bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of W/WSIx/Si Contact Structures under Thermal Annealing for Some X Values
Authors: Ogawa S. , Yamazaki K. , Akiyama S. , Terui Y. 
Published: March 2011

ABSTRACTThermal stability of W/WSix/Si (X=1.4, 2.1, 2.5) contact structures has been characterized at annealing temperature up to 900°C. Thermal reaction in these contact structures was strongly affected by the X values of deposited WSix films. The X values were presicely controlled by a novel co-sputter deposition apparatus. After annealing at 900°C, in the samples of X=1.4 and 2.1, the W films were stably maintained. On the other hand, in the sample of X=2.5, the structure changed into the WSi2. 2/Si resulting in the disappearance of the W film. The silicidation of the W film in the sample of X=2.5 was likely due to a diffusion of Si into the W film through the precipitated region of the excess Si in the tungsten silicide film. The W/WSi2.2/Si structure can provide the electrically stable W-Si contact at annealing temperature up to 800°C.
Characterization of Bias Sputtered Aluminum Film
Authors: Homma Y. , Hinode K. , Terada T. 
Published: March 2011

ABSTRACTThe characteristics of RF bias-sputtered Al films are clarified. A negative substrate bias voltage, VDC, produced by RF biasing, strongly influences not only the planarization effect but also film characteristics such as hillock and void growth, and Ar content.Films deposited at VDc lower than -150 V. are significantly degraded due to the formation of two kinds of voids grown during annealing. One type is a blister-like voids, while the others are large and irregular. These are produced when Ar is released from the films during heat treatment. as evidenced by the fact that the amount of Ar released from the films rapidly increases when VDC is lower than -150 V.Although biasing strongly effects Al films resulting in the formation of an almost complete (111) texture. the effect degrades as VDC exceeds -200 V. Thus, Al bias sputtering requires a high resputtering rate and a VDC higher than -150 V to achieve appropriate planarization with suitable film characteristics.
Simulation of Microposit 2400-17 Resist Profiles for 0.5μm Photolithography at 248 nm
Authors: Watts R. K. , Wolf T. M. , Stillwagon L. E. , Hellman M. Y. 
Published: March 2011

ABSTRACTModel parameters have been measured to characterize the exposure and development of Microposit 2400 resist exposed by a new deep UV wafer stepper at 248 nm. Resist profiles are obtained from the model for equal line/space patterns. The observed non-vertical wall profiles are correctly predicted by the simulation. These profiles result from the strong absorption of the resist and lack of photobleaching at 248 nm.
30-nm-Scale Device Fabrication for Electron Transport Studies
Authors: Rooks M. J. , Mceuen P. , Wind S. , Prober D. E. 
Published: March 2011

ABSTRACTThe study of quantum interference effects in metallic structures requires the lithographic resolution of electron-beam lithography. Resolution and reproducibility can be greatly enhanced by the use of a multilayer resist. We have implemented a polymethylmethacrylate (PMMA) bilayer resist which avoids the typical problem of intermixing of the layers. This is accomplished by an expedient choice of the solvent, xylene, for the upper resist layer. Metal lines 30 nm wide have been fabricated. We also describe an additional deep ultraviolet (DUV) exposure method which facilitates making electrical contact to these ultrasmall structures. Quantum interference, localization effects, and the electron phase-coherence time have been studied.
Application of Scanning Tunneling Microscopy to the Study of Metals: Spectroscopy and Topography
Authors: Jaklevic R. C. , Kaiser W. J. 
Published: March 2011

ABSTRACTThe design and performance of a scanning tunneling microscope for use in the study of metal surfaces is described. The system was designed for ultra high vacuum together with standard sample cleaning and characterization techniques. The STM provides both topographic and spectroscopie information. Topographic images of well annealed Au(lll) show very smooth planes with single atomic steps. Corrugation on the (111) planes, which is expected from reconstruction models for this surface, is not seen. Other areas show monatomic steps in the form of an ordered array with a period corresponding to that derived from previous studies. A possible alternative reconstruction mechanism is suggested by these STM data. On the same surface are steeper sloped regions with multiple steps of equal height with wide facets. Spectroscopie first derivative data for Au and Pd show peaks which correspond to surface and bulk electronic states, for both filled and unfilled cases. The energy values of these states are compared directly with the results of other experimental methods. The use of combined topographic and spectroscopie mode for metals is anticipated.
Angular Dependent Critical Fields in NbTi-Ge Superlattices in the Weakly Localized Regime
Authors: Jin Ben Y. , Ketterson J. B. , Hilliard J. E. , McNiff E. J. , Foner S. , Schuller Ivan K. 
Published: March 2011

ABSTRACTThe angular dependence of the upper critical fields, Hc(θ) for a set of NbTi-Ge superlattices were studied at various temperatures. The behavior of Hc(θ) at lower temperatures deviates from the Tinkham expression which is expected to be valid only in the Ginzberg-Landau regime close to Tc. We examine a model for calculating Hc(θ) involving the lowest eigenvalue of the gauge invariant diffusion equation (subject to boundary conditions appropriate to a slab) in the de Gennes expression for the upper critical field of a dirty superconductor at all temperatures. The disorder related localization and interaction effects as well, as the paramagnetic limiting effect, are also considered.
High Resolution Transmission Electron Microscopy of PbTe/Pb1-zEuxSeyTe1-v, Heterostructures.
Authors: Salamanca-Young L. , Partin D. L. , Heremans J. , Dresselhaus E. M. 
Published: March 2011

ABSTRACTHigh resolution transmission electron microscopy has been used to study the structure of PbTe/Pb1-zEuxSeyTe1-v semiconductor superlattices and heterojunctions grown on BaF2 substrates by molecular beam epitaxy. The objective of this study is to analyze the interface sharpness and the structural perfection of the samples at their interfaces. In the PbTe/Pb1-zEuxSeyTe1-v system, we have observed misfit dislocations and even amorphous regions for high Eu concentrations. We have also observed two directions of growth of the superlattice film. The interface appears to be sharp to approximately three monolayers. A model for the superlattice structure is suggested and used to obtain simulated images using computing methods. The simulated images are compared with those obtained experimentally.
Kinetics and Thermal Stability of Ni/Zr Multilayer Thin-Film Diffusion Couple during a Solid State Amorphization Reaction
Authors: Meng W. J. , Cotts E. J. , Johnson W. L. , Keck W. M. 
Published: March 2011

ABSTRACTDifferential scanning calorimetry and X-ray diffraction have been utilized to monitor the solid state amorphization reaction in crystalline Ni/Zr multilayers. Enthalpy of mixing of amorphous NiZr alloys has been measured. Kinetics of amorphous phase formation and thermal stability have been discussed in some detail.
Picosecond Dynamics of Photoexcitations in Amorphous Multilayer Structures
Authors: Grahn H. T. , Vardeny Z. , Maris H. J. , Tauc J. , Abeles B. 
Published: March 2011

ABSTRACTWe report on measurements of ultrafast relaxation processes in transmission and reflection in amorphous multilayer structures consisting of a-Si:H, a-SiNx:H, a-SiOx:H, and a-Ge:H. The decays recorded in transmission in the a-Si:H/a-SiNx:H and a-Si:H/a-SiOx:H multilayers depend strongly on the silicon sublayer thickness and are interpreted in terms of carrier transport to and trapping at interfacial defects. In the a-Si:H/a-Ge:H multilayers we observe oscillations in reflectivity due to standing acoustic waves with a frequency that depends on the repeat distance of the multilayer.
Two-Dimensional Excitons in A Strongly Localized Regime in CdTe/ZnTe Superlattices
Authors: Hefetz Y. , Lee D. , Nurmikko A. V. , Sivananthan S. , Chu X. , Faurie J.-P. 
Published: March 2011

ABSTRACTTime-resolved spectroscopy of the recombining exciton state in a highly strained II-VI semiconductor superlattice CdTe/ZnTe reveals strong localization effects at low lattice temperatures. Such phenomena originate naturally from small deviations in structural perfection on a monolayer scale in a strained superlattice with a small valence band offset. The quasi-2D aspect enhances the localization phenomena further.
Forkation and Oxidation of Titanium Silicide
Authors: Huang Tzuen-Luh , Lee Shuit-Tong 
Published: March 2011

ABSTRACTRefractory metal suicides have been used widely in VLSI fabrication, owing to their low resistivity, high-temperature compatibility, and oxidiz-ability. In this work, we have studied the titanium suicide formation, using a rapid thermal processor (RTP). Isothermal and isochronal sintering experiments were carried out to determine the appropriate process steps. The selective etch of the unreacted Ti was characterized. The sintered films were characterized by four-point probe, X-ray diffraction, and Auger electron spectroscopy. We also studied the oxidation at 800–1000°C of Ti suicide formed by sintering Ti and polycrystalline silicon using a RTP in N2 ambient. The oxidation results of Ti suicide formed using RTP in N2 ambient are compared with those formed using furnace sintering in vacuum/argon ambient and those deposited by cosputtering.
Coupled Two Dimensional Electron Gas Structures in the G1−xAlxAs/GaAs System
Authors: Christou A. , Hatsopoulos Z. , Bacalis N. , Papanicholaou N. , Ginoudi A. 
Published: March 2011

ABSTRACTTwo 2-dimensional electron gas (DEG) regions coupled either by a superlattice, an undoped GaAs layer, or the combination of a tunneling barrier with a superlattice have been investigated by studying (a) non-ohmic conduction, (b) field effect characteristics parallel to the 2DEG channels and (c) negative differential resistance (NDR) for conduction perpendicular to the quantum wells. It is shown that coupling is optimized when the separation region is a superlattice. Tunneling through superlattice mini-bands can enhance field effect transistor transconductance.
Structural Studies of Nickel Films and their Interface with Sapphire Substrates
Authors: Sparks C. J. , Hasaka M. , Easton D. S. , Baik S. , Habenschuss T. , Ice G. E. 
Published: March 2011

ABSTRACTThe perfection of epitaxial nickel films grown on the (00.ℓ) or basal plane of heated sapphire (A1203) single crystals were studied with X-ray diffraction techniques. Nickel films approximately 700 Å thick formed by vapor deposition increased in perfection as the temperature of the sapphire approached 1400°C. Although the nickel atom distances are 10.3% smaller than those of the closed-packed direction in sapphire, the strain was accommodated at the interface rather than being distributed through the thickness of the nickel film. Diffuse rods of X-ray scattering which are associated with diffraction from the interface gave information about the nature of the roughness at the interface.
Aluminum-Titanium Multilayer Interconnect With Titanium Diffusion Barrier
Authors: Tong-Lee S. , Huang Tzuen-Luh , Van Den Hove L. , Nichols D. N. 
Published: March 2011

ABSTRACTThe metallurgical reaction at 450°C in forming gas ambient between the Ti diffusion barrier and Al, causing the contact degradation in the Al (1% Si)-Ti multilayer interconnects has been studied. The Ti-Al reaction is reduced by preheating the Ti layer in N2 using rapid thermal processing (RTP) at 2.500°C. The curtailed reaction is attributed to the thin surface titanium oxynitride layer. It was found that a 1000-Å Ti layer inserted between the multilayer and Si is effective as a sacrificial diffusion barrier against contact degradation, but 500-Å Ti is not. RTP of the thin Ti film rendered it effective as a diffusion barrier.
Epitaxial Film Growth of Single Crystal Ce/V Prepared by Molecular-Beam Epitaxy
Authors: Homma Hitoshi , Yang Kai-Y. , Schuller Ivan K. 
Published: March 2011

ABSTRACTThe growth of epitaxial films of cerium (Ce)/vanadium (V)/on single crystal sapphires (α-A1203) was studied by in-situ reflection high energy electron diffraction and x-ray scattering. For the first time Ce(111) single crystal film was grown on V(110)/α-A12O3 (1120) in the Frank-van der Merwe mode. A new epitaxial orientation, different from the well known Nishiyama-Wasserman or Kurdjumov-Sachs orientations is found in the present study. Subsequent V(110) layers grow epitaxially with three equivalent domains.
Anneal Induced Changes in Amorphous Semiconductor Multilayers
Authors: Gonzalez-Hernandez J. , Allred D. D. , Nguyen O. V. 
Published: March 2011

ABSTRACTWe have prepared, heat treated and characterized various amorphous semiconductor periodic multilayers and ultrathin films. These were prepared by several vapor deposition techniques at substrate temperatures ranging from 25°C to 300°C and possessed periodicities from 22 to 400Å. Films were subjected to isochronal thermal treatments at progressively higher temperatures. Two effects were observed: enhanced diffusion and retarded crystallization. Interdiffusion, at rates which are many orders of magnitude higher than those anticipated from crystalline data, was observed in a-Si/a-Ge multilayers. Crystallization of germanium, the more readily crystallized member of the couple, is retarded; the extent depends on the thickness of the layer. The thinner the layer, the greater the retardation. Where intermixing is thermodynamically unfavorable as in a-Si/a-SiNx or a-Ge/a-SiNx multilayers, and ultrathin germanium layers on SiO2, interdiffusion does not occur, however, crystallization of silicon or germanium is again substantially retarded.
Effect of Heating on the Structure of Au/GaAS Encapsulated with SiO2
Authors: Zeng X.-F. , Chung D. D. L. , Lakhani Amir 
Published: March 2011

ABSTRACTThe structural effects of heating 1500 Å Au/GaAs (001) encapsulated with 2000 Å of SiO2 were examined by scanning electron microscopy and x-ray diffraction. It was observed that SiO2/Au/GaAs (capped) in vacuum up to 500°C remained shiny and gold in color, whereas similar heating of Au/GaAs (uncapped) caused a change of color from shiny gold to dull silver. Furthermore, mass spectroscopy showed that the amount of arsenic vapor evolved was much less for the capped sample. However, x-ray diffraction showed that Au7Ga2 formed abundantly in both types of samples after heating at 500°C, though the epitaxial relationship was AuyGa2 (001) // GaAs (001) for capped and Au7Ga2 (100) // GaAs (001) for uncapped. SEM revealed gold-rich aligned rectangular protrusions on the surfaces of SiO2/Au/GaAs as well as Au/GaAs after heating at 500°C, though the average length of these rectangles was 1.5 μm for the capped sample and 6.7 μm for the uncapped sample. Moreover, new morphological features absent in Au/GaAs were observed in SiO2/Au/GaAs. These features are a gold-rich maze with a line width of 6 Åm and gold-rich protruded lines with a line width of 9 Åm. The gold-rich protruded lines were formed by the growth and joining together of some gold-rich aligned rectangular protrusions. The gold-rich maze was observed in SiO2/Au/GaAs after heating in vacuum, but was not observed in SiO2/Au/GaAs after heating in nitrogen.
Chemical Vapor Deposition of Silicon Films Using Hexachlorodisilane
Authors: Taylor R. C. , Scott B. A. , Lin S.-T. , LeGoues F. , Tsang J. C. 
Published: March 2011

ABSTRACTThe use of hexachlorodisilane (Si2Cl6) as an alternative to silane for growth of polycrystalline silicon films has been investigated. Films were grown at atmospheric pressure in both hydrogen and nitrogen carrier gases over a temperature range of 450–900°C. Deposition rate data indicate the existence of two growth regimes at high and low temperatures and in the presence or absence of hydrogen. The change from amorphous to polycrystalline growth takes place at 600–650°C. At 600°C deposited films are amorphous but crystallize during the growth process. The chlorine content of high-temperature films was found to be less than 0.01 at.%.
Cross-Section Transmission Electron Microscope Study of Ni/Au/Ge/Au Ohmic Contact to Gallium Arsenide
Authors: Kim Taeil , Chung D. D. L. , Mahajan S. 
Published: March 2011

ABSTRACTThe interfacial structures resulting from the metallurgical reactions between a Ni/Au/Ge/Au film and (100) GaAs substrate were studied by cross-section TEM. Annealing at 300 – 350°C causes a complicated solid-solid phase reaction, resulting in the multilayer structure of Ni2Ge/Au7Ga2/NiAs/Au7Ga,/GaAs. The contact shows non-ohmic character, since most of the doping element Ge is trapped in the surface Ni2Ge layer When the contact is annealed at above 400°C. the layered structure is destroyed because one of the phases (Au-Ga) becomes liquid but other phases (Ni-Ge, Ni-As) remain solid Ge, which is captured in the surface layer, diffuses out of the Ni2Ge phase into the contact/GaAs interface through the Au-rich melt. Above this temperature, a Ge-doped n+ region is probably formed at the NiAs/GaAs interface and the contact becomes ohmic. With increasing annealing temperature, continuous grain growth of NiAs is found to occur and the NiAs/GaAs interface area increases. Thus the ohmic behavior of Au-Ge-Ni on n-GaAs can be explained by the low barrier height of the NiAs/GaAs interface and the formation of Ge-doped n+ region under the NiAs phase.
Liquid Phase Epitaxial Growth of Fe-Doped Semi-Insulating Inp and Ternary Alloys
Authors: Isozumi S. , Tanahashi T. , Kondo M. , Sugawara M. , Yamaguchi A. , Nakajima K. 
Published: March 2011

ABSTRACTFe-doped semi-insul ati ng layers of InP, In0.48A10.52As,and In0.49Ga0.51P have been grown by liquid phase epitaxy for the first time. Behaviors of Fe doping in these materials have been well explained by the solubility of Fe in the growth solution and the temperature dependent distribution coefficients of Fe. It has been found that the distribution coefficients of Fe in the ternary alloys are much greater than those in InP.
Mechanical Property and Microstructure of TZP and TZP/Al2O3 Composites
Authors: Tsukuma Koji , Takahata Tsutomu 
Published: March 2011

ABSTRACTThere are various types of microstructure in the TZP materials and their composite materials. The fine-grained microstructure is well-known as the basic microstructural type of TZP materials. Y-TZP and Ce-TZP belong to this group. The large-grained microstructure can exist in the TZP consisting of the tetragonal phase with low metastability, that is, Y-TZP doped with TiO2 and Ce-TZP containing a high CeO2 content. The composite material between Y-TZP and β-lanthanum alumina possessed a unique microstructure including elongated grains of β-Al2O3 type structure. This study provides a summary of the mechanical properties of these TZP and β-Al2O3 type structure composite materials, and points out how the mechanical behavior depends on the microstructural features.
Effect of Changes in Grain Boundary Toughness on the Strength of Alumina
Authors: Cook Robert F. 
Published: March 2011

ABSTRACTIndentation/strength data on a series of Ca-doped aluminas are presented, revealing considerable microstructural influence and increasing fracture resistance during crack propagation. The source of the increasing resistance is considered in terms of a restraining zone of grain-localized ligamentary bridges behind the crack tip. A simple fracture mechanics model is developed to characterize the effect of the restraining ligaments, which also allows the steady state toughness, applicable to large cracks, and the intrinsic strength, applicable to small cracks, to be predicted. The segregation of Ca to the grain boundaries is shown to correlate with decreases in grain boundary toughness and increases in toughness in the large crack limit. These latter two combined effects lead to decreases in intrinsic strength with increasing steady state toughness.
Comparison of Matrix Variation in Nicalon (Sic) Fiber Reinforced Composites
Authors: Johnson W. L. , Brasfield R. G. 
Published: March 2011

ABSTRACTThe high-temperature behavior of NICALON fabric is discussed. Three fabric reinforced composites are described that use NICALON fabric to take advantage of its oxidation and erosion resistance. The matrix materials used were phenolic resin, pyrolytic carbon and beta-silicon carbide. Each composite was subjected to an erosive environment at 2755 K. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and laser Raman microprobe analysis (LRMA) were used to characterize the raw materials, the unfired composites, and the erosion tested composites. These analyses concentrated on the fiber/matrix interaction and the effect of erosion on each component of the composite.
Texture on Ground, Fractured, and Aged Y-TZP Surfaces
Authors: Reidinger Franz , Whalen Philip J. 
Published: March 2011

ABSTRACTThe phase composition of Y-TZP surfaces has been shown to vary greatly depending on the thermo-mechanical history of the surface. The orientation of these different phases in the surface region is not always random. There is speculation that the alignment of the tetragonal phase before fracturing may play a part in increasing the toughness of these materials. This article deals with an X-ray diffraction analysis of various Y-TZP surfaces with special emphasis on the texture of the different phases. Surfaces which have been ground (and polished), fractured, and aged (200°C) have been examined. In all cases, the monoclinic component that was formed was strongly oriented. The tetragonal phase may or may not be oriented depending on surface treatment. Annealing above the monoclinic-tetragonal transition temperature had little effect on the tetragonal orientation in most cases. Samples fractured at 1000°C have no unusual orientation on the fracture faces.
Deflection-Toughened Corundum-Rutile Composites
Authors: Hori Saburo , Kaji Hisatsugu , Yoshimura Masahiro , Sōmiya Shigeyuki 
Published: March 2011

ABSTRACTDense corundum-rutile composites containing plate-shaped corundum particles were prepared from the CVD Al2O3-TiO2 powders by adding a small amount of sodium and sintering below ˜1280°C. The fracture toughness increased up to 6.5 Mpa · ✓m and the increment of toughness was proportional to the volume % of plate-shaped corundum particles. The importance of tilt deflection and crack bowing rather than the twist deflection was suggested in this system.
Deformation Behavior of SiC Whisker Reinforced Si3N4
Authors: Nixon R. D. , Chevacharoenkul S. , Huckabee M. L. , Buljan S. T. , Davis R. F. 
Published: March 2011

ABSTRACTConstant compressive stress creep exp∼riments in jhe temperature and stress ranges of 1420K – 1570K and 50 MN/m2 –350 MN/m2 have been conducted on hot pressed unreinforced Si3N4 containing the densification aids of 6 wt% Y2O3 and 1.5 wt% Al2O3 and on a similarly prepared composite material reinforced with 20 vol% SiC whiskers. Steady-state creep data obtained on these materials in a N2 atmosphere gave stress exponent values of 1.2 – 1.6 and 0.4 – 1.6 for the unreinforced Si3N4 and the composite, respectively. A break in the steady-state creep rate vs. log stress observed only in the composite occurred at approximately 250 MN/m2 at the temperatures of 1520K and 1570K. This information coupled with the results of electron microscopy indicate that the temperature as well as the extensive crystallization (or lack of it) of the amorphous grain boundary phase are the principal factors controlling the deformation rate at a given stress within the limits of the small total strains achieved in this research.