bluuebunny/crossref_metadata_2025 huggingface dataset:
FOUR-BODY CONTINUUM-DISCRETIZED COUPLED-CHANNEL CALCULATIONS APPLIED TO 6He REACTIONS AROUND THE COULOMB BARRIER
Authors: RODRÍGUEZ-GALLARDO M. , MORO A. M.
Published: May 2011

The scattering of a weakly bound three-body system by a target is studied within the four-body continuum-discretized coupled-channels (4b-CDCC) framework. Two different methods, the transformed harmonic oscillator (THO) method and the binning procedure, are used for discretizing the three-body continuum. The formalism is applied to different reactions induced by the Borromean nucleus 6 He at energies around the Coulomb barrier: 6 He +64 Zn at 13.6 MeV, 6 He +120 Sn at 17.4 MeV, and 6 He +208 Pb at 22 MeV. Elastic cross section distributions are presented for these reactions comparing both discretization methods, THO and binning, as the mass of the target increases.
A PANORAMA OF CDCC CALCULATIONS FOR DEUTERON INDUCED REACTIONS: FROM ELASTIC CROSS SECTIONS TO INELASTIC AND TRANSFER ONES
Authors: CHAU P. HUU-TAI
Published: May 2011

An overview of calculations performed within the Continuum Discretized Coupled Channels (CDCC) approach for deuteron induced reactions is given. We briefly present an extension of the CDCC formalism which accounts for the target excitations allowing us to determine ( d , d ') cross sections off deformed nuclei. We compare some calculated inelastic cross sections with experimental data. Then it is shown that the CDCC formalism can also be a useful tool to determine ( d , p ) cross sections. This point is illustrated with 54 Cr ( d , p )55 Cr reactions.
ALPHA SPECTROSCOPIC FACTOR OF 16O FROM ITS BREAKUP USING CONTINUUM DISCRETIZED COUPLED CHANNEL (CDCC) METHOD
Authors: ADHIKARI SUCHETA , BASU CHINMAY
Published: May 2011

In this work we extract the alpha spectroscopic factor ( S α) of 16 O ground state from breakup reaction. The CDCC theory is used to extract S α by comparison with 16 O breakup data from a light target (27 Al ). Extracted values show a small dependence on the single particle binding potential of 16 O at forward angles. At incident energies between 72 to 125 MeV S α varies from 2.29-2.83 (Wood Saxon binding potential) and between 2.42-3.72 (Gaussian potential).
QUASIFREE α-CLUSTER KNOCKOUT FROM LIGHT NUCLEI
Authors: COWLEY A. A.
Published: May 2011

Recent results for knockout of α-clusters from 12 C show that the reaction mechanism is very simple, even at moderate incident energy. The significance of available cluster knockout results from light nuclei, such as 9 Be and 12 C , is reviewed.
8Be DIRECT TRANSFER IN α+12C INELASTIC SCATTERING AND SIGNATURES OF THE ALPHA PARTICLE CONDENSATION IN THE NEAR-3α THRESHOLD STATES OF 12C
Authors: BELYAEVA T. L. , DEMYANOVA A. S. , OGLOBLIN A. A. , GONCHAROV S. A.
Published: May 2011

The coupled reaction channels model calculations of the direct 8 Be transfer in the α+12 C elastic and inelastic (to the 7.65 MeV [Formula: see text] and the 9.65 MeV [Formula: see text] states) scattering have been performed. It is shown that the cluster configuration with zero relative angular momentum dominates in [Formula: see text] state being 4.4 times larger than that in the ground state. In the [Formula: see text] state, a dominance of the p-orbital motion is found. The condensed properties are confirmed in the Hoyle state. The 3α exotic, but hardly a condensed structure of the [Formula: see text] state is found.
SPECTROSCOPY OF THE UNBOUND NUCLEUS 18Na
Authors: ASSIÉ M. , DE OLIVEIRA SANTOS F. , DE GRANCEY F. , ACHOURI L. , ALCANTARA-NUNEZ J. , ANGÉLIQUE J.-C. , BORCEA C. , CACERES L. , CELIKOVIC I. , CHUDOBA V. , PANG D.Y. , DAVINSON T. , DUCOIN C. , FALLOT M. , KIENER J. , LEFEBVRE-SCHUHL A. , LOTAY G. L. , MRAZEK J. , PERROT L. , SANCHEZ-BENITEZ A. M. , ROTARU F. , SAINT-LAURENT M.-G. , SOBOLEV YU. , STANOIU M. , STANOIU R. , STEFAN I. , SUBOTIC K. , WOODS P.J. , UJIC P. , WOLSKI R.
Published: May 2011

The unbound nucleus 18 Na , the intermediate nucleus in the two-proton radioactivity of 19 Mg , is studied through the resonant elastic scattering 17 Ne ( p ,17 Ne ) p . The spectroscopic information obtained in this experiment is discussed and put in perspective with previous measurements and the structure of the mirror nucleus 18 N .
2He DECAY FROM EXCITED STATES: THE 18Ne CASE
Authors: RACITI G. , DE NAPOLI M. , RAPISARDA E. , CARDELLA G. , GIACOPPO F. , SFIENTI C.
Published: May 2011

Two-proton radioactivity studies have been performed on excited states of 18 Ne produced by 20 Ne fragmentation at the FRIBs facility of the Laboratori Nazionali del Sud. The study of the relative-momentum correlations of the two protons allowed to disentangle the diproton, democratic and sequential decay contributions to the 2p emission. In order to extend the study on two-proton decay to other light-masses nuclei, an upgrade of the FRIBs facility is planned. A new configuration of the Fragment Separator would be able to increase the acceptance of the beam line and therefore the yield of the produced radioactive beams. Also the present tagging setup will be modified in view of the gain intensity, in order to sustain the higher foreseen incoming rate. Status and perspectives of the facility will be presented.
CLUSTERED LOW DENSITY NUCLEAR MATTER IN NEAR FERMI ENERGY COLLISIONS
Authors: NATOWITZ J. B. , HAGEL K. , WADA R. , QIN L. , CHEN Z. , SAHU P. , RÖPKE G. , KOWALSKI S. , BOTTOSSO C. , SHLOMO S. , BARBUI M. , FABRIS D. , LUNARDON M. , MORETTO S. , NEBBIA G. , PESENTE S. , RIZZI V. , VIESTI G. , CINAUSERO M. , PRETE G. , KEUTGEN T. , EL MASRI Y. , MAJKA Z.
Published: May 2011

Current research on clustering in low density matter formed in near Fermi energy heavy ion collisions is discussed Temperature and density dependent symmetry free energies derived from isoscaling analyses of the yields of nuclei with A ≤ 4 are far above those obtained in common effective interaction calculations, reflecting cluster formation, primarily of alpha particles, not included in such calculations.
PRODUCTION OF NEUTRON-RICH ISOTOPES IN TRANSFER-TYPE REACTIONS
Authors: ADAMIAN G.G. , ANTONENKO N.V. , SARGSYAN V.V. , SCHEID W.
Published: May 2011

The production yields of new neutron-rich 84,86 Zn and 90,92 Ge isotopes beyond N=50 and isotopes of nuclei with charge numbers Z=64-80 are estimated for future experiments in the multinucleon transfer reactions at energies close to the Coulomb barrier.
THREE-α CLUSTER STATE AROUND 40Ca CORE
Authors: ITAGAKI N. , KOKALOVA Tz. , von OERTZEN W. , MARUHN J.A.
Published: May 2011

We have studied three-α states around 40 Ca based on a microscopic α-cluster model.Quite recently experimental evidence for such states has been obtained. This study was performed by introducing a Monte Carlo technique for the description of the THSR (Tohsaki Horiuchi Schuck Röpke) wave function, which is called the "virtual THSR" wave function. The three α cluster state around 40 Ca has an energy below the Coulomb barrier top energy with a spatial extension comparable to the second 0+ state of 12 C . There is possibility that such gas-like structure of α clusters is stabilized with geometric shape when valence neutrons are added. We also discussed the appearance of geometric α cluster configurations, especially for the linear chain configurations of three α clusters, in neutron-rich C isotopes.
MULTICHANNEL ANALYSIS OF THE 16B NUCLEUS
Authors: DUFOUR MARIANNE , DESCOUVEMONT PIERRE
Published: May 2011

This work is devoted to a Generator-Coordinate-Method investigation of the 16 B spectrum with an Extended Two-Cluster Model which includes many 15 B + n channels. We find that the narrow peak above the 15 B + n threshold seen in the experiments of Kalpachieva et al. and of Lecouey et al. can be assigned to a [Formula: see text] resonance. Several resonances are obtained near the 15 B + n threshold, in particular a [Formula: see text] state which could be a possible candidate for the 16 B ground state. Comparison with Shell Model calculations is performed.
INNOVATIVE BUSINESS MODELS IN SEMICONDUCTOR FOUNDRY INDUSTRY: FROM SILICON INTELLECTUAL PROPERTY PERSPECTIVES
Authors: CHU PO-YOUNG , LEE CHENG-FEW , YUEN YUET-SHEUNG
Published: May 2011

Intellectual property (IP) is an exponentially consequential driver of competitive advantage nowadays. We bring in the technical views in the use of SIP technology as a more strategic weapon to elaborate our proposed strategies — design for manufacturability (DFM) adder, and home depot strategies through transaction cost approach that are able to be practically applying in the semiconductor foundry industry with added value by all means. DFM adder strategy is an effective solution specifying wafer processing enhancement while home depot strategy is an entire solution massing on product design integration. More substantially, these strategies are totally awesome mechanisms that can be matching and winning in the evolving marketplace for foundry industry in the 21st century.
ENTANGLEMENT DYNAMICS OF THREE-QUBIT STATES UNDER A SPIN ENVIRONMENT
Authors: MA XIAO SAN , LIU GAO SHENG , WANG AN MIN
Published: May 2011

In this paper, we investigate the entanglement dynamics of three-qubit states under a spin environment. From the analysis, we find that the entanglement dynamics of the three-qubit states depends not only on the coupling strength between the system and the environment and the number of degrees of freedom of the environment but also on the tunneling matrix elements of the spin environment and the specific state of concern. Specifically, the entanglement dynamics of the GHZ state, the W state, and the Werner state have been analyzed in detail and the conditions to identify the decoherence-free subspaces of our model have been discussed.
NONLINEAR EFFECT ON THE TRANSMISSION OF LIGHT IN A CAVITY ARRAY
Authors: LIU H. D. , WANG W. , YI X. X.
Published: May 2011

Taking nonlinear effect into account, we study theoretically the transmission properties of photons in a one-dimensional coupled cavity, the cavity located at the center of the cavity array being coupled to a two-level system. By using the traditional scattering theory and the mean-field approximation, we calculate the transmission rate of photons along the cavities, and discuss the effect of nonlinearity and the cavity-atom coupling on the photon transport. The results show that the cavity-atom couplings affect the coherent transport of photons. The dynamics of such a system is also studied by numerical simulations, the effect of the atom-field detuning and nonlinearity on the dynamics is shown and discussed.
JOINT REMOTE PREPARATION OF A MULTI-QUBIT GHZ-CLASS STATE VIA BIPARTITE ENTANGLEMENTS
Authors: WANG ZHANG-YIN
Published: May 2011

By joint actions of two separate two-qubit projective measurements, I present a new protocol for remotely preparing a two-qubit state via the shared three bipartite entanglements. The success probability and the classical communication cost are also minutely calculated. Then I concisely generalize it to multi-party case and multi-qubit state case, respectively. In contrast to the previous schemes [Int. J. Theor. Phys.48 (2009) 2005; Int. J. Theor. Phys.46 (2007) 2378; Commun. Theor. Phys.47 (2007) 247], this protocol has distinct advantages overwhelming the above ones as far as quantum resource consumption and quantum operation difficulty or intensity are concerned.
CONTROLLED TELEPORTATION OF AN ARBITRARY THREE-QUBIT STATE THROUGH A GENUINE SIX-QUBIT ENTANGLED STATE AND BELL-STATE MEASUREMENTS
Authors: NIE YI-YOU , LI YUAN-HUA , LIU JUN-CHANG , SANG MING-HUANG
Published: May 2011

We demonstrate that a genuine six-qubit entangled state introduced by Tapiador et al. [J. Phys. A42 (2009) 415301] can be used to realize the deterministic controlled teleportation of an arbitrary three-qubit state by performing only the Bell-state measurements.
QUANTUM IDENTITY AUTHENTICATION USING GAUSSIAN-MODULATED SQUEEZED STATES
Authors: HUANG PENG , ZHU JUN , LU YUAN , ZENG GUI-HUA
Published: May 2011

Two continuous-variable quantum identity authentication schemes, which are utilized to prevent active attack, are presented by using Gaussian-modulated squeezed states. The proposed schemes can both verify user's identity as well as distribute an updated new key as the authentication key. A new defined fidelity parameter is proposed to verify the identity of the communicator and detect eavesdropping. The analytical results show the feasibility of these two identity authentication schemes and the security under the attack of general Gaussian-cloner strategy and collective attack.
LOSSLESS QUANTUM DATA COMPRESSION AND QUANTUM KOLMOGOROV COMPLEXITY
Authors: ROGERS CAROLINE , NAGARAJAN RAJAGOPAL
Published: May 2011

We show that the optimal rate of lossless quantum data compression is closely related to Berthiaume, van Dam and Laplante's quantum Kolmogorov complexity. We show that:

• The expected quantum Kolmogorov complexity of a mixture is close to the optimal rate of lossless data compression of that mixture.

• If quantum Kolmogorov complexity obeys some inequality, then so does the optimal rate of lossless quantum data compression.
HAMILTONIAN MODELS FOR QUANTUM MEMORY CHANNELS
Authors: D'ARRIGO ANTONIO , BENENTI GIULIANO , FALCI GIUSEPPE
Published: May 2011

Quantum memory channels are attracting growing interest, motivated by both realistic possibilities of transferring information by means of quantum hardware and inadequacies of the memoryless approximation. In fact, subsequent uses of the same quantum transmission resource can be significantly correlated. In this paper we review two Hamiltonian models describing memory effects in a purely dephasing spin-boson channel and in a channel with damping visualized by a micromaser system, respectively. In both cases, we show that the quantum information transmission rates are higher than in the memoryless limit.
SOCIAL ENTREPRENEURSHIP AND A NEW MODEL FOR INTERNATIONAL DEVELOPMENT IN THE 21ST CENTURY
Authors: KATZENSTEIN JAMES , CHRISPIN BARBARA R.
Published: May 2011

In the last decade or so, there has been a growing interest in an area researchers are calling social entrepreneurship, a movement spearheaded by individuals with a desire to make the world a better place. This paper describes the structure and process of international development in Africa from the perspective of a social entrepreneur. The authors address the opportunities and challenges faced by social entrepreneurs as they attempt to affect large-scale social change. The result of this study is a unique development model that provides tools for the social entrepreneur to address problems and build capacity and sustainability within the African context.
THE IMPACT OF COLLEGE ENTREPRENEURIAL EDUCATION ON ENTREPRENEURIAL ATTITUDES AND INTENTION TO START A BUSINESS IN UGANDA
Authors: BYABASHAIJA WARREN , KATONO ISAAC
Published: May 2011

This paper reports results of a longitudinal quasi-experimental study that focused on the impact of entrepreneurial education and societal subjective norms on entrepreneurial attitudes and intentions of university students in Uganda to start a business. Data were collected in two waves: wave one before the entrepreneurship course and wave two after the entrepreneurship course — four months later. The sample composed of college students. Analyses included tests of significance of changes in the attitudes and intentions of students after the entrepreneurship course, the mediating role of attitudes and moderating role of employment expectations. The results show small but significant changes in attitudes and a significant mediating role of attitudes — perceived feasibility, perceived desirability and self-efficacy, but non-significant moderating influence of employment expectations. The findings offer lessons for policy makers and more questions for researchers.
Band Alignment at the Cu2O/ZnO Heterojunction
Authors: Ichimura Masaya , Song Ying
Published: May 2011

The band offset at the Cu2O/ZnO heterojunction was estimated both experimentally and theoretically following the procedure of core-level spectroscopy. The heterojunction was fabricated by electrochemical deposition, and the band offset was determined by X-ray photoelectron spectroscopy. For the theoretical calculation of the band offset, the first-principles, density-functional, pseudopotential method was used. It was predicted from both the experimental and calculation results that the valence band maximum of Cu2O is located higher than that of ZnO. The experimentally obtained valence band offset ΔE
v was 1.7 eV, and the theoretically obtained ΔE
v was 1.3–1.6 eV; both results agreed fairly well.
Study of Nitrogen Effect on the Boron Diffusion during Heat Treatment in Polycrystalline Silicon/Nitrogen-Doped Silicon Thin Films
Authors: Saci Lynda , Mahamdi Ramdane , Mansour Farida , Boucher Jonathan , Collet Maéva , Pereira Eléna Bedel , Temple-Boyer Pierre
Published: May 2011

The present paper studies the boron (B) diffusion in nitrogen (N) doped amorphous silicon (a-Si) layer in original bi-layer B-doped polycrystalline silicon (poly-Si)/in-situ N-doped Si layers (NIDOS) thin films deposited by low pressure chemical vapor deposition (LPCVD) technique. The B diffusion in the NIDOS layer was investigated by secondary ion mass spectrometry (SIMS) and Fourier transform infrared spectroscopy (FTIR) analysis. A new extended diffusion model is proposed to fit the SIMS profile of the bi-layer films. This model introduces new terms which take into account the effect of N concentration on the complex diffusion phenomena of B atoms in bi-layer films. SIMS results show that B diffusion does not exceed one third of NIDOS layer thickness after annealing. The reduction of the B diffusion in the NIDOS layer is due to the formation of complex B–N as shown by infrared absorption measurements. Electrical measurements using four-probe and Hall effect techniques show the good conductivity of the B-doped poly-Si layer after annealing treatment.
Comparison of Ferroelectric and Insulating Properties of Mn-Doped BiFeO3 Films Formed on Pt, SrRuO3/Pt, and LaNiO3/Pt Bottom Electrodes by Radio-Frequency Sputtering
Authors: Kim Jeong Hwan , Funakubo Hiroshi , Ishiwara Hiroshi
Published: May 2011

Mn-doped BiFeO3 (BFMO) films were deposited on Pt(111), SrRuO3(SRO)/Pt(111) and LaNiO3(LNO)/Pt(111) bottom electrodes by radio-frequency (RF) sputtering. <111> and <100>-oriented BFMO films were formed on the SRO/Pt and LNO/Pt bottom electrodes, respectively. The remanent polarization (P
r) in a <111>-oriented BFMO film on the SRO/Pt bottom electrode was 80 µC/cm2, which was twice larger than that in a <100>-oriented BFMO film on the LNO/Pt bottom electrode. However, the coercive field (E
c) of the BFMO film on LNO/Pt bottom electrode (242 kV/cm) was much lower than that of the BFMO film on SRO/Pt (407 kV/cm). Furthermore, improved leakage current, breakdown field, and fatigue endurance characteristics were obtained in the <100>-oriented BFMO film on LNO/Pt.
Nanosize-Induced Optically Isotropic Nematic Phase
Authors: Aya Satoshi , Le Khoa V. , Araoka Fumito , Ishikawa Ken , Takezoe Hideo
Published: May 2011

We fabricated, in a polymer matrix, liquid crystal (LC) nanosized droplets with a correlation length ξ of about 140 nm, which appear as an optically isotropic film. Differential scanning calorimetry (DSC) and light scattering measurements gave unambiguous evidences of an existence of nematic LC (NLC) order and fluctuation over a wide temperature range. The correlation length obtained by light scattering was consistent to the droplet size determined by a scanning electron microscope (SEM). The dynamic electro-optic (EO) response in such an isotropic NLC (IsoN) phase was found to be very fast, tens of µs, in a confined geometry because of the local short-range nematic order in the IsoN phase. This type of EO effect is very attractive for next-generation LC displays and light waveguides because of (1) very dark view in the absence of a field, (2) very fast response being independent of temperature and applied electric field, (3) gray-scale display capability with a constant response time, and (4) unnecessity of any surface treatment.
Ion-Irradiated Laterally Graded Ni/C Multilayers: A Combined X-ray Standing Wave and X-ray Reflectivity Analysis
Authors: Dev Bhupendra Nath , Roy Sumalay , Bera Sambhunath , Tawara Yuzuru , Schell Norbert , Grenzer Jörg , Borany Johannes von , Grötzschel Rainer
Published: May 2011

An X-ray standing wave (XSW) experimental facility was set up at the Rossendorf Beam Line (ROBL) at the European Synchrotron Radiation Facility (ESRF). Using this facility, the microstructures and ion-beam induced microstructural modifications of a nanoscale laterally graded Ni/C multilayer systems have been studied by the combined X-ray reflectivity (XRR) and XSW technique. The multilayer stack with 15 Ni/C layer pairs was fabricated on a glass substrate by ion beam sputtering. A 2 MeV Cu2+ion beam was rastered on the samples to obtain uniformly irradiated strips with fluences from 1×1014to 7×1014ions/cm2. We have observed that X-ray reflectivity at the first order Bragg peak gradually increases due to increase in multilayer period in the virgin samples. The multilayer period has expanded and interfaces broadened due to ion irradiation. X-ray standing wave analysis indicates that, during deposition, a significant amount of Ni diffuses into C layers. Up to a certain fluence, we have observed that more and more Ni atoms are incorporated into C layers. At higher fluences, Ni is progressively segregated from the C layers. These mixing and demixing phenomena of Ni in C layers as a function of ion fluence have been explained in terms of two competitive processes including ballistic mixing and chemically guided atomic movements.
Dynamics of Magnetostatically Coupled Vortices Observed by Time-Resolved Photoemission Electron Microscopy
Authors: Arai Kuniaki , Okuda Taichi , Fukumoto Keiki , Kotsugi Masato , Ohkouchi Takuo , Kodama Kenji , Kimura Takashi , Haruyama Yuichi , Nakamura Tetsuya , Matsushita Tomohiro , Osawa Hitoshi , Muro Takayuki , Matsui Shinji , Kakizaki Akito , Otani YoshiChika , Kinoshita Toyohiko
Published: May 2011

The dynamics of magnetostatically coupled vortices in a pair of ferromagnetic micron-sized disks has been observed in real space by pump–probe time-resolved photoemission electron microscopy. It is found that the dynamics of paired vortices is affected by a magnetic dipolar interaction. The displacement of a vortex core from its equilibrium position in the paired vortices during the supply of a magnetic field pulse is smaller than that in the isolated vortex, which is in qualitative agreement with micromagnetic simulation results. Unexpectedly, two eigenfrequencies of the paired vortices are different from each other. When the separation distance between the paired disks is shorter, the difference between the two eigenfrequencies is larger.
Effects of Concentration of Nanoscale Tin-Doped Indium Oxide on Electrical Breakdown of High-Resistance Liquid Crystal
Authors: Liang Bau-Jy , Liu Don-Gey , Chang Chih-Yuan , Shie Wun-Yi
Published: May 2011

According to our previous study, a high concentration of nanoscale tin-doped indium oxide (ITO) may be beneficial for protecting liquid crystal (LC) against attacks by electrostatic discharge (ESD). In this study, the influence of high-voltage stresses in an ESD test was investigated for cells doped with different concentrations of ITO. It was found that nano-ITO with a concentration of 0.4% in weight ratio deteriorated the physical properties of LC of transparency transition and charge retention. However, our experiment showed that the capability of ESD protection for the doped LC was still improved at the ITO concentration of 0.4 wt %. This finding supports the proposed model in our previous report. The role of ITO in the LC is not always beneficial, as discussed in this paper.
Effect of Pd Reactant on One-Dimensional Growth of ZnO on Si Substrate by Thermal Evaporation Method
Authors: Kim Kyoung-bum , Jeong Young Hun , Kim Chang-il , Lee Young-jin , Cho Jeong-ho , Paik Jong-hoo
Published: May 2011

ZnO nanostructures were developed on a Si(100) substrate from the powder mixture of ZnO and x mol % Pd (ZP-x) as reactants using a thermal evaporation method. The effect of Pd on the growth characteristics of one-dimensional ZnO nanostructures was investigated. High temperature X-ray diffraction patterns obviously revealed that Pd assisted the reduction of ZnO at temperatures higher than 1000 °C. Needle-like ZnO nanorod array, developed from ZP-x (x≥2) mixture, was well aligned vertically on the Si substrate at 1100 °C while nano-crystalline ZnO layer was only obtained from pure ZnO powder. Thus, it is considered that Pd is responsible for the growth of ZnO nanorod on the Si substrate at 1100 °C by providing the Zn vapor for the Zn/ZnO
x
droplets with reducing ZnO in the reactant. The developed ZnO nanorod exhibited growth direction along [001] with defect-free high crystallinity.
Carrier Gas Dependence at Initial Processes for a-Plane AlN Growth on r-Plane Sapphire Substrates by Hydride Vapor Phase Epitaxy
Authors: Tajima Jumpei , Echizen Chikashi , Togashi Rie , Murakami Hisashi , Kumagai Yoshinao , Takada Kazuya , Koukitu Akinori
Published: May 2011

The influence of the carrier gas used during the thermal cleaning of r-plane sapphire substrates and the subsequent first AlN layer growth at 1050 °C on two-step growth of a-plane AlN layers by hydride vapor phase epitaxy (HVPE) was investigated. When hydrogen (H2) was used as the carrier gas, the decomposition of r-plane sapphire occurred during the thermal cleaning, and unintentional nitridation of the sapphire surface occurred at the beginning of the growth of the first AlN layer, which resulted in the occurrence of misoriented AlN grains in the second AlN layer grown at 1450 °C. When a mixture of H2 and nitrogen (N2) was used as the carrier gas, nitridation of the sapphire surface occurred during the thermal cleaning, which also resulted in the occurrence of misoriented AlN grains. A single-crystalline a-plane AlN layer free of misoriented grains could be obtained by using only N2 as the carrier gas during the thermal cleaning and the growth of the first AlN layer to prevent nitridation of the sapphire surface.
Optical Properties of Ultrathin Copper Thin Films Sandwiched between Nb-Doped TiO2 Films Studied with Spectroscopic Ellipsometry
Authors: Lee Hosuk , Lee Hosun , Park Jun-Hyuk , Kim Han-Ki , Kong Bo Hyun , Cho Hyung Koun
Published: May 2011

Cu thin films sandwiched between Nb-doped TiO2 (NTO) thin films were grown on glass substrates using tilted-dual target DC magnetron sputtering deposition. The thicknesses of the top and bottom NTOs were nominally 30 nm, and the thicknesses of the Cu films (t) varied between 1.5 nm and 50 nm. We measured the ellipsometric angles (Ψ,Δ) of the NTO/Cu/NTO/glass by using spectroscopic ellipsometry and estimated the thicknesses and dielectric functions of the Cu films by using a multi-layer model analysis. Transmission electron microscopy measurements showed that the Cu layers evolved from aggregates of Cu nanoparticles to coalesced Cu thin films as the Cu film thickness increased. Sheet resistance data also showed that the t = 8 nm film was near the percolation threshold, suggesting that films thinner than 8 nm were aggregations of Cu nanoparticles that were not well-connected. The films thicker than 8 nm were above the percolation threshold. From the Drude model, we estimated the plasmon frequency (ωp) and the electron relaxation time (τ), which were found to increase with increasing film thickness. By applying standard critical point analysis to the second derivatives of the dielectric function spectra, we found several peaks near 1.5, 2.1, 2.5, 3.5, and 4.3 eV, and attributed to interband transitions. The peak energies (except 1.5 eV) matched to the band structure calculations of bulk Cu found in the literature.
Evaluation of a Delay-Line Detector Combined with Analog-to-Digital Converters as the Ion Detection System for Stigmatic Imaging Mass Spectrometry
Authors: Yoshimura Hidetoshi , Hazama Hisanao , Aoki Jun , Toyoda Michisato , Naito Yasuhide , Awazu Kunio
Published: May 2011

In addition to identifying analytes from the time-of-flight of ions, stigmatic imaging mass spectrometry (IMS) realizes microscopic and high-throughput imaging of multiple mass-resolved molecules. However, practical applications require a fast position- and time-sensitive ion detector. We have developed a delay-line detector combined with analog-to-digital converters (ADCs), and evaluated its performance as an ion detector for stigmatic IMS using electron ionization. The system shows spatial and temporal resolutions of 230 µm and 24 ns (4.2 ×107 frames per second), respectively. We speculate that the timing jitter of the signals limits the spatial resolution due to the signal processing devices. At a 20-fold ion optical magnification and m/z of 10,000, the estimated spatial resolution and mass resolving power m/Δm using this ion detection system with a stigmatic imaging mass spectrometer, which we are currently developing, are 12 µm and 15,000, respectively.
Tip to Side Welding of Ultrathin Pt Wires by Joule Heating
Authors: Fukui Satoru , Tohmyoh Hironori
Published: May 2011

This paper demonstrates welding the tip of an ultrathin Pt wire to the side of a similar wire by Joule heating. The tip of the wire, with a diameter of 600–800 nm, is brought into contact with the side of another wire, and they are welded together into a complex form by supplying a constant direct current through the parts in contact. The conditions for tip to side welding of Pt wires are compared to those of tip to tip welding using a parameter that was proposed previously for the tip to tip welding of two wires. The parameter depends on the current, the length and cross-sectional area of the wires and comprises a function with respect to the thermal boundary conditions. Although the successful welding conditions of tip to side welding are located in the range of those for tip to tip welding, the lower limit of the conditions for tip to side welding was slightly higher than that in tip to tip welding. Finally, a three-dimensional micrometer-scale structure was created by repeating the tip to side welding process.
Comparison of Process Options for Improving Backend-of-Line Reliability in 28 nm Node Technologies and Beyond
Authors: Aubel Oliver , Hennesthal Christian , Hauschildt Meike , Poppe Jens , Hahn Jens , Boemmels Juergen , Nopper Markus , Seidel Robert
Published: May 2011

This paper compares the most encouraging process options for improving electromigration performance in advanced technology nodes. Metal capping yields the best electromigration performance; however, this process is most challenging with respect to integration and may also suffer from significantly decreasing grain sizes in trench bottoms for future technologies. Alloying or silicidation techniques are less challenging to implement but can result in unacceptably high resistance increases. We analyze the respective results for each option and compare the performance on 45, 32, and 28 nm technology nodes. In addition, the impact of the various process options on stressmigration and time-dependent dielectric breakdown are discussed.
Role of Impurity Segregation into Cu/Cap Interface and Grain Boundary in Resistivity and Electromigration of Cu/Low-k Interconnects
Authors: Yokogawa Shinji , Kakuhara Yumi
Published: May 2011

The role of impurity segregation into the Cu/cap interface and grain boundary is discussed in terms of resistivity and electromigration (EM) lifetime. A Co-based metal capping, a CuAl seed, and new liners (Ti, Zr, and Hf) are compared as technologies for EM lifetime improvement. The roles of impurity in grain growth and electron scattering are investigated by residual resistivity measurement and physical analysis. The EM lifetime distribution and activation energy of lifetime are also investigated. The efficiency of EM improvements is discussed in terms of the trade-off characteristics of each technology during use. The EM improvement efficiency is categorized into three groups.
Improved Step Coverage of Cu Seed Layers by Magnetic-Field-Assisted Ionized Sputtering
Authors: Sakamoto Yuta , Kamada Koukichi , Hamaguchi Junichi , Sano Akifumi , Numata Yukinobu , Kodaira Shuji , Toyoda Satoru , Suu Koukou
Published: May 2011

The relationship between the ion flux of self-ionized sputtering and the static magnetic field supplied by DC coils was investigated by ion current measurements. The ion flux was clarified in order to increase the substrate ion current. The additional magnetic field perpendicular to the substrate increases the substrate ion current and decreases the side electron current. The suppression of Cu ion diffusion increases the substrate ion current of self-ionized sputtering and the current distribution depends on the magnetic field configuration. A stronger magnetic field in the region of the wafer edge is necessary to increase the substrate ion current. This condition results in an increase in bottom step coverage and any asymmetry at the wafer edge is also corrected.
New Copper Alloy, Cu(SnNx), Films Suitable for More Thermally Stable, Electrically Reliable Interconnects and Lower-Leakage Current Capacitors
Authors: Lin Chon-Hsin
Published: May 2011

The Cu(SnN
x
) alloy film formed in this study by doping a minute amount of Sn or SnN in a copper film via barrier-free Cu metallization method exhibits a good stability at high temperatures, an apparent improvement in adhesion and a greater electrical reliability, including low resistivity, lower leakage current in Cu(SnN
x
)-gate metal–oxide–semiconductor (MOS) capacitors, a longer time-dependent dielectric breakdown (TDDB) lifetime. The copper alloy films fabricated with this barrier-free Cu metallization method shall be suitable for application in future interconnects.
Prediction of Stress Induced Voiding Reliability in Cu Damascene Interconnect by Computer Aided Vacancy Migration Analysis
Authors: Shigeyama Haruhisa , Nemoto Takenao , Jr. A. Toshimitsu Yokobori,
Published: May 2011

The method of computer aided vacancy migration analysis has been developed to predict the stress induced voiding (SiV) reliability. In this method, distribution of hydrostatic stress was calculated by the finite element analysis (FEA), and vacancy concentration distribution was calculated by the finite difference analysis (FDA). In this paper, SiV acceleration tests were conducted in various widths of Cu lines in organic ultralow-kdielectric (Cu/Ta/ULK/SiCN) or silicon oxide dielectric (Cu/Ta/SiO2/SiCN) and these results were compared with the results of the vacancy migration analyses. The number of SiV failures increased in the line with width of 0.35 µm for Cu/Ta/SiO2/SiCN interconnects and 0.20 µm for Cu/Ta/ULK/SiCN interconnects, respectively, under SiV acceleration tests. The results obtained by vacancy migration analysis show similar behavior as the results of SiV acceleration tests. These results reveal that the vacancy migration analysis is useful to predict reliability of interconnects.
Atomic Layer Deposition of Thin VNx Film from Tetrakis(diethylamido)vanadium Precursor
Authors: Takeyama Mayumi B. , Sato Masaru , Sudoh Hiroshi , Machida Hideaki , Ito Shun , Aoyagi Eiji , Noya Atsushi
Published: May 2011

Thin vanadium nitride (VN
x
) films were grown by atomic layer deposition using tetrakis(diethylamido)vanadium as a precursor and NH3 as a reactant. A growth rate of 0.1 nm/cycle without incubation time is obtained. Transmission electron microscopy reveals that a nanocrystalline texture in random orientation is characteristic of the VN
x
film, which is favorable as an extremely thin barrier application. A low carbon impurity level (∼6 at.%) is achieved owing to acceleration of the transamination between the V(NR2)4 precursor and NH3. The lowest resistivity of 120 µΩ cm is successfully achieved for the VN
x
film prepared under optimized conditions.
Barrier Properties of Thin ZrNx Films Prepared by Radical-Assisted Surface Reaction
Authors: Sato Masaru , Takeyama Mayumi B. , Hayasaka Yuichirou , Aoyagi Eiji , Noya Atsushi
Published: May 2011

We have prepared thin ZrN
x
films at low temperatures without substrate heating. In the proposed process, radical species generated by the catalytic decomposition of NH3 molecules react on the sputtered Zr film to form ZrN
x
. The barrier performance of the obtained 5-nm-thick ZrN
x
film is as good as that prepared by reactive sputtering at 350 °C, indicating the usefulness of the proposed method in forming ZrN
x
films at low temperatures. We have also demonstrated the general effectiveness of the method for ZrN
x
preparation in addition to the previous result of TiN
x
.
Ru/WNx Bilayers as Diffusion Barriers for Cu Interconnects
Authors: Sari Windu , Eom Tae-Kwang , Choi Sang-Hyeok , Kim Soo-Hyun
Published: May 2011

Bilayers of Ru (7 nm)/WN
x
(8 nm) prepared by sputtering were investigated as diffusion barriers between Cu and Si, and their performances were compared as a function of N2 flow rate during the deposition of WN
x
. The Ru/WN
x
bilayer diffusion barriers were stable upon annealing at up to at least 650 °C for 30 min while a Ru single layer (15 nm in thickness) failed after annealing at 450 °C owing to the formation of Cu silicide. Grazing-angle X-ray diffractometry results showed that the crystallinity of the WN
x
film was degraded but that its nanocrystalline state preserved upon annealing at higher temperatures with increasing N2 flow rate during the deposition. These resulted in the better performance against Cu attack of bilayer diffusion barriers with the WN
x
film prepared with a higher N2 flow rate.
Formation of Palladium Silicide Thin Layers on Si(110) Substrates
Authors: Suryana Risa , Nakatsuka Osamu , Zaima Shigeaki
Published: May 2011

The formation of palladium silicide thin films from Pd/Si(110) and Pd/Si(001) systems with and without a Ti intermediate layer has been investigated. The existence of a Ti layer could improve the thermal stability of Pd2Si thin layers in Pd/Ti/Si(001). In addition, an epitaxial or highly oriented Pd2Si layer is formed in Pd/Ti/Si systems. However, the roughness of the Pd2Si/Si interface is observed in Pd/Ti/Si(110) systems, while the flatnesses of the Pd2Si/Si interface is observed in Pd/Ti/Si(001).
Isobutyl Silane Precursors for SiCH Low-k Cap Layer beyond the 22 nm Node: Analysis of Film Structure for Compatibility of Lower k-value and High Barrier Properties
Authors: Shimizu Hideharu , Tajima Nobuo , Kada Takeshi , Nagano Shuji , Shimogaki Yukihiro
Published: May 2011

To form SiCH films with a high carbon content using plasma-enhanced chemical vapor deposition (CVD), isobutyl trimethylsilane (iBTMS) and diisobutyl dimethylsilane (DiBDMS) were examined as precursors for a low-k cap layer and Cu diffusion barrier at the top of Cu lines. We elucidated the relationship between the structure of low-k SiCH films made from these newly developed precursors and their barrier properties against copper and oxygen diffusion. We also studied the relationship between the structure of SiCH and the deposition process under various RF plasma powers. A Monte Carlo simulation was employed to estimate the deposition profile in an overhang test structure. Fourier transform infrared spectroscopy (FT-IR) was used to analyze molecular structures. Our studies indicate that deposition conditions cannot dictate carbon content, but can control porosity/density. Precursor selection is thus an important factor in forming SiCH with a high carbon content that achieves both lower k and good barrier properties.
Electrical Characteristics of Novel Non-porous Low-k Dielectric Fluorocarbon on Cu Interconnects for 22 nm Generation and Beyond
Authors: Gu Xun , Nemoto Takenao , Tomita Yugo , Shirotori Akihide , Miyatani Kotaro , Saito Akane , Kobayashi Yasuo , Teramoto Akinobu , Kuroki Shin-Ichiro , Nozawa Toshihisa , Matsuoka Takaaki , Sugawa Shigetoshi , Ohmi Tadahiro
Published: May 2011

A novel non-porous low-kdielectric, fluorocarbon, deposited by new microwave excited plasma enhanced chemical vapor deposition was successfully integrated into Cu damascene interconnects for the first time. Electrical characteristics of fluorocarbon/Cu damascene lines are investigated. A compatible line to line leakage current to the one with porous low-kcarbon doped silicon oxide and a low effective dielectric constant as a value of 2.5 are achieved. The novel non-porous ultralow-kdielectric, fluorocarbon, is considered as a promising candidate to extendible for 22 nm generation and beyond.
Analysis of Sidewall Damage Layer in Low-k Film Using the Interline Dielectric Capacitance Measurements
Authors: Furuhashi Takahisa , Nakanishi Nobuto , Matsumoto Masahiro , Kido Shigenori , Okada Masakazu , Kawano Yuichi , Hirose Yukinori , Fujisawa Masahiko , Asai Koyu
Published: May 2011

We investigate a brief method extracting properties of damage layer in low-k film using the electrical measurement of Cu interconnects. In the electrical measurements, the capacitance measurement is useful for evaluating the damage layer in low-k film because the increase of k-value in low-k film affects directly the change of Cu interconnects capacitance. The interline capacitance including the damage layer can be described by a serial connected parallel-plate capacitor model. The analysis of electromagnetic field shows that the interline capacitance does not correspond to the capacitance of parallel-plate capacitor due to the fringe factors of interline capacitance. We can eliminate the fringe factors of interline capacitance by measuring the capacitances of different line heights and succeed in acquiring the relationship between the thickness and the dielectric constant of sidewall damage layer in low-k film.
Effectiveness of Dimethyl Carbonate and Dipivaloyl Methane Chemicals for Internal Repair of Plasma-Damaged Low-k Films
Authors: Nagano Shuji , Sakoda Kaoru , Hasaka Satoshi , Kobayashi Kiyoteru
Published: May 2011

We propose the use of methylating chemicals to repair plasma-damaged sites in low-k films. Dimethyl carbonate (DMC) and dipivaloyl methane (DPM) were selected as the methylating chemicals to supply methyl (CH3) groups into the bulk of damaged porous SiOCH films. The absorption of water into the damaged films was fully suppressed by the DMC repair treatment. The relative dielectric constant, which was increased from the value of 2.4 in the as-grown porous SiOCH film to 3.1 by plasma processes, recovered to 2.6 owing to the DMC treatment. In the case of the DPM repair treatment, the relative dielectric constant showed an almost full restoration from a value of 3.8 in the damaged film. To discuss the chemical reaction during the DMC repair treatments, SiO2 and the damaged porous SiOCH films subjected to the treatments were analyzed using time-of-flight secondary ion mass spectrometry and Fourier-transform infrared spectroscopy. The results can be explained using the model showing that the methyl and methoxy groups generated via the decomposition of DMC molecules react with silicon and oxygen sites in the films.
Electrochemical Reactions During Ru Chemical Mechanical Planarization and Safety Considerations
Authors: Shima Shohei , Wada Yutaka , Tokushige Katsuhiko , Fukunaga Akira , Tsujimura Manabu
Published: May 2011

We analyzed electrochemical reactions during ruthenium (Ru) chemical mechanical planarization (CMP) using a potentiostat and a quartz crystal microbalance, and considered the potential safety issues. We evaluated the valence number derived from Faraday's law using the dissolution mass change of Ru and total coulomb consumption in the electrochemical reactions for Ru in acidic solution and slurry. The valence numbers of dissolved Ru ions were distributed in the range of 2 to 3.5. As toxic ruthenium tetroxide (RuO4) has a valence number of 8, we were able to conclude that no toxic RuO4 was produced in the actual Ru CMP.
Study of Cu-Inhibitor State for Post-Chemical Mechanical Polishing Cleaning
Authors: Harada Ken , Ito Atsushi , Kawase Yasuhiro , Suzuki Toshiyuki , Hara Makoto , Sakae Rina , Kimura Chiharu , Aoki Hidemitsu
Published: May 2011

In order to reduce corrosion on the Cu surface in post-chemical mechanical polishing (CMP) cleaning, controlling the state of inhibitor layers is indispensable. In this study, to investigate the behavior of inhibitor layers in the cleaning process, Cu–benzotriazole (BTA) layers on CuO
X
were analyzed by electrochemical measurements and surface analysis. Electrochemical measurements revealed that Cu(I)–BTA can prevent corrosion more efficiently than Cu(II)–BTA, and surface analysis revealed that the Cu(I)–BTA layer is thin, whereas the Cu(II)–BTA layer is bulky. The Cu(I)–BTA layer is effective in preventing corrosion of the Cu surface.
Tribological Effects of Brush Scrubbing in Post Chemical Mechanical Planarization Cleaning on Electrical Characteristics in Novel Non-porous Low-k Dielectric Fluorocarbon on Cu Interconnects
Authors: Gu Xun , Nemoto Takenao , Tomita Yugo , Teramoto Akinobu , Sugawa Shigetoshi , Ohmi Tadahiro
Published: May 2011

Damage reduction during planarization is strongly required to avoid scratch generation and the variation in the electrical properties of low-kdielectrics leading to yield loss in an integrated circuit after the implementation of an ultralow-kdielectric in Cu damascene interconnects. An optimum process condition to reduce damage on brush scrubbing in post-chemical–mechanical-planarization (post-CMP) cleaning was proposed for advanced nonporous organic ultralow-kdielectric fluorocarbon/Cu interconnects. Increasing brush rotation rate by decreasing down pressures results in the improvement in both electric properties and particle removal efficiency. The tribological effects of brush scrubbing in post-CMP cleaning on the electrical characteristics were explored. The brush scrubbing condition of a high brush rotation rate at low down pressures contributes to the suppression of damage generation.
Development of Original End Point Detection System Utilizing Eddy Current Variation Due to Skin Effect in Chemical Mechanical Polishing
Authors: Fujita Takashi , Kitade Keita , Yokoyama Toshiyuki
Published: May 2011

An original end point detection system was developed by making use of the skin effect in chemical mechanical polishing (CMP). The developed system utilizes a critical change in the eddy current due to the skin effect. The critical change is caused by the following two phases in the polishing process. The first phase is that the eddy current increases when the magnetic flux begins to penetrate the copper film as the film thickness reduces to less than `skin depth'. The next phase is that the eddy current fades out due to substantial elimination of the copper film by further polishing. Consequently, a prominent local maximum point of the eddy current emerges at the turning point between the two phases, which can be detected sensitively before the copper film is eliminated. It was demonstrated that the developed system gains a high sensitivity by making use of a critical change in the eddy current due to the skin effect without exposing the semiconductor device excessively to an intense magnetic flux.
Development of High-Speed Copper Chemical Mechanical Polishing Slurry for Through Silicon Via Application Based on Friction Analysis Using Atomic Force Microscope
Authors: Amanokura Jin , Ono Hiroshi , Hombo Kyoko
Published: May 2011

In order to obtain a high-speed copper chemical mechanical polishing (CMP) process for through silicon vias (TSV) application, we developed a new Cu CMP slurry through friction analysis of Cu reaction layer by an atomic force microscope (AFM) technique. A lateral modulation friction force microscope (LM-FFM) is able to measure the friction value properly giving a vibration to the layer. We evaluated the torsional displacement between the probe of the LM-FFM and the Cu reaction layer under a 5 nm vibration to cancel the shape effect of the Cu reaction layer. The developed Cu CMP slurry forms a frictionally easy-removable Cu reaction layer.