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Volume 34 Issue 11
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GENERAL
Non-Relativistic Treatment of a Generalized Inverse Quadratic Yukawa Potential
Oluwatimilehin Oluwadare, Kayode Oyewumi
Chin. Phys. Lett. 2017, 34 (11): 110301 .   DOI: 10.1088/0256-307X/34/11/110301
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A bound state solution is a quantum state solution of a particle subjected to a potential such that the particle's energy is less than the potential at both negative and positive infinity. The particle's energy may also be negative as the potential approaches zero at infinity. It is characterized by the discretized eigenvalues and eigenfunctions, which contain all the necessary information regarding the quantum systems under consideration. The bound state problems need to be extended using a more precise method and approximation scheme. This study focuses on the non-relativistic bound state solutions to the generalized inverse quadratic Yukawa potential. The expression for the non-relativistic energy eigenvalues and radial eigenfunctions are derived using proper quantization rule and formula method, respectively. The results reveal that both the ground and first excited energy eigenvalues depend largely on the angular momentum numbers, screening parameters, reduced mass, and the potential depth. The energy eigenvalues, angular momentum numbers, screening parameters, reduced mass, and the potential depth or potential coupling strength determine the nature of bound state of quantum particles. The explored model is also suitable for explaining both the bound and continuum states of quantum systems.
Thermodynamic Performance of Three-Terminal Hybrid Quantum Dot Thermoelectric Devices
Zhi-Cheng Shi, Jing Fu, Wei-Feng Qin, Ji-Zhou He
Chin. Phys. Lett. 2017, 34 (11): 110501 .   DOI: 10.1088/0256-307X/34/11/110501
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We propose four different models of three-terminal quantum dot thermoelectric devices. From general thermodynamic laws, we examine the reversible efficiencies of the four different models. Based on the master equation, the expressions for the efficiency and power output are derived and the corresponding working regions are determined. Moreover, we particularly analyze the performance of a three-terminal hybrid quantum dot refrigerator. The performance characteristic curves and the optimal performance parameters are obtained. Finally, we discuss the influence of the nonradiative effects on the optimal performance parameters in detail.
Computed Tidal Relativistic Red-Shifts of Frequency Standards on Earth and in Space Stations
Wei Zhuang, Fang Fang, Shao-Kai Wang, Yang Zhao, Tian-Chu Li
Chin. Phys. Lett. 2017, 34 (11): 110601 .   DOI: 10.1088/0256-307X/34/11/110601
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Frequencies of frequency standards are shifted by the local static gravity red shifts and also modulated by the tidal relativistic red shifts. We compute the tidal relativistic red shifts using a time-domain method and present the numerical results for the National Institute of Metrology (NIM) in Beijing, Laboratoire National de Métrologie et Essais-Système de Références Temps-Espace (LNE-SYRTE) in Paris and Physikalisch-Technische Bundesanstalt (PTB) in Braunschweig. The differences of the tidal relativistic red shift approach as large as $1.1\times10^{-16}$ when frequency standards at NIM are compared with those at SYRTE and PTB. Moreover, the tidal relativistic red shifts of frequency standards in space stations are also computed.
ATOMIC AND MOLECULAR PHYSICS
Role of XUV Photons in Atomic High-Order Above-Threshold Ionization Processes in IR+XUV Two-Color Laser Fields
Kui Zhang, Min Liu, Bing-Bing Wang, Ying-Chun Guo, Zong-Chao Yan, Jing Chen, Xiao-Jun Liu
Chin. Phys. Lett. 2017, 34 (11): 113201 .   DOI: 10.1088/0256-307X/34/11/113201
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We investigate the above-threshold ionization of an atom in a combined infrared (IR) and extreme ultraviolet (XUV) two-color laser field and focus on the role of XUV field in the high-order above-threshold ionization (HATI) process. It is demonstrated that, in stark contrast to previous studies, the XUV laser may play a significant role in atomic HATI process, and in particular, the XUV laser can accelerate the ionized electron in a quantized way during the collision between the electron and its parent ion. This process cannot be explained by the classical three-step model. Our results indicate that the previously well-established concept that HATI is an elastic recollision process is broken down.
FUNDAMENTAL AREAS OF PHENOMENOLOGY(INCLUDING APPLICATIONS)
Unified Analysis for Calculating the Incoherent Spontaneous Emission of Cooperative Radiations
Hesham Fares, Enrica Chiadroni
Chin. Phys. Lett. 2017, 34 (11): 114101 .   DOI: 10.1088/0256-307X/34/11/114101
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A unified analysis is presented to calculate the incoherent spontaneous power of cooperative radiations based on self-amplified spontaneous emission. Using quantum mechanical tools, we derive analytical expressions for the incoherent spontaneous power of undulator and Cherenkov free-electron lasers (FELs). The undulator and Cherenkov FELs are considered as two different examples for the radiation that accumulate cooperatively. In the case of the undulator FEL, we show an excellent agreement between an expression for the incoherent radiation power derived in the present work and that obtained using a completely different approach [Phys. Rev. E 65 (2002) 026501]. For the Cherenkov radiation, we demonstrate a satisfactory agreement between the incoherent power predicted in our analysis and previous experimental results.
Dual-Wavelength Passively Q-Switched Ytterbium-Doped Fiber Laser Based on Aluminum Oxide Nanoparticle Saturable Absorbers
S. K. M. Al-Hayali, S. Selleri, A. H. Al-Janabi
Chin. Phys. Lett. 2017, 34 (11): 114201 .   DOI: 10.1088/0256-307X/34/11/114201
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We report on generation of a dual-wavelength, all-fiber, passively Q-switched ytterbium-doped fiber laser using aluminum oxide nanoparticle (Al$_{2}$O$_{3}$-NP) thin film. A thin film of Al$_{2}$O$_{3}$ was prepared by embedding Al$_{2}$O$_{3}$-NPs into a polyvinyl alcohol (PVA) as a host polymer, and then inserted between two fiber ferrules to act as a saturable absorber (SA). By incorporating the Al$_{2}$O$_{3}$-PVA SA into the laser cavity, a stable dual-wavelength pulse output centered at 1050 and 1060.7 nm is observed at threshold pump power of 80 mW. As the pump power is gradually increased from 80 to 300 mW, the repetition rate of the generated pulse increases from 16.23 to 59 kHz, while the pulse width decreases from 19 to 6 μs. To the best of our knowledge, this is the first demonstration for this type of SA operating in the 1 μm region.
Generation of 2.5μm and 4.6μm Dispersive Waves in Kagome Photonic Crystal Fiber with Plasma Production
Tian-Qi Zhao, Meng Li, Dong Wei, Xin Ding, Gui-Zhong Zhang, Jian-Quan Yao
Chin. Phys. Lett. 2017, 34 (11): 114202 .   DOI: 10.1088/0256-307X/34/11/114202
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We report our numerical simulation on dispersive waves (DWs) generated in the Kr-filled Kagome hollow-core photonic crystal fiber, by deploying the unidirectional pulse propagation equation. Relatively strong dispersive waves are simultaneously generated at 2.5 μm and 4.6 μm. It is deciphered that the interplay between plasma currents due to Kr ionization and nonlinear effects plays a key role in DW generation. Remarkably, this kind of DW generation is corroborated by the plasma-corrected phase-matching condition.
Active Anomalous Transmission and Its Application in Compensating Waveform Distortions
Chun Wang, Lei Chen, Shan Qiao, Yu-Zhou Shen, An-Jie Zhu, De-Xin Ye, Chang-Zhi Li, Li-Xin Ran
Chin. Phys. Lett. 2017, 34 (11): 114203 .   DOI: 10.1088/0256-307X/34/11/114203
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In theory, engineered anomalous transmission in passive materials and waveguide devices can be used to compensate for waveform distortions. However, they suffer from inherent dissipation. Recently, active non-Foster elements with imaginary immittance monotonically decreasing with frequency have shown important potentials in broadening bandwidths of electromagnetic devices. So far, they are implemented based on negative impedance convertors (NICs) loaded with Foster devices. This makes them intrinsically one-port elements and thus cannot be used to compensate for distortions of signals. We construct a two-port network with a non-Foster transmission coefficient based on an unconventional use of NICs. Simulation and experiments show that it can compensate for extremely distorted signals. The proposed method can be used to broaden existing applications in different areas such as antennas, circuits and systems, and physical-layer signal processing.
Invisible Visual Cryptography
Yi-Shi Shi, Xiu-Bo Yang
Chin. Phys. Lett. 2017, 34 (11): 114204 .   DOI: 10.1088/0256-307X/34/11/114204
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We propose to realize visual cryptography in an indirect way with the help of diffractive optics, the pure-amplitude keys being substituted with the phase-only keys that are invisible for common-used intensity detectors, leading to the significantly enhanced security and improved usability for practice. Three typical realizations are provided by using static or dynamic diffractive optical elements, and the new concept of invisible visual cryptography (IVC) may be established. This concept is demonstrated by a compact opto-electronic system with only one spatial light modulator within time-delayed exposure, maintaining the fast speed of decryption and no requirement to the calculation of decryption in conventional visual cryptography. Further, IVC shows the immunity to noises and good information capacity, which is partly inherited from diffractive optics. IVC might suggest a new strategy for visual cryptography with the respective of diverse realizations, such as opto-electronic or even bio-chemical or other methods.
Hybrid Long-Period Fiber Grating with Multimode Fiber Core for Refractive Index Measurement
Min Shao, Xue-Guang Qiao, Xue-Liang Ren, De-Xing Yang
Chin. Phys. Lett. 2017, 34 (11): 114205 .   DOI: 10.1088/0256-307X/34/11/114205
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A refractive index (RI) sensor based on hybrid long-period fiber grating (LPFG) with multimode fiber core (MMFC) is proposed and demonstrated. The surrounding RI can be determined by monitoring the separation between the resonant wavelengths of the LPFG and MMFC since the resonant wavelengths of the LPFG and MMFC will shift in opposite directions when the surrounding RI changes. Experimental results show that the sensor possesses an enhanced sensitivity of 526.92 nm/RIU in the RI range of 1.387–1.394 RIU. The response to the temperature is also discussed.
Propagation Properties of Backward Lamb Waves in Plate Investigated by Dynamic Photoelastic Technique
Zhong-Tao Hu, Zhi-Wu An, Guo-Xuan Lian, Xiao-Min Wang
Chin. Phys. Lett. 2017, 34 (11): 114301 .   DOI: 10.1088/0256-307X/34/11/114301
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The dynamic photoelastic technique is employed to visualize and quantify the propagation properties of backward Lamb waves in a plate. Higher energy leakage of second-order symmetric backward wave mode S$_{\rm 2b}$ in contrast to third-order anti-symmetric backward mode A$_{\rm 3b}$ is shown by the dispersion curve of a plate immersed in water, and then verified by experiments. To avoid the considerable high leakage, the plate is placed in air, both group and phase velocities of modes S$_{\rm 2b}$ and A$_{\rm 3b}$ in the glass plate are experimentally measured. In comparison with the theoretical values, less than 5% errors are found in experiments.
Effect of Thermal Convection on Density Segregation in Binary Granular Gases with Dissipative Lateral Walls
Rui Li, Jie Li, Wei Dai, Mu-Qing Chen
Chin. Phys. Lett. 2017, 34 (11): 114501 .   DOI: 10.1088/0256-307X/34/11/114501
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Molecular dynamics simulations are employed to investigate the effect of thermal convection induced only by dissipative lateral walls on density segregation of the strongly driven binary granular gases under low gravity conditions. It is found that the thermal convection due to dissipative lateral walls has significant influence on the segregation intensity of the system. The dominant factor in determining the degree of segregation achieved by the system is found to be the relative convection rate between differing species. Moreover, a qualitative explanation is proposed for the relationship between the thermal convection due to dissipative lateral walls and the observed segregation intensity profiles.
CONDENSED MATTER: STRUCTURE, MECHANICAL AND THERMAL PROPERTIES
Synthesis of Different TiO$_{2}$ Nanostructures and Their Physical Properties
T. Hoseinzadeh, Z. Ghorannevis, M. Ghoranneviss, M. K. Salem, A. H. Sari
Chin. Phys. Lett. 2017, 34 (11): 116101 .   DOI: 10.1088/0256-307X/34/11/116101
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Titanium dioxide (TiO$_{2}$) nanosheet, nanorod and nanotubes are synthesized using chemical vapor deposition (CVD) and anodizing processes. TiO$_{2}$ nanosheets are grown on Ti foil which is coated with Au catalyst in CVD, TiO$_{2}$ nanorods are synthesized on treated Ti foil with HCl by CVD, and TiO$_{2}$ nanotubes are prepared by the three-step anodization method. Scanning electron microscopy shows the final TiO$_{2}$ structures prepared using three processes with three different morphologies of nanosheet, nanorod and nanotube. X-ray diffraction verifies the presence of TiO$_{2}$. TiO$_{2}$ sheets and rods are crystalized in rutile phase, and TiO$_{2}$ tubes after annealing turn into the anatase crystal phase. The optical investigations carried out by diffuse reflection spectroscopy reveal that the morphology of TiO$_{2}$ nanostructures influencing their optical response and band gap energy of TiO$_{2}$ is changed for different TiO$_{2}$ nanostructures.
Characterization of Microstructure and Stability of Precipitation in SIMP Steel Irradiated with Energetic Fe Ions
Xue-Song Fang, Tie-Long Shen, Ming-Huan Cui, Peng Jin, Bing-Sheng Li, Ya-Bin Zhu, Zhi-Guang Wang
Chin. Phys. Lett. 2017, 34 (11): 116102 .   DOI: 10.1088/0256-307X/34/11/116102
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A type of home-made reduced activation martensitic steel, high silicon (SIMP) steel, is homogeneously irradiated with energetic Fe ions to the doses of 0.1, 0.25 and 1 displacement per atom (dpa), respectively, at 300$^{\circ}\!$C and 1 dpa, at 400$^{\circ}\!$C. Microstructural changes are investigated in detail by transmission electron microscopy with cross-section technique. Interstitial defects and defect clusters induced by Fe-ion irradiation are observed in all the specimens under different conditions. It is found that with increasing irradiation temperature, size of defect clusters increases while the density drops quickly. The results of element chemical mapping from the STEM images indicate that the Si element enrichment and Ta element depletion occur inside the precipitates in the matrix of SIMP steel irradiated to a dose of 1 dpa at 300$^{\circ}\!$C. Correlations between the microstructure and irradiation conditions are briefly discussed.
Spin Dynamics in Ferromagnet/10-nm-Thick N-Type GaAs Quantum Well Junctions
Xiao-Chen Ji, Chao Shen, Yuan-Jun Wu, Jun Lu, Hou-Zhi Zheng
Chin. Phys. Lett. 2017, 34 (11): 116701 .   DOI: 10.1088/0256-307X/34/11/116701
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Spin dynamics in several different types of ferromagnetic metal (FM)/10-nm-thick n-type GaAs quantum well (QW) junctions is studied by means of time-resolved Kerr rotation measurements. Compared with the MnGa/in-situ doped 10-nm-thick n-type GaAs QW junction, the spin lifetime of the MnGa/modulation-doped 10-nm-thick n-type GaAs QW junction is shorter by a factor of 5, consistent with the D'yakonov–Perel' spin relaxation mechanism. Meanwhile, compared with the spin lifetime of the MnAs/in-situ doped 10-nm-thick n-type GaAs QW junction, the MnGa/in-situ doped 10-nm-thick n-type GaAs QW junction is of a spin lifetime longer by a factor of 4.2. The later observation is well explained by the Rashba effect in the presence of structure inversion asymmetry, which acts directly on photo-excited electron spins. We demonstrate that MnGa-like FM/in-situ doped 10-nm-thick n-type GaAs QW junctions, which possess relatively low interfacial potential barriers, are able to provide long spin lifetimes.
Adsorption of 1,3,5-Triphenylbenzene Molecules and Growth of Graphene Nanoflakes on Cu(100) Surface
Qiao-Yun Liu, Jun-Jie Song, Yi-Liang Cai, Dan Qiao, Li-Wei Jing, Pi-Mo He, Han-Jie Zhang
Chin. Phys. Lett. 2017, 34 (11): 116801 .   DOI: 10.1088/0256-307X/34/11/116801
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Adsorption of 1,3,5-triphenylbenzene (TPB) molecules on Cu(100) surface is studied using ultraviolet photoelectron spectroscopy (UPS) and density functional theory (DFT) calculations. Researches on the bottom-up fabrication of graphene nanoflakes (GNFs) with TPB as a precursor on the Cu(100) surface are carried out based on UPS and DFT calculations. Three emission features $d$, $e$ and $f$ originating from the TPB molecules are located at 3.095, 7.326 and 9.349 eV below the Fermi level, respectively. With the increase of TPB coverage on the Cu(100) substrate, the work function decreases due to the formation of interfacial dipoles and charge (electron) rearrangement at the TPB/Cu(100) interface. Upon the formation of GNFs, five emission characteristic peaks of $g$, $h$, $i$, $j$ and $k$ originating from the GNFs are located at 1.100, 3.529, 6.984, 8.465 and 9.606 eV below the Fermi level, respectively. Angle resolved ultraviolet photoelectron spectroscopy (ARUPS) and DFT calculations indicate that TPB molecules adopt a lying-down configuration with their molecular plane nearly parallel to the Cu(100) substrate at the monolayer stage. At the same time, the lying-down configuration for the GNFs on the Cu(100) surface is also unveiled by ARUPS and DFT calculations.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
Electronic Transport Properties of Diblock Co-Oligomer Molecule Devices Sandwiched between Nitrogen Doping Armchair Graphene Nanoribbon Electrodes
Meng Ye, Cai-Juan Xia, Ai-Yun Yang, Bo-Qun Zhang, Yao-Heng Su, Zhe-Yan Tu, Yue Ma
Chin. Phys. Lett. 2017, 34 (11): 117101 .   DOI: 10.1088/0256-307X/34/11/117101
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We investigate the electronic transport properties of dipyrimidinyl-diphenyl sandwiched between two armchair graphene nanoribbon electrodes using the nonequilibrium Green function formalism combined with a first-principles method based on density functional theory. Among the three models M1–M3, M1 is not doped with a heteroatom. In the left parts of M2 and M3, nitrogen atoms are doped at two edges of the nanoribbon. In the right parts, nitrogen atoms are doped at one center and at the edges of M2 and M3, respectively. Comparisons of M1, M2 and M3 show obvious rectifying characteristics, and the maximum rectification ratios are up to 42.9 in M2. The results show that the rectifying behavior is strongly dependent on the doping position of electrodes. A higher rectification ratio can be found in the dipyrimidinyl-diphenyl molecular device with asymmetric doping of left and right electrodes, which suggests that this system has a broader application in future logic and memory devices.
New Method for 3D Transient Eddy Current Field Calculation and Its Application in Magneto-Acoustic Tomography
Yuan-Yuan Li, Guo-Qiang Liu, Hui-Xia, Li-Li Hu
Chin. Phys. Lett. 2017, 34 (11): 117201 .   DOI: 10.1088/0256-307X/34/11/117201
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A new method of 3D transient eddy current field calculation is proposed. The Maxwell equations with time component elimination (METCE) are derived under the assumption of magnetic quasi static approximation, especially for the sample of low conductivity. Based on METCE, we deduce a more efficient reconstruction algorithm of a 3D transient eddy current field. The computational burden is greatly reduced through the new algorithm, and the computational efficiency is improved. This new algorithm decompounds the space-time variables into two individual variables. The idea is to solve the spatial vector component firstly, and then multiply it by the corresponded time component. The iterative methods based on METCE are introduced to recover the distribution of conductivity in magneto-acoustic tomography. The reconstructed images of conductivity are consistent with the original distribution, which validate the new method.
Predicted High Thermoelectric Performance of Quasi-Two-Dimensional Compound GeAs Using First-Principles Calculations
Dai-Feng Zou, Chuan-Bin Yu, Yu-Hao Li, Yun Ou
Chin. Phys. Lett. 2017, 34 (11): 117202 .   DOI: 10.1088/0256-307X/34/11/117202
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The electronic structure of binary quasi-two-dimensional GeAs is investigated using first-principles calculations, and it is found that the anisotropic structure of the layered compound GeAs brings about the anisotropy of the transport properties. Meanwhile, the band structure of GeAs exhibits a relatively large dispersion near the valence-band maximum in the $Z$–$V$ direction while it is rather flat in the $Z$–${\it \Gamma}$ direction, which is highly desirable for good thermoelectric performance. The calculated partial charge density distribution also reveals that GeAs possesses anisotropic electrical conductivity. Based on the semi-classical Boltzmann transport theory, the anisotropic transport properties are observed, and the optimal doping concentrations are estimated. The temperature dependence transport properties of p-type GeAs are compared with the experimental data in good agreement, and the theoretical figure-of-merit $ZT$ has been predicted as well.
Circular Photogalvanic Effect in the Weyl Semimetal TaAs
Kai Sun, Shuai-Shuai Sun, Lin-Lin Wei, Cong Guo, Huan-Fang Tian, Gen-Fu Chen, Huai-Xin Yang, Jian-Qi Li
Chin. Phys. Lett. 2017, 34 (11): 117203 .   DOI: 10.1088/0256-307X/34/11/117203
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Weyl semimetal (WSM) is expected to be an ideal spintronic material owing to its spin currents carried by the bulk and surface states with spin-momentum locking. The generation of a sizable photocurrent is predicted in non-centrosymmetric WSM arising from the broken inversion symmetry and the linear energy dispersion that is unique to Weyl systems. In our recent measurements, the circular photogalvanic effect (CPGE) is discovered in the TaAs WSM. The CPGE voltage is proportional to the helicity of the incident light, reversing direction if the radiation helicity changes handedness, a periodical oscillation therefore appears following the alteration of light polarization. We herein attribute the CPGE to the asymmetric optical excitation of the Weyl cone, which could result in an asymmetric distribution of photoexcited carriers in momentum space according to an optical spin-related selection rule.
Design of Broadband Metamaterial Absorbers for Permittivity Sensitivity and Solar Cell Application
Hai-Long Huang, Hui Xia, Zhi-Bo Guo, Ding Xie, Hong-Jian Li
Chin. Phys. Lett. 2017, 34 (11): 117801 .   DOI: 10.1088/0256-307X/34/11/117801
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A broadband and ultra-thin absorber for solar cell application is designed. The absorber consists of three layers, and the difference is that the four split ring resonators made of metal gold are encrusted in the gallium arsenide (GaAs) plane in the top layer. The simulated results show that a perfect absorption in the region from 481.2 to 684.0 THz can be obtained for either transverse electric or magnetic polarization wave due to the coupling effect between the material of GaAs and gold. The metamaterial is ultra-thin, having the total thickness of 56 nm, which is less than one-tenth resonance wavelength, and the absorption coefficients at the three resonance wavelengths are above 90%. Moreover, the effective medium theory, electric field and surface current distributions are adopted to explain the physical mechanism of the absorption, and the permittivity sensing applications are also discussed. As a result, the proposed structure can be used in many areas, such as solar cell, sensors, and integrated photodetectors.
CROSS-DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY
Fabrication of High-Haze Flexible Transparent Conductive PMMA Films Embedded with Silver Nanowires
Lu Zhong, Wei Xu, Mei-Yi Yao, Wen-Feng Shen, Feng Xu, Wei-Jie Song
Chin. Phys. Lett. 2017, 34 (11): 118101 .   DOI: 10.1088/0256-307X/34/11/118101
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High-haze flexible transparent conductive polymethyl methacrylate (PMMA) films embedded with silver nanowires (AgNWs) are fabricated by a low-cost and simple process. The volatilization rate of the solvent in PMMA solution affects the surface microstructures and morphologies, which results in different haze factors of the composite films. The areal mass density of AgNW shows a significant influence on the optical and electrical properties of composite films. The AgNW/PMMA transparent conductive films with the sheet resistance of 5.5 $\Omega$sq$^{-1}$ exhibit an excellent performance with a high haze factor of 81.0% at 550 nm.
Fabrication and Characterization of a GaN-Based 320$\times$256 Micro-LED Array
Xiao-Fan Mo, Wei-Zong Xu, Hai Lu, Dong Zhou, Fang-Fang Ren, Dun-Jun Chen, Rong Zhang, You-Dou Zheng
Chin. Phys. Lett. 2017, 34 (11): 118102 .   DOI: 10.1088/0256-307X/34/11/118102
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Design, fabrication and characterizations of GaN-based blue micro light emitting diode (LED) arrays are reported. The GaN micro-LED array consists of $320\times256$ pixels with a pitch size of 30 μm. Each pixel is $25\times25$ μm$^{2}$ in size, which is designed for backside emission and high density flip-chip packaging. The selected LED pixels being tested exhibit good uniformity in terms of turn-on voltage and reverse leakage current. The efficiency droop behavior and reliability behavior under high forward current stress are also studied. The micro-LED pixel shows improved reliability, which is likely caused by enhanced heat dissipation.
Controllable Fabrication of GeSi Nanowires in Diameter of About 10nm Using the Top-Down Approach
Cheng Zeng, Yi Li, Jin-Song Xia
Chin. Phys. Lett. 2017, 34 (11): 118103 .   DOI: 10.1088/0256-307X/34/11/118103
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Ordered GeSi nanowires with a $\sim$10 nm cross section are fabricated utilizing top-down and Ge condensation techniques. In transmission electron microscopy measurements, the obtained GeSi nanowires exhibit a single-crystal structure and a smooth Ge/SiO$_{2}$ interface. Due to the linear relationship between the cross-section area and the initial pattern size under the self-limited oxidation condition, the cross-section size of GeSi nanowires can be precisely controlled. The Raman spectra reveal a high Ge fraction (up to 97%) and a biaxial strain of the GeSi nanowires. This top-down technique is promising for fabrication of high-performance GeSi nanowire based optoelectronic devices.
Influence of Total Ionizing Dose Irradiation on Low-Frequency Noise Responses in Partially Depleted SOI nMOSFETs
Chao Peng, Yun-Fei En, Zhi-Feng Lei, Yi-Qiang Chen, Yuan Liu, Bin Li
Chin. Phys. Lett. 2017, 34 (11): 118501 .   DOI: 10.1088/0256-307X/34/11/118501
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Total ionizing dose effect induced low frequency degradations in 130 nm partially depleted silicon-on-insulator (SOI) technology are studied by $^{60}$Co $\gamma$-ray irradiation. The experimental results show that the flicker noise at the front gate is not affected by the radiation since the radiation induced trapped charge in the thin gate oxide can be ignored. However, both the Lorenz spectrum noise, which is related to the linear kink effect (LKE) at the front gate, and the flicker noise at the back gate are sensitive to radiation. The radiation induced trapped charge in shallow trench isolation and the buried oxide can deplete the nearby body region and can activate the traps which reside in the depletion region. These traps act as a GR center and accelerate the consumption of the accumulated holes in the floating body. It results in the attenuation of the LKE and the increase of the Lorenz spectrum noise. Simultaneously, the radiation induced trapped charge in the buried oxide can directly lead to an enhanced flicker noise at the back gate. The trapped charge density in the buried oxide is extracted to increase from $2.21\times10^{18}$ eV$^{-1}$cm$^{-3}$ to $3.59\times10^{18}$ eV$^{-1}$cm$^{-3}$ after irradiation.
Experimental and Simulation Analysis of Two-Tone and Three-Tone Photodetector Linearity Characterizing Systems
Jia-Rui Fei, Yong-Qing Huang, You-Xin Liu, Kai Liu, Xiao-Feng Duan, Xiao-Min Ren
Chin. Phys. Lett. 2017, 34 (11): 118502 .   DOI: 10.1088/0256-307X/34/11/118502
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Two measurement techniques are investigated to characterize photodetector linearity. A model for the two-tone and three-tone photodetector systems is developed to thoroughly investigate the influences of setup components on the measurement results. We demonstrate that small bias shifts from the quadrature point of the modulator will induce deviation into measurement results of the two-tone system, and the simulation results correspond well to experimental and calculation results.
Fano Factor in Strained Graphene Nanoribbon Nanodevices
Walid Soliman, Mina D. Asham, Adel H. Phillips
Chin. Phys. Lett. 2017, 34 (11): 118503 .   DOI: 10.1088/0256-307X/34/11/118503
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We investigate the Fano factor in a strained armchair and zigzag graphene nanoribbon nanodevice under the effect of ac field in a wide range of frequencies at different temperatures (10 K–70 K). This nanodevice is modeled as follows: a graphene nanoribbon is connected to two metallic leads. These two metallic leads operate as a source and a drain. The conducting substance is the gate electrode in this three-terminal nanodevice. Another metallic gate is used to govern the electrostatics and the switching of the graphene nanoribbon channel. The substances at the graphene nanoribbon/metal contact are controlled by the back gate. The photon-assisted tunneling probability is deduced by solving the Dirac eigenvalue differential equation in which the Fano factor is expressed in terms of this tunneling probability. The results show that for the investigated nanodevice, the Fano factor decreases as the frequency of the induced ac field increases, while it increases as the temperature increases. In general, the Fano factors for both strained armchair and zigzag graphene nanoribbons are different. This is due to the effect of the uniaxial strain. It is shown that the band structure parameters of graphene nanoribbons at the energy gap, the C–C bond length, the hopping integral, the Fermi energy and the width are modulated by uniaxial strain. This research gives us a promise of the present nanodevice being used for digital nanoelectronics and sensors.
Influence of Tilted Angle on Effective Linear Energy Transfer in Single Event Effect Tests for Integrated Circuits at 130nm Technology Node
Le-Qing Zhang, Jian Lu, Jia-Ling Xu, Xiao-Nian Liu, Li-Hua Dai, Yi-Ran Xu, Da-Wei Bi, Zheng-Xuan Zhang,
Chin. Phys. Lett. 2017, 34 (11): 118504 .   DOI: 10.1088/0256-307X/34/11/118504
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A heavy-ion irradiation experiment is studied in digital storage cells with different design approaches in 130 nm CMOS bulk Si and silicon-on-insulator (SOI) technologies. The effectiveness of linear energy transfer (LET) with a tilted ion beam at the 130 nm technology node is obtained. Tests of tilted angles $\theta =0^{\circ}$, 30$^{\circ}$ and 60$^{\circ}$ with respect to the normal direction are performed under heavy-ion Kr with certain power whose LET is about 40 MeVcm$^{2}$/mg at normal incidence. Error numbers in D flip-flop chains are used to determine their upset sensitivity at different incidence angles. It is indicated that the effective LETs for SOI and bulk Si are not exactly in inverse proportion to $\cos \theta$, furthermore the effective LET for SOI is more closely in inverse proportion to $\cos \theta$ compared to bulk Si, which are also the well known behavior. It is interesting that, if we design the sample in the dual interlocked storage cell approach, the effective LET in bulk Si will look like inversely proportional to $\cos \theta$ very well, which is also specifically explained.
Mechanism of Competition between Nutlin3 and p53 for Binding with Mdm2
Shu-Xia Liu, Shi-Wei Yan
Chin. Phys. Lett. 2017, 34 (11): 118701 .   DOI: 10.1088/0256-307X/34/11/118701
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The tumour suppressor p53 is a transcription factor that regulates multiple biological functions including metabolism, DNA repair, cell cycle arrest, apoptosis and senescence. About half of human cancers show a normal TP53 gene and aberrant overexpression of Mdm2. This fact promotes a promising cancer therapeutic strategy by inhibiting the interactions between p53 and Mdm2. Various inhibitors have been designed to achieve this novel approach for cancer therapy. However, the detailed competition mechanism between these inhibitors and the p53 molecule in their binding process to Mdm2 is still unclear. We investigate this competition mechanism between Nutlin3 and p53 using molecular dynamics simulations. It is found that Nutlin3 binds faster than the p53 molecule to Mdm2 to prevent p53 binding to Mdm2 when Nutlin3 and p53 have equal distance from Mdm2. Nutlin3 can also bind to the p53-Mdm2 complex to disturb and weaken the interactions between p53 and Mdm2. Consequently, p53 cannot bind to Mdm2 and its tumour suppression function is reactivated. These results provide the detailed competition mechanism between Nutlin3 and p53 in their binding to Mdm2. Because the binding site of most other inhibitors to Mdm2 is the same as Nutlin3, therefore this competition mechanism can extend to most inhibitors which target the p53-Mdm2 interaction.
Effect of Optical Microcavity on Absorption Behavior of Homo-Tandem Organic Solar Cells
Guo-Long Li, Hao Wang, Jing-Rong Meng, Jin Li, Li-Jun He, Ming-Kui Wang
Chin. Phys. Lett. 2017, 34 (11): 118801 .   DOI: 10.1088/0256-307X/34/11/118801
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The optical microcavity effect of the homo-tandem solar cells is explored utilizing the transfer matrix method. Ultrathin silver can reduce the deadzone effect compared with graphene and PH1000, and leads to a factor of 1.07 enhancement for an electrical field in a metal microcavity. The enhancement is considered to be the fact that strong exciton-photon coupling occurs in the microcavity due to ultrathin Ag. On the basis of the optical enhancement effect, optical behaviors are manipulated by varying the microcavity length. It is confirmed that ultrathin silver can serve as an ideal interconnection layer as the active layer is $\sim$150 nm thick and the thickness ratio between front and rear active layers lies between 1:1 and 1:2.
30 articles