bluuebunny/crossref_metadata_2025 huggingface dataset:
One and Two-Dimensional Pattern Formation on Ion Sputtered Silicon
Authors: Brown Ari-David , Bola George H. , Aziz Michael J. , Erlebacher Jonah
Published: April 2011

The evolution of surface morphology during ion beam erosion of Si(111) at glancing ion incidence (60° from normal, 500 eV Ar+, 0.75 mA/cm2 collimated beam current) was studied over a temperature range of 500–730° Celsius. Keeping ion flux, incident angle, and energy fixed, it was found that one-dimensional sputter ripples with wavevector oriented perpendicular to the projected ion beam direction form during sputtering at the lower end of the temperature range. For temperatures above approximately 690° Celsius, growth modes both parallel and perpendicular to the projected ion beam direction contribute to the surface morphological evolution. This effect leads to the formation of bumps (“dots”) with nearly rectangular symmetry.
Characterization of “TEMPOS”: A new

T

unable

E

lectronic

M

aterial with

P

ores in

O

xide on

S

ilicon
Authors: Fink Dietmar , Petrov Alexander , Hoppe Kurt , Fahrner Wolfgang R.
Published: April 2011

Recently etched heavy ion tracks in MOS devices were filled with (semi)conducting materials to enable charge extraction from, or injection into the conducting channel below the Si/oxide interface, respectively. This leads to a family of novel electronic devices that we denoted as “TEMPOS” structures - that acronym stands for “Tunable Electronic Material with Pores in Oxide on Silicon”. In comparison with MOS-FETs, TEMPOS structures have some unique properties due to their additional parameters such as the track diameter, density, and shape, and the material embedded therein and its spatial distribution. This makes these novel structures much more complex, and it eventually leads to higher compactation of the TEMPOS circuits and to unexpected electronic properties. Depending on the choice of these parameters and the working point of these structures, TEMPOS elements can overtake the function of gatable resistors, condensors, photocells, hygrocells, diodes, sensors, and others. This work concentrates on some basic aspects of TEMPOS and gives some corresponding current /voltage relations and equivalent circuits.
Characterization of Nanoclusters in MgO Created by Means of Ion Implantation.
Authors: van Huis M.A. , van Veen A. , Schut H. , Kooi B.J. , De Hosson J.Th.M.
Published: April 2011

Metal nanoclusters (NCs) of lithium, zinc, silver and gold embedded in MgO were created by means of ion implantation of Li, Zn, Ag and Au ions into single crystals of MgO(100) and subsequent thermal annealing. Nanoclusters of the compound semiconductor CdSe were obtained by implantation of both Cd and Se ions. Solid noble gas clusters were formed by Kr ion implantation. Optical and structural properties of the NCs were investigated using optical absorption spectroscopy (OAS), high-resolution X-ray diffraction (XRD) and cross-sectional transmission electron microscopy (XTEM). The mean nanocluster size is estimated from the broadening of the Mie plasmon optical absorption bands using the Doyle formula. These results are compared with the NC size as obtained from XRD (using the Scherrer formula) and from direct XTEM observations. The three methods are found to be in reasonable agreement with a mean size of 4.0 and 10 nm found for the Au and Ag clusters, respectively. Using TEM observations, the relative interface energies of MgO//Au and MgO//Ag interfaces are also determined. In the case of MgO//Au, they are found not to be in agreement with theoretical predictions in the literature. CdSe nanoclusters were found to adopt different crystal structures dependent on the size. Small ones (<5 nm) appear to have a rock salt structure, larger ones the sphalerite structure. The solid krypton NC's are under high pressure. The pressure of individual Krypton bubbles was determined from the moiré fringes
Study of optical properties and TEM of Nanoparticles in Ni+-implanted Sapphire
Authors: Xiang X. , Zu X.T. , Zhu S. , Wang L.M.
Published: April 2011

64-keV Ni ion implantation was performed at room temperature up to a dose of 1×1017 cm-2 in α-Al2O3 single crystals. The charge states, structure and optical properties of metallic embedded Ni nanoparticles were studied by using X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and optical spectroscopy, respectively. XPS analysis showed that implanted Ni ions are mainly in charge state of metallic Ni0. Nanoparticles distributed from the surface to 30 nm below the surface were observed in a bright-field cross-sectional image. The size of nanoparticles ranges from 1 to 5 nm in diameter. A selected area electron diffraction (SAED) pattern shows Ni nanoparticles with lattice parameter a = 0.352 nm. A high-resolution electron microscopy (HREM) image indicated the Ni-implanted area had been entirely amorphized. A new broad absorption band centered at 400 nm appeared in the optical absorption spectrum of the as-implanted crystal, due to surface plasma resonance (SPR) of Ni nanoparticles.
Synthesis and Characterization of WOx Nanowires and their Conversion to WS2 Nanotubes
Authors: Dong Lifeng , Maiz Aitor , Jiao Jun
Published: April 2011

In this paper, we report for the first time the conversion of tungsten oxide (WOx) nanowires to tungsten sulfide (WS2) nanotubes using hydrogen (H2) gas and sulfur (S) powder as precursors instead of hydrogen sulfide (H2S) gas. Both the morphology and diameter of WS2 nanotubes were affected by the use of WOx nanowires. The diameter and length of the WOx nanowires were controlled by the growth temperature. A series of experiments confirmed that the higher the temperature was, the larger and longer the diameter and length of the WOx nanowires. When the temperature increased from 600 °C to 800 °C, the nanowire diameter increased from ∼ 15 nm to ∼50 nm. Furthermore, electron microscopy characterization reveals that the conversion of WS2 nanotubes from WOx nanowires started from outside the WOx nanowires and the conversion was not symmetrically uniform along the radial directions of the WOx nanowires.
TEM analysis of stress in GaInAs/(001)InP epitaxial systems.
Authors: Rocher André , Cabié Martiane , Ponchet Anne , Bertru Nicolas
Published: April 2011

A Transmission Electron Microscopy analysis of misfit stress based on the Stoney formula is proposed. It is applied to the GaInAs/(001)InP system to determine the residual stress for layers thicker than the critical thickness. The measured stress corresponds well to the value calculated using the elasticity theory and the nominal lattice mismatch: the structure is always nearly fully strained even for an epilayer two times larger than the critical thickness. Very few segments of misfit dislocation are observed indicating that the plastic relaxation is not active yet. A tentative explanation, based on the difficulty to create the core of a misfit dislocation, is explored.
Optical and Structural Properties of InAs/GaSb Nanostructures
Authors: Stokes D.W. , Li J.H , Forrest R.L. , Ammu S.L. , Lenzi J.C. , Moss S.C. , Nosho B.Z. , Aifer E.H. , Bennett B.R. , Whitman L.J.
Published: April 2011

The nanostructures self-organized via lateral composition modulation in 140 period (InAs)13/(GaSb)13 superlattices grown by molecular beam epitaxy have been studied by highresolution x-ray diffraction and infrared absorption. Three samples were analyzed in this study; two with lateral composition modulation and one without. X-ray reciprocal space map scans were taken to determine the average morphology of the modulated structures. Both vertical and lateral satellite peaks were observed for the samples with composition modulation, indicating the formation of two-dimensional nanowire arrays. The vertical wavelength measured for the two samples was twice the period intended by the growers. This is due to the face-centered cubic type stacking of the nanowires. Infrared absorption spectra of these two samples were compared to the spectra of the sample with no lateral composition modulation. Transitions involving the heavy- and light-hole bands in the GaSb hole quantum well and the electron subbands of the InAs electron quantum well were not evident for the samples with lateral composition modulation, indicating that the nanostructure of the lateral composition modulation affects the optical response of the sample, which is important for optoelectronic device applications.
Subwavelength Structured Optical Elements and Resonant Grating Filters
Authors: Kikuta Hisao , Iwata Koichi
Published: April 2011

We developed several optical elements with subwavelength-structured surfaces. Antireflection surfaces were fabricated on a diffraction grating. A micro-retarder array realized by the form-birefringent effect has been made for an application to a polarization camera system. And we developed narrow-band reflection wavelength filters called “guided-mode resonant grating filters”. This filter bases on a coupling of guided mode and radiation mode. After describing some examples of the filters, we mention a grating structure for an optical switch with nonlinear optical material.
Jahn-Teller Effect In Photonic Crystals
Authors: Malkova Natalia , Gopalan Venkatraman
Published: April 2011

The Jahn-Teller effect in photonic crystals as a prototype of photon-phonon interactions is studied. We are interested in removing the degeneracy of a defect state due to coupling with vibronic mode. Two-dimensional square photonic lattice of the dielectric rods in vacuum doped by the defect rod, giving the doubly degenerate E state in the first TM band gap is studied. We show that coming from the Jahn-Teller theorem, the lattice vibration with the symmetry of B1 and B2 modes should result in splitting the degeneracy of the E photon state, the lattice vibration being frozen. The stable configuration in the presence of the Jahn-Teller effect is determined from the dependence of the energy as a function of the rod displacement. Using the value of the vibronic constants, obtained from the suppercell plane wave calculations and the Finite Difference Time Domain simulations, we find the stable configuration of the lattice. We discuss the conditions to observe the effect.
Standing Wave Reflectivity in Photonic Structures Using a Scattering Type Optical Near-Field Optical Microscope
Authors: Bruyant A. , Aubert S. , Lérondel G. , Blaize S. , Bachelot R. , Royer P. , Minier V.
Published: April 2011

A method for measuring locally the normalised reflectivity spectrum in waveguiding photonic structures is presented. The latter is obtained by imaging the standing wave pattern upstream of the structure with a scattering type Scanning Near-field Optical Scanning Microscope (s-SNOM) and normalised with a simple Fourier analysis. Two kinds of sample are investigated. The first one is a corrugated integrated waveguide, the second is a fiber Bragg grating. The s-SNOM technique applied to waveguiding structures is first introduced with the case of a straight waveguide.
Creation and Optical Property of Microphotonic Crystals by Electrophoretic Deposition Method Using Micro-counter Electrode
Authors: Hamagami Jun-ichi , Hasegawa Kazuhiro , Kanamura Kiyoshi
Published: April 2011

In order to create micrometer-scale functional optical materials or devices, we have investigated on development of a novel electrophoretic deposition (EPD) method using a microelectrode as a counter electrode: This is so-called “μ-EPD method”. The μ-EPD method was applied to fabricate micro colloidal crystals consisting of monodisperse submicron polystyrene latex spheres for micro photonic application. Scanning electron micrographs of the deposit prepared under the optimized μ-EPD parameters showed a formation of microdot consisting of three-dimensionally ordered polystyrene spheres. As a result of the microscopic transmittance spectra, the microdots exhibited a narrow absorption peak and the optical stopband was observed at 460 nm for 204 nm polystyrene spheres, 675 nm for 290 nm polystyrene spheres, and 755 nm for 320 nm polystyrene spheres, respectively. The observed position is due to the Bragg diffraction of light from (111) plane of face-centered cubic opal lattice.
Anodization Time Dependent Photoluminescence Intensity of Porous Silicon
Authors: Islam Md. N. , Kumar Satyendra
Published: April 2011

The photoluminescence (PL) intensity first increases with anodization time (ta) and then decreases at very large ta. The increase in PL intensity with ta may be understood if the PL intensity is taken to be proportional to the effective volume of porous silicon (PS) layer under the probe laser beam. The effective volume of PS layer will be proportional to its thickness and reciprocal to the porosity. For a fixed anodization condition, the thickness and porosity both increase with ta. The increase in thickness increases the effective PS volume, while the increase in porosity causes the effective volume to decrease. Therefore, the intensity variation is governed by these two parameters: thickness and porosity. The observed results suggest that the thickness dominates the PL intensity initially and then the porosity becomes more important for very long ta. The PS layers prepared under ambient light illumination also exhibited the similar behaviour. The intensity variation with ta was explained as the interplay of thickness and porosity variations with ta.
Room temperature 1.3–1.55 μm laser-like emission from Ge/Si self-assembled islands in Si-based photonic crystals
Authors: Lourtioz J-M. , David S. , El Kurdi M. , Kammerer C. , Li X. , Sauvage S. , Chelnokov A. , Le Thanh V. , Bouchier D. , Boucaud P.
Published: April 2011

Experimental results are reported on various guided optic configurations that combine silicon-based photonic crystals (PC) and Ge/Si quantum island emitters. The feasibility of low-refractive-index-contrast PC waveguides by inductively-coupled-plasma (ICP) etching of buried SiGe/Si waveguides is briefly recalled from a previous work. The main body of the paper is focused on experiments that were carried out on the high-refractive-index-contrast silicon-on-insulator (SOI) system. Self-assembled Ge/Si quantum island layers were deposited on a SOI substrate that was further processed to get two-dimensional PC microcavities and waveguides. The room temperature 1.3–1.55 μm emission from Ge/Si islands is shown to be significantly enhanced in PC microcavities, the strongest enhancement being obtained with the smallest (micropillar-like) cavities surrounded by wide pores. In this latter case, the room-temperature photoluminescence amplitude is more than two-orders of magnitude larger than that of Ge/Si islands grown in unprocessed samples. A superlinear (laser-like) dependence with the optical pumping is observed in the same time. This behavior and other experimental trends would incriminate both a high carrier concentration of the photo-created electron-hole plasma and a good vertical coupling efficiency of the micro-structured silicon. A first attempt to characterize linear PC waveguides is also reported using the wideband luminescence of Ge/Si islands embedded in the guides.
Study of the Structural Transformation of Ge2Sb2Te5 Induced by Current Pulse in Phase Change Memory
Authors: Zhao Rong , Chong Tow Chong , Shi Lu Ping , Tan Pik Kie , Meng Hao , Hu Xiang , Li Ke Bin , Du An Yan
Published: April 2011

The electrical induced structural transformation of Ge2Sb2Te5 thin film in phase change memory device was investigated using micro-Raman spectroscopy and transmission electronic microscopy (TEM). Selected area electron diffraction (SAD) pattern showed that the electrical-induced Ge2Sb2Te5 film was crystallized into a face-centered cubic structure. Micro-Raman spectra show that the Ge2Sb2Te5 active layer at the high resistance state exhibited two minor peaks superposed on the broad peak after several switch cycles, which is identical to those of the Ge2Sb2Te5 active layer at the low resistance state. This is most likely due to the accumulation of segregated crystallites. TEM results suggest that the existence of nano-sized nuclei clusters resulted in the reduced resistance for the Ge2Sb2Te5 active layer at the high resistance state after first several switches. The dependence of resistance on the cycle number indicates that the deterioration of the Ge2Sb2Te5 active layer is resulted from the incomplete amorphization process, which is consistent with the micro-Raman results.
Effect of Ionic Bond in Recording Materials on Characteristics of Phase-Change Optical Disk
Authors: Terao Motoyasu
Published: April 2011

This paper discusses a crystallization model that takes difference of covalent bond and ionic bond into consideration. Ionic bond makes crystallization easier than covalent bond because ionic bond is more flexible than covalent bond. The diameter and spaces around large minus-ions should also be taken into consideration. Elements••having electronic negativity far from that of Te or Sb has a tendency to form ionic bonds. For example, Tb and In are considered to make chemical bonds having more ionic characteristics than Ge. In the case of already reported Sn or Bi addition, large ion diameter seems to increase crystallization speed.
Characterization of Ultra-Fast Phase Change Optical Disk with GaSb Material
Authors: Ito Kazunori , Tashiro Hiroko , Harigaya Makoto , Suzuki Eiko , Tani Katsuhiko , Yiwata Noriyuki , Toyoshima Nobuaki , Kitano Akiko , Kato Kenichi
Published: April 2011

We studied the crystallization mechanism of ultra-fast phase change optical disks with recording layers made of GaSb material for digital versatile disk (DVD) systems. The results of a static recording test and an amorphous mark formation simulation suggest that GaSb maintains a high crystal growth rate even at temperatures 150 degrees lower than the material's melting point. Disks with recording layers made of this material have a write speed margin ranging from DVD 3× to 8× or more.
A Study of Magnox Waste Glass Under Conditions of High Temperature, Very Deep, Geological Disposal
Authors: Hyatt Neil C. , Taylor Kathleen J. , Gibb Fergus G.F. , Lee William E.
Published: April 2011

The behaviour of a simulant Magnox waste glass was investigated under the likely conditions of high temperature, very deep, geological disposal, viz. 760°C and 0.15GPa. Under these conditions partial crystallisation of the glass is observed with the formation of LnBSiO5 (Ln = Y, La, Pr, Ce, Nd, Sm and Gd), LiNaZrSi6O15 and a palladium (ruthenium) telluride phase. The significance of these findings is discussed in the context of the high temperature, very deep, geological disposal scheme.
Thermochemical Investigations of Zirconolite, Pyrochlore and Brannerite: Candidate Materials for the Immobilization of Plutonium
Authors: Helean K. B. , Navrotsky A. , Lian J. , Ewing R. C.
Published: April 2011

Standard enthalpies of formation, ΔH°f (kJ/mol) at 298 K, were derived for three pyrochlore phases: Ca0.93Ce1.00Ti2.035O7.00 (−3656.0±5.6), Ca1.46U4+0.23U6+0.46Ti1.85O7.00 (−3610.6±4.1), Gd2Ti2O7 (−3822.5±4.9) and two zirconolite phases: CaZr1.03Ti1.97O7 (−3719.4±3.9) and CaHf1.02Ti1.98O7 (−3720.5±3.9). Enthalpies of formation with respect to an oxide phase assemblage, ΔH°f-ox (kJ/mol) at 298 K: CaO + MO2 + 2TiO2 = CaMTi2O7 or Gd2O3 + 2TiO2 = Gd2Ti2O7, and an oxide/perovskite phase assemblage: ΔH°f-pv+ox (kJ/mol) at 298 K: CaTiO3 + MO2 + TiO2 = CaMTi2O7, M = Ce, U, Hf, Zr were also calculated. All of the pyrochlore and zirconolite materials studied were stable in enthalpy with respect to their oxides. ΔH°f-ox: Ca0.93Ce1.00Ti2.035O7.00 (−54.1±5.2), Ca1.46U4+0.23U6+0.46Ti1.85O7.00 (−123.1±3.4), Gd2Ti2O7 (−113.4±2.8), CaZr1.03Ti1.97O7 (−89.6±2.8) and CaHf1.02Ti1.98O7 (−74.8±3.1). With respect to a perovskite plus oxide phase assemblage the hafnium zirconolite was marginally metastable in enthalpy (ΔH°f-pv+ox = +6.0±3.5 kJ/mol) while zirconolite was marginally stable in enthalpy (ΔH°f-pv+ox = −8.8±3.3 kJ/mol). The Ce-pyrochlore was not thermodynamically stable as measured by the enthalpy change relative to perovskite plus oxides: ΔH°f-pv+ox = Ca0.93Ce1.00Ti2.035O7.00 (+21.0±5.5). The U-pyrochlore sample was marginally stable in enthalpy relative to a perovskite plus oxide assemblage: ΔH°f-pv+ox = Ca1.46U4+0.23U6+0.46+Ti1.85O7.00 (−5.1±4.0). A significant field where the proposed waste form for excess weapons plutonium is not thermodynamically stable both at room temperature and at high temperature was defined.

ΔH°f (kJ/mol) at 298 K were derived for three brannerite phases: CeTi2O6 (−2948.8±4.3), U0.97Ti2.03O6 (−2977.9±3.5) and ThTi2O6 (−3096.5±4.3). Enthalpies of formation with respect to an oxide phase assemblage, ΔH°f-ox (kJ/mol) at 298 K: MO2 + 2TiO2 = MTi2O6, M = Ce, U, Th were also calculated. ΔH°f-ox: CeTi2O6 (+29.4±3.6), U0.97Ti2.03O6 (−7.7±2.8) and ThTi2O6 (+19.4±1.6). Thus, Ce and Th-brannerite are entropy stabilized and thermodynamically stable only at high temperature.

These thermochemical data are correlated to the observed trends in the radiation “susceptibility” of these phases. Thermodynamic data relevant to waste form processing and optimization are also discussed.
A Generic Procedure for the Assessment of the Effect of Concrete Admixtures on the Sorption of Radionuclides on Cement: Concept and Selected Results
Authors: Glaus M. A. , Laube A. , Van Loon L. R.
Published: April 2011

A screening procedure is proposed for the assessment of the effect of concrete admixtures on the sorption of radionuclides on cement. The screening procedure focuses on a broad and generic assessment and can thus be used as a tool for the assessment of concrete admixtures possibly used in the future. The experimental feasibility of the screening procedure and the relevance of the results obtained are tested using a selection of superplasticisers and set modifiers. Selected results obtained for these admixtures are presented in this contribution.
Modelling Experimental Results on Radiolytic Processes at the Spent Fuel Water Interface. I. Radiolysis Products and U Release
Authors: Bruno J. , Cera E. , Eriksen T. E. , Grivé M. , Ripoll S.
Published: April 2011

Experimental and modelling efforts in the last decade in the frame of nuclear waste management field have been focused on studying the role of the UO2 surfaces in poising the redox state of solid/water systems. For this purpose, an experimental programme was developed consisting on dissolution experiments with PWR spent fuel fragments in an anoxic environment and by using different solution compositions.

The collected data so far, indicate that production and fate of radiolysis products follow the same trends independently on the solution composition used in the tests. Hydrogen and oxygen concentrations show an initial increase with time until reaching a constant concentration. The trend observed for hydrogen peroxide is a decrease at short contact times to reach again a constant concentration with time. These steady-states indicate an overall balance of the generated radiolytic species.

Modelling work indicates that uranium dissolution is controlled by the oxidation of the spent fuel matrix in 10mM bicarbonate solutions while in the tests carried out at lower or without carbonate concentrations uranium in the aqueous phase is governed by the precipitation of schoepite.

These results are determinant to highlight that reducing conditions are restored in the aqueous phase in relatively short periods of time and at short distances away from the dynamic redox spent fuel/water interface.
Corrosion Behavior of Pre-oxidized High Burnup Spent Fuel in Salt Brine
Authors: Loida Andreas , Kienzler Bernhard , Geckeis Horst
Published: April 2011

During long-term interim storage of spent fuel, pre-oxidation of the UO2-matrix may not be ruled out completely. This can happen if air could find access to the fuel in the case of cladding failure. The aim of this work is to study the impact of pre-oxidation of the fuel surface on the UO2 matrix dissolution rate and the associated mobilization or retention of radionuclides in highly concentrated salt solutions. The tests were performed with samples that suffered pre-oxidation during up to seven years. The dissolution rate of a fuel sample contacted by small quantities of air-oxygen was found to be roughly a factor of 10 higher in comparison to non oxidized samples, but concentrations of radionuclides, especially Pu and U were hardly affected. The majority of dissolved radionuclides, especially Pu, U appear to have been reimmobilized on the fuel sample itself.
Solubility Measurement of Iron-Selenium Compounds under Reducing Conditions
Authors: Kitamura Akira , Shibata Masahiro , Kitao Hideo
Published: April 2011

Chemical behavior of selenium (Se), which was one of the important elements for performance assessment of geological disposal of high-level radioactive waste, was investigated under reducing and iron-containing conditions. A washing method for an iron diselenide (FeSe2(cr)) reagent with acidic and basic solutions was carried out for the purification of FeSe2(cr) reagent, which was considered to be a solubility limiting solid for Se under the geological disposal conditions. Furthermore, solubility of FeSe2(cr) was measured in alkaline solutions under reducing conditions, and thermodynamic data on equilibrium reactions between Se in solution and Se precipitate were obtained. It was found that the dependencies of solubility values on pH and redox potential (Eh: vs. standard hydrogen electrode) were best interpreted assuming that the solubility limiting solid was not FeSe2(cr) but Se(cr) and the aqueous species was SeO32- in the present experimental conditions. The equilibrium constant between Se(cr) and SeO32- at zero ionic strength was determined and compared with literature values. The chemical behavior of Se under geological disposal conditions was discussed.
EC GASNET Project: Gas Issues in the Safety Assessment of Deep Repositories for Nuclear Waste
Authors: Cool Wim , Cuñado Miguel , Johnson Lawrence , Mäntynen Mia , Müller Wolfgang , Norris Simon , Rodwell William , Sellin Patrik , Snellman Margit , Talandier Jean , Vieno Timo , Vines Sarah
Published: April 2011

GASNET is a “thematic network” project supported by the European Commission. Its objectives are to evaluate the present treatment in safety assessments of issues arising from the generation of gas in deep geological repositories for nuclear waste, and to improve the translation of scientific information on these issues into safety arguments for such repositories.

An overview is provided of the work that has been undertaken within the project and of the preliminary observations and conclusions that have been assembled.
Modelling the Release of Radionuclides from the Spent Fuel and their Transport in the Near Field: a Coupled Approach
Authors: Merino Juan , Cera Esther , Bruno Jordi , Martínez-Esparza Aurora
Published: April 2011

In this work we have developed a model for the release of radionuclides from the spent fuel coupled with their transport through the near field. A compartmental approach has been used, as this methodology is well suited to model integrated systems. Several processes have been taken into account: oxidative dissolution of the spent fuel matrix, radioactive decay and chains, diffusive and advective transport, retardation by sorption and secondary phase precipitation. Results illustrate the complex evolution of the radionuclide concentrations in the gap and the near field. Hence, the main conclusion from this study is the requirement to model this coupled system using a compartmental integrated approach.
Model for the Microbiological Corrosion of Copper Containers in a Deep Geologic Repository
Authors: King Fraser , Kolar Miroslav , Stroes-Gascoyne Simcha , Maak Peter
Published: April 2011

A model has been developed to predict the impact of microbiological processes on the long-term corrosion behaviour of copper containers in a deep geologic repository. The model accounts for a range of aerobic and anaerobic microbial processes. Various factors expected to limit the extent of microbial activity in the repository, such as the lack of water, evolving redox conditions, and the nutrient-poor environment, are taken into account in the model. Amongst other effects, the model predicts that microbial activity will not occur close to the container in the presence of highly compacted bentonite buffer material.
Mineralogy and some Physical Properties of the San José Bentonite - A Natural Analogue to Buffer Material Exposed to Saline Groundwater
Authors: Karnland Ola , Sellin Patrik , Olsson Siv
Published: April 2011

Bentonite clay has an important buffer function in several of the proposed systems for nuclear waste repositories. Some proposed repository locations have significant concentration of sodium and calcium chloride in the ground-water, and others may be under sea-level for part of their life-time. A crucial question is consequently if there will be any long term effects on the stability of clay minerals due to exposure to saline conditions and thereby also on the desired physical properties.

In the present study we used material from a small bentonite habitat at San José, southeastern Spain, as a natural analogue to a bentonite buffer exposed to high saline ground-water. The composition of the bentonite material was determined by use of XRD, ICP/AES, and cation exchange capacity (CEC) analyses both of bulk material and of fine fraction. The important physical properties swelling pressure and hydraulic conductivity were measured for a range of densities and NaCl concentrations. The observed smectite structure and the measured properties of the San José bentonite were similar to those found in Wyoming bentonite and no obvious effects of the harsh saline environment were observed.
MEMS Microresonators Based on Nanocrystalline Silicon
Authors: Gaspar J. , Adrega T. , Chu V. , Conde J. P.
Published: April 2011

This paper describes the fabrication and characterization of thin-film nanocrystalline silicon microresonators processed at temperatures below 110°C on glass substrates. The microelectromechanical structures consist of surface micromachined bridges of boron-doped hydrogenated nanocrystalline silicon (p+-nc-Si:H) deposited at 100°C by hot-wire chemical vapor deposition (HWCVD). The microbridges, which are suspended over an Al gate electrode, are electrostatically actuated and the mechanical resonance is detected in vacuum using an optical setup. The resonance frequency and energy dissipation in p+-nc-Si:H based resonators are studied as a function of the geometrical dimensions of the microstructures. Resonance frequencies between 700 kHz and 36 MHz and quality factors as high as 2000 are observed. A Young's modulus of 160 GPa for the structural bridge film is extracted from the experimental data using an electromechanical model and the main intrinsic energy dissipation mechanisms in nc-Si:H microresonators are discussed.
Surface Processes during Growth of Hydrogenated Amorphous Silicon
Authors: Aydil Eray S. , Agarwal Sumit , Valipa Mayur , Sriraman Saravanapriyan , Maroudas Dimitrios
Published: April 2011

Hydrogenated amorphous silicon films for photovoltaics and thin film transistors are deposited from silane containing discharges. The radicals generated in the plasma such as SiH3 and H impinge on the surface and lead to silicon film growth through a complex network of elementary surface processes that include adsorption, abstraction, insertion and diffusion of various radicals. Mechanism and kinetics of these reactions determine the film composition and quality. Developing deposition strategies for improving the film quality requires a fundamental understanding of the radical-surface interaction mechanisms. We have been using in situ multiple total internal reflection Fourier transform infrared spectroscopy and in situ spectroscopic ellipsometry in conjunction with atomistic simulations to determine the elementary surface reaction and diffusion mechanisms. Synergistic use of experiments and atomistic simulations elucidate elementary processes occurring on the surface. Herein, we review our current understanding of the reaction mechanisms that lead to a-Si:H film growth with special emphasis on the reactions of the SiH3 radical.
Roughness evolution of high-rate deposited a-SiNx:H films studied by atomic force microscopy and real time spectroscopic ellipsometry
Authors: Oever P.J. van den , Sanden M.C.M. van de , Kessels W.M.M.
Published: April 2011

The scaling behavior of the roughness evolution of silicon nitride (a-SiNx:H) films with different mass densities (deposited from SiH4-N2-H2 and SiH4-NH3 based plasmas) has been investigated by atomic force microscopy and real time spectroscopic ellipsometry. The observed roughness exponent a is similar for both films, whereas the growth exponent b is a factor of two smaller for the higher density films. The relation between the lower value of b and the higher mass density is discussed.
Low-Temperature Silicon Films Deposition by Pulsed Cathodic Arc Process for Microsystem Technologies
Authors: Xia Hui , Yang Yan , Bergstrom Paul L.
Published: April 2011

The deposition of silicon films was investigated for the first time by the pulsed cathodic vacuum arc process. This method has been employed to take the advantages of its low deposition temperature, high deposition rate, and high-energy capabilities, coupled with its relatively low operational cost. Heavily doped silicon films were deposited on silicon and glass substrates at temperatures below 100°C with pulsed deposition rate of 0.2nm/A·s. Pulsed arc currents up to 400A in 1∼5ms pulse width with 20∼300 pulses per second were studied. Compared with the direct current (D.C.) cathodic vacuum arc, numerous possibilities exist for the pulsed arc deposition to suit specific targeted film growth. The characterization of the films was carried out by scanning electron microscopy (SEM) and X-ray diffraction (XRD) in terms of materials morphological and structural properties. The production of high quality silicon film materials at low temperature would further enable the integration of microsystems with microelectronics.
Correlation of Hydrogenated Nanocrystalline Silicon Microstructure and Solar Cell Performance
Authors: Wang Keda , Canning Anthon , Weinberg-Wolf J.R. , Harley E.C.T. , Han Daxing , Yan Baojie , Yue Guozhen , Yang Jeffrey , Guha Subhendu
Published: April 2011

We used Raman and photoluminescence (PL) spectroscopy to study the relationship between the material properties and the solar cell performance of hydrogenated nanocrystalline silicon (nc-Si:H). The crystalline volume fraction (fc) was deduced from the Raman spectrum. Generally, a high fc leads to a high short circuit current density and a low open circuit voltage. PL spectra were measured using 632.8-nm and 442-nm laser lines. There are two distinguished PL peaks at 80 K, one at ∼1.4 eV originating from the amorphous region, while the other at = 0.9 eV from the nanocrystalline grain boundary regions. Generally, the intensity fraction of this low energy PL peak, IPLc/(IPLa+IPLc), was larger for 442-nm than 632.8-nm excitation, indicating an increase in crystallinity along the growth direction. However, for the best initial performance cells obtained by H2 dilution profiling and the i/p buffer layer, the intensity fraction IPLc/(IPLa+IPLc) decreased from the bulk to the topi/p interface. The Raman and PL results give insight into the correlation between the microstructures and the cell performance, and verified that properly-controlled crystallinity in the intrinsic layer and buffer layer at the i/p interface layer are important for optimizing nc-Si:H solar cells.
Doping and Mobility Profiles in Defect-Engineered Ultra-shallow Junctions: Bulk and SOI
Authors: Smith A. J. , Colombeau B. , Gwilliam R. , Collart E. , Cowern N.E.B. , Sealy B. J.
Published: April 2011

Silicon on insulator (SOI - Smartcut®) wafers were implanted with 1MeV and 300keV silicon ions to doses of 3.8x1015 cm−2 and 3x1014 cm−2, respectively, in order to modify the vacancy concentration in a controlled way. Boron was then implanted at 2keV to a dose of 1×1015 cm−2 into the near-surface part of the vacancy-engineered region. Atomic profiles were determined using SIMS and electrical profiles were measured using a novel Differential Hall Effect (DHE) technique, which enables profiling of electrically active dopants with a nanometer depth resolution. The electrical profiles provide pairs of carrier concentration and mobility values as a function of depth. The buried oxide (BOX) is proven to restrict the back diffusing interstitials positioned below the BOX from entering the silicon top layer and interacting with the boron profile. Also an increase of ∼50% in boron activation is achieved when a co-implant is used. However, SOI shows a reduced degree of activation when compared to bulk silicon, with or without a co-implant.
Post-Anneal Stress Reduction of 200 mm Silicon Wafers in Single Wafer Rapid Thermal Annealing
Authors: Setokubo Tsuyoshi , Nakano Eiichi , Aizawa Kazuo , Miyoshi Hidekazu , Yamamoto Jiro , Fukada Takashi , Yoo Woo Sik
Published: April 2011

In every wafer processing step wafer stress management is extremely important for advanced device manufacturing. Thermally induced stress on device wafers has a large impact on lithography and affects device yield. Thermally induced stress during rapid thermal annealing (RTA) steps in high density 512MB DRAM device fabrication was investigated using a lamp-based (cold wall) RTA system and compared to results using a furnace-based (hot wall) single wafer RTA system. Compared to the lamp-based (cold wall) system, RTA in a furnace-based (hot wall) system was found to be very effective in suppressing thermally induced stress and increasing device yield due to superior pattern transfer characteristics in lithography.
Modeling Atomistic Ion-Implantation and Diffusion for Simulating Intrinsic Fluctuation in MOSFETs arising from Line-Edge Roughness
Authors: Hane Masami , Ikezawa Takeo , Ezaki Tatsuya
Published: April 2011

We have developed new simulation tools to enable more precise design of sub-100nm MOSFETs. Intrinsic fluctuations in the characteristics of these devices occur as part of their statistical nature. Our three-dimensional atomistic approach to both process and device simulations enabled us to examine the coupling effects of the most significant sources of fluctuation, i.e.line-edge-roughnessandrandom discrete dopants, considering practical fabrication processes.
Modeling B clustering in Si and SiGe
Authors: Radic Ljubo , Lilak Aaron D. , Law Mark E.
Published: April 2011

Our experiments show boron-interstitial cluster dissolution is reduced during oxidation, a behavior not predicted by the current models. Both our experiments and others on the time dependence indicate the reactivation is coming from more than one cluster. Since oxidation induced interstitial injection reduces reactivation, one of the significant clusters has to release an interstitial release during dissolution. Recent ab-initio calculations provide a qualitatively different B clustering model, with two significant cluster species. Based on these energetics, we have developed a new physically based model that for the first time accounts for the experimentally observed cluster dissolution time and ambient dependence.

Anomalous B diffusion behavior is also observed in an investigation of Ge influence on B diffusion. Silicon wafers were subjected to a Si preamorphization implant (PAI), followed by Ge and B implants contained within the existing amorphous layer. The control sample received only Si PAI and B implant. Upon annealing, the peak of the B profile shifts towards the surface and increases in magnitude, exhibiting uphill diffusion. The control samples subjected to the same thermal processing exhibit TED, but no uphill diffusion behavior. This is consistent with the model of B diffusion in Si1−xGex, accounting for trapping of B at Ge sites through formation of GeB complex.
Ultra Low-dielectric-constant Materials for 65nm Technology Node and Beyond
Authors: Cui Hao , Moore Darren , Carter Richard , Eda Masaichi , Burke Peter , Gidley David , Peng Huagen
Published: April 2011

Pore characteristics including pore size distribution, porosity, and pore interconnectivity of PECVD SiCOH inter- layer dielectric (ILD) materials with different dielectric constant (κ) values have been studied. Oxygen plasma damage to SiCOH low-κ films increases dramatically as the κ value decreases. Simulations showed that, compared to the ILD film, the overhead dielectric films have a significant impact on the overall effective κ (κeff) of the BEOL interconnects. Reducing the κ values of these overhead films helps to alleviate the pressure on the κ value requirement of the ILD materials while still meeting the κeff target. Ultra low-κ (ULK) PECVD hydrogenated silicon carbide (H:SiC) films with a κ of 3.0 have been studied for the etch-stop applications. Studies of the chemical composition and bonding structure suggest that less Si-C networκs are formed and more micro-porosity are incorporated in the ULK H:SiC film. The leakage current of the ULK H:SiC film is found to be about 5 times lower than the H:S iC and H:SiCN films with higher κ values. The etch rate of ULK H:SiC film using a standard SiCOH ILD etch chemistry has been found to be negligible. Such an extremely high etch selectivity maκes these films very good etch-stop layers.
Structural and functional characterization of W-Si-N sputtered thin films for copper metallizations
Authors: Vomiero Alberto , Frabboni Stefano , Marchi Enrico Boscolo , Quaranta Alberto , Mea Gianantonio Della , Mariotto Gino , Felisari Laura
Published: April 2011

Ternary W-Si-N thin films have been reactively sputter-deposited from a W5Si3 target at different nitrogen partial pressures. The composition has been determined by 2.2 MeV4He+ beam, the structure by x-ray diffraction and transmission electron microscope, the chemical bonds by Fourier transform - infrared spectroscopy and the surface morphology by scanning electron microscopy. Electrical resistivity was measured by four point probe technique on the as grown films. The film as-deposited is amorphous with the Si/W ratio increasing from about 0.1 up to 0.55 with the nitrogen content going from 0 to 60 at%. The heat treatments up to 980 °C induce a loss of nitrogen in the nitrogen rich samples. Segregation of metallic tungsten occurs in the sample with low nitrogen content (W58Si21N21). Samples with high nitrogen content preserve the amorphous structure, despite of the precipitation of a more ordered phase inferred by FT-IR absorbance spectrum of the layer treated at highest temperature. The surface morphology depends upon the nitrogen content; the loss of nitrogen induces the formation of blistering and in the most nitrogen rich sample the formation of holes. Electrical resistivity preliminary results on the as grown layers range between 500 and 4750 μωcm passing from the lowest to the highest N concentration.
Optical Interconnect Components for Wafer Level Heterogeneous Hyper-Integration
Authors: Persans P. D. , Ojha M. , Gutmann R. J. , Lu J.-Q. , Filin A. , Plawsky J.
Published: April 2011

Optical waveguides for three-dimensionally stacked chip fabrication technologies, in which optical connection between layers plays a central role, are described. CMOS-compatible approaches to optical via and waveguide fabrication are addressed. Detailed modeling is used for design optimization and also addresses how manufacturing variations from ideal design may affect device performance.
Probing Effects of Etching Plasmas on the Properties of Porous Low-k Dielectrics
Authors: Wang L. , Liu J. , Wang W.D. , Chi D.Z. , Gidley D. W. , Yee A. F.
Published: April 2011

The application of porous low-k interlayer dielectrics is needed for reducing the parasitical capacitance, especially at 65-nm node and beyond. The understanding of process-induced modifications to material properties is crucial for a successful integration of these low-k dielectrics. The dry etching processes of porous low-k materials are important modules in ULSI fabrication. In this study, the interaction between MSQ-based JSR LKD-5109 films (shown by PALS to have interconnected 2.8 nm size pores) with CF4/O2 plasma has been investigated. Various ratios of O2 content were designed to characterize its effects on the etch rate, formation of polymerization layer, and properties of the LKD-5109 film. Composition analysis was conducted by SIMS and FTIR. Moisture absorption and fluorine diffusion into low-k films after etch process are observed, along with carbon depletion near the surface region. The influence of etching chemistries on the morphological characteristics of thin Ta barrier layers (8-nm in thickness) deposited on etched low-k films were further investigated by SEM, and it is found that oxygen concentration has significant influences on the morphological characteristics of thin Ta barriers.
Hot Wire Chemical Vapor Deposition as a Novel Synthetic Method for Electroactive Organic Thin Films
Authors: Zaharias Gillian A. , Shi Helen H. , Bent Stacey F.
Published: April 2011

We are exploring the use of hot-wire chemical vapor deposition (HW-CVD) as an alternative, solvent-free technique to produce compact polyconjugated films from vaporized monomers. This paper will focus on our attempts to deposit polyaniline, a polymer with a wide variety of optoelectronic applications. Infrared and X-ray photoelectron spectra have been obtained to characterize HW-CVD films produced using aniline as a precursor. The aromatic ring structure, essential for the polyconjugated network that leads to semiconducting properties, is largely preserved in our method. The bonding structure is analyzed, and the films are found to have significant metal incorporated from the hot wire. The implications of these results for understanding the polymerization and growth mechanism are discussed.