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Effects of In-Medium Nucleon-Nucleon Cross Section and Nuclear Density Distribution on the Proton-Nucleus Total Reaction Cross Section
HAN Rui, CHEN Zhi-Qiang, R. Wada, ZHANG Su-Ya-La-Tu, LIU Xing-Quan, LIN Wei-Ping, JIN Zeng-Xue, HU Bi-Tao
Chin. Phys. Lett. 2013, 30 (12):
122501
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DOI: 10.1088/0256-307X/30/12/122501
We present the proton-total reaction cross sections σR by comparing the experimental data with the Glauber model calculation using four sets of nucleon-nucleon cross sections used in literature (free nucleon-nucleon cross sections (NNCS), phenomenological NNCS, Bruckner-type NNCS and Pauli NNCS) and different nuclear densities for symmetric and asymmetric nuclei. For light symmetric target nuclei, the experimental σR data are well reproduced by the former three NNCS with the ground state density distributions of relativistic mean-field theory. On the other hand, for asymmetry heavier target nuclei, the calculations of the σR data depend significantly on the nuclear density distribution at large radius in the low energy region. The experimental σR of these nuclei are well reproduced by the empirical 3 pF density distribution and the in-medium NNCS. The neutron surface distributions are also discussed based on the 3 pF nuclear charge distributions.
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Numerical Simulations of Magnetic Reconnection in an Asymmetric Current Sheet
WANG Pei-Ran, HUANG Can, LU Quan-Ming, WANG Rong-Sheng, WANG Shui
Chin. Phys. Lett. 2013, 30 (12):
125202
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DOI: 10.1088/0256-307X/30/12/125202
Previous particle-in-cell simulations have shown that electron phase-space holes (electron holes), where the associated parallel electric field has a bipolar structure, exist near the four separatrices in anti-parallel magnetic reconnection. By performing two-dimensional (2-D) particle-in-cell (PIC) simulations, here we investigate magnetic reconnection in an asymmetric current sheet, with emphasis on the parallel electric field near the separatrices. Compared with magnetic reconnection in a symmetric current sheet, it is found that the parallel electric field with a bipolar structure only exists around the separatrices in the upper region with a lower density (upper separatrices). Such a bipolar structure of the parallel electric field is considered to be associated with electron holes resulting from the nonlinear evolution of the electron beam instability excited by the high-speed electron flow formed after their acceleration around the X line. The disappearance of the parallel electric field around the separatrices in the lower region with a higher density (lower separatrices) may be due to the transverse instability, which is unstable in a weak magnetized plasma.
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Cavity Swelling in Three Ferritic-Martensitic Steels Irradiated by 196 MeV Kr Ions
LI Yuan-Fei, SHEN Tie-Long, GAO Xing, YAO Cun-Feng, WEI Kong-Fang, SUN Jian-Rong, LI Bing-Sheng, ZHU Ya-Bin, PANG Li-Long, CUI Ming-Huan, CHANG Hai-Long, WANG Ji, ZHU Hui-Ping, HU Bi-Tao, WANG Zhi-Guang
Chin. Phys. Lett. 2013, 30 (12):
126101
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DOI: 10.1088/0256-307X/30/12/126101
We report on cavity swelling at peak damage regions of three ferritic-martensitic (FM) steels (NHS, RAFM and T91) irradiated by 196 MeV Kr ions at different temperatures (450/550°C). Cavity configurations of the irradiated specimens are investigated by transmission electron microscopy with cross-section technique. For home-made reduced activation ferritic-martensitic (RAFM) and T91 steels irradiated at 450°C, both large size and bimodal size distribution of the cavity are found in their peak damage regions, whereas novel high silicon (NHS) steel exhibits good swelling resistance at different irradiation temperatures. Temperature relativity of the cavity swelling in NHS, RAFM and T91 steels is discussed briefly.
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Pseudo Spin Torque Induced by Strain Field of Dirac Fermions in Graphene
Bumned Soodchomshom
Chin. Phys. Lett. 2013, 30 (12):
126201
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DOI: 10.1088/0256-307X/30/12/126201
The physical property of pseudo spin of electrons in graphene is investigated. In contrast to a recent description [ Phys. Rev. Lett. 106 (2011) 116803], we show that pseudo spin in graphene is not completely a real angular momentum. The pseudo spin only in the direction perpendicular to the graphene sheet is real angular momentum while the pseudo spin parallel to the graphene plane is still not real angular momentum. Interestingly, it is also shown that the Newtonian-like force and pseudo spin torque of massive Dirac electrons in graphene under strain field mimic gravitomagnetic force and gravitomagnetic spin torque, respectively. This is due to the equivalence of pseudo spin and velocity operators of (2+1)-dimensional massive electrons in graphene, different from that in real (3+1)-dimensional Dirac fields. This work reveals the new physical property of graphene as a pseudo gravitomagnetic material.
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Optoelectronic Properties of Pure and Co Doped Indium Oxide by Hubbard and modified Becke–Johnson Exchange Potentials
H. A. Rahnamaye Aliabad, M. Bazrafshan, H. Vaezi, Masood Yousaf, Junaid Munir, M. A. Saeed
Chin. Phys. Lett. 2013, 30 (12):
127101
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DOI: 10.1088/0256-307X/30/12/127101
Structural and optoelectronic properties of pure and Co doped In2O3 are studied by employing the full-potential linearized augmented plane wave method, which is known to produce highly accurate results. First principles calculations are performed with ordinary generalized gradient approximation (GGA) along with new Hubbard and modified Becke–Johnson exchange (mBJ) potential techniques. Improved band gap results are obtained for In2O3 with GGA+U and mBJ. In the case of mBJ, the band gap values are 3.5 eV and 3.4 eV for rhombohedral and cubic phases, which are in close agreement with the experimental data. Substitution of In by Co 25% alters the energy gap and a spin splitting effect is observed in these phases. For the spin-up state, it remains semiconductor, whereas for the spin-down state it shows semimetallic behavior. The value of static refractive index n(0) is 1.74 for the cubic phase, while in rhombohedral phase the values of n(0) are 1.77 and 1.74 along xx and zz optical axes, respectively. The calculated optical properties conform anisotropy in the rhombohedral phase and these materials can be potential candidates for the optoelectronics applications.
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A Novel Silicon-on-Insulator Super-Junction Lateral-Double-Diffused Metal-Oxide-Semiconductor Transistor with T-Dual Dielectric Buried Layers
WU Li-Juan, ZHANG Wen-Tong, ZHANG Bo, LI Zhao-Ji
Chin. Phys. Lett. 2013, 30 (12):
127102
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DOI: 10.1088/0256-307X/30/12/127102
A novel silicon-on-insulator (SOI) high-voltage device of super-junction (SJ) lateral-double-diffused metal-oxide-semiconductor transistors (LDMOSTs) with T-dual dielectric buried layers (T-DBLs) is presented. The T-DBLs are formed by the first T-shaped dielectric layer and the second dielectric layer. A lot of holes are accumulated on the top interface of the second dielectric layer, which compensates for the charge imbalance of the surface N and P pillars, thus the substrate-assisted depletion (SAD) effect is eliminated in the new device. The electric field of the second dielectric buried layer, EI2, is enhanced by the interface charges, and the breakdown voltage Vbreakdown is increased. EI2=515 V/μm is obtained in the T-DBL SOI SJ. The Vbreakdown of the new device is increased from 124 V of the conventional SOI SJ to 302 V with a 15 μm length drift region. The specific on-resistance (Ron, sp) of the T-DBL SOI SJ is only 0.00865 Ω?cm2 and the FOM (FOM = V2breakdown/Ron, sp) is 10.54 MW/cm2.
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First Principles Study on Elastic Constants, Ferromagnetism and Electronic Structures of Alloyed Fe3Si Doped with Mo, Ti or Nb
MA Rui, XIE Quan, HUANG Jin, GUO Xiao-Tian, YAN Wan-Jun
Chin. Phys. Lett. 2013, 30 (12):
127104
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DOI: 10.1088/0256-307X/30/12/127104
Elastic constants, ferromagnetism and electronic structures of Fe11MoSi4, Fe11TiSi4, and Fe11NbSi4 are studied by first-principles calculations with density functional theory (DFT). It is found that the ductility of Fe3Si could be obviously improved with the addition of Ti. The G/B0 of Fe11TiSi4 is 0.483, which means that it is ductile. The strong interaction of Fe 3d–Ti 3d intensifies the metallic character. However, Fe11NbSi4 has the optimal ferromagnetism. The total magnetic moments of the Fe11NbSi4 is 20.42μB. The difference between spin-up electrons and spin-down electrons at the Fermi level markedly varies with different alloying elements; furthermore, the difference at EF in the Nb case is the highest.
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AlGaN Channel High Electron Mobility Transistors with Ultra-Low Drain-Induced-Barrier-Lowering Coefficient
HA Wei, ZHANG Jin-Cheng, ZHAO Sheng-Lei, GE Sha-Sha, WEN Hui-Juan, ZHANG Chun-Fu, MA Xiao-Hua, HAO Yue
Chin. Phys. Lett. 2013, 30 (12):
127201
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DOI: 10.1088/0256-307X/30/12/127201
The conventional AlGaN/GaN high electron mobility transistor (HEMT), the AlGaN/GaN/AlGaN HEMT, and the AlxGa1?xN/AlyGa1?yN HEMT are fabricated on sapphire substrates to study the drain-induced barrier-lowering (DIBL) effect. It is found that the AlxGa1?xN/AlyGa1?yN HEMT with AlGaN channel has the lowest DIBL coefficient of 6.7 mV/V compared with the other two HEMTs. This is attributed to the best two-dimensional electron gas confinement of the AlxGa1?xN/AlyGa1?yN structure. This opinion is further confirmed by the conduction band diagrams and electron distribution calculated from the one-dimensional Poisson–Schr?dinger equation.
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High-Performance InTiZnO Thin-Film Transistors Deposited by Magnetron Sputtering
LIU Ao, LIU Guo-Xia, SHAN Fu-Kai, ZHU Hui-Hui, B. C. Shin, W. J. Lee, C. R. Cho
Chin. Phys. Lett. 2013, 30 (12):
127301
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DOI: 10.1088/0256-307X/30/12/127301
InTiZnO thin-film transistors (ITZO TFTs) with Al2O3 gate dielectrics are fabricated by magnetron sputtering at room temperature. The bottom-gate-type ITZO TFTs with amorphous Al2O3 gate dielectrics are operated in the enhancement mode and exhibit a mobility of 50.4 cm2/V?s, threshold voltage of 1.2 V, subthreshold swing of 94.5 mV/decade, and on/off-current ratio of 7×106. We believe that ITZO deposited at room temperature is an appropriate semiconductor material to produce high-mobility TFTs for developing flexible electronic devices.
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Fermi Surface and Band Structure of (Ca,La)FeAs2 Superconductor from Angle-Resolved Photoemission Spectroscopy
LIU Xu, LIU De-Fa, ZHAO Lin, GUO Qi, MU Qing-Ge, CHEN Dong-Yun, SHEN Bing, YI He-Mian, HUANG Jian-Wei, HE Jun-Feng, PENG Ying-Ying, LIU Yan, HE Shao-Long, LIU Guo-Dong, DONG Xiao-Li, ZHANG Jun, CHEN Chuang-Tian, XU Zu-Yan, REN Zhi-An, ZHOU Xing-Jiang
Chin. Phys. Lett. 2013, 30 (12):
127402
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DOI: 10.1088/0256-307X/30/12/127402
The (Ca,R)FeAs2 (R=La, Pr, etc.) superconductors with a signature of superconductivity transition above 40 K possess a new kind of block layers that consist of zig-zag As chains. We report the electronic structure of the new (Ca,La)FeAs2 superconductor investigated by both band structure calculations and high resolution angle-resolved photoemission spectroscopy measurements. Band structure calculations indicate that there are four hole-like bands around the zone center Γ(0,0) and two electron-like bands near the zone corner M(π, π) in CaFeAs2. In our angle-resolved photoemission measurements on (Ca0.9La0.1)FeAs2, we have observed three hole-like bands around the Γ point and one electron-like Fermi surface near the M(π, π) point. These results provide important information to compare and contrast with the electronic structure of other iron-based compounds in understanding the superconductivity mechanism in the iron-based superconductors.
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Fast Homoepitaxial Growth of 4H-SiC Films on 4° off-Axis Substrates in a SiH4-C2H4-H2 System
LIU Bin, SUN Guo-Sheng, LIU Xing-Fang, ZHANG Feng, DONG Lin, ZHENG Liu, YAN Guo-Guo, LIU Sheng-Bei, ZHAO Wan-Shun, WANG Lei, ZENG Yi-Ping, LI Xi-Guang, WANG Zhan-Guo, YANG Fei
Chin. Phys. Lett. 2013, 30 (12):
128101
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DOI: 10.1088/0256-307X/30/12/128101
Homoepitaxial growth of 4H-SiC epilayers is conducted in a SiH4-C2H4-H2 system by low pressure hot-wall vertical chemical vapor deposition (CVD). Thick epilayers of 45 μm are achieved at a high growth rate up to 26 μm/h under an optimized growth condition, and are characterized by using a Normaski optical microscope, a scanning electronic microscope (SEM), an atomic force microscope (AFM) and an x-ray diffractometer (XRD), indicating good crystalline quality with mirror-like smooth surfaces and an rms roughness of 0.9 nm in a 5 μm × 5μm area. The dependence of the 4H-SiC growth rate on growth conditions on 4° off-axis 4H-SiC substrates and its mechanism are investigated. It is found that the H2 flow rate could influence the surface roughness, while good surface morphologies without Si droplets and epitaxial defects such as triangular defects could be obtained by increasing temperature.
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Impact of Au Nanocrystal Size and Inter-Nanocrystal Distance on the Storage Characteristics of Memory Devices
LAN Xue-Xin, OU Xin, XU Bo, GONG Chang-Jie, LI Run, YIN Qiao-Nan, XIA Yi-Dong, YIN Jiang, LIU Zhi-Guo, LI Ai-Dong, YAN Feng
Chin. Phys. Lett. 2013, 30 (12):
128102
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DOI: 10.1088/0256-307X/30/12/128102
The charge-storage characteristics of charge trapping memory devices containing different sizes of Au nanocrystals (NCs) sandwiched by Al2O3 tunneling and blocking layers are studied. A strong impact of both Au NC size and inter-NC distance on the charge trapping capability of the devices is observed. The total surface area of Au NCs associated with Au NC size is supposed to be a key factor in the charge-storage capability, and the device with larger size of Au NCs and a suitable inter-NC distance will possess better charge trapping capability. Variable range hopping as the lateral charge loss mechanism is considered as the main reason for the decrease of the charge trapping capability when Au NCs grow and overlap neighbors.
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Eco-Friendly Phyto-Synthesis of Silver Nanoparticles Using Jatropha Seedcake Extract
Anjali Bose, Haresh Keharia, M. P. Deshpande
Chin. Phys. Lett. 2013, 30 (12):
128103
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DOI: 10.1088/0256-307X/30/12/128103
Phytosynthesis of metal nanoparticles is gaining importance due to their biocompatibility, low toxicity and eco-friendly nature. In the present study, an aqueous extract of Jatropha seedcake (JSC) is assessed as a reducing and stabilizing agent for the synthesis of silver nanoparticles (AgNPs). The maximum reduction of silver ions occur when 1 mM AgNO3 solution is treated with 0.1 volume fraction of JSC extract in boiling water bath for 10 min. The synthesis of AgNPs is monitored by the excitation of surface plasmon resonance using UV-vis spectrophotometry. The AgNPs are found to be mono-dispersed, spherical with average particle size of 10.48 ± 74 nm when analyzed by transmission electron microscopy. The selected area electron diffraction (SAED) ring pattern indicated the polycrystalline nature of the AgNPs. The x-ray diffraction data further confirm the presence of characteristic (111), (200), (220), (311) and (222) diffraction planes of face centered cubic structure, and the calculated lattice parameter comes out to be 4.083 ?. FTIR analysis reveals the involvement of proteins and phenols in reduction and stabilization of nanoparticles. The synthesized AgNPs have significant antibacterial action on both the Gram positive and negative bacteria.
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Frequency Gradient with Respect to Temperature for Determination of Classification of the Phase Response Curve
Yasuomi D. Sato
Chin. Phys. Lett. 2013, 30 (12):
128201
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DOI: 10.1088/0256-307X/30/12/128201
The interesting task here is to study the frequency-current (f–I) curve and phase response curve (PRC), subject to neural temperature variations, because the f–I curve and PRC are important measurements to understand dynamical mechanisms of generation of neural oscillations, and the neural temperature is widely known to significantly affect the oscillations. Nevertheless, little is discussed about how the temperature affects the f–I curve and PRC. In this study, frequencies of the neural oscillations, modulated with the temperature variations, are quantified with an average of the PRC. The frequency gradient with respect to temperature derived here gives clear classifications of the PRC, regardless of the form. It is also indicated that frequency decreases with an increase in temperature, resulted from bifurcation switching of the saddle-homoclinic to the saddle-node on an invariant circle.
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Magnetic-Particle-Composite-Medium-Filled Stacked-Spiral Inductors for Radio-Frequency CMOS Applications
ZHAN Jing, CAI Hua-Lin, CHEN Xiao, WANG Xin, FANG Qiang, YANG Yi, REN Tian-Ling, LIU Li-Tian, LI Xin-Xin, WANG Albert, YANG Chen
Chin. Phys. Lett. 2013, 30 (12):
128401
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DOI: 10.1088/0256-307X/30/12/128401
Magnetic-particle-composite-medium-filled stacked-spiral inductors for rf complementary metal oxide semiconductor (CMOS) applications in GHz are demonstrated. The new inductor features a nearly closed magnetic circuit loop, an optimized high-permeability and low-loss sub-1 μm magnetic particles' composite core, and a developed 0.18-μm CMOS-compatible device fabrication process. An equivalent circuit model with structural amplifying factors is proposed and modeled. The prototype of the 6-level stacked inductor with Co2Z magnetic-particles-composite-medium filling increases the inductance L by 50%, and quality factor Q by 37% at frequencies as high as 1 GHz, with high inductance density as 825 nH/mm2 and a reduced size area by 80% compared to the planar spiral inductor.
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Enhanced Performance in Perovskite Organic Lead Iodide Heterojunction Solar Cells with Metal-Insulator-Semiconductor Back Contact
HI Jiang-Jian, DONG Wan, XU Yu-Zhuan, LI Chun-Hui, LV Song-Tao, ZHU Li-Feng, DONG Juan, LUO Yan-Hong, LI Dong-Mei, MENG Qing-Bo, CHEN Qiang
Chin. Phys. Lett. 2013, 30 (12):
128402
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DOI: 10.1088/0256-307X/30/12/128402
Metal-insulator-semiconductor back contact has been employed for a perovskite organic lead iodide heterojunction solar cell, in which an ultrathin Al2O3 film as an insulating layer was deposited onto the CH3NH3PbI3 by atomic layer deposition technology. The light-to-electricity conversion efficiency of the devices is significantly enhanced from 3.30% to 5.07%. Further the impedance spectrum reveals that this insulating layer sustains part of the positive bias applied in the absorber region close to the back contact and decreases the carrier transport barrier, thus promoting transportation of carriers.
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The Nucleon Direct Urca Processes in a Cooling Neutron Star
XU Yan, LIU Guang-Zhou, LIU Cheng-Zhi, FAN Cun-Bo, WANG Hong-Yan, ZHU Ming-Feng, ZHAO En-Guang
Chin. Phys. Lett. 2013, 30 (12):
129501
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DOI: 10.1088/0256-307X/30/12/129501
In the relativistic mean field approximation, the relativistic energy losses of the nucleon direct Urca processes are studied in the degenerate baryon matter of neutron stars. We investigate the effects of hyperon degrees of freedom and the isovector scalar interaction which is considered by exchanging δ meson on the nucleon direct Urca processes in neutron star matter. The results indicate that the existence of hyperons decreases the abundance of protons and leptons and can sharply suppress the neutrino emissivity of the nucleon direct Urca processes, while it has only a little influence on the neutrino luminosity for a fixed neutron star whether δ mesons appear in a neutron star or not. However, the presence of δ mesons can result in obvious growth in the neutrino emissivity and luminosity which will speed up the cooling rate for the nonsuperfluid neutron star.
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47 articles
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