bluuebunny/crossref_metadata_2025 huggingface dataset:
Feasibility of producing a short, high energy s‐band linear accelerator using a klystron power source
Authors: Baillie Devin , Aubin J. St. , Fallone B. G. , Steciw S.
Published: March 2013

Purpose:

To use a finite‐element method (FEM) model to study the feasibility of producing a short s‐band (2.9985 GHz) waveguide capable of producing x‐rays energies up to 10 MV, for applications in a linac‐MR, as well as conventional radiotherapy.

Methods:

An existing waveguide FEM model developed by the authors' group is used to simulate replacing the magnetron power source with a klystron. Peak fields within the waveguide are compared with a published experimental threshold for electric breakdown. The RF fields in the first accelerating cavity are scaled, approximating the effect of modifications to the first coupling cavity. Electron trajectories are calculated within the RF fields, and the energy spectrum, beam current, and focal spot of the electron beam are analyzed. One electron spectrum is selected for Monte Carlo simulations and the resulting PDD compared to measurement.

Results:

When the first cavity fields are scaled by a factor of 0.475, the peak magnitude of the electric fields within the waveguide are calculated to be 223.1 MV/m, 29% lower than the published threshold for breakdown at this operating frequency. Maximum electron energy increased from 6.2 to 10.4 MeV, and beam current increased from 134 to 170 mA. The focal spot FWHM is decreased slightly from 0.07 to 0.05 mm, and the width of the energy spectrum increased slightly from 0.44 to 0.70 MeV. Monte Carlo results show dmax is at 2.15 cm for a 10 × 10 cm2 field, compared with 2.3 cm for a Varian 10 MV linac, while the penumbral widths are 4.8 and 5.6 mm, respectively.

Conclusions:

The authors' simulation results show that a short, high‐energy, s‐band accelerator is feasible and electric breakdown is not expected to interfere with operation at these field strengths. With minor modifications to the first coupling cavity, all electron beam parameters are improved.
From Optogenetic Technologies to Neuromodulation Therapies
Authors: Williams Justin C. , Denison Timothy
Published: March 2013

Translating optogenetic technologies into the clinic will encounter a number of technical, practical, and regulatory hurdles.
Optogenetics and Translational Medicine
Authors: Chow Brian Y. , Boyden Edward S.
Published: March 2013

Optogenetics has proven useful for understanding basic neurobiology and may next serve as a therapeutic modality in the clinic.
Terminally Differentiated CD8
+
T Cells Negatively Affect Bone Regeneration in Humans
Authors: Reinke Simon , Geissler Sven , Taylor William R. , Schmidt-Bleek Katharina , Juelke Kerstin , Schwachmeyer Verena , Dahne Michael , Hartwig Tony , Akyüz Levent , Meisel Christian , Unterwalder Nadine , Singh Navrag B. , Reinke Petra , Haas Norbert P. , Volk Hans-Dieter , Duda Georg N.
Published: March 2013

A subset of T cells inhibits bone regeneration in humans.
Quinolone-3-Diarylethers: A New Class of Antimalarial Drug
Authors: Nilsen Aaron , LaCrue Alexis N. , White Karen L. , Forquer Isaac P. , Cross R. Matthew , Marfurt Jutta , Mather Michael W. , Delves Michael J. , Shackleford David M. , Saenz Fabian E. , Morrisey Joanne M. , Steuten Jessica , Mutka Tina , Li Yuexin , Wirjanata Grennady , Ryan Eileen , Duffy Sandra , Kelly Jane Xu , Sebayang Boni F. , Zeeman Anne-Marie , Noviyanti Rintis , Sinden Robert E. , Kocken Clemens H. M. , Price Ric N. , Avery Vicky M. , Angulo-Barturen Iñigo , Jiménez-Díaz María Belén , Ferrer Santiago , Herreros Esperanza , Sanz Laura M. , Gamo Francisco-Javier , Bathurst Ian , Burrows Jeremy N. , Siegl Peter , Guy R. Kiplin , Winter Rolf W. , Vaidya Akhil B. , Charman Susan A. , Kyle Dennis E. , Manetsch Roman , Riscoe Michael K.
Published: March 2013

ELQ-300, an investigational drug for treating and preventing malaria, shows potent transmission-blocking activity in rodent models of malaria.
Intracellular Aggregation of Multimodal Silica Nanoparticles for Ultrasound-Guided Stem Cell Implantation
Authors: Jokerst Jesse V. , Khademi Christine , Gambhir Sanjiv S.
Published: March 2013

Silica nanoparticles enable multimodel imaging of stem cell implantation into the mouse heart.
CD19-Targeted T Cells Rapidly Induce Molecular Remissions in Adults with Chemotherapy-Refractory Acute Lymphoblastic Leukemia
Authors: Brentjens Renier J. , Davila Marco L. , Riviere Isabelle , Park Jae , Wang Xiuyan , Cowell Lindsay G. , Bartido Shirley , Stefanski Jolanta , Taylor Clare , Olszewska Malgorzata , Borquez-Ojeda Oriana , Qu Jinrong , Wasielewska Teresa , He Qing , Bernal Yvette , Rijo Ivelise V. , Hedvat Cyrus , Kobos Rachel , Curran Kevin , Steinherz Peter , Jurcic Joseph , Rosenblat Todd , Maslak Peter , Frattini Mark , Sadelain Michel
Published: March 2013

Five adults with chemotherapy-refractory B-ALL were induced into molecular remissions after treatment with CD19 CAR-targeted T cells.
The utility of Advanced Trauma Life Support (ATLS) clinical shock grading in assessment of trauma
Authors: Lawton Luke D , Roncal Sue , Leonard Elizabeth , Stack Amanda , Dinh Michael M , Byrne Christopher M , Petchell Jeffrey
Published: March 2013

Background

Acute haemorrhage is a major contributor to trauma related morbidity and mortality. Quantifying blood loss acutely and accurately is a difficult task and no currently accepted standard exists. We introduce a simple shock grading tool incorporating vital signs, fluid response and estimated blood loss to describe shock grade during the primary survey based on the original Advanced Trauma Life Support (ATLS) classification.

Methods

We performed a prospective cohort study of all trauma patients admitted to our emergency room over a 1-year period to evaluate the utility of this tool for emergency physicians to detect significant haemorrhage in the trauma patient. Shock grades were prospectively assigned to patients by the trauma team as part of the primary survey, and followed up to assess for outcomes. The primary outcome was a composite endpoint of clinical, radiological and operative findings consistent with significant haemorrhage. Data were analysed using linear and logistic regression to assess predictive ability and receiver operator characteristic curve to assess overall diagnostic accuracy.

Results

The overall sensitivity of the shock grading tool was 83%. The diagnostic accuracy based on area under receiver operator characteristic curve was 0.86. There was also a significant association between increasing shock grade and both injury severity score (β coefficient 7.0, p<0.001, 95% CI 6.2 to 7.8) and the presence of significant haemorrhage (OR 5.1, p<0.001, 95% CI 3.6 to 7.3).

Conclusions

We conclude that a simple ATLS based clinical tool that objectively categorises haemorrhagic shock is a useful part of the primary survey of the trauma patient, although a larger study with higher statistical power is required to evaluate this conclusion further.
Emergency department reported head injuries from skiing and snowboarding among children and adolescents, 1996–2010
Authors: Graves Janessa M , Whitehill Jennifer M , Stream Joshua O , Vavilala Monica S , Rivara Frederick P
Published: March 2013

Objectives

To evaluate the incidence of snow-sports-related head injuries among children and adolescents reported to emergency departments (EDs), and to examine the trend from 1996 to 2010 in ED visits for snow-sports-related traumatic brain injury (TBI) among children and adolescents.

Methods

A retrospective, population-based cohort study was conducted using data from the National Electronic Injury Surveillance System for patients (aged ≤17 years) treated in EDs in the USA from 1996 to 2010, for TBIs associated with snow sports (defined as skiing or snowboarding). National estimates of snow sports participation were obtained from the National Ski Area Association and utilised to calculate incidence rates. Analyses were conducted separately for children (aged 4–12 years) and adolescents (aged 13–17 years).

Results

An estimated number of 78 538 (95% CI 66 350 to 90 727) snow sports-related head injuries among children and adolescents were treated in EDs during the 14-year study period. Among these, 77.2% were TBIs (intracranial injury, concussion or fracture). The annual average incidence rate of TBI was 2.24 per 10 000 resort visits for children compared with 3.13 per 10 000 visits for adolescents. The incidence of TBI increased from 1996 to 2010 among adolescents (p<0.003).

Conclusions

Given the increasing incidence of TBI among adolescents and the increased recognition of the importance of concussions, greater awareness efforts may be needed to ensure safety, especially helmet use, as youth engage in snow sports.
SUBSTITUTIONS OVER INFINITE ALPHABET GENERATING (−β)-INTEGERS
Authors: DOMBEK DANIEL
Published: March 2013

We study positional numeration systems with negative base called (−β)-expansions in a more general setting than that of Ito and Sadahiro. We give an admissibility criterion for (−β)-expansions and discuss the properties of the set of (−β)-integers, denoted by ℤ−β. We give a description of distances between consecutive (−β)-integers and show that ℤ−β can be coded by an infinite word over an infinite alphabet, which is a fixed point of a non-erasing non-trivial morphism. We give a set of examples where ℤ−β is coded by an infinite word over a finite alphabet.
CONDITIONAL FAULT DIAGNOSABILITY OF DUAL-CUBES
Authors: ZHOU SHUMING , CHEN LANXIANG , XU JUN-MING
Published: March 2013

The growing size of the multiprocessor system increases its vulnerability to component failures. It is crucial to locate and replace the faulty processors to maintain a system's high reliability. The fault diagnosis is the process of identifying faulty processors in a system through testing. This paper shows that the largest connected component of the survival graph contains almost all of the remaining vertices in the dual-cube DCnwhen the number of faulty vertices is up to twice or three times of the traditional connectivity. Based on this fault resiliency, this paper determines that the conditional diagnosability of DCn(n ≥ 3) under the comparison model is 3n − 2, which is about three times of the traditional diagnosability.
EQUALITY SETS OF MORPHIC WORD SEQUENCES
Authors: HONKALA JUHA
Published: March 2013

We study equality sets of mappings. In particular, we study D0L equality sets. If s = (s(n))n≥0 and t = (t(n))n≥0 are D0L sequences, their equality set is defined by E(s,t) = {n ≥ 0 ∣ s(n) = t(n)}. We study various periodicity and decidability questions concerning these sets. We also study HD0L and DT0L equality sets.
GROUPOIDS, LOOP SPACES AND QUANTIZATION OF 2-PLECTIC MANIFOLDS
Authors: SÄMANN CHRISTIAN , SZABO RICHARD J.
Published: March 2013

We describe the quantization of 2-plectic manifolds as they arise in the context of the quantum geometry of M-branes and non-geometric flux compactifications of closed string theory. We review the groupoid approach to quantizing Poisson manifolds in detail, and then extend it to the loop spaces of 2-plectic manifolds, which are naturally symplectic manifolds. In particular, we discuss the groupoid quantization of the loop spaces of ℝ3, 𝕋3and S3, and derive some interesting implications which match physical expectations from string theory and M-theory.
INSTABILITIES AND STICKINESS IN A 3D ROTATING GALACTIC POTENTIAL
Authors: KATSANIKAS M. , PATSIS P. A. , CONTOPOULOS G.
Published: March 2013

We study the dynamics in the neighborhood of simple and double unstable periodic orbits in a rotating 3D autonomous Hamiltonian system of galactic type. In order to visualize the four-dimensional spaces of section, we use the method of color and rotation. We investigate the structure of the invariant manifolds that we found in the neighborhood of simple and double unstable periodic orbits in 4D spaces of section. We consider orbits in the neighborhood of the families x1v2, belonging to the x1 tree, and the z-axis (the rotational axis of our system). Close to the transition points from stability to simple instability, in the neighborhood of the bifurcated simple unstable x1v2 periodic orbits, we encounter the phenomenon of stickiness as the asymptotic curves of the unstable manifold surround regions of the phase space occupied by rotational tori existing in the region. For larger energies, away from the bifurcating point, the consequents of the chaotic orbits form clouds of points with mixing of color in their 4D representations. In the case of double instability, close to x1v2 orbits, we find clouds of points in the four-dimensional spaces of section. However, in some cases of double unstable periodic orbits belonging to the z-axis family we can visualize the associated unstable eigensurface. Chaotic orbits close to the periodic orbit remain sticky to this surface for long times (of the order of a Hubble time or more). Among the orbits we studied, we found those close to the double unstable orbits of the x1v2 family having the largest diffusion speed. The sticky chaotic orbits close to the bifurcation point of the simple unstable x1v2 orbit and close to the double unstable z-axis orbit that we have examined, have comparable diffusion speeds. These speeds are much slower than of the orbits in the neighborhood of x1v2 simple unstable periodic orbits away from the bifurcating point, or of the double unstable orbits of the same family having very different eigenvalues along the corresponding unstable eigendirections.
POLYNOMIAL VECTOR FIELDS IN ℝ3 WITH INFINITELY MANY LIMIT CYCLES
Authors: FERRAGUT ANTONI , LLIBRE JAUME , PANTAZI CHARA
Published: March 2013

We provide a constructive method to obtain polynomial vector fields in ℝ3 having infinitely many limit cycles starting from polynomial vector fields in ℝ2 with a period annulus. We present two examples of polynomial vector fields in ℝ3 having infinitely many limit cycles, one of them of degree 2 and the other one of degree 12. The main tools of our method are the Melnikov integral and the Hamiltonian structure.
ENERGY METHODS IN THE STABILITY PROBLEM FOR THE 𝔰𝔬(4) FREE RIGID BODY
Authors: BIRTEA PETRE , CAŞU IOAN
Published: March 2013

For the 𝔰𝔬(4) free rigid body the stability problem for the isolated equilibria has been completely solved using Lie-theoretical and topological arguments. For each case of nonlinear stability previously found, we construct a Lyapunov function. These Lyapunov functions are linear combinations of Mishchenko's constants of motion.
BIFURCATIONS AND CONTINUOUS TRANSITIONS IN A NONLINEAR MODEL OF INTRACELLULAR CALCIUM OSCILLATIONS
Authors: JI QUANBAO , LU YONG
Published: March 2013

Oscillatory patterns in a one-pool model with Ca 2+-activated IP 3 degradation are presented and classified, based on fast/slow dynamical analysis and two-parameter bifurcations. The whole parameter space can be partitioned into two parts, that is, the oscillatory and rest regions. For this purpose, we perform the continuation of fold bifurcation, Hopf bifurcation and saddle-node bifurcation of limit cycles, respectively. Several distinct topological types of complex intracellular Ca 2+ oscillations (especially bursting) are investigated in the oscillatory area. The classification and transition of different types of Ca 2+ oscillations may offer a possible explanation for the differences in dynamic behavior observed in real cells in response to different levels of stimulation.
MESHFREE GALERKIN KRIGING MODEL FOR BENDING AND BUCKLING ANALYSIS OF SIMPLY SUPPORTED LAMINATED COMPOSITE PLATES
Authors: BUI TINH QUOC , NGUYEN MINH NGOC
Published: March 2013

Further development of the novel meshfree Galerkin Kriging method for bending and buckling analysis of laminated composite plates is the main objective of the present work. The present formulation follows the classical plate theory while the discrete equations are derived from the standard Galerkin weak form. The moving Kriging interpolation technique is used for constructing shape functions, which possess the delta property and thus no special techniques are required for imposing the essential boundary conditions. Various numerical examples with different geometries of plates for both bending and buckling analysis are solved to demonstrate the applicability and the effectiveness of the present approach. The calculated results are compared with reference solutions available in the literature and very good agreements are obtained. It obviously illustrates that the proposed method can be considered as an alternative numerical approach for buckling and bending of laminated plates.
Development of High Power Density Three-Phase Inverter
Authors: Sato Shinji , Matsui Kohei , Zushi Yusuke , Murakami Yoshinori , Tanimoto Satoshi
Published: March 2013

A high power density three-phase unit with the forced-air cooling, which has 10kW power capacity, is developed in this report. The high power three-phase unit is composed of three SiC(Silicon Carbide) power module, cooling fan, DC capacitor, gate-drive circuit, and EMI filter. And also, the design method and the evaluations of the power module, cooling system, gate-drive circuit, and EMI filter are discussed in　case that the switching frequency is 50kHz. The volume of the DC/AC converter, EMI filter, and device temperature in the rated output are respectively designed to become 220 degree, 250cc, and 120cc.
Fabrication of a SiC Double Gate Vertical Channel JFET and It's Application in Power Electronics
Authors: Schöner Adolf , Bakowski Mietek , Kumar Malhan Rajesh , Takeuchi Yuuichi , Sugiyama Naohiro , Rabkowski Jacek , Peftitsis Dimosthenis , Ranstad Per , Nee Hans-Peter
Published: March 2013

The fabrication process of an innovative epitaxial trench JFET with vertical channel and double gate control is reviewed. Due to the excellent doping and thickness control of the epitaxial re-growth techniques, the sub-micron channel can be tailored for normally-on and -off operation. Due to the vertical channel design the epitaxial trench JFETs have narrow cell pitch for high-density power integration and high saturation current capabilities. The excellent performance of these fabricated and packaged JFET devices is demonstrated with on-wafer measurements and power switching tests. High current conduction tests are performed at room temperature and elevated temperatures of 125{degree sign}C with switching frequencies of 30 kHz and 200 kHz.
Recent Advances in VJFETs at SemiSouth
Authors: Chatty Kiran , Sheridan David C. , Bondarenko Vladomyr , Schrader Robin , Speer Kevin , Casady Jeffrey B.
Published: March 2013

The fast switching speeds, large current handling capability and superior thermal properties of SiC makes SiC Vertical Trench JFETs (VJFETs) ideal candidates for power electronic applications. This paper reports on the recent progress in the development of a low resistance 1200V/25mOhm EM VJFET and a new range of DM JFETs with ratings from 650V to 1700V, and resistances below 22mOhms. The lowest rated voltage class of VJFET, the 650V/55mOhm DM VJFET designed for use in 600-800V applications, has a breakdown voltage of 900V and RDSON,SP of 1.46mOhm-cm2. This RDSON,SP is the lowest reported value for a VJFET and is an order of magnitude lower compared to the best Si Super Junction (SJ) MOSFETs reported in the literature.
Growth and Characterization of Thick 4H-SiC Epilayers for Very High Voltage Bipolar Devices
Authors: Tsuchida Hidekazu , Miyazawa Tetsuya , Zhang Xuan , Nagano Masahiro , Tanuma Ryohei , Kamata Isaho , Ito Masahiko
Published: March 2013

To establish elemental technologies of thick 4H-SiC epitaxial growth for very high voltage bipolar devices, reduction methods for Z1/2 center, BPDs and in-grown stacking faults have been investigated. Complete elimination of the Z1/2 center in a very thick (>100 μm) epilayer and significant enhancement of carrier lifetimes are achieved by growing the epilayer under proper conditions followed by application of the post-growth process. A new method to convert remaining BPDs in an epilayer to TEDs by simple high temperature annealing is demonstrated. We also discuss the growth conditions to minimize the formation of the in-grown stacking faults during epitaxial growth under a H2+SiH4+C3H8 system.
Physics of GaN-based Power Field Effect Transistors
Authors: Shur Michael
Published: March 2013

Unique properties of GaN/AlN/InN heterostructures make them superior for high power applications. The key issues in the device designs are achieving normally-off operation, controlling the electric field distribution in the device channel to prevent breakdown, eliminating or reducing non-ideal effects causing reliability issues, and providing for efficient heat dissipation. High electric fields at the gate edges lead to an additional strain and hot electron effects causing the current collapse and gate lag. Quantum well designs (e.g. incorporating an InGaN or GaN quantum well between the wide band gap AlGaN barrier layer and GaN or AlGaN buffer) might control the wave function penetration and the real space transfer and increase the breakdown voltage. Insulated gate heterostructure HFETs (MOSHFETs) demonstrated superior performance and reliability. Field plates, recessed and double recessed gates, drain field controlled electrodes have been used to control current collapse and improve device reliability. An emerging approach is Frequency Configurable Electronics that enables better electric field uniformity.
III-Nitride High Voltage Nitride Electronics
Authors: Spencer Michael , Schaff William
Published: March 2013

The recent development of low dislocation density Aluminum Nitride (AlN) substrates allows the realization of a new class of majority carrier power devices. Majority carrier devices based on AlxGa1-xN grown on AlN substrates will be able to operate with breakdown voltages in excess of 20KV. A significant challenge to the development of these devices is the ionization efficiency of donor levels in high Al AlxGa1-xN. Donor ionization energies have been measured as high as .35eV for pure AlN. In order to realize the promise of these devices doped superlattice or modulation-doped blocking structures are proposed. These geometries allow for the realization of high breakdown Schottky barrier diodes and vertical MOS power transistors in high Al AlxGa1-xN.
GaN-Based Wide-Bandgap Power Switching Devices: From Atoms to the Grid
Authors: Atcitty Stanley , Kaplar Robert , DasGupta Sandeepan , Marinella Matthew , Armstrong Andrew , Biedermann Laura , Sun Min , Palacios Tomas , Smith Mark
Published: March 2013

Emerging semiconductor switches based on the wide-bandgap semiconductor GaN have the potential to significantly improve the efficiency of portable power applications such as transportable energy storage. Such applications are likely to become more widespread as renewables such as wind and solar continue to come on-line. However, the long-term reliability of GaN-based power devices is relatively unexplored. In this paper, we describe joint work between Sandia National Laboratories and MIT on high-voltage AlGaN/GaN high electron mobility transistors. It is observed that the nature of current collapse is a strong function of bias conditions as well as device design, where factors such as Al composition in the barrier layer and surface passivation play a large role. Thermal and optical recovery experiments are performed to ascertain the nature of charge trapping in the device. Additionally, Kelvin-force microscopy measurements are used to evaluate the surface potential within the device.
Passivation in High-Power Si Devices - An Overview
Authors: Grossner Ulrike , Mihaila Andrei , Vemulapati Umamaheswara
Published: March 2013

Passivation of semiconductor devices reaches back to the 1950s with passivation of silicon surfaces by thermally grown oxides. Over the years, the concept has changed towards a detailed balance of breakdown field and leakage current capabilities, involving also the underlying termination areas. In this contribution, a brief historical overview of passivation of Si devices will be given. Based on the underlying physics and lessons learned, an outlook to the challenges for power devices from wide band gap materials, such as silicon carbide, is provided.
GaN Technology for Millimeter Wave Power Amplifiers
Authors: Oki Aaron K , Wojtowicz Mike , Heying Ben , Smorchkova Ioulia , Luo Ben , Siddiqui Mansoor
Published: March 2013

Gallium nitride's (GaN) superior material properties offers revolutionary performance for millimeter wave power amplifiers in terms of output power, power added efficiency, linearity, frequency, bandwidth, gain flatness, and noise. NGAS has developed a 0.2um GaN HEMT technology which demonstrates 3.6 W/mm at 40 GHz with 37% power-added-efficiency (PAE) and 8.4 dB associated gain. RF driven thermally accelerated life testing has demonstrated reliability in excess of 60 million hours median-time-to-failure at 150C junction temperature. At 55 GHz this process has demonstrated 2.8 W/mm at 23% PAE. This capability is 4 - 8 times higher power than competing GaAs HEMT technology.
eGaN FETs in Low Power Wireless Energy Converters
Authors: de Rooij Michael A , Strydom Johan T.
Published: March 2013

Wireless power applications are gaining popularity in many commodity products such as mobile phone chargers. Most of the wireless power solutions have focused on tight coupling with induction coil solutions at operating frequencies around 200 kHz, and Class E, F and S amplifier converter topologies. Recently, however, there has been a push for operation in the restricted and unlicensed lower ISM band at 6.78 MHz where traditional MOSFET technology is approaching its capability limit. Enhancement mode gallium nitride transistors offer an alternative to MOSFETs as they can switch fast enough to be ideal for wireless power applications. This paper will focus on the experimental evaluation of an induction coil wireless energy system using Efficient Power Conversion's (EPC) eGaN FETs in a half bridge topology operating at 6.78 MHz designed to be suitable for multiple 5 W USB based charging loads.
Ti Silicide Electrodes Low Contact Resistance for Undoped AlGaN/GaN Structure
Authors: Tsuneishi Kana , Chen Jiangning , Kakushima Kuniyuki , Ahmet Parhat , Kataoka Yoshinori , Nishiyama Akira , Sugii Nobuyuki , Tsutsui Kazuo , Natori Kenji , Hatorri Takeo , Iwai H.
Published: March 2013

Current-voltage characteristics of Ti and TiSi2 electrodes on AlGaN/GaN structures have been characterized. Ti electrode has revealed annealing temperature dependent properties presumably due to excess reaction with AlGaN layer. Owing to inert properties of TiSi2, stable current-voltage characteristics have been obtained.
XPS Analysis of AlGaN/GaN Surface after Chemical and N-Containing Plasma Treatments
Authors: Meunier Richard , Torres Alphonse , Charles Matthew , Morvan Erwan , Petit-Etienne Camille , Renault O. , Billon T.
Published: March 2013

The effects of chemical treatment and nitride based plasma on an AlGaN/GaN heterostructure surface are investigated by XPS analyses. Different chemical treatments were evaluated in order to reduce the surface oxide, while N-based plasma treatments such as in-situ N2 and NH3, as well as decoupled forming gas plasmas were tested for nitridation effect on the surface. A 10% NH4OH solution proved to be the most efficient in removing surface oxides, with residual Ga oxides as low as 3% and Al oxides below the XPS detection limit. In terms of nitridation, a 500W decoupled forming gas plasma at 150{degree sign}C and a 50W N2 in-situ plasma at 350{degree sign}C increased drastically the N-presence at the surface, up to three times its original level. The nitride plasma also proved to be efficient in removing overall carbon contamination, as well as diminishing the surface rugosity.
(Invited) Theoretical Perspectives in Defect and Impurity Physics toward Materials Design for Oxides
Authors: Umezawa Naoto
Published: March 2013

Doping oxides with foreign elements significantly varies their electronic and structural properties. Here we demonstrate that doping is actually useful for controlling interfacial structures and photoresponse properties of several oxide materials. Based on our theory, the difference in the interfacial structures of HfO2/Si and La2O3/Si is understood by migration of Si atoms into La2O3, turning the oxide into an oxygen absorber. Analogs to the mechanism of the formation of a silicate layer at La2O3/Si, we have suggested a practical solution for the removal of a redundant SiOx layer unintentionally formed at HfO2/Si by doping with a donor, Ta, into HfO2. The theory of doped oxides has been also exported to investigate several phenomena in photocatalysis reactions such as N-doped TiO2 and Cr-doped SrTiO3. Our results clearly show that the computational materials design is feasible for doped oxides.
(Invited) Strain Effects on Dielectric Properties of Thin, Crystalline Rare Earth Oxides on Silicon
Authors: Osten H. Jörg , Schwendt Dominik
Published: March 2013

Under certain conditions, thin rare earth oxide layers epitaxially grown on Si exhibit dielectric constants that are much larger than the known bulk values. We investigate the effect of lattice-mismatch induced strain on dielectric properties. First, we report on the dependence of that enhancement effect on layer thickness for epitaxial Gd2O3 on Si(111). Controlling the oxide composition in ternary (Gd1-xNdx)2O3 thin films enables us to tune the lattice mismatch to silicon, and thus the dielectric constants of the layer from 13 (close to the bulk value) up to 20. We show that simple tetragonal distortion of the cubic lattice is not sufficient to explain the observed enhancement effects. Therefore, we propose more severe strain induced structural phase deformations.
(Invited) Room Temperature Ferromagnetism Induced by Electric Field in Cobalt-Doped TiO2
Authors: Fukumura Tomoteru , Yamada Yoshinori , Ueno Kazunori , Yuan Hongtao , Shimotani Hidekazu , Iwasa Yoshihiro , Gu Lin , Tsukimoto Susumu , Ikuhara Yuichi , Kawasaki Masashi
Published: March 2013

Electric field induced ferromagnetism at room temperature in cobalt-doped titanium dioxide was demonstrated by means of electric double layer transistor. This result represents that a carrier-mediated exchange coupling plays a principal role in the high temperature ferromagnetism in this compound. Accordingly, this compound is a promising material for room temperature semiconductor spintronics.
(Invited) Interface Trap Densities and Admittance Characteristics of III-V MOS Capacitors
Authors: Stemmer Susanne , Chobpattana Varistha , Son Junwoo , Rajan Siddharth
Published: March 2013

High-k/III-V interfaces in metal-oxide-semiconductor capacitor structures with In0.53Ga0.47As channels exhibit certain admittance characteristics that are almost universally observed, independent of the specific high-k material or deposition technique used. These include a "hump" in the capacitance-voltage curves at negative biases (depletion region) and low frequencies for n-type channels, and pronounced frequency dispersion in accumulation. The paper discusses both features in the context of the high density of non-uniformly distributed interface trap states in the semiconductor band gap that is typical of these interfaces.
Phenomena of Dielectric Capping Layer Insertion into High-κ Metal Gate Stacks in Gate-First/Gate-Last Integration
Authors: Jagannathan Hemanth , Jamison Paul , Paruchuri Vamsi K.
Published: March 2013

This paper presents systematic studies performed to investigate the properties of dielectric capping layers inserted in high-k metal gate stacks. Physical mechanisms involving such material systems are studied by using identical gate dielectric stacks of La inserted in HfO2 and are studied in both gate-first and gate-last integration. The studies reveal a strong dependence on the thermal budget that the gate stacks are subjected to in forming the capping layer induced dipoles that in turn influences the dipole related threshold voltage shifts and lowered gate leakage. By varying the position of the capping layers in the HfO2 gate dielectric, the threshold voltage and gate leakage are reduced by ~ 200mV and 1.5-2 orders of magnitude respectively in gate-last integration and ~580mV and 4 orders of magnitude respectively in gate-first integration.
Schottky Barrier Height at TiN/HfO2 Interface of TiN/HfO2/SiO2/Si Structure
Authors: Han Kai , Wang Xiaolei , Wang Wenwu , Zhang Jing , Xiang Jinjuan , Yang Hong , Zhao Chao , Chen Dapeng , Ye Tianchun
Published: March 2013

Band alignment of TiN/HfO2 interface of TiN/HfO2/SiO2/Si stack is investigated by x-ray photoelectron spectroscopy (XPS). The p-type Schottky barrier height (p-SBH) is found to increase with thicker HfO2 thickness. Since considering only the metal/dielectric interface cannot explain this phenomenon, band alignment of TiN/HfO2 interface of TiN/HfO2/SiO2/Si stack is demonstrated based on band alignment of entire gate stack. Dependence of p-SBH on HfO2 thickness is interpreted and contributed to fixed charges in gate stack, interfacial gap state charges at HfO2/SiO2 interface, and space charges in Si substrate. Electrical measurements of capacitor structures further support XPS results and corresponding explanation.
Comprehensive Study on Chemical Structures of Compositional Transition Layer at SiO2/Si(100) Interface
Authors: Suwa Tomoyuki , Teramoto Akinobu , Muro Takayuki , Kinoshita Toyohiko , Sugawa Shigetoshi , Hattori Takeo , Ohmi Tadahiro
Published: March 2013

The angle-resolved Si 2p photoelectron spectra arising from the transition layers formed on both sides of the SiO2/Si(100) interface covered with more than one SiO2 monolayer, which is device grade, were measured with the probing depth of nearly 2 nm. The novel analytical procedure of these spectra is developed by considering that one SiO2 monolayer, two compositional transition layers (CTLs), and one Si monolayer on Si substrate surface are continuously connected with each other. It was found for the interface formed in dry O2 at 900 {degree sign}C that two CTLs constitute the first and second CTLs. The first CTL formed at the interface consists mainly of Si1+, Si2+, and Si0 and the second CTL formed on the first CTL consists mainly of Si3+ and Si4+. Influences of oxidation temperature, annealing in forming gas on the chemical structures of transition layers formed on both sides of the interface are also discussed.
Introduction of New Materials into CMOS Devices
Authors: Iwai H.
Published: March 2013

With the progress of recent smart society, demand for high-performance low-power CMOS devices becomes stronger and stronger. Corresponding to the situation, the downsizing of CMOS device has been accelerated significantly. In order to solve the problem inherent in the downsizing, new structures and new materials are being aggressively introduced into MOSFETs. They are, for example, nanowire channel, metal/high-k gate stack, metal/silicide source/drain. In this paper, the status of the new material introduction to CMOS devices is described.
(Invited) A Density Functional Theory Study of the Effect of Pressure on the Formation and Migration Enthalpies of Intrinsic Point Defects in Growing Si Single Crystals
Authors: Sueoka Koji , Kamiyama Eiji , Kariyazaki Hiroaki , Vanhellemont Jan
Published: March 2013

The dependences of the formation enthalpy (Hf) and the migration enthalpy (Hm) of the self-interstitial I and the vacancy V in single crystal Si on hydrostatic pressure and on internal pressure were studied by calculating the formation energies and relaxation volumes. Density functional theory calculations were used with 216-atom supercells and with special attention for the convergence of the calculations. The obtained Hf and Hm were used to describe the impact of thermal stress on the critical pulling speed over thermal gradient ratio Γ0crit as defined in the Voronkov criterion. A nearly linear relation between Γ0crit (in 10-3 cm2min-1K-1) and σ0 (in MPa) was obtained, described by Γ0crit 1.509 - 0.023σ0. The impact of thermal stress on Γ0crit is opposite to that of hydrostatic pressure and makes the growing Si crystal more vacancy-rich. It is important to take into account the impact of stress on the generation of intrinsic point defects in developing future large diameter defect-free crystals.
(Invited) Manufacturing of Ultra Thin SOI
Authors: Bonnin Olivier , Schwarzenbach Walter , Barec V. , Daval Nicolas , Cauchy X. , Nguyen By. , Maleville C.
Published: March 2013

Devices using fully depleted undoped channels are among the most promising candidates for the next device generations due to their better immunity to short channel effects (SCE) (1) and to random dopant fluctuation. Channel engineering and control are then critical as silicon thickness fluctuation is a statistical source of VT variability and strained channels provide 47% increase in the drive current for NFETs (2) without any degradation for PFETs (3). SOI substrates from Soitec provide a complete set of manufacturing solutions either for planar or three-dimensional (FinFET) devices as they pre-integrate critical characteristics of the transistors within the wafer structure itself. Substrate robustness and readiness have been demonstrated. For planar devices the SOI thickness uniformity is controlled at +/-5A (6sigma value, all sites, all wafers) in high volume manufacturing mode. For three-dimensional devices, substrate requirements are extremely close to partially depleted ones which are in high volume manufacturing for more than 7 years.
Investigation of Doping Type Conversion and Diffusion Length Extraction of Proton Implanted Silicon by EBIC
Authors: Kirnstötter Stefan , Faccinelli Martin , Hadley Peter , Job Reinhart , Schustereder Werner , Laven Johannes G. , Schulze Hans-Joachim
Published: March 2013

Electron beam induced current (EBIC) measurements were used to determine the doping type and to extract the diffusion length in proton implanted silicon wafers. This method makes it possible to distinguish between n-type and p-type at low carrier concentrations. Because of the defects caused by the implantation, the diffusion length is much smaller in the implanted than in the non-implanted regions.
Wafer Level Statistical Evaluation of the Proton Radiation Hardness of a High-k Dielectric/Metal Gate 45 nm Bulk CMOS Technology
Authors: Claeys C. , Iacovo Serana , Kobayashi Daisuke , Mercha Abdelkarim , Griffoni Alessio , Roussel Philippe J. , Crupi Felice , Simoen Eddy
Published: March 2013

Although scaled down technologies may suffer from statistical parameter fluctuations caused by process variability, they are potentially radiation hard from a total-dose perspective. Therefore, the proton radiation hardness of a high-κ/metal gate 45 nm CMOS technology is studied using wafer level testing on 300 mm wafers. Attention is given to the correlation between pre- and post-radiation parameter variations. It is demonstrated that both the pre-irradiation process variability and the radiation-induced variability of the parameters have to be taken into account. For devices with a capping layer, the type of dielectric layer has an impact on the radiation-induced trapping mechanisms.
(Invited) The Pseudo-MOSFET: Principles and Recent Trends
Authors: Cristoloveanu Sorin , Ionica Irina , Diab Amer , Liu Fanyu
Published: March 2013

The pseudo-MOSFET (Ψ-MOSFET) is a fascinating transistor based on the upside-down MOS configuration of semiconductor-on-insulator (SOI) wafers. This technique has been conceived for quick characterization of as-grown SOI materials. MOSFET-like characteristics are measured and simple parameter extraction techniques deliver the material properties: carrier mobility and lifetime, threshold and flat-band voltages, density of interface traps and oxide charges, doping level. After reviewing the methodology for reliable characterization, we focus on recent trends enabling the enrichment of the technique.
Deep-Level Transient Spectroscopy of MOS Capacitors on GeSn Epitaxial Layers
Authors: Simoen Eddy , Vincent Benjamin , Merckling Clement , Gencarelli Federica , Chu Lung-Ku , Loo Roger
Published: March 2013

Deep levels present in MOS capacitors, fabricated on GeSn epitaxial layers on Ge-on-Si substrates have been studied by Deep-Level Transient Spectroscopy (DLTS). The gate dielectric is composed of 9 nm Al2O3 deposited by Molecular Beam Epitaxy (MBE) on two different types of Interfacial Oxide Layers (IOL). It is shown that the density of interface traps (Dit) near the valence band edge is significantly reduced for GeSn epilayers compared with the same gate stack on a Ge cap. At the same time, several deep-level traps in the germanium depletion region have been observed, whereof the origin is discussed.
The Characteristics of Gettering Ability in Advanced Multi-Chip Packaging Thinned Wafer
Authors: An Jeong-Hoon , Kim Jang-Seop , Kim Ja-Young , Lee Ki-Sang , Kang Hee-Bog , Moon Byeong-Sam , Lee Sang-Hyun , Shin Yong , Hwang Sung-Min , Park Hyun-Yul
Published: March 2013

Gettering property of Cu and Ni was investigated after MCP thinned process wafer. The test samples were prepared to various dopant concentration types of CZ or Epitaxial wafer, and various processed thinning conditions corresponding with a total remaining thickness of 100 µm, 50 µm, and 30 µm by backside grinding. It was found that the 30 µm thinned wafer maintains its Cu gettering ability for heavily boron doped samples but Ni contamination decrease the gettering ability for all samples.
Mn Silicide Nanowires on the Si(001)-2×1 Surface Having Anisotropic Strain Fields with Bi Nanolines
Authors: Miki Kazushi , Liu Hongjun , Owen James H. G.
Published: March 2013

The technique of producing new nanomaterial structures has been examined by making into a template the bismuth nanolines formed on silicon (001) surfaces. By this method, we succeeded in manganese forming its silicide wire by applying anisotropic strain using the tensile stress which arises between bismuth nanolines. The anisotropic surface stress blocks the formation of embedded structures and stabilizes the nucleation of manganese silicide islands which grow in a preferred direction at the growth temperature of 450 oC, forming nanowires with a band gap of approximately 0.6 eV, matching the reported band gap of MnSi1.7 and not that of MnSi.
Large Scale Single-Crystal Cu(In,Ga)Se2 Nanotip Arrays for High Efficiency Solar Cell
Authors: Chueh Yu-Lun
Published: March 2013

Cu(In,Ga)Se2 (CIGS) is the best material choice for solar cell owing to the highest light absorption and tunable bandgap while the further improvement of efficiency has to rely on nanostructures, which has attracted much attention in recent years , . In this paper, we demonstrated direct formation of large area Cu(In,Ga)Se2 nanotip arrays (CIGS NTRs) by using one step Ar+ milling process without template. By controlling milling time and incident angles, the length of CIGS NTRs with adjustable tilting orientations can be precisely controlled. Formation criteria of these CIGS NTRs have been discussed in terms of surface curvature, multiple components, and crystal quality, resulting in a highly anisotropic milling effect. The CIGS NTRs have very low reflectance < 0.1 % at incident wavelengths between 300 nm to 1200 nm. Open circuit voltage and short circuit current of CIGS NTRs solar cell were measured to be ~390 mV and ~22.56 mA/cm2, yielding the filling factor and the efficiency of 59 % and 5.2 %, respectively. In contrast to CIGS thin film solar cell with efficiency of 3.2 %, the nanostructured CIGS NTRs can have efficiency enhancement of ~160 % due to the higher light absorption ability because of the nanostructure.
Three-Dimensional Silicon Phononic Crystal
Authors: Lin Yu-Kai , Ting Heng-Wen , Chou Li-Jen , Chen Lih-Juann
Published: March 2013

Three-dimensional silicon phononic crystal comprising periodic hexagonal-close packed nanotubular structures was fabricated by metal nanosphere patterning and metal-assisted chemical etching. Hexagonal-close packed metal nanosphere arrays fabricated by colloidal lithography and metal dewetting process were well-defined on the surface of silicon as patterns with controllable nanosphere size and intersphere spacing. Metal-assisted chemical etching were consequently implemented by exposing patterned silicon to etching solution composed of H2O2, H2O and HF for several minutes to etch silicon. The diameter and intertube spacing of nanotubes of silicon phononic crystal can be precisely regulated by the metal nanosphere arrays pattern.These silicon phononic crystals exhibited excellent absorption and thermoelectric properties can be applied and integrated into solar cell and realized Si-based thermoelectric devices.
Controllable Surface Plasmon Resonance Properties of Hexagonal Close-Packed Metal Nanosphere Arrays
Authors: Ting Heng-Wen , Lin Yu-Kai , Chou Li-Jen , Tsai Cho-Jen , Chen Lih-Juann
Published: March 2013

The wavelength of localized surface plasmon resonance (LSPR) peak can be specifically tuned by precise control of the diameter and intersphere spacing of hexagonal close-packed metal nanosphere arrays (MSA). Large-area hexagonal close-packed metal nanosphere arrays with controllable spherical diameter and intersphere spacing are fabricated. The resonant peak locations for the maximun absorption of the localized surface plasmon were systematically measured and exhibited strong dependency on the diameter and intersphere spacing. This work demonstrates not only an inexpensive and easy route to fabricate a large-scale close-packed metal nanosphere arrays with controllable sizes compared to that can be achieved by the e-beam lithography method but also a platform for biosensor and plasmonic waveguide applications using localized surface plasmon resonance, surface-enhanced Raman scattering.
Synthesis and Characterization of the Core-Shell Au/Ga2O3 Nanowires
Authors: Wu Bao-Hsien , Hsu Chia Wei , Chou Li-Jen
Published: March 2013

Core-shell nanowires have attracted much attention for their interesting electrical properties. With Ga metal source, Au/Ga2O3 nanowires were synthesized on silica substrate via the vapor-liquid-vapor (VLS) growth mechanism in the chemical vapor deposition (CVD) system. According to the results examined by HRTEM and FESEM, the as-grown Ga2O3 nanowires are single crystal with Au at the center. And through the current-voltage measurement , we find out the resistive switching characteristic of the core-shell Au/Ga2O3 nanowires.
Extremely Low Electron Density in a Modulation-Doped Si/SiGe Two-Dimensional Electron Gases by Effective Schottky Gating
Authors: Li Jiun-Yun , Huang Chiao-Ti , Rokhinson Leonoid P. , Sturm James C.
Published: March 2013

We reported an extremely low electron density (8.3 x 1010 cm-2) of a modulation-doped Si/SiGe two-dimensional electron gas by Schottky gating. Effective Schottky gating with extremely low gate leakage current was enabled by low-temperature chemical vapor deposition epitaxial growth to suppress the surface segregation of phosphorus. Furthermore, an extremely high electron mobility of ~ 504,000 cm2/V-s at 0.3 K was also reported.
GaN High Electron Mobility Transistor Degradation: Effect of RF Stress
Authors: Douglas Erica A. , Gila B. P. , Abernathy C. R. , Ren Fan , Pearton S. J.
Published: March 2013

Sub-micron AlGaN/GaN high electron mobility transistors were RF stressed at various drain bias conditions at 10 GHz under 3 dB and 3.7 dB compression. Rapid degradation was observed above a drain bias of 20 V, with significant degradation of the Schottky contact. Additionally, electroluminescence and cathodoluminescence was performed on stressed devices. Localization of 2.2 eV defect emission was observed on a device suffering from infant mortality.