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Fidelity Tradeoff in Estimation of Partial Entanglement State with Local Operation and Classic Communication
ZHANG Sheng-Li, WANG-Kun, GUO Jian-Sheng, SHI Jian-Hong
Chin. Phys. Lett. 2015, 32 (07):
070302
.
DOI: 10.1088/0256-307X/32/7/070302
In quantum mechanics, there is no measurement process that could gain some information of an unknown quantum state without causing any disturbance. A tradeoff bound between the amount of information gain and the concomitant disturbance ? in the measurement process of a bipartite entangled state is actually ingrained. Such a bound is fundamental and closely connected with the entangled degree b. In this work, the bound for estimation of a partial entangled state with a local strategy is investigated. It is shown that, with local operation with classical communication, a monotonic change in the ?– picture will be spotted. This is due to the fact that the partial entanglement gradually becomes two individual qubits and, consequently, the optimal operation boils down to local operations. A quantum circuit which achieves the optimal tradeoff is also obtained.
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A High-Sensitivity Refractive-Index Sensor Based on Plasmonic Waveguides Asymmetrically Coupled with a Nanodisk Resonator
XIAO Li-Ping, WANG Fa-Qiang, LIANG Rui-Sheng, ZOU Shi-Wei, HU Miao
Chin. Phys. Lett. 2015, 32 (07):
070701
.
DOI: 10.1088/0256-307X/32/7/070701
A high-sensitivity plasmonic refractive-index sensor based on the asymmetrical coupling of two metal-insulator-metal waveguides with a nanodisk resonator is proposed and simulated in the finite-difference time domain. Both analytic and simulated results show that the resonance wavelengths of the sensor have an approximate linear relationship with the refractive index of the materials which are filled into the slit waveguides and the disk-shaped resonator. The working mechanism of this sensor is exactly due to the linear relationship, based on which the refractive index of the materials unknown can be obtained from the detection of the resonance wavelength. The measurement sensitivity can reach as high as 6.45×10 ?7, which is nearly five times higher than the results reported in the recent literature [ Opt. Commun. 300 (2013) 265]. With an optimum design, the sensing value can be further improved, and it can be widely applied into the biological sensing. The sensor working for temperature sensing is also analyzed.
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The Approach of Compensation of Air Refractive Index in Thermal Expansion Coefficients Measurement Based on Laser Feedback Interferometry
ZHENG Fa-Song, DING Ying-Chun, TAN Yi-Dong, LIN Jing, ZHANG Shu-Lian
Chin. Phys. Lett. 2015, 32 (07):
070702
.
DOI: 10.1088/0256-307X/32/7/070702
We present the thermal expansion coefficient (TEC) measurement technology of compensating for the effect of variations in the refractive index based on a Nd:YAG laser feedback system, the beam frequency is shifted by a pair of acousto-optic modulators and then the heterodyne phase measurement technique is used. The sample measured is placed in a muffle furnace with two coaxial holes opened on the opposite furnace walls. The measurement beams hit perpendicularly and coaxially on each surface of the sample. The reference beams hit on the reference mirror and the high-reflectivity mirror, respectively. By the heterodyne configuration and computing, the influences of the vibration, distortion of the sample supporter and the effect of variations in the refractive index are measured and largely minimized. For validation, the TECs of aluminum samples are determined in the temperature range of 298–748 K, confirming not only the precision within 5×10?7 K?1 and the accuracy within 0.4% from 298 K to 448 K but also the high sensitivity non-contact measurement of the lower reflectivity surface induced by the sample oxidization from 448 K to 748 K.
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The Analytical Potential Energy Function of NH Radical Molecule in External Electric Field
WU Dong-Lan, TAN Bin, WAN Hui-Jun, XIE An-Dong, DING Da-Jun
Chin. Phys. Lett. 2015, 32 (07):
073101
.
DOI: 10.1088/0256-307X/32/7/073101
The geometric structures of an NH radical in different external electric fields are optimized by using the density functional B3P86/cc-PV5Z method, and the bond lengths, dipole moments, vibration frequencies and IR spectrum are obtained. The potential energy curves are gained by the CCSD (T) method with the same basis set. These results indicate that the physical property parameters and potential energy curves may change with the external electric field, especially in the reverse direction electric field. The potential energy function of zero field is fitted by the Morse potential, and the fitting parameters are in good accordance with the experimental data. The potential energy functions of different external electric fields are fitted adopting the constructed potential model. The fitted critical dissociation electric parameters are shown to be consistent with the numerical calculation, and the relative errors are only 0.27% and 6.61%, hence the constructed model is reliable and accurate. The present results provide an important reference for further study of the molecular spectrum, dynamics and molecular cooling with Stark effect.
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A Precise Description of the Electronic Structures and Spin-Allowed Transition Properties of PF and Its Cation: All-Electron Configuration-Interaction Investigations Including Relativistic Effect
LI Qi-Nan, ZHAO Shu-Tao, ZHANG Xiao-Mei, LUO Wang, LI Rui, YAN Bing
Chin. Phys. Lett. 2015, 32 (07):
073103
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DOI: 10.1088/0256-307X/32/7/073103
The electronic structures of PF and PF+ are calculated with the high-level configuration interaction method. To improve the precision of calculations, the spin-orbit coupling effect, the scalar relativistic effect, and the Davidson correction(+Q) are also considered. The spectroscopic parameters of bound states are derived by the electronic structures of PF and PF+, which are in good accordance with the measurements. The transition dipole moments of spin-allowed transitions are evaluated, and the radiative lifetimes of several Λ–S states of PF and PF+ are obtained.
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Multiple Ionization of Argon Induced by Carbon Ions at 20–500 keV/u Energies
NIU Shu-Tong, LIU Wen-Biao, YANG Ai-Xiang, HAN Cheng-Zhi, HU Wei, WEN Zhi-Wen, GAO Zhi-Min, SHAO Jian-Xiong, CHEN Xi-Meng
Chin. Phys. Lett. 2015, 32 (07):
073401
.
DOI: 10.1088/0256-307X/32/7/073401
We measure the multiple ionization cross-section ratios Rk1 of Ar impacted by Cq+ (q=1–3) ions in the energy range of 20–500 keV/u. The measured ratios Rk1 increase with the projectile energy at lower energies, and reach the maximum at energies of 50–150 keV/u, then decrease for higher energies. We also use the classical over barrier ionization model to calculate the ratios Rk1, and the calculation results are in good agreement with the data, which suggest that the multiple ionization process is described by the sequential over-barrier ionization process.
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Design of an Electrically Written and Optically Read Non-volatile Memory Device Employing BiFeO3/Au Heterostructures with Strong Absorption Resonance
XIAO Peng-Bo, ZHANG Wei, QU Tian-Liang, HUANG Yun, HU Shao-Min
Chin. Phys. Lett. 2015, 32 (07):
074204
.
DOI: 10.1088/0256-307X/32/7/074204
Exploiting new concepts for dense, fast, and nonvolatile random access memory with reduced energy consumption is a significant issue for information technology. Here we design an 'electrically written and optically read' information storage device employing BiFeO3/Au heterostructures with strong absorption resonance. The electro-optic effect is the basis for the device design, which arises from the strong absorption resonance in BiFeO3/Au heterostructures and the electrically tunable significant birefringence of the BiFeO3 film. We first construct a simulation calculation of the BiFeO3/Au structure spectrum and identify absorption resonance and electro-optical modulation characteristics. Following a micro scale partition, the surface reflected light intensity of different polarization units is calculated. The results depend on electric polarization states of the BiFeO3 film, thus BiFeO3/Au heterostructures can essentially be designed as a type of electrically written and optically read information storage device by utilizing the scanning near-field optical microscopy technology based on the conductive silicon cantilever tip with nanofabricated aperture. This work will shed light on information storage technology.
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Single Mode 2 μm GaSb Based Laterally Coupled Distributed Feedback Quantum-Well Laser Diodes with Metal Grating
SONG Yu-Zhi, ZHANG Yu, SONG Jia-Kun, LI Kang-Wen, ZHANG Zu-Yin, XU Yun, SONG Guo-Feng, CHEN Liang-Hui
Chin. Phys. Lett. 2015, 32 (07):
074206
.
DOI: 10.1088/0256-307X/32/7/074206
Room-temperature operation of a GaSb based laterally coupled distributed feedback quantum-well laser diode emitting at 2 μm is demonstrated. The device exhibits single longitudinal mode characteristic as a result of the first order Cr-Bragg gratings alongside the narrow ridge waveguide. We design the laser structure to obtain a critical coupling condition corresponding to a coupling coefficient of 12 cm?1. For a 1-mm-long uncoated laser diode with a 3-μm-wide stripe, a single mode output spectrum with side mode suppression ratio as high as 28.5 dB is achieved, and the maximum single mode continuous-wave output power is about 11 mW at room temperature.
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A Linearly Polarized Ho:YAG Laser at 2.09 μm with Corner Cube Cavity Pumped by Tm:YLF Laser
WU Jing, JU You-Lun, DAI Tong-Yu, LIU Wei, YAO Bao-Quan, WANG Yue-Zhu
Chin. Phys. Lett. 2015, 32 (07):
074207
.
DOI: 10.1088/0256-307X/32/7/074207
A linearly polarized operation Ho:YAG laser at 2090.5 nm with a corner cube cavity is demonstrated. A polarizer with high reflectivity for the s-polarized light at the laser wavelength is employed to achieve a linearly polarized laser. In the same case of resonator length, the corner cube can be used to cut the volume of the Ho:YAG laser and to enhance the stability of the system. The maximum linearly polarized output power of 5.8 W is achieved at the absorbed pump power of 23.3 W, corresponding to a slope efficiency of 29.7%, and the optical-optical conversion efficiency is around 24.9%. The M2 factors of the 2.09 μm laser are 2.4 and 1.2 along the horizontal and vertical directions, respectively.
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Direct Laser-Driven Quasi-Isentropic Compression on HEAVEN-I Laser
ZHANG Pin-Liang, TANG Xiu-Zhang, LI Ye-Jun, WANG Zhao, TIAN Bao-Xian, YIN Qian, LU Ze, XIANG Yi-Huai, GAO Zhi-Xing, LI Jing, HU Feng-Ming, GONG Zi-Zheng
Chin. Phys. Lett. 2015, 32 (07):
075201
.
DOI: 10.1088/0256-307X/32/7/075201
The HEAVEN-I laser is used for direct drive quasi-isentropic compression up to ~18 GPa in samples of aluminum without being temporal pulse shaped. The monotonically increasing loading is with a rise time over 17 ns. The compression history is well reproduced by the 1D radiation hydrodynamics simulation. We find that a small shock precursor where the backward integration method cannot process is formed at the beginning of illumination. We compare the loading process of HEAVEN-I with the typical profile (concave down, prefect pulse shape), the results show that a typical profile can obtain more slowly rising and higher pressure, and the shock precursor has significant effects on temperature and entropy production. However, it is demonstrated that the HEAVEN-I is an excellent optical source for direct laser-driven quasi-isentropic compression, even if it produces more temperature rise and entropy than the typical profile.
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Modeling of the Distinctive Ground-State Atomic Oxygen Density Profile in Plasma Needle Discharge at Atmospheric Pressure
QIAN Mu-Yang, YANG Cong-Ying, CHEN Xiao-Chang, NI Geng-Song, LIU-Song, WANG De-Zhen
Chin. Phys. Lett. 2015, 32 (07):
075202
.
DOI: 10.1088/0256-307X/32/7/075202
A two-dimensional coupled model of neutral gas flow and plasma dynamics is presented to explain the two distinctive patterns of ground-state atomic oxygen density profiles that have been observed experimentally in the helium plasma needle discharge. When the gas flow rate is 0.25 standard liter per minute (SLM), the discharge is substantially sustained by the electron impact ionization of air near a dielectric surface, corresponding to the radial density peaks along the axis of the symmetry. However, as the flow rate is 1.1 SLM, Penning ionization between helium metastables and surrounding air dominates the ionization reactions and peaks at an off-center position (r=0.9 mm), which indicates the ring-shaped density distribution. The critical feeding gas flow rate is found to be around 0.4 SLM. The peak density is on the order of 1020 m?3 in our case. Previous reports of a flow-dependent bacterial killing pattern and ground-state atomic oxygen measurement support our simulation results.
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TEM Characterization of Helium Bubbles in T91 and MNHS Steels Implanted with 200 keV He Ions at Different Temperatures
WANG Ji, GAO Xing, WANG Zhi-Guang, WEI Kong-Fang, YAO Cun-Feng, CUI Ming-Huan, SUN Jian-Rong, LI Bing-Sheng, PANG Li-Long, ZHU Ya-Bin, LUO Peng, CHANG Hai-Long, ZHANG Hong-Peng, ZHU Hui-Ping, WANG Dong, DU Yang-Yang, XIE Er-Qing
Chin. Phys. Lett. 2015, 32 (07):
076101
.
DOI: 10.1088/0256-307X/32/7/076101
Modified novel high silicon steel (MNHS, a newly developed reduced-activation martensitic alloy) and commercial alloy T91 are implanted with 200 keV He2+ ions to a dose of 5×1020 ions/m2 at 300, 450 and 550°C. Transmission electron microscopy (TEM) is used to characterize the size and morphology of He bubbles. With the increase of the implantation temperature, TEM observations indicate that bubbles increase in size and the proportion of 'brick shaped' cuboid bubbles increases while the proportion of polyhedral bubbles decreases in both the steel samples. For the samples implanted at the same temperature, the average size of He bubbles in MNHS is smaller than that in T91. This might be due to the abundance of boundaries and precipitates in MNHS, which provide additional sites for the trapping of He atoms, thus reduce the susceptibility of MNHS to He embrittlement.
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Discontinuous Precipitation Reaction Front of Cellular Recrystallization for a Single-Crystal Superalloy Studied by Electron Microscopy
ZHUO Long-Chao, LIANG Shu-Hua, WANG Feng, LIU Yu-Feng, XIONG Ji-Chun
Chin. Phys. Lett. 2015, 32 (07):
076102
.
DOI: 10.1088/0256-307X/32/7/076102
Combining analytical transmission electron microscopy systematic tilting, scanning transmission electron microscopy mapping and nano-beam electron diffraction operations, we obtain direct experimental proofs on the boundary type, elemental distribution and structure of the cellular recrystallization reaction front for a single-crystal superalloy. It is demonstrated that the cellular recrystallization reaction front usually corresponds to coincidence site lattice boundaries, and a thin layer of γ-forming elements such as Re, Cr, Mo and Co invariably exists in the direct reaction front. Furthermore, the thin layer with γ-forming elements is proved to be γ phase, with the same orientation as the neighboring original matrix.
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A Novel Method of Fabricating Flexible Transparent Conductive Large Area Graphene Film
FAN Tian-Ju, YUAN Chun-Qiu, TANG Wei, TONG Song-Zhao, LIU Yi-Dong, HUANG Wei, MIN Yong-Gang, Arthur J. Epstein
Chin. Phys. Lett. 2015, 32 (07):
076802
.
DOI: 10.1088/0256-307X/32/7/076802
We fabricate flexible conductive and transparent graphene films on position-emission-tomography substrates and prepare large area graphene films by graphite oxide sheets with the new technical process. The multi-layer graphene oxide sheets can be chemically reduced by HNO3 and HI to form a highly conductive graphene film on a substrate at lower temperature. The reduced graphene oxide sheets show a high conductivity sheet with resistance of 476 Ω/sq and transmittance of 76% at 550 nm (6 layers). The technique used to produce the transparent conductive graphene thin film is facile, inexpensive, and can be tunable for a large area production applied for electronics or touch screens.
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Electronic Structure and Optical Properties in Uranium Dioxide: the First Principle Calculations
SUI Peng-Fei, DAI Zhen-Hong, ZHANG Xiao-Ling, ZHAO Yin-Chang
Chin. Phys. Lett. 2015, 32 (07):
077101
.
DOI: 10.1088/0256-307X/32/7/077101
We report a study of the electronic structure and optical properties of uranium dioxide (UO2) based on the ab-initio density-functional theory and using the generalized gradient approximation. To correctly describe the strong correlation between 5f electrons of a uranium atom, we employ the on-site Hubbard U correction term and optimize the correlation parameter of the bulk uranium dioxide. Then we give the structural and electronic properties of the ground state of uranium dioxide. Based on the accurate electronic structure, we calculate the complex dielectric function of UO2 and the related optical properties, such as reflectivity, refractive index, extinction index, energy loss spectra, and absorption coefficient.
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Memory Behaviors Based on ITO/Graphene Oxide/Al Structure
YI Ming-Dong, GUO Jia-Lin, HU Bo, XIA Xian-Hai, FAN Qu-Li, XIE Ling-Hai, HUANG Wei
Chin. Phys. Lett. 2015, 32 (07):
077201
.
DOI: 10.1088/0256-307X/32/7/077201
We investigate the memory properties of the ITO/graphene oxide/Al diodes. It is found that the devices show different memory behaviors with the diverse geometry and thickness of Al. When the thickness of the Al electrode is relatively thick, the device of the cross-point Al electrode shows a three-level memory effect, and the counterpart device of the cross-bar Al electrode exhibits a volatile static random access memory effect. When the thickness of the Al electrode is thinner, the above devices demonstrate a flash memory effect. The different memory behaviors of ITO/GO/Al diodes are ascribed to the mode and degree of reduction and oxidation of GO.
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Effects of Nonparabolicity on Electron Thermopower of Size-Quantized Semiconductor Films
BAHSHELI Guliyev, AKBAR Barati Chiyaneh, NOVRUZ Bashirov, GENBER Kerimli
Chin. Phys. Lett. 2015, 32 (07):
077204
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DOI: 10.1088/0256-307X/32/7/077204
Effects of nonparabolicity of energy band on thermopower, in-plane effective mass and Fermi energy are investigated in size-quantized semiconductor films in a strong while non-quantized magnetic field. We obtain the expressions of these quantities as functions of thickness, concentration and nonparabolicity parameter. The influence of nonparabolicity is studied for degenerate and non-degenerate electron gases, and it is shown that nonparabolicity changes the character of thickness and the concentration dependence of thermopower, in-plane effective mass and Fermi energy. Moreover, the magnitudes of these quantities significantly increase with respect to the nonparabolicity parameter in the case of strong nonparabolicity in nano-films. The concentration dependence is also studied, and it is shown that thermopower increases when the concentration decreases. These results are in agreement with the experimental data.
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AlGaN Channel High Electron Mobility Transistors with an AlxGa1?xN/GaN Composite Buffer Layer
LI Xiang-Dong, ZHANG Jin-Cheng, ZOU Yu, MA Xue-Zhi, LIU Chang, ZHANG Wei-Hang, WEN Hui-Juan, HAO Yue
Chin. Phys. Lett. 2015, 32 (07):
077205
.
DOI: 10.1088/0256-307X/32/7/077205
We report an AlGaN channel high electron mobility transistor (HEMT) on a sapphire substrate with a 1000-nm AlxGa1?xN (x=0–0.18)/GaN composite buffer layer. With a significant improvement of crystal quality, the device features a high product of ns?μn. The AlGaN channel HEMTs presented show improved performance with respect to the conventional AlGaN channel HEMTs, including the on-resistance reduced from 31.2 to 8.1 Ω?mm, saturation drain current at 2 V gate bias promoted from 218 to 540 mA/mm, peak transconductance at 10 V drain bias promoted from 100 to a state-of-the-art value of 174 mS/mm, and reverse gate leakage current reduced from 1.85×10?3 to 2.15×10?5 mA/mm at VGD=?20 V.
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Improvement of Performance of Organic Light-Emitting Diodes with Both a MoO3 Hole Injection Layer and a MoO3 Doped Hole Transport Layer
LIU Wei, LIU Guo-Hong, LIU Yong, LI Bao-Jun, ZHOU Xiang
Chin. Phys. Lett. 2015, 32 (07):
077206
.
DOI: 10.1088/0256-307X/32/7/077206
We improve the performance of organic light-emitting diodes (OLEDs) with both a MoO3 hole injection layer (HIL) and a MoO3 doped hole transport layer (HTL), and present a systematical and comparative investigation on these devices. Compared with OLEDs with only MoO3 HIL or MoO3 doped HTL, OLEDs with both MoO3 HIL and MoO3 doped HTL show superior performance in driving voltage, power efficiency, and stability. Based on the typical NPB/Alq3 heterojunction structure, OLEDs with both MoO3 HIL and MoO3 doped HTL show a driving voltage of 5.4 V and a power efficiency of 1.41 lm/W for 1000 cd/m2, and a lifetime of around 0.88 h with an initial luminance of 5268 cd/m2 under a constant current of 190 mA/cm2 operation in air without encapsulation. While OLEDs with only MoO3 HIL or MoO3 doped HTL show higher driving voltages of 6.4 V or 5.8 V and lower power efficiencies of 1.20 lm/W or 1.34 lm/W for 1000 cd/m2, and a shorter lifetime of 0.33 or 0.60 h with an initial luminance of around 5122 or 5300 cd/m2 under a constant current of 200 or 216 mA/cm2 operation. Our results demonstrate clearly that using both MoO3 HIL and MoO3 doped HTL is a simple and effective approach to simultaneously improve both the hole injection and transport efficiency, resulting from the lowered energy barrier at the anode interface and the increased hole carrier density in MoO3 doped HTL.
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Characterization of Ge Doping on Sb2Te3 for High-Speed Phase Change Memory Application
ZHU Yue-Qin, ZHANG Zhong-Hua, SONG San-Nian, XIE Hua-Qing, SONG Zhi-Tang, SHEN Lan-Lan, LI Le, WU Liang-Cai, LIU Bo
Chin. Phys. Lett. 2015, 32 (07):
077302
.
DOI: 10.1088/0256-307X/32/7/077302
The phase change material of Ge-doped Sb2Te3 is shown to have higher crystallization temperature and better thermal stability compared with pure Sb2Te3. Ge0.11Sb2Te3 alloys are considered to be a potential candidate for phase change random access memories, as proved by a higher crystallization temperature, a better data retention ability, and a faster switching speed in comparison with those of Ge2Sb2Te5. In addition, Ge0.11Sb2Te3 presents extremely rapid reverse switching speed (10 ns), and up to 105 programming cycles are obtained with stable set and reset resistances.
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The Effect of Oxygen Partial Pressure during Active Layer Deposition on Bias Stability of a-InGaZnO TFTs
HUANG Xiao-Ming, WU Chen-Fei, LU Hai, REN Fang-Fang, ZHU Hong-Bo, WANG Yong-Jin
Chin. Phys. Lett. 2015, 32 (07):
077303
.
DOI: 10.1088/0256-307X/32/7/077303
The effect of oxygen partial pressure (PO2) during the channel layer deposition on bias stability of amorphous indium-gallium-zinc oxide (a-IGZO) thin film transistors (TFTs) is investigated. As PO2 increases from 10% to 30%, it is found that the device shows enhanced bias stress stability with significantly reduced threshold voltage drift under positive gate bias stress. Based on the x-ray photoelectron spectroscopy measurement, the concentration of oxygen vacancies (OV) within the a-IGZO layer is suppressed by increasing PO2. Meanwhile, the low-frequency noise analysis indicates that the average trap density near the channel/dielectric interface continuously drops with increasing PO2. Therefore, the improved interface quality with increasing PO2 during the channel layer deposition can be attributed to the reduction of interface OV-related defects, which agrees with the enhanced bias stress stability of the a-IGZO TFTs.
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Common Base Four-Finger InGaAs/InP Double Heterojunction Bipolar Transistor with Maximum Oscillation Frequency 535 GHz
NIU Bin, WANG Yuan, CHENG Wei, XIE Zi-Li, LU Hai-Yan, CHANG Long, XIE Jun-Ling
Chin. Phys. Lett. 2015, 32 (07):
077304
.
DOI: 10.1088/0256-307X/32/7/077304
A common base four-finger InGaAs/InP double heterojunction bipolar transistor with 535 GHz fmax by using the 0.5 μm emitter technology is fabricated. Multi-finger design is used to increase the input current. Common base configuration is compared with common emitter configuration, and shows a smaller K factor at high frequency span, indicating a larger breakpoint frequency of maximum stable gain/maximum available gain (MSG/MAG) and thus a higher gain near the cut-off frequency, which is useful in THz amplifier design.
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Doping Induced Gap Anisotropy in Iron-Based Superconductors: a Point-Contact Andreev Reflection Study of BaFe2−xNixAs2 Single Crystals
ZHU Jun, WANG Zhao-Sheng, WANG Zhen-Yu, HOU Xing-Yuan, LUO Hui-Qian, LU Xing-Ye, LI Chun-Hong, SHAN Lei, WEN Hai-Hu, REN Cong
Chin. Phys. Lett. 2015, 32 (07):
077401
.
DOI: 10.1088/0256-307X/32/7/077401
We report a systematic investigation on c-axis point-contact Andreev reflection (PCAR) in BaFe2−xNixAs2 superconducting single crystals from underdoped to overdoped regions (0.075≤x≤0.15). At low temperatures, an in-gap sharp peak at low-bias voltage is observed in PCAR for overdoped samples, in contrast to the case of underdoped junctions, in which an in-gap plateau is observed. The variety of the conductance spectra with doping can be well described by using a generalized Blonder–Tinkham–Klapwijk formalism with an angle-dependent gap. This gap shows a clear crossover from a nodeless in the underdoped side to a nodal feature in the overdoped region. This result provides evidence of the doping-induced evolution of the superconducting order parameter when the inter-pocket and intra-pocket scattering are tuned through doping, as expected in the s± scenario.
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Surface State Bands in Superconducting (PtxIr1?x)Te2
KONG Wan-Dong, MIAO Hu, QIAN Tian, WANG Zhi-Jun, XU Gang, FANG Ai-Fang, HUANG Yao-Bo, ZHANG Peng, SHI Xun, FANG Zhong, DAI Xi, RICHARD Pierre, WANG Nan-Lin, DING Hong
Chin. Phys. Lett. 2015, 32 (07):
077402
.
DOI: 10.1088/0256-307X/32/7/077402
Angle-resolved photoemission spectroscopy is performed to study the bulk and surface electronic structures of non-superconducting IrTe2 and superconducting Pt0.05Ir0.95Te2. In addition to the bulk electronic bands predicted by the local density approximation calculations, we observe two Dirac cone-like bands at the Brillouin zone center, which are non-dispersive along kz, suggesting that the extra bands are surface state bands. As the experimental results are well consistent with the ab initio calculations of surface states, the parity analysis proves that these surface state bands are topologically trivial and thus exclude (PtxIr1?x)Te2 as a possible topological superconductor candidate.
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Optical Properties and Surface Morphology of Thin Silver Films Deposited by Thermal Evaporation
ZHOU Ming, LI Yao-Peng, ZHOU Sheng, LIU Ding-Quan
Chin. Phys. Lett. 2015, 32 (07):
077802
.
DOI: 10.1088/0256-307X/32/7/077802
Thin silver films with different thicknesses are deposited by thermal evaporation, and the Drude–Lorentz mode is used to describe the optical properties of samples measured by an ellipsometer, and the thickness uniqueness analysis and reflection spectrum testing are used to verify the simulated results. We obtain the surface morphologies of the samples using the scanning electron microscopy, and calculate the relationship of reflectance with film thickness at wavelength 800 nm using the Mathcad software. Moreover, the effective medium approximation mode is used to explain the differences of wavelength-dependent n and k as the thickness changes. As the silver film thickness decreases, the optical constant changes regularly, and the films show flat surface, small cracks, discontinuous and island distribution, respectively, while n and k of the island distributed silver film have an intersection point in the visible spectrum. Our experiments provide an in-depth research for the ultra-thin silver film under thermal evaporation deposition, and will be helpful for its application in multilayers and plasmonic devices.
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Rice Husk Templated Mesoporous ZnO Nanostructures for Ethanol Sensing at Room Temperature
M. Chitra, K. Uthayarani, N. Rajasekaran, N. Neelakandeswari, E. K. Girija, D. Pathinettam Padiyan
Chin. Phys. Lett. 2015, 32 (07):
078101
.
DOI: 10.1088/0256-307X/32/7/078101
Mesoporous zinc oxide nanostructures are successfully synthesized via the sol-gel route by using a rice husk as the template for ethanol sensing at room temperature. The structure and morphology of the nanostructures are characterized by x-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and nitrogen adsorption–desorption analyses. The mechanism for the growth of zinc oxide nanostructures over the biotemplate is proposed. SEM and TEM observations also reveal the formation of spherical zinc oxide nanoparticles over the interwoven fibrous network. Multiple sized pores having pore diameter ranging from 10–40 nm is also evidenced from the pore size distribution plot. The larger surface area and porous nature of the material lead to high sensitivity (40.93% for 300 ppm of ethanol), quick response (42 s) and recovery (40 s) towards ethanol at 300 K. The porous nature of the interwoven fibre-like network affords mass transportation of ethanol vapor, which results in faster surface accessibility, and hence it acts as a potential candidate for ethanol sensing at room temperature.
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Glitch Crisis or Not: a Microscopic Study
LI Ang
Chin. Phys. Lett. 2015, 32 (07):
079701
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DOI: 10.1088/0256-307X/32/7/079701
The problem of glitch crisis has been a great deal of debate recently. It might challenge the standard two-component model, where glitches are thought to be triggered by the sudden unpinning of superfluid vortices in the neutron-star crust. It says that due to crustal entrainment the amount of superfluid in the crust cannot explain the changes in angular momentum required to account for the glitches. However, the argument of this crisis is based on the assumption that the core superfluid is completely coupled to the crust when a glitch happens. The fraction of the coupled core part is actually a quite uncertain problem so far. In this work, we take three possible values for the fraction of the coupled core part and study in detail the crisis problem for a 1.4 M? canonical star, based on a microscopic equation of state for the neutron star's core using the Brueckner–Hartree–Fock approach. For this purpose, two requisite parameters are chosen as follows: the core-crust transition pressure is in the range of Pt=0.2–0.65 MeV/fm3, and the fractional crust radius ΔR/R=0.082 based on experiments. To account for the possibility of a heavier star, a larger value of ΔR/R=0.15 is also chosen for comparison. Then we take the crustal entrainment into account, and evaluate the predictions for the fractional moment of inertia at various conditions. The results show that there is commonly no such glitch crisis, as long as one considers only a small fraction of the core neutron superfluid will contribute to the charged component of the star. Only if the core-crust transition pressure is determined to be a low value, the crisis problem may appear for complete core-crust coupling. This is consistent with a recent study in a phenomenological model.
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56 articles
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