfactant has been studied with high resolution photoemission, low energy electron diffraction and cross-sectional transmission electron microscopy. The growth mode of Ge on Si changed from Stranski-Krastanov (S-K) to layer-by-layer mode when 1/4 ML Te atoms were on the surface. During the growth, Te atoms segregated to the top of the surface. If the growth temperature is too high (above ∼450°C), the Te coverage was less than that necessary to keep the layer-by-layer growth, and the growth mode of Ge on Si is still S-K.
Dynamics of Periodic Step-Bunching During Growth on Vicinal GaAs(110) Surfaces: Computer Simulations and Experiments
Authors: Krishnamurthy Mohan , Williams D. R. M. , Petroff P. M. 
Published: March 2011

AbstractMolecular beam epitaxial growth on GaAs(110) vicinal surfaces results in the formation of periodic micro-facets. We compare experimental results with computer simulations of a simple one dimensional step-flow growth model. The simulations show that preferential adatom attachment to the down step in a step array results in the destruction of step uniformity. A kinetic limitation due to adatom diffusion length along the terraces leads to stabilization of a periodic array of step-bunches. We extend our simulations to show the effects of the attachment and diffusion parameters on the dynamics of facet evolution.
Compositional Ordering in Semiconductor Alloys
Authors: Stringfellow G. B. 
Published: March 2011

AbstractCompositional ordering has been observed in a wide variety of III/V semiconductor alloys as well as in SiGe alloys. The thermodynamic driving force is now understood in terms of minimization of the microscopic strain energy of the bonds in the solid. However, the mechanism leading to the specific ordered structures formed is only now beginning to be understood. It appears to be intimately related to the physical processes occurring on the surface during epitaxial growth, specifically surface reconstruction and the attachment of atoms at steps and kinks. Thus, an improved understanding the ordering process may lead to a better understanding of the surface processes occurring during epitaxial growth from the vapor.This paper will review the current understanding of the ordering process, including discussions of the arrangement of atoms on the surface and the nature of surface steps. The emphasis will be on the use of patterned surfaces to investigate and control the ordered structures formed during organometallic vapor phase epitaxial growth of GaInP. Using photolithography and chemical etching, [110]-oriented steps are formed on the (001) GaAs substrate. The direction of motion of these steps determines the specific variant of the Cu-Pt ordered structure (with ordering on (111) planes) formed. The step density at the edge of the groove apparently determines the degree of order. Highly stepped surfaces suppress ordering or lead to small domains of a single variant. When the steps are very shallow, the large domain of the predominant variant is filled with “inclusions” of the second variant. Step edges that are oriented at nearly 160 from (001) form a {511} variant during growth. This facet is observed to grow at the expense of adjacent (001) surfaces and to produce material that is completely disordered.Growing on intentionally misoriented substrates leads to interesting structures consisting of both large, highly-ordered domains and disordered material. This allows, using cathodoluminescence(CL) imaging, a direct determination of the effect of ordering on the energy band gap. In the GaInP samples studied, the CL images show that the disordered material has a distinct emission pattern consisting of a single, sharp peak at an energy more than 100 meV higher than that observed in the adjacent ordered region.
Microanalysis of a Copper-to-Graphite Solder Bond
Authors: Intrater James B. 
Published: March 2011

AbstractSEM, x-ray microprobe and EDS analysis was performed on a uniquely prepared joint of graphite soldered to copper with 60Sn-40Pb. The presented data shows a segregation of chromium out from the metallization paste to the graphite/solder interface. Dot maps of the other elemental species were also generated.
Low temperature photoluminescence from GaAs impinged by mass-separated low-energy C+ ion beams during molecular beam epitaxy
Authors: Iida Tsutomu , Makita Yunosuke , Winter Stefan , Kimura Shinji , Tsai Yushin , Kawasumi Yoko , Fons Paul , Yamada Akimasa , Shibata Hajime , Obara Akira , Niki Shigeru , Uekusa Shin-ichiro , Tsukamoto Takeyo 
Published: March 2011

ABSTRACTC-doped GaAs films were prepared by novely a developed, combined ion beam and molecular beam method (CIBMBE) as a function of hyperthermal (30–500 eV) energies (EC+) of carbon ion (C+) beam. Ion beams of a fixed beam current density were impinged during molecular beam epitaxy growth of GaAs at substrate temperature of 550 °C. Low temperature (2 K) photoluminescence (PL) has been used to characterize the samples together with Hall effects measurements at room temperature. Through the spectral evolution of an emission denoted by [g-g]β which is a specific emission relevant to acceptor-acceptor pairs, the activation rate was confirmed to increase with increasing EC+ for EC+ lower than 170 eV. It was explicitly demonstrated that the most effective Ec+ to establish highest activation rate is located at ~170 eV. This growing activation rate was suggested to be attributed to the enhanced migration of both impinged C and host constituent atoms with increasing EC+. This surmise was supported also by Hall effect measurements which revealed the maximum net hole concentration ( |NA-ND| ) for EC+=170 eV. For EC+ higher than ~170 eV, increasing EC+ was found to induce the reduction of activation rate. It was suggested that this observation is ascribed not to the formation of C donors but to the enhanced sputtering effect of impinged C+ ions with increasing EC+.
Ultrathin Low Energy Simox for Low Cost, High Density Applications
Authors: Namavar Fereydoon , Kalkhoran N.M. , Cremins A. 
Published: March 2011

ABSTRACTSilicon-on-insulator (SOI) materials made by standard energy (150 to 200 keV) separation by implantation of oxygen (SIMOX) processes have shown great promise for meeting the needs of radiation-hard microelectronics. Since much smaller doses are required, low energy SIMOX (LES) reduces cost, improves radiation hardness, and increases the throughput of any ion implanter. The process can also produce high quality thin SIMOX structures that are of particular interest for fully depleted and submicron device structures. In this paper, we address the formation as well as the material and electrical characterization of LES wafers and compare them with standard SIMOX wafers.
Application of Ion-Plasma-Electron Technological Source T A M E K for Modification of Materials
Authors: Tolopa Alexander M. 
Published: March 2011

ABSTRACTThe same vacuum arc TAMEK source in pulse mode can generate a wide aperture S=300...2000 cm^2 ion flow of any hard electroconductive materials (metal or composites type -Tic, TiSiC, NiCrAlY, MoS, TiMoSi, WA1B, TІBNІ) both for ion implantation (Ei<200 keV, dDi=10^16 ion/cm^2/min) and for deposition dh=50...200 nm/min of the same ions. TAMEK design principle is to provide realization of ion implantation, deposition, mixing or ion beam assisted deposition of the same ions without switching off the source. TAMEK is able to create a mutual mixed (10×90 at.%) alloyed layer up to 3 μm for time in t=15 min, with structure improving (microhardness) of inner layer up to 50 μm in depth. This report presents a review of application of TAMEK source for improving the properties of surface layers of tools, construction materials, electrical contacts and electrodes, glass and other dielectric materials.
Slight Radiation Damage in Silicon for Si-Based Device Processing
Authors: Harnau A. , Schreiber H.-U. 
Published: March 2011

ABSTRACTUtilization of radiation damage by means of ion implantation to reduce parasitic capacitances in GaAs integrated circuits has become a well-established technique in the last years. Similar to GaAs, novel high-speed silicon-based devices, e.g. the Si/SiGe heterojunction bipolar transistor, are generally marked by additional short time annealing related to doping activation and a metallization annealing step in the range of 400 °C .For reproducing the external base region of such devices, Si-p+nn+ diodes were realized and investigated using I-V and C-V measurements. Slight radiation damage was achieved by Ne-implantation. Apart from enhanced leakage currents due to space charge recombination, capacitance reduction for frequencies above 50 kHz was observed even for a n-layer doping concentration as high as 1 to 2x1017 cm-3 including a 12 min 400 °C annealing step. Preliminary tests with 250 keV-Ne-ions within a dose range between 1013 and 1014 cm-2 were carried out with Schottky diodes on moderately doped n-type Si-substrate (0.3 Ωcm). For a high temperature furnace anneal at 900 °C (2 min), no capacitance reduction could be observed.Compared to previous results with Ar-implantation to obtain amorphized silicon layers, this technique allows a more easy technological handling concerning the metallization and the use of a simple photoresist pattern.