Volume 35 Issue 4

Previous Issue    Next Issue

Current Issue

Realization of Quantum Maxwell's Demon with Solid-State Spins
W.-B. Wang, X.-Y. Chang, F. Wang, P.-Y. Hou, Y.-Y. Huang, W.-G. Zhang, X.-L. Ouyang, X.-Z. Huang, Z.-Y. Zhang, H.-Y. Wang, L. He, L.-M. Duan
Chin. Phys. Lett. 2018, 35 (4): 040301 .   DOI: 10.1088/0256-307X/35/4/040301
Abstract   PDF(pc) (1703KB) ( 799 ) PDF(mobile)(1693KB) ( 39 ) HTML ( 1037
We report experimental realization of a quantum version of Maxwell's demon using solid state spins where the information acquiring and feedback operations by the demon are achieved through conditional quantum gates. A unique feature of this implementation is that the demon can start in a quantum superposition state or in an entangled state with an ancilla observer. Through quantum state tomography, we measure the entropy in the system, demon, and the ancilla, showing the influence of coherence and entanglement on the result. A quantum implementation of Maxwell's demon adds more controllability to this paradoxical thermal machine and may find applications in quantum thermodynamics involving microscopic systems.
Phase Transition and Quasinormal Modes for Spherical Black Holes in 5D Gauss–Bonnet Gravity
Ming Zhang, Rui-Hong Yue
Chin. Phys. Lett. 2018, 35 (4): 040401 .   DOI: 10.1088/0256-307X/35/4/040401
Abstract   PDF(pc) (573KB) ( 380 ) PDF(mobile)(557KB) ( 13 ) HTML ( 461
We study the quasinormal modes (QNMs) of massless scalar perturbations to probe the van der Waals like SBH/LBH phase transition of anti-de Sitter black holes in five-dimensional (5D) Gauss–Bonnet gravity. It is found that the signature of this SBH/LBH phase transition is detected when the slopes of the QNMs frequency change drastically and differently in small and large black holes near the critical point. The obtained results further support that the QNMs can be a dynamic probe to investigate the thermodynamic properties in black holes.
Neutron Diffraction of Large-Volume Samples at High Pressure Using Compact Opposed-Anvil Cells
Xiao-Lin Ni, Lei-Ming Fang, Xin Li, Xi-Ping Chen, Lei Xie, Duan-Wei He, Zi-Li Kou
Chin. Phys. Lett. 2018, 35 (4): 040701 .   DOI: 10.1088/0256-307X/35/4/040701
Abstract   PDF(pc) (682KB) ( 478 ) PDF(mobile)(679KB) ( 7 ) HTML ( 377
Neutron diffraction techniques of large-volume samples at high pressure using compact opposed-anvil cells are developed at a reactor neutron source, China's Mianyang research reactor. We achieve a high-pressure condition of in situ neutron diffraction by means of a newly designed large-volume opposed-anvil cell. This pressure calibration is based on resistance measurements of bismuth and the neutron diffraction of iron. Pressure calibration experiments are performed at room temperature for a new cell using the tungsten carbide anvils with a tapered angle of 30$^{\circ}$, ${\it \Phi}$4.5 mm culet diameter and the metal-nonmetal composite gasket with a thickness of 2 mm. Transitions in Bi (I–II 2.55 GPa, III–V 7.7 GPa) are observed at 100 and 300 kN, respectively, by resistance measurements. The pressure measurement results of neutron diffraction are consistent with resistance measurements of bismuth. As a result, pressures up to about 7.7 GPa can routinely and stably be achieved using this apparatus, with the sample volume of 9 mm$^{3}$.
Hopping Parameter Expansion Technique in Noise Method for Disconnected Quark Loops
Jia-Liang Zhou, Zhen Cheng, Guang-Yi Xiong, Jian-Bo Zhang
Chin. Phys. Lett. 2018, 35 (4): 041101 .   DOI: 10.1088/0256-307X/35/4/041101
Abstract   PDF(pc) (538KB) ( 356 ) PDF(mobile)(541KB) ( 10 ) HTML ( 255
We investigate the effectiveness of the hopping parameter expansion (HPE) combined with the $Z(2)$ noise method in the calculation of the trace of the inverse of Wilson's Dirac operator and some other disconnected contributions. A numerical comparison of the standard deviation for the $Z(2)$ noise method and HPE with the $Z(2)$ noise method is carried out. It is found that there are noise reductions in all the quantities we calculated using the HPE with the $Z(2)$ noise method. For the trace of the inverse of Wilson's Dirac operator, the HPE can reduce the statistical error by about 60%.
Multi-Electron Effects in Attosecond Transient Absorption of CO Molecules
Bin Zhang, Jian Zhao, Zeng-Xiu Zhao
Chin. Phys. Lett. 2018, 35 (4): 043201 .   DOI: 10.1088/0256-307X/35/4/043201
Abstract   PDF(pc) (600KB) ( 624 ) PDF(mobile)(584KB) ( 5 ) HTML ( 360
Using the fully propagated time-dependent Hartree–Fock method, we identify that both the dynamic core polarization and multiorbital contributions are important in the attosecond transient absorption of CO molecules. The dynamics of core electrons effectively modifies the behaviors of electrons in the highest occupied molecular orbital, resulting in the modulation of intensity and position of the absorption peaks. Depending on the alignment angles, different inner orbitals are identified to contribute, and even dominate the total absorption spectra. As a result, multi-electron fingerprints are encoded in the absorption spectra, which shed light on future applications of attosecond transient absorption in complex systems.
Kramers–Henneberger Form of Strong Field Theory with the Correction of Dipole Approximation
Yi-Ning Huo, Jian Li, Feng-Cai Ma
Chin. Phys. Lett. 2018, 35 (4): 043202 .   DOI: 10.1088/0256-307X/35/4/043202
Abstract   PDF(pc) (649KB) ( 531 ) PDF(mobile)(647KB) ( 3 ) HTML ( 367
We show that the breakdown of dipole approximation can be adopted to explain the asymmetry structure in the photoelectron momentum distributions along the beam propagation direction, which is defined as the photoelectron longitudinal momentum distributions (PLMD), in tunneling regime ($\gamma_{\rm K}\ll 1$), based on the strong field approximation theory. The nondipole Hamiltonian for photoelectrons interacting with laser fields from a hydrogen-like atom is transformed into the Kramers–Henneberger frame in our model. To introduce the correction of dipole approximation, the spatial variable is kept in a vector potential ${\boldsymbol A}({\boldsymbol r},t)$, demonstrating that the breakdown of dipole approximation is the major reason for the shift of the peak in PLMD. The nondipole effects are apparent when circularly polarized lasers are adopted to ionize the atoms, and clear tendency to increase offsets is found for increasing laser intensities.
Experimental Determination of the Landé $g$-Factors for 5$s^{2}$$^{1}\!S$ and $5s5p$$^{3}\!P$ States of the $^{87}$Sr Atom
Ben-quan Lu, Yebing Wang, Yang Guo, Qinfang Xu, Mojuan Yin, Jiguang Li, Hong Chang
Chin. Phys. Lett. 2018, 35 (4): 043203 .   DOI: 10.1088/0256-307X/35/4/043203
Abstract   PDF(pc) (733KB) ( 343 ) PDF(mobile)(723KB) ( 19 ) HTML ( 233
We present an experimental determination on the Landé $g$-factors for the 5$s^{2}$ $^{1}\!S_{0}$ and $5s5p$ $^{3}\!P_{0}$ states in ultra-cold atomic systems, which is important for evaluating the Zeeman shift of the clock transition in the $^{87}$Sr optical lattice clock. The Zeeman shift of the $5s5p$ $^{3}\!P_{0}$–5$s^{2}$ $^{1}\!S_{0}$ forbidden transition is measured with the $\pi$-polarized and $\sigma^{\pm}$-polarized interrogations at different magnetic field strengths. Moreover, in the $g$-factor measurement with the $\sigma^{\pm}$-transition spectra, it is unnecessary to calibrate the external magnetic field. By this means, the ground state 5$s^{2}$ $^{1}\!S_{0}$ $g$-factor for the $^{87}$Sr atom is $-1.306(52)\times10^{-4}$, which is the first experimental determination to the best of our knowledge, and the result matches very well with the theoretical estimation. The differential $g$-factor $\delta g$ between the $5s5p$ $^{3}\!P_{0}$ state and the 5$s^{2}$ $^{1}\!S_{0}$ state of the $^{87}$Sr atoms is measured in the experiment as well, which are $-7.67(36)\times10^{-5}$ with $\pi$-transition spectra and $-7.72(43)\times10^{-5}$ with $\sigma^{\pm}$-transition spectra, in good agreement with the previous report [Phys. Rev. A 76 (2007) 022510]. This work can also be used for determining the differential $g$-factor of the clock states for the optical clocks based on other atoms.
Raman-Assisted Passively Mode-Locked Fiber Laser
Lei Zhao, Pei-Jun Yao, Chun Gu, Li-Xin Xu
Chin. Phys. Lett. 2018, 35 (4): 044201 .   DOI: 10.1088/0256-307X/35/4/044201
Abstract   PDF(pc) (1027KB) ( 474 ) PDF(mobile)(1022KB) ( 4 ) HTML ( 254
We propose and demonstrate a Raman-assisted passively mode-locked Yb-doped fiber laser in a normal dispersion regime. A section of highly nonlinear fiber is adopted to enhance the nonlinearity to extend the bandwidth of the gain spectrum by the stimulated Raman effect. The mode-locked fiber laser emits a broad spectral bandwidth of 64 nm at the $-$20 dB level and a highly stable pulse operation with a signal-to-noise ratio of 77 dB.
Electrically and Optically Bistable Operation in an Integration of a 1310nm DFB Laser and a Tunneling Diode
Ya-Jie Li, Jia-Qi Wang, Lu Guo, Guang-Can Chen, Zhao-Song Li, Hong-Yan Yu, Xu-Liang Zhou, Huo-Lei Wang, Wei-Xi Chen, Jiao-Qing Pan
Chin. Phys. Lett. 2018, 35 (4): 044202 .   DOI: 10.1088/0256-307X/35/4/044202
Abstract   PDF(pc) (609KB) ( 424 ) PDF(mobile)(606KB) ( 5 ) HTML ( 205
We experimentally demonstrate an InP-based hybrid integration of a single-mode DFB laser emitting at around 1310 nm and a tunneling diode. The evident negative differential resistance regions are obtained in both electrical and optical output characteristics. The electrical and optical bistabilities controlled by the voltage through the tunneling diode are also measured. When the voltage changes between 1.46 V and 1.66 V, a 200-mV-wide hysteresis loop and an optical power ON/OFF ratio of 17 dB are obtained. A side-mode suppression ratio of the integrated device in the ON state is up to 43 dB. The tunneling diode can switch on/off the laser within a very small voltage range compared with that directly controlled by a voltage source.
Tip-Nanoparticle Near-Field Coupling in Scanning Near-Field Microscopy by Coupled Dipole Method
Yi Ruan, Kan Li, Qiang Lin, Ting Zhang
Chin. Phys. Lett. 2018, 35 (4): 044203 .   DOI: 10.1088/0256-307X/35/4/044203
Abstract   PDF(pc) (2322KB) ( 296 ) PDF(mobile)(2319KB) ( 1 ) HTML ( 133
We use the couple dipole method to investigate the scanning near-field optical microscopy metallic tip-nanoparticle near-field interaction. Dependences of the local field intensity inside the nanoparticle on the nanosized tip shape, the tip open angle and the illumination angle are revealed. In combination with the previous results, we establish a complete model to understand the tip-nanoparticle near-field coupling mechanism.
Mode-Locked Erbium-Doped Fiber Laser Using Vanadium Oxide as Saturable Absorber
A. Nady, M. F. Baharom, A. A. Latiff, S. W. Harun
Chin. Phys. Lett. 2018, 35 (4): 044204 .   DOI: 10.1088/0256-307X/35/4/044204
Abstract   PDF(pc) (823KB) ( 819 ) PDF(mobile)(816KB) ( 9 ) HTML ( 413
A mode-locked erbium doped fiber laser (EDFL) is demonstrated using the vanadium oxide (V$_{2}$O$_{5}$) material as a saturable absorber (SA). The V$_{2}$O$_{5}$ based SA is hosted into poly ethylene oxide film and attached on fiber ferule in the laser cavity. It shows 7% modulation depth with 71 MW/cm$^{2}$ saturation intensity. By incorporating the SA inside the EDFL cavity with managed intra-cavity dispersion, ultrashort soliton pulses are successfully generated with a full width at half maximum of 3.14 ps. The laser operated at central wavelength of 1559.25 nm and repetition frequency of 1 MHz.
Superradiance-Driven Phonon Laser
Ya-Jing Jiang, Hao Lü, Hui Jing
Chin. Phys. Lett. 2018, 35 (4): 044205 .   DOI: 10.1088/0256-307X/35/4/044205
Abstract   PDF(pc) (529KB) ( 378 ) PDF(mobile)(519KB) ( 18 ) HTML ( 205
We propose to enhance the generation of a phonon laser by exploiting optical superradiance. In our scheme, the optomechanical cavity contains a movable membrane, which supports a mechanical mode, and the superradiance cavity can generate the coherent collective light emissions by applying a transverse pump to an ultracold intracavity atomic gas. The superradiant emission turns out to be capable of enhancing the phonon laser performance. This indicates a new way to operate a phonon laser with the assistance of coherent atomic gases trapped in a cavity or lattice potentials.
A Temperature-Insensitive Amplified Spontaneous Emission Broadband Source Based on Er-Doped Fiber
Yue-e Chen, Yun-kai Zhou, De-wang Yang, Wei Yan, Yong Wang
Chin. Phys. Lett. 2018, 35 (4): 044206 .   DOI: 10.1088/0256-307X/35/4/044206
Abstract   PDF(pc) (725KB) ( 447 ) PDF(mobile)(724KB) ( 2 ) HTML ( 112
To obtain a stable amplified spontaneous emission (ASE) source for complex environment applications, we design an ASE source and study the output power and spectral characteristics under different ambient temperatures. We optimize the structure of the ASE source to flatten the ASE spectrum, and study the output characteristics in terms of output power and optical spectrum under different pump powers. Then the performance of the ASE source is investigated in the temperature range from $-$18.9$^{\circ\!}$C to 50$^{\circ\!}$C. A stable-power and flat-spectrum ASE source can be obtained by structural optimization and pump control.
Sequential Parameter Estimation Using Modal Dispersion Curves in Shallow Water
Xue-Dong Zhang, Li-Xin Wu, Hai-Qiang Niu, Ren-He Zhang
Chin. Phys. Lett. 2018, 35 (4): 044301 .   DOI: 10.1088/0256-307X/35/4/044301
Abstract   PDF(pc) (2099KB) ( 444 ) PDF(mobile)(2101KB) ( 6 ) HTML ( 147
Existing sequential parameter estimation methods use the acoustic pressure of a line array as observations. The modal dispersion curves are employed to estimate the sound speed profile (SSP) and geoacoustic parameters based on the ensemble Kalman filter. The warping transform is implemented to the signals received by a single hydrophone to obtain the dispersion curves. The experimental data are collected at a range-independent shallow water site in the South China Sea. The results indicate that the SSPs are well estimated and the geoacoustic parameters are also well determined. Comparisons of the observed and estimated modal dispersion curves show good agreement.
Extraordinary Electromagnetic Waves in Weakly Relativistic Degenerate Spin-1/2 Magnetized Quantum Plasmas
Chun-Hua Li, Shao-Wei Wang, Yun-Hao Liu, Zhen-Wei Xia, Xiao-Hui Zhang, Dan-Dan Zou
Chin. Phys. Lett. 2018, 35 (4): 045201 .   DOI: 10.1088/0256-307X/35/4/045201
Abstract   PDF(pc) (564KB) ( 475 ) PDF(mobile)(560KB) ( 3 ) HTML ( 177
By using the relativistic quantum magnetohydrodynamic model, the extraordinary electromagnetic waves in magnetized quantum plasmas are investigated with the effects of particle dispersion associated with the quantum Bohm potential effects, the electron spin-1/2 effects, and the relativistic degenerate pressure effects. The electrons are treated as a quantum and magnetized species, while the ions are classical ones. The new general dispersion relations are derived and analyzed in some interesting special cases. Quantum effects are shown to affect the dispersion relations of the extraordinary electromagnetic waves. It is also shown that the relativistic degenerate pressure effects significantly modify the dispersive properties of the extraordinary electromagnetic waves. The present investigation should be useful for understanding the collective interactions in dense astrophysical bodies, such as the atmosphere of neutron stars and the interior of massive white dwarfs.
Effect of Parallel-Plate Geometry on Mode Transition Behavior in Argon Microplasmas: Two-Dimensional Simulation
Xiang-Mei Liu, Yuan-Hong Song, Wei Jiang, Wen-Zhu Jia
Chin. Phys. Lett. 2018, 35 (4): 045202 .   DOI: 10.1088/0256-307X/35/4/045202
Abstract   PDF(pc) (599KB) ( 572 ) PDF(mobile)(598KB) ( 5 ) HTML ( 152
A two-dimensional self-consistent fluid model is employed to investigate radio-frequency process parameters on the plasma properties in Ar microdischarges. The neutral gas density and temperature balance equations are taken into account. We mainly investigate the effect of the electrode gap on the spatial distribution of the electron density and electron temperature profiles, due to a mode transition from the $\gamma$ regime (secondary electrons emission is responsible for the significant ionization) to the $\alpha$ regime (sheath oscillations and bulk electrons are responsible for sustaining discharge) induced by a sudden decrease of electron density and electron temperature. The pressure, radio-frequency sources frequency and voltage effects on the electron density are also elaborately investigated.
Photoluminescence Analysis of Electron Damage for Minority Carrier Diffusion Length in GaInP/GaAs/Ge Triple-Junction Solar Cells
Rui Wu, Jun-Ling Wang, Gang Yan, Rong Wang
Chin. Phys. Lett. 2018, 35 (4): 046101 .   DOI: 10.1088/0256-307X/35/4/046101
Abstract   PDF(pc) (686KB) ( 530 ) PDF(mobile)(681KB) ( 3 ) HTML ( 163
Photoluminescence (PL) measurements are carried out to investigate the degradation of GaInP top cell and GaAs middle cell for GaInP/GaAs/Ge triple-junction solar cells irradiated with 1.0, 1.8 and 11.5 MeV electrons with fluences ranging up to $3\times10^{15}$, $1\times10^{15}$ and $3\times10^{14}$ cm$^{-2}$, respectively. The degradation rates of PL intensity increase with the electron fluence and energy. Furthermore, the damage coefficient of minority carrier diffusion length is estimated by the PL radiative efficiency. The damage coefficient increases with the electron energy. The relation of damage coefficient to electron energy is discussed with the non-ionizing energy loss (NIEL), which shows a quadratic dependence between damage coefficient and NIEL.
Bias Dependence of Radiation-Induced Narrow-Width Channel Effects in 65nm NMOSFETs
Qi-Wen Zheng, Jiang-Wei Cui, Ying Wei, Xue-Feng Yu, Wu Lu, Diyuan Ren, Qi Guo
Chin. Phys. Lett. 2018, 35 (4): 046102 .   DOI: 10.1088/0256-307X/35/4/046102
Abstract   PDF(pc) (646KB) ( 429 ) PDF(mobile)(644KB) ( 2 ) HTML ( 148
The bias dependence of radiation-induced narrow-width channel effects (RINCEs) in 65-nm n-type metal-oxide-semiconductor field-effect transistors (NMOSFETs) is investigated. The threshold voltage of the narrow-width 65 nm NMOSFET is negatively shifted by total ionizing dose irradiation, due to the RINCE. The experimental results show that the 65 nm narrow-channel NMOSFET has a larger threshold shift when the gate terminal is kept in the ground, which is contrary to the conclusion obtained in the old generation devices. Depending on the three-dimensional simulation, we conclude that electric field distribution alteration caused by shallow trench isolation scaling is responsible for the anomalous RINCE bias dependence in 65 nm technology.
Dipole Oscillation in a Bose–Fermi Superfluid Mixture of $^{41}$K and $^{6}$Li
Ren Zhang
Chin. Phys. Lett. 2018, 35 (4): 046701 .   DOI: 10.1088/0256-307X/35/4/046701
Abstract   PDF(pc) (557KB) ( 252 ) PDF(mobile)(553KB) ( 6 ) HTML ( 111
We study the relation between the bosonic frequency shift of a dipole oscillation and the fermionic compressibility in a Bose–Fermi superfluid mixture. Our results show that the ${\it \Lambda}$ transition occurs in such a system, which interprets the perplexing phenomenon observed in the recent experiment [arXiv:1705.04496]. In that experiment, the frequency shift of the bosonic gas was measured with different fermion-fermion s-wave scattering lengths $a_{\rm f}$. The most striking feature of their measurement is that the frequency shift shows a puzzling non-monotonic behavior around $1/k_{\rm F}a_{\rm f}\simeq-0.2$ with $k_{\rm F}$ being the Fermi momentum. In the present work, the relation between the bosonic frequency shift and the compressibility of the Fermi gas is revealed by means of the equation of state of the superfluid mixture. Making use of the relation, we find that the compressibility of Fermi gas shows a ${\it \Lambda}$-like shape around $1/k_{\rm F}a_{\rm f}\simeq-0.2$. We would like to stress that no free parameter is used in our calculation and our results can be further testified in a future experiment.
Directional Analysis of the Chaotic Superlattice around the Equilibrium Point in the Phase Space
Yan-Fei Liu, Dong-Dong Yang, Li-Xin Wang, Qi Li
Chin. Phys. Lett. 2018, 35 (4): 046801 .   DOI: 10.1088/0256-307X/35/4/046801
Abstract   PDF(pc) (939KB) ( 592 ) PDF(mobile)(936KB) ( 2 ) HTML ( 115
The recently proposed method of our research group named as directional Lyapunov exponents (DLEs) is presented. Then, DLEs are used to analyze the eigenstructure of the output phase space around the equilibrium points. Finally, the impacts of the superlattice parameter changes on the characteristics of the output chaotic signal are analyzed. The experimental results show that parameter changes of the superlattice will affect the eigenstructure around the equilibrium points in the output phase space, and DLEs are sensitive to these changes.
Molecular Dynamics Simulation of 4-N-Hexyl-4'-Cyanobiphenyl Adsorbed at the Air-Water Interface
Oğuz Gürbulak, Emine Cebe
Chin. Phys. Lett. 2018, 35 (4): 046802 .   DOI: 10.1088/0256-307X/35/4/046802
Abstract   PDF(pc) (660KB) ( 460 ) PDF(mobile)(650KB) ( 3 ) HTML ( 412
The interfacial behavior of 4-n-hexyl-4'-cyanobiphenyl (6CB) molecules at the air-water interface is investigated by full atomistic molecular dynamics simulations. To understand the morphology and the structure of adsorbed 6CB molecules in detail, the snapshots and mass density profiles of the simulation system are generated. The average tilt angles between the interface normal and various vectors defined in the rigid and alkyl parts of 6CB are in good agreement with the experimental data available. The interfacial thickness and monolayer width are obtained from the mass density profiles of water and 6CB phase, respectively. The second and fourth rank orientational order parameters of cyanobiphenyl core are found to be larger than those of an elastic alkyl chain. Bond order parameters for 6CB are also calculated. The calculated oxygen-oxygen radial distribution function and hydrogen bonding statistics for bulk water are compared with those for the interfacial region. The surface tensions of the systems are calculated. All simulation results are compared with the available literature data.
Effect of Interaction on the Majorana Zero Modes in the Kitaev Chain at Half Filling
Zhidan Li, Qiang Han
Chin. Phys. Lett. 2018, 35 (4): 047101 .   DOI: 10.1088/0256-307X/35/4/047101
Abstract   PDF(pc) (670KB) ( 596 ) PDF(mobile)(666KB) ( 6 ) HTML ( 107
The one-dimensional interacting Kitaev chain at half filling is studied. The symmetry of the Hamiltonian is examined by dual transformations, and various physical quantities as a function of the fermion-fermion interaction $U$ are calculated systematically using the density matrix renormalization group method. A special value of interaction $U_{\rm p}$ is revealed in the topological region of the phase diagram. We show that at $U_{\rm p}$ the ground states are strictly two-fold degenerate even though the chain length is finite and the zero-energy peak due to the Majorana zero modes is maximally enhanced and exactly localized at the end sites. Here $U_{\rm p}$ may be attractive or repulsive depending on other system parameters. We also give a qualitative understanding of the effect of interaction under the self-consistent mean field framework.
Energetics of He and H Atoms in W–Ta Alloys: First-Principle Calculations
Chu-Bin Wan, Su-Ye Yu, Xin Ju
Chin. Phys. Lett. 2018, 35 (4): 047102 .   DOI: 10.1088/0256-307X/35/4/047102
Abstract   PDF(pc) (892KB) ( 300 ) PDF(mobile)(886KB) ( 2 ) HTML ( 119
Properties of various defects of He and H atoms in W–Ta alloys are investigated based on density functional theory. The tetrahedral interstitial site is the most configured site for self-interstitial He and H in W and W–Ta alloys. Only a single He atom favors a substitutional site in the presence of a nearby vacancy. However, in the coexistence of He and H atoms in the presence of the vacancy, the single H atom favors the tetrahedral interstitial site (TIS) closest to the vacancy, and the He atom takes the vacancy center. The addition of Ta can reduce the formation energy of TIS He or H defects. The substituted Ta affects the charge density distribution in the vicinity of the He atom and decreases the valence electron density of the H atoms. A strong hybridization of the H $s$ states and the nearest W $d$ state s exists in W$_{53}$He$_{1}$H$_{1}$ structure. The sequence of the He $p$ projected DOS at the Fermi energy level is in agreement with the order of the formation energy of the He–H pair in the systems.
Nonvolatile Resistive Switching and Physical Mechanism in LaCrO$_{3}$ Thin Films
Wan-Jing Hu, Ling Hu, Ren-Huai Wei, Xian-Wu Tang, Wen-Hai Song, Jian-Ming Dai, Xue-Bin Zhu, Yu-Ping Sun
Chin. Phys. Lett. 2018, 35 (4): 047301 .   DOI: 10.1088/0256-307X/35/4/047301
Abstract   PDF(pc) (942KB) ( 669 ) PDF(mobile)(928KB) ( 3 ) HTML ( 164
Polycrystalline LaCrO$_{3}$ (LCO) thin films are deposited on Pt/Ti/SiO$_{2}$/Si substrates by pulsed laser deposition and used as the switching material to construct resistive random access memory devices. The unipolar resistive switching (RS) behavior in the Au/LCO/Pt devices exhibits a high resistance ratio of $\sim 10^{4}$ between the high resistance state (HRS) and low resistance state (LRS) and exhibits excellent endurance/retention characteristics. The conduction mechanism of the HRS in the high voltage range is dominated by the Schottky emission, while the Ohmic conduction dictates the LRS and the low voltage range of HRS. The RS behavior in the Au/LCO/Pt devices can be understood by the formation and rupture of conducting filaments consisting of oxygen vacancies, which is validated by the temperature dependence of resistance and x-ray photoelectron spectroscopy results. Further analysis shows that the reset current $I_{\rm R}$ and reset power $P_{\rm R}$ in the reset processes exhibit a scaling law with the resistance in LRS ($R_{0}$), which indicates that the Joule heating effect plays an essential role in the RS behavior of the Au/LCO/Pt devices.
Resistivity and Radio-Frequency Properties of Two-Generation Trap-Rich Silicon-on-Insulator Substrates
Lei Zhu, Yong-Wei Chang, Nan Gao, Xin Su, YeMin Dong, Lu Fei, Xing Wei, Xi Wang
Chin. Phys. Lett. 2018, 35 (4): 047302 .   DOI: 10.1088/0256-307X/35/4/047302
Abstract   PDF(pc) (1369KB) ( 1340 ) PDF(mobile)(1370KB) ( 4 ) HTML ( 296
Crystal morphologies and resistivity of polysilicon trap-rich layers of two-generation trap-rich silicon-on-insulator (TR-SOI) substrates are studied. It is found that the resistivity of the trap-rich layer of generation 2 (TR-G2) is higher than that of generation 1 (TR-G1), although the crystal morphologies of the trap rich layers are the same. In addition, the rf performance of two-generation TR-SOI substrates is investigated by coplanar waveguide lines and inductors. The results show that both the rf loss and the second harmonic distortion of TR-G2 are smaller than those of TR-G1. These results can be attributed to the higher resistivity values of both the trap-rich layer and the high-resistivity silicon (HR-Si) substrate of TR-G2. Moreover, the rf performance of the TR-SOI substrate with thicker buried oxide is slightly better. The second harmonics of various TR-SOI substrates are simulated and evaluated with the harmonic quality factor model as well. It can be predicted that the TR-SOI substrate will see further improvement in rf performance if the resistivities of both the trap-rich layer and HR-Si substrate increase.
Measurement of Secondary Electron Energy Spectra of Polymethyl Methacrylate
Ming Weng, Wan Liu, Ming Yin, Fang Wang, Meng Cao
Chin. Phys. Lett. 2018, 35 (4): 047901 .   DOI: 10.1088/0256-307X/35/4/047901
Abstract   PDF(pc) (591KB) ( 437 ) PDF(mobile)(590KB) ( 2 ) HTML ( 189
We report on a novel and convenient method of measuring secondary electron spectra for insulators in a secondary electron yield measurement system with a planar grid analyzer configuration and a metal mesh probe. In this measurement, the planar grid is negatively biased to force some emitted secondary electrons to return to the sample surface and to neutralize charges accumulated on the sample during the previous beam irradiation. The surface potential of the sample is then measured by use of a metal mesh probe. The grid bias for neutralization corresponding to the zero surface potential is determined based on the linear relationship between the surface potential and the grid bias. Once the surface potential equals zero, the secondary electron spectra of polymethyl methacrylate (PMMA) are studied experimentally by measuring the $S$-curve and then fitting it to Everhart's formula. The measurement results show that the peak energy and the full width at half maximum of the spectra are 4.26 eV and 14.06 eV, respectively.
Effects of Substrate Temperature on Properties of Transparent Conductive Ta-Doped TiO$_{2}$ Films Deposited by Radio-Frequency Magnetron Sputtering
Yang Liu, Qian Peng, Zhong-Pin Zhou, Guang Yang
Chin. Phys. Lett. 2018, 35 (4): 048101 .   DOI: 10.1088/0256-307X/35/4/048101
Abstract   PDF(pc) (1339KB) ( 336 ) PDF(mobile)(1329KB) ( 0 ) HTML ( 278
Ta-doped titanium dioxide films are deposited on fused quartz substrates using the rf magnetron sputtering technique at different substrate temperatures. After post-annealing at 550$^{\circ\!}$C in a vacuum, all the films are crystallized into the polycrystalline anatase TiO$_{2}$ structure. The effects of substrate temperature from room temperature up to 350$^{\circ\!}$C on the structure, morphology, and photoelectric properties of Ta-doped titanium dioxide films are analyzed. The average transmittance in the visible region (400–800 nm) of all films is more than 73%. The resistivity decreases firstly and then increases moderately with the increasing substrate temperature. The polycrystalline film deposited at 150$^{\circ\!}$C exhibits a lowest resistivity of $7.7\times10^{-4}$ $\Omega\cdot$cm with the highest carrier density of $1.1\times10^{21}$ cm$^{-3}$ and the Hall mobility of 7.4 cm$^{2}\cdot V^{-1}$ $s^{-1}$.
Current–Voltage Characteristics of the Aziridine-Based Nano-Molecular Wires: a Light-Driven Molecular Switch
Ayoub Kanaani, Mohammad Vakili, Davood Ajloo, Mehdi Nekoei
Chin. Phys. Lett. 2018, 35 (4): 048501 .   DOI: 10.1088/0256-307X/35/4/048501
Abstract   PDF(pc) (1131KB) ( 315 ) PDF(mobile)(1117KB) ( 8 ) HTML ( 321
Using nonequilibrium Green's function formalism combined first-principles density functional theory, we analyze the transport properties of a 4,4-dimethyl-6-(4-nitrophenyl)-2-phenyl-3,5-diaza-bicyclo[3.1.0]hex-2-ene molecular optical switch. The title molecule can convert between closed and open forms by visible or ultraviolet irradiation. The $I$–$V$ characteristics, differential conductance, on-off ratio, electronic transmission coefficients, spatial distribution of molecular projected self-consistent Hamiltonian orbitals, HOMO-LUMO gaps, effect of electrode materials $Y$(111) ($Y=$Au, Ag and Pt) on electronic transport and different molecular geometries corresponding to the closed and open forms through the molecular device are discussed in detail. Based on the results, as soon as possible the open form translates to the closed form, and there is a switch from the ON state to the OFF state (low resistance switches to high resistance). Theoretical results show that the donor/acceptor substituent plays an important role in the electronic transport of molecular devices. The switching performance can be improved to some extent through suitable donor and acceptor substituents.
Low-Frequency Noise in Amorphous Indium Zinc Oxide Thin Film Transistors with Aluminum Oxide Gate Insulator
Ya-Yi Chen, Yuan Liu, Zhao-Hui Wu, Li Wang, Bin Li, Yun-Fei En, Yi-Qiang Chen
Chin. Phys. Lett. 2018, 35 (4): 048502 .   DOI: 10.1088/0256-307X/35/4/048502
Abstract   PDF(pc) (781KB) ( 979 ) PDF(mobile)(775KB) ( 3 ) HTML ( 325
Low-frequency noise (LFN) in all operation regions of amorphous indium zinc oxide (a-IZO) thin film transistors (TFTs) with an aluminum oxide gate insulator is investigated. Based on the LFN measured results, we extract the distribution of localized states in the band gap and the spatial distribution of border traps in the gate dielectric, and study the dependence of measured noise on the characteristic temperature of localized states for a-IZO TFTs with Al$_2$O$_3$ gate dielectric. Further study on the LFN measured results shows that the gate voltage dependent noise data closely obey the mobility fluctuation model, and the average Hooge's parameter is about $1.18\times10^{-3}$. Considering the relationship between the free carrier number and the field effect mobility, we simulate the LFN using the $\Delta N$–$\Delta\mu$ model, and the total trap density near the IZO/oxide interface is about $1.23\times 10^{18}$ cm$^{-3}$eV$^{-1}$.
A Dynamic Model of Heavy Ion $^{7}$Li Irradiation Mutagenesis Based on Maize Inbred Line Nutrition Difference
Jin-Shan Hu, Jin-Peng Geng, Duo-Fang Li, Li Sui, Yong Zhan
Chin. Phys. Lett. 2018, 35 (4): 048701 .   DOI: 10.1088/0256-307X/35/4/048701
Abstract   PDF(pc) (1270KB) ( 488 ) PDF(mobile)(1262KB) ( 7 ) HTML ( 273
To reveal the saddle-type dose effect relationship, we propose a radiation mutagenesis model based on maize nutrition difference resulting from heavy ion $^{7}$Li radiation. Through irradiation mutagenesis, apparent trait selection, amino acids and fatty acids content determination, and modeling, dynamic evolution from microscopic damage and repair initiation to the final macroscopic biological effects are considered simultaneously. The results show that the steady state nature is independent of evolution time and only relates to different radiation doses. Heavy ion $^{7}$Li radiation could effectively cause maize phenotypic variation and could improve nutritional quality. This model not only gives a good fit to the experimental results on most types of amino acids and fatty acids, but also offers an adequate explanation of the experimental phenomenon underlying the saddle-type bimodal dose effect. By combining experimental results with theoretical analyses, we suggest that the synergy of the stimulus effect and momentum transfer is the main cause of the saddle-type dose effect bimodal curve. This provides an effective strategy for conducting maize germplasm innovation.
A High-Temperature $\beta$-Phase NaMnO$_{2}$ Stabilized by Cu Doping and Its Na Storage Properties
Li-Wei Jiang, Ya-Xiang Lu, Yue-Sheng Wang, Li-Lu Liu, Xing-Guo Qi, Cheng-Long Zhao, Li-Quan Chen, Yong-Sheng Hu
Chin. Phys. Lett. 2018, 35 (4): 048801 .   DOI: 10.1088/0256-307X/35/4/048801
Abstract   PDF(pc) (756KB) ( 451 ) PDF(mobile)(753KB) ( 12 ) HTML ( 862
The high-temperature $\beta$-phase NaMnO$_{2}$ is a promising material for Na-ion batteries (NIBs) due to its high capacity and abundant resources. However, the synthesis of phase-pure $\beta$-NaMnO$_{2}$ is burdensome and cost-ineffective because it needs to be sintered under oxygen atmosphere at high temperature and followed by a quenching procedure. Here we first report that the pure $\beta$ phase can be stabilized by Cu-doping and easily synthesized by replacing a proportion of Mn with Cu via a simplified process including sintering in air and cooling to room temperature naturally. Based on the first-principle calculations, the band gap decreases from 0.7 eV to 0.3 eV, which indicates that the electronic conductivity can be improved by Cu-doping. The designed $\beta$-NaCu$_{0.1}$Mn$_{0.9}$O$_{2}$ is applied as cathode in NIBs, exhibiting an energy density of 419 Wh/kg and better performance in terms of rate capability and cycling stability than those in the undoped case.
31 articles