bluuebunny/crossref_metadata_2025_split huggingface dataset:
Behavior of Uranium Dioxide: Chemistry and Catalysis in the UO2-water System
Authors: Devoy Jérôme , Haschke John , Cui Daqing , Spahiu Kastriot 
Published: April 2011

ABSTRACTInteractions during extended exposure of UO2 to 2:1 H2+O2 mixtures at room temperature and 0.13 bar pressure are investigated in an effort to describe chemical and kinetic behavior of spent fuel following contact with groundwater. Oxidation of UO2 to UO2+x by O2 occurs initially when oxide is directly exposed to the gas mixture or submerged in water, but immersion is accompanied by a 25-fold reduction in the rate. The initial rate is proportional to [O2]2 for gasphase oxidation and to [O2]1.5 for the submerged oxidation. Continued measurement during direct oxide-gas contact indicates sequential reactions in which the UO2+x product is further oxidized by H2O and ultimately reacts with H2 to form an oxide hydride.
Evaluation of Corrosion Processes Affecting the Performance of Alloy 22 as a Proposed Waste Package Material
Authors: Cragnolino Gustavo A. , Dunn Darrell S. , Pan Yi-Ming 
Published: April 2011

ABSTRACTThis paper presents recent work on evaluating localized corrosion and stress corrosion cracking, two corrosion processes that are important to the long-term performance of Alloy 22 (58Ni-22Cr-13Mo-3W-4Fe). This alloy is the material preferred by the U.S. Department of Energy (DOE) for the outer container of the waste package to be used in the proposed high-level radioactive waste repository at Yucca Mountain, Nevada. It was found that both welded and thermally aged materials are more susceptible to localized corrosion in chloride solutions at temperatures above 60 EC than the mill-annealed material. This observation suggests that welding and certain post-welding operations may decrease the estimated life of the waste packages. However, no stress corrosion crack growth was observed in concentrated chloride solutions and simulated, concentrated groundwater at 95 EC when precracked compact tension specimens were tested under both constant and cycling loading.
The Impact of Cementitious Materials on the Corrosion of Copper Canisters
Authors: King Fraser , Werme Lars 
Published: April 2011

ABSTRACTCementitious materials could be used in an underground repository as seals, bulkheads, grouts, or to provide a smooth surface for vehicles in the rooms and tunnels during repository construction. There is a possibility that an alkaline plume could be released from the cementitious materials in the repository and impact the corrosion behaviour of the canisters. The available literature information on the corrosion and electrochemical behaviour of copper in alkaline environments has been reviewed. Alkaline conditions promote passivation of the canister, whereas the presence of chloride groundwaters supports general dissolution. Localized corrosion due to an alkaline plume is considered to be unlikely because the protectiveness of the passive film (as measured by the difference between the corrosion and pitting potentials) increases with increasing pH.
The Use of Natural Uranium Decay Series Studies in Support of Understanding Redox Conditions at Potential Radioactive Waste Disposal Sites
Authors: Tullborg Eva-Lena , Smellie John A. T. , MacKenzie Angus B. 
Published: April 2011

ABSTRACTUranium is a redox-sensitive element which occurs naturally in the bedrock and groundwaters in Fennoscandia, and can be used, in conjunction with its decay series descendants, to indicate groundwater redox conditions. Not only can contemporary conditions be characterised, but evidence of past changes (e.g. during the last glaciation some 10 ka ago) can be preserved in minerals which coat the fracture walls along groundwater pathways. Uranium decay series data for groundwaters and solid fracture phases from the site of the Äspö Hard Rock Laboratory and its near vicinity are presented and discussed in the context of redox conditions.
Gate Overlapped Lightly Doped Drain Poly-Si TFTs Employing 45° Tilt Implant For Source and Drain
Authors: Lee Jae-Hoon , Shin Moon-Young , Shin Heesun , Nam Woo-Jin , Han Min-Koo 
Published: April 2011

ABSTRACTWe propose a short channel gate overlapped lightly doped drain (GOLDD) poly-Si TFT employing 45° tilt implant for source and drain (S/D) regions without any additional ion doping or mask. Oblique-incident ELA activation is performed to activate both n+ S/D and n- LDD regions as well as cure junction defects. The proposed poly-Si TFT can suppress the anomalous leakage current, and exhibit the better reliability against the hot-carrier stress.
Characterization of the Bulk Recombination in Hydrogenated Amorphous Silicon Solar Cells
Authors: Deng J. , Pearce J.M. , Vlahos V. , Collins R.W. , Wronski C.R. 
Published: April 2011

ABSTRACTDark forward bias current, JD-V, characteristics offer a probe for characterizing carrier recombination and the defect states in the intrinsic layers of hydrogenated amorphous silicon (a-Si:H) solar cells. Detailed studies were carried out on such characteristics for the cells with optimized p/i interfaces and high quality i-layers in which the current transport is bulk recombination dominated. It was found that the diode quality factor n is not a constant with bias voltages as has been generally considered. Instead, it can be best described through the bias dependent differential diode quality factors, n(V) = [kT/q]−1[d(lnJD)/dV]−1, whose magnitude and shape reflect the gap state distribution in the corresponding bulk i-layers. The n(V) characteristics obtained on cell structures with both hydrogen diluted and undiluted i-layers have been utilized in characterizing the differences in the distribution of defect states in the two i-layers both in annealed state as well as after creating light induced defects. In the characterization of the Staebler-Wronski Effect (SWE) using JD-V characteristics, a newphenomenon is observed – relaxation of light induced defect states created by 1 sun illumination at 25°C, which is also found in the follow-on studies on the photo-conductivities of corresponding thin films.
Microcrystalline Silicon Solar Cell Deposited Using Modified Very-High-Frequency Glow Discharge and Its Application in Multi-junction Structures
Authors: Yue Guozhen , Yan Baojie , Owens Jessica M. , Yang Jeffrey , Guha Subhendu 
Published: April 2011

ABSTRACTWe have used the modified very-high-frequency glow discharge technique to deposit hydrogenated microcrystalline silicon (m c-Si:H) solar cells at high rates for use as the bottom cell in a multi-junction structure. We have investigated c-Si:H single-junction, a-Si:H/ c-Si:H double-junction, and a-Si:H/a-SiGe:H/m c-Si:H triple-junction solar cells and achieved initial active area efficiencies of 7.7%, 12.5%, and 12.4%, respectively. Issues related to improving material properties and device structures are addressed. By taking advantage of a lower degradation in m c-Si:H than a-Si:H and a-SiGe:H alloys, we have minimized the light induced effect in multi-junction structures by designing a bottom-cell-limited current mismatching. As a result, we have obtained a stable active-area cell efficiency of 11.2% with an a-Si:H/a-SiGe:H/μ c-Si:H triple-junction structure.
Deposition of Optimal a-Si:H and a-SiGe:H by HWCVD Using the Same Filament Temperature and Substrate Temperature
Authors: Mahan A.H. , Xu Y. , Gedvilas L.M. 
Published: April 2011

ABSTRACTThe incorporation of high Ge content a-SiGe:H into a low bandgap solar cell device commonly involves the use of bandgap (Ge) profiling. In previous work using the hot wire (HWCVD) technique, device quality low bandgap (ETauc= 1.25eV) a-SiGe:H films were deposited at low Tsub(∼200-250°C) filament operating at Tfil∼ 1750-1800°C. However, higher bandgap films containing little or no Ge and deposited under the same low temperature (Tsub,Tfil) conditions were of decidedly inferior quality to those deposited using higher temperatures (Tfil∼2000°C,Tsub∼360°C) solar cell with an efficiency ∼ 5.85% was fabricated using these materials, it was clear that our best ‘end point’ materials alloying at this low Tfilseverely limits film reproducibility and filament lifetime. This work explores deposition of device quality low bandgap a-SiGe:H and (high bandgap) a-Si:H, both at the same low Tsub, using a tantalum (Ta) filament operating at low Tfil. Film material properties are presented.
Extension of the Constant Photocurrent Method to Determine Densities of Occupied and Unoccupied Localised States
Authors: Main Charlie , Reynolds Steve , Zrinŝcak Ivica , Merazga Amar 
Published: April 2011

ABSTRACTThis paper examines the use of Constant Photocurrent (CPM) measurements on thin film semiconductors, employing steady (DC) and modulated (AC) sub-gap illumination, to determine the density of localised states (DOS) in the bandgap. AC and DC measurements often result in different apparent absorption spectra. It is demonstrated that it is possible not only to extract information from the respective 'absorption' spectra, on the DOS below the Fermi level - i.e. occupied states, but also on the density of unoccupied states above the Fermi level. The ability to discriminate between these two groups of states by using DC and AC modulated sub-gap light arises from the frequency dependence of the different excitation pathways by which free electrons can be produced. AC modulated excitation will reveal absorption associated with transitions from occupied states into the conduction band, while DC excitation will include transitions from the valence band into unoccupied defect states, followed by slow thermal emission to the conduction band. We examine the temperature dependence of the CPM spectra and present a simple analysis of the DC and AC absorption spectra which allows the two regions of the DOS, above and below the Fermi level, to be determined.
Hydrogen Injection in ETP Plasma Jet for Fast-Deposition of High-Quality a-Si:H
Authors: Petit A.M.H.N. , Swaaij R.A.C.M.M. van , Sanden M.C.M. van de 
Published: April 2011

ABSTRACTWe have used a cascaded-arc expanding thermal plasma (ETP) to produce thin films of amorphous silicon at high growth rates (> 3 nm/s). Here, we present a study of the effect on material properties of hydrogen injection in the nozzle, i.e., at the exit of the arc where the plasma expands into the reactor chamber. The advantage of using extra H2 in the nozzle is that the plasma chemistry and pressure in the arc remain unchanged, whilst higher growth rates and a material with low defect densities can be obtained.We observe that with an increase of substrate temperature the growth rate decreases due to densification of the material. This densification is accompanied by a reduction of the hydrogen content and of the microstructure parameter. Further we observe that hydrogen content decreases with higher growth rate. A strong relation is found between the light conductivity and the microstructure parameter indicating a large void fraction in samples grown at low temperature.We have been able to grow a-Si:H material, with H2 in the nozzle, at 350°C and 3 nm/s with a light conductivity of 1.2 × 10−5 Ω1cm−1, which can be suitable for solar-cell application.
Recessed and Epitaxially Regrown SiGe(B) Source/Drain Junctions with Ni salicide contacts
Authors: Isheden Christian , Hellström Per-Erik , Radamson Henry H. , Östling Mikael 
Published: April 2011

ABSTRACTIntegration issues concerning recessed epitaxial SiGe(B) source/drain junctions formed by selective Si etching followed by selective epitaxial growth of in situ heavily B-doped Si1−xGex are presented. The concept is beneficial compared to conventional ion implanted junctions, since dopant activation above the solid solubility in Si can be obtained. When integrated in the PMOS process flow, the resulting Si1−xGex layer is very rough. Several possible causes for low quality epitaxy are discussed and improvements are proposed. It is suggested that the dopant type and/or concentration in the silicon substrate can have an effect on the process.
On the “Life” of {113} Defects
Authors: Cherkashin N. , Calvo P. , Cristiano F. , Mauduit B. de , Claverie A. 
Published: April 2011

ABSTRACTIn this paper, we present a new set of conditions which can be used for imaging {113} defects. These conditions have the advantage of allowing the simultaneous imaging of all the variants of the defects. They can be used for building up accurate size-histograms or for checking the occurrence of the different variants. Making use of these conditions, we revisit the well- known experiments of the dissolution of the {113} defects and pinpoint some specific features of defect evolution during annealing which were not evidenced in previous works. The new results are discussed and are definitely found to be well-explained in the framework of a non- conservative Ostwald ripening.
Strain Relaxation of Ion-implanted Strained Silicon on Relaxed SiGe
Authors: Crosby R. T. , Jones K. S. , Law M. E. , Saavedra A. F. , Hansen J. L. , Larsen A. N. , Liu J. 
Published: April 2011

ABSTRACTThe relaxation processes of strained silicon films on silicon-rich relaxed SiGe alloys have been studied. Experimental structures were generated via Molecular Beam Epitaxial (MBE) growth techniques and contain a strained silicon capping layer of approximately 50 nm. The relaxed SiGe alloy compositions range from 0 to 30 atomic% germanium. Samples received two distinct types of silicon implants. A 12 keV Si+ implant at a dose of 1×1015 atoms/cm2 was used to generate an amorphous layer strictly confined within the strained Si cap. An alternate 60 keV Si+ implant at a dose of 1×1015 atoms/cm2 was employed to create a continuous amorphous layer extending from the sample surface to a position 50 nm into the bulk SiGe material. The strain relaxation and regrowth processes are quantified through High Resolution X-Ray Diffraction (HRXRD) rocking curves and Cross-sectional Transmission Electron Microscopy (XTEM). The role of injected silicon interstitials upon the strain relaxation processes at the Si/SiGe interface after annealing at 600°C is investigated.
Ni Silicide Morphology On Small Features
Authors: Chamirian Oxana , Lauwers Anne , Kittl Jorge A. , Dal Mark Van , Potter Muriel De , Vrancken Christa , Lindsay Richard , Maex Karen 
Published: April 2011

ABCTRACTSilicidation of small features of various geometries and sizes using Ni-silicide was studied. Effects of dopants, surface preparation and silicidation parameters on silicide morphology were investigated. It was found that Ni silicide thickness and quality of the silicide/silicon interface (presence of NiSi2 pyramids) are dependent on the area dimensions and geometry. NiSi formed on narrow lines is thicker compared to wide areas. We found that pyramids of epitaxial NiSi2 protruding into the Si substrate are formed during the silicidation of undoped, boron-doped and BF2-doped active areas. The presence of pyramids was not observed on As-doped silicon. Rough interface due to the pyramids could be the reason for a more pronounced linewidth dependence of leakage current in the case of p+/n diodes. A higher density of pyramids was found on narrow lines (below 0.2μm) and particularly islands structures. No pyramids were found when a Ge preamorphisation implant was used.
Effect of Ge-rich Si1−zGez Segregation on the Morphological Stability of NiSi1−uGeu Film Formed on Strained (001) Si0.8Ge0.2 Epilayer
Authors: Yao H.B. , Chi D.Z. , Tripathy S. , Chow S.Y. , Wang W.D. , Chua S. J. , Sun H.P. , Pan X.Q. 
Published: April 2011

ABSTRACTThe germanosilicidation of Ni on strained (001) Si0.8Ge0.2, particularly Ge segregation, grain boundary grooving, and surface morphology, during rapid thermal annealing (RTA) was studied. High-resolution cross-sectional transmission electron microscopy (HRXTEM) suggested that Ge-rich Si1−zGez segregation takes place preferentially at the germanosilicide/Si1−xGex interface, more specifically at the triple junctions between two adjacent NiSi1−uGeu grains and the underlying epi Si1−xGex, and it is accompanied with thermal grooving process. The segregation process accelerates the thermal grooving of NiSi1−uGeu grain boundaries at the interface. The segregation-accelerated grain boundary grooving has significant effect on the surface morphology of NiSi1−uGeu films in Ni-SiGe system.
Technology Computer Aided Design of Ultra-shallow Junctions in Si Devices Formed by Laser Annealing Processes
Authors: Magna Antonino La , Alippi Paola , Privitera Vittorio , Fortunato Guglielmo , Camalleri Marco , Svensson Bengt 
Published: April 2011

ABSTRACTThe simulation of laser annealing, applied to the formation of ultra-shallow junctions in Si, is discussed. Our effort is developing tools capable to aid the process integration issue. The numerical approach deals with a double problem: 1) the interaction between the irradiated transistor structure and the laser light, 2) the non-equilibrium evolution of the thermal field, molten regions and dopant density. Here we present a complete methodology: the calculated heat source distribution, induced by the irradiation, is used as input of a phase-field approach for the simulation of the thermal phase and impurity fields. We solved numerically the phase field equations in two dimensional structures, considering as an initial status the generic material modification due to an ion implant process. We present various simulation results obtained in MOS structures with different geometry. With the support of the simulation results we discuss the problematic and the perspectives of the excimer laser annealing process application in the fabrication of MOS devices.
The Effect of Fluorine Implantation on Boron Diffusion in Metastable Si0.86 Ge0.14
Authors: El Mubarek Huda A. W. A. , Wang Yun , Bonar Janet M. , Hemment Peter , Ashburn Peter 
Published: April 2011

ABSTRACTThis paper investigates the effect of varying F+ implantation energy on boron thermal diffusion and boron transient enhanced diffusion (TED) in metastable Si0.86Ge0.14 by characterising the diffusion of a boron marker layer in samples with and without P+ and F+ implants. The effect of two F+ implantation energies (185keV and 42keV) was studied at two anneal temperatures 950°C and 1025°C. In samples implanted with P+ & 185keV F+, the fluorine suppresses boron transient enhanced diffusion completely at 950°C and suppresses thermal diffusion by 25% at 1025°C. In samples implanted with P+ & 42keV F+, the fluorine does not reduce boron transient enhanced diffusion at 950°C. This result is explained by the location of the boron marker layer in the vacancy-rich region of the fluorine damage profile for the 185keV implant but in the interstitial-rich region for the 42keV implant. Isolated dislocation loops are seen in the SiGe layer for the 185keV implant. We postulate that these loops are due to the partial relaxation of the metastable Si0.86Ge0.14 layer.
Thermal Stability and Electrical Properties of Ag(Al) Metallization
Authors: Kim Hyunchul C. , Theodore N. David , Mayer James W. , Alford Terry L. 
Published: April 2011

AbstractThe thermal stability and electrical resistivity of Ag(Al) alloy thin films on SiO2 are investigated and compared to pure Ag thin films by performing various analyses: Rutherford backscattering spectrometry (RBS), X-ray diffractometry (XRD), transmission electron microscopy (TEM), and four-point probe. The susceptibility to agglomeration of Ag on SiO2 layer is a drawback of Ag metallization. Ag(Al) thin films show good thermal stability on SiO2 layer without any diffusion barrier. The films are stable up to 600 °C for 1 hour in vacuum. Electrical resistivity of as-deposited Ag (5 at % Al) thin film is slightly higher than that of pure Ag thin film. However, the resistivity of Ag(Al) samples annealed at high temperatures (up to 600 °C for 1 hour in vacuum) remains constant due to the improvement of thermal stability (large reduction of agglomeration). This finding can impact metallization for thin film transistors (TFT) for displays, including flexible displays, and high-speed electronics due to lower resistivity value compared to Cu thin film.
New hybrid low-k dielectric materials prepared by vinylsilane polymerization
Authors: Kang Jung-Won , Kim Byung Ro , Kang Gwi-Gwon , Moon Myung-Sun , Choi Bum-Gyu , Ko Min-Jin 
Published: April 2011

AbstractSpin-on Low-K materials are potentially very attractive as interconnection materials in a wide range of semiconductor structures. In this work, new organic-inorganic hybrid materials synthesized by vinylsilane polymerization were proposed. According to compositions and additional fabrications, dielectric constants of these materials were evaluated to be 2.3∼3.1. The hardness was 2.0GPa after 430°C curing. These materials had good adhesion strength such that fracture toughness on silicon wafer was 0.22 MPam0.5 without any adhesion promoters. This result indicates that these organicinorganic hybrid materials are very promising candidates for low-K dielectrics.
Scanning Near-Field Microwave Probe for In-line Metrology of Low-K Dielectrics
Authors: Talanov Vladimir V. , Moreland Robert L. , Scherz André , Schwartz Andrew R. , Liu Youfan 
Published: April 2011

AbstractWe have developed a novel microwave near-field scanning probe technique for non-contact measurement of the dielectric constant of low-k films. The technique is non-destructive, noninvasive and can be used on both porous and non-porous dielectrics without any sample preparation. The probe has a few-micron spot size, which makes the technique well suited for real time low-k metrology on production wafers. For dielectrics with k<4 the precision and accuracy are better than 2% and 5%, respectively. Results for both SOD and CVD low-k films are presented and show excellent correlation with Hg-probe measurements. Results for k-value mapping on blanket 200mm wafers are presented as well.
Chemical Routes to Improved Mechanical Properties of PECVD Low K Thin Films
Authors: Bilodeau S.M. , Borovik A.S. , Ebbing A.A. , Vestyck D.J , Xu C. , Roeder J.F. , Baum T.H. 
Published: April 2011

AbstractIncreasing the elastic modulus and hardness of low K films is one of the key challenges towards integration of these materials into future integrated circuits. Several approaches are explored for increasing the hardness of carbon doped oxide (CDO) dielectrics. Several low K precursors and their mixtures specifically chosen to enhance the hardness (H) and modulus (E) of CDO films through chemically induced cross-linking. Composition and FTIR measurements suggest the presence of C-C and C-Si cross-linking with concurrent observation of improved film hardness and modulus at relatively low deposition temperatures. Films deposited at 373°C using diethoxy-methyl-oxiranyl have a hardness and modulus of 2.5 GPa and 18.1 GPa respectively. Films deposited at 180°C using tetramethylcyclotetrasiloxane (TMCTS) and 25% hardener have hardness and modulus of 1.5 GPa and 9.4 GPa, respectively. These film properties are significantly higher than those observed for TMCTS alone under similar deposition conditions. Based on these results a low temperature process with 25% hardener and 75% TMCTS combined with a porogen was used to produce a porous film with a k<2.5 and a hardness of 0.72GPa.
Thermomechanical Stresses in Copper Interconnect/Low-κ Dielectric Systems
Authors: Shen Y.-L. , Ege E. S. 
Published: April 2011

AbstractNumerical simulations of thermal stresses in copper interconnect and low-κ dielectric systems are carried out. The analyses include two- and three-dimensional finite element modeling of the interconnect structure. Various combinations of metal, oxide and polymer-based low-κ dielectric schemes are considered in the simulation. The evolution of stresses and deformation pattern in copper, barrier layers, and the dielectrics are critically assessed.